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FINAL REPORT OF THE
COMMITTEE ON A STRATEGIC PLAN FOR U.S.
BURNING PLASMA RESEARCHADVANCE COPYNOT FOR PUBLIC RELEASE BEFORE

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Committee on a Strategic Plan for U.S. Burning Plasma Research
Board of Physics and Astronomy
Division on Engineering and Physical Sciences
A Consensus Study Report of

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Consensus Study Reports published by the National Academies of Sciences, Engineering, andMedicine document the evidence-based consensus on the study’s statement of task by anauthoring committee of experts. Reports typically include findings, conclusions, andrecommendations based on information gathered by the committee and the committee’s
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COMMITTEE ON A STRATEGIC PLAN FOR U.S. BURNING PLASMA RESEARCHMICHAEL MAUEL, Columbia University, Co-ChairMELVYN SHOCHET, NAS,1 University of Chicago, Co-Chair
CHRISTINA A. BACK, General Atomics
RICCARDO BETTI, University of Rochester
IAN CHAPMAN, UK Atomic Energy Authority
CARY FOREST, University of Wisconsin, Madison
T. KENNETH FOWLER, NAS, University of California, Berkeley
JEFFREY FREIDBERG, Massachusetts Institute of Technology
RONALD GILGENBACH, University of Michigan
WILLIAM HEIDBRINK, University of California, Irvine
MARK HERRMANN, Lawrence Livermore National Laboratory
FRANK JENKO, University of Texas at Austin & Max Planck Institute for Plasma Physics
STANLEY KAYE, Princeton University
MITSURU KIKUCHI, National Institutes for Quantum and Radiological Science and Technology
SUSANA REYES, Lawrence Berkeley National Laboratory
C. PAUL ROBINSON, NAE,2 Advanced Reactor Concepts, LLC
PHILIP SNYDER, General Atomics
AMY WENDT, University of Wisconsin, Madison
BRIAN WIRTH, University of Tennessee, Knoxville
Staff
JAMES C. LANCASTER, Director
GREG EYRING, Senior Program Officer, Study Director (from May to August 2018)
CHRISTOPHER J. JONES, Program Officer, Study Director (from August 2018)
NEERAJ P. GORKHALY, Associate Program Officer
LINDA WALKER, Program Coordinator
HENRY KO, Research Associate
BETH DOLAN, Financial Associate
DAVID LANG, Senior Program Officer, Study Director (until May 2018)
ANDREA PETERSON, Program Officer (until August 2017)

1
2

Member, National Academy of Sciences.
Member, National Academy of Engineering.

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BOARD ON PHYSICS AND ASTRONOMYBARBARA V. JACAK, NAS, Lawrence Berkeley National Laboratory, Chair
ABRAHAM LOEB, NAS, Harvard University, Vice Chair
FRANCIS J. DISALVO, NAS, Cornell University
TODD DITMIRE, University of Texas, Austin
NATHANIEL J. FISCH, Princeton University
DANIEL FISHER, NAS, Stanford University
WENDY FREEDMAN, NAS, University of Chicago
GERALD GABRIELSE, Harvard University
JACQUELINE N. HEWITT, Massachusetts Institute of Technology
WENDELL T. HILL III, University of Maryland
ALAN J. HURD, Los Alamos National Laboratory
BARBARA JONES, IBM Almaden Research Center
HERBERT LEVINE, Rice University
LYMAN A. PAGE, JR., NAS, Princeton University
STEVEN M. RITZ, University of California Santa Cruz
Staff
JAMES C. LANCASTER, Director
CHRISTOPHER J. JONES, Program Officer,
NEERAJ P. GORKHALY, Associate Program Officer
LINDA WALKER, Program Coordinator
HENRY KO, Research Associate
BETH DOLAN, Financial Associate
DAVID LANG, Senior Program Officer
ANDREA PETERSON, Program Officer (until August 2017)

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Preface
Following decades of scientific research, including the successful production of 11 MW fusion
power in the Tokamak Fusion Test Reactor experiment in the United States and 16 MW in the Joint
European Tokamak in the United Kingdom, an international agreement to build and operate a burning
plasma experiment was formalized in Paris with the signing of the Agreement on the Establishment of the
ITER International Fusion Energy Organization for the Joint Implementation of the ITER Project inNovember 2006. The signatories of the ITER agreement—the United States, China, the European Union,
India, Japan, the Republic of Korea, and the Russian Federation—are building the world’s largest
international scientific research facility, called ITER. When construction is complete, scientists will sharein the operation and results of ITER; create, study, and control burning plasma; and demonstrate fusion
power production at least 10 times greater than the power needed to sustain the plasma. This will be ascientific and technical achievement and a critical step toward producing and delivering electricity fromfusion energy.
Since the international establishment of the ITER project, an international design review wascompleted in 2008; ITER construction began in 2010; and ITER became the first-of-its-kind, licensed,
basic nuclear fusion facility in 2012. However, by 2013, ITER’s construction schedule had slipped, andITER’s costs had increased significantly, leading to questions of whether the United States should
continue its commitment to participate in ITER. These concerns resulted in a directive from Congress,
appearing in the Consolidated Appropriations Act, 2016, that the Secretary Energy report to Congress on
U.S. participation in the ITER project, including budget projections, project schedule, project
management, and foreign policy implementations.
The Secretary’s report was delivered to Congress in May 2016 and recommended that the UnitedStates remain a partner in the ITER project through fiscal year (FY) 2018. The report acknowledged thesignificant construction progress made at ITER and the substantial improvements in ITER project
management. The Secretary’s report also stated that ITER appears to be technically achievable and is thebest candidate today to demonstrate sustained burning plasma. Although fusion power holds thepossibility of providing abundant energy, the Secretary’s report noted that significant technical andmanagement risks remain before the project will be completed and recommended “the U.S. re-evaluate its
participation in the ITER project to assess if it remains in our best interests to continue our participation.”
In addition to outlining various oversight and management reviews to ensure continued improvement in
ITER project performance, the Secretary’s report requested advice from the National Academies of
Sciences, Engineering, and Medicine,1 as follows:
To perform a study of how to best advance the fusion energy sciences in the U.S., given the developmentsin the field since the last Academy studies in 2004, the specific international investments in fusion scienceand technology, and the priorities for the next ten years developed by the community and the Office of
Fusion Energy Sciences (FES) that were recently reported to Congress. This study will address the1

Effective July 1, 2015, the institution is called the National Academies of Sciences, Engineering, andMedicine. References in this report to the National Research Council are used in a historical context identifying
programs prior to July 1.

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scientific justification and needs for strengthening the foundations for realizing fusion energy given a
potential choice of U.S. participation or not in the ITER project, and will develop future scenarios in eithercase.

In response to this request, the Committee on a Strategic Plan for U.S. Burning Plasma Research
was established. The committee’s statement of task is given in Appendix A. The statement of task
requested the preparation of two reports.
The first, an interim report, was released on December 21, 2017, and is reprinted in Appendix I. It
presented the committee’s assessment of the current status of U.S. fusion research and of the importanceof burning plasma research to the development of fusion energy as well as to plasma science and otherscience and engineering disciplines.
For this report, the second and final report, the committee was asked to provide guidance on a
strategic plan for a national program of burning plasma science and technology research given the U.S.
strategic interest in realizing economical fusion energy in the long term. Strategic guidance was to beprovided in two separate scenarios in which the United States is, or is not, a member in ITER. The
committee was also asked to consider the health of the domestic fusion research sectors (universities,
national laboratories, and industry), participation by U.S. scientists in international activities, and whatrole international collaboration should play over the next 20 years.
This report represents the consensus of the committee after seven meetings (see Appendix B for
the meeting agendas). The first two meetings informed preparation of the interim report. The final fivemeetings were devoted to the scientific and technical bases for a variety of strategic elements underconsideration within the United States and to improve understanding the strategic plans for Europe,
China, Japan, and the Republic of Korea. The committee visited the two major fusion research facilities
within the United States; toured the superconducting magnet facility at Poway, California, where the large
ITER central solenoid magnets are being manufactured; and learned first-hand of the European fusionenergy strategy during a visit to the ITER construction site. Additionally, the committee heard about thefusion energy strategies of the two largest privately funded fusion ventures within the United States fromBob Mumgaard, chief executive officer of Commonwealth Fusion Systems (CFS) and Michl
Binderbauer, president and chief technology officer of TAE Technologies.
The committee is very grateful for the input from two weeklong community workshops on
Strategic Directions for U.S. Magnetic Fusion Research, hosted by the University of Wisconsin, Madison,in July 2017 and by the University of Texas, Austin, in December 2017. These workshops were highly
successful, involved hundreds of researchers across the country, and provided the committee with several
dozen technical documents on the scientific and engineering challenges and opportunities associated withadvancing magnetic confinement fusion as an energy source. The committee appreciates the tremendous
effort of the U.S. fusion energy research community in providing expert input. We are especially gratefulfor the leadership of the workshop co-chairs, David Maurer, Jon Menard, Hutch Neilson, and Mickey
Wade.
Several important findings became apparent during the committee’s deliberations, and they aredetailed in its two reports. First, the programmatic focus on preparing for ITER experiments has resulted
in tremendous progress in the understanding and prediction of a burning plasma. By way of wellinstrumented experiments, advanced theory, and state-of-the-art computer simulation, the international
community of fusion scientists is much more ready to carry out burning plasma experiments in ITER
today than when the Burning Plasma Assessment Committee released its report2 in 2004. Confidence that
ITER will achieve its scientific mission has improved. Second, the pace of advancing technology has
been rapid, and numerous technology breakthroughs, some of which developed independently fromfusion, appear to offer a viable pathway to lower the cost and shorten the time required to demonstratefusion power. These technologies were described in a report of the subcommittee of the U.S. Department
2

National Research Council, 2004, Burning Plasma: Bringing a Star to Earth, The National Academies Press,
Washington, D.C.

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of Energy’s (DOE’s) FESAC on Transformative Enabling Capabilities (TEC) Toward Fusion Energy,
released in February 2018. The FESAC report identified technologies, especially including high magnetic
field and critical temperature superconductors and advanced materials and manufacturing, with thepotential to transform fusion power systems to become more economically attractive forcommercialization. The application of these new technologies to fusion energy, when combined with thesignificant progress in understanding the complex processes within a magnetized burning plasma, are theunderpinnings for the committee’s strategic guidance for a cost-attractive pathway to fusion power.
During the committee’s study, we received encouragement and support from many individuals towhom we are indebted; these include Jim Van Dam of DOE’s Office of Fusion Energy Sciences; Nat
Fisch, member of the National Academies Board on Physics and Astronomy; Bill Dorland, chair of the
National Academies Plasma Science Committee; and James Lancaster, director of the Board on Physics
and Astronomy. The committee is also grateful to the following physicists and engineers who madeimportant technical contributions to the preparation of the interim and final reports: Mohamed Abdou,
Hans-Henrich Altfeld, Amitava Bhattacharjee, Bernard Bigot, Richard Buttery, Tony Donné, Gianfranco
Federici, Phil Ferguson, Stefan Gerhardt, Chuck Greenfield, Martin Greenwald, Sibylle Guenter, Richard
Hawryluk, Dave Hill, Amanda Hubbard, Yong-Seok Hwang, Thomas Klinger, Mike Jaworski, Sam
Lazerson, Gyung-Su Lee, Jiangang Li, Tim Luce, David Maurer, Jon Menard, Yuichi Ogawa, Stewart
Prager, Soren Prestemon, Juergen Rapp, Ned Sauthoff, Oliver Schmitz, Ed Synakowski, Tony Taylor,
Mickey Wade, Dennis Whyte, and Mike Zarnstorff.
On a more personal note, we would like to express our sincere appreciation to all members of thecommittee for their dedicated efforts for more than a year in the preparation of both reports. We areespecially grateful to Stanley Kaye, Philip Snyder, Brian Wirth, and Amy Wendt who took leadership inthe drafting of the chapters of the final report. We would also like to express our appreciation to the staffof the National Academies, particularly to David Lang and Christopher Jones, for their advice and highly
professional guidance in the final preparation of the interim and final reports. We are truly indebted tothem for their insights and extraordinary contributions throughout the committee’s study process.
Michael E. Mauel and Melvyn Shochet, Co-Chairs
Committee on a Strategic Plan for U.S. Burning Plasma
Research

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Acknowledgment of Reviewers
This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse
perspectives and technical expertise. The purpose of this independent review is to provide candid andcritical comments that will assist the National Academies of Sciences, Engineering, and Medicine in
making each published report as sound as possible and to ensure that it meets the institutional standards
for quality, objectivity, evidence, and responsiveness to the study charge. The review comments and draft
manuscript remain confidential to protect the integrity of the deliberative process.
We thank the following individuals for their review of this report:
Richard Buttery, General Atomics,
James D. Callen, NAE,1 University of Wisconsin, Madison,
Sibylle Guenter, Max Planck Institute of Plasma Physics,
Joseph Hezir, EOP Group, Inc.,
Robert Iotti, ARC Nuclear,
Steven E. Koonin, NAS,2 New York University,
Jonathan Menard, Princeton University,
David Petti, Idaho National Laboratory,
Anne White, Massachusetts Institute of Technology, andSteven J. Zinkle, NAE, University of Tennessee, Knoxville.
Although the reviewers listed above provided many constructive comments and suggestions, they
were not asked to endorse the conclusions or recommendations of this report nor did they see the final
draft before its release. The review of this report was overseen by Martha P. Haynes, NAS, Cornell
University. They were responsible for making certain that an independent examination of this report was
carried out in accordance with the standards of the National Academies and that all review comments
were carefully considered. Responsibility for the final content rests entirely with the authoring committee
and the National Academies.

1
2

Member, National Academy of Engineering.
Member, National Academy of Sciences.

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Contents
EXECUTIVE SUMMARY

ES-1

1

INTRODUCTION
Background
Committee Approach
Community and Expert Input
Assessments from the Interim Report
Structure of the Final Report
Notes

1-1

2

PROGRESS IN BURNING PLASMA SCIENCE AND TECHNOLOGY
Research Progress in Support of ITER
Plasma Confinement Predictions
Plasma Stability and Operational Boundaries
Energetic Particle Physics
Mitigation of Transients and Abnormal Events
Fusion Technology and Engineering Science
Research Progress Beyond ITER Toward Fusion Electricity
Plasma Exhaust Physics
Driving Plasma Current
Integrated Burning Plasma Configurations
Three-Dimensional Magnetic Fields and Stellarators
Theory and Simulation at the Exascale
Transformative Enabling Technologies
Advanced Algorithms
High Temperature Superconductors
Advanced Materials and Manufacturing
Fusion Blanket Research and Tritium Fuel Cycle
Fusion Safety
Integrated Systems Engineering for Fusion
Summary
Notes

2-1

3

EXTENDING THE FRONTIER OF BURNING PLASMA RESEARCH
The Importance of Burning Plasma Research
Understanding and Controlling a Burning Plasma
Advancing Fusion Technology and Engineering Science
The Importance of ITER to the U.S. to the Fusion Research Program
United States Partnership in ITER Construction
U.S. Research in Support of ITER Burning Plasma Science
U.S. Contributions to Fusion Technology
Preparing for ITER’s Scientific Mission

3-1

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Extending ITER Performance
Understanding Plasma Confinement at the Scale of a Power Plant
Exploring and Controlling a Burning Plasma
Developing an Alternate Approach without ITER Participation
Summary
Notes
4

ADVANCING MAGNETIC FUSION TOWARD AN ECONOMICAL ENERGY SOURCE
Previously Studied Pathways to Commercial Fusion Energy
A Compact and Lower-Cost Pathway to Fusion Electricity
High-Magnetic Field Strength for Compact Fusion
Plasma Power Handing for Compact Fusion
Achieving Steady Uninterrupted Operation for Compact Fusion
The Technology Pathway to Economical Fusion Power
High-Critical-Temperature Superconducting Magnets
Advanced Materials and Manufacturing Methods
Enabling Technologies for Heating, Measurement, Plasma Control, and Safe MaintenanceBlanket and Tritium Fuel Cycle Research
Pre-Pilot-Plant Research Program for the Compact Fusion Pathway
Systems-Engineering for a Compact Fusion Pilot Plant
Advanced Materials Modeling for Fusion Technology
Large-Bore, High-Field HTS Magnets for Fusion
Developing Long-Lifetime Materials for Fusion
Advancing Tritium Science and Blanket Technologies
Fusion Neutron Irradiation Facility
Sustaining High-Power Density Fusion Plasmas with Optimized Plasma Exhaust
Theory and Simulation
Stellarator Contributions to Compact Fusion Energy
Fusion Enabling Technologies for Plasma Heating, Current Drive, Measurement
and Control and Safe Maintenance of Core Components
Summary
Notes

4-1

5

STRATEGIC GUIDANCE FOR A NATIONAL PROGRAM FOR BURNING
PLASMA SCIENCE AND TECHNOLOGY
ITER: Extending the Frontiers of Burning Plasma Science
Beyond ITER: Setting the Nation’s Fusion Energy Goal
Toward Fusion Electricity: The Compact Fusion Pilot Plant
2020-2035: Removing the Barriers to Low-Cost Fusion Development
Extending the Frontier of Burning Plasma Science
Sustaining High Fusion Power Density with High Plasma Confinement
Power Exhaust Solutions for High-Power Density Fusion Systems
Large-Bore High-Temperature Superconducting Coils
Materials that Deliver High Performance and Long Lifetime
Blanket Systems that Breed Tritium and Extract High Quality Heat
Effective Leadership and Participation in the ITER Research Program
Maintaining Readiness to Move to Next Steps After ITER
Fusion Science Predictive Modeling and Exascale Computing
Promoting Discovery in Fusion Energy Science and Technology
Responding to a United States Decision to Withdraw from the ITER Project
Sustaining the National Program

5-1

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Budget Implications
Notes
6

COMMENTS ON ORGANIZATIONAL STRUCTURE AND PROGRAM BALANCE
Organizational Structure and Program Management
Expanding the OFES Organization to Meet Program Needs
Adopting a Long-term Strategy Toward a Fusion Energy Goal
Strengthening Community Organization and Input
Further Strengthening of United States Fusion Research
Setting Safety and Licensing Standards for Fusion Energy Research Facilities
Health of the U.S. Fusion Program
International Partnerships
Private Sector
Relationship Between Private Sector and National Goals
Linkages to Other Science and Technology Disciplines
Public Outreach
Summary
Notes

6-1

APPENDIXES
A
B
C
D
E
F
G
H
I
J
K

Statement of Task
Agendas for Committee Meetings and Site Visits
Strategic Planning for U.S. Burning Plasma Research from 2000 to 2018
Bibliography of Previous Studies Consulted by the Committee
Published Technical References Consulted by the Committee
Summary of Input Received from the Fusion Community
Major Research Facilities of the United States and Other Nations
Schedule and Budget Implications
Reprinted Interim Report
Biographies of Committee Members
Glossary and Acronyms

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A-1
B-1
C-1
D-1
E-1
F-1
G-1
H-1
I-1
J-1
K-1

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Executive Summary
Fusion energy offers the prospect of virtually unlimited energy, and the United States and manynations around the world have made enormous progress toward achieving fusion energy. Many of thecomplex physical processes of magnetically confined plasma are now understood, and the first
construction phase of the international ITER fusion reactor is more than half complete. With the initial
operation of ITER scheduled to begin within a decade and with the expectation, 10 years later, that
controlled fusion will be demonstrated, now is the right time for the United States to develop plans tobenefit from its investment in burning plasma research and take steps towards the development of fusion
electricity for the nation’s future energy needs.
This report of the Committee on a Strategic Plan for U.S. Burning Plasma Research describes a
strategic plan for fusion research to guide implementation of the committee’s two main recommendations:First, the United States should remain an ITER partner as the most cost-effective way to gain
experience with a burning plasma at the scale of a power plant.
Second, the United States should start a national program of accompanying research andtechnology leading to the construction of a compact pilot plant that produces electricity fromfusion at the lowest possible capital cost.

ITER is a burning plasma experiment and the critical next step in the development of fusionenergy. It is a large and ambitious project that integrates multiple advanced technologies and combines
the scientific and engineering expertise, industrial capacity, and financial resources of many nations. As apartner, the United States receives full benefit from the technology developed for ITER while providing
only a fraction of the financial resources. Methods to control the plasma and extract the electricityproducing heat will be tested and developed. U.S. industry is building major systems for ITER and
thereby gaining expertise in fusion engineering science and building industrial capabilities.
Although the United States provides only part of the cost of ITER, if the United States is to profit
from its share of the ITER investment, the nation’s strategic plan for fusion should combine its ITER
experience with the additional science and engineering research needed to realize reliable and economicalfusion electricity. Without this additional research, the United States risks being overtaken as othernations advance the science and technology required to deliver a new and important source of energy.
Recent advances motivate a new national research program leading to the construction of acompact fusion pilot plant. Significant progress in predicting and creating the high-pressure plasma
required for such a reactor has been made. Opportunities to develop technologies for fusion, such as hightemperature superconducting magnets and advanced materials, now make a compact device possible. A
focus on a compact device will accelerate the fusion development path, making it affordable andattractive for industrial participation. Finally, by starting now, a national research program toward acompact pilot plant and critical science and technology research can be ready in time to use theknowledge learned from ITER operation to demonstrate electricity production by mid-century.
The committee envisions a U.S. pilot plant producing power similar to that expected in ITER but
in a device much smaller in size and cost and employing design improvements that would allow net
electricity production. This compact burning plasma fusion pilot plant would be a pre-commercial
research facility. In addition to the production of fusion electricity, it would ultimately be capable ofuninterrupted operation for weeks and produce tritium, the heavy isotope of hydrogen in fusion fuel. As apilot plant, its purpose will be learning, but the knowledge obtained would be sufficient to design the firstcommercial fusion power systems.
A new national focus on developing a compact pilot plant in the long term will help set priorities
for the near and mid-term fusion program. Research needs to show how to increase the fusion power
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ES-1

density beyond that obtainable in ITER. Uninterrupted operation should be demonstrated while
researchers learn how to handle reliably the high levels of escaping heat from the plasma. New program
elements should begin immediately to develop the materials and technologies needed to extract the heatand recirculate tritium and, also, to promote the industrial development of very-high-field
superconducting magnets for fusion. Finally, technology innovations should be encouraged anddeveloped to simplify maintenance and lower construction cost.
The committee recognizes that there are risks involved in developing a compact fusion pilot
plant. Resolving these risks will necessitate the design and operation of new facilities. One of the greatest
risks is the control of a continuous high-pressure compact plasma, which will require a design andconstruction of new intermediate-scale research facility in the United States, or a significant upgrade to an
existing facility, to establish its feasibility. Another significant risk is the qualification of the materials
and components that surround the plasma and are exposed to fusion irradiation. The committee’s
proposed strategic plan also includes other recommendations aimed at improving and reducing the cost of
fusion as a source of electricity through the development of promising innovations in burning plasma
science and fusion engineering science.
The committee expects that the implementation of its recommendations, including both continued
participation in ITER and the start of a national research program for a compact pilot plant, will require
additional funding, rising to nearly $200 million beyond the recently enacted annual funding levels. This
funding would need be sustained for several decades. Although the funding remains level, the research
portfolio evolves over time, and existing research facilities are phased out as new ones are implemented.
The committee was also tasked to recommend strategic guidance if the United States decides towithdraw from the ITER project. This withdrawal would significantly disrupt the national research effort,
isolate U.S. researchers from the international effort, and eliminate the benefit of sharing the cost of
producing a burning plasma at the power plant scale. Nevertheless, if the United States decides towithdraw from the ITER project, the committee recommends the United States continue research toward
the construction of a compact fusion pilot plant. However, without ITER participation, U.S. progress will
necessitate a significantly larger commitment of resources for a longer time. Without ITER, the UnitedStates would need to design, license, and construct an alternative means to gain experience creating andcontrolling an energy-producing burning plasma. The scale of research facilities within the United States
would become larger, more ambitious, and more expensive. As a result, producing net electricity fromfusion in the United States would be delayed.

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ES-2

1Introduction
Fusion energy offers the prospect of abundant, virtually unlimited energy, and the United Statesand many nations around the world have made enormous progress toward achieving fusion energy. Manyof the complex physical processes of magnetically confined plasma are now understood, and the firstphase of ITER construction is more than half complete. With the initial operation of ITER scheduled to
begin within a decade and with the expectation, 10 years later, that controlled fusion will bedemonstrated, now is the right time for the United States to develop plans to benefit from its investment
in burning plasma research and take steps towards develop fusion electricity for the nation’s future energy
needs.
This report of the Committee on a Strategic Plan for U.S. Burning Plasma Research presents
guidance on a strategic plan for a U.S. research program of burning plasma science and technology
directed toward realizing economical fusion energy. It builds on the committee’s interim report,1 which
provided assessments of the importance of burning plasma research to the development of fusion energy
and of the current status of burning plasma research in the United States. Although significant scientificand engineering challenges are described, the committee concluded that the knowledge developed
through decades of fusion research is now sufficiently advanced to propose a path to demonstrate fusion
generated electricity within the next several decades. This strategy requires continued partnership in theinternational effort and strengthened research within the United States. Many technical details of the
proposed strategy need further development and input from the U.S. fusion energy science community.
Nevertheless, based on the advanced state of understanding the science of magnetic confinement, newdevelopments in superconducting magnets and advanced manufacturing methods, the considerable expert
input received, and the committee’s expertise, the committee concludes a research pathway that includes
study of a burning plasma and leads to the construction of a compact fusion pilot plant at the lowest
possible capital cost is technically sound and strategically warranted. This strategic guidance can be
developed for two scenarios: if the United States continues as a partner in the ITER project, or if it doesnot. However, if the United States decides to withdraw from the ITER project, the United States would
need to design, license, and construct an alternative means to gain experience creating and controlling anenergy-producing burning plasma. Without ITER participation, the scale of research facilities within the
United States would become larger, and the achievement of electricity production from fusion in the
United States would be delayed.
The following introduction is organized into four sections: (1) a brief background, (2) a summaryof the committee’s approach to its task, (3) a summary of the committee’s assessments within the interim
report, and (4) an outline and guide to the overall structure of this final report, including the committee’sfindings and recommendations.
BACKGROUND
Fusion is the process that powers the sun and thereby enables life on Earth to exist. It occurs
when hydrogen-like particles at extremely high temperature fuse to make a heavier element, like helium.
In this process energy is released, eventually appearing as heat. Fusion electrical power plants would
produce no carbon-based pollutants, have minimal long-lived radioactive waste, and benefit from analmost limitless fuel supply. The most successful concept and the subject of this report is a fusion power
plant consisting of a steadily burning plasma confined by a very strong magnetic force field within adonut-shaped vessel. In order for more power to be released by fusion reactions than needed to maintainthe temperature of the burning plasma, above 100 million degrees Kelvin, the burning plasma must have
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sufficiently large size and strong magnetic field so that the energy released by fusion reactions provides
most of the power needed to keep the plasma hot. Although significant fusion power has been generated
for short periods in the laboratory, a burning plasma, which is heated predominately by fusion reactions,has never been created. This requires construction of a burning plasma experiment such as theInternational Thermonuclear Experimental Reactor (ITER). While ITER is a science and technology
experiment, a future fusion power system will be built with additional advanced technologies that willallow uninterrupted operation, guide escaping plasma heat from the burning plasma out of the vessel in acontrolled way, produce the fusion fuel in blankets that surround the burning plasma, and convert theradiating energy from fusion to electricity in the same way as in existing power plants.
The United States became an ITER partner in 2007 after signing a binding international
agreement2 with China, the European Union (EU), India, Japan, the Republic of Korea (ROK) and Russia
to build and operate a burning plasma experiment at the scale of a power plant. ITER is a large andambitious project that integrates multiple advanced technologies and combines the scientific andengineering expertise, industrial capacity, and financial resources of several nations. As a burning plasma
experiment, ITER is a critical step along the path to advance the science and technology of a fusion powersource. The first phase of ITER construction is now more than half complete. The ITER Organization(IO) plans for initial operation of the facility by the end of 2025.
The decision to construct ITER was a milestone in fusion energy research. Fusion scientists had
successfully built, operated, and studied a series of experiments with strong magnetic fields andincreasing size. Using these experiments, they learned how to confine and control high-pressure plasma attemperatures exceeding 100 million degrees. In the largest experiments,3,4 significant fusion power was
produced for seconds, and some of the processes expected in a burning plasma were studied at thetemperatures and pressures required for fusion energy. In 2004, the NAS Burning Plasma Assessment
Committee5 concluded that the global fusion community was technically and scientifically ready toundertake a burning plasma experiment like ITER. Since that report, research has further increased
confidence that ITER will achieve its scientific mission and allow scientific studies of burning plasma at
the power plant scale.6
When fully completed, ITER will be capable of producing energy comparable to the output of apower plant and will allow study of many of the interconnected science and technology issues needed todevelop magnetic fusion energy as a practical source of power. Scientists will use ITER to test methods tocontrol plasma stability, plasma interactions with first wall materials, plasma confinement, and fusion
power output. Theoretical predictions of energetic particles produced by fusion reactions and methods tosustain a burning plasma for pulses longer than five minutes will be explored and validated. Equallyimportant are gains in fusion engineering science and industrial capability that are resulting fromassembly and operation of large superconducting magnets, safe management and recovery of tritium,
remote handling of in-vessel components, progress in evaluating fusion blanket options, and experience
with large-scale project management.
While experiments with ITER will lead to major gains along the path to fusion energy, additional
science and engineering challenges need to be addressed before fusion power can be produced in a
reliable, economical, and socially acceptable way. In a commercial system, the fusion power density
would need to increase and uninterrupted operation should be available for more than a year. Energetic
neutrons impinging on the surrounding wall and the escaping heat from the plasma need to be handled
reliably. The lithium-containing blankets that surround the plasma need to produce safely unprecedented
quantities of tritium, the heavy isotope of hydrogen. Technology innovations should be encouraged anddeveloped to simplify maintenance and lower construction cost. Any strategic plan for fusion power
requires both study of a burning plasma experiment and research beyond what will be done in a burning
plasma experiment to improve and fully enable commercial fusion power.
National strategic plans leading to the demonstration of fusion power have been adopted by ourinternational partners. Similar strategies have been discussed within the United States in the past.
However, for more than a decade, the United States has not had a long-term strategic plan for fusionenergy. This Final Report provides guidance for such a plan for the United States.
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The U.S. DOE/FES presented its current vision for fusion research to Congress in 2015.7 The
overall mission is to “expand the fundamental understanding of matter at very high temperatures anddensities and build the scientific foundation needed to develop a fusion energy source.” United States
fusion research emphasizes two frontiers in burning plasma science: “the physics of self-heated burning
plasma state” using ITER as the vehicle for gaining access to this state, and the “great scientific challenge
for fusion is to develop materials that can tolerate the extreme conditions created by burning plasma in afusion reactor.” The majority of the U.S. DOE/FES program budget contributes to developing thepredictive understanding needed for ITER operations and providing solutions to high‐priority ITER
research needs. A smaller element, called “Discovery Plasma Science,” represents about 15% of theannual fusion budget and supports research that advances fundamental understanding of ionized matter, or
plasma, in support of non-fusion applications. Nevertheless, these fundamental plasma studies inform
both non-fusion and fusion applications. As applied to fusion energy science, they develop and test
underlying concepts that underpin fusion plasma theory and simulation efforts and assist in thedevelopment of validated simulation capabilities to predict fusion plasma performance and behavior. The
U.S. DOE Office of Science has not presented a plan for research and technology programs needed toprogress beyond ITER to a source of fusion power.
The United States research focus on ITER has resulted in significant burning plasma researchadvances and improved confidence in ITER burning plasma performance. Examples of new progressinclude improved understanding and modeling of plasma confinement, demonstration of long-pulse
magnetic confinement, achievement of high plasma pressure comparable to values expected in ITER,
improved understanding of plasma exhaust processes, and successful demonstration of several techniques
to control transients. However, other fusion energy science and technology efforts within the UnitedStates that did not directly support ITER have been reduced or eliminated. Fusion technology efforts werereduced and domestic experimental facilities were closed limiting scientific and engineering opportunities
within the United States and weakening the potential to build expertise in fusion science and technology
and guide needed research alongside ITER.
The absence of a long-term research strategy for the United States is particularly evident whencompared to the plans of our international partners. The NRC Committee to Review the DOE Plan for
U.S. Fusion Community Participation in the ITER Program8 observed “international partners in ITER are
explicitly organized toward developing fusion energy and a Demonstration Power Plant (DEMO). Thisfocus gives them a clear goal for their development of fusion power.” The 2008 NRC report further
recommended that “existing gaps in planning for a demonstration power plant” should be addressed infurther development of U.S. DOE planning. EUROfusion (the consortium agreement of researchorganizations and universities from 26 European Union countries plus Switzerland, Ukraine, and formerly
the European Fusion Development Agreement) is guided by a roadmap to supply fusion electricity to thegrid by the 2050s.9 Similar national roadmaps leading to the demonstration of fusion power guideresearch in China10 and Japan.11 The committee’s Interim Report also noted the importance of strategicplanning to guide national research and innovation programs, to engage industrial partners, and to set
national priorities and concluded, “if the United States seeks to continue its pursuit for abundant fusion
power, the development of a national strategic plan for fusion energy that spans several decades isnecessary.”
Since joining the ITER project, the U.S. fusion community and its advisory committee, theFusion Energy Sciences Advisory Committee (FESAC),12 have responded to requests from the U.S. DOE
Office of Science to identify the issues arising in a path to fusion demonstration, with ITER as a central
part of that effort, and to prioritize the additional interconnected scientific and technical questions to beanswered. Appendix C presents a summary of these strategic planning activities conducted from 2001 to
2018. Fourteen FESAC reports and four community workshops, sponsored by the U.S. DOE Office of
Science are summarized. These reports recommended programs of research to address all of the scientificchallenges of fusion energy including fusion engineering, materials science, and plasma physics.
One difficulty for recent U.S. fusion energy strategic planning has been the substantial growth in
ITER construction costs and schedule slippage. In response to cost and schedule concerns, the ITERPREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION
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Council charged an independent team, chaired by William Madia, former director of Oak Ridge National
Laboratory and Stanford University vice president for the Stanford Linear Accelerator Center, todetermine the causes for ITER’s cost increases and schedule delays and to make management
recommendations. These recommendations resulted in significant management improvements by the
ITER Council and the appointment of Bernard Bigot as the new ITER director in March 2015. The ITER
Council approved a new Updated Long-Term Schedule to first plasma in June 2016, and the U.S. DOE
was able to approve the project execution plan for U.S. contributions to ITER in January 2017.13 A
measure of the success of ITER’s management reforms is the fact that two years after the creation of the
updated long-term schedule, the project remains on schedule for first plasma in 2025 and, since January
2016, has achieved all 33 scheduled project milestones.14
The preceding paragraphs and the additional background within Appendix C present the context
for the committee’s study and its strategic guidance for burning plasma science and technology directed
toward realizing fusion energy. On the one hand, the U.S. fusion energy science program has madeleading advances in burning plasma science that have substantially improved our confidence in the
success of ITER and our ability to learn a great deal from its operation. On the other hand, theinterconnected science and technology needed for fusion are not fully developed. Many challenging
questions still need to be answered through scientific discovery and dedicated interdisciplinary study inplasma physics, materials science, fusion nuclear technology, and engineering science. New researchfacilities and initiatives need to be designed and constructed to carry out the additional research needed torealize fusion electricity. Long-term goals should be set so that priority choices can be made. The U.S.
research portfolio will need to evolve in time as existing research facilities are phased out as new ones are
implemented.
To be compelling, a new strategy should incorporate technical innovations and insights thatenable a lower cost development path than was proposed in past strategic plans. Also, a compelling planshould take into consideration ITER’s updated management and schedule, and allow cost-effective studyof both a burning plasma experiment and the research and technology programs needed beyond what isdone in a burning plasma experiment. After adopting a nationally endorsed strategic plan for delivery offusion energy, the United States can better set research priorities, promote innovation in fusion scienceand technology targeted to improve the fusion power system as a commercial energy source, and attract
the talented scientists and engineers who will drive research toward commercially viable fusion reactor
designs. Describing the elements of this compelling plan is the purpose of this final report.
COMMITTEE APPROACH
In the course of developing its strategic guidance, the committee considered past strategic plans
proposed for the United States, the strategic plans of other nations, recent developments, and the input
from community experts. The committee first worked to understand whether the science and technology
of magnetic fusion has advanced sufficiently to justify adopting a national plan toward realizing fusion
power for the United States and how a national strategic plan developed today is different from past
strategic plans. This required understanding the progress and challenges for magnetic fusion energy, thestatus and schedule of the ITER project, the potential contributions from other international research
activities, and the opportunities for progress within the Unites States. The committee then set out todefine the steps required to realize economical fusion energy for the United States in the long term.
As required by the committee’s Statement of Task (Appendix A), the focus of this Final Report isthe advancement of magnetic confinement fusion energy given the U.S. strategic interest in realizing
economical fusion energy in the long-term. As a consequence, the committee did not comment onquestions of program balance within the U.S. DOE Office of Science between non-fusion plasma scienceand research in support of magnetic fusion energy. As this Final Report is being written, the committee
notes the start of a new Decadal Assessment of Plasma Science by the National Academies15 that will

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provide valuable information and guidance on issues that pertain to plasma science to the federal agencies
and policy makers in both Congress and the Administration.
The past strategic plans16 proposed for the United States development of fusion energy consistedof four elements: (1) magnetic confinement systems, (2) understanding and controlling a burning plasma,(3) developing materials systems that can withstand the energetic fusion neutrons and the escaping plasma
heat impinging on the inner wall, and (4) fusion nuclear technology consisting of a fusion “blanket” thatboth converts the energy released from fusion reactions to electricity and also creates from lithium theheavy isotope of hydrogen, tritium, which should be safely recovered and used as fusion fuel. Figure 1.1
illustrates one strategic pathway as presented in the 2004 NRC Report of the Burning Plasma Assessment
Committee.17 Research from all four elements need to be completed to inform a future “decision point”
leading to the demonstration of fusion power and construction of a DEMO facility. A DEMO would
produce electricity, operate routinely and eliminate all technical barriers to the commercialization offusion power. Prior to a DEMO decision, both non-nuclear and nuclear fusion research occurs. Nonnuclear research in magnetic confinement systems aims to understand and predict how plasma pressure
can be confined by configuring the magnetic pressure imposed from strong superconducting magnets.
Non-nuclear technology research includes enabling systems that heat and control a burning plasma, theengineering sciences for strong superconducting magnets, and the techniques to handle the escaping heatfrom the plasma.
The remaining activities in Figure 1.1 are fusion nuclear facilities: a burning plasma experiment,
like ITER, a source of 14-MeV neutrons that would advance scientific understanding of radiation effects
phenomena in the materials that will surround a fusion plasma, and a fusion component test facility thatwill test and develop the lithium-containing fusion “blankets” necessary to create the fusion fuel, tritium,and convert energetic neutron energy into useful heat. Because they are fusion nuclear facilities, they
operate with nuclear operating licenses, like the first-of-a-kind basic nuclear fusion license given to ITER
by French Order of 7 February 2012.18
All strategic plans for fusion energy contain the elements depicted in Figure 1.1. But, today, thesequence of activities can be quite different from Figure 1.1 for several reasons. First, the international
fusion research community is now much stronger, having made good progress toward fusion. Ourinternational partners have demonstrated world-record achievements in long-pulse plasma confinement
and have successfully constructed and operated leading research facilities with superconducting magnets.
These experiments have provided increased confidence in the prospect for sustained, uninterrupted fusion
power. Second, while past plans required the design, siting, and construction of a burning plasma
experiment, today’s planning can build upon the continued progress of the ITER project and thesignificant investment of the international community already underway. With the schedule of the ITER
Project newly baselined and on-track, strategic plans can expect burning plasma studies using ITER will
inform the next steps in the development of fusion energy. Third, fusion strategic planning is also
different today because of advances in the theoretical understanding of toroidal magnetic confinement andplasma control that provide integrated solutions to optimize the burning plasma regime. Finally,
remarkable new technologies, largely developed outside the fusion research effort, promise to reduce thesize and cost of future facilities that will demonstrate the production of fusion electricity. Unlike thepathway shown in Figure 1.1, a large DEMO device no longer appears to be the best long-term goal for
the United States program. Instead, science and technology innovations and the growing interest andpotential for private-sector ventures to advance fusion energy concepts and technologies suggest that
smaller, more compact facilities would better attract industrial participation, shorten the time and lower
the cost of the development path to commercial fusion energy.

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Permission Pending

FIGURE 1.1 Development path for realizing fusion power as a practical energy source, developed by
the Snowmass 2002 Fusion Summer Study Workshop. Basic research in plasma physics andtechnologies support major fusion faculties leading to decision point for a DEMO device. SOURCE:
National Research Council. 2004. Burning Plasma: Bringing a Star to Earth. Washington, DC: The
National Academies Press. https://doi.org/10.17226/10816, p. 152.

The committee reviewed past strategic plans, the advancement in magnetic fusion confinement
science, and the recent breakthroughs in fusion-relevant technologies with the goal to develop a newlower-cost roadmap for the United States. The committee asked several questions:






Has the science and technology of magnetic fusion advanced sufficiently to justify adopting anational plan toward realizing economical fusion power for the United States?
With the expected start of ITER experiments within the next decade, will U.S. researchers beready to benefit from burning plasma experiments and begin the next steps, beyond ITER,
toward the demonstration of fusion electricity?
How can the U.S. program develop a unique research strategy that benefits from the large
international effort and avoids the cost of duplicated effort?
Can advances in modeling, prediction, and simulation be used to make wise facility
investments and improve overall research effectiveness?
Finally, can new technologies, like high magnetic field and high critical temperature
superconductors, and new material designs and advanced fabrication, like additive
manufacturing, lower the cost of fusion development and provide an affordable plan thatbuilds upon the ITER research experience and is consistent with appropriate long-term
funding scenarios leading to fusion electricity?

The committee answered these questions through deliberation and through detailed considerationof technical input from the fusion research community.

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COMMUNITY AND EXPERT INPUT
In the course of developing its strategic guidance, the committee placed high value on communityand expert input and the considerable scientific progress reported in scientific and technical journals.19 In
addition to the review of past studies on magnetic fusion energy strategy and research needs, thecommittee heard from representatives from the European Union, China, Japan, and the Republic of Korea(ROK) who addressed the committee and described near-term and long-term research plans. The
committee conducted visits to the national fusion research facilities at General Atomics and the Princeton
Plasma Physics Laboratory and walked through the ITER construction site located besides the Cadarache
research center of the French Alternative Energies and Atomic Energy Commission (CEA). Over fifty
technical white papers were received; more than two dozen technical lectures were presented to thecommittee during seven open meetings (Appendix B); and references to more than 300 technical andscientific papers were cited to illustrate the progress in fusion energy science research.
The committee also benefited from two independent strategic planning activities (Appendix E).
The first was a series of community workshops, titled “U.S. Magnetic Fusion Research Strategic
Directions.”20 The goals of the workshops were to discuss, debate, and develop critical technicalinformation required for the development of a strategic plan, including program mission and goals, and topresent and discuss opportunities to achieve those goals through the pursuit of various scientific andtechnical programs. These workshops were highly successful and involved hundreds of researchers acrossthe country. Workshop participants prepared detailed technical reports on nine strategic research program
elements, descriptions of various strategic approaches to fusion research planning, and summaries ofimportant working group topics such as the impact of ITER access to U.S. fusion scientists and therequirements for attractive fusion power systems. The second activity supporting magnetic fusion
strategic planning was the work of the Subcommittee of the U.S. DOE FESAC on Transformative
Enabling Capabilities (TEC) Toward Fusion Energy. FESAC released the subcommittee’s report in
February 2018,21 which identified “the most promising transformative enabling capabilities (TEC) for the
U.S. to pursue that could promote efficient advance toward fusion energy, building on burning plasma
science and technology.” The report identified several technologies (advanced computer algorithms, highmagnetic field and high critical temperature superconductors, advanced materials and manufacturing,novel technologies for tritium fuel cycle control, and fast flowing liquid metals) each with “tremendous
opportunity to accelerate fusion science and technology toward power production” and with the potential
to transform fusion power systems to become more economically attractive for commercialization.
ASSESSMENTS FROM THE INTERIM REPORTThe Final Report builds on the committee’s seven assessments of the status and importance ofU.S. burning plasma research to the development of fusion power presented in the Interim-Report.22
These are:
Assessment 1: Burning plasma research is essential to the development of magnetic fusionenergy and contributes to advancement in plasma science, materials science, and the nation’s
industrial capacity to deliver high-technology components.
Assessment 2: The U.S. fusion energy science program has made leading advances in burning
plasma science that have substantially improved our confidence that a burning plasma experimentsuch as ITER will succeed in achieving its scientific mission.
Assessment 3: Construction and operation of a burning plasma experiment is a critical, but not
sufficient, next step toward the realization of commercial fusion energy. In addition to a burning

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plasma experiment, further research is needed to improve and fully enable the fusion powersystem.
Assessment 4: Although our international partners have national strategic plans leading to afusion energy demonstration device, the United States does not.
Assessment 5: Recent closures of domestic experimental facilities without new starts, as well asa reduction of fusion technology efforts, threaten the health of the field in the United States.
Assessment 6: Any strategy to develop magnetic fusion energy requires study of a burning
plasma. The only existing project to create a burning plasma at the scale of a power plant is ITER,
which is a major component of the U.S. fusion energy program. As an ITER partner, the UnitedStates benefits from the long-recognized value of international cooperation to combine thescientific and engineering expertise, industrial capacity, and financial resources necessary forsuch an inherently large project. A decision by the United States to withdraw from the ITER
project as the primary experimental burning plasma component within a balanced long-term
strategic plan for fusion energy could isolate U.S. fusion scientists from the international effort
and would require the United States to develop a new approach to study a burning plasma.
Assessment 7: If the United States wishes to maintain scientific and technical leadership in thisfield, the committee concludes that the United States needs to develop its own long-term strategicplan for fusion energy.
The first two assessments address the importance of burning plasma research to the developmentof fusion energy science and describe the achievements of the United States research program
contributing to increased confidence in burning plasma studies to be conducted with the ITER device. The
next three assessments describe programmatic shortfalls in the United States program that threaten thehealth of the field and hamper progress in necessary fusion technology research to improve and fully
enable fusion power. The last two assessments from the Interim Report deserve emphasis because they
directly relate to the committee’s strategic guidance.
As explained in Assessment 6, as an ITER partner the United States benefits from the longrecognized value of international cooperation to combine the scientific and engineering expertise,industrial capacity, and financial resources necessary to create and study burning plasma at the scale of apower plant, i.e. ITER. Because burning plasma research in support of ITER and in preparation for ITER
experiments is a primary focus of the international and U.S. research programs, ITER is more than aconstruction project. ITER plays a central role in today’s U.S. burning plasma research activities, andparticipation in the ITER project provides formal mechanisms for U.S. scientists to take leading roles in
the international effort to develop fusion energy. Additionally, because the vast majority (approximately
80 percent) of U.S. ITER construction funding remains within the U.S. supply chain, participation in
ITER has resulted in significant advances in U.S. domestic industrial capabilities and capacities thatwould not have happened without ITER participation.
A decision by the United States to withdraw from the ITER project as the primary experimental
burning plasma component within a balanced long-term strategic plan for fusion energy could isolate U.S.
fusion scientists from the international effort and would require the United States to develop a new
approach to study a burning plasma. The impact of a decision to withdraw from ITER would be
disruptive. Because there is currently no mature burning plasma experiment as an alternative to ITER, thedesign, construction, and licensing of such an alternative to ITER would require significant developmentby the U.S. program, as well as a new approach to avoid isolation from the international fusion energy
research effort.
The committee’s study in preparation for the Final Report has reinforced its conclusion that
continuation as a partner in the ITER project best serves the nation’s strategic plan for fusion energy. For
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this reason, the primary guidance within this Final Report assumes continued U.S. participation in ITER
and presents a strategy for the demonstration of fusion electricity that benefits from ITER operation andfrom new developments in technologies that will lower fusion’s development costs. The committee did
not find any reasonable or compelling strategy for fusion power development without ITER participation,and no such strategy was presented to the committee that could provide a technical basis forrecommended guidance. What the committee does provide, nevertheless, is a generic plan if the UnitedStates decides to withdraw from ITER having similar goals but requiring a larger commitment of
resources for longer periods of time.
As explained in Assessment 7, if the United States wishes to maintain scientific and technicalleadership in this field, the committee concludes that the United States needs to develop its own long-term
strategic plan for fusion energy. This assessment reinforces the recommendations of the NRC Committee
to Review the DOE Plan for U.S. Fusion Community Participation in the ITER Program and echoes therecommendations of Congressional leaders and the 2014 GAO Report.23 After adopting such a plan, theUnited States can better set research priorities and attract the talented scientists and engineers who will
drive research toward commercially viable fusion reactor designs. Indeed, now is the right time to expand
the U.S. effort beyond the study of a burning plasma and include the accompanying research to fully
enable fusion power. If the United States is to profit from its share of the ITER investment, a strategic
research plan directed toward realizing fusion energy in the long term is necessary.
As a result of research progress and the potential for new technologies to improve the economic
attractiveness of fusion power and lower the cost of fusion development, the committee’s guidance
presents a plan for the United States to benefit from its investment in burning plasma research and takesteps towards the development of fusion electricity for the nation’s future energy needs. Four elements
important to the committee’s guidance are:
Continued progress toward the construction and operation of a burning plasma experimentleading to the study of burning plasma,
Research beyond what is done in a burning plasma experiment to improve and fully enable
commercial fusion power,
Innovation in fusion science and technology targeted to improve the fusion power system as acommercial energy source, andA mission for fusion energy research that engages the participation of universities, national
laboratories, and industry in the realization of commercial fusion power for the nation.

Today, there is little doubt that fusion energy can be produced in the laboratory. The questions
now being asked are different than before and cannot be answered by science alone. Whether fusion canbe done in a reliable, economical, and socially acceptable way requires finding inventive solutions tochallenges that intersect science, technology, and engineering and combining the talents of plasma
scientists and skilled engineers. These remaining challenges are by no means trivial. Fusion research anddevelopment would need to be sustained for several more decades, and major new test facilities will need
to be carefully designed and constructed. Needless to say, fusion research, like any grand undertaking,will be most successful when guided by a national strategic plan that sets priorities, supports decisionmaking, and establishes a long-term goal by which to measure progress.
STRUCTURE OF THE FINAL REPORTThe following five chapters describes the committee’s guidance for a strategic plan leading to the
production of electricity from a compact fusion pilot plant:

Chapter 2 describes scientific and technical progress and how this progress has improved
confidence that a burning plasma experiment, like ITER, will succeed. Chapter 2 provides

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







three findings about this progress and further developments needed to progress beyond ITER
toward fusion electricity.
Chapter 3 describes the important burning plasma science to be learned from participation in
ITER and how the United States can benefit from ITER participation and inform the designof a compact pilot plant. Chapter 3 concludes with three findings describing the scientific andtechnical benefits from ITER, the importance of ITER in the U.S. program, and how
advancements in understanding magnetic confinement point to improvements beyond the
ITER baseline and with two recommendations for how the U.S. DOE FES should conductboth the near-term and long-term ITER research. Chapter 3 also includes two findings
describing research needs if the U.S. withdraws from the ITER project and states thecommittee’s recommendation that the United States should not withdraw. However, even in
the scenario without ITER participation, the U.S. DOE/FES should still initiate a plan leading
toward the construction of a compact fusion pilot plant. In the scenario without ITER, analternate means to study a burning plasma and to engage the international community would
be required.
Chapter 4 describes the interconnected science and technology research within the newnational program. It describes research building upon ITER results and reaching the lowest
possible capital cost for the compact pilot plant. Chapter 4 concludes with a detailed finding
itemizing the technical and scientific support motivating a new national research program
leading to the construction of a compact pilot plant. Chapter 4 also concludes with fourrecommendations to the U.S. Department of Energy in the start and planning of its new
program of accompanying research and technology leading to the compact pilot plant. These
include resolving five critical research needs, planning for the construction of new researchfacilities, and the adoption of a two-phase approach to its plans for the compact pilot plant sothat scientific and technical risks can be addressed cost-effectively.
Chapter 5 reviews the forgoing chapters and summarizes the committee’s strategic guidancefor U.S. burning plasma research. The committee’s two main recommendations areelaborated. This chapter summarizes program elements, an approximate research timeline, a
response to a decision to withdraw from ITER, and budget implications of the committee’s
guidance.
Chapter 6 discusses organizational structure, program management, and other management
goals to further strengthen United States fusion research with partnerships with related efforts
within the U.S. Department of Energy, with industry, and with the international researchcommunity. Chapter 6 concludes with five findings and seven recommendations aimed to
guide the implementation of an expanded U.S. DOE FES research program and strengthencommunity participation in the burning plasma science, materials science, fusion nuclear
sciences, and engineering sciences needed to realize an economical pathway to fusion
electricity for the nation.

The following chapters contain many technical details of the proposed strategy based on study
and deliberation. However, the committee expects its guidance will need further technical development
and further input from the U.S. fusion energy science community. Nevertheless, based on the advanced
state of understanding the science of magnetic confinement, new developments in superconducting
magnets and advanced manufacturing methods, the considerable expert input received by the committee,
and the committee’s expertise, the committee’s Final Report provides a technically sound pathway thatgains experience with a burning plasma at the scale of a power plant and that also starts a national plan for
the accompanying research and technology leading to the construction of a compact pilot plant at thelowest possible capital cost and the production of electricity from fusion.

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NOTES
1. National Academies of Sciences, Engineering, and Medicine. 2018. Interim Report of theCommittee on a Strategic Plan for U.S. Burning Plasma Research. Washington, DC: The National
Academies Press. https://doi.org/10.17226/24971 and also Appendix B.
2. Agreement on the Establishment of the ITER International Fusion Energy Organization for the
Joint Implementation of the ITER Project, IAEA, INFCIRC/702,
https://www.iaea.org/sites/default/files/publications/documents/infcircs/2007/infcirc702.pdf
3. Hawryluk, et al., “Results from deuterium-tritium tokamak confinement experiments,” Rev. Mod.
Phys. 70, 537 (1998).
4. Keilhacker et al, “High fusion performance from deuterium-tritium plasmas in JET,” Nuclear
Fusion 39, 209 (1999).
5. National Research Council. 2004. Burning Plasma: Bringing a Star to Earth. Washington, DC:
The National Academies Press. https://doi.org/10.17226/10816 .
6. See Assessment 2 of National Academies of Sciences, Engineering, and Medicine. 2018. Interim
Report of the Committee on a Strategic Plan for U.S. Burning Plasma Research. Washington, DC: The
National Academies Press. https://doi.org/10.17226/24971 and also Appendix F.
7. DOE, The Office of Science’s Fusion Energy Sciences Program: A Ten‐Year Perspective, Reportto Congress, Washington, D.C., December 2015.
8. (p. 16) National Research Council. 2009. A Review of the DOE Plan for U.S. Fusion Community
Participation in the ITER Program. Washington, DC: The National Academies Press.
https://doi.org/10.17226/12449.
9. European Fusion Development Agreement (EFDA), Fusion Electricity: A Roadmap to theRealization of Fusion Energy, November 2012, https://www.euro-fusion.org/wpcms/wpcontent/uploads/2013/01/JG12.356- web.pdf
10. Yuanxi Wan, et al, “Overview of the present progress and activities on the CFETR,” 2017 Nucl.
Fusion 57 102009.
11. Yamada et al., “Japanese endeavors to establish technological bases for DEMO,” Fusion Eng and
Design 109:1318-1325, 2016.
12. The Fusion Energy Sciences Advisory Committee (FESAC) is the chartered FACA committee toprovide independent advice to the Director of the Office of Science on complex scientific andtechnological issues that arise in the planning, implementation, and management of the fusion energy
sciences program. The FESAC Charter and membership is available athttps://science.energy.gov/fes/fesac/.
13. DOE, Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, Office of
Science, Fusion Energy Sciences, Washington, D.C., January 2017.
14. ITER Council Press Release (21 June 2018), available online:
https://www.iter.org/doc/www/content/com/Lists/list_items/Attachments/777/2018_06_IC-22.pdf
15. See current activities of the National Academies Board on Physics and Astronomy,
http://sites.nationalacademies.org/BPA/BPA_048421 .
16. S. O. Dean (2017) “Historical Perspective on the United States Fusion Program,” Fusion Scienceand Technology, 47:3, 291-299, DOI: 10.13182/FST05-A708
17. From p. 152, National Research Council. 2004. Burning Plasma: Bringing a Star to Earth.
Washington, DC: The National Academies Press. https://doi.org/10.17226/10816
18. Implementation at ITER of the French Order of 7 February 2012, concerning basic nuclear
installations within the European Domestic Agency, P. Wouters et al 2017 Nucl. Fusion 57 100401.
19. Appendices C, D, and E provide the agendas for committee meetings and site visits, bibliographyof past studies consulted, and summary of input received from the fusion research community.
20. See website for community workshops on U.S. Magnetic Fusion Research (MFR) Strategic

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Directions, https://sites.google.com/site/usmfrstrategicdirections/home
21. Transformative Enabling Capabilities for Efficient Advance Toward Fusion Energy, report of the
U.S. DOE FESAC, February 2018.
https://science.energy.gov/~/media/fes/fesac/pdf/2018/TEC_Report_1Feb20181.pdf
22. National Academies of Sciences, Engineering, and Medicine. 2018. Interim Report of theCommittee on a Strategic Plan for U.S. Burning Plasma Research. Washington, DC: The National
Academies Press. https://doi.org/10.17226/24971 and also Appendix F.
23. U.S. Government Accountability Office, Fusion Energy: Actions Needed to Finalize Cost and
Schedule Estimates for U.S. Contributions to an International Experimental Reactor, Report to Congress,
GAO-14-499, Washington, D.C., June 2014.

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2Progress in Burning Plasma Science and Technology
This chapter describes progress in burning plasma science since the United States joined the
ITER partnership by way of international agreement.1 Since then, experiments using research facilities in
the United States and in other nations have been highly productive. New ideas to control and sustain aburning plasma have been discovered, and theoretical and computational models developed in the UnitedStates have substantially improved the ability to control plasma stability, predict plasma confinement, andenhance fusion energy performance. Methods to control and mitigate transients and scenarios that will
guide operation of ITER have been successfully tested. Confidence that ITER will succeed in achieving
its scientific mission has substantially improved, and progress in burning plasma science and technology
has motivated research beyond what will be achieved in ITER toward fusion electricity.
The following first describes progress in burning plasma science and technology that has resulted
from the international effort to prepare for ITER operation. This progress combined with ITER
construction progress (Figure 2.1) demonstrates a high-level of readiness to undertake burning plasma
experiments and the expectation that the burning plasma regime can be accessed for detailed study. Next,
this chapter discusses the scientific and technical readiness to undertake research beyond ITER andaddress the potential for economical fusion electricity. Finally, this chapter concludes with a summary of
three findings about progress and the further developments needed to progress beyond ITER toward
fusion electricity.
RESEARCH PROGRESS IN SUPPORT OF ITER
The 2004 NAS Burning Plasma Assessment concluded that the global fusion science community
is both scientifically and technically ready for proceeding with a burning plasma experiment. Scientificreadiness was determined from empirical confinement predictions, knowledge of operational limits set byplasma stability, methods to mitigate abnormal events like plasma current disruptions, the ability tomaintain plasma purity, methods to measure and characterize a burning plasma, and techniques to control
a burning plasma. Technical readiness was determined by successful prototyping of ITER components,
evidence of adequate component lifetime in a nuclear environment, tests of plasma-facing components
and materials, initial analysis of the safe control of tritium, demonstrations of remote maintenancesystems, and demonstration of the required fueling, heating, and current drive control.
Since the 2004 assessment, the ITER design was reviewed and updated in 2008.2 The updated
ITER physics basis3 reflected progress from major experiments around the world. Scientists from theUnited States and from other nations significantly advanced the basic understanding of the processes
expected in burning plasma, tested scenarios that will be used to study burning plasma, and achieved
significant progress toward construction of the ITER facility through international cooperation.
Experiments conducted using research facilities in the United States have discovered new ideas to control
a burning plasma that can be tested in ITER. New experiments built with superconducting magnets in
China and the Republic of Korea have demonstrated long-pulse plasma with high confinement properties.
United States researchers have used NSTX to test innovative divertor configurations and understandplasma rotation and kinetic effects on the stabilization of instabilities. Using the DIII-D national researchfacility, fusion scientists have discovered and tested techniques to control edge localized modes, test
disruption mitigation schemes for use on ITER, and experimentally verified computational models to help
predict ITER operation. Record plasma pressure was achieved in the Alcator C-Mod experiment at MIT.
Experiments using Alcator C-Mod, and the JET and ASDEX-U devices in Europe demonstrated use of ametallic first-wall in preparation for similar experiments in ITER. Theoretical and computational models
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FIGURE 2.1 Arial photograph of the ITER site. Construction began in 2010 after site preparatory
work. By December 2017, more than half of ITER total construction work through first plasma wascomplete. On June 2018, ITER construction continues on track having achieved all 33 Councilapproved project milestones scheduled since January 2016.

developed in the United States have substantially improved the ability to control plasma stability, predict
plasma confinement, and enhance fusion energy performance.
The ITER Organization (IO) and a team of international scientists developed the ITER Research
Plan (IRP) in 2013.4 This plan was recently revised with the updated ITER schedule.5 The IRP presents a
program logic for a sequence of plasma operations with hydrogen, helium, deuterium, and ultimately
deuterium-tritium mixtures for fusion power production. Through dedicated experiments, research, andstudy by the international community, all of the science and technical criteria that established thereadiness for burning plasma experiments in 2004 have progressed greatly.
In the next sections, scientific readiness for ITER operation is presented, including these mainareas of research: (1) plasma confinement predictions, (2) plasma stability and operational boundaries, (3)energetic particle physics, (4) mitigations of transients and abnormal, events, and (5) technical progressfor ITER construction and technology.
Plasma Confinement Predictions
The understanding and optimization of plasma transport, and the ability to predict the plasma
response to both collisional and turbulence-induced transport, have advanced considerably beyond thestage when only empirical scaling-laws were employed to predict the performance of ITER. Physics
based optimization of confinement performance in both the core and edge of magnetically confinedplasmas is one of the critical areas in present day burning plasma research.
A strength of the U.S. theory and simulation program is its close connection to experimental
studies, which fosters the validation of the simulation tools and theory to existing observations. Examples
include (1) multi-scale predictions of turbulent transport,6,7 which have been subsequently observed inexperiment,8 (2) the impact of turbulence on neoclassical tearing modes (NTM),9,10 and (3) the
development of high-gain scenarios for ITER and other planned devices.11 While extensive validation
against experimental databases of reduced models is still required, examples of the success of this reduced
model development is seen in Figure 2.2, which shows the comparison between reduced model
predictions and experimental observations for the plasma core (Figure 2.2a) and plasma edge (Figure2.2b). These two models have been coupled to produce the core-edge optimized scenarios for burning
plasma studies.12 The coupling of experiment and theory, along with expanded computational capabilities,
have been determined through experimental observations of turbulence characteristics as well as throughcomprehensive, physics-based numerical simulations.
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FIGURE 2.2 Validation of model predictions for plasma pressure and energy. (a) Comparison of reduced
model prediction to experimental measurements of core plasma stored energy and (b) comparison of predicted
and measured edge pedestal pressure. SOURCE: Kinsey et al., Nucl. Fusion 51:083001, 2011l (b) Snyder et al.,Nucl. Fusion 51:103016, 2011.

An example of successful core-edge plasma optimization is to improve the performance of aburning plasma. This achievement was made possible by the recently developed capability to use physicsbased core-edge coupled numerical simulations to predict plasma characteristics across the entire plasma.
The predicted scenario was achieved through strong plasma shaping and by carefully controlling the
trajectory of the plasma density to open access to a regime with stable, high density and pressure plasmaedge.13,14 This optimization has led to the achievement of record pedestal pressures that are withinapproximately 10% of the ITER target15 and also led to equivalent fusion power gain, defined as Q, with
D-T equivalent Q over 0.5 achieved on DIII-D.16 Another optimization led to another world record for the
average plasma pressure achieved for any fusion device, as indicated in Figure 2.3. While the ITER target
goal of Q = 10 can be achieved with the expected performance in conventional operation, applying these
optimization techniques to ITER plasmas can potentially enhance performance beyond the Q = 10 range.
Research has led to the understanding of zonal flows in plasma turbulence,17 and the role of single
and multi-spatial scale effects in driving transport.14,18,19,20Error! Bookmark not defined. Research has shed light on
the structure and formation of the H-mode pedestal. 21,22,23 In plasma stability, an understanding of theeffects of and plasma response to applied 3D magnetic perturbations,24,25 as well as of the plasma
behavior during disruptions26 and disruption mitigation,27 has been developed. Finally, comprehensive
simulations28 have been used to understand processes controlling the scrape-off layer heat flux width, andthey project to a more optimistic scenario for heat flux width on ITER than previously thought.29
Plasma Stability and Operational Boundaries
Magnetohydrodynamic (MHD) instabilities in tokamaks are large-scale perturbations to theplasma that are driven by the plasma pressure and current, and which can lead to degradation of plasma
performance through enhanced radial transport of plasma and energetic particles. If not controlled, alarger-scale instability may lead to abrupt terminations of the plasma, called “disruptions.” Operationalboundaries are defined by those plasma parameters where these instabilities can be avoided or controlled.
For the ITER baseline scenario for achieving Q = 10, pressure-driven kink and resistive wall instabilities30
are avoided by operating below plasma pressure limits. However, the ITER baseline scenario issusceptible to neoclassical tearing modes (NTM) that are driven by plasma current density.31,32 Significant
progress toward meeting the challenge posed by tearing instabilities has occurred for the ITER baseline
stability by way of better understanding of the roles of plasma rotation, plasma collisionality, and the use
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Permission Pending

FIGURE 2.3 Maximum pressure obtained in 49,110 discharges spanning the lifetime of the C-Mod experiment(+), vs. B IP / a, where the average plasma pressure is given by <P> (Pa) = 4000 βN (B Ip/a). The world recordpressure was obtained using high magnetic field (B = 5.7 T) and physics-based optimization. The ITER target
parameters are indicated, as well as some noteworthy high-performance discharges from the TFTR, JET, andDIII-D experiments. See J.W. Hughes, et al 2018 Nucl. Fusion in press https://doi.org/10.1088/17414326/aabc8a.

of various control actuators, including cancelation of unwanted magnetic field errors33 and localized
plasma current drive34 and optimized with advanced feedback and search algorithms.35
Active techniques include tailoring the plasma profiles with various heating and current drive
schemes, as well as applying 3D magnetic field perturbations at the plasma edge.36 Achieving highplasma βN can also be aided by a judicious choice of plasma shaping and configuration. For instance, inthe more “spherically shaped” NSTX plasmas, stable high-βN discharges were produced routinely with theaid of stabilization techniques.37 Stabilization studies in the mid-sized U.S. tokamaks DIII-D and NSTXU, along with further development of techniques to stabilize and control the plasma, including
development of physics-based models of MHD instability thresholds, are necessary to inform decisions
on an optimized shape and configuration for producing steady-state plasmas in a fusion pilot plant.
Steady-state operation with large self-induced plasma currents, called “bootstrap current” requires both
high pressure and low plasma current. In order to accomplish this, both passive and active plasma control
techniques need to be developed and incorporated into closed-loop feedback algorithms beyond theirpresent state.
The fraction of self-generated “bootstrap” current, fbs ≈ 0.02 q βN A1/2, is related to the plasma
safety factor, q, the plasma aspect ratio, A, and the plasma pressure, characterize by the normalized
pressure parameter, βN. (See, for example, Zohm, et al., Nuclear Fusion 57, 086002 (2017) for discussionof these formula.) Shown in Figure 2.4, the fraction of self-generated “bootstrap” current reaches 100%
when βN ≈ 25/q for ITER parameters when A = 3. High bootstrap current fraction is a goal for efficient
steady-state operational scenarios that require minimal injected current drive power. The TCV tokamak in
Switzerland achieved 100% bootstrap current in 2008.38 Passive control techniques use the stabilizing
influence of image currents in conductors that are proximate to the plasma.39,40

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q95 = 6

p
tra
ots
Bo

Conventional
Tokamakq95 = 5

SteadyState

EquilibriumLimit

Advanced
Inductive
Curre
nt Limit

Fusion Powerq95 = 40%
10

Increasing Plasma Pressure →q95 = 3

N=5

N=3

BootstrapPlasma
Current Fraction
Decreasing
Current →FIGURE 2.4 Stability requires plasma pressure and plasma current to be lower than limits shown above. The
ITER baseline target is a “conventional tokamak.” As the plasma current decreases, efficient “steady-state”
operation becomes possible because the “bootstrap” current sustains the plasma without the need to drive
current. SOURCE: Luce, Phys. Plasmas, 18, 030501 (2011).

Energetic Particle Physics
Burning plasmas will be self-heated by the -particles (He++) produced from fusion reactions. To
date, only TFTR and JET operated with significant amounts of tritium to allow study of energetic αparticles. Both devices produced modest levels of fusion power, and the fraction of -particle heating
power to heating power supplied externally was low, between 10 and 15%. Burning plasma experiments
in ITER are expected to achieve a fraction of -particle heating power exceeding 60%.
Other fusion experiments without significant heating from fusion reactions do not generate an particle population; however, the energetic particle (EP) population created from neutral beam heating
can serve as a proxy for the -particles. Some present-day fusion experiments can produce an EP
population that resides in the same “phase space” as that for the -population expected in both ITER anda burning plasma produced in a more spherical configuration (see Figure 2.5). The EP phase-space ischaracterized by the fraction of energetic particle energy relative to the total plasma energy and speed of
the EP motion relative to an Alfvén wave.
The dynamics of the EP population are governed by classical collisional processes in MHDquiescent plasmas. A sufficient EP population, however, can drive instabilities, which can then interact
with the EP population and affect performance through loss or redistribution of the energetic particles,
leading to reduced plasma heating.
The past decade has seen significant progress in both understanding and mitigating the EP-driven
instabilities in both stellarators and tokamaks.41,42 Theory and numerical simulation advances have led tothe development of models, validated by experiment, that predict the existence and characteristics of EPdriven modes, as well as their resulting interactions with the EP population itself.43,44,45,46,47 This has
allowed for accurate descriptions of their ability to heat the plasma and drive current. Presently, reduced
models of the modes and their interactions are under development, and, along with reduced models ofplasma transport and stability, will lead to a comprehensive physics-based capability for developing the
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FIGURE 2.5 Energetic particle (EP) “phase space” for NSTX-U, present day higher aspect ratio tokamaks,
and phase space regions expected for α-heated tokamaks at both low and high aspect ratio. SOURCE: Courtesyof E. Fredrickson and the Princeton Plasma Physics Laboratory.

operational scenarios necessary for ITER to achieve its Q = 10 target. Furthermore, this model
development will leverage off of the success in mitigating EP-driven instabilities through “phase spaceengineering,” in which neutral beam48 and radio frequency wave49 actuators are used to tailor the EP
phase space in order to control the detrimental consequences of EP instabilities without compromisingheating and current drive performance. These same actuators are planned for ITER.
While the tools and understanding that has developed over the past decade are sufficient fordeveloping scenarios in which ITER can achieve its Q = 10 goal, only the study of the -particle
population generated by these burning plasmas will help ensure extrapolation from relative short-pulse
fusion power production to one where -particle modes can remain stable in long-pulse, steady-state
operation.
Mitigation of Transients and Abnormal Events
Transients, or abnormal events, are phenomena that are short-lived and that release plasma energy
at levels that can damage plasma facing components (PFCs). These phenomena include major disruptions
and more localized plasma edge instabilities called Edge Localized Modes (ELMs).
Major disruptions are due to crossing into unstable operational space in current, density or , or totechnical system failures, and result in most of the plasma and magnetic field energy being released
within thousandths of a second. The disruption can also result in a beam of relativistic electrons, which
can cause highly localized damage to the reactor inner wall. While present devices are capable ofhandling these disruption loads, at least an order of magnitude increase in plasma and field energy content
is estimated for ITER and future reactors, and therefore it is essential to develop reliable methods to avoid
or mitigate disruptions to avoid damaging vessel components, to allow achievement of high fusion power
density and to ensure continuous operation in a reactor.
Significant progress in disruption control has been made on three fronts: prediction, avoidance,and mitigation. Real-time descriptions of conditions that can lead to a disruption have been developed
within empirical frameworks,50,51,52 and these have led to predictability at or above the 95% level. For
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FIGURE 2.6 Examples of visible images from different rapid shutdown methods from DIII-D showing (a)massive gas injection, (b) shattered pellet injection, and (c) large intact pellet injection. Green curves areapproximate plasma magnetic flux surface contours in tangency plane for orientation only. SOURCE: E.M.
Hollmann, et al., "Status of research toward the ITER disruption mitigation system," Phys Plasmas 22, 021802(2015).

early operations in ITER, predictability higher than 80% is required, although 98% disruption
predictability is required at ITER’s full operational capabilities.53 Recent advances have included
developing machine learning/neural network approaches,54,55,56 real-time monitoring of plasma
stability57,58 and incorporating real-time stability calculations from reduced, physics-based MHD stability
models to warn of an approach to stability limits.
If a disruption cannot be controlled or avoided, it would need to be mitigated, and progress to do
this has been made using injection of gas, liquid and solid, which can cause high enough radiation to
decrease the plasma energy content and provide high enough collisionality to inhibit the formation of
runaway electron beams.59,60,61 Shattered pellet injection, successfully developed on DIII-D,62 has been
adopted as the mitigation technique-of-choice for ITER. Demonstrations of post-disruption runaway
electrons using shattered pellet injection (SPI) and massive gas injection (MGI) in the DIII-D experimentare shown in Figure 2.6. After injection of pure (100%) neon or argon atoms, total dissipation of fully
avalanched runaway electron beams is achieved.63 Novel methods, like shell-pellet injection,64 have been
demonstrated. Other methods to use radio frequency waves to dissipate runaway electrons have been
proposed65 that will be tested on DIII-D and could potentially be employed on ITER.
Edge Localized Modes, or ELMs, are features of H-mode plasmas in which the high edgepressure and pressure gradients cause intermittent edge instabilities that can release significant amounts ofenergy to the PFCs. The accompanying impurity influx from these material surfaces can lead todegradation of plasma performance. As with disruptions, present day devices are capable of handling thepeak and averaged heat loads from ELMs, but even a 0.3% (~1 MJ) loss of thermal energy in ITER canlead to PFC damage.
A variety of mitigation methods have been developed and tested successfully on present-day
devices. Three-dimensional edge magnetic fields have been applied to both mitigate and suppress
ELMs66,67 ,68,69 (see Figure 2.7). Repetitive injection of solid pellets was used to control the frequency of
ELMs.70,71,72,73 Deposition of lithium on the walls has been used to reduce the frequency of and ultimately
eliminate ELMs.74,75 Additionally, there are naturally occurring ELM-free regimes in which edge
instabilities flush out impurities but preserve plasma performance,76,77 and these regimes can be used as abasis for the optimized core-edge coupled operating scenarios in steady-state devices.
Fusion Technology and Engineering Science

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FIGURE 2.7 (a) DIII-D ELM suppression in an ITER Baseline-similar plasma using an applied magnetic
field supplied by the I-coil. (b) Similar internal coils will be used in ITER. The ELMs (spikes in D in top
panel) disappear when the external field is applied. SOURCE: Courtesy of M. Wade and General Atomics.

In addition to the scientific progress in the preparations for burning plasma operation in ITER,
progress in fusion technology and engineering science has been significant. The fabrication ofsuperconducting magnets (Figure 2.8), the ITER cryostat, and vacuum components are in progress. ITER
has been licensed as a first-of-a-kind basic nuclear fusion facility. And ITER construction is now morethan halfway completed to first plasma. Additionally, since the 2004 NRC Burning Plasma Assessment
report,78 fusion technology advances have been driven by ITER research needs and by next-step goals to
fully enable the fusion energy system. Key contributions from the U.S. fusion technology program inrecent years have led to successful progress in blanket research,79 tritium and fuel cycle research,80 fusion
safety and environmental aspects,81 remote handling approaches,82 fusion materials science,83
superconducting magnets,84 and fusion energy systems studies.85 These contributions have resulted fromjoint international projects in support of ITER and from tasks directed by U.S. researchers.
Accomplishments include (but are not limited to) the development of vacuum and gas species
management,86,87 tritium fusion fuel cycle systems,88 pellet injection for fueling and disruption
mitigation,89 and the manufacture of the ITER central solenoid.90
RESEARCH PROGRESS BEYOND ITER TOWARD FUSION ELECTRICITY
International research progress preparing for burning plasma study on ITER has also increased
the state of readiness to undertake research beyond ITER leading toward the construction of follow-on
devices that demonstrate fusion power production and the potential for economical fusion electricity. In
Europe, Japan, South Korea, and China, research beyond ITER is directed to develop the interconnectedscience and technology needed to design and construct a device to demonstrate fusion power. Just as
ITER has provided a research focus for international fusion researchers to advance burning plasma
science, a strategy for the accompanying research and technology programs needed to progress beyond
ITER to a commercial fusion reactor guides national research and innovation programs, helps to engage
industrial partners, and sets national priorities.

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FIGURE 2.8 (a) Ground insulation being applied to a central solenoid superconducting module atGeneral Atomics (Poway, CA). The insulation must be precisely placed and consists of 18 layers offiberglass, six layers of Kapton sheets totaling over 2,300 square meters, and a ground plane. (b) The
ITER central solenoid will consist of six stacked modules, stand nearly 18 meters tall, and weigh morethan 900 tons. When completed, it will be the largest pulsed superconducting magnet in the world.

Plasma Exhaust Physics
While temperatures in the core of the magnetically confined plasma can be up to 100s of millionsof degrees K, the plasma cools as it is transported radially from core to edge through plasma transport,
radiation, and other processes. Nevertheless, the edge plasma temperature can still be in the 10s of
millions degree K range, and is much greater than the temperature that can be withstood by surrounding
walls, for which there is an upper limit of ~1500 to 3000 K for most solid material to avoid melting.91
Even at lower temperatures, the Plasma-Material Interactions (PMI) between the hot plasma and solid
surfaces can cause drastic changes in the integrity of the wall material, notably through physical andchemical erosion. This can introduce impurities into the plasma, which can degrade plasma performanceand fusion gain.92,93,94
There has been considerable progress over the last decade in mitigating heat fluxes escaping theplasma by various means that increase the area over which the heat is deposited. One such method isthrough plasma “detachment” from the divertor targets, obtained by additional gas fueling in the divertor
region, which increases density and lowers the temperature of the plasma in the divertor region primarily
through radiation.95,96 Detachment can lead to factors of several decrease in the heat flux deposition
without impacting the performance of the core plasma.
While detachment in a conventional divertor alone is estimated to reduce heat loading in ITER to an
acceptable level by radiating 60-70% of the escaping heat flux, a next-step burning plasma may haveheating and fusion powers greater than those expected in ITER, and with a conventional divertor, up to
90% of the heat exhaust would have to be radiated away to avoid material surface damage; at these levels,
core plasma performance could be severely affected.97 Studies of the compatibility of innovative divertor
designs with divertor plasma detachment, which can significantly relax the radiated power requirement,
are needed.
Innovative divertor designs use more complex magnetic topologies to spread the heat flux over a
wider area on the target plates. This is done by increasing the field line length, which allows for additionalcross-field transport of the heat, making the angle at which the field lines impinge on the surface
shallower, and increasing the broadening of the magnetic field lines “tubes.” Innovative configurations
that have shown heat flux reductions on a variety of devices include the Snowflake,98,99,100 the X-divertor,
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FIGURE 2.9 Innovative divertor configurations may improve fusion power and particle handling.
Shaping the magnetic field changes the nature of plasma interaction with the divertor armor andgeometry, as shown with the colored lines used to trace magnetic field lines. SOURCE: Figure provided
by H.Y. Guo and General Atomics and reprinted from “Magnetic Fusion Energy: From Experiments toPower Plants,” ed. By G.H. Neilson, Woodhead Series in Energy, No. 99, Elsevier, 2016.

and the Small-Angle Slot divertor.101,102 The Super-X103 divertor is closely related to the X-divertor, andboth will be studied on MAST-U104 tokamak. Also related to the Super-X is the X-point target divertor
concept.105 These various innovative divertor configurations are shown in Figure 2.9.
Liquid metal (LM) surfaces are a potentially transformative solution to the heat flux challenge forall magnetic configurations, as the damage and/or erosion that can occur in solid PFCs are eliminatedsince the liquid metal walls are continually replenished with new, clean surfaces contacting the plasma.
Liquid metals are renewable, and they return to equilibrium after perturbations. LMs can handle heat
fluxes up to factors of several over the upper limits for solid walls.106 One of the leading candidates for
LM walls is lithium, which, when coated on solid walls through evaporation, led to improved
confinement107,108 and suppressed or mitigated ELMs.109,110 Liquid lithium surface research anddevelopment on tokamaks is in the early stage ,111,112 and the challenges involve their design, stability inthe presence of magnetic fields, retention of tritium (an issue for both liquid and solid walls)113 andimpact on plasma performance.114,115

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Driving Plasma Current
Among the key challenges for obtaining a steady-state burning plasma beyond ITER is thecapability to drive the plasma current non-inductively. This is of fundamental importance in tokamaks
since tokamak confinement improves with the poloidal magnetic field that is produced by the plasma
current. Efficient steady state operation in a tokamak requires operation in plasma regimes that yieldsignificant self-driven (or “bootstrap”) plasma current.116 It is important that the self-driven current profile
lead to a scenario that is stable to large-scale magnetohydrodynamic (MHD) instabilities.
The physics of externally produced non-inductive current drive (CD), from neutral beams (NB)
and radio-frequency (RF) methods such as electron cyclotron (EC), lower hybrid (LH) and fast waves(FW) are now well understood and are documented in the ITER physics basis.117,118 Recently, current
drive by high frequency “helicon” waves has been proposed.119 Most robust and free from accessibility
issues are NBCD and ECCD. ECCD is particularly attractive since it can achieve the highest transmission
power density, and the space necessary for power injection is smallest. Local current drive by ECCD can
suppress internal MHD modes and the local ECCD is also effective for local pressure profile modification
to further enhance plasma performance. The challenges facing ECCD include the relatively high cost ofsources, the possible need for new source development if high fields are used, and the lower current drive
efficiency for off-axis current generation which may be necessary for high bootstrap fraction. In contrast,
LHCD already has readily available sources at lower costs and the off-axis current drive efficiency isperhaps the highest of any of the RF options. On the other hand, LHCD has important challenges becauseof the need for a close-to-the-plasma-edge launching structure.
Establishment of a high-bootstrap-current-fraction, fully non-inductive tokamak plasma at
sufficiently high normalized-beta using reactor-relevant and efficient current drive systems is a criticalresearch subject for developing steady-state scenarios and being able to operate in the reduced tritium
breeding blanket space of a compact configuration.
Integrated Burning Plasma Configurations
Perhaps the greatest challenge faced in a burning plasma regime is the simultaneous solution to
all of the above issues to achieve the overall goal of a fusion power system capable of uninterrupted
operation. Measuring progress on multiple design metrics is not trivial. A number of the issues, including
self-driven “bootstrap” current, external current drive and plasma heating systems, plasma-materialinteractions and power handling, and robust control and mitigation of transients, are to some extent
measured by the normalized fusion gain (or triple product) and the duration of uninterrupted plasma
confinement pulses. (See Figure 4.5 in Chapter 4.)
Burning plasmas must simultaneously achieve a high triple product while eventually being
sustained for months of steady-state operation. Until now, short pulse experiments built with copper
magnets have operated for several seconds and have achieved conditions equivalent to “scientificbreakeven,” or Q ~ 1, when extrapolated to operation with deuterium-tritium fuel. Longer pulse studies
using experiments with superconducting magnets have been performed,120,121,122,123 but these researchdevices are not large enough to operate at the high pressures needed for fusion gain. High power density
scenarios capable of steady-state should be explored in actual reactor-like conditions, providing scientists
the opportunity to study coupled electron-ion turbulence, super-Alfvénic ion distributions, and highopacity plasma edge. The highly non-linear interactions between different phenomena in fusion
equivalent regimes, defined at reactor relevant integration parameters, have not yet been examined.
A critical integration aspect upon reaching fusion equivalent regimes is to reconcile the core andthe edge. Because the plasma collisionality parameter, ν* scales strongly with the ratio of plasma density
to plasma pressure, ν* ~ n3 / P2, the parameters of both the divertor and the plasma core cannot
simultaneously operate at reactor relevant parameters unless absolute reactor-relevant plasma pressure, P,
is achieved. Because the plasma core and edge strongly interact, the core-edge-divertor interactions are
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2-11altered by increasing neutral opacity as reactor-like densities are approached. As the fusion equivalentregime is approached, the divertor, scrape-off layer (SOL) and pedestal become increasingly opaque, andpedestal profiles become more strongly dependent on transport and pinch effects. Divertor and plasma
confinement are linked, and integrated solutions require both regions to be in the relevant density
regimes.
Another major issue is integrating the design and operation of tokamaks with requirements andtechnology imposed by future reactor engineering constraints. Progress toward this integration has beenslow since plasma science and device performance are each a necessary first step. As devices approach
the burning plasma regime it is appropriate to embrace design choices that are compatible with a futurecompact pilot plant. Notably, this includes operating with metal walls to minimize tritium retention,
optimization of the geometry/topology of magnets, and measurement/control systems that can operate in a
nuclear environment. In addition, the tritium breeding ratio and corresponding blanket design should becompatible with overall plasma performance.
Three-Dimensional Magnetic Fields and Stellarators
The study of very long pulse, toroidal magnetic confinement is underway using major researchfacilities using superconducting magnets. EAST (China), KSTAR (Republic of Korea), WEST (formally
Tore-Supra, in France) are superconducting tokamaks, as is also ITER and the JT-60SA experiment underconstruction in Japan. The two superconducting stellarator facilities are the Large Helical Device (LHD)in Japan and the Wendelstein 7-X (W7-X) device in Germany. Because tokamaks and stellarators havestrong magnetic fields and toroidal geometries, the fusion science and technologies of tokamaks andstellarators are similar. The fundamental dynamics of plasma confinement are described with the same
methods; scientists produce and diagnose confined plasma using the same technologies; and tokamaks
and stellarators are challenged to achieve and sustain the same fusion equivalent conditions.
Stellarators and tokamaks differ by the degree by which the magnetic field is three
dimensional.124 Tokamaks, like ITER, use relatively small three-dimensional magnetic field perturbations
to control plasma instabilities, such as edge localized modes (ELMs), and influence plasma profiles andflows. (See Figure 2.7.) As the degree of three-dimensional magnetic field increases significantly, theusual confinement properties that arise from symmetry are broken and particle confinement requires
carefully designed three-dimensional magnetic fields to avoid rapid particle loss. Careful design is also
necessary for the three-dimensional magnetic fields used to control tokamak plasmas,125 and this further
motivates ongoing research linking the science of strong three-dimensional magnetic fields optimized forstellarators and the weaker three-dimensional magnetic fields needed to optimize performance of
tokamaks, like ITER.126
Understanding transport in stellarators (Figure 2.10) has led to the design of a new class ofstellarators that have recently commenced operating. Transport in early stellarators was dominated bycollisional, or neoclassical, processes. Neoclassical effects cause the cross-field transport of otherwise
trapped particles as well as large impurity fluxes, which can dilute the plasma and compromise
performance. However, advances in theory and in numerical tools have led to identifying stellarator
configurations with various optimizations of the magnetic field that predict a reduction in neoclassicaltransport to levels comparable to those in tokamaks.127,128,129 The development of optimization codes havesuccessfully designed of stellarators with reduced neoclassical transport.130 A major new facility withsuch optimization, W7-X in Germany,131 recently began operating, and experiments have confirmed thethree-dimensional magnetic field optimization.132 A prime goal of W7-X is to test fusion magnetic
confinement for one such optimization scheme and the balance between neoclassical and turbulencedriven transport. The experiments will serve to validate results of several gyrokinetic codes, including thefirst fully global and physically comprehensive turbulence codes, which have recently been developed.133

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FIGURE 2.10 Strong three-dimensional magnetic fields can create stellarators optimized to confine
particles. (a) The HSX stellarator at the University of Wisconsin is the world’s only quasi-helically symmetricstellarator. (b) The Wendelstein-7X stellarator in Germany is built from superconducting magnets in aconfiguration that minimizes equilibrium plasma currents.

Some MHD and energetic particles instabilities are predicted to behave differently in stellarators
than in tokamaks. Understanding these differences will help to better control a burning plasma and tobetter predict fusion performance. For example, some stellarator configurations, like that used in W7-X,
minimize the toroidal plasma current, and plasma current induced MHD instabilities can potentially be
avoided. Other stellarator configurations, like the proposed National Compact Stellarator Experiment(NCSX),134 are predicted to reduce the toroidal plasma current by more than half an equivalently sized
tokamak. Because relatively few stellarators have been built and studied, stellarators provide new tests ofour understanding of plasma stability limits. Although disruptions are absent in existing low current
stellarators,135 because high-pressure plasma confined within a quasi-symmetric stellarator are predicted
to generate significant bootstrap current, current-driven instabilities and plasma current disruptions mayneed active methods for controlling the plasma profiles and mitigating the effects of transients just as intokamaks. MHD-stability studies have been ongoing in LHD136 and will be undertaken in W7-X andCTH.137
Stellarators also provide opportunities to investigate plasma heat flux issues and to better
understand how to design an optimized divertor. Because the stellarator the configuration is intrinsicallythree dimensional, the design, maintenance and replacement of a stellarator divertor more complicatedthan in a tokamak while also providing an opportunity to validate three-dimensional models of the plasmaedge and the plasma interaction with the first wall. There are several types of divertors that are being
assessed on stellarators, including the helical divertor138,139 and the island divertor.140,141 Stellarator
divertors have not been tested to the extent that they have been tested on tokamaks. Nevertheless, thesechallenges are common to both stellarators and tokamaks and include understanding the plasma boundary,including the effect of edge magnetic field shear, active control requirements and assessing compatibilityof divertor solutions in a high-performance integrated core-edge coupled regime.142
Theory and Simulation at the Exascale
For many years, the U.S. effort in basic theory, simulation, and modeling of fusion plasmas has
been extremely strong, with many U.S. scientists being recognized internationally as world-leaders intheir respective fields. United States fusion researchers have been instrumental in driving recent, andseminal, progress in several diverse areas. Both analytic theory and reduced models and high-fidelity
physics simulations development comprise this impressive set of accomplishments.
Theory and simulation offer important new opportunities for accelerating progress toward theobjective of economical fusion energy development by incorporating recent advances in theoreticalunderstanding, validated physics models, computing infrastructure, and diagnosis of experiments.143,144 As
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described in the Report of the 2015 Workshop on Integrated Simulations for Magnetic Fusion Energy
Sciences,145 what is needed is to comprehensively and self-consistently advance the many complex,
nonlinear, and multi-scale plasma descriptions into an integrated suite of Whole Device modeling (WDM)
capabilities.146 The long-term goal of the project is to have a complete and comprehensive application thatwill include all the important physics components required to simulate a full toroidal discharge. Such a
predictive modeling capability is required, e.g., for the interpretive analysis of existing devices as well as
for minimizing risks and qualifying operating scenarios for next-step burning plasma experiments. In all
future burning plasma facilities, the optimization of fusion performance and control scenarios will requirepredictive WDM with a quantified, validated uncertainty, as it will not be feasible to determine
operational limits by running trial discharges.
The following research elements are critical for realization of a successful WDM capability:Continued efforts to better understand and distill the physics of gap areas in fusion theory.
These gaps include understanding transients, the plasma boundary, fully non-inductive
operation, and optimization of the toroidal magnetic configuration.
Increased development of and support for modular WDM frameworks. A sustainable pathforward will require support both for the most mission-critical legacy tools and fordevelopment and expansion of the newer efforts that can more effectively utilize leadershipclass computing resources and execute next-generation work.
Increased connection to experiment through validation. This will require the development
and extensive use of tools that fulfill validation hierarchies and compute associated metrics,
as well as an accurate and comprehensive set of diagnostics. Such an approach will require
expertise in large-scale data management and analysis, including machine-learning strategies,
for both leadership-class code output and the experimental observations against which they
will be tested.

While present models can help develop operational scenarios for ITER and increase confidence inachieving its goals, a validated WDM capability would provide the confidence to explore the extreme
parameter regimes of fusion reactors, informing decisions and lowering the future risks of building fullscale fusion power plants, and thus accelerating the fusion program.
Transformative Enabling Technologies
In addition to projects in support of ITER and domestic FES research activities, the fusion
program can leverage technology developments in areas that have significant potential to advance fusionenergy development. In order to capture the impact of such advances and identify ground breaking
research opportunities for advancing fusion energy, the Fusion Energy Sciences Advisory Committee(FESAC) was recently charged “to identify the most promising transformative enabling capabilities(TEC) for the U.S. to pursue that could promote efficient advance toward fusion energy,” The FESAC
TEC report147 identified four areas of transformative enabling capabilities where, building fromsignificant progress in certain areas of research, the U.S. has a strategic opportunity to developtransformative technologies to enable fusion energy. The four top-tier TECs identified by the panel were:advanced algorithms, high critical temperature superconductors, advanced materials, and novel
technologies for tritium fuel cycle control.
Advanced Algorithms

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Permission Pending

FIGURE 2.11 Importance of advanced algorithms is illustrated with (a) a “control operating map” fora burning plasma showing the level of controllability for several control parameters and (b) a schematicof the ITER disruption mitigation system (DMS) requiring off-normal fault response. SOURCE: Fig.
4.1.1 of Fusion Energy Sciences Advisory Committee Report on Transformative Enabling Capabilities
for Efficient Advance Toward Fusion Energy, (2018)) and (b) J.A. Snipes, et al., “Overview of thepreliminary design of the ITER plasma control system,” Nucl. Fusion 57 (2017) 125001.

Advanced control systems are required to control a burning plasma during the normal evolutionof the plasma and, also, during transient events that need to be either predicted and avoided or mitigated.
Advancements in feedback algorithms and intelligent systems may significantly improve the reliability offusion power and perhaps enable operation at optimized operating points whose achievement andsustainment are impossible without high performance feedback control. As explained in the TEC Report,
the area of advanced algorithms includes the related fields of mathematical control, machine learning,
artificial intelligence, integrated data analysis, and other algorithm-based research and development. The
importance of advanced algorithms is illustrated in Figure 2.11, which shows the variables and control
functions in a fusion plasma “control operating map” and a chart illustrating the control function
interactions for ITER's disruption mitigation system (DMS). As understanding of burning plasma
operation improves, advanced control algorithms will support and accelerate the pace of physics
understanding, enable the experimental realization of theoretically predicted operating scenarios, andbuild mathematical synergies with advances in other high-performance computing capabilities that will
enable improved physics understanding. Machine learning and mathematical control can also help tobridge gaps in knowledge when these exist, for example to enable effective control of fusion plasmas withimperfect understanding of the plasma state.148
High Temperature Superconductors (HTS)
Advances in higher field superconductors present a major opportunity to enhance theperformance and feasibility of fusion reactor designs. High-field, high-temperature superconductors
would enable a new generation of relatively compact fusion experiments and power plants, dramatically
speeding the development path and improving the overall attractiveness of fusion energy.149 HTS
technology could provide high energy gain and power density in much smaller devices, together with
operational robustness and steady state potential needed for successful fusion energy. Strong magnetic
fields are critical to the success of magnetic fusion as a source of energy. Achieving higher magnetic fieldstrength extends the allowable plasma properties to higher plasma density, higher plasma current, andhigher plasma pressure while retaining the same dimensionless scaling parameters found at lower
magnetic field strength. This extended range of plasma parameters from high-field magnets allows more
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compact tokamak devices that may provide a lower cost path to future fusion reactors. ITER’s
superconducting magnet system will be the largest ever made and is designed to operate with the highest
practical magnetic field strength for large toroidal field coils made of niobium-tin (Nb3Sn)superconductors and consistent with the strength of steel.150 New developments of rare-earth bariumcopper-oxide high-temperature superconductors (Figure 2.11) may lead to larger magnetic fieldstrength151 and improved maintenance that potentially improve the prospects for economical magnetic
fusion energy.152
Advanced Materials and Manufacturing
The behavior and integrity of materials in a fusion system are of great importance to the longterm viability of fusion energy.153 The flux of energetic neutrons to the vessel and structural materials
poses a serious materials problem that will require substantial testing, some of which may be done on aburning plasma experiment. The high energy neutrons from the D-T fusion reaction generate between 50
to 100 times higher He/dpa in materials such as ferritic steels than does fission reactor irradiation.
Burning plasma experiments will thus aid in the development of high-heat-flux components and willserve as testbeds in which to evaluate the performance of the components in a reactor-like fusion
environment.
The heat loads on components in a burning plasma experiment will be comparable to those
expected in a reactor and will require the application of state-of-the-art high-heat flux technology usingmaterials that satisfy requirements of tritium retention, safety, structural integrity, lifetime, and plasmacompatibility.154
Since the 2004 NRC Burning Plasma
Assessment report, the United States has madesignificant advances in fusion materials studies,including contributing to the qualification of reduced
activation ferritic martensitic steels for the European
demonstration fusion reactor,155 nanostructured156 andoxide dispersed strengthened steels,157 all aspects ofPermission Pending
SiC/SiC technology,158 and new understanding oftungsten159 and tungsten composites160 as fusion
plasma-facing materials. Linear plasma simulators
allow for long-duration study of material evolution
FIGURE 2.12 Photograph of Yttrium-based highunder fusion-relevant plasma flux, but they are nottemperature superconducting tape from Fujikura,useful to test integrated plasma-material effects
now routinely manufacturing wires with critical
expected in fusion divertors. In the United States,
current densities greater than 3 MA/cm2 andlinear plasma simulators include the PISCES facility at
production rates of 10-100 meter/hour.
University of California, San Diego,161 the Tritium
Plasma Experiment (TPE) at Idaho National
Laboratory (INL) (Figure 2.12), and the Material
Plasma Exposure Experiment being developed at Oak
Ridge National Laboratory.162
Qualification of materials to operate safely in a fusion environment is of critical importancemoving forward. Material effects have to be strongly connected to any consideration of availability,
reliability and maintainability of the fusion core. All of these have a large impact upon the threeoverarching factors of plant economics, public perception and ability to license.

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FIGURE 2.13 Advanced manufacturing used for enhanced heat exchanger structures. Left (a) shows aprototype tungsten heat exchange structure with 3D surfaces. Right (b) shows a variety of enhanced
surfaces made with selective laser melting (SLM). See review by Davoud Jafari and Wessel W. Wits,
The utilization of selective laser melting technology on heat transfer devices for thermal energy
conversion applications: A review, Renewable and Sustainable Energy Reviews 91 (2018) 420–442.

Looking toward future opportunities, new material designs and processes will enable therealization of resilient components that are essential to survive the harsh fusion environment and to
optimize the reactor’s performance. As reported by the 2018 U.S. DOE FESAC Committee on
Transformative Enabling Capabilities, “Advances in novel synthesis, manufacturing and materials design
are providing for some of the most promising transformation enabling technologies in PMI and nuclear
fusion materials to enable fusion energy for the future.”163 The novel features enabled by advanced
manufacturing and additive manufacturing include complex geometries and transitional structures, oftenwith materials or constituents including hard-to-machine refractory metals; the potential for local controlof material microstructure; rapid design-build-test iteration cycles and exploration of materials andstructures for containing and delivering liquid metals. The U.S. Department of Energy’s first
Manufacturing Demonstration Facility164 is located at ORNL and is developing new manufacturing
technologies beneficial for fusion energy technologies. These include advanced metals manufacturing:
electron beam melting, laser-blown metal powder deposition, laser sintering, and metal laser melting.
Figure 2.13 shows an example of selective laser melting (SLM) for complex manufacturing of enhanced
tungsten heat exchangers. With these emerging techniques, important new opportunities are emerging todevelop the resilient materials and components for a fusion energy system.
Fusion Blanket Research and Tritium Fuel Cycle
A fusion breeding blanket—that is, a nuclear system that creates tritium via interaction of thefusion-produced 14-MeV neutrons with lithium—is a key fusion nuclear technology needed for thedevelopment of fusion energy. Fusion reactors should operate with more tritium produced and recovered
than is burned. The vast majority of the fuel injected in a fusion chamber will not be burned in a single
pass. Unburned deuterium-tritium fuel will be continuously transported to the plasma edge, where it will
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be exhausted, stripped of impurities, and then reinjected into the plasma. A burning plasma experiment
provides the opportunity to test and evaluate the performance of prototypical blanket modules anddemonstrate technologies for tritium extraction from blankets and for fuel processing systems that can be
operated efficiently at large scale.165,166,167
Some recent successful activities in the U.S. include construction and operation of the MaPLE(Magnetohydrodynamic PbLi Experiment) facility168 international blanket research partnerships (e.g.,
Korean National Fusion Research Institute (NFRI)-UCLA-INL collaboration framework and UCLAEUROfusion collaboration), and innovative ideas in the tritium fuel cycle.169,170 In particular, significant
progress has been made in experiments and massively parallel simulations to understand magnetohydrodynamic flows of liquid metal, self-cooled, dual-coolant, and helium-cooled lead-lithium blanket
concepts.
It is well recognized that the development of a fusion breeding blanket is an outstanding
challenge for fusion because scientific gaps exist related to controlling tritium permeation and minimizing
tritium inventory.
While the 2004 report of the NAS Burning Plasma Assessment Committee noted the central roleof the ITER Test Blanket Module (TBM) in the United States fusion research program, the U.S. is not apartner in the ITER TBM Project, nor will the decision to incorporate TBMs on ITER be made until muchlater in the ITER construction schedule. While the signing of all of the TBM Arrangements (TBMA)
occurred in 2015, the TBM preliminary designs are not expected until 2023. The final TBM designs are
not expected until 2025, and the first installation of the TBMs will occur after 2030. Because the decision
to install TBM on ITER will not be made until after additional legal arrangements are signed dealing withall TBM phases through decommissioning,171 the careful consideration for the best approach to advancefusion tritium blanket technology could include becoming a supporting partner with a TBM activity alongwith other approaches.
The recent FESAC TEC131 report recognizes this challenge, and identifies several opportunities todevelop technologies with potential to address existing gaps, such as novel blanket technologies fortritium breeding that allow for higher thermal to electrical efficiencies and improved tritium breeding
ratios (TBR).172,173 advanced tritium extraction technologies,174 and new fuel recycling technologies thatallow for minimization of tritium inventories.175
Fusion Safety
A burning plasma experiment offers the opportunity to begin development of the technologies
needed for a fusion reactor, including important safety-related technologies. Many components andsystems needed for fusion’s safety objectives are unique, such as source diagnostics and cleaning
technologies, state-of-the-art safety analyses tools, technologies for the remote handling of large activatedcomponents, technologies for the control of routine tritium releases, and innovative approaches for thecontrol of tritiated and mixed waste streams.176 A burning plasma experiment will be an integrated
demonstration of the safety, reliability, and effectiveness of these technologies.177 In the United States,
recent progress has been remarkable in the areas of safety code development and understanding of tritium
behavior in fusion systems.
INL’s Safety and Tritium Applied Research (STAR) facility is a worldwide unique facility
capable of handling tritium and radioactive materials, as well as other controlled chemical elements suchas beryllium and lead.178,179 This facility provides opportunities for researchers to investigate thesynergistic effects of hydrogen isotopes in neutron irradiated fusion materials at burning plasma operating
conditions. Experiments at the STAR Facility include the Tritium Plasma Experiment (TPE), the Tritium
Gas Absorption Permeation (TGAP) Experiment, the Neutron Irradiated Material Ion Implantation
Experiment (NIMIIX), and the Experimental Chamber for Evaluation of Exploding Dust (ExCEED).
Recent progress has allowed researchers to expand the understanding of tritium permeation and retention
behavior in tungsten at prototypical fusion conditions. Not only have the number and types of traps been
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measured, but also how these crucial safety parameters vary with neutron irradiation history andtemperature. In addition, excellent progress has been made in the area of safety code development. The
MELCOR for fusion and Tritium Migration Analysis Program (TMAP) codes180 developed at INL, havebeen used for safety analyses in licensing ITER and design studies for many national and international
future fusion reactors. These computer codes are in use at more than 30 fusion institutions worldwide andhave recently been merged allowing for tritium tracking within a fusion facility during normal operation
and accident conditions.
Integrated Systems Engineering for Fusion
Integrated systems studies guide researchand identify programs that can reduce cost andlower risk to the development of fusion power.
Integrated systems studies combine burning
plasma science, materials science, fusion nuclear
science, and systems engineering to evaluate
safety, environmental and maintainability issues,and technical requirements to progress toward
fusion energy. Recent progress in systems
engineering studies in the United States and by ourinternational partners have had an enormous
impact on the direction of research to address
fusion economics, public perception and regulatory
framework.
Systems engineering combines plasma
FIGURE 2.14 Tritium Plasma Experiment (TPE) at
physics and engineering constraints into a selfIdaho National Laboratory is a linear plasma device toconsistent integrated design for large-scale fusion
accelerate deuterium and tritium plasma ions into metal
facilities. Systems engineering studies have beentarget samples. TPE test samples are first irradiated at thecarried out for various types of fusion reactors,
High Flux Isotope Reactor at ORNL to simulate fusion
including the advanced tokamak,181 high-field
neutron damage and then exposed to deuterium andtokamak,182 and the spherical tokamak andtritium to evaluate promising materials for use in fusion
stellarator.183 The United States has madedivertors.
significant progress in the area of fusion nuclear
systems study,184 leading to the definition ofrequirements for a Fusion Nuclear Science Facility (FNSF)185 for integrated testing of fusion components.
Figure 2.14 illustrates several examples of integrated systems studies, ranging from a pilot plant thatwould generate 73 MW of net electricity to a large commercial demonstration facility generating up to
300 MW of net electricity, operating without interruption, and designed with sufficient cooling for 1.5
GW of fusion power production. These systems engineering and integrated fusion systems studies are theprimary means to combine the knowledge obtained from burning plasma study with the interdisciplinarysciences needed to define the most optimal path toward fusion energy demonstration.

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Permission
Pending

FIGURE 2.15 Example next-step options resulting from integrated systems studies in the United States andin Japan. Each study combined burning plasma science with different engineering constraints andassumptions for large superconducting magnets. Integrated systems studies guide research and identify
programs that can reduce cost and lower risk to the development of fusion power. SOURCE: (a) J.E.
Menard, at al., Nuclear Fusion 56, 106023 (2016), (b) C.E. Kessel, et al., Fusion Eng. Des. (2017),
http://dx.doi.org/10.1016/j.fusengdes.2017.06.003, (c) Kenji Tobita, et al., Fusion Engineering and Design(2018), https://doi.org/10.1016/j.fusengdes.2018.04.059, and (d) B.N. Sorbom, et al., Fusion Eng Des 100,
378 (2015).

SUMMARY
Since the United States joined the ITER partnership, experiments using research facilities in the
United States and in other nations have been highly productive. New ideas to control and sustain aburning plasma have been discovered, and theoretical and computational models developed in the UnitedStates have substantially improved the ability to control plasma stability, predict plasma confinement, andenhance fusion energy performance. Methods to control and mitigate transients and scenarios that will
guide operation of ITER have been successfully tested. The understanding of burning plasma science hasadvanced significantly.
Finding: The U.S. fusion energy science program as part of the international research effort has
made leading advances in burning plasma science and technology that have substantially
improved our confidence that a burning plasma experiment such as ITER will succeed inachieving its scientific mission.
Although the primary focus of the world’s fusion research program is the preparation for ITER
experiments, progress has also resulted in the research aimed beyond ITER to address remaining scienceand technology challenges and demonstrate innovative solutions that lead to a reduced size, lower cost,full-scale power source. While this research is much less developed than the science and technology
required for a burning plasma experiment, opportunities exist to increase the readiness to benefit fromITER experiments and progress toward the demonstration of economical fusion power. New technologies,
such as high-field superconducting magnets, may reduce the size of next-step fusion demonstration

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experiments. Advances in understanding and predictive models also suggest that opportunities exist to
pursue more compact follow-on experiments.
Finding: In addition to burning plasma studies, further research in burning plasma science, fusion
nuclear science, and fusion materials science is needed to reduce the cost and fully enable thefusion power system.
Finding: New technologies for fusion, advances in understanding and predictive modeling, theimproved confidence in the science and operation of ITER, and the engineering systems studies
conducted both within the United States and by our international partners demonstrate a readinessto undertake the research leading to a cost-effective next step toward the realization ofcommercial fusion energy.

NOTES
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Lipschultz, A. Loarte, K. Miyamoto, T.H. Osborne, A. Polevoi, and A.C.C. Sips, Nuclear Fusion 47, S1(2007). http://dx.doi.org/10.1088/0029-5515/47/6/S01.
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3
Extending the Frontier of Burning Plasma ResearchThis chapter describes the importance of burning plasma research, explains why continued
participation as an ITER partner is important to United States fusion energy research, and describes how
ITER participation will inform the design of a compact fusion pilot plant as a new element of the UnitedStates magnetic fusion program. While decades of international collaborative research have been spentestablishing confidence in the science and technology basis for reliable pulsed operation in ITER, a
compact fusion pilot plant requires extending the burning plasma regime beyond ITER and achieving
uninterrupted operation having simultaneously high normalized confinement, high fusion power density,and a long-life divertor and first-wall. Because the physics basis of the compact fusion pilot plant is lessmature than the physics basis for ITER, hands-on experience and study of a burning plasma experiment,
like ITER, will be essential along the path forward to the U.S. compact pilot plant.
This chapter begins with a brief summary of the committee’s Interim Report assessment of theimportance of burning plasma research to the development of fusion energy and of the ongoing activitiesof the United States that supports burning plasma science and the ITER project is included. Next, research
activities that will maximize the benefits from U.S. participation in ITER and advance the science andtechnology needed to reduce risks in the design and operation of a compact fusion pilot plant arepresented. Chapter 3 concludes with three findings and with two recommendations for how the U.S. DOE
FES should conduct both the near-term and long-term ITER research. Chapter 3 also includes two
findings describing research needs if the U.S. withdraws from the ITER project and states thecommittee’s recommendation that the United States should not withdraw. However, if the United States
does withdraw from the ITER partnership, the U.S. DOE/FES should still initiate a plan leading toward
the construction of a compact fusion pilot plant. In the scenario without ITER, an alternate means to study
a burning plasma and to engage the international community would be required.
THE IMPORTANCE OF BURNING PLASMA RESEARCH
The importance of a burning plasma experiment as a required step in the development of practicalfusion energy has been endorsed by all previous strategic planning documents prepared for the UnitedStates fusion research program.1 As ITER partners, the fusion research programs of the United States andother nations have focused on preparations for the study of burning plasmas using the ITER experiment
for more than a decade.
Access to a burning plasma in ITER will open a new frontier in science. For the first time,scientists will observe the complex processes of a plasma that is primarily heated by the energetic
particles created by fusion reactions within the plasma itself. Even beyond the observation of a self-heatedfusion plasma, the study, control, and manipulation of a burning plasma in ITER will give scientists theirfirst opportunity to demonstrate many technical capabilities needed by any energy-producing magnetic
fusion device. ITER will extend the frontier of burning plasma research to include opportunities to learn
how to sustain a fusion plasma for durations much longer than previously achieved and how to maximize
the fusion power produced from a burning plasma. The frontier of burning plasma research also leads toprogress in the applied and engineering sciences needed to design reliable structures that surround theplasma and provides the first opportunity to gather materials data needed to design systems that convert
fusion energy into useful heat and power. In all of these ways, the science learned from study of burning
plasma in ITER will extend beyond ITER and contribute to the engineering science of large fusion energy
facilities and contribute to the applied science of predicting, controlling, and sustaining a magneticallyconfined burning plasma.
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The committee’s Interim Report reaffirmed the importance of burning plasma research to thedevelopment of fusion energy, as well as to plasma science and other disciplines. Furthermore, because
ITER is the only existing project to create a burning plasma at the scale of a power plant and also a major
component of the U.S. fusion energy program, the scientific and technical goals of ITER give clear
illustration of the importance of burning plasma research. ITER will demonstrate the scientific andtechnical feasibility of fusion energy for peaceful purposes. The ITER target is to sustain high fusion
power gain (Q ~ 10) for more than five minutes and to provide the capabilities to study advanced
operating scenarios and explore a wide range of fusion confinement parameters. Long plasma durations
exceeding 15 minutes are planned that will be useful for limited nuclear testing of tritium blanket
modules. For shorter durations, ITER will test advanced scenarios with elevated plasma pressure andhigher fusion power output that may allow investigation of ignited or near ignited burning plasmas. These
ITER research targets are ambitious, but the understanding of burning plasma science has advanced
significantly and the international effort to prepare for ITER operation has further increased confidence inthe burning plasma performance that can be achieved in ITER. As explained in Chapter 2, this is due tothe discovery of new ideas to control and sustain a burning plasma, the substantial improvements in theability to predict plasma confinement and fusion energy performance, and the demonstration of burning
plasma scenarios that are expected to simultaneously satisfy the requirements for stability, confinement,
fuel purity, and compatibility with plasma-facing components.
The importance of burning plasma research to the development of fusion energy is described
below in two parts: (1) understanding and controlling a burning plasma and (2) advancing fusion
technology and engineering science.
Understanding and Controlling a Burning Plasma
Burning plasma experiments in ITER will address critical research areas and answer key
scientific questions, including:

A burning plasma experiment will represent the first time that a confined fusion plasma isdominated by fusion-born alpha particles. Energetic alpha particles from fusion reactions heatand sustain the burning plasma, but they are also predicted to drive plasma instabilities.
While the onset of energetic particle instabilities is understood, detailed identification of
nonlinear mechanisms is just beginning. Beyond understanding energetic particle dynamics,
important research opportunities include methods to control energetic particles instability for
helpful purposes such as favorably modifying the current profile or to govern the nonlinear
dynamics to control fusion burn.
A burning plasma experiment advances understanding of plasma transport properties from thecore to the boundary. Although there has been considerable progress made in predicting
plasma transport, the validity of these predictions need to be tested in future burning plasma
experiments. In particular, confinement studies using a burning plasma will help determine
confinement scaling in desirable fusion reactor conditions characterized by high plasma beta,
steady state, and compatible divertors. In addition, transport of plasma impurities eroded frommaterial surfaces, as well as helium produced by fusion reactions, are not yet understood.
ITER experiments will give scientists a first look at heat and particle transport at the scale ofa fusion power plant.
A burning plasma experiment enables critical tests to control plasma transients. Due to thelarge energy of a burning plasma, transient events, which cause rapid energy loss from theplasma, may damage first-wall materials. Transients include plasma current disruptions andedge localized modes, called “ELMs.” The United States has led the world in thedevelopment of techniques for understanding, as well as predicting, avoiding and/or
controlling plasma transients. These techniques are critical for ITER and other burning

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



plasma devices, and ITER will provide a critical test of disruption avoidance and mitigation
systems at reactor scale and power density.
A burning plasma experiment advances divertor science necessary for a fusion power source.
Unless controlled, the power escaping from a burning plasma will lead to inner wall damage.
Control of escaping heat and particles is made by carefully shaping the magnetic field so thatplasma flows along the plasma boundary and into a divertor, where the plasma heat andparticle flux can be nearly extinguished by interaction with recycling neutrals. The U.S.
research program has significantly advanced understanding of burning plasma boundary
physics, including improved understanding of the narrow “scrape-off layer” connecting theconfined plasma to the divertor2 and the successful testing of innovative divertor concepts.3
However, further developments for a divertor with long lifetime remains a major fusion
research challenge, and ITER will enable detailed tests of divertor physics, including
detachment, retention, erosion and re-deposition in reactor-like conditions.
A burning plasma experiment tests integrated scenarios that simultaneously test therequirements for stability, confinement, fuel purity, and compatibility with plasma-facing
components needed for a fusion energy source. Plasma operation and control scenarios havebeen developed and tested in preparation for ITER experiments, and integrated models using
the latest advances in high-performance computing now routinely interpret experimental
measurements and make progress in predicting the results of burning plasma experiments.
Additionally, the U.S. research program has led the world in the development of quiescentplasma scenarios not subject to damaging transient events, which can achieve the same
plasma performance at reduced plasma current and so minimize the risk of disruption
damage. A burning plasma experiment can also test other advanced scenarios, like the socalled “super H-mode,” which represents an attractive area of innovation aimed to reduce thesize of a fusion device with improved confinement. An ITER research program focusedstrongly on advanced scenarios and physics model validation will enable an advance inunderstanding needed to develop an attractive, compact fusion pilot plant.
Advancing Fusion Technology and Engineering ScienceAs an ITER partner, the United States receives full benefit from the technology developed for
ITER. Because U.S. industry is fabricating major systems for ITER, burning plasma research is alsobuilding industrial capacity in fusion nuclear science, superconducting magnet engineering, nuclear
instrumentation, and plasma heating and control systems. Construction and operation of the ITER facility
addresses important research in fusion nuclear science and engineering science, including:

Fusion fuel processing, blanket design, and tritium breeding. The release of fusion energy
results from the fusion reactions of tritium and deuterium ions heated to 100 million degrees.
While deuterium is abundant, tritium will be produced from lithium within a fusion breedingblanket, which is a key fusion nuclear technology needed for the development of fusionenergy. Tritium for ITER will be obtained from the tritium removal facility of the Canadianowned Ontario Power Generation (OPG) utility using tritium produced within CANDU
nuclear power stations. The vast majority of the fuel injected in a fusion chamber will not beburned in a single pass. ITER will provide the first opportunity for large scale fuel processingof deuterium-tritium, which will be transported continuously from the plasma edge, thenexhausted from the vacuum chamber, stripped of impurities, and reinjected into the plasma.
ITER will also provide the first opportunity to test and evaluate the performance of
prototypical blanket modules and demonstrate technologies for tritium extraction fromblankets in ITER test blanket modules.4,5

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Fusion safety, remote handling, and waste management. As a burning plasma experiment,
ITER will provide the first opportunity to begin development of the technologies needed for afusion reactor, including important safety-related technologies. Many components andsystems needed for fusion’s safety objectives are unique, such as source diagnostics andcleaning technologies, state-of-the-art safety analyses tools, technologies for the remotehandling of large activated components, technologies for the control of routine tritium
releases, and innovative approaches for the control of tritiated and mixed waste streams.6
ITER will be the first integrated demonstration of the safety, reliability, and effectiveness ofthese technologies.7
Fusion materials science. As a burning plasma experiment, ITER will aid in the developmentof high-heat-flux components and will evaluate the performance of the components in afusion environment at the scale of a power plant. The heat loads on components in a burning
plasma experiment will be comparable to those expected in a reactor and will require theapplication of state-of-the-art high-heat-flux technology using materials that satisfy
requirements of tritium retention, safety, structural integrity, lifetime, and plasmacompatibility.8,9,10 Additionally, the behavior and integrity of materials irradiated by fusion
neutrons are of great importance to the long-term viability of fusion energy.11 The high fluxof energetic neutrons to the vessel and structural materials poses a serious materials problem
that will require substantial testing, some of which will be done on ITER.12
Plasma heating and current drive systems for fusion. Plasma heating by electromagnetic
waves and neutral particle beams are needed to heat the plasma to a burning state,13 sustain
plasma current,14 modify temperature and current profiles, and control plasma instabilities.15
Fusion reactor research continues to push the frontiers of high-power mm-wave and radiofrequency technology, and these technologies will be extensively tested at the reactor scale on
ITER.16
High-field magnet technology for fusion. Strong magnetic fields are critical to the success ofmagnetic fusion as a source of energy. Achieving higher magnetic field strength extends theallowable plasma properties to higher plasma density, higher plasma current, and higher
plasma pressure while retaining the same dimensionless scaling parameters found at lower
magnetic field strength. The superconducting magnets being constructed for ITER will be thelargest ever made and are designed to operate with the highest practical magnetic fieldstrength for large toroidal field coils made of niobium-tin (Nb3Sn) superconductors andsupported by steel.17Experience operating ITER’s superconducting magnets will advancephysics understanding of the role of magnetic field in a burning plasma and inform thedevelopment of large-scale superconducting magnet technology.

As the world’s first burning plasma experiment at the scale of power plant, ITER will provide
scientists the first opportunity to access the frontier of burning plasma research. The complex processes
within a burning plasma that couple plasma confinement, energetic particles created by fusion reactions,plasma stability, and fusion materials and technologies will be investigated. Because ITER is built at thescale of a power plant, ITER offers the first opportunity to begin development of nearly all of thetechnologies needed for a fusion reactor. In addition, as the first licensed fusion research facility, within
the licensing code requirements used by the French nuclear industry, the safe operation of ITER will
demonstrate necessary safety and operational procedures of a fusion power system.
THE IMPORTANCE OF ITER TO THE U.S. FUSION RESEARCH PROGRAM
Burning plasma research in support of ITER and in preparation for ITER experiments is a
primary focus of the fusion research programs of the United States and other nations. Preparation for
ITER experiments is a central element of today’s burning plasma research activities. Participation in the
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ITER project also provides formal mechanisms for U.S. scientists to take leading roles in the international
effort to develop fusion energy and to benefit significantly from international collaboration. Because theUnited States is a key contributor to ITER construction, participation in ITER has resulted in significant
advances in U.S. domestic industrial capabilities and capacities that would not have happened without
ITER participation.
The important role of ITER in the U.S. fusion research program is described below. First, theU.S. role in ITER construction is discussed and the resulting benefits to the United States in industrial
capabilities. Next, advances in fusion technology resulting from U.S. participation in ITER are presented.
Finally, research in preparation for ITER experiments provides a focus for ongoing burning plasma
research that has already resulted in substantial scientific progress in understanding, predicting, andcontrolling a burning plasma.
United States Partnership in ITER Construction
In December 2017, the ITER project passed the construction milestone of having completed 50%of the tasks required for first plasma operation. ITER is a large and ambitious facility. The fusion
containment vessel, superconducting magnets, and cryostat will weigh 23,000 metric tons. The largest
superconducting magnets are the poloidal field coils with a 24 m diameter. Each of 18 superconducting
toroidal field coils is 17 m tall, weighs 360 metric tons, and will be installed to a precision of less than 0.1
mm in the radial plates which support the large magnet forces.
Since the 2013 ITER Management Assessment Report,18 the new director, Bernard Bigot, hasplayed a key role in enacting rigorous project discipline in a nuclear project culture, enabling milestones
to be met consistently. Project decision processes and accountability have been substantially improved
through improved integration of the ITER Central Team and the domestic agencies. Component design is
now finalized, and a new optimized resource-loaded schedule has been developed to minimize the time to
first plasma. Since 2016, all scheduled project milestones have been achieved on schedule. The recently
revised ITER Research Plan19 has a first plasma in 2025, first scientific experiments in 2028, and a firstburning plasma experiment with deuterium and tritium fuel in 2035. The ITER Organization now has ateam of over 800 people, of which 5.5% come from the United States, with many thousands working on
the construction site and in the globally distributed supply chain.
The external structure surrounding the tokamak is now largely complete, as is the assembly hallstanding 60 m tall and with a crane lifting capacity of 1500 metric tons. The ITER cryo-plant will be thelargest single platform cryo-cooling facility in the world. It will distribute liquid helium to various
machine components, including the superconducting magnets, thermal shield, and divertor cryopumps.
The last of eighteen skids supporting the helium compressors was installed atop its massive four-meterhigh concrete pad in November 2017. The 400 kV switchyard to provide power from the grid has beensuccessfully installed and commissioned. Many ancillary heating and diagnostic buildings are now
erected and awaiting fit out.
A 12,000 m2 facility has been built to wind the largest poloidal field coils since they are too large
to be transported to the site. The first two poloidal field coils are now being wound and all thesuperconducting strand is now on-site. The 30 m x 30 m cryostat is being assembled on site andundergoing final welding. General Atomics has completed the first module of the 1000 metric ton central
solenoid, which will produce ITER’s highest magnetic field of 13 T. Besides initiating plasma current
within ITER, the currents in the six modules of the central solenoid will be independently controlled toshape and position the plasma.
The United States has committed to contributing 9.09% of ITER’s construction costs.
Participation in ITER in this fashion has resulted in significant advances in U.S. domestic industrial
capabilities and capacities, with the vast majority (approximately 80 percent) of U.S. ITER construction
funding remains within the U.S. supply chain.20 For example,

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The United States has proven its capability for fabricating superconductor in bulk, producing
over four miles of cable-in-conduit superconductor for the toroidal field magnets;
The United States is fabricating a first-of-a-kind 13 m tall, 13 T central solenoid
electromagnet, which is unique worldwide and has required the development of bespoke
fabrication and testing infrastructure;
United States industry is developing microwave and radio-frequency transmission lines toprovide unprecedented power transfer for heating in ITER;
High-throughput cryogenic pellet fueling systems and tritium processing systems have beendeveloped by U.S. national laboratories; andInstrumentation for the fusion nuclear environments has been developed.

In addition, the United States has been tasked with the research, design and fabrication of the AC
power system (delivered), the tokamak cooling water system, the vacuum pumping systems and thetokamak exhaust processing system. The United States has also been a key contributor toward theapproval of ITER’s license to start construction, by providing a “pedigreed” version of the fusionmodified safety code MELCOR, developed and maintained by the Fusion Safety Program at INL, which
has been used extensively for the safety analyses presented to the French Nuclear Regulator (Autorité deSureté Nucléaire) as part of the Construction Authorization Request.
According to the DOE project execution plan for ITER,21 the United States has “madeconsiderable progress in completing its assigned hardware design, R&D, and fabrication work.” Finaldesign of about two-thirds of U.S. hardware is complete, and two of thirteen in-kind hardware systems
have been delivered. A total of $942 million has been obligated by the U.S. ITER project with contracts
spread across U.S. industry, universities, and national laboratories, across 44 states.22 Approximately 50
U.S. personnel are working as members of the staff of the ITER International Organization (IO). Morethan one hundred full-time equivalents (FTEs) are working in the U.S. ITER Project Office, with most on
the central solenoid construction and tokamak cooling water system. It is anticipated that with full
funding, approximately 150 FTEs will be working in the U.S. ITER Project Office. The technicalleadership and contributions made by the U.S. fusion science team is and will continue to be important to
the eventual success of the ITER design, operation, diagnostics, and analyses. In addition, the U.S.
financial commitment is highly leveraged by the sharing of costs and technology with its international
partners. The performance of the United States in its ITER obligations has been very favorably assessedby the U.S. Government Accountability Office23 and DOE assessments and quality assurance audits
conducted in 2015.
The U.S. contribution to ITER construction is a prime driver for the U.S. fusion technology
program, and the United States is contributing a number of key systems that are both important for ITER
and for any future fusion power system. U.S. ITER participation has the effect of not only providing
leadership in the field of fusion technology, but also building capability in United States industry andcapacity to provide components for future fusion experiments and facilities. The United States has several
critical items to deliver for the completion of ITER construction and it should remain committed todelivering these key systems.
U.S. Research in Support of ITER Burning Plasma Science
The International Tokamak Physics Activity (ITPA) operates under the auspices of ITER, and the
ITPA provides an international framework for coordinated fusion research useful for all fusion programs
and for broad progress toward fusion energy. The United States continues to make significant
contributions to the ITPA, which coordinates the international tokamak physics research and development
activities and provides the physics basis for the ITER project. Presently, the United States chairs four ofthe seven ITPA Topical Working groups. The United States also actively participates in multiple-facility,
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joint tokamak experimental exercises. For example, joint experiments coordinated among MAST,ASDEX Upgrade, and DIII-D have recently evaluated the use of resonant magnetic field perturbations
and pellet injection to suppress edge localized modes (ELMs)24 leading to the introduction of ELM
control systems to be tested in ITER.
Ongoing advances in understanding burning plasma physics enable improvements in theprediction and optimization of ITER and in future burning plasma experiments. Progress has resulted by
combining physics-based dimensionless analysis with the development and validation of advanced
physics models using high-performance scientific computing. While this approach increases confidence in
ITER performance, the burning plasma regime is an extrapolation of fundamental underlying processes.
The normalized size of a burning plasma experiment is much larger than in existing devices, and this mayalter the confinement and stability properties. Heating and current sources, including the fusion alphaparticles that will heat a burning plasma, will involve new science. Finally, the boundary of the burning
plasma, where atomic physics and interaction with material surfaces become important, may lead to new
phenomena.
While addressing all these issues self-consistently awaits a burning plasma experiment, there are
numerous opportunities to establish the physics basis for optimal fusion performance. These include: (1)exploring plasma confinement physics expected in ITER, especially core plasma energy transport, plasmaedge pedestal physics, and the transition between low-confinement (L-mode) and high-confinement (Hmode), (2) exploring the strongly coupled physics of a burning plasma regime when fusion alpha particle
heating interacts with plasma transport and stability; (3) optimizing methods to control ITER plasmas toreach performance targets, maintain stability and avoid or mitigate transients and disruptions; and (4)further development and validation of plasma-material-interaction theory and simulation, leveraging
advanced computational techniques and next generation exascale computers.
Integrated understanding of the plasma core-edge integration with the materials science of thedivertor and first-wall is an ongoing research area that will benefit burning plasma experiments in ITER
and contribute to United States efforts toward an attractive compact fusion pilot plant. Because the coreand edge plasma are guided by different physics, bringing the two together in high fusion performance,
reactor-relevant scenarios represent a grand challenge of burning plasma science. Doing so will enablevalidation of theory and simulation in a reactor relevant physics regime, while qualifying exhaust
scenarios at relevant heat loads. Core-edge integration requires high plasma pressure in order tosimultaneously achieve the high particle density needed for attractive exhaust solutions, while
maintaining reactor-relevant low plasma collision rates. Experimental investigation of core-edge
integration will also need to address the conflicting needs for a cold, dense divertor to avoid material
erosion and, simultaneously, a hot, high power density core for high fusion performance. ITER will
provide a critical opportunity to explore a high-power density core at reactor-like dimensionlessparameters, combined with a tungsten divertor.
As United States fusion researchers approach and access frontier studies of the burning plasmastate, additional research topics provide opportunities for progress. These include:
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Disruption mitigation research, including development of prediction and avoidancealgorithms using passive and active control as well as mitigation (i.e. shattered pellet
Injection, SPI);
ELM control through pellet injection, applied external magnetic perturbations, natural ELMfree regimes;
Controlling heat exhaust through detached divertor and innovative divertor configurations
Development of ITER-relevant steady-state, non-inductive high-performance scenarios withacceptable divertor power loading;
Development of predictive computational tools within integrated simulations enabling
extrapolation to ITER regimes, including models for non-inductive current drive, core

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confinement, pedestal physics, core-edge coupling, energetic particle-induced instabilities,
plasma transient control, and plasma surface interactions;
Development of integrated frameworks for plasma control algorithm development;
Understanding material properties under the combined load condition and neutron loading
present in ITER with verification of models against irradiated samples from test reactors; andUnderstanding the redistribution and loss of energetic particles and how Alfvénic instabilities
can be mitigated in burning plasmas.
U.S. Contributions to Fusion Technology

Fusion technology advances have been driven by ITER research needs and by next-step goals to
fully enable the fusion energy system. ITER provides important experience for the critical development offusion technology and engineering needed in a fusion power device. Examples include: operation ofsuperconducting magnets, tritium handling systems, and tungsten divertor performance. Key
contributions from the U.S. fusion technology program involve the fusion fuel cycle, fusion materials,
fusion materials modeling,25 fusion plasma power handling, superconducting magnets, and liquid metals.
These contributions have resulted from joint international projects in support of ITER and from tasks
directed by U.S. researchers. Examples include vacuum and gas species management,26,27 tritium fusion
fuel cycle development,28 pellet injection for fueling and disruption mitigation,29 and the manufacture of
the ITER central solenoid.30 The capabilities of the United States pellet injection technology will be usedin future fusion experiments at the JET device (see Figure 3.1).
Many of the program advancements in fusion technology and engineering science in the UnitedStates are coordinated with the Virtual Laboratory for Technology (VLT). The VLT functions as a“virtual” laboratory with many collaborating institutions within the United States, including eight
universities, nine national laboratories, and one private company.31 The VLT facilitates fusion technology
and engineering science in the United States by (1) developing the enabling technology for existing andnext-step experimental devices, (2) exploring and understanding key materials and technology feasibility
issues for attractive fusion power sources, and (3) conducting advanced design studies that provide
integrated solutions for next-step and future fusion devices and call attention to research opportunities in
the field.32 As was described in Chapter 2, the United States has also advanced the science of high-powerplasma-material interactions using linear plasma simulators.
Preparing for ITER’s Scientific Mission
Research preparation for ITER’s scientific mission has focused on science and technology needed
to extend ITER operation for long pulse durations and to provide safe, reliable operation of the machine
for long duration pulses. Research results in support of ITER’s scientific mission also support thescientific missions of fusion energy facilities that will follow ITER. Three active research areas are:controlling the high heat flux on the divertor, preventing or minimizing transient edge instabilities that
could damage the divertor armor, and preventing or mitigating an uncontrolled loss of plasma
confinement, called a plasma current disruption, that could damage the first wall or the vessel structure.
Significant progress in all three of these areas were described in Chapter 2.

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FIGURE 3.1 Shattered pellet injection components for ITER's disruption mitigation system were tested first at
ORNL before shipment to the UK's JET tokamak for further testing. Photo courtesy: U.S. ITER/ORNL. For thisJET application, the ORNL injector is compatible for operation with tritium.

The large heat flux to the divertor is determined, in part, by the width of the channel in which hot
plasma escapes the confined plasma region and is directed to the divertor region. The ITER design canaccommodate a peak heat flux of 10 MW/m2. This heat flux is achieved by operating the divertor in a“detached” or “partially detached” state where the majority of the escaping plasma heat flux is radiated byrecycling neutral atoms in the diverter region. Detached divertors have been achieved on a number ofdevices worldwide, and the science of the escaping plasma heat flux continues to be an active area of
research.33,34
The baseline operating scenario for ITER is high-confinement (H-mode) with a strong edgetransport barrier and high pedestal pressure. The steep pressure gradient at the H-mode pedestal candestabilize Edge Localized Modes (ELMs). However, experiments on a number of devices worldwide
have demonstrated that it is possible to suppress or mitigate the effects of these ELMs by either applying
non-axisymmetric magnetic fields locally to the plasma edge, or injecting small pellets at high-frequency.
These control schemes are now included in the ITER design.
Finally, ITER will have the largest plasma current ever produced in a magnetic confinement
device, and an unmitigated plasma current disruption has the potential to significantly damage first-wallcomponents and divertor armor. To mitigate the effects of disruptions, ITER is planning to use massive
injection of gases and injection of shattered pellets to provide injection of a substantially larger volume ofparticles than is in the fuel, which will radiate the stored energy across all of the material surfaces, thereby
mitigating any risk of damage. These techniques to mitigate disruptions have been demonstrated, notably
in DIII-D, and will soon be tested in JET using the Shattered Pellet Injector (SPI) anticipated for ITER
(see Section II.1.b). Following a recent disruption mitigation workshop,35 the U.S. is actively participating
in an ITER Disruption Task Force and exploring even more effective techniques for disruption mitigation.
EXTENDING ITER PERFORMANCE
Recent advances in validated theory and simulation provide opportunities to significantly extend
ITER performance, including higher fusion power gain, longer plasma duration, demonstration ofadvanced operating scenarios, and improvements in divertor power handling. Simulations of integrated
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ITER
DIII-D Super H
DIII-D H
C-Mod Super H
C-Mod HJET H
NSTX

TFTR LNSTX H

FIGURE 3.2 Metric of fusion performance based on the product of volume averaged pressure (<p>)
and stored energy (W) divided by the product of heating power (Ph), current (I), minor radius (a) andmagnetic field (B), is plotted in units of kPa MJ / MW MA m T. Experiments on DIII-D and Alcator CMod have sustained values of this metric sufficient for ITER to meet its goals and have briefly achieved
higher values (red symbols) yielding enhanced ITER performance. SOURCE: Adapted from Snyder etal., “High Fusion Performance in Super H-Mode Experiments on Alcator C-Mod and DIII-D,” 27th
IAEA Fusion Energy Conference, Paper EX/2-4 (2018).

core-pedestal performance have already been used to optimize steady-state scenarios on DIII-D36 andmake initial predictions for ITER.37 New high-performance regimes such as Super H-Mode have been
predicted first, and later experimentally confirmed. These optimized regimes resulted in the highest
plasma pedestal pressure (pped ~ 80 kPa) ever achieved in a magnetic fusion device using the Alcator CMod tokamak,38 and the demonstration of the highest value of peak fusion gain, (Qequiv ~ 0.5), everachieved on a medium-scale (R < 2 m) tokamak by operating with advanced scenarios on DIII-D.39 These
achievements are summarized in Figure 3.2.40
Existing medium-scale and large-scale fusion experiment have achieved performance levels
consistent with ITER’s goals and have briefly achieved normalized performance levels that would enable
ITER to exceed its fusion performance goals. These might allow high fusion power gain (Q ~ 10) at lower
plasma currents and fusion ignition, or near ignition, which corresponds to achieving both high plasma
confinement and high fusion power. Achieving and sustaining these levels of performance in ITER would
represent a significant development toward smaller, less costly, compact fusion power systems. Figure 3.2
highlights these achievements using two metrics of fusion performance: the plasma pedestal pressure anda new metric motivated by recent advances in simulation <p>W/PhIaB. This is a metric of fusion
performance based on the product of volume averaged pressure (<p>) and stored energy (W) divided by
the product of heating power (Ph), plasma current (I), minor radius (a) and magnetic field (B), and isplotted in units of kPa MJ / MW MA m T. The normalized plasma pressure is βN; the average plasmapressure is given by <p> (Pa) = 4000 βN (B I/a); and the plasma energy confinement time is W/Ph. In thisway, the fusion performance parameter, <p>W/PhIaB, measures both high plasma pressure and highplasma confinement relative to the provided plasma current, field and minor radius. High performance has
also been demonstrated relative to empirical H-mode confinement scalings.41
Existing devices such as DIII-D and NSTX-U provide opportunities to address key science that
may extend the fusion performance in ITER. These include continuous operation while avoiding
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transients, maximizing normalized core performance at high bootstrap fraction, and developing exhaust
solutions. Collaborations with the European JET experiment on the planned D-T campaign should provevery valuable for validating physics models in high performance core plasmas consistent with an ITERlike beryllium wall and tungsten divertor. Collaborations with EAST and KSTAR, and in the future JT60SA, enable model testing in long pulse mode. JT-60SA in particular provides a compelling opportunity
to test model predictions made in advance of an experiment, as will be necessary in ITER. US-developedmodels such as EPED and TGLF have been applied in initial predictive studies of JT-60SA, and thesemodels, coupled to others, can be applied in comprehensive predictions of performance and performance
optimization in JT-60SA, which can then be tested as the machine enters high power operation.
Improvements in high performance computing hardware and algorithms, including the advent of
exascale computing, also provide an opportunity to extend the fusion performance of ITER. During thenext few years, advanced scientific simulations will be able to incorporate higher resolution time andspace scales and explore the complex couplings between electrons, ions, and global collective plasma
physics. Advances in analytic theory, including development of new formalisms capable of efficiently
treating the full range of scales associated with both magnetohydrodynamics and gyrokinetics, will lead to
improved study of the boundary plasma where equilibrium and turbulence scales overlap. A
comprehensive theory and simulation program including high fidelity multi-scale simulations, reduced
models incorporating insight from those simulations, and very fast neural net interpolations of more
complex models will enable theoretical understanding to be involved in all aspects from experimental
planning, to control, design and optimization of the fusion concept. Integrated simulation, moving toward
whole device modeling by connecting physics models from the core to the pedestal, boundary, andmaterial interface, provides a timely opportunity for comprehensive planning of burning plasma
experiments on ITER.
Continued physics model development and validation using the results from United States
facilities, DIII-D, NSTX-U, and the international experiments will further increase confidence in ITER
predictions. Additionally, experiments using U.S. facilities can develop advanced scenarios, closely
guided by validated models, to enable high fusion performance in both inductive and steady-state
scenarios. In particular, advanced scenarios, such as the “Super H-mode,” are expected to be achievableon ITER42 and lead to important studies of enhanced fusion performance in ITER and improved
confidence in the design of the compact pilot plant.
The United States has also contributed to the development of steady-state scenarios, where theplasma current is largely self-driven, through the “bootstrap” effect, and does not rely on inductively
driven current. A strong focus on high performance steady-state scenarios on ITER will also advanceunderstanding of the high-performance steady-state plasma, where the heating source (primarily fusion
produced alpha particles) and current drive (primarily pressure-driven bootstrap current) are both strongly
coupled to confinement and energetic particle physics.
Understanding Plasma Confinement at the Scale of a Power Plant
The move from existing fusion experiments to experiments at the scale of a power plant, like
ITER, brings important changes to the underlying plasma and atomic physics. The ratio of the ion
gyroradius to the device size, called ρ*, will be much smaller than on existing devices. This is true
because the reactor’s minor radius, a, is larger, the magnetic field is relatively stronger, and thegyroradius decreases with magnetic field. Numerous physical processes in both the core and edge plasma
are expected to have important dependencies on ρ*, and in some cases these dependencies are still not
well understood.
In addition, a fusion device at the scale of a power plant is influenced by the atomic processes
associated with the fueling and penetration of neutral particles at the plasma edge. In existing magnetic
confinement experiments, the neutrals penetrate a significant distance into the pedestal region of theconfined plasma, and the pedestal region is directly fueled by recycling neutral atoms, which are ionized
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upon penetrating into the plasma. This neutral penetration depth relative to the width of the pedestal isdenoted by λ*, which scales roughly in proportion to the inverse product of plasma density and plasma
size. However, the large scale and relatively high density of a device like ITER prevent neutral
penetration into the pedestal region. The study and understanding of plasma confinement processes underconditions of small ρ*, short neutral penetration depth λ*, and high plasma pressure and fusion power
density is a scientific frontier of burning plasma research.
Pedestal Physics at the Power Plant Scale
High confinement regimes are necessary for high fusion gain in ITER and in compact fusion pilot
plants. These regimes are characterized by stabilization of plasma turbulence and radial shear of theplasma flow near the pedestal. The increased plasma confinement associated with the high-confinement
operating mode, called the “H-mode,” occurs when the plasma shear flow is self-generated near the edge
pedestal region. How the turbulence suppression and plasma confinement properties scale with decreasing
ρ* is an important question to answer at the scale of a fusion power plant. Because the plasma flow shear
stabilization takes place across a region which scales with the turbulent eddy size, there is no significant
ρ* scaling of the pedestal width in front-propagation paradigm. To date, observations on existing devices
in carefully controlled dimensionless experiments have found no significant ρ* scaling of the pedestal
width.43 However, it remains to be learned whether ρ* physics may enter at very small ρ* values which
may impact the pedestal pressure in ITER and other future fusion power devices. Ongoing model tests on
existing devices,44,45 particularly at higher field, can shed light on this and further extend comparisonssuch as that shown in Figure 2.2(b). Detailed testing of physics models in the early stages of ITER
operation should improve understanding before entering the burning plasma phase of ITER. The role ofdirect fueling by neutrals in determining the pedestal density and density profile also plays an importantrole. An ongoing series of high-density experiments on DIII-D is currently exploring this physics, andexperiments on ITER will provide critical data.
Predicting the L-H Transition
The physics associated with the initial formation of the edge transport barrier (known as the “lowto-high” or L-H transition) remains poorly understood. Empirical scaling of the heating power required
for the transition suggests high power will be needed in an ITER-scale device because the needed L-H
power is observed to increase strongly with magnetic field, density, and plasma surface area at an aspectratio of A ~ 3. Being able to predict the L-H power threshold precisely is important for development ofhigh-performance scenarios on ITER. Both the empirical scaling and some proposed physics models,such as those that include the role of ion orbit loss,46 suggest ρ* scaling. In addition, changes in fuelingand recycling, such as divertor leg length, have been observed to affect the L-H transition, suggesting arole for neutral penetration physics. Results from NSTX suggest a possible collisionality dependence.
Three-dimensional (3D) fields, such as those ITER plans to use to control ELMs, also are known to
impact the L-H transition. Ongoing studies on existing devices such as DIII-D and NSTX-U can further
explore the role of geometry, fueling and 3D fields on the L-H transition. The early operation phase of
ITER, including operation at reduced field to reduce the L-H threshold power, will provide valuable data
to further develop physics understanding, and burning plasma experiments on ITER will address L-H
transition physics at high power density and reactor-like physics parameters.

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Power exhaust width (mm)C-Mod

FIGURE 3.3 Observations of the power exhaust width (SOL) decreasing as the inverse of the poloidal
magnetic field, Bp ∝AB/q. Adapted from T. Eich et al, "Scaling of the tokamak near the scrape-off
layer H-mode power width and implications for ITER," 2013 Nucl. Fusion 53 09303, with the additionof recent plasma simulation results showing the electron-scale turbulence will widen the power exhaust
width in ITER, from C.S. Chang et al, "Gyrokinetic projection of the divertor heat-flux width frompresent tokamaks to ITER," 2017 Nucl. Fusion 57 116023.

Understanding the Plasma Power Exhaust Width
As heat leaves the confined plasma it is quickly lost to the divertor across a narrow layer known
as the scrape-off-layer width, λq. As shown in Figure 3.3, observations of the scrape-off-layer widthshows that it scales inversely with the poloidal magnetic field, or λq ∝ q/AB, where q is the plasma safety
factor (inversely proportional to the twist rate of the magnetic field), A is the plasma aspect ratio, and B is
the magnetic field strength. At high q or low magnetic field, λq is wide and spreads the escaping plasma
heat across a wider surface within the divertor. In contrast, at low q or higher magnetic field, λq becomesnarrow and the peak power dissipation in the divertor region increase. Empirical scaling of λq suggests it
narrows with increasing poloidal magnetic field, and may therefore be very small, as small as 1 mm in
ITER.47 Physics models based on drift scaling also predict narrow λq for ITER.48,49 However, physics
models incorporating micro-instabilities suggest that as ρ* gets smaller, gradients across the scrape-offlayer will become high, strongly driving turbulence which transports heat radially, broadening λq.50,51
These models predict much larger values of λq ~ 5 to 8 mm for ITER. A similar broadening is predicted
for high plasma current (2 MA) NSTX-U plasmas, and validation of these calculations on both NSTX-U
and ITER can lead to a full understanding of this important physics at reactor scale.
Core Heat, Particle, Momentum and Impurity Transport
In the plasma core, the competition between turbulent and neoclassical transport is expected to bestrongly affected by ρ*. In particular, transport of high Z impurities such as tungsten are often dominated
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by the neoclassical pinch in existing devices, but turbulent transport is predicted to play a much more
important role in ITER.52,53 ITER is also expected to operate much closer to the critical gradient for
micro-instabilities which has important effects requiring large scale, long duration simulations to
explore.54 Low ρ* is also predicted to weaken coupling between equilibrium and turbulent eddy scales,making transport more local. The physics of momentum transport, and the mechanism for generation of
so-called intrinsic rotation, are relatively poorly understood, and ITER results at low ρ* and low injected
torque will clarify important physics. In addition, ITER will operate with a variety of hydrogen isotopes,
including protium, deuterium, and tritium, and so will provide important data on the isotope effect ontransport.
Density Limit
Tokamaks are observed empirically to encounter a density limit that scales roughly with the ratioof the plasma current to the square of the minor radius.55 The physics mechanism for this density limit is
not well understood, though a number of theories have been proposed, such as the radiative island
theory.56 On existing devices, the plasma density limit is also associated with high collisionality in theplasma edge. However, at the high pressure expected in ITER, it should be possible to encounter thedensity limit at low collisionality, providing insight on the role of plasma collisionality in density limits.
This physics is very important for ITER and reactor performance, because state-of-the art performanceprojections predict that fusion performance increases with density even to densities above the empiricallimit observed in present devices.
Alpha Particle Transport
Fusion plasmas contain energetic ions created by fusion reactions in the plasma. In present
devices, energetic ions can be produced by injecting beams of high-energy neutrals into the plasma that,after ionization, subsequently heat it; alternatively, radio frequency waves accelerate an energetic ion
population. In a fusion power device, fusion reactions between deuterium and tritium produce energeticalpha particles (also known as the nuclei of helium gas) at 3.5 MeV. The alpha particles are trapped
within the plasma and heat the plasma and sustain its temperature. Besides heating the plasma, theenergetic ions may drive instabilities that degrade their confinement. At their worst, alpha-particle
instabilities may cause beams of energetic ions to be lost to the first wall and erode wall materials. Figure
3.4 illustrates the orbit of an energetic ion in the DIII-D device that resonates with a 115 kHz Alfvén
eigenmode. Even if the ions remain in the plasma, their radial redistribution can degrade plasma
performance. Near-term research concentrates on acquiring the ability to predict which instabilities will
be unstable, the non-linear coupling among multiple simultaneous modes, what their consequences willbe, and developing methods to mitigate adverse consequences. Reduced models and high-fidelity physics
simulations using high-power computing play a key role. Development of simpler models that are lessexpensive computationally enable efficient prediction and model validation. Experiments on both DIII-D
and NSTX-U will help to validate these simulations. Experiments on ITER are a vital step in developing
confidence in these projections at reactor scale. One difference between ITER and present-day devices isthat the energetic-particle orbit is a smaller fraction of the machine radius. This is predicted to change thespectrum of unstable waves, which may alter their saturation mechanism. Using neutral beams, thesepredictions can be tested in the non-nuclear phase.
A major goal of ITER is to study the behavior of alpha particles, for the first time, in plasmas
with dominant fusion-product heating. The plasma will be a highly coupled, nonlinear system, as changes
in alpha confinement will alter the heating profile which may, in turn, alter the production of alphaparticles. High power deuterium-tritium experiments in ITER constitute a crucial experimental test of ourability to predict alpha-particle behavior in a power plant.

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FIGURE 3.4 The evolution of an ion interacting with an Alfvén eigenmode as measured in the DIII-D
tokamak. In (a), an ion trajectory is shown in resonances with the spatial and temporal structure of the
global Alfvén eigenmode. The interaction leads to a large displacement of the resonant ion, andeventually the ion ends at a location marked x, where a sensor detects it outside the plasma. Power
spectra from fluctuations of (b) energetic-ion losses and (c) plasma density measured reveal peaks at
the eigenmode frequency of 115 kHz. SOURCE: David Pace, W.W. Heidbrink, and M.A. Van
Zeeland, “Keeping fusion plasmas hot,” Phys Today 68, 34 (2015).

Exploring and Controlling a Burning Plasma
A burning plasma is a highly coupled, nonlinear system. The energy and momentum that alphaparticles provide to the plasma will affect the plasma current, transport, and stability in a manner that willalter the density and temperature of the burning fuel, which, in turn, changes the rate of fusion reactions.
Achieving and controlling the burning plasma state involves understanding these internal nonlinear
couplings and the self-organized plasma configuration resulting from self-heating. A burning plasma isfundamentally different from plasmas that have been created in all research facilities to date, and ITER
will provide the first opportunities to study, sustain, and control a burning plasma.
In preparation for ITER experiments, many techniques to control the coupled plasma state can be
explored beforehand. Couplings between the current profile, transport properties, and macroscopic
stability are already operative in existing experiments. In general, plasma control hinges on threeelements: sensors that measure the plasma state, actuators that alter the plasma state, and algorithms that
direct the actuator response to the sensor input. In the case of plasma control, the goal is often to suppress
an instability or, if that is not possible, to mitigate its impact. Instabilities that can damage the first wall of
the plasma chamber include plasma current disruptions, edge localized modes (ELMs), neoclassicaltearing modes (NTM), and Alfvén eigenmodes. Exploration of these instabilities benefit from thedevelopment of new sensors and instrumentation that can be operated in the radiation environment of a
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burning plasma, testing of control actuators, such as localized microwave heating, and the development of
new control algorithms and real-time control systems.
DEVELOPING AN ALTERNATE APPROACH WITHOUT ITER PARTICIPATION
Previous sections of this chapter describe the importance of burning plasma research, explain why
continued participation as an ITER partner is important to United States fusion energy research, anddescribe how ITER participation will inform the design of a compact fusion pilot plant as a new elementof the United States magnetic fusion program. The benefits of continued U.S. participation in ITER arecompelling. Planning and preparation for ITER experiments are the major focus of the U.S. fusion
research program. The development of national expertise in burning plasma science requires theparticipation of experts and will not result from mere study of the research achievements of other nations.
ITER construction is more than half complete, and the first plasma experiments are expected to begin inless than ten years. ITER is the only existing experiment with a mission to explore burning plasma
physics at the power plant scale. ITER is also an ambitious research project that integrates multiple
advanced technologies and combines the scientific and engineering expertise, industrial capacity, andfinancial resources of several nations. As an ITER partner, the United States receives full benefit from thetechnology that will establish the feasibility of fusion while providing only a fraction of the financial
resources.
Even though ITER is recognized as “the best candidate today to demonstrate sustained burning
plasma,” the committee was tasked to provide long-term guidance for the scenario in which the UnitedStates is not a partner in ITER. Because any strategy to develop magnetic fusion energy requires study ofa burning plasma, a decision by the United States to withdraw from the ITER project would require a new
approach to study a burning plasma and a new focus to the U.S. fusion research program. Currently, there
is no mature burning plasma experiment as an alternative to ITER. The design, construction, and licensingof such an alternative to ITER would require significant development by the U.S. program. Because
participation in ITER and the ITPA aids international cooperation and collaboration in fusion energy
science, withdrawal from the ITER project will also require a new approach to avoid isolation from theinternational fusion energy research effort.
Irrespective of whether the U.S. remains an ITER partner, the committee recommends the UnitedStates should start a national program of accompanying research and technology leading to theconstruction of a compact pilot plant at the lowest possible capital cost and the production of electricity
from fusion. In this way, the committee’s long-term strategic guidance is generic and applies to bothscenarios.
All previous strategic plans reviewed by the committee calls for construction and operation of aburning plasma experiment and the demonstration of scientific and technical feasibility prior toconstruction of a facility capable of electricity production. This committee concurs with this assessment.
A burning plasma experiment is a critical next step toward the realization of fusion energy, and thescience and technology gained from a burning plasma experiment, like ITER, will answer key questions
needed to design a compact pilot-plant. With access to a burning plasma experiment, scientists will havethe means to answer fundamental questions pertaining to energetic alpha particles created by fusion
reactions, plasma transport processes in fusion reactor conditions, methods to control of plasma transients,
divertor science, and the integrated scenarios that simultaneously test the requirements for stability,
confinement, fuel purity, and compatibility with plasma-facing components needed for a fusion energy
source.
If the United States wishes to maintain scientific and technical leadership in fusion energy
development and undertake a program toward a compact pilot plant, national expertise in burning plasma
science needs to be developed through hands-on operational participation and scientific study by U.S.
fusion scientists.

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For the scenario with the United States remaining an ITER partner, research toward the second
goal of compact, attractive fusion power generation will build upon the ITER experience and focus onhigh power density plasmas, and the integration of core and edge physics in the regime required for acompact fusion pilot plant. Using research results from the DIII-D, NSTX-U and Alcator C-Mod
programs, from advances in fusion confinement theory and simulation, a follow-on experiment as anintermediate step toward a high-pressure, compact pilot plant need not be a fusion nuclear facility,
resulting in significant savings in facility cost, research access, instrumentation, and project schedule.
However, if the United States were to withdraw from ITER, the United States would need todesign and construct a larger and more ambitious research facility with a capability to explore burning
plasma science with deuterium-tritium operation. The direct study of high-gain burning plasma physics
and access to research opportunities necessary to evaluate long plasma duration and burning plasma
control methods are central long-term goals of the United States program. As an alternative to ITER, theaddition of an expanded fusion nuclear program for the high-power density burning plasma facility would
very be expensive for the United States to undertake without international support, and it would delay
progress in the field.57 Such an expanded fusion research program, however, would be critical for directly
addressing the physics of a strongly coupled burning plasma, and addressing the key challenges discussed
above.
A decision by the United States to withdraw from the ITER partnership would make international
collaboration more difficult. Nevertheless, the United States would need to explore other avenues forcollaboration and international cost-sharing, such as the engagement of the U.S. in the physics design for
the China Fusion Energy Test Reactor (CFETR). Such international collaborations, particularly in theevent of a United States withdrawal from ITER, would benefit the United States provided a vibrantnational fusion program can provide value to offer to other collaborating nations.
In summary, in both scenarios, whether the U.S. remains an ITER partner, or not, the committee
recommends the United States should start a national research and technology program leading to theconstruction of a compact pilot plant at the lowest possible capital cost. However, without ITER
participation and since the long-term objective would still be the compact pilot plant, the primary initial
focus of a United States program would be a high-power density research tokamak with expanded
capabilities allowing study and operational experience with a burning plasma. Systems engineering andconceptual design studies for this machine, building on results from new experiments on DIII-D and
NSTX-U, and state-of-the art theory and simulation, should begin as quickly as possible in response to a
United States decision to withdraw from ITER in order to provide the necessary means to study burning
plasma science and technology as part of a new focus to the United States fusion research program andmaintain progress toward the long-term development of commercial fusion power.
SUMMARY
Major advances in both experimental and theoretical fusion science provide a strong foundation
for rapid progress toward fusion development. Progress in theory and computation of fusion plasmas,
coupled to well-diagnosed flexible US experiments, have increased confidence in predictions of burning
plasma performance, and clarified requirements for an attractive fusion energy source. Realization of aburning plasma is essential to developing a complete understanding of the strongly coupled system, andadvancing the technology needed to make fusion energy attractive.
ITER is a burning plasma experiment and the critical next step in the development of fusionenergy. Methods to control plasma stability, plasma interactions with first wall materials, plasma
confinement, and fusion power output will be tested. Theoretical predictions of energetic particles
produced by fusion reactions and methods to sustain a burning plasma will be explored and validated.
Equally important are gains in fusion engineering science and industrial capability that result from ITER
fabrication and operation.

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Finding: The scientific and technical benefits from the study and operation of ITER arecompelling and critical to the development fusion energy for the United States.
ITER is a large and ambitious project that integrates multiple advanced technologies andcombines the scientific and engineering expertise, industrial capacity, and financial resources of several
nations. As an ITER partner, the United States receives full benefit from the technology that will establish
the feasibility of fusion while providing only a fraction of the financial resources.
Finding: ITER plays a central role in U.S. burning plasma research activities and is currently the
only existing project to create a burning plasma at the scale of a power plant. Because the ITER
partnership is the central focus in the large international effort to develop fusion energy, theUnited States significantly benefits from participation in the ITER partnership.
Recommendation: Because the scientific and technical benefits from ITER are compellingand because ITER is the only existing project to create a burning plasma at the scale of apower plant, the Committee recommends that the United States government fulfill its
commitment to construct and operate ITER as the primary experiment in the burning
plasma component of its long-term strategic plan for fusion energy.
Recommendation: A near-term focus of the U.S. DOE OFES research program should
maximize the scientific and technical benefits from its partnership in a burning plasma
experiment.
Finding: Advances in understanding toroidal magnetic confinement, plasma control, andintegrated solutions to whole-plasma optimization point to improvements beyond the ITER
baseline and show how careful design and simulation can be used to lower the cost and accelerate
fusion energy development.
Recommendation: In the longer-term, the U.S. DOE OFES research program should
encourage the development and testing of burning plasma scenarios on ITER that
contribute to reliable operation of a compact fusion pilot plant.
Finding: If the United States withdraws from the ITER project, the national research effort would
be significantly disrupted, United States researchers would be isolated from the international
effort, and any benefit from sharing the cost in critical burning plasma studies and fusion
demonstration would be eliminated.
Finding: Without ITER, the United States would need to design, license, and construct analternative means to gain experience creating and controlling an energy- producing burning
plasma. The scale of research facilities within the United States would be more costly. The
achievement of electricity production from fusion in the United States would be delayed.
Recommendation: Nevertheless, if the United States decides to withdraw from the ITER
project, the U.S. DOE OFES should initiate a plan to continue research that will lead
toward the construction of a compact fusion pilot plant. This should include theconstruction of an alternative means to study the burning plasma regime and an alternate
method to engage in the international effort in the pursuit of its long-term objective forfusion demonstration.

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NOTES
1. See previous studies listed in Appendix D and, for example, National Research Council. 2004.
Burning Plasma: Bringing a Star to Earth. Washington, DC: The National Academies Press.
https://doi.org/10.17226/10816.
2. Goldston, “Heuristic drift-based model of the power scrape-off width in low-gas-puff H-mode
tokamaks,” Nuc Fusion 52, 013009 (2012).
3. Krasheninnikov, et al., “Edge and divertor plasma: detachment, stability, and plasma-wallinteractions,” Nuc Fusion 57, 102010 (2017).
4. Sawan and Abdou, “Physics and technology conditions for attaining tritium self-sufficiency for the
DT fuel cycle,” Fusion Eng and Design, 81, pp. 1131-1144 (2006).
5. Giancarli, et al., “Overview of the ITER TBM Program,” Fusion Eng and Design, 87, 395 (2012).
6. Girard, et al., “TER, safety and licensing,” Fusion Eng Des 82, 506 (2007).
7. Bornschein, et al., “Tritium management and safety issues in ITER and DEMO breedingblankets,” Fusion Eng Des 88, 466 (2013).
8. Raffray, et al., “High heat flux components-Readiness to proceed from near term fusion systems topower plants,” Fusion Eng and Design, 85, pp. 93-108 (2010).
9. Zinkle and Snead, “Designing Radiation Resistance in Materials for Fusion Energy,” Annu. Rev.
Mater. Res. 44, 241 (2014).
10. Burning Plasma: Bringing a Star to Earth, Burning Plasma Assessment Committee, National
Research Council (2004), http://www.nap.edu/catalog/10816.html.
11. Zinkle and Snead, “Designing Radiation Resistance in Materials for Fusion Energy,” Annu. Rev.
Mater. Res. 44, 241 (2014).
12. Burning Plasma: Bringing a Star to Earth, Burning Plasma Assessment Committee, National
Research Council (2004), http://www.nap.edu/catalog/10816.html.
13. Omori, et al., “Overview of the ITER EC H&CD system and its capabilities,” Fusion Eng and
Design, 86, pp. 951-954 (2011).
14. Cesario, et al., “Current drive at plasma densities required for thermonuclear reactors,” Nature
Comm, 1, 55 (2010).
15. Sauter, et al., “On the requirements to control neoclassical tearing modes in burning plasmas,”
Plasma Phys Control Fusion, 52, 025002 (2010).
16. Thumm, Manfred, “Recent Advances in the Worldwide Fusion Gyrotron Development,” IEEE
Trans Plasma Sci, 42, pp. 590-599 (2014).
17. Mitchell and Devred, “The ITER magnet system: configuration and construction status,” (inpress) Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.02.085.
18. See https://www.documentcloud.org/documents/1031934-2013-iter-managementassessment.html (2013)
19. ITER Organization, ITER Research Plan within the Staged Approach (ITR-18-003, 17
September 2018).
20. Sauthoff, N., “Perspectives from the US ITER Project,”, presented to the NAS Committee for a
Strategic Plan for U.S. Burning Plasma Research (August 29, 2017)21. Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, U.S.
DOE/OS/FES (January, 2017).
22. See slides 56-59, Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC60, U.S. DOE/OS/FES (January, 2017)
23. FUSION ENERGY: Actions Needed to Finalize Cost and Schedule Estimates for U.S.
Contributions to an International Experimental Reactor, U.S. GAO Report to Congress, GAO-14-499,
June 2014
24. Liu, Y., et al., Phys. Plasmas 24 056111 (2017)

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25. Wirth, Hammond, Krasheninnikov, and Maroudas, “Challenges and opportunities of modelingplasma's surface interactions in tungsten using high-performance computing,” J Nucl Mater 463, 30(2015).
26. Duckworth, et al., “Development and Demonstration of a Supercritical Helium-Cooled
Cryogenic Viscous Compressor Prototype for the ITER Vacuum System,” in Adv Cryogenic Eng, v. 57A
and 57B, pp. 1234-1242 (2012).
27. Perevezentsev, et al., “Study of Outgassing and Removal of Tritium from Metallic Construction
Materials of ITER Vacuum Vessel Components,” Fusion Sci and Technology, 72, pp. 1-16, (2017).
28. Klein, Poore, and Babineau, “Development of fusion fuel cycles: Large deviations from US
defense program systems,” Fusion Eng Des 1 (2015).
29. Lyttle, et al.,”Tritium Challenges and Plans for ITER Pellet Fueling and Disruption Mitigation
Systems,” Fusion Sci and Tech, 71, 251 (2017).
30. Libeyre, P.; Cormany, C.; Dolgetta, N.; et al., “Starting Manufacture of the ITER Central
Solenoid,” IEEE Trans on Applied Superc, 26, 4203305 (2016).
31. “Response to the NAS Committee for a Strategic Plan for U.S. Burning Plasma Research,” Phil
Ferguson, presented to the NAS Committee for a Strategic Plan for U.S. Burning Plasma Research(August 29, 2017). See also http://vlt.ornl.gov/.
32. Baker, Charles C., “An overview of enabling technology research in the United States,” Fusion
Engineering and Design, Volumes 61–62, November 2002, Pages 37-45.
33. Chen et al., “Progress towards modeling tokamak boundary plasma turbulence and understanding
its role in setting divertor heat flux widths,” Physics of Plasmas 25, 055905 (2018).
34. Chang, C.S., et al., Nucl. Fusion 57 116023 (2017).
35. Michael Lehnen and So Maruyama, ITER Disruption Mitigation Workshop (ITER HQ, 8–10
March 2017), ITR-18-002, 23 March 2018.
36. Park et al., “Integrated modeling of high normalized beta steady state scenario on DIII-D,” Phys
Plasmas 25 012506 (2018).
37. Meneghini et al., “Integrated fusion simulation with self-consistent core-pedestal coupling,” Phys
Plasmas 23 042507 (2016).
38. Hughes et al., “Access to pedestal pressure relevant to burning plasmas on the high magnetic
field tokamak Alcator C-Mod,” Nucl Fusion (accepted) 2018.
39. Solomon et al., “Exploration of the Super H-mode regime on DIII-D and potential advantages forburning plasma devices,” Phys Plasmas 23 056105 (2016).
40. Snyder et al., “High Fusion Performance in Super H-Mode Experiments on Alcator C-Mod andDIII-D,” 27th IAEA Fusion Energy Conference (2018).
41. Holcomb et al., “Steady state scenario development with elevated minimum safety factor on
DIII-D,” Nucl Fusion 54 093009 (2014).
42. Snyder et al., “Super H-Mode: theoretical prediction and initial observations of a new highperformance regime for tokamak operation,” Nucl Fusion 55 083026 (2015).
43. Beurskens et al., “H-Mode pedestal scaling in DIII-D, ASDEX Upgrade and JET,” Phys Plasmas
18 056120 (2011).
44. Kotschenreuther et al., "Pedestal transport in H-mode plasmas for fusion gain," Nucl. Fusion 57
064001 (2017); https://doi.org/10.1088/1741-4326/aa6416
45. Hatch, D.R., et al., "A gyrokinetic perspective on the JET-ILW pedestal," Nucl. Fusion 57
036020 (2017); https://doi.org/10.1088/1741-4326/aa51e1
46. Ku et al., “A fast low-to-high confinement mode bifurcation dynamics in the boundary-plasma
gyrokinetic code XGC1,” Phys. Plasmas 25 056107 (2018).
47. Eich et al., “Scaling of the tokamak near the scrape-off layer H-mode power width andimplications for ITER,” Nucl Fusion 53 093031 (2013).
48. Goldston, “Heuristic drift-based model of the power scrape-off width in low-gas-puff H-mode

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tokamaks,” Nucl Fusion 52 013009 (2012).
49. M. Kotschenreuther et al,"Pedestal transport in H-mode plasmas for fusion gain," 2017 Nucl.
Fusion 57 064001; https://doi.org/10.1088/1741-4326/aa6416
50. Chang et al., Gyrokinetic projection of the divertor heat-flux width from present tokamaks to
ITER,” Nucl Fusion 57 116023 (2017).
51. Chen et al., “Progress towards modeling tokamak boundary plasma turbulence and understanding
its role in setting divertor heat flux widths,” Physics of Plasmas 25, 055905 (2018).
52. Belli and Candy, “Impact of centrifugal drifts on ion turbulent transport,” Phys Plasmas 25 03201(2018).
53. Casson et al., “Theoretical description of heavy impurity transport and its application to themodeling of tungsten in JET and ASDEX upgrade,” Plasma Phys Control Fus 57 014031 (2015).
54. Staebler et al., “A model of the saturation of coupled electron and ion scale gyrokinetic
turbulence,” Nucl Fusion 57 066046 (2017).
55. Greenwald, “Density limits in toroidal plasmas,” Plasma Phys Control Fus 44 R27 (2002).
56. Gates et al., “Origin of tokamak density limit scalings,” Phys Rev Lett 108 165004 (2012).
57. The budget implications of the committee’s strategic guidance is discussed in Chapter 5 and in
Appendix H.

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4
Advancing Magnetic Fusion Toward an Economical Energy Source
While construction and operation of a burning plasma experiment is a critical next step to thedevelopment of magnetic fusion energy, further research is needed to improve and fully enable the fusion
power system. The interconnected science and technology for the hardware that surrounds the plasma,converts fusion power into useful heat, and breeds and recovers tritium will need to be developed for acommercial fusion power source. Additionally, research and innovations are needed to reduce the size andcost of the fusion power system and to attract industries and utilities to pursue fusion energy-based
electricity production for the United States.
This chapter describes the research needed to advance magnetic fusion toward an economicalenergy source beyond what will be conducted with ITER. It is motivated by recent science andtechnology achievements that make feasible a research strategy that may shorten the time and reduce thecost required to develop commercial fusion energy. Instead of following ITER experiments with a large,
and potentially costly demonstration fusion power plant (DEMO),1 research opportunities are describedfor a reduced cost pathway to fusion development. Industry can now produce commercial quantities ofhigh-temperature superconducting tapes that have the potential to be used in very high field fusion
magnets that will reduce the size needed to magnetically confine a burning plasma. Advanced burning
plasma operating scenarios have been investigated that may allow uninterrupted plasma confinement athigh fusion power density and with very low recirculating power requirements. Emerging newtechnologies have been identified, like additive and advanced manufacturing and novel tritium processing
technology, that may reduce the cost and improve the reliability of fusion nuclear components andsystems. Taken together, these advances create a new approach to the development of commercial fusionenergy, called the “compact fusion pilot plant.” The goal of a compact fusion pilot plant is to use
advances in fusion science and technology to address mission elements of previous pathways to a fusion
DEMO but in a facility having a small size and the lowest possible capital-cost.
This pathway to a compact fusion pilot plant merges fusion science and technology research withburning plasma studies conducted in parallel with ITER. This pathway converges in the time-frame after
burning plasma demonstration in ITER (near 2040) and enables the construction of a compact pilot plant
to begin near this time. When ITER operation establishes key burning plasma science and when theaccompanying research program has simultaneously advanced burning plasma science, materials science,fusion nuclear science, and engineering science, the design of the compact fusion pilot plant can befinalized and construction commence. As identified in the committee’s Interim Report, without the
research accompanying ITER aimed to improve and fully enable the fusion system, the United Statesrisks being overtaken as our partners advance the science and technology required to deliver fusionenergy.
Advancing magnetic fusion energy by developing a compact fusion pilot plant involves risks. A
compact fusion pilot plant requires developing operation scenarios for sustaining high-power density
burning plasma with the plasma exhaust capability required for compact fusion. The engineering design
and fabrication of large bore, high-field superconducting magnets for fusion needs to be established.
Long-lifetime materials will need to be developed and qualified for use in the compact fusion pilot plant.
Tritium science and fusion breeding blanket development needs to be developed sufficiently for
integrated non-nuclear testing of prototypes that can serve as the basis for blanket components that will
ultimately be installed in the compact pilot plant. Finally, to be successful, a detailed system engineering
effort is needed to guide a “pre-pilot-plant” research program toward construction of a low capital-cost
fusion pilot plant through cost-effective research and development. The only way to retire these risks is tocarry out the needed research and development.
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This chapter is organized into four parts. First, previous pathways to commercial fusion aresummarized, and the mission needs for commercial fusion power are listed. Second, the compact fusion
pathway is presented including the research needed to establish and sustain burning plasma conditions athigh power density, with low recirculating power, and using low-cost research facilities. Third, fusion
nuclear science and technology is discussed followed by description of a “pre-pilot-plant” research
program that will increase the technical readiness of the superconducting magnets, fusion nuclear
materials, fusion nuclear components, and enabling technologies that are needed to design and fabricate acompact fusion pilot plant. Possible facilities and partnerships that further accelerate magnetic fusionenergy are also described.
Finally, the committee’s findings and recommendations for a national program of accompanying
research and technology leading to the construction of a compact pilot-plant which produces electricity
from fusion at the lowest possible capital cost. A detailed finding itemizing the technical and scientificsupport motivating a new national research program leading to the construction of a compact pilot plant isfollowed by four recommendations to resolve five critical research needs, initiate planning for theconstruction of new research facilities, and the adoption of a two-phase approach to its plans for thecompact pilot plant so that scientific and technical risks can be addressed cost-effectively.
PREVIOUSLY STUDIED PATHWAYS TO COMMERCIAL FUSION ENERGY
The long-term objective of previous pathways to commercial fusion energy is the design andoperation of a demonstration fusion power plant (DEMO). A DEMO would produce electricity, operateroutinely and eliminate all technical barriers to the commercialization of fusion power. Previous designs
for a fusion DEMO are for large, high-power facilities that build upon the ITER design with technologies
needed to produce net electricity from fusion for long periods of time.
Two approaches have been proposed to reduce technical risks of a DEMO facility and to satisfy
fusion nuclear licensing requirements. One approach builds an intermediate facility, called a fusion
nuclear science facility (FNSF), prior to DEMO. An FNSF would establish the materials and component
database in the real fusion in-service environment before proceeding to a larger DEMO facility. The otherapproach would design and build a large DEMO facility with a “slow start” where necessary fusion
nuclear components would be installed over time in a staged approach.
Figure 4.1 illustrates the timelines for various pathways to DEMO and to a commercial fusion
power plant developed for Korea, Europe, Japan, and China and previously considered for the UnitedStates. All pathways have the same goal of operating a DEMO near 2050. The United States has not
adopted an official strategy toward a DEMO, but the U.S. DOE FESAC has recommended researchleading to the construction of an FNSF prior to DEMO.2,3 The FNSF would be the first part of a two-step
approach to a fusion power plant that would commence in parallel with the study of burning plasma in
ITER. The second step is a DEMO device. Variations of the FNSF differ in size and capability, but thestrategic argument for the FSNF is to understand the behaviors of materials and fusion components prior
to the pursuit of electricity production in the larger DEMO device. Several options for an FNSF have been
considered in the United States depending how closely the FNSF approaches the characteristics of apower-producing fusion energy device and that vary the shape of the magnets that confine the toroidal
burning plasma.4

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FIGURE 4.1 Timelines for the pathways to the first commercial power plant for the United States,
Korea, Europe, Japan, and China. All pathways have the same goal of operating a DEMO near 2050.
The fusion energy pathway for the United States is not determined, and proposals have been made toconstruct an intermediate FNSF prior to DEMO. The Korean and Chinese DEMO would be designed
and operated in two phases. For Japan and Europe, construction of DEMO would begin near the end of
ITER operation. SOURCE: Laila El-Guebaly, “Worldwide Timelines for Fusion Energy,” presented tothe committee (November 2017).

The pathways considered by Korea and China proceed directly from ITER to DEMO, but the
Korean and Chinese DEMO facilities would be designed and operated in two phases. Higher-power andlonger-duration fusion power would occur in the second phase after the first-phase established burning
plasma operating scenarios and some fusion nuclear technologies. For Japan and Europe, construction of
DEMO would begin near the end of ITER operation in order to start DEMO operation at the earliest
possible date.5 The EU fusion roadmap Horizon 20206 requires the EU-DEMO to be based on maturetechnologies and use reliable regimes of operation extrapolated from the ITER facility. All of thepathways listed in Figure 4.1 include a DEMO device built at a size and power level larger than ITER.
The various international pathways to commercial fusion energy address equivalent technicalresearch and development needs. In the United States, these research needs were most recently describedin the 2007 FESAC committee on Priorities, Gaps, and Opportunities7 and the 2009 report of U.S. DOE
Office of Science Research Needs Workshop for Magnetic Fusion Sciences.8 Scientific and technicalquestions were organized into three broad themes defined in terms of the knowledge required prior to
DEMO. These were:

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



Creating predictable high-performance steady-state plasmas sufficient to create and sustain aburning plasma meeting all of the conditions required for practical production of fusionenergy.
Taming the plasma-material interface sufficiently to design and build robust material
components that interface the hot plasma in the presence of energetic fusion neutrons.
Harnessing fusion power sufficiently to design and build reliable systems that convert fusionenergy to useful forms of energy and breed a self-sufficient supply of tritium fuel.

These reports recommended an integrated program of research to address all of the scientificchallenges of fusion energy including fusion engineering, materials science, and plasma physics.
As presented in Chapters 2 and 3, the world-wide focus on the construction and preparation forburning plasma experiments on ITER has resulted in significant progress in the first theme to create
predictable high-performance steady-state plasmas sufficient to create and sustain a burning plasma.
Important progress has also been made toward the second theme of plasma-materials interaction needed
to design and predict performance of the ITER divertor. Progress in the third research theme, the technicalreadiness to harness fusion power, is least well-developed. In a future nuclear fusion power facility,
virtually every major component will require novel materials compatible with fusion’s energetic neutron
production. Additionally, fusion nuclear components will need to safely and efficiently fuel, exhaust,
breed, confine, extract, and separate unprecedented quantities of tritium.9
The development path and technical missions to progress beyond ITER toward a commercial
fusion power plant were recently summarized based on a detailed system engineering study for an FNSF.
In addition to the study of burning plasma and control, the development of fusion technology is
categorized into three steps. Fusion-relevant neutron exposure of materials and non-nuclear testing of
fusion components are tests that can be prepared in the short term. The purpose of the second step, theFNSF, is to produce environments similar to a fusion power plant for evaluating heat removal and theimpact of energetic fusion neutrons. Integration of those systems related to electricity production,
including high efficiency heating, current-drive, thermal management, breeding, and gas processing, aredeferred to the last step, the large DEMO device.
For all of these development pathways, the long-term objective is the design and operation of ademonstration fusion power plant (DEMO). The pathways are distinguished by the number and size of
research facilities needed to achieve the integrated technical efficiency to produce electricity from fusionenergy.
A COMPACT AND LOWER-COST PATHWAY TO FUSION ELECTRICITY
New technologies, such as high-temperature superconducting magnets and advanced materials,
and new achievements in burning plasma science now make smaller, less-costly research devices possible
and fusion research and development more affordable and attractive. This has two strategic implications:

In place of a single-step approach to a large fusion demonstration facility (DEMO), theopportunity exists today to start the interconnected science and technology research leading
to construction of a compact pilot plant and, ultimately, the production of electricity with adevice with significantly lower cost.

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FIGURE 4.2 Illustration of the DEMO approach and the pilot plant approach to next-step fusion energy
development devices. On the left is a design of the K-DEMO capable of producing as much as 600 MW ofelectricity. On the right is a diagram of a smaller and less-costly pilot plant. While not producing as muchelectricity, a compact pilot plant would allow low-cost testing and development of the science and technology
for commercial fusion power. SOURCE: T. Brown, “U.S. Next Step Strategy for Magnetic Fusion,” submitted to
the U.S. Workshop on Strategy for Magnetic Fusion, Madison, WI, July 2017.



In place of two-step approach with a fusion nuclear science facility (FSNF) having a mission
limited to fusion component development followed by a second DEMO facility, recent
science and technology advances suggest a compact fusion pilot plant might be built at a costcomparable to previous FNSF designs while being ultimately capable of demonstrating theoverall systems efficiency required to produce electricity.

Relative to previous pathways to commercial fusion energy, a compact fusion pathway targets
smaller device size, lower capital cost, and shorter development steps. A research approach thatminimizes the capital cost of major research facilities is a less costly pathway to the demonstration offusion electricity. A research approach that includes the production of electricity as an objective
motivates, from the beginning, efforts to optimize overall systems efficiency as an essential part of theevaluation of the compact fusion pilot plant.
This compact fusion pilot plant would be a pre-commercial research facility with a burning
plasma at its core and surrounded by a blanket to capture fusion heat and neutrons. In addition to the
production of fusion electricity, the pilot plant would ultimately be capable of uninterrupted operation forweeks and produce tritium, the heavy isotope of hydrogen in fusion fuel, from lithium-containing
blankets that surround the plasma. As a pilot plant, its purpose will be learning, but the knowledge
obtained would be sufficient for the design of the first commercial fusion power systems..
The pilot plant pathway to commercial power has been examined favorably by several studies formany years.10 Figure 4.2 compares one DEMO design to an example of a pilot plant designed withsuperconducting magnets, B = 6T, small size, R = 4m, and relatively low fusion power, 500 MW.11 By
comparison, the K-DEMO (R = 6.8m, B = 7.4T) design would be much larger and costlier but produce
2000 MW of fusion power.12 Besides decreasing the cost of fusion research facilities, a smaller, compact
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fusion pilot plant addresses market trends from United States electrical utilities seeking lower capital-cost
capacity additions, shorter construction times, and more flexible siting options that result from smaller
power-plant footprint.13
Another advantage of a compact approach is that it reduces the financial risk in combing two
fusion research missions in a single device, provided that sufficient progress is made to retire technology
risks. The initial pilot plant operation would demonstrate net-electric equivalent performance in acompact fusion system, focusing on integrated core/edge performance, assessing plasma materialinteractions, demonstrating tritium pumping, limited breeding, safe handling and extraction. This initial
phase would not include long-pulse fusion power production and would not demonstrate self-sufficient
tritium production. The second phase of the pilot plant would seek near continuous operation, allow formaterials/component testing with neutron fluences approaching power-plant levels, and provide
integrated blanket testing. Upon success of this second phase, the compact fusion pilot plant studies
would have reduced both the economic and technical risks for fusion energy-based electricity production
and will motivate further involvement from industries and utilities in the United States.
The scientific and technical opportunities for developing a compact fusion pilot plant aredescribed below. The important relationship between compact size and high magnetic field is discussed
along with the engineering challenges associated with high-temperature superconducting magnets and theplasma science and materials science challenges associated with continuous operation and high-powerplasma exhaust. Fusion nuclear science and technology, opportunities for new research facilities, andopportunities for expanded international collaboration are also discussed further.
High-Magnetic Field Strength for Compact Fusion
The relationship between high magnetic field and compact fusion confinement has been
appreciated for decades.14,15 Fusion power density is proportional to the square of the plasma pressure,0.08 P2 (MW m-3), where P is the plasma pressure in atmospheres. Because the maximum achievable
plasma pressure increases in proportion to the magnetic pressure, fusion power density increases rapidly
with increasing magnetic field, in proportion to B4. Furthermore, the confinement time in a magnetizedplasma scales with the number of gyro-radii across the plasma. At fusion temperatures, this number scaleswith the product of the plasma size and the magnetic field, R×B. Thus, if the magnetic field doubles, thefusion power density can increase as much as 16-fold while maintaining the same fusion power gain at
half the size.
The magnet technology with the highest possible magnetic field generally determines the size ofmagnetic fusion devices. A smaller compact fusion power source becomes possible with the availabilityof higher field magnets provided the compatible plasma components can be developed to control, sustain,
and utilize the high-power density burning plasma.
Early compact magnetic fusion experiments were built with copper magnets, where highmagnetic field strength could be reached for short pulses using novel engineering to deal with very large
magnetic forces. The world’s record for volume-averaged plasma pressure was set in September 2016 in
the Alcator C-Mod device at the Massachusetts Institute of Technology, which operated at high magnetic
field and physics-based optimization. (See Figure 2.3.) Two of the three burning plasma experiments
discussed in the 2004 NAS Burning Plasma Assessment were designed with copper coils in order to reachburning plasma conditions during short pulses in devices that would be smaller, but less capable, than
ITER.
Copper coils require large currents and consume large power when operating at high magnetic
field. For this reason, continuous high-field operation for fusion is not possible with copper coils. All
power producing magnetic fusion concepts considered today require superconducting magnets to reduce
recirculating power and significantly improve the efficiency and economics of electricity production.16 At
the time ITER was designed, the highest-field superconductor available was niobium-tin (Nb3Sn). To
reach burning plasma conditions, the ITER superconducting magnets are the largest ever built, with a
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FIGURE 4.3 Diagrams of (a) fusion power and (b) magnet energy (within plasma volume) versus plasma major
radius for several next-step burning plasma devices including proposed DEMO reactors. Compact devices are
smaller and require superconducting magnet systems with lower magnet energy requirements. DEMO devices
proposed in China (CFETR), Korea (K-DEMO), Japan (JA-DEMO) and Europe (EU-DEMO) are larger than
ITER and require higher energy superconducting magnets. The ARC device, proposed by MIT, and the Fusion
Nuclear Science Facility (FNSF), developed in the United States, are compact next-step devices with lower cost.
SOURCE: Adapted from “Producing Electricity in a Fusion Nuclear Science Facility or Similar,” C. E. Kessel,
paper submitted to the committee, April 2018 and C.E. Kessel, et al., "The Fusion Nuclear Science Facility, theCritical Step in the Pathway to Fusion Energy," Fusion Sci Technol 68, 225 (2017).

total magnetic stored energy of 51 GJ, a nominal mechanical stress of 600 MPa, and a magnetic fieldstrength of B = 5.3 T within the plasma.17 Today’s opportunity for compact magnet fusion energy resultsfrom the potential for high-field superconducting magnets. New high-temperature superconductors may
make possible fusion magnets that can achieve fusion gain and power equivalent to ITER but at asignificantly lower size and cost.
Figure 4.3 illustrates the sizes for several proposed superconducting next-step burning plasma
devices at A ~ 3, including ITER. Various DEMO designs have magnetic fields comparable to ITER andachieve higher power at larger size. The large EU-DEMO device (R = 9 m) requires a system ofsuperconducting magnets having a magnet energy about four times larger than ITER. In contrast, recent
FNSF conceptual designs18 (which are not designed to achieve the same power gain as ITER) and the
proposed ARC device19 are much smaller fusion devices that operate with higher magnetic field strength
but smaller stored magnetic field energy than in ITER.
Two engineering challenges will need to be addressed to increase the magnetic field in a compact
fusion device. The first challenge is the development of superconductors with higher critical current
density and higher critical magnetic field strengths. With the new commercial availability of rare-earthbarium copper oxide superconducting materials deposited on steel tapes, the prospects for meeting thischallenge appear good. The second challenge is the mechanical design of the high field tokamak. At highmagnetic fields, the magnetic force becomes extremely large. Within larger devices, like ITER, thecentral force of each toroidal field magnet is supported by wedges between adjacent coils and includes alarge ohmic heating solenoid. The CFETR,20 EU-DEMO,21 K-DEMO,22 and J-DEMO23 designs listed in
Figure 4.3 are examples. By comparison, with a compact fusion device, innovative mechanicalconfigurations are needed to support the large forces on the superconducting magnets. The magnetic fieldstrength used for conceptual design studies of compact fusion devices are limited by the high stresses
within the materials needed to support the magnets.24 However, the FESAC Report on Transformative
Enabling Capabilities concluded (p. 28) a “consensus within the magnet community that existing high
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strength stainless steel and superalloy materials are adequate for projected fusion requirements.”
Additionally, smaller and higher-field designs incorporate multiple load paths, called bucked and wedged,
to support the magnet forces.25
In a fusion device built using superconductors, the field from the toroidal magnets does notchange in time. However, the poloidal field magnets that are used to start-up the burning plasma andcontrol its position and shape will need to change in time. The development of high-field superconductors
for the poloidal field coils require the solution of challenging technical issues related to time-varying
magnet currents. These engineering issues will influence the magnet configuration, aspect ratio, andlocation of poloidal field magnets within the device.
While new high-temperature superconductors require engineering developments to reach the highmagnetic field strength for compact fusion, they may provide additional benefits as compared to lowcritical temperature superconductors. For example, demountable toroidal field magnets may allow
simplified maintenance, as proposed in the ARC compact fusion device.26 Because the newsuperconductor is deposited in thin layers on flexible steel tapes, magnet winding and manufacturing may
be superior than the wind-and-react method required for Nb3Sn. Low aspect ratio compact design has
been proposed both in the United States27 and by Japanese scientists.28,29 In each case, size reduction
resulting from high-field compact tokamak reactors is significant when compared with conventional
reactor designs. Further mechanical design is required to assure adequate structural integrity andcompatibility with high fusion power density, a compact tritium breeding blanket, effective neutron andgamma shielding, and non-inductive operation.
Finding: Although additional research, including magnet engineering research, is needed todemonstrate the viability of the compact pathway to fusion power, the combination of new highfield superconducting magnet technology with advanced burning plasma science is a significant
opportunity to decrease the size and cost of a magnetic fusion power system.
Plasma Power Handing for Compact Fusion
Power handling is one of the crucial challenges for magnetic confinement fusion, and thecompact pathway to economical fusion path may either heighten or help to mitigate this challenge.
The escaping plasma exhaust that contacts the divertor will need to be configured to avoid
unacceptable thermal damage or erosion of plasma facing components due to sputtering. Compared withpresent-day devices, the escaping plasma heat flux will increase in commercial fusion power devices andrequire design improvements to properly cool the divertor and first-wall and allow continuous
uninterrupted operation. Additionally, plasma relaxation phenomena, called edge-localized modes(ELMs) driven by instabilities localized to the plasma edge region,30 should be controlled or prevented inorder to avoid first-wall material damage.
Variations of the divertor approach taken for ITER may also prove applicable for the compact
fusion pilot plant. The divertor is constructed from water cooled blocks with plasma-facing tungsten
armor. The very high heat flux from the plasma is prevented from direct contact with the divertor armor
by volumetric radiation and recombination, called a “detachment.” Uncertainties exist how divertor
detachment can be achieved in next-step fusion devices, and the results from ITER experiments will
provide crucial measurements with which to test predictive models. Nevertheless, the power flow of theescaping plasma exhaust is observed to be narrow, with a width inversely proportional to the poloidal
magnetic field, Bp ≈ B/Aq, where A is the plasma aspect ratio and q is the plasma safety factor (inversely
proportional to the helical twist of the magnetic field lines.) A fusion device with the same peak power
flux to the divertor as expected in ITER will require that the thermal power escaping the plasma surface
scale in proportion to RqA/B and likely also require seeding with impurity atoms (like argon, neon, orother radiating atoms) that scale in proportion to qA/B.31 Self-consistent models for detached divertors
indicate the impurity fraction required for detachment scales in proportion to the ratio of the escaping
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Permission Pending

FIGURE 4.4 Illustration of magnetic fusion operation as a function of the magnetic field strength, B, andtoroidal major radius, R. Three diagrams are shown with different assumptions of the confinement factor, H, thenormalized plasma pressure, βN, and plasma safety factor, q. The fusion power increases rapidly with both size
and magnetic field, ∝R3B4; the plasma current increases linearly, ∝RB/q; and the power flux to the divertor isassumed to scale as the product of the plasma thermal power and (B/Rq). As the size of the fusion power source
decreases (panel a), the magnetic field must increase. As the size of the fusion power source increases (panel c),
the fusion power output increases. Finally, when both the plasma pressure, βN, and safety factor, q, are sufficiently
large, about q× βN > 25, the plasma current is self-sustaining without external current drive power, as shown in(panel a). SOURCE: Adapted from H. Zohm et al, “A stepladder approach to a tokamak fusion power plant,”
2017 Nucl. Fusion 57 086002.

fusion power to the poloidal magnetic field. For this reason, a compact pilot plant operating at lower
power but higher magnetic field may be preferred to a higher-power fusion system because the compact
design allows lower impurity concentration within the detached divertor region.
As the magnetic field increases, the fusion device becomes more compact and produces less total
power at equivalent gain. Figure 4.4 illustrates these trends which show how the limits imposed by thedivertor heat flux and fusion power change as the magnetic field, B, and the device size, R, change while
keeping the aspect ratio at A ~ 3. Because the exhaustible heat is proportional to the plasma surface area
while the device cost is proportional to the magnetic energy within the plasma volume, a compact fusion
approach can be a cost-effective approach for magnetic confinement fusion from the power handlingpoint of view as well as by reducing total capital investment for a power plant.
Another challenge is controlling the transient heat flux due to ELMs (Edge Localized Modes).
ELMs are edge relaxation phenomena believed to be driven by the peeling/ballooning mode.32 Several
methods have been demonstrated to suppress ELMs, including the application of 3D magnetic
perturbations in DIII-D33 and steady operation without any transient ELM events. These include thequiescent “QH-mode”3435 associated with edge harmonic oscillation (EHO) to enhance edge transport, “Imode”36 associated with the weakly coherent mode (WCM), and improved energy confinement with
reduced particle confinement. Eliminating or reducing the transient heat flux due to ELMs significantly
lengthens the lifetime of the divertor armor. Because of the higher magnetic field of a compact fusion
reactor, operation can occur at reduced plasma current and higher q, which has been found to assist in
ELM-free operating modes.
Finally, ongoing research, discussed in Chapter 2, is now evaluating promising advanced divertor
configurations such as the Snowflake divertor,37 Super-X-divertor,38 and Small-Angle Slot (SAS)divertor.39 A recent low aspect ratio HTS FNSF/Pilot plant design by Menard40 successfully showed thatthe long-leg and Super-X-divertor can be implemented for the outboard divertor leg in a compact fusion
system. The SAS divertor, first tested in DIII-D, is a compact divertor geometry in which stable

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detachment has been obtained experimentally, showing that a slot with a V-shaped corner is very
promising for a compact fusion power source.
Finding: While methods to remove heat from the divertor and reduce material erosion due toplasma sputtering remain active research areas, current understanding of divertor scaling indicatesthat the compact fusion pathway at higher field and lower total power may benefit power
handling solutions for fusion energy.
Achieving Steady Uninterrupted Operation for Compact Fusion
A commercial fusion power source will need to produce electricity continuously for several
months at a time. A critical goal for a compact fusion pilot plant is to demonstrate uninterrupted operationand to establish the basic science and technology needed for commercial fusion power.
Figure 4.5 shows diagrams of fusion plasma performance and plasma pulse duration. The fusionenergy gain is roughly proportional to the fusion “triple product,” n(0)×E ×Ti(0) equal to the product of
the central plasma density, the characteristic time for energy loss, and the central temperature of thefusion fuel. The fusion gain and triple product generally increase quickly with the size and magnetic fieldstrength of the fusion containment device, n(0)×E ×Ti(0) ∝ (R B)3 at fusion temperatures and densities.
The highest fusion performance has so far been achieved using large copper magnets (e.g., the JT-60U,
JET, and TFTR experiments). In these devices, long-pulse operation requires reduced toroidal magnetic
field, resulting in reduced plasma performance. Studies of long duration plasma confinement has become
possible with superconducting magnets such as the Tore Supra (TS) ,41 EAST, and K-STAR experiments.
The longest plasma duration was achieved in TRIAM-1M,42 but TRIAM-1M could not simultaneously
achieve high fusion performance due to its small size, R = 0.84 m. Two superconducting stellarators, theW-7X (R = 5.5 m, B = 2.4T) and LHD device (R = 3.9 m, B = 3.0T), have, respectively, two and threetimes higher energy superconducting magnet systems than in the EAST tokamak, and they are sufficiently
large to allow study of fusion performance at pulse lengths comparable to the superconducting tokamaks.
As shown in Figure 4.4, the technical achievement of high fusion gain and long plasma duration will betested for more than one minute in the JT-60SA device,43 expected to be commissioned in 2010 in Japan,
and for several minutes in ITER and additional facilities, like FNSF, have been proposed to extend fusion
pulse lengths from days to weeks.
To achieve efficient steady-state operation, most of the plasma current will need to be selfgenerated instead of driven by injection of particles or electromagnetic waves. Indeed, the plasma current
in high-gain fusion experiments have been driven by magnetic induction, and the plasma current in thehighest performance experiments in ITER also results from induction.
Self-generated current is called “bootstrap current,” and the fraction of plasma current sustainedby the bootstrap effect scales in proportion to the plasma poloidal beta, p, where the plasma poloidal beta
measures the ratio of the plasma energy to the magnetic energy of the plasma current. The poloidal beta is
proportional to the normalized plasma beta and the plasma safety factor, p ≈ 0.03 q A βN. The highpoloidal beta regime occurs when q βN ~ 25 (when the plasma aspect ratio is near 3) and the selfgenerated bootstrap current fraction, fBS, reaches 100%. This mode of operation is called the advanced
tokamak operation.44 JT-60U45 sustained high bootstrap current fraction (~75%) discharges for 7.4 s;
TCV achieved 100% bootstrap current; and DIII-D46 achieved a fully non-inductive high bootstrap
current fraction (~ 60%) operation around N = 3.5, which is twice the normalized pressure in the ITER
reference scenario. These high poloidal beta regimes also have improved energy confinement, making
high poloidal beta regimes promising modes to operate a commercial fusion power device and a fusion
DEMO. Higher magnetic field in the compact fusion pathway allows higher fusion power density while
also operating with high poloidal beta and lower plasma current. As shown in Figure 4.4(a), a compact
fusion pilot plant (shown as the star symbol and labeled “HT-SC Compact”) operating at high magnetic
field and within an advanced fusion confinement regime would produce significant fusion power while
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Normalized Pressure (β N)(a) Normalized Plasma Pressure vs. Plasma Duration(b) Fusion Triple Product vs. Plasma Duration
ITER
Long-Pulse

DEMO
FNSF

TRIAM-1M (5 hours)

FIGURE 4.5 Diagrams of fusion plasma performance versus duration of plasma operation. Top (a) shows
normalized plasma pressure versus duration, with high βN indicative of high-power density and self-sustained
plasma current. Bottom (b) shows the fusion triple product versus duration, with the product ni(0)ETi(0)proportional to fusion energy gain. The highest performance is achieved for short duration. The longest plasma
duration is achieved with superconducting magnets with sustained injection of external plasma heating power.
TRIAM-1M (Japan) has world record in plasma sustainment of 5 h and 16 min. Tore Supra (France) was
sustained for more than 5 min, and the plasma was sustained in the superconducting Large Helical Device(LHD) in Japan for 48 min. SOURCE: Adapted from M. Kikuchi, M. Azumi, Frontier in Fusion Research II(Springer, 2015) and from C.E. Kessel, et al., “Overview of the fusion nuclear science facility, a credible
break-in step on the path to fusion energy,” Fusion Eng. Des. (2017),
http://dx.doi.org/10.1016/j.fusengdes.2017.05.081.

operating at lower plasma current and full bootstrap current. Similar levels of fusion power were
described by the HTS-ST pilot plant design developed by Menard and co-authors.47
As was described in the Chapter 3 section on “Extending ITER Performance,” just as recent
advances in theory and simulation provide opportunities to significantly extend ITER performance, theseadvances also improve the prospects for a compact fusion pilot plant. Experiments at U.S. researchfacilities have achieved record plasma pressure, demonstrated advanced operating scenarios, like theSuper H-Mode, and tested methods to improve divertor power handling. Simulations of integrated corepedestal performance have already been used to optimize steady-state scenarios on DIII-D and makeinitial predictions for ITER. These advances optimizing fusion performance for ITER combine withadvances in magnet technology to motivate the reduced size and capital cost of the compact fusion pilot
plant.
Finding: While significant progress is needed to achieve uninterrupted operation of a highperformance fusion confinement device, the higher magnetic field in the compact fusion pathway,
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when combined with advanced operating scenarios, appears to allow operation at high fusion
power density, high poloidal beta, and high bootstrap current fraction more easily than otherpathways to commercial fusion power.
THE TECHNOLOGY PATHWAY TO ECONOMICAL FUSION POWER
Research aimed at developing a fusion-based power plant has, to date, focused mainly on theplasma physics and confinement itself, including the plasma, the divertor and first wall, as well as themagnets and heating systems. These are all necessary features of a power plant, and significant progresshas culminated with the construction of ITER. But, these aspects alone are not sufficient for a fusionenergy pilot plant. The attractiveness of a fusion system, in terms of economics as well as safety andenvironmental considerations, is mainly determined by the materials and design of systems that will
extract the fusion power in order to convert it to electricity and sustainably generate, or breed, tritium. At
present, these systems for the divertor and first wall, and integrated blanket are at a very low technicalreadiness level, and significant fusion nuclear science and technology research is needed to provide thetechnological foundation required for the design and construction of a compact fusion pilot plant.
As noted earlier, a number of transformative enabling capabilities illustrate how rapidly
developing technology advances may speed progress and lower the cost of fusion energy development.
These transformative capabilities include advanced materials, high temperature and/or high field magnets,
and tritium processing, all of which offer the potential to significantly increase the technical readinesslevel to enable construction and mitigate risks toward the initial operation of the compact, advanced
fusion energy test facility. In particular, the TEC report of the U.S. DOE/FESAC on Transformative
Enabling Capabilities for Efficient Advance Toward Fusion Energy noted that “magnet systems are theultimate enabling technology for magnetic confinement fusion devices. Advances in the development ofsuperconductors that operate at higher temperature and higher field, referred to as HTS, present a
potentially transformative opportunity to significantly enhance the performance and feasibility of a large
variety of magnetic confinement devices.”
In addition to advancement in superconducting magnet technology, the TEC report describedrecent advances in “novel synthesis, manufacturing and materials design are providing the mostpromising transformation enabling technologies in PMI and nuclear fusion materials to enable fusionenergy for the future.” The TEC report identified a number of potentially transformative developments intritium extraction and processing that show promise for a commercial fusion reactor, but will require
further research and development, in addition to demonstration in a compact fusion energy test facility.
In the following, opportunities to advance magnetic fusion energy through engineering science,materials science, and fusion nuclear technology are described. Taking advantage of these research
opportunities would increase the technical readiness needed for the design and construction of a compact
fusion pilot plant.
High-Critical-Temperature Superconducting Magnets
Magnetic fusion energy requires access to the highest possible magnetic fields that can be
maintained with superconducting magnets. In general, the highest magnetic fields achievable in practicallarge-bore superconducting magnets have been limited by the properties of the superconducting materials
themselves. The two main well-established options are low-critical-temperature superconductors (LTS).
Niobium-titanium (NbTi) is used in Tore-Supra, EAST, K-STAR, and the two superconducting
stellarators. The higher-field niobium-tin (Nb3Sn) superconductor is used for ITER. Since the mid-2000s,
a new class of high temperature superconducting (HTS) materials was successfully used for large-scale
applications: rare-earth Barium Copper-Oxides (REBCO) tapes and Bi-2212 round strands. Figure 4.6
shows a plot of the critical current density versus magnetic field for low temperature superconducting(LTC) and HTS magnets. REBCO has performance anisotropy parallel and perpendicular to the magnetic
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FIGURE 4.6 Critical current density as a function of applied magnetic field (a) showing the achievements of
new HTS concepts. From Larbalestier, et al., Nature Materials 13, 375 (2014). Also shown are cross-sectionsof low-temperature superconducting strands from CERN/LHC and high-temperature conductor grown onstrong Hastelloy substrate.

field but has high critical current density at high field. Bismuth strontium calcium copper oxide (BSCCO)
superconductor, such as Bi 2212 and Bi 2223, has lower current density at high field but each has its own
merit compared to REBCO. Today, REBCO tapes are commercially available from at least sevenmanufacturers (AMSC, Fujikura, Shanghai Superconductor, SuNAM, SuperOx, SuperPower, and SWCC
Showa).48
REBCO superconductors offer the potential to carry sufficient current density for magnet
applications at fields up to 100 T.49 REBCO has been successfully used to reach fields over 40 T insolenoids50 and has demonstrated engineering current densities exceeding 10 A/mm2.51 This is an orderof-magnitude higher current density compared to conventional low temperature superconductor fusion
magnets, and has generated considerable interest from the private sector. Indeed, the recent MIT –Commonwealth Fusion Systems collaboration has announced it is moving forward with plans to design,
construct and test a large-bore magnet using HTS that is central to the SPARC design of a compact fusion
device with a peak field of 23 T.52
At present, HTS magnets have not been tested in the configuration or at the scale needed forfusion experiments. Key challenges include magnet quench detection and protection, conductor
stress/strain management and characterization of radiation resistance. There is consensus within themagnet community that existing high-strength stainless steel and super-alloy materials are adequate forprojected fusion requirements. Although REBCO is extremely stable in operation, quench detection is asignificant issue due to very slow propagation of the normal zone. The status and future directions of highmagnetic field science, including the potential for fusion energy applications, were assessed in 2013.53
Important goals of the Magnet Development Program of the U.S. DOE Office of High Energy Physics are
to investigate fundamental aspects of magnet design that lead to substantial performance improvements
and cost reduction.54 Progress in the use of HTS magnets for fusion energy applications have beenreported; however, additional engineering research is needed to gain full-size operating experience with
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fusion magnets, including magnet quench detection and protection, demountable coil development andtesting, conductor stress/strain management, and characterization of radiation resistance.
Finding: While additional research and development is needed to establish the technical basis forlarge high-field HTS magnets, the growing industrial capability to produce HTS conductor,
opportunities to partner with industry and other U.S. DOE program offices, and the rapid progressin HTS magnets may enable significant reductions in the size of magnetic fusion devices andsupport the compact lower-cost pathway to fusion development.
Advanced Materials and Manufacturing Methods
Overcoming the performance challenges of materials and structures in the fusion energy
environment is a daunting challenge but yet is critically important to realize the promise of fusion as apractical energy source. Development of materials, components and structures for any complex
engineered system generally occurs in a series of steps, proceeding from relatively simple single variable
experiments to very complex, fully integrated multiple variable tests. Commercially available additive
manufacturing tools exist today and the FESAC Report on Transformative Enabling Capabilities (pp. 3536) noted the rapid advancement of capabilities including mixed material printing, multi-scale features,and large component manufacture.
The first step on the development path begins with screening experiments that are performed
under carefully controlled laboratory conditions. These experiments establish the basic mechanical andphysical properties, chemical compatibility, and fabrication and joining technologies of candidate
materials. If satisfactory results are obtained, more complex experiments are performed in order to
identify materials that perform well in partially integrated or multiple variable tests. The final stage ofmaterial development involves fully integrated experiments with prototypical test sections that are carriedout in an environment combining the appropriate nuclear, chemical, thermomechanical and magnetic
fields necessary to establish lifetime and performance limits. The ultimate goal is to develop an extensive
material database that includes chemical and mechanical properties, and physics based models to
describe the material performance within a fusion power system.
Fortunately, as noted previously in this Chapter, significant advances in materials synthesis,
manufacturing and materials design provide promising transformative capability to develop the integrated
divertor, first wall and blanket materials to survive the fusion environment. Advanced manufacturing
offers the potential to locally tailor the material microstructure within a single component by varying the
manufacturing process parameters, and to create complex structures that were simply not possible withconventional methods. Further, advanced manufacturing will lead to complex lattice or composite
structures for lightweight yet strong components that could optimize cooling channels to increase heatremoval capability. While these tailored materials and complex structures require testing in the neutronand high heat flux environments to characterize their properties for optimizing the material microstructure
and component design, advanced manufacturing offers substantial opportunities to develop complex
hierarchical composites and self-healing materials to enable breakthroughs in emergent fusion materials.
Complex composites and complex solid phase alloys also have promise to demonstrate radiation
tolerance, or even radiation resistance that could be transformative for fusion divertor, first wall andblanket materials. This use of complex composite geometries may significantly improve the performanceof refractory materials for fusion energy applications, and recent developments in continuous fiber andlaminate composites demonstrate promising thermal fatigue and thermo-mechanical response inlaboratory experiments.55 As well, advanced manufacturing techniques could lead to the development ofhybrid material systems that encompass the self-healing and renewable characteristics of liquid metals
with a solid-state matrix that could provide a beneficial plasma facing component with optimal heatremoval. Furthermore, significant developments in SiC/SiC composites have been demonstrated in theceramic gas turbine industry, and have transformative potential for nuclear fusion pilot plant components.
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The FESAC Report on Transformative Enabling Capabilities also called attention to novel tritium
extraction technologies proposed for liquid metal breeding blankets and for plasma facing components.
Tritium science, extraction technologies, and fuel processing are critical challenges for fusion energy
systems, and significant challenges will need to be overcome including the need to develop effective
tritium permeation barriers to prevent release of sizable quantifies of tritium.56
Finding: While advanced manufacturing and complex material component design havetransformative potential, research is required to move beyond the early stage of developing thesealloys and composites. This includes radiation effects, chemical compatibility and corrosion,
unknown response to plasma material interactions and tritium permeation, and component
performance and degradation in the complex neutron, plasma material and thermal-mechanicalloading conditions. Studies will need to proceed from relatively simple single‐variable
experiments to very complex, fully integrated, multiple variable tests.
Enabling Technologies for Heating, Measurement, Plasma Control, and Safe MaintenanceContinued development of the technologies used to heat, control, and measure burning plasma
will be needed as the level of fusion power increases and the duration time of the plasma approaches
steady-state conditions. Additionally, engineering strategies need to be developed for subsystem andcomponent reliability and efficient remote maintenance of fusion nuclear components.
Development of a compact fusion pilot plant with higher magnetic field strength will requiredevelopment of a new generation of higher frequency sources for radio waves and millimeter waves andalso technology research to extend the capabilities and efficiency of higher-power launching apparatus
and transmission systems. Similar to the shorter duration needs for ITER, a compact fusion power-plant
will require continuous injection of high-power electromagnetic waves for plasma heating, plasma profile
control, pre-ionization/startup, and plasma current drive.
Diagnostics have two important roles in preparation for a compact pilot plant. First, newmeasurement techniques are needed to provide the data to validate the physical models and simulation
codes used to extrapolate to future devices. As noted in the NRC plasma science report,57 “quite simply,
we cannot understand what we cannot measure.” Hence, diagnostic development is a key building blockof the predictive understanding that will enable a compact fusion device, and these diagnostics will haveto function reliably in the harsh neutron radiation environment near the burning plasma. New diagnostics
are needed to replace those techniques incompatible with continuous production of fusion power.
Measurements are needed to address the new issues associated with burning plasma experiments, such asdetection of the alpha-particle population in ITER and erosion of material surfaces in the pilot plant.
In addition to measurement instruments, the plasma and fusion energy system will be actively
controlled. Sensors will provide input to algorithms that control actuators in real-time to maintain theplasma in the desired state. Advances in machine learning and mathematical control theory may enableeffective control of fusion plasmas despite imperfect knowledge of the plasma state.
Finding: While continued research and development is needed to adapt enabling technologies foruse in the compact fusion pathway, ongoing advances in heating, diagnostics, and control
underway in support of ITER provide confidence that these technologies can be developed forhigher-power longer-pulse fusion devices.
Blanket and Tritium Fuel Cycle Research
The integrated first wall and breeding blanket of a fusion reactor will need to operate at hightemperature to ensure efficient conversion of fusion power into electricity in addition to generating tritiumin the blanket. The tritium generated in the blanket, as well as the unburned tritium fuel from the plasma
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FIGURE 4.7 Science and technology required to establish a tritium fuel cycle. The diagram has blue bands
depicting the need for two distinct tritium permeation barriers, as reproduced from Tanabe64. Commercial lightwater reactors release about 1 g T per year. 100 g of T is produced annually in a Canadian CANDU reactor, anda total of 20-25 kg T will be available for ITER operation.

exhaust, will need to be efficiently extracted and processed for re-introduction to the plasma. Although
the performance, safety, and economics of a fusion system depend on successful power extraction andtritium breeding, these systems have a low technical readiness and significant uncertainty regarding
performance and operating limits requiring technology advancement to extrapolate handling increasing
tritium concentration and temperature, as illustrated in Figure 4.7.
Testing in prototypic environments is incredibly challenging. Because of the unique operating
environment surrounding a burning plasma, the development of power handling and breeding blanket
systems involves a complex set of interactions among numerous disciplines including materials, thermomechanics, thermo-fluids, magnetohydrodynamics, and corrosion chemistry. The complex, extreme
fusion environment needed to test these components is not currently available. In addition to the science
within each discipline, it is likely that synergistic effects among disciplines will be discovered when
components are tested in a fusion nuclear environment.
The breeding and recovery of tritium as it is processed raises a number of safety concerns toprotect workers, the public and the environment. Tritium is highly mobile, and can readily permeate
through metallic components, especially at elevated temperatures. Tritium will have to be accurately
tracked to assure safety and nonproliferation. The grand challenges of tritium require improved scientificunderstanding of many interconnected phenomena including permeation, radiolytic chemistry, surface
science and kinetics, liquid metal magnetohydrodynamics, and mass transfer. Systems and processes
should be developed that can efficiently and safely continuously process tritium at flow rates andquantities beyond current practice.
The United States has developed a potentially attractive family of blanket concepts, in which adual cooled, lead-lithium eutectic alloy serves as both breeder and coolant. In this concept, the reduced
activation ferritic steel integrated first wall and blanket structure have separate gas cooling and thermaland electrical-insulating inserts based on silicon carbide composites that control the structural material
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temperatures at critical interfaces. However, this concept, along with the other solid and liquid blanket
concepts that have been proposed, remain relatively immature due to a lack of research and testing
capability to assess performance limits. A significant enhancement of research activities is needed tovalidate blanket concepts and the science and technologies of the tritium fuel cycle prior to constructing acompact fusion pilot plant.
The recent TEC report highlighted a number of technologies that show tremendous potential for
fusion power development. These include advances in tritium fuel production in breeding blankets
involving either the dual cooled liquid lithium concept or cellular ceramic blankets. Research into tritium
fuel production would also address unresolved sintering problems in proposed ceramic pebble based
fusion blankets. In terms of tritium extraction, the TEC report identified recent advances in electrolytic
membrane extraction and permeable membrane extraction methods with the potential to efficiently
process and extract tritium from liquid metal blankets. The TEC report also discussed the potential for a
super-permeable metal foil pump that would effectively decouple the plasma and tritium plant operationand thereby reduce the size and inventory of the tritium plant substantially. While the TEC report noted
these potentially transformative tritium fuel cycle technologies, it also noted the relatively low scientificand technical maturity of the fusion blanket system and the systems to manage the full tritium fuel cycle.
Finding: Technical concepts needed to harness fusion energy are ready for design and testing.
These concepts, along with innovations and promising new methods to separate and process
tritium, will be essential to the development of a compact, lower cost fusion reactor.
PRE-PILOT-PLANT RESEARCH PROGRAM FOR THE COMPACT FUSION PATHWAY
Conceptual design studies for various compact fusion pilot plants have concluded that in addition
to a burning plasma experiment research is needed to understand the interconnected science andtechnology for the high-field superconducting magnets and for the fusion components that surround theplasma, convert fusion power into useful heat, and breed and recover tritium. Important optimization isneeded to configure the high-field HTS magnets and determine the burning plasma scenarios for highpower density uninterrupted operation at very low recirculating power. The most cost-effective
configuration or shape for a compact fusion pilot plant has yet to be determined. Configuration options
include divertor geometry, plasma aspect ratio, geometric parameters like elongation and triangularity andothers that may improve the operation of the fusion power system. This “pre-pilot-plant” research
program needs to be guided by an interdisciplinary systems-engineering effort to reduce the size and costof the fusion development pathway and to attract industrial engagement in the development of fusionenergy-based electricity for the United States. By the time construction of the compact fusion pilot planttakes place, industry should be prepared to deliver fully functioning industrially produced components
fabricated using materials that have been appropriately qualified for use in the fusion pilot plant
environment.
This section describes strategic elements within a pre-pilot-plant research program. They areintended to provide guidance for a program extending beyond ITER’s burning plasma experiments andleading to the construction of a compact fusion pilot plant having the lowest possible capital cost. Manytechnical details, research schedules, and issues pertaining to the proper balance between internationaland national research are beyond the scope of the committee’s study. However, the scientific andtechnical requirements for the pre-pilot-plant research program are well-documented through previous
studies of a fusion nuclear science facility (FNSF) or a fusion pilot plant. Figure 4.8 illustrates the scienceand technology research elements of a “pre-FNSF” program that would still be necessary for the Compact
Pilot Plant.
The pre-pilot-plant science and technology research program will need a coordinated engineering
approach to guide a variety of laboratory scale experimental facilities, computational modeling andanalysis, and collaborations with the international effort. New non-nuclear program elements will be
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FIGURE 4.8 Elements of the “Pre-FNSF” research program leading to the design and construction of a fusion
nuclear science facility (FNSF). Both nuclear and non-nuclear testing is shown. A similar research program isneeded for a compact fusion pilot plant; however, an essential additional element of a plan to a compact fusion
pilot plant is a program of engineering systems studies that guides research along the lowest-cost pathway.
SOURCE: Figure 14 of C.E. Kessel, et al., “Overview of the fusion nuclear science facility, a credible break-in
step on the path to fusion energy,” Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.05.081.

needed for testing and evaluation of HTS fusion magnets, and for establishing critical design data forsimultaneous thermo-mechanical loading in a high-temperature environment. A facility will be needed forevaluating the performance of divertor and plasma facing components at high temperature withrepresentative particle and heat fluxes and compatible with high-performance and high-pressure fusion
confinement. The mission requirements for this facility integrates the science and technology from thehigh-performance core to the divertor and expands upon the mission requirements for the Divertor Test
Tokamak (DTT) proposed in both the 2015 FESAC Report on Plasma Materials Interactions and forconstruction in Italy.58 The experimental demonstration of integrated uninterrupted high-power density
magnetic confinement regimes is needed in order to validate the configuration and operation space for acompact fusion pilot plant. A new national research facility is probably needed to provide this. If so, theconstruction of such a new facility would occur after the most critical research missions of the national
DIII-D and NSTX-U facilities are completed.
Fusion nuclear testing is essential for materials development and qualification for all aspects offusion research. Fusion nuclear tests can include both fission and fusion relevant neutron exposure ofindividual material samples. A larger volumetric fusion neutron source can provide experimental data andinitial nuclear testing of integrated first wall and breeding blanket systems as well as critical data on theeffect of radiation damage and transmutation effects from a 14-MeV peaked neutron spectrum. While thestrategies adopted in previous FNSF and DEMO pathways required qualification of all materials near thefusion core to the neutron fluence they will experience, a staged-approach to the operation of the compact
fusion pilot plant may have simpler materials qualification requirements in a first-stage because of lower
neutron fluences. This two-stage approach reduces the cost and accelerates fusion demonstration in thecompact fusion pathway.
The key elements of the pre-pilot-plant research strategy, in addition to the burning plasma
science and technology that will be learned from ITER operation, are:

Systems-engineering for a compact fusion pilot plant,

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
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Advanced materials modeling for fusion technology,
Testing of large-bore, high-field HTS magnets for magnetic fusion,Developing long-lifetime materials for fusion,
Advancing tritium science and blanket technologies,
A fusion neutron irradiation facility for prototypical materials qualification,
Demonstrating sustained high-power-density fusion plasmas with optimized plasma exhaust
configuration for compact fusion, andContinued development of fusion-enabling technologies needed to heat, measure, and control
the burning plasma and to safely maintain the components within the compact fusion pilot
plant.
Systems-Engineering for a Compact Fusion Pilot Plant

Options for a compact fusion pilot plant are at a pre-conceptual design stage, and iteration of theengineering design is needed to evaluate configuration options for reaching the optimum design goals.
Systems engineering involves the integration of multiple science and technology realms including
burning plasma science, configuration optimization and development of HTS fusion magnets, a compact
blanket, licensing procedures, tritium processing technology, and enabling technologies like efficient
plasma heating and current-drive systems. The design of the pilot plant should include both optimizationof the burning plasma configuration and also considerations for efficient and low-cost balance-of-plant(BoP) systems needed for operating the plant. Experience from ITER operation will be important input tothe design optimizations regarding plasma initiation, divertor science, burning plasma control, and othersupporting fusion technologies. Examples include experience with ITER’s tritium-handling system,
cryogenic systems, and measurement and control systems.
A systematic study is needed to explore configuration options for the compact fusion pilot plant.
It should identify research needs and facility needs that can be addressed in the pre-pilot-plant program.
Operational scenarios will need to be developed and supported by validated modeling incorporating stateof-the-art advances in coupled core-edge plasma simulations. Metrics for evaluating design options
should include the capability for uninterrupted operations, very low recirculating power, demonstration offusion electricity, a staged approach to tritium self-sufficiency, and a justified estimate for theconstruction cost. At the end of the concept design study, focused engineering design activities shouldcommence with significant involvement of industry. Industrial experience could be developed byindustrial participation in testing of component prototypes prior to the decision to construct a compact
fusion pilot plant.
Advanced Materials Modeling for Fusion Technology

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FIGURE 4.9 Photograph and schematic of the Large Coil Test Facility managed by ORNL at the International
Fusion Superconducting Magnet Test Facility (IFSMTF). Six large-bore fusion magnets from industries in the
United States, Switzerland, Europe Atomic Energy Community, and Japan operated for two years (1985-1987),
reached stable operation at B = 8T, and successfully demonstrated low-temperature superconducting magnet
technology for fusion. (Right) Photograph of all six superconducting magnets. (Left) A cross-section of the
LCTF from "Large Coil Task Specifications." Fusion Eng. and Design, 7, pp. 15-22 (1988).

The United States has made significant advances in multi-scale modeling of plasma materials
interactions and high-energy neutron induced degradation of structural materials.59,60,61 These multiscalemodels attack the complex materials degradation issues from both a “bottom-up” atomistic-based
approach and a “top-down” continuum perspective, and they focus on the hierarchical integration of
kinetic processes for species reactions and diffusion to model microstructure evolution over experimental
timescales. The simultaneous use of both an atomistic and continuum approach has furthered thedevelopment of scale-bridging or multi-scale integration, and has led to fundamental insight into helium –hydrogen synergies controlling tungsten PMI as well as the long-term microstructural evolution due toradiation damage in structural materials65. However, it is important to note that these emerging modelingcapabilities are in the early stages of development, and continued research activities are required tofurther develop this capability further. Central to the development of advanced modeling is to closely
coordinate the modeling activities with experimental studies to provide both model validation andguidance for future modeling activities, as well as to design experiments to resolve specific scientificchallenges such as simulating changes in multi-component surfaces and materials that are formed byerosion and re-deposition processes of PFC surfaces and neutron transmutation of structural materials.
Large-Bore, High-Field HTS Magnets for Fusion
The compact fusion pathway requires development of large-bore, high-field HTS magnets.
Currently HTS magnet research and development is focusing on commercial production improvements,characterization of conductor performance, and the scale-up and integration of the magnet assemblies andcomponents, such as the cables needed to fabricate full-size fusion-class magnets.
On March 9, 2018, MIT and a newly formed private company, Commonwealth Fusion Systems(CFS), announced the start of a staged research effort for fusion experiments and fusion power systems
based on advances in high-temperature superconductors.62 Other efforts to develop large HTS magnets
include the Magnet Development Program sponsored by the U.S. DOE Office of High Energy Physics,
the National Institute for Fusion Science (NIFS) at Toki, Japan, the National High Magnetic Field
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Laboratory (Tallahassee, FL), which announced the world's largest magnetic field generated withsuperconducting solenoid in December 2017, and several European efforts including CERN, CEA (FR),KIT (DE), University of Geneva (CH), University of Twente (NL) and Bruker HTS (DE).
Because of the importance of HTS magnet development for fusion, an opportunity exists toinitiate a large-coil HTS test facility modeled after the Large Coil Test Facility (LCTF) that was hosted by
the ORNL in the 1980s. Figure 4.9 shows a photograph of the installation of one of six LTS magnets anda schematic showing the cross-section of the LCTF. The international magnet test facility evolved fromthe Large Coil Project (LCP) imitated through contracts awarded to industrial teams led by GDC (General
dynamics Convair Division), GE (General Electric Company) and WH (Westinghouse Electric
Cooperation). Later, the International Energy Agency (IEA) Fusion Power Coordinating Committee(FPCC) sponsored an international agreement with partners of EURATOM, Switzerland and Japan. Eachof the six coils that were tested had different features but met equivalent magnet requirements. The GDC
coil used Nb3Sn, while the other five coils used NbTi as the superconductor. A U.S. sponsored HTS test
facility would likely attract participation from industries from several nations. Such international
cooperation, along with the opportunity to partner with private industry within the US, would be quite
useful for accelerating optimizing HTS coil design as well as identifying the most cost-effective
manufacturing method.
In addition to a large coil HTS test facility, several important smaller scale components, including
a new, very near-term test facility, are needed if the United States is to play a leading role insuperconducting magnet development for fusion. The purpose of such an additional facility is to allow
testing of full size HTS jacketed cable samples at high field over a range of temperatures and currents.
This HTS sample test facility has been strongly urged by United States superconducting magnet
researchers. It would be much less costly than a full coil test facility, and research use may include nonfusion applications of HTS magnets including those for high-energy physics. This relatively small facility
has the potential to substantially speed up magnet development since new designs and concepts can be
rapidly tested under realistic conditions with small sample sizes. As of now, testing of such cable samples
take place either in NIFS (Japan) or SULTAN (Switzerland), neither of which has the high field
capabilities needed for HTS. Furthermore, the United States has little control over the prioritization ofusage time at these facilities of other nations. The other equally important components of a U.S. HTS
program include the development of magnet quench detection and protection systems, demountable coildevelopment and testing, conductor stress/strain management, characterization of radiation resistance, andcontinued research and development of advanced HTS materials.
Developing Long-Lifetime Materials for Fusion
One of the keys to understanding and controlling plasma material interactions in the divertor andplasma facing components is to collect data on the evolution of material surfaces during and following
long-term plasma exposure. The United States program has contributed significantly to this researchthrough PMI experimental studies based on the PISCES facility.63 Additional research is needed to
explore very long duration exposure under conditions of high heat and particle flux with a representative
geometry. The opportunity exists for a cost-effective linear plasma material interaction test stand thatwould utilize a high-intensity radio frequency (RF) plasma source for experimental PMI studies. The newlinear test stand should be able to operate uninterrupted for many days and expose targets at glancing
angles with an applied magnetic field in order to test models of the plasma-material sheath, theacceleration of ionized impurities, emission of secondary electrons, while maintaining ion and neutral
fluxes directly relevant to a fusion divertor.64 The knowledge gained from PMI tests stands would need tobe coordinated with plasma divertor research and inform the selection of divertor materials needed tosustain a high-power density fusion plasma with an optimized plasma exhaust.

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Advancing Tritium Science and Blanket Technologies
A commercial source of fusion electricity requires a closed tritium fuel cycle. In order to fully
realize commercial fusion power, the science and technology of tritium needs to be developed. This
includes all tritium processes and the methods needed for safe operation and benign environmental
impact. Virtually all of the technologies related to the tritium fuel cycle are at low technical readiness,with uncertain parameters that describe tritium migration through materials and across interfaces, its
retention in bulk solids and liquids, and retention and behavior in plasma facing materials. Building
technical readiness for fusion power requires a program of materials testing and component performance
when exposed to fusion neutrons.65,66
In a fusion power system, the breeding blanket is a critical component that consists of a set ofmodules covering the interior of the fusion vacuum vessel, capable of supporting a high heat load and an
intense neutron flux.67 The breeding blanket will need to (1) assure self-sufficiency of the fusion reactor
with regard to tritium, (2) maximize the net efficiency of the power plant, (3) act as a radiation barrier,and (4) act as structural barrier to limit dispersion of the tritium and potential activation products
suspended in the coolant.68
ITER provides an opportunity to answer questions regarding tritium processing at large scale
within the fueling/exhaust tritium loop. The ITER Test Blanket Module (TBM) program is the firstopportunity to study whether tritium can be generated in a blanket and whether heat can be extracted for
power production.69 Although the amount of bred tritium to be handled will be relatively low, due to asmall testing area and low plasma duty cycle, the tritium transport processes involved in the TBM
program are prototypical of the fusion blanket tritium fuel cycle, including deuterium and tritium neutral
ion flux implantation and the resulting transport and permeation under prototypical tokamak plasma
facing surface and operating conditions.
The complexity involved in understanding the behavior of breeding blanket concepts in the fusion
environment has led to a rather detailed planning for TBM testing program in ITER.70 During the nonnuclear phase of ITER operation, the TBM testing objectives are to (1) test the electro-magnetic response,(2) verify the test blanket system operation in the ITER operating environment, (3) demonstrate thecooling capability and TBM resistance to ITER disruptions, (4) obtain data required for the nuclear
licensing process, and (5) confirm that the TBMs do not jeopardize the quality of plasma confinement.
During the nuclear phase with operation with deuterium and deuterium-tritium plasma, the main ITER
TBM objectives are to (1) test the thermal-neutronic behavior, neutronic-tritium/thermo-mechanic
response and integral performance of the modules, (2) validate the predictions with modeling codes andnuclear data, (3) assess the TBMs thermo-mechanical behavior, (4) demonstrate the tritium management
capability, and (5) demonstrate TBM performance for an extended period of time.
At the ITER Organization (IO), the ITER Test Blanket Module (TBM) program will provide an
opportunity for testing tritium breeding blanket concepts that would result in tritium self-sufficiency, an
extraction of high-grade heat and net electricity production in future fusion reactors. Although all of the
TBM Arrangements were signed in 2015, the ITER International Organization (IO) has not made a final
determination on proceeding with the ITER Test Blanket Module (TBM) program, and the decision to
install the TBM on ITER requires signing additional legal arrangements dealing with all TBM phases
through decommissioning.
The United States is not currently a partner in the ITER TBM Program. Whether or not the U.S.
becomes a supporting partner in a TBM activity would need to be determined after further considerationof the schedule and capabilities of the ITER TMB activities, as well as the goals of the new national
blanket technology program are defined. Should the United States decide not to seek supporting
partnerships on one or more ITER TBMs (assuming they are approved by the ITER IO), then the UnitedStates will forego access to and experience with the resulting demonstrations and will need to develop thisexperience through the national blanket technology program. If an ITER TBM partnership collaboration
were initiated, the United States, for example, could contribute critical property data such asrecombination coefficients, tritium diffusivity in PbLi, MHD mixed convection on tritium transport, and
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tritium transport within permeation barrier coatings, through small scale laboratory tritium experiments.
Additionally, international collaboration on the various aspects of the tritium fuel cycle and theaccompanying areas of fusion nuclear materials, plasma facing materials, fusion nuclear science, andenabling technologies requires serious consideration. These objectives are critical steps toward
developing working breeding blankets for future fusion concepts.
Other opportunities exist in blanket and tritium fuel cycle research that could be conducted inparallel with the ITER activities. Non-nuclear testing can be conducted to advance understanding ofthermo-solid and thermo-fluid mechanics, tritium extraction and migration, and some aspects of a fuelcycle development facility. The thermal-fluid testing would incorporate surface and volumetric heatingwith high magnetic field strength and representative coolant flow rates. This non-nuclear fuel cycle
research and development investigates only deuterium/hydrogen isotopes to advance the required
technologies for tritium extraction and processing. Because fusion neutron irradiation will changematerials properties, such as barriers to tritium penetration, beneficial synergies should be explored, suchas the possibility that enhanced trapping of tritium in solid material due to damage or even thenanostructured particles introduced may enhance the material’s radiation resistance. Access to a neutron
irradiation facility is required for initial data on neutron exposure effects on welds, component lifetimes,
and reliability.
Fusion Neutron Irradiation Facility
The fusion nuclear engineering community has long advocated a dedicated fusion neutron
irradiation facility for acquiring material irradiation test data in a simulated fusion environment for
design, licensing, construction and safe operation of fusion structural materials and, also, forbenchmarking radiation responses of materials with computational material science. Existing neutron
irradiation sources include accelerator-driven sources, like the SINQ Target Irradiation Program (STIP) at
the Swiss Paul Scherrer Institute (PSI), and fission-based sources like the High Flux Isotope Reactor(HIFR) at ORNL. Options for fusion neutron irradiation facilities with a 14 MeV fusion neutron spectrum
do not now exist although proposals for such a source include a plasma-based volume neutron source(VNS) or accelerator-based facilities with either gas, liquid or solids targets.71 Based on joint Japaneseand European research in the framework of the Broader Approach (BA) agreement, the IFMIF-DONES(International Fusion Materials Irradiation Facility - DEMO-oriented Neutron Source) is currently being
developed for the irradiation of temperature controlled capsules containing test specimens filling a 54 cc
volume. The capsule-averaged structural damage rate expected for IFMIF-DONES reaches 15 dpa/fpy.72
Opportunities should be explored to provide a larger-volume fusion irradiation environment thatwould study and increase the technical readiness level of breeding blanket components and systems prior
to the construction of the compact fusion pilot plant. A low-cost material testing facility has been
proposed for near-term fusion materials research.73 Recognizing the need to conserve resources, fusion
engineers have proposed either a low-cost linear mirror device for blanket testing or, when mirror
research was abandoned in the U.S., a driven tokamak.74,75 New results in the gas dynamic trap (GDT)
mirror device at Novosibirsk have revived interest in the mirror option.76
The licensing requirements for the first and second phases of the compact fusion pilot plant need
to be determined early in its planning. If irradiation data are only required for structural material samples
and welds, then full-size fusion components can be tested as part of the fusion pilot plant research
program. If larger volume irradiations are required, then program planning would need to design andconstruct a cost-effective plasma-based neutron source. In particular, determining whether construction ofa volumetric fusion neutron irradiation facility using a magnetic mirror device, or an alternate
configuration, would more rapidly advance the technical readiness and lower the cost of the compact
fusion pathway needs to be answered as part of the systems engineering studies.

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Sustaining High-Power Density Fusion Plasmas with Optimized Plasma Exhaust
The United States has made significant contributions to the development and understanding of
high-performance, steady-state burning plasma operating scenarios that will be used in ITER todemonstrate fusion power gain for pulses of several minutes. However, the compact fusion pathway
requires further advances in fusion performance to achieve high power density in a small-sized device
with integrated core-edge plasma scenarios capable of uninterrupted operation. This approach is inspiredby recent experiments, which were motivated by theoretical studies, that demonstrated record
performance on Alcator C-Mod (world record plasma pressure) and DIII-D (high equivalent fusion gain)
through optimization of the pedestal performance. Separate experiments have demonstrated highperformance steady-state scenarios with no ELMs and the sustainment of high bootstrap fraction
scenarios with internal transport barriers at near zero rotation. Further, the impact of reduced aspect ratio
and improved boundary shaping on access to regimes of enhanced pedestal confinement and stability will
be investigated utilizing NSTX-U operation at higher plasma current and toroidal field. Additionally,
theoretical studies have indicated the distinct advantages of high-field side-launched RF in obtaining
much higher current drive efficiencies, which if realized could lead to more efficient fusion systems.
The investigation of compact burning plasma conditions will require increased values ofnormalized size, R×B/T1/2, while maintaining achievable levels of plasma collisionality and normalized
plasma pressure, ~ nT/B2. Currently the two U.S. national facilities (DIII-D and NSTX-U) are operating
at relatively low toroidal fields (B = 2.2 T in DIII-D and B = 1 T in NSTX-U). A device built at the size of
DIII-D but with a much larger magnetic field (about B ~ 4 T) and with larger heating power (Pheat ~ 50MW) would be a potential facility. Opportunities exist to extend the capabilities of the U.S. national
facilities. High-performance fully non-inductive scenarios can be explored on NSTX-U77 and withplanned upgrades of DIII-D78 and NSTX-U.79 A follow-on national facility, which combines the research
efforts of the DIII-D and NSTX-U, could provide new advanced tokamak studies closer to burningplasma conditions.80 This would involve a substantial upgrade, or a new facility.
A key issue in assessing the compact fusion pilot plant is confinement performance scaling athigh N as the normalized device size, R×B, increases. High N reduces the size of the fusion device andincreases the bootstrap current fraction, thereby reducing the current drive power and improving theoverall efficiency of the pilot plant. While ITER and JT-60SA will provide some information about
performance improvements with increasing N, plasma edge pedestal models predict that the highest
performance, and hence highest fusion power density, will be achieved with optimal shaping of theplasma, including aspect ratio, triangularity, and elongation. DIII-D and NSTX-U are well positioned toprovide key information on the choice of the required parameters for a follow-on high-power density
research facility needed to establish the science and technology basis for the compact pilot plant. Thisapproach would also enable exploration of the physics benefit of high field operation, particularly the
impact on improving plasma confinement, which is synergistic with the high temperature superconductor(HTS) research. In fact, practical experience could be gained with smaller HTS TF magnets if the magnet
R&D delivers such a capability on the necessary timeline. Considering the importance of long-pulse
advanced tokamak operation to the compact fusion pathway, the availability of HTS magnets would besignificant, but its use critically depends on the outcome of timely HTS magnet development.
Theory and Simulation
Integrated simulation has long been part of fusion energy research, and recent years have seen atremendous improvement in the ability to perform simulations with increasing physical fidelity.
Theoretical and computational models developed in the United State have substantially improved theability to predict plasma confinement, control plasma stability, and enhance fusion energy
performance.81,82

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In addition to integrated simulation making important contributions to developing burning plasma
science with ITER, advancement along the compact fusion pathway will benefit from research on
integrating more multiple physics, multiscale phenomena, and higher-fidelity algorithms into simulations
as well as further expanding the simulation capabilities toward prediction and design. These advances intheoretical and computational models, which enable the development of whole device modeling withincreasing physical fidelity, have been facilitated by the rapid growth in computational capabilities andthe U.S. DOE Office of Science initiatives that have encouraged partnerships among fusion, appliedmathematics and computer science researchers.83
High-fidelity whole device simulations will improve physics understanding and further enableoptimization of the high density, high performance plasma core coupled to a detached divertor. Continued
research investments in whole device modeling should improve the fidelity of kinetic simulations, help
develop model hierarchies for incorporating disruption and boundary physics, allow incorporating theinteractions of fast particles with thermal plasma waves and instabilities, the strong coupling of coretransport to sources and instabilities, and improve the coupling of the plasma surface interactions andboundary plasma physics to the pedestal and plasma core. Advances in whole device models, as well as
individual physics models, are anticipated to enhance the capability of probabilistic whole device
modeling to assess the likelihood of key physical transitions such as those leading to plasma disruptions,to optimize operational conditions for achieving specific fusion energy gains, and to optimize or evenincrease the divertor heat flux thresholds.
Stellarator Contributions to Compact Fusion Energy
The compact fusion pathway is based on an advanced tokamak configuration operating at
sufficiently high normalized beta and sustained continuously, without the need for significant current
drive power, because of self-generated bootstrap current. The tokamak configuration has dominated theworld’s fusion research program. Fusion performance achieved with the tokamak configuration issuperior to other magnetic configurations; however, theory, simulation, and experiments with thestellarator configuration is strongly related to the tokamak and can contribute to the integrated science andtechnology needed to design the compact fusion pilot plant.
The stellarator concept was invented in the U.S. and, in some configurations, the confinement
field can be produced entirely by the external magnetic coils. Two large stellarator devices operate withsuperconducting magnets: the Large Helical Device (LHD)84 in Japan and the Wendelstein-7X (W7-X)85
stellarator in Germany. A smaller, helically symmetric stellarator (HSX), built with copper magnets, islocated at the University of Wisconsin in the United States. As shown in Figure 4.5, the plasma durationof the LHD stellarator has achieved pulse lengths comparable to what is expected in ITER, except at
much lower fusion gain. Because most of the rotational transform of a stellarator is generated fromexternal coils, the stellarator magnetic configuration does not require current drive power. Additionally,
because the magnetic configuration is controlled primarily with external magnets, a transient confinement
loss due to plasma instability should avoid all plasma current disruptions and the generation of runaway
electrons.86
W7-X has a high aspect ratio (A > 10) with a large major radius, R = 5.5m. The W7-X stellarator
is called a “heliac,” and HELIAS fusion reactor studies show this type of configuration leads to large
fusion power systems.87,88 Currently, the United States is an active collaborator in the W7-X experiment,
and stellarator research using W7-X contributes to understanding of all aspects of toroidal magnetic
confinement, including energy and particle transport, energetic particle physics, and divertor science andtechnology. The two large stellarators with superconducting magnets (see Fig. 4.5) have achieved
operating conditions comparable to the superconducting tokamaks, EAST (China) and KSTAR (ROK),
when operating for about one-minute pulses. These superconducting fusion research facilities provide
opportunities to develop the science and technology needed for continuous operation and to learn fromthe comparison between axisymmetric and three-dimensional magnetic geometry.
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While the long-pulse capabilities of the superconducting LHD and W7-X stellarators contributeto the knowledge needed for the long-pulse operation of the compact pilot plant, stellarators with “hidden
symmetry,” either quasi-axisymmetry (QA) in the toroidal direction or quasi-helical-symmetry (QH) in
the helical direction, will also contribute to understanding of the role of symmetry in high-performancemagnetic confinement and stability through the development and validation of predictive models. As
presented to the committee,89 the toroidal magnetic confinement with quasi-symmetry have not been welltested in the laboratory, but opportunities exist for an optimized intermediate-scale research facility that
may impact the national effort to design a compact fusion pilot plant. Such optimization is expected to be
useful to generate flow in the quasi-symmetric direction and hence to enhance confinement by flow shear
suppression of turbulence. In a quasi-symmetric stellarator, unlike the heliac configuration, plasma
currents will change the magnetic structure as plasma pressure increase. Quasi-symmetric stellarators
might help validate models to predict fusion performance and improved optimization of a compact fusion
pilot plant. Because the only operating quasi-symmetric stellarator is located in the United States and,more importantly, because quasi-symmetric stellarators might lead to improved designs for a compact
fusion confinement system, opportunities exist to explore this configuration and validate the physics ofthree-dimensional magnetic fields and quasi-symmetry for toroidal magnetic confinement.
Fusion Enabling Technologies for Plasma Heating, Current Drive,
Measurement and Control and Safe Maintenance of Core Components
The compact pathway to fusion requires higher magnetic fields and long, uninterrupted plasma
operation. Continued development of fusion enabling technologies include: higher frequency gyrotrons
and transmission systems in the range of 250-336 GHz, higher power, more compact antenna/wave
launching systems for a compact pilot plant, advancement in diagnostic and plasma control systems, andthe implementation of remote maintenance of fusion components located near the burning plasma. Before
the operational pulse times of fusion research facilities can significantly increase, research anddevelopment of the associated plasma heating, plasma current drive, and plasma control systems are
required. Examples of such research are described earlier in this chapter, and Chapter 2 described ongoing
research activities for robust current drive technologies, like injection of high-frequency “helicon” waves.
SUMMARY
This chapter describes the interconnected science and technology research required within an
expanded U.S. burning plasma research program in the near and mid-term leading to construction of acompact fusion pilot plant at the lowest possible capital cost.
Finding: Recent advances motivate a new national research program leading to the construction of acompact fusion pilot plant at the lowest possible capital cost that will accelerate the fusion
development path. Significant progress has been made to predict and create the high-pressure plasma
required for such a reactor. This progress combined with opportunities to develop technologies forfusion, such as high-temperature superconducting magnets and advanced materials, now make acompact device technically possible, affordable, and attractive for industrial participation. Thisfinding is supported by the following:

Although additional research, including magnet engineering research, is needed to demonstrate
the viability of the compact pathway to fusion power, the combination of new high-field
superconducting magnet technology with advanced burning plasma science is a significant
opportunity to decrease the size and cost of a magnetic fusion power system.
While methods to remove heat from the divertor and reduce material erosion due to plasma
sputtering remain active research areas, current understanding of divertor scaling shows that the
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









compact fusion pathway at higher field and lower total power may benefit power handlingsolutions for fusion energy.
While significant progress needs to be demonstrated to achieve uninterrupted operation of a highperformance fusion confinement device, the higher magnetic field in the compact fusion pathway
appears to allow operation at high fusion power density, high poloidal beta, and high bootstrap
current fraction more easily than other pathways to commercial fusion power.
While additional research and development is needed to establish the technical basis for large
high-field HTS magnets, the growing industrial capability to produce HTS conductor,
opportunities to partner with industry and other U.S. DOE program offices, and the rapid progressin HTS magnets promise significant reductions in the size of magnetic fusion devices andsupports the compact pathway to fusion development.
While advanced manufacturing and complex material component design have transformative
potential, research is required to move beyond the early stage of developing these alloys andcomposites. This includes radiation effects, chemical compatibility and corrosion, unknown
response to plasma material interactions and tritium permeation, and component performance anddegradation in the complex neutron, plasma material and thermal-mechanical loading conditions.
Studies should proceed from relatively simple single‐variable experiments to very complex, fully
integrated, multiple variable tests.
While continued research and development is needed to adapt enabling technologies for use in thecompact fusion pathway, ongoing advances in heating, diagnostics, and control underway insupport of ITER provide confidence that these technologies can be developed for higher-power
longer-pulse fusion devices.
Technical concepts needed to harness fusion energy are ready for design and testing. These
concepts, along with innovations and promising new methods to separate and process tritium, willbe essential to the development of a compact, lower cost fusion reactor.
Based on these findings, the committee offers the following recommendations:
Recommendation: Along with participation in international fusion research, including the
ITER partnership, the U.S. DOE OFES should start a national program of accompanying
research and technology leading to the construction of a compact pilot plant, which
produces electricity from fusion at the lowest possible capital cost.
Recommendation: In the near- and mid-terms, the U.S. Department of Energy should
resolve critical research needs for the construction of a compact fusion pilot plant: Understand the science, production, and control of burning plasma at the scale of apower plant through participation in ITER.
 Demonstrate the science and engineering needed to sustain a magnetically confinedplasma having the high-confinement property and compatible plasma exhaustsystem that are needed for a compact fusion pilot plant.
 Advance high-critical-temperature superconductors (HTS) and demonstrate theability to achieve high magnetic fields using large, fusion-relevant coils.
 Expand significantly the U.S. research program in fusion nuclear technology,
advanced materials, safety, and tritium and blanket technologies needed to fully
enable fusion energy.
 Develop promising innovations in burning plasma science, such as optimized
stellarator configurations and innovative approaches for a low-cost fusion
irradiation facility, and fusion engineering science that reduce the cost and improve
the fusion concept as a source of electricity.

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Recommendation: In addition to study of a burning plasma, new research facilities should bebuilt to increase the technical and scientific readiness of critical capabilities needed to construct
a compact fusion pilot plant. This will require retiring one or more existing facilities as they
complete their most important goals.
Recommendation: In recognition of the significant challenges that needs to be addressed for theconstruction of a compact fusion pilot plant facility capable of electricity production, the U.S.
DOE OFES plan for a pilot plant should have a two-phase approach. These objectives of thesetwo phases are:
 In the first phase, the pilot plant should be capable of demonstrating fusion electricity
production for periods lasting minutes and establish the feasibility of electricity
production in a compact fusion system including the assessment of plasma materialinteractions, tritium safety, pumping, recycling, breeding, and extraction.
 In the second phase, the pilot plant should be capable of uninterrupted operation formany days allowing fusion materials and component testing consistent with acommercial power plant, including full fuel cycle blanket testing.

NOTES
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82. Solomon, et al., “Exploration of the Super H-mode regime on DIII-D and potential advantages
for burning plasma devices,” Phys Plasmas 23, 056105 (2016).
83. Bonoli and McInnes, Report on the Workshop on Integrated Simulations for Magnetic Fusion

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Energy Sciences, DOE Office of Science, 2015.
84. O. Motojima, et al., Extended steady-state and high-beta regimes of net-current free heliotron
plasmas in the Large Helical Device, Nucl. Fusion 47(2007) S668
85. T. Klinger, et al., Performance and properties of the first plasmas of Wendelstein 7-X, Plasma
Phys. Control. Fusion 59(2017)014018
86. P. Helander,et al., “Stellarator and tokamak plasmas: a comparison,” Plasma Phys Contr F 54,
124009 (2012).
87. R.C. Wolf, “A stellarator reactor based on the optimization criteria of W7-X,” Fusion
Engineering and Design 83 (2008) 990–996.
88. Akio Sagara, et al., “Review of stellarator/heliotron design issues towards MFE DEMO,” Fusion
Engineering and Design 85 (2010) 1336–1341; http://doi.org/10.1016/j.fusengdes.2010.03.041.
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Research Strategic Directions workshop, submitted to NAS panel 09 April 2018.

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5Strategic Guidance for a National Program for
Burning Plasma Science and Technology
This chapter summarizes previous chapters in the context of the committee’s strategic guidance
for a national program for burning plasma science and technology covering the next several decades. The
committee’s two main recommendations are elaborated. This chapter summarizes program elements, anapproximate research timeline, a response to a decision to withdraw from ITER, and budget implicationsof the committee’s guidance.
This plan has two parts.
First, the United States should seek full benefit from continued participation in the ITER
project as the nation’s burning plasma experiment.
Second, the United States should start a national program of interconnected science andtechnology research extending beyond what will be accomplished with ITER and leading toconstruction of a compact fusion pilot plant at the lowest possible capital cost.

Together, these two research efforts establish the scientific and technical feasibility of fusion
power and advance the fusion program from its current feasibility stage along a cost-effective path to the
production of electricity from fusion. The strategic guidance strengthens United States capabilities inburning plasma science, materials science, fusion nuclear science, and engineering science, continues
engagement in the international effort, and promotes innovation and the involvement of industry.
ITER: EXTENDING THE FRONTIERS OF BURNING PLASMA SCIENCEAt the foundation of the U.S. strategy is the production, study, and exploitation of a burning
plasma. This regime is characterized by plasmas that are dominantly self-heated by the particles generated
by the fusion reactions. Methods to control plasma stability, plasma interactions with first wall materials,
plasma confinement, and fusion power output will be tested. Theoretical predictions of energetic particles
produced by fusion reactions and methods to sustain a burning plasma will be explored and validated.
Equally important are gains in fusion engineering science and industrial capability that result fromconstruction of the world’s first burning plasma research facility at the scale of power plant.
The only existing project to create a burning plasma at the scale of a power plant is ITER, which
is a major component of the U.S. fusion energy program. As an ITER partner, the United States receives
full benefit from the technology that will establish the feasibility of fusion while providing only a fractionof the financial resources
Active participation in the ITER project is necessary for the U.S. to derive full benefit from the
ITER project. The committee is not aware of any credible alternative that might achieve burning plasma
conditions sooner. Effective participation in ITER requires that the U.S. continue to invest in domestic
tokamak facilities and research to address operational issues for ITER and prepare the physics and fusion
technology needed to enable next step devices. United States researchers are providing solutions andtechnical support for successful preparation and operation of the ITER facility. In some areas the UnitedStates is uniquely able to provide essential information. Even at this stage of ITER preparation, U.S.
fusion research experiments provide knowledge needed to refine burning plasma operating scenarios, tofinalize the designs for magnets to control transients, to develop the systems used to mitigate the adverse
impact of plasma current disruptions, and to predict the response of the divertor during the expected
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periods of high plasma heat-flux. Later, during ITER operations, opportunities will exist for the UnitedStates to take leadership in upgrading capabilities and the development and testing of ITER operating
scenarios that may expand ITER’s scientific impact on the physics and predicative design tools used tolower the cost of fusion development.
Ongoing research targeted to resolve issues related to plasma control and transient reductions
should continue. Recent research has been important in developing the ITER plans, which are guided by
new techniques to suppress edge localized modes (ELM) using external control magnets, injection ofsmall pellets of frozen hydrogen, and operation in regimes that are naturally stable to ELMs. A
hierarchical approach is needed for mitigating adverse effects of plasma current disruptions, including
design of scenarios that are naturally disruption resistant, predictive algorithms for assessing the plasma
stability, control tools for stabilizing large scale MHD, recovery modes for dealing with off-normal faults
and reliable mitigation tools when a disruption cannot be avoided. The two largest research facilities
within the United States, NSTX-U and DIII-D, are well-poised to address these issues in the near term.
Examples of additional research tools include additional plasma heating and plasma current drive
systems, expanded magnet systems for precision plasma control, and improved methods to measureplasma phenomena including those diagnostics capable of fully exploiting the physics of plasma current
disruptions.
While reaching the frontier of burning plasma science will establish the feasibility of magnetic
fusion energy, the full benefit from participation in ITER will result from opportunities to develop andtest burning plasma science in order to maximize the potential of a compact fusion pilot plant. Recent
advances in theory and simulation validated by results from United States experiments have alreadysuggested ways to optimize ITER performance. A strong focus on high performance steady-state
scenarios in ITER will advance understanding of the strongly coupled system, where the heating source(primarily fusion produced alpha particles) and current drive (primarily pressure-driven bootstrap current)
are both strongly coupled to confinement and energetic particle physics. Advances in understanding
toroidal magnetic confinement, plasma control, and integrated solutions to whole-plasma optimization
point to improvements beyond the ITER baseline and show how careful design and simulation can beused to lower the cost and accelerate fusion energy development.
The United States research participation with ITER should develop and test burning plasma
scenarios, validate predictive simulation models, and gain engineering experience that will contribute toreliable operation of a compact fusion pilot plant.
BEYOND ITER: SETTING THE NATION’S FUSION ENERGY GOAL
As discussed in the committee’s Interim Report and the technical analysis in the previous
chapters, now is the right time for the United States to develop a national strategic plan for fusion energythat benefits from its investment in burning plasma research and takes leadership in the development offusion electricity for the nation’s future energy needs. The adoption of such a plan provides a grounding
for strategic funding decisions and priorities within the national program and helps foster innovation
toward commercially viable fusion reactor designs. Additionally, a national fusion energy goal guides
national research and innovation programs, helps to engage all participants in the fusion endeavor in the
United States, from universities, to national laboratories, to industrial partners, and sets the national
priorities of our partners, enabling them to develop key areas of unique expertise.
Many reasons justify the readiness to develop a national strategic plan for fusion energy. Throughthe work of the United States and other nations, the ITER project is “back on track,” and confidence has
increased that burning plasma science will succeed in its mission. In contrast to the strategic planningproposed more than a decade ago, today the international community is stronger. The world effort has
achieved rapid scientific and technical progress, and significant efforts are now underway by ourinternational partners to move fusion beyond ITER toward commercial fusion energy. If the United States

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seeks to maintain a leading role in the pursuit for abundant fusion power, the development of a national
strategic plan for fusion energy that spans several decades is necessary.
Most importantly, the reason behind our committee’s recommendation is scientific progress,
technical readiness and the opportunities presented by recent advances in fusion-relevant technologies.
Understanding of toroidal magnetic confinement is now highly advanced: performance beyond the ITER
baseline can now be predicted and new science shows how advanced knowledge and simulation can beused to speed fusion development. Additionally, new technologies (largely developed outside fusion)
show great promise to reduce the size and cost of fusion power systems and reduce the cost of fusion
research and further progress. Today, with many of the complex physical processes of magneticallyconfined plasma becoming better understood and the first phase of ITER construction more than half
complete, the most critical fusion science research needs are interdisciplinary, combining burning plasma
science with materials science, fusion nuclear science, and engineering science. These interconnectedscience challenges require a comprehensive strategic plan that looks beyond the demonstration offeasibility expected with the ITER device and addresses all of the challenges for developing fusion power.
With the initial operation of ITER scheduled to begin within a decade and with the expectation that
controlled fusion will be demonstrated in ITER, now is the right time for the United States to develop
plans to benefit from its investment in burning plasma research and take leadership in the development offusion electricity for the nation’s future energy needs
TOWARD FUSION ELECTRICITY: THE COMPACT FUSION PILOT PLANT
The committee’s two main recommendations address the nation’s strategic interest in realizing
economical fusion energy in the long term. First, as described in Chapter 3, the United States should
remain an ITER partner as the most cost-effective way to gain experience with a burning plasma at thescale of a power plant. Second, as described in Chapter 4, the United States should start a national
program of accompanying research and technology leading to the construction of a compact pilot plant
which produces electricity from fusion at the lowest possible capital cost. Implementation of both
recommendations require essential research using facilities and programs within the United States andcontinued active partnership with the international effort.
The committee considered several strategic pathways for the nation’s long-term demonstration offusion electricity. The objective of each path was fusion electricity, but the size, priority, and number of
research facilities were different. For example, a Fusion Nuclear Science Facility (FNSF) does not need tomake electricity, but instead focuses on the materials science and fusion nuclear science to develop
materials that can survive the harsh environment surrounding a fusion system and it enables scientists tounderstand and control the operation of a burning plasma for many days. However, a FNSF would need to
be followed by a second, larger facility to demonstrate fusion electricity. Other nations are pursuing alarge, next-step fusion device, called a Demonstration Fusion Power Plant (DEMO).1,2,3 A fusion DEMO
would be capable of producing electricity, operating with a closed fuel-cycle and be the single step
between ITER and a commercial reactor. This definition of DEMO calls for larger devices with themission to produce significant net electricity, establishing routine electricity production and maintenancein order to convince utility companies (and other associated investors) that all aspects of the power source
are credible, reliable, safe, and ultimately profitable. Previous committees of the National Academies andof FESAC have recommended that the United States develop a strategic plan leading to either an FNSF or
to a DEMO. By contrast, this committee’s recommendation recognizes the advantages for a reduced cost
pathway to fusion energy demonstration and the scientific and technical opportunities that make thispathway possible.
Based on scientific progress and the expectation of innovations in technologies that will decrease
the size of the magnetic fusion reactor and, as a consequence, also reduce both the capital-cost andconstruction time, the committee’s strategic guidance for the United States is to target a pilot plant
producing power similar to the power levels expected in ITER but in a device much smaller in size and
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cost and employing design improvements that allow net electricity production. The recommended
strategy is faster and less costly than a two-step approach that requires both the construction of an FSNF
and a follow-on DEMO device to produce electricity. The recommended strategy is also less costly thanthose proposed by other nations, which involve a single large DEMO device. This is because the goal of
the compact fusion pilot plant is to incorporate science and technology innovations into a single facility,with a staged research plan, that will produce electricity from fusion at the lowest possible capital cost.
This compact fusion pilot plant would be a pre-commercial research facility with a burning
plasma at its core and surrounded by a blanket to capture fusion heat and neutrons. In addition to the
production of fusion electricity, the pilot plant would ultimately be capable of uninterrupted operation forweeks and produce tritium, the fusion fuel, from lithium-containing blankets that surround the plasma.
The compact pilot plant would be a staged facility and constructed at lower capital cost than previously
consider for fusion demonstration devices. The first stage will establish the capability of uninterrupted
operation at high-power density in a compact device. The second stage would operate at high fusion
power and demonstrate the safe production and handling of the tritium fuel required for sustained power.
As a pilot plant, its purpose will be learning, but the knowledge obtained would be sufficient for the nextstep to be commercial fusion power systems.
By starting a national research program toward a compact pilot plant, critical science andtechnology research can be ready in time to use the knowledge learned from ITER operation todemonstrate electricity production by mid-century.
2020-2035: REMOVING THE BARRIERS TO LOW-COST FUSION DEVELOPMENT
The cost of fusion electricity is driven principally by its capital cost and by how many hours theplant can run each year. Key to the achievement of low-cost fusion development are four researchchallenges: (1) the fusion power density should increase beyond that obtainable in ITER, (2)uninterrupted steady-state operation needs to be demonstrated while learning how to handle reliably thehigh levels of heat escaping from the plasma, (3) innovations should be encouraged and developed tosignificantly reduce the size of the fusion power system, improve component lifetime, simplify
maintenance, and lower construction cost, and (4) blanket technologies should be developed and tested toefficiently and safely breed tritium and extract high quality heat.
Resolving these barriers to low-cost fusion development will require the design and operation of
new facilities and continued engagement in the international effort. Facility decisions should be guided bycost-effective opportunities to achieve critical program goals and by unique opportunities for worldleading contributions. As the research portfolio evolves in time, existing research facilities are phased out
as new ones are implemented. One of greatest needs is the control of a continuous high-pressure compact
plasma, which will likely require a new intermediate-scale research facility in the United States toestablish its feasibility. Another significant challenge is the qualification of the materials and componentsthat surround the plasma and are exposed to fusion irradiation. One of the greatest opportunities is for theUnited States to take a leading role in the engineering sciences for high-critical-temperature
superconductors for fusion purposes.
This national research effort aimed at low-cost fusion development not only addresses U.S.
strategic interest in realizing economical fusion energy in the long term but also contributes to several
national science and technology goals in high-heat flux material science, advanced nuclear science, andhigh-field superconducting magnets.
Based on the input received by the committee and the committee’s study, the national program
should contain several program elements.

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Extending the Frontier of Burning Plasma Science
The U.S. fusion program has been a key contributor to the physics basis for ITER design andoperation. Participation in ITER provides the most timely and cost-effective opportunity for the U.S. tobenefit from the science and technology of the burning plasma regime. In the 2020-2040 period, the U.S.
program, through its domestic facilities and in collaboration with international partners, will continue
playing a key role in burning plasma studies and efforts to fully exploit the capabilities of the ITER
facility. Alongside ITER participation, a key program element is the development of scenarios that deliver
both higher levels of fusion power gain (i.e. Q > 10) and the achievement of high-power gain at lower
plasma current in ITER. The high priority placed on well diagnosed plasmas in the U.S. coupled with
continued U.S. leadership in developing physics-based models will provide the U.S. with uniquecapabilities not only to improve the understanding of reactor-grade plasmas but also to use thisunderstanding for improving the performance of fusion systems beyond ITER. Continued involvement in
the International Tokamak Physics Activity (ITPA) and future international activities coordinatingburning plasma research should remain a U.S. priority.
Sustaining High Fusion Power Density with High Plasma Confinement
The U.S. has long been a world leader in the development of high performance, steady-statecapable scenarios. The planned capabilities of DIII-D and NSTX-U will remain world-leading indeveloping the feasibility of high performance, fully non-inductive scenarios. This involves researchestablishing scenarios combining high bootstrap current fraction, compatible divertor configuration, andhigher-efficiency current drive technology.
Recent advances in the U.S program, motivated by theoretical studies, point to new researchelements that not only offer the U.S. distinct leadership opportunities but also potentially lead to morecost-attractive fusion systems, a central theme of this strategic plan. The U.S. program in 2020-2035
should focus on these potential breakthroughs through a program to quantify the benefits of such ideas.
Early in this period, planned upgrades to DIII-D and NSTX-U should provide sufficient capability to test
the basic aspects of the underlying ideas and establish the feasibility of steady-state tokamak operation
with good power-handling capability. However, either substantial upgrades to these facilities and/or a
new facility are needed to extend these results to burning-plasma-relevant conditions where the selfconsistency of transport, stability, current drive, and compatibility with a reactor relevant boundary
solution can be assessed. Note that detailed models predict that the highest performance (and hence
highest power density) will be achieved with optimal shaping of the plasma (including aspect ratio,
triangularity, and elongation). DIII-D and NSTX-U are well positioned to provide key information on the
choice of the required parameters. The committee cannot now determine whether the research needs
outlined here require an entirely new facility or an upgrade of an existing facility. The details of the nextstep magnetic fusion research facility should be developed through a coordinated community process that
includes consideration of multiple mission elements. However, the objective of this facility should be theestablishment of the science and technology needed for uninterrupted, high-power-density plasma
confinement at a compact size. The resulting upgrades or new facility should be designed, fabricated, andoperated by a national team.
Power Exhaust Solutions for High-Power Density Fusion Systems
A key enabling element of any U.S. strategic plan should be the development of power exhaust
solutions and materials that can handle the very high heat flux intrinsic to these systems. In the UnitedStates, DIII-D and NSTX-U have world-leading diagnostic sets and the ability to vary divertor conditions
over a wide range. Additionally, ITER will offer a significant opportunity to assess boundary solutions at

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heat flux levels much higher than in presently available devices and that therefore should be an integral
part of this plan.
However, a key aspect of projecting these solutions to devices beyond ITER is the ability toconfidently predict the divertor and first wall configurations compatible with very high plasma heat andparticle fluxes while preventing material contamination of the burning plasma core. Because projecting
boundary solutions for future devices is quite uncertain, a key aspect of any plan going forward is to
reduce the predictive uncertainties through a science-driven, model validation approach to elucidating key
features of the boundary solution and identifying phenomena that are not captured properly bymeasurement or by simulation. Additionally, several innovations to improve the heat flux handlingcapability of the divertor, called “Snowflake,” “Super-X,” and “Small-Angle Slot” divertors andincluding innovative material choices (e.g., liquid metal walls) should be assessed. While each of thesecan be developed and tested in existing facilities, confidence in such solutions for future devices may
require substantially increased capability in order to explore heat fluxes and their dissipation at the highlevels and densities expected in fusion power systems. For this reason, an additional requirement of thenext-step magnetic fusion research facility discussed above should be tests of advanced divertor schemeswith robust power and particle handling capabilities applicable to the compact fusion pilot plant.
Large-Bore High-Temperature Superconducting Coils
Recent advances in the technology of high-critical-temperature superconductors (HTS) have thepotential of reducing the cost of fusion energy and providing unique benefits for increasing theperformance limits of fusion systems including very high current density, operation at much higher
magnetic field, and the potential for improved maintenance, for example through jointed, demountable
magnets.
In order for the U.S. program to be in a position to utilize HTS magnet technology on the timeline
articulated in this strategic plan, a development program should begin as soon as possible. Early stages ofthis effort should focus on assessing relevant means to produce coils from the HTS conductor andpossible performance degradation as the bore size is increased. The United States should consider hostinga toroidal magnet test facility similar to the Large Coil Test Facility (LCTF) that was hosted by ORNL
and facilitated by an implementing agreement of the IEA-FPCC. The LCTF was a successful partnershipof magnet scientists from the United States, Switzerland, Europe, and Japan and between national
laboratories and industry. Just as the LCTF established the engineering science for low-temperature
superconductors, like those used in ITER, this new facility would invite proposals from industries aroundthe world and establish the engineering basis for higher-field high-temperature superconductors for fusion
magnets.
Materials that Deliver High Performance and Long Lifetime
Since the economics of fusion power depend critically on the amount of time available for power
production, the lifetimes of materials are a critical factor in reactor design and operation. Rapid material
degradation due to plasma erosion or neutron bombardment could severely limit the benefit that could be
gained from a high-power core/boundary solution. In this regard, the presence of 14 MeV neutrons andtheir deleterious effects are very specific to the fusion environment and therefore data quantifying such
effects is sparse.
To resolve key materials challenges, two branches of research are envisioned. First, the effect oflong-term exposure of plasma facing materials to divertor-like conditions needs to be understood, leading
to the development and qualification of materials that meet the stringent demands of a fusion system.
Second, these plasma-facing materials as well as structural materials that can maintain under high neutron
fluence their critical properties, transfer properties, tensile strength, and fracture toughness, would need to
be developed, tested, and qualified. The development of these materials requires a better scientific
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understanding of the processes that modify material properties. This understanding requires continued
improvement in theory, numerical simulations, and experimental capabilities.
During the 2020-2035 period, the U.S. program should develop plans for new facilities to addressthese materials research needs. First, the U.S. would bring online a non-nuclear material test facility thathas the capability to expose materials to relevant heat fluxes over the range of plasma conditions expectedin future fusion systems. Such a facility (similar to the proposed MPEX facility) would provide a uniquetest bed for new materials including composites and liquid metals. Second, and later in this period, theU.S. would develop a facility and research plan leading to construction of a fusion neutron source for tests
of modest-scale-sample materials and components in a 14-MeV neutron environment. This researchshould consider the benefit, cost, and timing of nuclear materials testing using a spallation source. A new
fusion neutron source would be a world-leading scientific instrument, enabling U.S. and international
researchers to explore effects not possible at any other facility and would complement the efforts of othernations that are focused on exposure of smaller material samples (for example, a beam-driven neutron
source like IFMIF). Delivering the necessary capabilities in a cost-attractive manner should be a key
factor in the choice of concept.
Blanket Systems that Breed Tritium and Extract High Quality Heat
A very important component of any fusion energy system will be the ability to efficiently breed
and extract tritium and convert the fusion energy to high quality heat for electricity production. In
particular, achieving sufficient tritium breeding and extraction efficiency is absolutely critical to thesuccess of fusion given the very limited availability of tritium. As noted above, the worldwide fusion
program has developed plans for significant technical development of blanket systems through the ITER
Test Blanket Module (TBM) program and other dedicated research worldwide. The U.S. should invest
sufficiently in blanket R&D to ensure that we are capable of leveraging this international investment
while addressing specific issues associated with a compact fusion reactor. A decision whether or not tobecome a supporting participant in the TBM program would be part of a national evaluation of research
options considering the time-line for the final design, licensing, and installation of TBM modules.
Examples of research issues to be addressed in the national program include heat generation and removal
at very high-power density and potential new blanket solutions that are predicted to achieve very highthermal efficiency and provide a path to tritium self-sufficiency.
In addition to the research elements above, the committee views other considerations as important
guidance for the national strategic plan for fusion energy.
Effective Leadership and Participation in the ITER Research Program
ITER will provide the first laboratory for studying the behavior of a burning plasma, and as such
will offer an unprecedented opportunity to United States fusion scientists to move into what we all
acknowledge as the next frontier in our field. The U.S. fusion research community should be prepared to
fully embrace that opportunity. Maintaining technical leadership is essential for that readiness, but it isjust as important to optimize the organization of the ITER research program to facilitate that participation.
This will eventually be decided in negotiation between the Domestic Agencies and the ITER Organization
Central Team, but a USBPO Task Group has already prepared “Recommendations for ITER
Experimental Operation, U.S. Team Formation and Participation” to help guide the process.
Maintaining Readiness to Move to Next Steps After ITER
The United States has not constructed a large facility since the 1990s, when Alcator C-Mod and
NSTX came into operation. Several of our international partners in ITER are in the midst of a long period
without a major domestic tokamak facility, and much of their expertise developed in the past has been lost
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through attrition. If the United States wishes to maintain scientific and technical leadership in this field,
the nation needs to maintain the skills to design, construct, and operate a world-class fusion researchfacility. This potential for leadership should engage the participation of universities, national laboratories,
and industry in the realization of commercial fusion power for the nation.
FUSION SCIENCE PREDICTIVE MODELING AND EXASCALE COMPUTING
Fundamental to this strategic plan is the continued role of theory, simulation, and computation in
motivating innovative approaches to improving the prospects of fusion energy. This encompasses
research in burning plasma physics, materials science, fusion nuclear science and engineering sciences.
These efforts benefit tremendously from the availability of exascale computing capabilities to tackle
complex problems and high-capacity computing for scoping studies, machine learning, and data analysis.
Utilizing these tools, validation of important physics models should be a strong emphasis of the R&D
program supporting this plan.
The creation of the DOE Exascale Computing Project4 in FY2017 has provided the impetus forthe realization of a high-fidelity Whole Device Model (WDM) of fusion plasma applicable to a highperformance advanced tokamak regime, integrating the effects of turbulent transport, plasma collisions,and neutral particles, energetic particles, plasma-material interactions, as well as heating and current
drive. At the present time, the Exascale Computing Project is one of the largest projects in the U.S. DOE
Office of Science.5 Whole device modeling holds the promise of being a powerful predictive tool for
current and future fusion devices that will access hitherto unrealized plasma regimes, and has the potential
to produce scientific discoveries of new and emergent behavior of burning plasmas that have been so far
studied piecemeal. The project will be developed in a computational ecosystem that brings together
plasma physicists with applied mathematicians, computer scientists, and other application scientists using
a diverse range of software technologies and several co-design centers. The continued growth of exascalecomputing, which is supported by U.S. DOE/ASCR, is a valuable opportunity for United States fusion
scientists and represents at the present time the largest project in the Office of Science,
PROMOTING DISCOVERY IN FUSION ENERGY SCIENCE AND ENGINEERINGTo reduce risk and encourage discovery, the long-term research strategy should develop
promising innovations in burning plasma science and fusion engineering science that can accelerate
fusion development or improve and reduce the cost of fusion as a source of electricity. New insights anddiscoveries are expected to occur in all of the interconnected research in burning plasma science,materials science, fusion nuclear science, and engineering science. But the committee feels that researchon less developed and therefore more speculative topics should continue to be a feature of the U.S.
program. This might include some research previously provided by the ARPA-E ALPHA Program [Ref]that supports the national program leading towards a compact fusion pilot-plant. An ongoing program
promoting discovery in fusion energy science would be similar to the existing U.S. DOE/FES program in
Discovery Plasma Science, except any program in Discovery Fusion Science would need to be open to
the possibility of intermediate scale research facilities involving multiple institutions. While someresearch would be supported by competitive peer review, the selection of intermediate scale facilities
should follow a conceptual design effort and be guided by the evaluation of a national team of experts.
The recent FESAC report Transformative Enabling Capabilities for Efficient Advance Toward
Fusion Energy listed several revolutionary ideas that would “dramatically increase the rate of progress
toward a fusion power plant.” These breakthroughs include substantial increase in fusion performance,
simplification of fusion enabling technologies, reduction in fusion system cost or time to delivery, or
improvements in reliability and safety. Example transformative enabling capabilities (TEC) include: (1)advanced algorithms, like machine learning and integrated data analysis, to improve the methods tocontrol a burning plasma and to facilitate predictive understanding from advances in exascale computing,
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(2) high critical temperature superconductors, (3) new material designs, advanced fabrication methods,
and additive manufacturing offering the potential for local control of material structure, and (4) novel
technologies for tritium fuel cycle control. Each of these TECs presents a tremendous opportunity toaccelerate fusion science and technology toward power production. Dedicated investment in these TEC
areas for fusion systems is needed to capitalize on the rapid advances being made for a variety of nonfusion applications so that their transformative potential for fusion energy is fully realized.
In addition to the FESAC Report on Transformative Enabling Capabilities, the committee waspresented with two additional examples for promising discovery in fusion energy science. These aredescribed below.
“Hidden Symmetry” versus “Axisymmetry”
Magnetic fusion energy requires a toroidal confinement region with strong magnetic field tocontain the high-pressure plasma. As described in Chapter 2, the tokamak configuration is mostsuccessful and best understood configuration for magnetic fusion energy. ITER is also a tokamak as are
the two major United States research facilities, DIII-D and NSTX-U. While tokamaks use relatively small
non-symmetric magnetic fields, the other configuration, called the stellarator, is strongly non-symmetricby design. The two largest stellarators are the Japanese Large Helical Device (LHD) and the German
Wendelstein 7-X (W7-X) stellarator. Both of these experiments are built with superconducting magnets,
and both are conducting successful ongoing investigations of the potential for uninterrupted magnetic
confinement for fusion with a more complex, non-symmetric set of magnets. United States scientists areactive participants in the German W7-X experiment.
The stellarator has benefitted from advances in theoretical understanding leading to improved
particle confinement at high plasma temperature. This improvement is achieved through careful
optimization of the shape of the magnetic field. The present day focus of the United States stellarator
program creates a “hidden symmetry” of magnetic field, called the quasi-symmetric approach. A
stellarator with a “hidden symmetry” has favorable single particle orbits and pressure driven currents thatare similar to axisymmetric tokamak configurations. Validating the effectiveness of these optimization
approaches defines a major element of the existing experimental stellarator program. Presently, theworld’s only stellarator with hidden symmetry is the Helically Symmetric Experiment (HSX) located at
the University of Wisconsin. While the HSX program has definitively demonstrated neoclassicalconfinement of thermal electrons, the small size of the HSX device has prevented the investigation ofthermal and energetic ion confinement and plasma flows in quasi-symmetric magnetic systems. Because
the behaviors of a plasma confined with “hidden symmetry” informs the predictive capability of all
magnetic configurations, including the axisymmetric tokamak, a unique opportunity for discovery exists
through exploration of a larger stellarator experiment where “hidden symmetry” can be evaluated at adevice size sufficient to fully investigate confinement effectiveness and understand how plasma flow
physics can positively impact turbulent transport, MHD physics and impurity confinement.
Beam-Driven Plasma Neutron Source versus Fission-Based Neutron Source
A key facility needed to prepare for initial operation of a compact fusion pilot plant is a
prototypic 14 MeV fusion neutron source capable of testing fusion blanket concepts, as well as to obtainthe neutron-induced degradation data required for the initial stage of pilot plant licensing. The UnitedStates fusion nuclear engineering community has long advocated a dedicated facility with a reliable
steady-state plasma source for this purpose. Concerns about the costs of fusion neutron sources need to beaddressed in arriving at the most fusion neutron source for cost-effective testing. Various approaches forblanket and materials testing are characterized by the useful irradiation volume and the neutron energy
spectrum. Research facility options include fast fission reactor test facilities, accelerator-based ion
sources, or somewhat non-prototypic neutron spectra involving spallation neutron sources. A beam-driven
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plasma source may provide a lower cost approach while also providing a prototypic neutron spectrum. A
beam-driven plasma source consists of a relatively small magnetic confinement device that is operated
continuously by injecting energetic neutral beams of deuterium and tritium atoms that generate a fusion
neutron spectrum for testing. A low-cost linear mirror device, called the gas dynamic trap (GDT), as well
as beam-driven tokamak or alternate plasma-based, accelerator-based, or innovative fission reactor
facilities, should be evaluated to determine which may provide an innovative solution to fusion’s nuclear
testing needs.
Other opportunities for discovery in fusion energy science having high scientific merit andtechnical readiness should be promoted provided that they significantly advance burning plasma science,materials science, fusion nuclear science, or engineering science.
RESPONDING TO A UNITED STATES DECISION TO WITHDRAWN FROM THE ITER
PROJECT
Chapter 3 describes the importance of burning plasma research, explains why continued
participation as an ITER partner is important to United States fusion energy research, and describes how
ITER participation will inform the design of a compact fusion pilot plant as a new element of the UnitedStates magnetic fusion program. The benefits of continued U.S. participation in ITER are compelling forseveral reasons: (1) ITER is the only existing experiment with a mission to explore burning plasma
physics at the power plant scale, (2) ITER research is currently a major focus of the U.S. fusion research
program, (3) the development of national expertise in burning plasma science requires the hands-on
participation by experts, (4) ITER construction is more than half complete, and the first plasma
experiments are expected to begin in less than ten years, and (5) as an ITER partner, the United States
fully shares in the technology that will establish the feasibility of fusion while providing only a fraction of
the costs. However, should the United States decide to end its participation in the ITER project, the needto address key burning plasma physics issues remains. Advancing toward a national fusion energy goal
requires progress in all of the interconnected program elements needed for a low-cost demonstration offusion electricity: burning plasma science, materials science, fusion nuclear science, and engineeringscience.
The committee’s response to the scenario in which the U.S. is not an ITER partner is based on the
scenario in which the U.S. continues participation in the ITER project. Irrespective of whether the U.S.
remains an ITER partner, the committee recommends the United States should start a national program ofaccompanying research and technology leading to the construction of a compact pilot plant at the lowest
possible capital cost and the production of electricity from fusion. In this way, the committee’s long-term
strategic guidance is generic and applies to both scenarios.
All previous strategic plans reviewed by the committee call for construction and operation of aburning plasma experiment and the demonstration of scientific and technical feasibility prior toconstruction of a facility capable of electricity production. This committee concurs with this assessment.
A burning plasma experiment is a critical next step toward the realization of fusion energy, and thescience and technology gained from a burning plasma experiment, like ITER, will answer key questions
needed to design a compact pilot-plant. The study, control, and manipulation of a burning plasma will
give scientists their first opportunity to demonstrate many technical capabilities needed by an energyproducing magnetic fusion device. With access to a burning plasma experiment, scientists will have themeans to answer fundamental questions pertaining to energetic alpha particles created by fusion reactions,plasma transport processes in fusion reactor conditions, methods to control of plasma transients, divertor
science, and the integrated scenarios that simultaneously test the requirements for stability, confinement,
fuel purity, and compatibility with plasma-facing components needed for a fusion energy source. If theUnited States wishes to take leadership in fusion energy development and pursue a program toward acompact pilot plant, national expertise in burning plasma science needs to be developed through hands-on
operational participation and scientific study by U.S. fusion scientists.
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For the scenario with the United States remaining an ITER partner, research toward the second
goal of compact, attractive fusion power generation will build upon the ITER experience and focus onhigh power density plasmas, and the integration of core and edge physics in the regime required for acompact fusion pilot plant. However, if the United States were to withdraw from ITER, the United States
would need to design and construct a larger and more ambitious research facility with a capability to
explore burning plasma science with deuterium-tritium operation. The direct study of high-gain burning
plasma physics and access to research opportunities necessary to evaluate long plasma duration andburning plasma control methods are central long-term goals of the United States program. As analternative to ITER, the expanded fusion nuclear program for a high-power density burning plasma
facility would be expensive for the United States to undertake without international support, and it would
likely delay progress in the field. Such an expanded fusion research program, however, would be criticalfor directly addressing the physics of a strongly coupled burning plasma, and addressing the key
challenges discussed above.
A decision by the United States to withdraw from ITER would make international collaboration
far more difficult. Nevertheless, the United States would need to explore other avenues for collaborationand international cost-sharing, and important avenues for collaboration may still remain. In particular, theUnited States has already been engaged in the design of the China Fusion Energy Test Reactor (CFETR),
and if that collaboration could be maintained, it would provide valuable insight on fusion technology.
However, such collaboration, particularly in the event of a U.S. withdrawal from ITER, would require theUnited States to have its own vibrant fusion program with value to offer to those collaborating with theUnited States.
Given the resources required, the primary initial focus of a U.S. program without ITER
participation would still be a high-power density burning plasma tokamak. However, the mission for thisnew facility would need to be expanded to include study and control of self-heated burning plasma.
Design studies for such an experimental device, building on results from new experiments on DIII-D and
NSTX-U, state-of-the art theory and simulation, and possibly technology innovations, would need toshould begin as quickly as possible in response to a United States decision to withdraw from ITER. Thesedesign studies would need to include the licensing and facility requirements for safe handling of tritium.
Once constructed, this new facility would give United States fusion scientists the necessary means tostudy burning plasma science and technology and to maintain progress toward the long-term developmentof commercial fusion power.
SUSTAINING THE NATIONAL PROGRAM
The demonstration of fusion electricity is a long-term undertaking, requiring progress at bothnational and international levels and sustained support. Besides the scientific and technical challenges tocontinued progress, fusion energy research needs solid support from the broad scientific community andthroughout the political system. The 2009 NRC report A Review of the DOE Plan for U.S. Fusion
Community Participation in the ITER Program recommended that steps should be taken to “seek greater
U.S. funding stability for the international ITER project to ensure that the United States remains able toinfluence the developing ITER research program, to capitalize on research at ITER to help achieve U.S.
fusion energy goals, to participate in obtaining important scientific results on burning plasmas from
ITER, and to be an effective participant in and beneficiary of future international scientificcollaborations.”
The first half of the committee’s recommendations is continued participation in the ITER project
as the nation’s primary experimental burning plasma component within a balanced long-term strategicplan for fusion. The committee concurs with the conclusion from the Secretary of Energy’s Report toCongress in May 2016, “ITER remains the best candidate today to demonstrate sustained burning plasma,
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will inform accompanying research and technology programs needed to progress beyond ITER to acommercial fusion reactor.
The second half of the committee’s recommendations recognizes that if the United States is to
profit from its share of the ITER investment, the nation’s strategic plan for fusion should combine its
ITER experience with the additional research needed to realize fusion. In addition to burning plasma
science, the interconnected research in materials science, fusion nuclear science, and engineering scienceshould be expanded. Without this additional research, the United States risks being overtaken by othernations as they advance the science and technology required to deliver a new and important source ofenergy.
BUDGET IMPLICATIONS
The committee was asked to consider the budget implications of its guidance. Estimates were
examined for the cost and schedule for the two main research activities: (1) construction and operation of
the ITER burning plasma experiment and (2) a national program of accompanying research anddevelopment leading to the construction of a compact fusion pilot plant. The committee also examined theschedule and budget implications of a decision by the United States to withdraw from the ITER project.
Because the committee’s long-term strategic guidance covered the next several decades, all cost andschedule estimates are necessarily approximate. Implementation of the committee’s strategic guidance
will require significant planning and thought by the fusion research community, involvement withinternational partners, and oversight by the U.S. Department of Energy. Additionally, because thecommittee’s strategic plan involves research and technology development over several decades, theimpact of unanticipated discoveries, breakthroughs, or technical setbacks that would influence theschedule and cost of the strategic plan could not be determined.
With the baseline cost and schedule for U.S. contributions to ITER’s first plasma subproject now
formalized, the committee’s recommendations imply a sustained national funding for more than two
decades at a level that is about $200 million higher than the presently enacted funding levels. About halfof this additional amount is required to meet ITER commitments and the other half is needed to launch
the science and technology supporting the research leading to a compact fusion pilot plant. Appendix Hsummarizes the input used by the committee in its considerations of the budget implications of its
recommended strategic plan for U.S. burning plasma research.
Based on information received, including the Updated Long-Term Schedule for ITER, the 2016
DOE Report to Congress,6 and the 2017 DOE, Project Execution Plan for U.S. ITER Subproject-1,7continued U.S. participation in the ITER project requires additional annual funding near $100 million,
representing half of the required incremental funding.
The start of a national program of accompanying science and technology leading a compact pilot
plant at the lowest possible capital cost will also require additional funds of $100 million annually,
representing the other half of the required incremental funding. This estimate is based on recent reports of
the U.S. DOE FESAC, including 2014 Report of the subcommittee for Priorities Assessment and Budget
Scenarios,8 the 2013 Report of the subcommittee on the Prioritization of Proposed Scientific User
Facilities for the Office of Science,9 and the 2013 Report of the subcommittee on the Priorities of theMagnetic Fusion Energy Science Program.10 All of these reports recommended additional funding toaddress the full range of scientific, technical, and engineering challenges for fusion energy. They also
recommended an evolution of the research portfolio as existing research facilities are phased out and newones are implemented.
Programmatic decisions for new facilities and programs mentioned in this report should be basedon cost-benefit analysis and technical input from the U.S. fusion research community as recommended in
Chapter 6. If the required engineering and science studies begin soon, new world-class research facilities
could be available to enable resolution of the critical issues needed to finalize the design and begin
construction of a compact fusion pilot plant having the lowest possible capital cost. Such a program with
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a cost-attractive goal for the demonstration of fusion electricity would also provide important scientificopportunities for U.S. researchers and U.S. industry and deliver technical know-how to the nation's effort
to provide abundant fusion power.
In summary, based on information received and described in Appendix H, including the updated
long-term schedule for ITER participation and previous strategic planning efforts of the U.S. DOE
FESAC, the committee expects the implementation of its recommendations, including both continued
participation in ITER and the start of a national research program for a compact pilot plant, to require anannual funding level about $200 million larger than presently enacted levels, about half required to meet
ITER commitments and half needed to launch the science and technology supporting the research leading
to a compact fusion pilot plant. This funding would need to be sustained for several decades.
NOTES
1. K. Tobita, et al., “Overview of the DEMO conceptual design activity in Japan,” Fusion Eng Des 1(2018).
2. K. Kim, et al., “Design concept of K-DEMO for near-term implementation,” Nuclear Fusion 55,
053027 (2015).
3. G. Federici, et al., “Overview of EU DEMO design and R&D activities,” Fusion Eng Des 89, 882(2014).
4. See Exascale Computing Project online at https://www.exascaleproject.org .
5. A. Bhattacharjee, et al., Strategic Role of Exascale Computing in U.S. Magnetic Fusion Research,
White paper submitted to the committee.
6. U.S. Department of Energy, U.S. Participation in the ITER Project, Report to Congress,
Washington, D.C., May 2016,
7. Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, U.S.
DOE/OS/FES (January, 2017).
8. DOE, Report on Strategic Planning: Priorities Assessment and Budget Scenarios, (October 2014),
online:https://science.energy.gov/~/media/fes/fesac/pdf/2014/October/FESAC_strategic_planning_rept_dec14.p
df
9. DOE, Report of the FESAC Subcommittee on the Prioritization of Proposed Scientific User
Facilities for the Office of Science, (March, 2013), available online:
https://science.energy.gov/~/media/fes/fesac/pdf/2013/FESAC_Facilities_Report_Final.pdf
10. DOE, Report of the FESAC Subcommittee on the Priorities of the Magnetic Fusion Energy
Science Program, (January, 2013), available online:
https://science.energy.gov/~/media/fes/fesac/pdf/2013/Final-Report-02102013.pdf

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6Comments on Organizational Structure and Program Balance
Implementation of the recommended strategic plan for United States magnetic fusion energy
research will require an expanded organizational structure for the U.S. DOE Office of Fusion Energy
Sciences (OFES) with more deliberate planning, regular opportunities for input from the researchcommunities, coordination of research efforts in burning plasma science, materials science, fusion nuclear
science and technology, and the engineering sciences needed to realize an economical pathway to fusion
electricity for the nation.
Three primary organizational and program changes are described below: (1) a new division
within the U.S. DOE Office of Fusion Energy Sciences, (2) adoption of a long-range strategic plan, and(3) strong engagement from the fusion energy science research community. The expanded organizational
and program management structure within the OFES is needed to emphasize burning plasma science inpreparation of ITER studies and to coordinate the research and technology within a growing national
program that looks beyond ITER. Importantly, this structure enables the comprehensive, long-range planthat is needed to carry out the accompanying research aimed at a low-cost, compact fusion pilot plant.
This includes support for the fusion technologies that will enable a compact, low-cost pathway to fusion
demonstration and strengthening communication with the multi-disciplinary research communities.
Comments are also made regarding (1) safety and licensing standards for fusion energy researchfacilities, (2) the health of the U.S. fusion research program, (3) the importance of continued participationin the larger international effort, (4) the need to encourage growth of private sector capabilities in fusionenergy technology, (5) the value of cross-disciplinary partnerships in related science and technology
efforts, and (6) the importance of public outreach to better communicate the long-term potential for
economical fusion energy and to better engage students and educational institutions in the integrated
science, technology, engineering, and mathematics at the foundation of fusion energy science.
This chapter concludes with six findings and seven recommendations aimed to guide theimplementation of an expanded U.S. DOE FES research program and strengthen community participationin the burning plasma science, materials science, fusion nuclear sciences, and engineering sciences
needed to realize an economical pathway to fusion electricity for the nation
ORGANIZATIONAL STRUCTURE AND PROGRAM MANAGEMENT
The pathway ahead for fusion development requires augmentation of ongoing burning plasma
research with the technology and engineering research required to enable fusion power systems. As
discussed in Chapter 2, in the last ten years, many of the complex physical processes of magneticallyconfined plasma have become understood, and there is growing confidence in the predictions of validated
computer simulations and models for burning plasma performance and in the promising new technologies
that have the potential for lower-cost approaches to fusion energy. As was also discussed in Chapters 4
and 5, the pathway ahead for fusion development requires augmentation of ongoing burning plasma
research with the technology and engineering research required to enable fusion power systems. The
demonstration of fusion electricity production will require continued innovations in the technology andengineering needed to sustain the plasma, manage the power exhaust, and take advantage of newtechnologies to breed tritium fuel and realize innovative approaches to reduce the size of the fusion pilot
plant. Progress calls for management and coordination of a multi-disciplinary effort to promote continued
innovations in those technologies that will reduce the cost of the fusion development path and to further
develop the knowledge, expertise and infrastructure needed to design a compact fusion pilot plant.
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Expanding the OFES Organization to Meet Program Needs
The current organizational structure for the U.S. DOE Office of Fusion Energy Science (OFES)
has been adequate to advance to the burning plasma, but is not well suited to accommodate the larger
scope. Currently, two divisions exist in OFES: “Research” and “Facilities, Operations, and Projects.” Thefirst has been a generator of ideas and exploration to assess the viability of different magnetic
confinement configurations, plasma behavior and characteristics needed for sustained fusion. The second
division attends to the oversight of existing projects. However, the committee finds that the current
structure is not readily adaptable to the expanded science scope and integration of the required
sophisticated technologies.
To achieve the necessary focus and coordination, the committee proposes strengthening theorganizational structure of the U.S. DOE OFES program to better focus on the two goals of the long-term
strategy. As discussed in Chapter 3, data and modeling/simulation associated with ITER experiments will
provide critical information to design the future pilot plant. Thus, the research division should be reorganized with an explicit focus on burning plasma research as a centerpiece of the division. As noted in
Chapter 4, a new fusion technologies division should be added to manage and organize research leading
to technologies required to improve and fully enable the fusion power system. Effective coordination
between the research, technology, and facilities divisions should be strongly emphasized by U.S.
DOE/FES leadership.
The goal of this new division would be to manage a portfolio of research tasks including
engineering studies of the compact fusion pilot plant that can guide and prioritize research needed to fully
establish the science and technology of the fusion power system. The purview of the subgroups within the
new U.S. DOE OFES division should include, for example, high-temperature superconducting (HTS)
magnets, structural materials, blanket, and tritium technologies. The revised organizational structure will
facilitate both technical innovation and coordination on interrelated elements within and between FES
divisions.
Ultimately, the realization of fusion energy as a source of electricity will involve the design andconstruction of complex facilities that rely upon continued development of the underlying enabling
technologies. Past research facilities for fusion energy science illustrate the significant boosts in capability
that result from state-of-the-art advancement of enabling technology. For example, advancement in glass
forming technologies were essential for the National Ignition Facility (NIF). Migration of inclusions fromthe crucibles into the glass had to be overcome, and continuous glass forming techniques had to be
developed in order to supply the quantity of high-quality optical glass needed. Similarly, advances in the
manufacturing of large niobium-tin (Nb3Sn) superconductors, as discussed in Chapter 2, were essential to
the success of the ITER facility and will result in the world’s largest superconducting magnet system.
Looking to the future, continued developments in the underlying enabling technologies arenecessary and should be supported. For instance, superconducting magnet technology that can operate ateven higher magnetic fields than possible with Nb3Sn conductor will be critical for compact and lowercost fusion power plants. New manufacturing methods are now able to fabricate complex material
structures that may result in extremely beneficial thermal and mechanical properties for fusion
applications. Similarly, it is not hard to imagine that materials research is also needed to develop a
tritium-breeding blanket in the wall facing the burning plasma.
In short, many transformative and innovative technologies listed in the 2018 report from the
FESAC Subcommittee on Transformative Enabling Capabilities1 may significantly improve theeconomics of fusion power systems. Strengthened program support within the U.S. DOE OFES is needed
to support the science and engineering that will lead to the technological leaps necessary for a fusion
machine.

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Adopting a Long-term Strategy Toward a Fusion Energy Goal
The United States fusion energy science program needs a long-term strategy that ensuresbalanced growth and integration, supporting a diversity of program elements that are inherently
interlinked through the national fusion energy goal.
Implementation of the strategic expansion recommended in this report will result in a research
program that combines burning plasma science, materials science, fusion nuclear science, and theengineering science needed for guiding, designing and ultimately constructing a compact pilot plant andgenerating electricity from fusion. The resulting research program in the United States begins with acurrent focus on burning plasma science and adds research elements that will fully enable a fusion powersystem. These include engineering of high-field superconducting magnets, fusion nuclear science and therelated technologies needed for the components surrounding a burning plasma and, notably, the fusion“blanket” that can breed tritium fuel and the materials science needed to engineer the structures that canwithstand the magnetic forces and neutron irradiation in magnetic fusion energy.
With any burning plasma effort, and especially with the multi-national ITER, the shift to “bigscience” at the international scale along with national facilities with specific and focused research
missions have implications for all areas of the U.S. fusion research community. As noted in the 2004
report of the NAS Burning Plasma Assessment Committee,2 as the U.S. fusion community enters theburning plasma era and ITER operation begins, the scale of even the largest national research facilities
effectively become “smaller-scale” programs having specific objectives that will be complementary to
ITER. During the next decades, research facilities will continue the trend toward national facilities that,
although are smaller than ITER, still addressing essential research tasks in the most cost-effective manner.
The committee’s strategy to realize a fusion plant will require new U.S. research facilities. In fact,
the experience in the design, construction and successful operation of major research facilities in the
United States will be critical in both the science mission and in establishing and maintaining global
leadership. Successful and efficient completion of new major facilities requires institutional knowledge inthe form of experienced scientists and engineers, and cannot be achieved solely by relying on theory or byreading research articles about facilities in other countries. The adoption of a new strategy for U.S. fusionenergy research will necessitate an evolution of major research facilities. These facilities should continue
to be world-class and serve the national fusion research community to develop scientific and technicalleadership in fusion energy science.
In a well-managed strategy, research priorities would be expected to evolve over time as researchquestions are answered and tasks are completed, laying the foundation for each new stage. The retirementof facilities that have served their intended purpose and the planning for new machines that will replacethem should follow priorities established through a formal structure that includes community-based
program reviews and strategic planning. The contributors from university and U.S. DOE and industry
research labs will give voice to the advances and challenges in their respective institutions that together
will inform major decisions as well as the direction of the program more broadly.
Strengthening Community Organization and Input
An expansion in the U.S. DOE OFES to support fusion science and technology beyond theburning plasma science will require coordination among multiple research communities and may include
scientific experts from U.S. industry and utilities. The current MFE community is largely rooted inacademic institutions, with key groups and facilities in nationally funded laboratories, with a growinginternational involvement through participation in ITER and collaboration on other international facilities.
This diverse nature is different in character than, for example, Inertial Confinement Fusion, which is
mission-driven by the national laboratories responsible for stockpile stewardship. While there are many
able contributors, the expanded research community is only beginning to be unified in the greater vision.

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To ensure incorporation of innovations and discoveries while making consistent progress toward the longrange fusion energy vision, the committee recommends changes to strengthen community engagement.
The current management structure of the Office of Science allows for input from the researchcommunity through advisory boards. These advisory boards are subject to the Federal Advisory
Committee Act (FACA) rules, which require providing the public with the opportunity to participate inboard meetings, where recommendations are discussed. Each advisory board is composed ofapproximately twenty individuals, selected for their expertise in the different areas critical to scientificand technical growth and management, including relevant university and laboratory personnel.
The Fusion Energy Sciences Advisory Committee (FESAC) is the advisory board for the OFES,
and according to its charter, meets and acts only when specifically tasked by the Office of Science toprovide advice. FACA rules dictate that FESAC restrict advisory comments to those directly responsive
to specific committee charges.
To achieve consistent long-range planning through the FESAC, the committee examined thepractices of other advisory committees within the Office of Science to identify those that may serve as amodel for OFES. For the U.S. DOE Office of Science High Energy Physics Advisory Panel (HEPAP), a
subcommittee called the “Particle Physics Project Prioritization Panel” (P5), was charged with making
recommendations on priorities of large facility projects, considering their projected costs. The first P5
report, issued in October 2003, described their role as the “guardian of the facilities roadmap.” P5 isconvened approximately every five years, including 2008 and 2013, to provide “long-range planning for a
10-year, and 20-year global vision.” For HEPAP, the process of soliciting input from the community
works fairly well because P5 prioritization takes that input into account along with fiscal constraints andthe need to balance large and medium size projects. HEPAP has the clear and explicit commitment of the
Office of High Energy Physics that the recommended priorities will be honored in funding decisions.
The committee recommends that the U.S. DOE/FES ensure the long-range U.S. strategic plan isdeveloped, regularly updated, and vetted by the community through a P5-like process that covers thedomestic and international facilities/programs. This effort should engage the professional societies
supporting the science and technology for fusion energy, including the American Physical Society
Division of Plasma Physics (APS-DPP) and the American Nuclear Society Fusion Energy Division(ANS-FED). In addition, defined events held at regular intervals will bring the U.S. magnetic fusionenergy research community together to build a unified national program.
The committee also finds that the magnetic fusion energy research community, itself, needs todevelop a culture that provides for broad, transparent input to the national program. Self-organizedcommunity workshops, or cross discipline community meetings organized by professional societies, canprovide important forums to vet ideas and should be encouraged by the leadership.
A recent successful example of magnetic fusion energy research community engagement is thepair of workshops held in Madison and Austin in 2017 that enabled a long-overdue discussion among
members of the plasma science community about collective research priorities and potential pathways tofusion energy. The workshops, organized by the grassroots U.S. Magnetic Fusion Research Strategic
Directions3 program committee, were well received by those who participated, and they contributed to thedevelopment of a shared vision of the field, although they lacked representation from some disciplinesthat will be critical to the development of fusion power plants. A strong consensus emerged from theworkshops that the science of magnetically confined plasmas has advanced sufficiently that a broadened
national effort encompassing the science of fusion energy technologies in addition to burning plasma
science is now appropriate.
Another example in this electronic age, is the online forum that was established4 by a selforganized group of “Early Career Fusion Scientists” (ECFS) that took inspiration from the workshops. A
poll conducted of the ECFS participants by the group’s leaders shows that group members are strongly
motivated in their work by the prospect of fusion energy, and they have expressed enthusiasm for a
strategic plan that would unite the community around a roadmap to achieve fusion-based electricity
within their lifetimes.

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In summary, meaningful coordination and alignment should occur regularly through suchactivities as FESAC charges to solicit a long-range plan on program/facility priorities and future
workshops with significantly broadened participation to include all fields contributing to fusion
technology. These activities, coupled with the creation of a new division, are recommended to bring
together the creative talent and the management needed for a unified national effort. Together, theyshould represent the community and enable a prioritization of resources in the most equitable way
possible to ensure a vibrant national program.
FURTHER STRENGTHENING OF UNITED STATES FUSION RESEARCH
In addition to the primary management guidance above, the committee also comments on six
additional areas: (1) safety and licensing standards for fusion energy research facilities, (2) the health of
the U.S. fusion research program, (3) the importance of continued participation in the larger international
effort, (4) the need to encourage growth of private sector capabilities in fusion energy technology, (5) thevalue of cross-disciplinary partnerships in related science and technology efforts, and (6) the importanceof public outreach to better communicate the long-term potential for economical fusion energy and tobetter engage students and educational institutions in the integrated science, technology, engineering, andmathematics at the foundation of fusion energy science.
Setting Safety and Licensing Standards for Fusion Energy Research Facilities
The pathway toward a compact fusion pilot plant requires one or more research facilities that arecapable of safely handling tritium and fusion neutrons, as well as other recognized fusion hazards such as
neutron-activated materials, high magnetic fields and significant thermal, mechanical loads. Siting andlicensing strategies for such facilities should be developed well in advance so as not to delay the progress
toward the compact fusion pilot plant. It is reasonable to expect that these tritium-capable fusion nuclear
research facilities will be owned by the U.S. DOE and sited at one or more national laboratory. The
operation of these facilities under U.S. DOE auspices will be an opportunity to provide insight toward
future siting and licensing of a compact fusion pilot plant.
The U.S. DOE Fusion Safety Standards5,6,7 were developed in the 1990's during the ITER
Engineering Design Activity8 in preparation for a potential siting of ITER in the United States.
Development of such standards required a multi-year effort with tight collaboration between the mainstakeholders, including U.S. DOE, the U.S. Nuclear Regulatory Commission (NRC), national
laboratories, and industry. The U.S. DOE Fusion Safety Standards were developed with the intention thatthat they would provide an initial set of requirements and design guidance that could later be used by
NRC to develop a fusion regulatory framework for commercial fusion.
Health of the U.S. Fusion Program
As was stated in the 2004 NRC Burning Plasma Assessment report (p. 119),9
The well-trained fusion scientist or engineer of the coming decades will require knowledge ofconcepts and techniques that do not now exist. The hardware and techniques for engineering andscientific research can be expected to change in fundamental ways. Examples involve expectedadvances in computational techniques, laser and other radiation sources for probing plasmas,
sensors, measurement techniques, materials, manufacturing techniques, and so on. Furthermore,
many of the scientific concepts used to describe physical phenomena will be qualitatively moresophisticated a decade or two hence. Examples of areas currently undergoing dramatic changes
include the modeling of nonlinear processes ranging from plasma heating to magnetic
reconnection and models of plasma turbulence and turbulent transport. These and many other

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areas are likely to change dramatically in the decades of the burning plasma experiment. Thus, thebasic training of fusion scientists and engineers in broad areas of physical science and engineeringmust continue to be an integral part of the fusion program.

The committee has taken notice of the enthusiasm within the United States fusion science
research community as reflected in the strategic workshops that reported on outstanding recent scientificand engineering progress and an eagerness of early career fusion scientists and engineers to help realize
fusion as an energy source. Nevertheless, there is concern that the future health of the United States
fusion energy sciences program is uncertain. This concern stems from shutting down major experimental
facilities (e.g., Alcator C-Mod) and smaller university scale experiments without replacements. This
domestic program contraction may be contrasted with new medium and large-scale facilities in Europe
and Asia (W7-X, MAST-U, JT60-SA, KSTAR, EAST, WEST, HL-2M,). The many contributions from
United States researchers show a history of innovation. The quality of United States research has allowed
the nation to remain, until now, a respected peer in the international fusion community. In the future,
maintaining a leadership role will require new domestic research facilities that target key questions and ademographically balanced workforce. Furthermore, even though there is widespread community support
for ITER, the United States has yet to prove that it can be a reliable ITER partner, and further delays arelikely if the nation does not fulfill its commitments on schedule.
A 2017 white paper on the status of university-based fusion science research submitted by the
University Fusion Association (UFA)10 expressed concern that reductions in federal funding for magnetic
fusion research at universities, and specifically a contraction in the number of experiments, lead directly
to reductions in the training of graduate students. It is further argued that these cutbacks also accelerate
the loss of research infrastructure and lead to reticence for university departments to hire new faculty withexpertise in this area. Similar concerns were expressed in the 2004 report of the NAS Burning Plasma
Assessment Committee11 about the aging of the fusion and plasma science workforce at universities andlarge fusion facilities; this has been further exacerbated in the years since. The UFA survey results showthat the average age of university faculty in the field has increased from 52.7 to 56 in the past 12 years,
and up to 30% of current faculty anticipate retirement in the next five years.
The committee expects that the expansion of scope of OFES recommended in this report willenergize university fusion research in several ways. New research initiatives to establish the science basisof fusion energy technology will create opportunities for university innovation, for stable funding tosustain university programs and to inspire the next generation of talented students to become part of thenational team. Over the past decades, universities within the United States have, alongside federally
funded laboratories, made innovations that advanced magnetic fusion energy plasma science andtechnology, leading to international recognition of U.S. leadership in the field. In the previous research
era when magnetic confinement concepts were evaluated, many universities were able to contribute withmoderately sized experimental facilities on site. The practicalities of burning plasma research introduce
new constraints on university participation. Future construction of domestic fusion nuclear facilities
involving burning plasmas and the safe handling of tritium will be sited at federally funded labs due totheir larger scale and required specialized safety infrastructure. A unified research effort will require anorganizational structure that enables involvement of both lab and university personnel in the use andoperations of major national facilities. Planning of operations for both national U.S. research facilities andthe large international facilities and ITER will require careful consideration to ensure representation andinclusion of contributing groups and broad participation of laboratory and university personnel based at
off-site institutions. One approach would be for U.S. DOE to provide travel and organizational support foreach facility to hold regularly scheduled “collaboration meetings” involving all participants for thispurpose. Large high energy physics experiments such as those at the LHC may serve as an example forinclusive science organizational practices. In addition, the committee notes the value of university scalemachines, both for their advantages in cost-effective investigation of focused research questions and fortheir hands-on educational value.

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International Partnerships
When construction is complete, ITER will be the world’s largest research facility and the mostsignificant near-term opportunity for the United States to advance burning plasma science. ITER
construction is now more than halfway completed, and the potential benefits to the U.S. of continued
funded participation as an ITER partner are evident. ITER addresses questions about burning plasma
science and reactor scale confinement that are essential to progressing toward the goal of fusion power.
International collaboration on ITER is a means for the U.S. to gain answers to these questions as anengaged partner while sharing costs with other participants. Moreover, the standing of the U.S. in the
global fusion community will hinge on fulfillment of its construction commitment as an ITER partner andalso the critical engagement of U.S. researchers in support of ITER experiments.12
National benefits as a reliable ITER partner include future opportunities for mutually beneficial
international collaborations to make advances in other aspects of the science and technology leading tofusion as an electricity source, including entertaining partnerships on future experiments sited in the
United States. As already mentioned, a decision by the United States to withdraw from the ITER
partnership would make international collaboration more difficult. Nevertheless, if the United States
withdraws from ITER, the U.S. would still need to pursue other avenues for collaboration andinternational cost-sharing.
Private Sector
As major new technologies develop and mature, the division of activities between universities,
government-funded labs and the private sector evolves. Considerable development often takes place inuniversities and national laboratories before commercial enterprise takes off. This is depicted in Figure
6.1 as developed by the 2017 Annual Report of the State of U.S. DOE National Laboratories.13 Magnetic
fusion energy research is currently in the second stage of technology maturation, called “development.”
During the “development” stage, a relatively small fraction of current activity is in the private sector. That
proportion will grow in the coming decades, presenting opportunities both to leverage commercial
ventures in technology development, and to begin preparation for a future fusion power industry.
Since the last burning plasma study in 2004, there has been a substantial increase in private
sector fusion energy funding and research. This increase has been of several sorts. First there are theindustrial contracts from the DOE issued to privately held corporations. This is not a new development.
The most significant activity is the General Atomics (GA) contract to manage the DIII-D facility. More
importantly perhaps, is that private industry is playing a major role in the construction of United States inkind contributions to ITER. For example, GA is assembling and testing the central solenoid
electromagnets. This industrial component of ongoing burning plasma science is significant and will
become increasingly important as the U.S. effort progresses toward the construction of a fusion pilot
plant. The expertise, developed for the ITER central solenoid in assembling large electromagnets will
expand to include producing very high magnetic fields using rare earth barium copper oxide, or REBCO,
superconducting cables

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FIGURE 6.1 The institutional balance of science and technology research evolves with maturity and technicalreadiness of the technology. While there are areas of overlap, universities emphasize early discovery and tend to
focus on research associated with individuals or small groups of faculty members. Companies respond to market
needs and typically focus their R&D on near-term solutions or the integration of multiple technologies. National
Laboratories have a particular capability to tackle multidisciplinary problems with long time horizons, often
coupling fundamental discovery research, technology development, and demonstration projects. From the 2017
Annual Report on the State of DOE National Laboratories.

Fusion science and technology research are also pursued in the private sector, both nationally andinternationally. The Fusion Industry Association14 is an international coalition of companies working todevelop fusion power technologies for the production of electricity. At the present time, the Fusion
Industry Association has sixteen members and five affiliate members. Similar to the professional societiesthat represent the fusion research community (e.g., the APS Division of Plasma Physics and the ANS
Fusion Energy Division), industry associations, like the Fusion Industry Association, can provide
important input to implementation of the national fusion research strategy.
One privately funded fusion energy ventures is TAE Technologies, with headquarters in Foothill
Range, CA. TAE Technologies was started nearly two decades ago by University of California-Irvine
physics professor Norman Rostoker. In contrast to mainstream fusion research, TAE concentrates on analternative magnetic confinement geometry, the field-reversed configuration (FRC). Though FRC
confinement performance has not achieved that of tokamaks, the configuration has many attractiveengineering features, including simplified divertor geometry and access for maintenance. A new mediumscale FRC experiment, dubbed “Norman” in Rostoker’s honor, was recently constructed and began

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operation in a single year. A predecessor device achieved confinement that is superior to previous FRC
experiments.15,16
The recently announced Commonwealth Fusion Systems,17 with headquarters in Cambridge, MA,
is another privately funded venture. Their goal is to combine proven tokamak physics developed in
decades of government-funded fusion research with high temperature superconducting (HTS) magnet
technology to accelerate the path to commercial fusion energy. MIT scientists and engineers are key
partners in the Commonwealth effort. Their first technical milestone is successful construction of an HTS
fusion magnet, with proposed construction of a compact fusion research device able to explore burning
plasma science should that technology development succeed.
All of these companies benefit enormously from the decades of U.S. Government sponsoredresearch that led to their emergence and now train their workforce, and the fundamental research activities
that remain critical before commercialization of fusion takes place. The next phase of commercializationin the United States might take a path similar to those in (1) the space industry with the emergence ofSpaceX, Blue-Horizon and Virgin Galactic, and (2) in the nuclear power industry with a substantial entryof smaller, modular advanced fission concepts. The development of fusion power will require increasing
participation by private industry, and, in select areas of technology, private industry is now ready to take alarger role.
Mutually beneficial partnerships can maximize information exchange between the public andprivate sectors by providing tools developed through U.S. DOE/FES funding to aid industry development
and design, integrating tools from both sectors to provide more complete physics/engineering
descriptions, and setting up the framework for each sector to propose and carry out experiments on theother sector’s devices to optimize progress toward development goals. Examples might include






Parallel private and government supported R&D on REBCO magnets, with companies andresearch labs contributing complementary strengths
U.S. DOE could provide access for future private sector development experiments at facilities
with safety measures and licensing for tritium and neutrons. Similar
cooperative developments are now in place at Idaho National Labs, Oak Ridge and SavannahRiver.
U.S. DOE/FES could provide access and support for the use of simulation and design codes,
developed with Federal R&D support, to be used by the private sector within the UnitedStates to make most effective these important private sector ventures.
There may be opportunities for U.S. DOE supported efforts to operate and exploit the science(diagnostics) on future private venture burning plasma machines.
Relationship Between Private Sector and National Goals

The U.S. fusion community, through a series of workshops and white papers, has concluded thatafter over a half-century of plasma physics research, sufficient progress has been made that it is now timeto increase attention to engineering and technology-based development. The NAS Panel supports thisconclusion. Increased industrial involvement in fusion development underscores this transition as well,and this welcome step offers the opportunity for the U.S. DOE fusion program to contribute in the formof partnerships and collaborations with industrial projects wherever appropriate. Specific contributions
can be made in the form of access to high quality simulation tools as well as to special purpose
experimental facilities. Intellectual property issues, while important but cumbersome, need to be resolved
by mutual negotiations.
The overall conclusion is that increased industrial interest in fusion is a good sign, indicating thereadiness to transition to more of a fusion energy focus and to take advantage of new opportunities forcollaboration.

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Linkages to Other Science and Technology Disciplines
Fusion energy science research is interdisciplinary and has resulted in technological and scientificachievements that touch many aspects of everyday life and lead to new insights in related fields such as
optics, fluid mechanics, and astrophysics. Fusion research has a long history of “spin-offs” contributing to
an impressive assortment of science and technology fields.18 Strong linkages between fusion energy
science and related research areas is anticipated in the burning plasma era. Several examples arehighlighted below.

Exascale Computing
For several decades, fusion research has been an important driver for using high-performancecomputing to describe complex physical systems. Already in 1974, it was realized that simulating the
behavior of a fusion plasma required a computer center dedicated to this purpose. This led to the foundingof the Controlled Thermonuclear Research Computer Center as the first unclassified supercomputer
center in the U.S. Its name was later changed to the National Energy Research Supercomputer Center(NERSC), and its mission was expanded to provide computing services to all of the programs funded by
the DOE Office of Energy Research (now the Office of Science). Now, fusion simulation codes are being
prepared for use on future exascale supercomputers (expected to become available within the next few
years), capable of at least a billion billion calculations per second. In the context of the DOE ExascaleComputing Project, efforts are underway to create a high-fidelity whole-device model of a magneticallyconfined fusion plasma. The long-term goal is to reproduce essential aspects of fusion experiments on asupercomputer, guiding the interpretation of existing experiments and helping to optimize the design offuture devices, including, in particular, a pilot plant. To this end, many physical processes, involving awide range of space and time scales, would need to be described in a way that accounts for their mutualinteractions. Fusion research shares this challenge with many other scientific domains, from materials
research to weather prediction, and contributes significantly to the development of a predictive
computational science, with broad applicability.
Magnets
The prospect of high magnetic field strengths of 20 Tesla and above drive the development,
including private sector ventures, of magnet coils manufactured from high-temperature superconductors(HTS). The technological leap to large HTS electromagnets now appears within reach, and their higher
magnetic fields will enable more compact fusion machines than what is possible even when current
niobium-titanium (NbTi) and niobium-tin (Nb3Sn) technologies have reached their practical performance
limits. While plasma confinement in MFE systems is currently a major driver for HTS magnet
development, high field electromagnets would be transformative in other fields as well, including particle
accelerators for high energy physics, MRI for medical imaging and NMR (spectroscopic method used, forexample, to determine the structure of organic compounds), all of which rely on high magnetic fieldstrengths.
Materials
One technological area which will significantly influence the design of the pilot plant is advanced
materials. Both fusion and fission applications require materials to sustain high heat and neutron flux. The
ability to design and tailor material and component properties is now possible with material synthesis andcharacterization techniques. For instance, precision control of processes enables the creation of new
alloys or nanostructured material to achieve desirable properties, such as high thermal conductivity or
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tritium retention. One example is the research and development on silicon carbide composites, which has
produced an engineered material composed of silicon carbide fibers embedded in a silicon carbide matrix
to form a strong fracture resistant material that is able to withstand high displacements per atom. Theseadvanced materials will be critical to realizing efficient fusion and fission devices.
Low Temperature Plasma Science
For the most part, laboratory plasmas for a wide variety of practical applications operate in a
vastly different regime from those approaching the burning plasma state. Some naturally occurring
plasmas can, along with technological plasmas, also be described as “low-temperature” plasmas, tocontrast them with their much hotter magnetically confined cousins in fusion experiments. There is,however, an intersection between the two subdisciplines in the exhaust region of tokamaks and othermagnetic confinement devices, known as the divertor. The divertor region of a fusion system is rich in
low temperature plasma physics, with a high temperature plasma and a solid surface in close proximity.
Understanding and manipulating the interactions between the low temperature plasma, neutral gas andradiation in the divertor as a means of protecting reactor surfaces from the huge exhaust heat flux
produced by burning plasmas will certainly lead to synergies with studies of low-temperature andtechnological plasmas. Neutral beam systems developed for heating of tokamak plasma, including ITER,
are another area of overlap between the MFE and low-temperature plasma communities.
Robotics and Automation
A fusion reactor is perhaps the ultimate challenging environment for essential operation andmaintenance, with the surrounding components characterized by high temperature, near 500 °K, vacuum,
liquid metals, confined spaces and kGy/hour neutron radiation. Remote maintenance (RM) will be afusion power plant “device defining driver” whether the reactor is a large conventional aspect ratio design
like the EU DEMO or a high-performance design like the compact pilot plant. Remote maintenanceconcepts should be integral to the design, construction, inspection, maintenance, operation anddecommissioning of the power plant and included in assessing the costs of material and waste flow
through the plant. The robotics solutions developed for fusion will have wide applicability in many othersectors, essentially anywhere that robotics solutions are required because person-entry is either impossibleor highly undesirable. This includes the space sector, the petrochemical industry where there is high riskof explosion, and broader nuclear applications, especially in decommissioning fission reactors. Beyond
the direct application of robots developed for fusion, there is also considerable synergy between thesensors and control systems of robotics developed for fusion and other sectors. As an example of this, thesensors and control systems developed for autonomous vehicles have been applied on the remote
maintenance system in JET in the EU.
Plasma Astrophysics
Burning plasma and natural plasma research are mutually beneficial. As fusion plasmas becomehotter, they more closely approach the very low levels of collisionality characteristic of many
astrophysical plasmas. The process of magnetic reconnection, where rearrangement of the magnetic field
impulsively releases a burst of energy, occurs in both settings. Instabilities driven by relativistic electronsand super-thermal ions have similar underlying physics. Models that describe particle and energy
transport by fluctuating electric and magnetic fields are applicable in both settings. Through systematic
variations of parameters that cannot be controlled in natural settings, laboratory experiments advanceunderstanding in both disciplines. An example of this synergy is the Max Planck/Princeton Center on
Plasma Physics, which is a collaborative study on processes in astrophysical and fusion plasmas.

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Public outreach
Public awareness is a critical element in maintaining support for the fusion effort and associatedexpenditures, and for inspiring young students to consider pursuing careers in fusion energy. A systematiccommunication and education campaign to engage the public should be maintained and expanded, withleadership by the U.S. DOE in collaboration with the National Academies as well as professionalsocieties such as APS, ANS, and IEEE. A solid basis for such an effort is already in place: for example,
the U.S. DOE Office of Science maintains a website with tutorial materials and frequent press releases
describing recent advances. The national labs have also been successful in promoting fusion energy
research at their respective institutions.
Future outreach initiatives should emphasize that realizing fusion as an energy source is a unitedeffort with contributions from many sectors across the country and through international collaborations,and from many disciplines, including supporting technologies, as well as contributions to other scienceand technology advances made possible by fusion research. Consideration should also be given tosystematic inclusion of fusion in energy-related instructional materials used in schools across the nation.
SUMMARY
This chapter describes an expanded organizational structure for the U.S. DOE Office of Fusion
Energy Sciences (OFES) that implements a research program evolving toward a long-term plan for fusionenergy and strengthens community participation in the burning plasma science, materials science, fusion
nuclear science and technology, and the engineering sciences needed to realize an economical pathway tofusion electricity for the nation. The committee arrived at several conclusions:Finding: The program management strategy for the coming decades would benefit from
exploiting the benefits of U.S. ITER participation as a full partner, while advancing a coordinateddomestic research program directed at elements of a fusion power system not addressed by ITER.
Finding: The recommended expansion in scope and interconnected programs within OFES will
necessitate reconsideration of management and planning to ensure coordination between
programs and efficient progress.
Finding: Success in fusion energy and global leadership will require opportunities for the U.S. tomaintain and expand its institutional knowledge in the design, construction and successful
operation of experimental facilities on a gradation of scales.
Finding: Community input in setting technical priorities (including initiation of new projects andfacilities and sunsetting those no longer needed) is essential for a healthy fusion energy program
because of the interrelated nature of fusion energy technologies. Ongoing community engagement
will further serve to promote community unity and foster morale and retention of a creative andproductive workforce.
Finding: Opportunities exist to encourage and support private investment in fusion energy
development and the focused, goal-oriented approach from U.S. industry, which is beneficial tofusion energy development.
Finding: Science and engineering resulting from U.S. investment in fusion energy research will
have synergies and benefits to other disciplines. Specific examples include: exascale computing,high field magnets employing high temperature superconductors (HTS), robotics, highperformance materials, low temperature plasmas and astrophysical plasmas.
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Based on these findings, the committee makes the following recommendations:
Recommendation: The committee recommends a new division within U.S. DOE/FES to
manage and organize research developing technologies needed to improve and fully enable
the fusion power system.
Recommendations: The U.S. DOE/FES should establish a formal strategic planning process
by which, at regular intervals, respected scientific and technical leaders review progress on
short- and long-term goals. This should include consideration of upgrades to and new U.S.based research facilities needed to advance science and technology in support of fusionenergy. Community input should be an essential element of this process.
Recommendation: The U.S. DOE/FES should establish formal structures for regularcommunication with and among leaders of the research communities across the OFES
program.
Based on the committee’s observations of other programmatic ways to strengthen fusion research,
the committee makes these additional recommendations:
Recommendation: It is recommended that the DOE Fusion Safety Standards be reviewed
for consistency with current regulations, and updated to incorporate the community's
increased knowledge of the performance of fusion systems and current fusion program
needs. In parallel with the fusion pilot plant design effort, a licensing strategy should be
developed that includes transition from DOE to NRC regulatory authority to ultimately
allow for commercialization of fusion power.
Recommendation: In addition to continued participation in ITER, the U.S. government
should explore partnerships with other existing and future facilities in Europe, Asia and the
U.S. as a means of pooling expertise and resources in advancing specific aspects of fusion
science and technology, including aspects of the tritium fuel cycle and the accompanying
areas of fusion nuclear materials, plasma facing materials, fusion nuclear science andenabling technologies.
Recommendation: The U.S. DOE OFES should define mechanisms to manage assignment ofintellectual property as a means to encourage both private and publicly funded researchers
to establish mutually beneficial partnerships.
Recommendation: The U.S. DOE OFES should conduct outreach initiatives that engage thefusion research community and inform the nation of the realization of fusion an energy
source is a united effort involving many disciplines, including advanced technologies andcontributes broadly to national science and technology goals. Public awareness is a criticalelement in maintaining support for the fusion effort and associated expenditures, and for
inspiring young students to consider pursuing careers in fusion energy, the fusion researchcommunity.

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NOTES
1. FESAC subcommittee on transformative enabling capabilities toward fusion energy, FESAC
Report: Transformative Enabling Capabilities for Efficient Advance Toward Fusion Energy, Departmentof Energy Office of Fusion Energy Sciences, February 2018.
2. From p. 126 of National Research Council. 2004. Burning Plasma: Bringing a Star to Earth.
Washington, DC: The National Academies Press. https://doi.org/10.17226/10816.
3. See https://sites.google.com/site/usmfrstrategicdirections/home
4. Bader et al. , “Perspective on Magnetic Fusion Energy Directions from Early Career Fusion
Scientists,” White paper submitted to Committee on a Strategic Plan for U.S. Burning Plasma Research(2018)
5. Safety of Magnetic Fusion Facilities: Requirements, DOE-STD-6002 (1996)
6. Safety of Magnetic Fusion Facilities: Guidance, DOE-STD-6003 (1996)
7. Supplementary Guidance and Design Experience for this Fusion Safety Standards DOE-STD6002-96 and DOE-STD-6003-96, DOE-STD-6004 (1999)
8. Final Report of the ITER Engineering Design Activities (EDA) (2001)
9. Burning Plasma Assessment Committee, “Burning Plasma: Bringing a Star to Earth,” National
Academies Press (Washington D.C., 2004).
10. “Status of University-based magnetic confinement research”, White Paper submitted to NAS(2017)
11. Burning Plasma Assessment Committee, “Burning Plasma: Bringing a Star to Earth,” National
Academies Press (2004).
12. Greenwald et al., “Recommendations for ITER Experimental Operation, U.S. Team Formation
and Participation,” Burning Plasma Organization, 2015.
13. Fig. 2-2 from the “Annual Report on the State of DOE National Laboratories, DOE Report,
January 2017.
14. Information about the Fusion Industry Association is available online
https://www.fusionindustryassociation.org.
15. Binderbauer, M., et al., Phys. Rev. Lett. 105 045003 (2010)
16. Tuszewski, M., et al., Phys. Rev. Lett. 108 255008 (2012)17. See https://www.cfs.energy
18. Wendt et al., “Applications of Fusion Energy Sciences Research,” Fusion Energy Sciences
Advisory Committee, U.S. DoE Office of Science (2015).

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Appendixes

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Statement of Task
A committee of the National Academies of Sciences, Engineering, and Medicine will be formed to study
the state and potential of magnetic confinement-based fusion research in the United States and provide guidance on
a long-term strategy for the field. The study will focus on research that supports understanding the magneticallyconfined burning plasma state but will take a broad view beyond plasma confinement science, and as such consider
capabilities such as simulation and materials. Specifically, the committee will prepare an interim report that will:
1.
2.

Describe and assess the current status of U.S. research that supports burning plasma science, including
current and planned participation in international activities, and describe international research
activities broadly.
Assess the importance of U.S. burning plasma research to the development of fusion energy as well as
to plasma science and other science and engineering disciplines.

The committee will also prepare a final report, building on the interim report, which will:
1.
2.

Consider the scientific and engineering challenges and opportunities associated with advancing
magnetic confinement fusion as an energy source, including the scientific and technical developments
since the 2004 NAS1 study on burning plasma research.
In two separate scenarios in which, after 2018, (1) the United States is a partner in ITER, and (2) the
United States is not a partner in ITER: provide guidance on a long-term strategic plan (covering thenext several decades) for a national program of burning plasma science and technology research which
includes supporting capabilities and which may include participation in international activities, given
the U.S. strategic interest in realizing economical fusion energy in the long term.

In doing the above, the committee will consider the priorities for the next ten years developed by thecommunity and FES that were recently reported to Congress. The committee will also consider the current level ofparticipation by U.S. scientists in international activities as well as what role international collaboration should playover the next 20 years. The committee will also consider the health of the domestic fusion research sectors(universities, national laboratories, and industry). Elements of any strategic plan for U.S. burning plasma researchshould ensure that the United States maintains a leadership role in this field. The committee may assume that
economical fusion energy within the next several decades is a U.S. strategic interest. The committee may take into
account how unanticipated events or innovations may necessitate mid-course re-directions. The committee will use
the prior work of the Academies as well as that of FESAC and the domestic and foreign communities in its
deliberations. The committee is not to compare fusion as an energy source against other current or potential energy
sources. The committee will consider the budget implications of its guidance but will not make recommendations
about the budget for burning plasma research itself. The committee will only consider magnetically confinedburning plasma research as within its purview. The committee may make recommendations or offer comments onorganizational structure and program balance, with accompanying supporting discussion of the evidentiary bases, as
appropriate.

1

Effective July 1, 2015, the institution is called the National Academies of Sciences, Engineering, andMedicine. References in this report to the National Research Council (NRC) are used in a historical context to referto activities before July 1.

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B
Agendas from Committee Meetings and Site Visits
Meeting #1
June 5-6, 2017
Keck Center of the National Academies
500 5th Street NW
Washington, D.C
June 5, 2017
CLOSED SESSION
8:00 A.M.
Breakfast
9:00 A.M.
Discussion
12:00 P.M.
Lunch
1:00 P.M.
Discussion
OPEN SESSION
1:45 P.M.
Reconvene
2:00 P.M.
Perspective from DOE Fusion Energy Sciences, Ed Synakowski, DOE FES
3:00 P.M.
Break
3:15 P.M.
Perspectives from Capitol Hill, Adam Rosenberg and Emily Domenech, House Science,
Space, and Technology
4:00 P.M.
Perspectives from the U.S. Burning Plasma Organization, Chuck Greenfield, General
Atomics, and Amanda Hubbard, MIT
5:00 P.M.
Open public comments
5:30 P.M.
Break
CLOSED SESSION
6:30 P.M.
Committee dinner
8:30 P.M.
Adjourn for the day
June 6, 2017
CLOSED SESSION
This day is held entirely in closed session.
Meeting #2
August 29-31, 2017
Beckman Center of the National Academies
Irvine, California

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August 29, 2017
CLOSED SESSION
8:00 A.M.
Breakfast
9:00 A.M.
Committee discussion
OPEN SESSION
9:30 A.M.
Perspectives from the U.S. ITER Project, Ned Sauthoff, Oak Ridge National Lab
Perspectives from the ITER Organization, Bernard Bigot, Director General
10:30 A.M.
Break
11:00 A.M.
Perspective on Fusion Energy Strategy, Stewart Prager, Princeton University
12:00 P.M.
Lunch
1:00 P.M.
Perspective on Fusion Energy Strategy, Tony Taylor, General Atomics
2:00 P.M.
Perspectives from University Fusion Associates, David Maurer, Auburn University
3:00 P.M.
Break
3:30 P.M.
Perspectives from the Virtual Laboratory for Technology, Phil Ferguson, Oak Ridge
National Lab
4:30 P.M.
Public comments
CLOSED SESSION
5:00 P.M.
Discussion
OPEN SESSION
6:30 P.M.
Dinner
8:30 P.M.
Adjourn for the day
August 30, 2017
CLOSED SESSION
8:30 A.M.
Committee discussion
6:00 P.M.
Adjourn for the day
August 31, 2017
CLOSED SESSION
8:30 A.M.
Committee discussion
2:00 P.M.
Adjourn

Meeting #3
December 15-16, 2017
Omni Austin Downtown
Austin, TX
December 15, 2017
OPEN SESSION – Capital Ballroom
8:00 A.M.
US Magnetic Fusion Research Strategic Directions Workshop
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10:30 A.M.

Break
12:30 P.M.

Workshop Concludes

December 16, 2017
CLOSED SESSION – Austin Conference Room
8:00 A.M.
Committee Discussion
12:30 P.M.
Working Lunch
OPEN SESSION
1:30 P.M.
Reception of the interim report, Jim Van Dam, DOE-Fusion Energy Sciences
2:15 P.M.
Path forward for fusion Dennis Whyte, MIT’s Plasma Science and Fusion Center
3:00 P.M.
Princeton lab update, Richard Hawryluk, Princeton Plasma Physics Laboratory
3:45 P.M.
Public Discussion
4:30 P.M.
Break
CLOSED SESSION
5:00 P.M.
Discussion
OPEN SESSION - Perry’s Steakhouse
7:00 P.M.
Dinner
9:00 P.M.
Adjourn for the day
Meeting #4
February 1-2, 2018
ITER
St. Paul Lez Durance France
February 1, 2018
OPEN SESSION – ITER Council Room
9:00 A.M.
Welcome from ITER Organization, Bernard Bigot, Director-General
9:15 A.M.
Opening Remarks, Introductions, and Discussion of Agenda,
Michael Mauel and Melvyn Shochet, Study Committee Co-Chairs
9:30 A.M.
Foundation of the EUROfusion Consortium, Sibylle Guenter, Max Planck Institut für
Plasmaphysik
10:30 A.M.
Break
11:00 A.M.
Strategic Plan of the European Fusion Consortium, Tony Donné, EUROfusion
12:00 A.M.
Lunch and General Discussion
1:30 P.M.
European DEMO design activities, Gianfranco Federici, EUROfusion
2:30 P.M.
Break
3:00 P.M.
Overview of ITER Project and International Organization,
Bernard Bigot, Director-General, ITER
4:00 P.M.
The Science of ITER, Tim Luce, Head of Science and Operations, ITER
5:00 P.M.
General Discussion
6:00 P.M
Break and Depart for Dinner
7:00 P.M.
Committee Dinner - Le Jardin Mazarin
9:00 P.M.
Adjourn for the day
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February 2, 2018
OPEN SESSION – ITER Council Room
9:00 A.M.
Tour of ITER Worksite Bernard Bigot, Director-General, ITER
10:30 A.M.
Break
10:45 A.M.
ITER Engineering Science and Breakthroughs
Gyung-Su Lee, Deputy Director-General, ITER
11:45 A.M.
Lunch
1:15 P.M.
Project Management, Hans-Henrich Altfeld, Head of Project Control Office, ITER
2:15 P.M.
Summary and Conclusion, Bernard Bigot, Director-General, ITER
2:30 P.M.
Break
CLOSED SESSION – ITER Council Room
3:00 P.M.
Committee discussion
4:00 P.M.
Adjourn and depart for hotel/airport;
Meeting #5
February 26-28, 2018
General Atomics (GA)San Diego, CA
February 26, 2018
OPEN SESSION – GA Conference Room
8:00 A.M.
Breakfast
9:00 A.M.
Welcome from General Atomics and Discussion of Agenda
9:15 A.M.
Research Plans of the DIII-D National Team, Richard Buttery, GA
10:15 A.M.
Vision for Fusion Research at General Atomics, Dave Hill, GA
11:15 A.M.
Break
11:30 A.M.
Strategic elements/Approaches of the U.S. Fusion Program, Mickey Wade, GA
12:15 P.M.
Lunch and General Discussion
1:30 P.M.
Japanese Fusion Energy Strategy, Yuichi Ogawa, Univ. Tokyo
2:30 P.M.
Republic of Korea Fusion Energy Strategy, Yong-Seok Hwang, Seoul National
University.
3:30 P.M.
Break
4:00 P.M.
Break and depart for tour of DIII-D facility
6:30 P.M.
Working dinner - Eddie V’s Prime Seafood
8:00 P.M.
Adjourn for the day
February 27, 2018
CLOSED SESSION– GA Conference Room
8:30 A.M.
Committee discussion
10:00 A.M.
Break
10:15 P.M.
Committee discussion
12:00 PMLunch

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February 28, 2018
CLOSED SESSION– GA Conference Room
8:00 A.M.
Committee discussion
OPEN SESSION
9:00 A.M.
Tour of Magnet Technology Center
CLOSED SESSION– GA Conference Room
11:00 A.M.
Committee Discussion
12:00 P.M.
Working Committee Lunch
1:00 P.M.
Committee Discussion
3:00 P.M.
Adjourn
Meeting #6
April 11-13, 2018
Princeton Plasma Physics Laboratory
Princeton, NJ
April 11, 2018
OPEN SESSION – Lyman Spitzer Building, Conference Room B318
9:00 A.M.
Welcome from PPPL and Discussion of Agenda
9:15 A.M.
Overview Vision of PPPL in Long-Term Fusion Strategy, Mike Zarnstorff, PPPL
9:45 A.M.
Options and Strategies towards Fusion Net-Electricity , Jon Menard, PPPL
10:30 A.M.
NSTX-U Research and Operation Plan, Stefan Gerhardt, PPPL
11:15 A.M.
Break
11:30 A.M.
Advanced Scientific Computing Strategy for Fusion, Amitava Bhattacharjee, PPPL
12:15 P.M.
Lunch
12:15 P.M.
Trying for Upside Potential in Controlling Fusion, Nat Fisch, PPPL
CLOSED SESSION
1:30 P.M.
Committee Discussion Committee and Staff
OPEN SESSION - Witherspoon Grill
6:30P.M.
Committee working dinner
8:00 P.M.
Adjourn for the day
August 12, 2018
CLOSED SESSION
8:30 A.M.
Committee discussion
OPEN SESSION
1:00 P.M.
High-Field Development Strategy for Fusion, Martin Greenwald, MIT
1:45 P.M.
Investor-MIT Partnership for Fusion Development, Bob Mumgaard, CFS
2:15 P.M.
Strategic Prospects for HTS Magnets for Fusion, Soren Prestemon, LBNL
3:00 P.M.
Break
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3:15 P.M.
4:00 P.M.
4:45 P.M.

Plasma-Materials and Divertor Options for Fusion, Juergen Rapp ORNL
Liquid Metal Technology Strategy for Fusion, Mike Jaworski, PPPL
Public comment

CLOSED SESSION
5:00 P.M.
Committee Discussion Committee and Staff
OPEN SESSION
6:00
Tour of NSTX-U and PPPL Laboratory
7:30
Adjourn for the day

Meeting #7
June 12-14, 2018
Keck Center of the National Academies
Washington D.C
June 12, 2018
CLOSED SESSION – Keck 201
9:00 A.M.
Welcome and Discussion of Agenda, Co-chairs, Mike Mauel and Mel Shocket
9:15 A.M.
Current summary of findings and recommendations
10:15 A.M.
Break
10:30 A.M.
High-level discussion: Does the draft reflect our findings and recommendations?
12:00 P.M.
Lunch
1:00 P.M.
Review of Chapter 2
2:30 P.M.
Break
2:45 P.M.
Review of Chapter 3
4:15 P.M.
Review of Chapter 4
5:45 P.M.
Break for dinner
6:30 P.M.
Committee working dinner - Ruth’s Chris Steak House
8:00 P.M.
Adjourn for the day
June 13, 2018
CLOSED SESSION – Keck Room 201
8:30 A.M.
Review of Chapter 6
10:15 A.M.
Break
10:30 A.M.
Review of Summary
12:00 P.M.
Lunch
1:00 P.M.
2nd Review of findings and recommendations
2:30 P.M.
Break
2:45 P.M.
2nd Discussion: Does the draft reflect our findings and recommendations?
4:15 P.M.
Further Discussion: what needs to be drafted?
5:45 P.M.
Adjourn for the day

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June 14, 2018
CLOSED SESSION – Keck Room 101
8:00 A.M.
Breakfast available in meeting room
9:00 A.M.
High-level discussion: summary and thoughts
10:30 A.M.
Break
11:00 A.M.
Discussion: further assignments and schedule
12:00 P.M.
Lunch
1:00 P.M.
Wrap up/continued discussion of next steps
2:00 P.M.
Adjourn

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C
Strategic Planning for U.S. Burning Plasma Research from 2000 to 2018
This appendix provides background to various strategic planning activities for the U.S. burning
plasma research effort beginning with the 2001 FESAC Report on Burning Plasma Physics1 to the 2015
strategic planning perspective provided to Congress by the U.S. DOE Office of Science in response to theConsolidated Appropriations Act, 2014.2 Background to U.S. fusion strategic planning is also available inAppendix D: “Fusion Community Recommendations” of the 2004 NAS Report of the Burning Plasma
Assessment Committee3 and in Chapter 1 of the committee’s Interim Report.
The following background to U.S. strategic planning activities is organized into three parts: (i)Achievement of Government Consensus to Join ITER, (ii) U.S. Planning during the ITER Design Review
and Start of Construction, and (iii) Management Reforms and the Updated ITER Cost and Schedule.
Achievement of Government Consensus to Join ITER
In October 2000, Mildred Dresselhaus, Director of the Office of Science requested FESAC
address the scientific issues of burning plasma physics. In her letter, Dresselhaus noted the U.S. magnetic
fusion community has recognized burning plasma physics as the next frontier of fusion research andquoted the recommendation of the 1990 Fusion Policy Advisory Committee for “construction as soon as
possible of the U.S. Burning Plasma Facility.” In addition to reporting the scientific issues to be addressedby a burning plasma physics experiment, FESAC was charged to address how the U.S. program should be
used to assist the community in preparations for an assessment in 2004, as recommended in the 1999
FESAC Subcommittee on Priorities and Balance.4
The main conclusion of the 2001 FESAC Report on Burning Plasma Physics (p. 7) was:The U.S. fusion program, and indeed the world fusion program, is technically andscientifically ready to proceed NOW with a burning plasma experiment. This is the logicalnext step on the path to fusion energy. The key physics and engineering questions have been
known since the mid 1980’s. They have been investigated theoretically during the interim
period. They have been investigated on existing experiments, although often one at a time or in
reduced performance regimes because of experimental limitations. Further progress requires anew, large scale burning plasma experiment. Thus, the key question is not “Are we ready?” butinstead “How should we proceed?”

The 2001 FESAC Burning Plasma Physics Report further said (i) a workshop should be held forthe scientific and technological examination of proposed burning plasma experimental designs and toprovide community input and endorsement to FESAC planning activities, and (ii) that the DOE initiate a1

Report of FESAC Subcommittee, Review of the Burning Plasma Physics, DOE/SC-0041. Washington, D.C.:
U.S. Department of Energy, 2001; available online athttps://inis.iaea.org/collection/NCLCollectionStore/_Public/46/134/46134990.pdf
2
U.S. DOE Report to Congress, The Office of Science's Fusion Energy Sciences Program: A Ten-Year
Perspective, (December 2015); available online at https://fire.pppl.gov/FES_10Year_Perspective_2015.pdf
3National Research Council. 2004. Burning Plasma: Bringing a Star to Earth. Washington, DC: The National
Academies Press. https://doi.org/10.17226/10816.
4
Report of the FESAC Panel on Priorities and Balance, (1999); available as Baker, C., Davidson, R., Dean, S.
et al. Journal of Fusion Energy (1999) 18: 65. https://doi.org/10.1023/A:1018831113757

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review by a National Research Council committee with the goal of determining the desirability as well as
the scientific and technological credibility of the burning plasma experiment design. The 2001 FESAC
Report was highly influential, and the U.S. DOE adopted both follow-on planning activities.
In 2002, the U.S. fusion community organized a fusion summer study, co-sponsored by the APS
Division of Plasma Physics, the ANS Fusion Energy Division, and the U.S. DOE/FES. At the same time,
DOE Office of Science’s Acting Director, James Decker, charged FESAC to establish a high-level panel
to recommend a strategy for burning plasma experiments. The FESAC Panel on a Burning Plasma
Program Strategy to Advance Fusion Energy5 considered three options for a burning plasma experimentat different sizes and levels of readiness and concluded (p. 3), “Since ITER is at an advanced stage, has
the most comprehensive science and technology program, and is supported internationally, we should
now seek to join the ITER negotiations with the aim of becoming a partner in the undertaking, withtechnical, programmatic and timing considerations” that included U.S. participation in the full range ofactivities, proposing and implementing science experiments, reviewing the overall cost of the ITER
project, and concluding that ITER is highly likely to proceed to construction.
On September 2002 and upon release of the FESAC Report on a Burning Plasma Program
Strategy to Advance Fusion Energy, Raymond Orbach, Director of the Office of Science, tasked acommittee of National Academies to “carry out an assessment of a program of burning plasma
experiments and its role in magnetic fusion research.” The NAS Burning Plasma Assessment Committee
was instructed to complete an Interim Report (see Appendix E of Ref. 3) containing “advice to the
Department of Energy regarding reentering negotiations to be a participant in the multinational burning
plasma experiment (ITER).” The NAS Burning Plasma Assessment Committee was asked to “makerecommendations on the program strategy aimed at maximizing the yield of scientific and technicalunderstanding as the foundation for the future development of fusion as an energy source.” But the NAS
committee was not asked to evaluate fusion as an energy option. This task was given to a FESAC
subcommittee, also in September 2002, resulting in the 2003 Report of the FESAC Subcommittee for aPlan for the Development of Fusion Energy.6 While the NAS Burning Plasma Assessment Committee
was asked to consider the importance and readiness to undertake a burning plasma experimental program,
the FESAC subcommittee was asked “to comment, from our present state of understanding of fusion, on
the prospects and practicality of electricity into the U.S. grid from fusion in 35 years.”
The Interim Report of the NAS Burning Plasma Assessment Committee was released on
December 20, 2002 and recommended “the United States enter into ITER negotiations while the strategy
for an expanded U.S. fusion program is further defined and evaluated.” This recommendation was subject
to three conditions: (i) “a strategically balanced program, including meaningful U.S. participation in ITER
and a strong domestic fusion science program, must be maintained, recognizing that this will eventuallyrequire a substantial augmentation in fusion program funding in addition to the direct financial
commitment to ITER construction”, (ii) “fusion program strategy should include cost estimates andscenarios for involvement in ITER, integration with the existing fusion science program, contingency
planning, and additional issues as raised in this letter”, and (iii) “the United States should pursue anappropriate level of involvement in ITER, which at a minimum would guarantee access to all data from
ITER, the right to propose and carry out experiments, and a role in producing the high-technology
components of the facility, consistent with the size of the U.S. contribution to the program.”

5
FESAC Panel Report on a Burning Plasma Program Strategy to Advance Fusion Energy (DOE/SC-0060,
September 2002); also available at Prager, S., Baker, C., Baldwin, D. et al., J Fusion Energy (2001) 20: 85.
https://doi.org/10.1023/A:1021398608479
6
Report of the FESAC Fusion Development Panel (March 2003), A Plan for the Development of Fusion
Energy, DOE/SC-0074; also available as Goldston, R., Abdou, M., Baker, C. et al. Journal of Fusion Energy (2002)
21: 61. https://doi.org/10.1023/A:1025038002187 .

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FIGURE C.1 The overlapping scientific and technological challenges needed in the fusion development
path described in the 2003 FESAC Report (p. 7 of Ref. 6). In order to demonstrate fusion electricity,materials testing research and fusion component testing should accompany burning plasma research.

The 2003 FESAC Report for A Plan for the Development of Fusion Energy presented acomprehensive fusion development strategy that included both inertial fusion energy (IFE) and magnetic
fusion energy (MFE). The key conclusion of the plan was (p. 6 of Ref. 6) was “to develop fusion energy
on this timescale [35 years], it is imperative to have a strong balanced program that develops fusion
science and technology in parallel”. The committee found a set of overlapping scientific andtechnological challenges that determined the development path for fusion energy. These challenges were
presented in Fig. A.1 and comprised research in configuration optimization, burning plasma science,materials testing, fusion component testing, demonstration of environmentally and economicallyattractive fusion energy, and the underlying science and technology programs in basic plasma science,
theory and simulation, materials science, and engineering science.
Six weeks after the release of the NAS Burning Plasma Interim Report, on January 30, 2003,
President George W. Bush announced “that the United States will join an ambitious international research
project to harness the promise of fusion energy, the same form of energy that powers the sun.” The
President's announcement described ITER as “the largest and most technologically sophisticated fusion
experiment in the world.” The President also acknowledged the National Academies recommendation for
U.S. participation in ITER and further explained, “This step is critical to the development of fusion as a
viable energy source. Recent scientific developments have advanced knowledge of this field to the pointthat scientists now believe ITER can demonstrate the feasibility of this technology as part of an ongoing
effort to develop a practical energy-generating device.”
Later that year, Raymond Orbach requested FESAC to assist in establishing priorities for thefusion program in light of the recommendation of the 2004 NAS Burning Plasma Committee for a neweffort to integrate ITER into the U.S. domestic program. The 2005 FESAC Report on Scientific

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Challenges, Opportunities and Priorities for the U.S. Fusion Energy Sciences Program7 describedoverarching themes, asked topical scientific questions, and defined six campaigns to plan, organize, andcoordinate research activities. The committee’s recommendations called for “a research program thatencompasses a broad range of key scientific questions,” identified high-priority activities for the domestic
research program that would be enhanced with additional funding, and stated “the need for additional
major domestic experimental facilities.”
Achievement of government consensus on rejoining ITER, along with broad support within the
U.S. scientific community, was a major accomplishment over the past decade. The committee’s key
recommendation was: “The United States should participate in the International Thermonuclear
Experimental Reactor (ITER) project. If an international agreement to build ITER is reached, fulfilling
the U.S. commitment should be the top priority in a balanced U.S. fusion science program.” Following
this recommendation, the U.S. Department of Energy Twenty-Year Outlook8 listed ITER as the highest
priority within the Office of Science in 2003 and, again, in 2007.9
The international agreement to build and operate a burning plasma experiment was finallyformalized in Paris with the signing of the Agreement on the Establishment of the ITER International
Fusion Energy Organization for the Joint Implementation of the ITER Project on November 2006.10 The
ITER International Fusion Energy Organization (IO) is a public international organization, with limited
privileges and legal immunities, involving the U.S. with China, the European Union, India, Japan, theRepublic of Korea and the Russian Federation. At the signing ceremony, DOE Undersecretary for Science
Raymond Orbach explained, “ITER is the first stand-alone, truly international, large-scale scientificresearch effort in the history of the world.”
U.S. Planning During the ITER Design Review and Start of Construction
As predicted by the 2004 NRC Burning Plasma Assessment Committee (p. 12 of Ref. 3), “oncethe [ITER] decision is made, fulfilling the international commitment to help construct the ITER facility
and participate in the ITER program will necessarily become the highest priority in the program.” This
new priority within the United States fusion energy sciences program following the ITER agreement
resulted in several planning activities, both (i) to guide U.S. participation in the ITER project and (ii) to
develop and define U.S. fusion research that would accompany ITER.
In response to the Energy Policy Act of 2005, DOE Undersecretary for Science Raymond Orbachtasked the National Academies to review the plan for U.S. Community Participation in the ITER
Program11 that was developed by the U.S. Burning Plasma Organization (USBPO). The NAS committee
made several recommendations (pp. 2-4) including that steps should be taken to “seek greater funding
stability for the international ITER project to ensure that the United States remains able to influence thedeveloping ITER research program, to capitalize on research at ITER to help achieve U.S. fusion energy
goals, to participate in obtaining important scientific results on burning plasmas from ITER, and to be aneffective participant in and beneficiary of future international scientific collaborations.” The committee
also noted important considerations not reflected in the DOE plan for U.S. participation in ITER should

7

FESAC (2005), Report on Scientific Challenges, Opportunities and Priorities for the U.S. Fusion Energy
Sciences Program; available as Baker, C., Prager, S., Abdou, M. et al. J Fusion Energ (2005) 24: 13.
https://doi.org/10.1007/s10894-005-6922-z
8
DOE, Facilities for the Future—A Twenty Year Outlook, Office of Science, Washington, D.C., November
2003.
9Facilities for the Future - A Twenty Year Outlook, U.S. DOE Office of Science (November, 2003).
10
https://www.iaea.org/sites/default/files/publications/documents/infcircs/2007/infcirc702.pdf
11
National Research Council. 2009. A Review of the DOE Plan for U.S. Fusion Community Participation in the
ITER Program. Washington, DC: The National Academies Press. https://doi.org/10.17226/12449.

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3
2
1

How Initiatives Could
Address Gaps

LegendMajor Contribution
Significant Contribution
Minor Contribution

No Important Contribution

I-1. Predictive plasma modeling and validation
initiativeI-2. ITER – AT extensions

I-3. Integrated advanced physics demonstration (DT)I-4. Integrated PWI/PFC experiment (DD)I-5. Disruption-free experiments

I-6. Engineering and materials science modeling andexperimental validation initiativeI-7. Materials qualification facility

I-8. Component development and testingI-9. Component qualification facility

3 2

2

2

2 2 1 12 1 3 3 1 1

1 1 1

1 1

1 1

3 2 1 3 3

2 2 3 11 2

3 3 3 3 3

2 1

2 1 3

1

3 3 3 2 2 2

1 3 1 3 2 3 3 2 1

2 1

3 2 2 3 3 3 3 3 3

3 3 3 3 3 1 3 2 3 3 1 1 1 1 1

2 1

1

1 1 2 1 2

G -1 P la s m a P re d ic tiv e c a p a b ility
Gd e - m2 oI nn ts et gr ar ta i toe nd p l a s m a
G -3 N u c le a r-c a p a b le D ia g n o s tic s
Gm -i 4n i Cm oa nl tpr oo lw ne er a r l i m i t s w i t h
Gn o- r5 m Aa vl oe iv de an nt cs ei no ft o kL aa mr g ae k- ss c a l e O f f Go f - 6o f Df - en vo er lmo pa lm p el na st sm f ao re vc oe nn tc s e p t s f r e e
Gs t r- u7 c Rt u e r ae cs t o r c a p a b l e R F l a u n c h i n g
G -8 H ig h -P e rf o rm a n c e M a g n e ts
G -9 P la s m a W a ll In te ra c tio n s
G -1 0 P la s m a F a c in g C o m p o n e n ts
G -1 1 F u e l c y c le
G -1 2 H e a t re m o v a l
G -1 3 L o w a c tiv a tio n m a te ria ls
G -1 4 S a fe ty
G -1 5 M a in ta in a b ility

FIGURE C.2 Figure 1 (p. 20) from the 2007 FESAC Report on Priorities, Gaps and Opportunities
Towards A Long-Range Strategic Plans for Magnetic Fusion Energy.12 The effectiveness of nine
potential initiatives to address all of the scientific and technical gaps to fusion energy development
illustrates that accompany research in addition to ITER is needed.

be addressed and include “existing gaps in planning for a Demonstration Power Plant, dissemination of
information on and the results of ITER research activities to the broader scientific community, andplanning for the recruitment and training of young scientists and engineers.”
Five subcommittees of FESAC provided important strategic guidance for the research needed toadvance fusion energy science alongside ITER. These six subcommittees completed their reports in thefive years following the signing of the ITER agreement:Report of the 2007 FESAC Subcommittee on Priorities, Gaps and Opportunities Towards A
Long-Range Strategic Plans for Magnetic Fusion Energy,12which submitted fourrecommendations (pp. 6-7): (i) “a long-term and detailed strategic plan should be developed andimplemented as soon as possible,” (ii) the “plan should recognize and address all scientificchallenges of fusion energy including fusion engineering, materials sciences and plasma physics,”(iii) the “plan should include bold steps and encourage adoption of major new initiatives orconstruction of new facilities in order to resolve scientific challenges,” and (iv) “nine potential
initiatives, ranging from key topics in fusion science and engineering to large, integrated plasma
experiments exploring aspects of the fusion reactor environment.”

12

Report of the 2007 FESAC Subcommittee on Priorities, Gaps and Opportunities Towards A Long-Range
Strategic Plans for Magnetic Fusion Energy; available online athttps://science.energy.gov/~/media/fes/fesac/pdf/2007/Fesac_planning_report.pdf

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








Report of the 2007 FESAC Subcommittee on Fusion Simulation Project (FSP),13 which
recommended joint U.S. DOE/FES-ASCR program activities (p. 1) “to develop advanced
software designed to use leadership class computers for carrying out multi-scale physics
simulations to provide information vital to delivering a realistic integrated fusion simulation
model with unprecedented physics fidelity.”
Report of the 2008 FESAC Toroidal Alternatives Panel,14 which made several general findings ofthe quality, benefit, and status of various configurations for magnetic confinement fusion.
DOE Office of Science, 2009 Report of the Research Needs Workshop for Magnetic Fusion
Energy (ReNeW),15 which involving some 200 scientists from universities, national laboratories
and private industry to develop a portfolio of research activities for U.S. research in magnetic
fusion for two decades. The report characterized three “ReNeW thrusts” (p. 9): (i) “advancementin fundamental science and technology”, (ii) “confrontation with critical fusion challenges”, and(iii) “the potential for major transformation of the program – such as altering the vision of afusion reactor, or shortening the time scale for fusion’s realization.”
Report of the 2012 FESAC subcommittee on Materials Science and Technology Research
Opportunities Now and in the ITER Era: A Focused Vision on Compelling Fusion Nuclear
Science Challenges,16 which made three overarching recommendations (pp. vi-vii): (i) as fusion
nuclear science matures from concept exploration studies to more complex proof of principle
studies, it is appropriate to focus R&D on front-runner concepts; (ii) numerous fusion nuclear
science feasibility issues can be effectively investigated during the next 5 to 10 years by efficientuse of medium-scale facilities; and (iii) the key mission of the next step U.S. device should be to
explore the integrated response of tritium fuel, materials and components in the extreme fusion
environment in order to provide the knowledge bases to contain, conquer, harness and sustain athermonuclear burning DT plasma at high temperatures.
Report of the 2012 FESAC subcommittee on Opportunities for and Modes of International
Collaboration in Fusion Energy Sciences Research during the ITER Era,17 which considered thequestion “what additional international collaborations should be pursued by a US FES programthat is already expecting to be dominated by the large international ITER collaboration?” andidentified three compelling opportunities for international collaboration (pp. 7-9): (i) extending
high performance regimes to long pulse, (ii) development and integration of plasma wall
solutions for fusion, and (iii) burning plasma research in advance of ITER.

The 2007 FESAC Report on Priorities, Gaps and Opportunities “found remarkable progress has
been made by the [fusion research] program but recognized that formidable challenges remain.” Thereport organized the key scientific and technical questions that need to be answered into three themes:
creating predictable high-performance steady-state plasmas, taming the plasma material interface, andharnessing fusion power. An important conclusion of the FESAC subcommittee was multiple initiatives
13

ESAC (2007) Report on Fusion Simulation Project (FSP);
https://science.energy.gov/~/media/fes/fesac/pdf/2007/Fesac_fsp_report.pdf.
14
FESAC Toroidal Alternatives Panel (2008);
https://science.energy.gov/~/media/fes/fesac/pdf/2008/Toroidal_alternates_panel_report.pdf
15
DOE Office of Science, Report of the Research Needs Workshop for Magnetic Fusion Energy (ReNeW),(Bethesda, Maryland – June 8-12, 2009); https://science.energy.gov/~/media/fes/pdf/workshopreports/Res_needs_mag_fusion_report_june_2009.pdf
16
FESAC Report (2012) on Materials Science and Technology Research Opportunities Now and in the ITER
Era: A Focused Vision on Compelling Fusion Nuclear Science Challenges;
https://science.energy.gov/~/media/fes/pdf/workshop-reports/20120309/FESAC-Materials-Science-final-report.pdf.
17
FESAC Report (2012) on Opportunities for and Modes of International Collaboration in Fusion Energy
Sciences Research during the ITER Era; https://science.energy.gov/~/media/fes/pdf/workshopreports/20120309/Intl_Collab_Final_SCSC-PRINT.pdf.

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were needed to fully address the scientific and technical gaps in fusion development. Fig. A.2 shows theeffectiveness of the nine potential initiatives in addressing the key scientific and technical questions.
While the ITER burning plasma research program addresses many questions, additional research should
accompany ITER to answer questions related to the plasma material interface and the technologies toharnessing fusion power.
Simultaneous with the above-mentioned U.S. research planning activities, the United States
contributed to the international review and update of the ITER physics basis and design. The initial ITER
physics basis was published as nine chapters of Nuclear Fusion in 199918 and represented the combined
expert knowledge of the international community for the ITER project. This physics basis was available
to the 2004 NAS Burning Plasma Assessment Committee. With the signing of the ITER Joint
Implementing Agreement, the International Tokamak Physics Activity (ITPA) Coordinating Committee
updated the ITER physics basis, which appeared in 2007 as nine chapters (and 413 pages) in a special
issue of Nuclear Fusion.19 The ITER design review also resulted in topics affecting near-term
procurement arrangements including poloidal field coil requirements, vertical stability, the effect of
toroidal field ripple on thermal confinement, first wall material choice, disruptions, and disruption
mitigation. 20
Shortly after an international design review was completed in 2008, ITER construction began in2010 in Cadarache, France.21 In 2012, by French Order, ITER became the first of a kind licensed basic
nuclear fusion facility.22
Management Reforms and the Updated ITER Cost and Schedule
Recent U.S. fusion energy strategic planning has been difficult because ITER construction costs
have increased significantly and the construction schedule has significantly drawn-out. The increased
construction cost for ITER has forced choices among program priorities and limited funding for new
facilities.
In May 2013, a bipartisan group of leaders in the U.S. Senate requested the Government
Accountability Office to investigate the cost and feasibility of ITER and its effect on U.S. fusion
programs.23 The senators wrote, “At a time when federal budgets for research are likely to be constrained
for the foreseeable future, concerns have been raised that funding for other U.S. fusion energy science
programs and user facilities have, and may continue to be, cut to pay for increasing ITER costs.” The
GAO recommended24 that “DOE formally propose the actions needed to set a reliable international
project schedule and set a date to complete the U.S. fusion program’s strategic plan.”

18

ITER Physics Basis Editors, ITER Physics Expert Group Chairs and Co-Chairs, ITER Joint Central Team,
Chapter 1: Overview and summary, Nuclear Fusion 39, 2137 (1999); https://doi.org/10.1088/0029-5515/39/12/301.
19
K. Ikeda, (2007), “Preface: Progress in the ITER Physics Basis,” Nuclear Fusion 47, (2007);
http://doi.org/10.1088/0029-5515/47/6/E01
20
R. Hawryluk, et al., “Principal physics developments evaluated in the ITER design review,” Nuclear Fusion
49, 065012 (2009); http://doi.org/10.1088/0029-5515/49/6/065012.
21
M. Banks, “Construction begins, but ITER's costs spiral,” Phys. World, 23(7), 10 (2010).
22
P. Wouters et al (2017), “Implementation at ITER of the French Order of 7 February 2012, concerning basic
nuclear installations within the European Domestic Agency,” Nucl. Fusion 57, 100401;
https://doi.org/10.1088/1741-4326/aa64fc
23
See Newsroom Report from U.S. Senate Committee on Energy and Natural Resources, May 3, 2013,
available online at https://www.energy.senate.gov/public/index.cfm/2013/5/senators-request-gao-investigation-ofcosts-at-experimental-fusion-reactor
24
U.S. Government Accountability Office, Fusion Energy: Actions Needed to Finalize Cost and Schedule
Estimates for U.S. Contributions to an International Experimental Reactor, Report to Congress, GAO-14-499,
Washington, D.C., June 2014; available online https://www.gao.gov/products/GAO-14-499.

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In response to cost and schedule concerns, the ITER Council charged an independent team,chaired by William Madia, former director of Oak Ridge National Laboratory and Stanford University
vice president for the Stanford Linear Accelerator Center, to determine the causes for ITER’s cost
increases and schedule delays and to make management recommendations. These recommendations
resulted in significant management improvements by the ITER Council and the appointment of Bernard
Bigot as the new ITER director in March 2015. The ITER Council approved a new Updated Long-Term
Schedule (ULTS) to first plasma in June 2016, and the U.S. DOE was able to approve the project
execution plan for U.S. contributions to ITER in January 2017.25 A measure of the success of ITER’s
management reforms is the fact that two years after the creation of the updated long-term schedule, theproject remains on schedule for first plasma in 2025 and, since January 2016, has achieved all 33
scheduled project milestones.26
While ITER management reforms have been successful, recent strategic planning efforts in the
United States have been less successful. As noted by the 2014 GAO report, “Without a strategic plan for
the U.S. fusion program, DOE does not have information to create an understanding among stakeholders
about its plans for balancing the competing demands the program faces with the limited available
resources or to help improve Congress’ ability to weigh the trade-offs of different funding decisions for
the U.S. ITER Project and overall U.S. fusion program.”
Responding to a request from the Office of Science, the FESAC Subcommittee on the
Prioritization of Proposed Scientific User Facilities for the Office of Science27 recommended three new
U.S. facilities as “absolutely central” to world-leading fusion science: (i) a fusion materials irradiation
facility, which would “transform nuclear material science and address critical gaps in irradiation
capability needed to qualify materials for future science missions”; (ii) a fusion nuclear science facility(FNSF) , which would “provide the first-ever access to the integrated controlled thermonuclear fusion
environment, which is characterized by strong couplings among high temperature plasma properties,
plasma-material interactions, fusion neutron science and extreme material alterations and damage”; and(iii) a quasi-symmetric stellarator experiment, which would “evaluate a pathway toward producing steady,quiescent magnetically-confined fusion plasmas by scientific optimization of the underlying toroidal
magnetic field geometry”. Each of these recommended facilities would have created new opportunities toenhance or establish U.S. leadership in plasma and fusion science; however, none were adopted or
pursued.
Then, responding to a Congressional request in the FY2014 Omnibus Appropriations Act, theU.S. DOE Office of Science asked FESAC to prioritize among research program elements defined by
U.S. DOE FES assuming continued participation in ITER and include views on new facilities, initiatives,and facility closures. The resulting FESAC Strategic Panel Report28 was controversial and recommended
a strategy that would “transition the U.S. to a fusion energy program bounded by realistic budgets” andthe start of a fusion nuclear science subprogram that would provide the scientific and technological basis
for a Fusion Nuclear Science Facility (FNSF) as a critical step towards commercial power. In its
transmittal letter, the Acting Chair of FESAC at the time wrote, “the lack of adequate consensus on toplevel vision, strategy, and priorities makes it difficult for more technically oriented groups … to achieve
widespread acceptance of recommended strategic initiatives and associated program-wide FES
investments.”
25

DOE, Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, Office of Science,
Fusion Energy Sciences, Washington, D.C., January 2017.
26
ITER Council Press Release (21 June 2018), available online:
https://www.iter.org/doc/www/content/com/Lists/list_items/Attachments/777/2018_06_IC-22.pdf
27
DOE, Report of the FESAC Subcommittee on the Prioritization of Proposed Scientific User Facilities for the
Office of Science, (March, 2013), available online:
https://science.energy.gov/~/media/fes/fesac/pdf/2013/FESAC_Facilities_Report_Final.pdf
28
DOE, Report on Strategic Planning: Priorities Assessment and Budget Scenarios, (October 2014), online:
https://science.energy.gov/~/media/fes/fesac/pdf/2014/October/FESAC_strategic_planning_rept_dec14.pdf

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The U.S. DOE/FES presented its current vision for fusion research to Congress in 2015.29 The
overall mission is to “expand the fundamental understanding of matter at very high temperatures anddensities and build the scientific foundation needed to develop a fusion energy source.” United States
fusion research emphasizes two frontiers in burning plasma science: “the physics of self-heated burning
plasma state” using ITER as the vehicle for gaining access to this state, and the “great scientific challenge
for fusion is to develop materials that can tolerate the extreme conditions created by burning plasma in afusion reactor.” The majority of the U.S. DOE/FES program budget contributes to developing thepredictive understanding needed for ITER operations and providing solutions to high‐priority ITER
research needs. A smaller element, called “Discovery Plasma Science,” represents about 15% of theannual fusion budget and supports research that advances fundamental understanding of ionized matter, or
plasma, in support of non-fusion applications. The U.S. DOE Office of Science Ten-Year Strategic Vision
to Congress in 2015 emphasizes three continuing research thrusts: controlling transient events, theinterface between fusion plasma and the surrounding material structures, and experimentally validated
predictive simulations using massively parallel computers. This Ten-Year Strategic Vision benefited fromthree community workshop reports on: (i) Science Challenges and Research Opportunities in Plasma
Materials Interactions,30 (ii) Integrated Simulations for Magnetic Fusion Energy Sciences,31 and (iii)
Transients in Tokamak Plasmas.32 In addition, FESAC completed a report titled Applications of Fusin
Energy Sciences Research: Scientific Discoveries and New Technologies Beyond Fusion,33 which
identified areas of fusion energy sciences with broad impact on fields of science, technology andengineering not directly associated with fusion energy. While the U.S. DOE Office of Science Ten-Year
Strategic Vision highlights important areas of research for the next decade, the U.S. DOE has notpresented a plan for research and technology programs needed to progress beyond ITER to a source of
fusion power nor started a fusion nuclear science subprogram leading to a new facility and to progress
towards commercial power that was recommended by FESAC.34
At the end of 2015, the question of U.S. partnership in the ITER project was still unresolved, andCongress requested “the Secretary of Energy to submit to the Committees on Appropriations of bothHouses of Congress a report recommending either that the Unites States remain a partner in the ITER
project after October 2017 or terminate participation.”35 The Secretary’s report was delivered to Congressin May 201636 and opened with the statement, “ITER remains the best candidate today to demonstratesustained burning plasma, which is a necessary precursor to demonstrating fusion energy power.” The
Secretary of Energy recommended that the U.S. remain a partner in the ITER project through FY 2018
and acknowledged the significant construction progress made at ITER and the substantial improvements
DOE, The Office of Science’s Fusion Energy Sciences Program: A Ten‐Year Perspective, Report to Congress,
Washington, D.C., December 2015.
30
U.S. DOE/FES Report on Science Challenges and Research Opportunities in
Plasma Materials Interactions (May, 2015); available online athttps://science.energy.gov/~/media/fes/pdf/workshop-reports/2016/PMI_fullreport_21Aug2015.pdf.
31
U.S. DOE/FES Report on Integrated Simulations for Magnetic Fusion Energy Sciences (June, 2015);
available online at https://science.energy.gov/~/media/fes/pdf/workshopreports/2016/ISFusionWorkshopReport_11-12-2015.pdf.
32
U.S. DOE/FES Report on Transients in Tokamak Plasmas (June 2015); available online athttps://science.energy.gov/~/media/fes/pdf/program-news/Transients_Report.pdf.
33
FESAC Report (2015) on Applications of Fusion Energy Sciences Research Scientific Discoveries and New
Technologies Beyond Fusion; available online athttps://science.energy.gov/~/media/fes/fesac/pdf/2015/2101507/FINAL_FES_NonFusionAppReport_090215.pdf.
34(p. 18) DOE, The Office of Science’s Fusion Energy Sciences Program: A Ten‐Year Perspective, Report toCongress, Washington, D.C., December 2015.
35
Consolidated Appropriations Act, 2016, (129 STAT. 2410), Public Law 114-113, December 19, 2015.
36
U.S. Department of Energy, U.S. Participation in the ITER Project, Report to Congress, Washington, D.C.,
May 2016.
29

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of ITER project management, but also noted significant technical and management risks remain.
Continued ITER membership of the Unites States past FY 2018 awaits determination if project
performance will be sustained and whether the larger costs needed for U.S. obligations for ITER
construction can be accommodated in future budgets for the DOE Office of Science. Additionally, theSecretary’s report requested advice from the National Academies and the establishment of the Committee
on a Strategic Plan for U.S. Burning Plasma Research, and the J. Stephen Binkley, acting director of the
U.S. DOE Office of Science, requested a report from FESAC “identifying the most promisingtransformative enabling capabilities for the U.S. to pursue that could promote efficient advance towards
attractive fusion energy.” 37
The project cost and schedule for the U.S. contributions to ITER first plasma construction were
finalized in January 2017 and detailed in the Project Execution Plan for the U.S. Contributions to ITER
Subproject-1.38 The DOE execution plan was developed by the U.S. DOE Office of Science based upon
the Updated Long-Term Schedule (ULTS) to first plasma. The ULTS was approved by the ITER Council
in June 2016 and independently reviewed by an ITER Council Review Group (ICRG) in April 2016.39 As
the committee notes, a measure of the reliability of ITER’s new schedule is the fact that two years after
the creation of the updated long-term schedule, the project remains on schedule for first plasma in 2025
and, since January 2016, has achieved all 33 scheduled project milestones.

37

Report of the FESAC Subcommittee on Transformative Enabling Capabilities Toward Fusion Energy(February 2018); available online athttps://science.energy.gov/~/media/fes/fesac/pdf/2018/TEC_Report_15Feb2018.pdf
38
DOE, Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, Office of Science,
Fusion Energy Sciences, Washington, D.C., January 2017.
39
ITER Council Working Group on the Independent Review of the Updated Long-Term Schedule and Human
Resources (ICRG), (15 April 2016); available online
http://www.firefusionpower.org/ITER_ICRG_Report_2016.pdf.

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D
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E
Published Technical References Consulted by the Committee
Fusion energy science is an active research area as evident from the significant number ofscientific and technical publications. Since the 2004 report of the NAS Burning Plasma Assessment
Committee, over 1,200 scientific publications have appeared authored or co-authored by scientists
supported by the U.S. Department of Energy and reporting advancements in magnetic fusion research. As
noted in the committee’s Interim Report, the Nuclear Fusion Award has been given annually since 2006,
and 8 of the 12 Nuclear Fusion Awards were presented to U.S. scientists working on scenarios, transport,
stability, transient control, boundary, and pedestal physics. U.S. award recipients are Tim Luce (2006
General Atomics), Todd Evans (2008 General Atomics), Steve Sabbagh (2009 Columbia University),
John Rice (2010 MIT), Pat Diamond (2012 University of California, San Diego), Dennis Whyte (2013MIT), Phil Snyder (2014 General Atomics), and Rob Goldston (2015 Princeton University). The
significant fraction of all articles published in magnetic fusion energy research are authored or coauthored by United States researchers. This included publication of the ‘Progress in the ITER Physics
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F
Summary of Input Received from the Fusion Community
The magnetic fusion community in the United States has provided numerous assessments ofresearch progress, opportunity, and strategy. The 2001 report of the NAS Fusion Science Assessment
Committee1 was informed by the two-week community Fusion Summer Study held in Snowmass,
Colorado, July 20-23, 1999. The 2004 report of the NAS Burning Plasma Assessment Committee2 wasinformed by a second Fusion Summer Study also held in Snowmass, Colorado, July 8-19, 2002.3 The
2008 report of the NAS Committee to Review U.S. Fusion Community Participation in the ITER Program
was informed by a community process organized by the U.S. Burning Plasma Organization.4 The 2007
report of the FESAC subcommittee for Priorities, Gaps and Opportunities towards a Long-Range
Strategic Plan for Magnetic Fusion Energy5 was followed by a U.S. DOE sponsored workshop report
prepared with input from more than two hundred fusion scientists assembled to define and characterize
the research activities that advance fusion as a practical source of energy.6 The most recent U.S. DOE
Office of Science Ten-Year Perspective on the fusion energy sciences program prepared for Congress was
informed by the reports from four community workshops: Plasma Materials Interactions (2015),
Integrated Simulations for Magnetic Fusion Energy Sciences (2015), Transients (2015), and Frontiers of
Plasma Science (2017).7
Like these previous research planning efforts, the committee also benefited from community andexpert input. Input from the fusion community was provided in three ways: (i) white papers andcomments contributed through direct online submission to the NRC, (ii) technical presentations to thecommittee during seven open public meetings, and (iii) summary reports from two week-long community
workshops: July 24-28, 2017 held at the University of Wisconsin at Madison, WI and December 11-15,
2017 hosted by the University of Texas at Austin, TX. All of these presentations were made public.
Appendix B lists the technical presentations to the committee during open public meetings. A list of thosepresentations contributed through online submission and as a result of the community workshops areprovided at the end of this appendix.
The input resulting from the community workshops, titled “U.S. Magnetic Fusion Research
Strategic Directions,”8 deserve special mention. The goals of the workshops were to discuss, debate, anddevelop critical technical information required for the development of a strategic plan, including program
1

National Research Council. 2001. An Assessment of the Department of Energy's Office of Fusion Energy
Sciences Program. Washington, DC: The National Academies Press. https://doi.org/10.17226/9986.
2
National Research Council. 2004. Burning Plasma: Bringing a Star to Earth. Washington, DC: The National
Academies Press. https://doi.org/10.17226/10816.
3
Information on the Fusion Summer Studies are online at https://fire.pppl.gov/snowmass02.html.
4
U.S. Burning Plasma Organization, Planning for U.S. Fusion Community Participation in the ITER Program,
June, 2006. https://www.burningplasma.org/resources/ref/fp/EPAct_final_June09.pdf
5
U.S. FESAC Report of Priorities, Gaps and Opportunities: Towards a Long-Range Strategic Plan for
Magnetic Fusion Energy, November 2007,https://science.energy.gov/~/media/fes/fesac/pdf/2007/Fesac_planning_report.pdf
6
U.S. DOE Office of Science, Research Needs for Magnetic Fusion Energy Sciences, June 8-12, 2009,https://science.energy.gov/~/media/fes/pdf/workshop-reports/Res_needs_mag_fusion_report_june_2009.pdf
7
All four community workshop reports are available online from: https://science.energy.gov/fes/communityresources/workshop-reports/.
8
See online website for community workshops on U.S. Magnetic Fusion Research (MFR) Strategic Directions,
https://sites.google.com/site/usmfrstrategicdirections/home

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mission and goals, and to present and discuss opportunities to achieve those goals through the pursuit ofvarious scientific and technical programs. These workshops were highly successful and involved
hundreds of researchers across the country. Workshop participants prepared detailed technical reports onnine strategic research program elements, descriptions of various strategic approaches to fusion researchplanning, and summaries of important working group topics such as the impact of ITER access to U.S.
fusion scientists and the requirements for attractive fusion power systems. These technical descriptions
underwent an informal peer review and described strategic elements of a U.S. fusion research program
responding to the committee’s task.
In a letter to the committee from the workshop co-chairs, reported, “over 200 members of thecommunity have participated in this activity so far, submitting white papers and debating technicalinitiatives, missions, research pathways, and strategic principles in working groups and in two week-longworkshops.” U.S. researchers engaged in constructive debate of many of the challenging technical andstrategic issues under study by the committee. While the workshop participants documented several
strategic elements in technical white papers, the workshop co-chairs noted “a sustained effort well beyond
the time horizon of your panel will be necessary for us to reach community consensus on key aspects of astrategic plan for the U.S. program.” The technical descriptions for each strategic element were preparedby knowledgeable experts and updated to accommodate review comments. The committee is grateful forthe considerable effort by white paper authors and their intent to inform rather than to advocate and toconvey, as far as possible, a broader view of the U.S. research community’s strategic directions activity.
These papers have been posted for a period of time on a public web site:
https://sites.google.com/site/usmfrstrategicdirections/strategic-element-white-papers
SUMMARY OF PUBLIC INPUT PRESENTATIONS TO THE COMMITTEE
Presentations to the Committee
Meeting 1 - Washington, D.C.
 Perspectives on Burning Plasma Research – Chuck Greenfield, Amanda Hubbard, United States
Burning Plasma Organization
 Context for an NAS Study on Burning Plasma Research and A Magnetic Fusion Strategy Edumund Synakowski, DOE Office of Science
Meeting 2 - Irvine, California
 Perspectives from the University Fusion Association - David Maurer, Auburn University
 A Reinvigorated U.S. Fusion Energy Program - Stewart Prager, Princeton University
 Perspective on Fusion Energy Strategy - Tony S. Taylor, General Atomics
 Perspectives from the US ITER Project - Ned Sauthoff, US ITER Project Office Response to the NAS Committee for a Strategic Plan for U.S. Burning Plasma Research - Phil
Ferguson, US Virtual Laboratory for Technology (VLT)
Meeting 3 - Austin, Texas Further Context for NAS Burning Plasma Study - James W. Van Dam, DOE Office of Science The Road Not Taken -- Yet - D. Whyte, MIT Plasma Science and Fusion Center Strategic Plan for U.S. Burning Plasma Research - R.J. Hawryluk and M.C. Zarrnstoff, PPPL
Meeting 4 - ITER, France ITER Engineering Science and Breakthroughs - Gyung-Su Lee, ITER
 ITER: The Way to a New, Clean, Safe, and Near-Unlimited Energy - Bernard Bigot, ITER
 ITER Project Management - Hans H. Altfeld, ITER
 The Science of ITER - Tim Luce, ITERPREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION
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EU DEMO Design and R&D Activities: Progress and Updates - Gianfranco Federici,
EUROFusion
Meeting 5 - General Atomics, San Diego Challenges and Strategy for Development of FNST: Blanket/FW & Tritium Fuel Cycle –Mohamed Abdou, UCLA On TAE’s Path to Fusion: A Private-Sector Perspective – Michl Binderbauer, TAE Technologies
 A Mission to Discover the Plasma Solutions for Future Fusion Reactors - RJ Buttery, General
Atomics
 General Atomics Perspective on the Strategic Plans for U.S. Fusion Energy Development - David
Hill, General Atomics
 Perspective on Magnetic Fusion Energy Directions from Early Career Fusion Scientists Multiple Perspectives
 Korean Fusion Energy Development Strategy - Y.S. Hwang, Center for Advanced Research in
Fusion Reactor Engineering Chinese Fusion Energy Strategy - J. Li, Institute of Plasma Physics
 Research and Development Policy on Fusion Energy in Japan - Yuichi Ogawa, The University ofTokyo A Fusion Program Strategy for Timely Fusion Energy Development - Mickey Wade, General
Atomics
Teleconference - Stellerators (March 23, 2018)
 U.S. Research on International Stellarators - Samuel A. Lazerson, Princeton Plasma Physics
Laboratory
 A Vision for an Experimental Stellarator Program in the U.S. that is a Slingshot for a Stellerator
D-T Device - Oliver Schmitz et al
Meeting 6 - Princeton Plasma Physics Laboratory (April 11-13, 2018)
 First-Wall, Plasma-Material Interaction, Liquid Metals, and Strategic Elements for Advancing
Liquid Metal Science and Technology - M.A. Jaworski, Princeton Plasma Physics Laboratory
 A New Approach to Funding, Accelerating, and Commercializing Fusion - R. Mumgaard,
Commonwealth Fusion Systems
 Magnetic Confinement-Based Fusion Research in the United States - Soren Prestemon, Lawrence
Berkeley National Laboratory
 Plasma-Materials and Divertor Options for Fusion - J. Rapp, Oak Ridge National Laboratory
 SPARC: A Critical Step on the High-Magnetic-Field Path to Practical Fusion Energy - Martin
Greenwald, Commonwealth Fusion Systems
 Long-term Fusion Vision, Strategy, and Role - M.C. Zarnstorff, Princeton Plasma Physics
Laboratory
 Trying for Upside Potential in Controlling Fusion - Nat Fisch, Princeton University
 Advanced Scientific Computing Strategy for Fusion - Amitava Bhattacharjee, Princeton Plasma
Physics Laboratory
 NSTX-U: An Essential Science Facility for US Fusion Innovation - S. Gerhardt, Princeton Plasma
Physics Laboratory
 Options and Strategy Towards Fusion Net Electricity - Jonathan Menard, Princeton Plasma
Physics Laboratory

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Public Input
Strategic Element White Papers - US Magnetic Fusion Research Strategic Directions
 Letter to the Committee - Hutch Neilson, Mickey Wade, Dave Maurer on behalf of the Magnetic
Fusion Research Strategic Directions Activity
 Entering the Burning Plasma Frontier, Chuck Greenfield, Dale Meade, Chuck Kessel Developing HTS Magnets for Fusion Applications, Joe Minervini, Yuhu Zhai, Xiaorong Wang,
Robert Duckworth Magnetic Configuration Research: A Foundation Element for the Development of Magnetic
Fusion Energy, John Sarff, Uri Shumlak
 Quasi-Symmetric Stellarators as a Strategic Element in the US Fusion Energy Research Plan,
David Gates, David Anderson, Dave Maurer, Chris Hegna
 Importance of Theory, Computation, and Predictive Modeling in the US Magnetic Fusion Energy
Strategic Plan, Fatima Ebrahimi, Gary Staebler, Paul Bonoli, François Waelbroeck, Chris Hegna
 Elements of a US R&D Plan to Solve Plasma-Material Interaction Challenges for Magnetic
Fusion Energy, Brian LaBombard, Peter Stangeby, Dick Majeski, Jean Paul Allain
 Elements of a US R&D Plan to Develop Fusion Nuclear Materials, Steve Zinkle, Yutai Katoh,
Richard Nygren
 Tritium Fuel Cycle, Chuck Kessel, Arnie Lumsdaine Sustained High Performance Tokamak as the Leading Magnetic Fusion Path to Net Electricity
Production, Richard Buttery, Steve Sabbagh, Earl Marmar
Strategic Approach White Papers
 Use Present Physics and Technology Basis for DEMO - Working Group for Strategic Approach 1
for the 2017 U.S. Magnetic Fusion Research Strategic Directions Workshops, S. Zinkle, W.
Solomon, D. Newman
 Delivering Key Technical Achievements, then DEMO - Working Group for Strategic Approach 2
for the 2017 U.S. Magnetic Fusion Research Strategic Directions Workshops, G. Navratil, C.
Collins, N. Howard
Working and Discussion Group White Papers - US Magnetic Fusion Research Strategic Directions
 Whitepaper on Principles, Values, Metrics and Criteria for the Development of Magnetic Fusion
Energy - Working Group 1, Laila El-Guebaly, Lauren Garrison, Robert Goldston, Martin
Greenwald, Walter Guttenfelder, Scott Hsu, Hantao Ji, Ilon Joseph, Karsten McCollam, Brad
Merrill, Craig Michoski, Hutch Neilson, Francesca Turco.
 Whitepaper on Technical and Programmatic Access to ITER, Working Group 2.
 Whitepaper on Fusion Market Attractiveness, Working Group 3, David Hatch, Scott Hsu, andMark Tillack (Co-chairs).
 Whitepaper Summary of the Quasi-Symmetric Stellarator Program - Working Group 4 for theAustin USMFR Discussion Group 5 Summary of USMFRSD Workshop in Austin, TX (January 12, 2018) - D.
Sutherland et. alContributed White Papers
 Plasma Pinch (Physics World) - John E. Allen, University of Oxford
 Two Comments on the NAS Interim Report on a Strategy Plan of U.S. Burning Plasma Research Stephen E. Bodner, (Ret.) Navy Research Laboratory Whitepaper on Proposed Strategic Element for U.S. Magnetic Fusion Research - M. R. Brown,
B. Chapman, H. Gota, S. C. Hsu, R. Majeski, H. McLean, B. A. Nelson, U. Shumlak
 The Advanced Tokamak Path to a Compact Fusion Power Plant – R.J. Buttery, et. al, General
Atomics

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Comments on A Strategic Plan for U.S. Burning Plasma Research - F.F. Chen, Professor
Emeritus, University of California, Los Angeles
DOE Should Strongly Support Physics Research and Technology Development for AdvancedFuel FRCs - S.A. Cohen, Princeton Plasma Physics Laboratory
Brief Words on U.S. Fusion Research - Clesio Ismerio de Oliveira, Eletrobras CGTEEHistorical Perspective on the United States Fusion Program - Stephen O. Dean, Fusion Power
Associates
Pilot Plant: A Shortened Path to Fusion Power - Stephen Dean et. al, Fusion Power Associates,
ORNL, MIT, Canadian Fusion Fuels Technology Project, Ebasco Services, Kurchatov Institute ofAtomic Energy
Essential Criteria for Fusion Power Plants - Laila El-Guebaly (UW-Madison), Ilon Joseph(LLNL), Brad Merrill (Idaho National Laboratory), Scott Hsu (LANL)Worldwide Timelines for Fusion Energy - Laila El-Guebaly, University of Wisconsin, Madison
Stellarator Research Opportunities - National Stellarator Coordinating Committee
Whitepaper on Proposed Strategic Element for U.S. Magnetic Fusion Research: Opportunities
Presented by Magneto-Inertial Fusion - Scott Hsu et al.
The High-Field Path to Practical Fusion Energy - M. Greenwald et. al, Massachusetts Institute ofTechnology Plasma Science and Fusion Center
Fusion Research: Time to Set a New Path - Robert L. Hirsch, (Ret.) Science Applications
International Corporation
Revamping Fusion Research - Robert L. Hirsch, (Ret.) Science Applications International
Corporation
A Tritium Research Program in Support of Burning Plasma Science and Fusion Energy - P. W.
Humrickhouse et. al, Idaho National Laboratory
The ITER Power Amplification Myth - Steven B. Krivit, New Energy Times
Harsh Environment Microwave Diagnostics for Reactor Plasmas - N.C. Luhmann, Jr et al.
Letter to the Strategic Plan for U.S. Burning Plasma Committee - Shigekazu Matsuura,International Nuclear and Fusion Energy Affairs Division, Japan
Letter to Co-Chairs for Strategic Plan for U.S. Burning Plasma Committee - Bruno Coppi,
Ignitor Program
Letter to the Strategic Plan for U.S. Burning Plasma Committee - Matthew Reinke, Oak Ridge
National Laboratory
Letter to the Academy of Sciences on Fusion Review - Walter L. Sadowski, (Ret.) Office of
Fusion Energy Sciences, DOE
Letter to NAS - Bruno Coppi
Collection of Documents by the University Fusion Association - sent by David A. Maurer,
University Fusion Association
Burning Plasma Physics and the U.S. Strategic Plan for Magnetic Fusion Energy - Dale Meade,
Princeton Plasma Physics Laboratory
A Vision for Attaining and Exploring a Burning Plasma for Attractive Fusion Power - Dale
Meade
A New Tandem Mirror Concept with High Fusion Power Gain - T.C. Simonen and R.W. Moir,
LLNL, Vallecitos Molten Salt Research
White Paper on Magnetic Fusion Program - Weston M. Stacey, Georgia Institute of Technology
Be Bold: An Alternative Plan for Fusion Research - G.A. Wurden, Los Alamos National
Laboratory
Perspective on Magnetic Fusion Energy Directions from Early Career Fusion Scientists Multiple Authors

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Follow-Up Polling of the Early Career Fusion Scientist Community in Response to NAS Panel
Feedback - Chris Holland et al.
ITER is a Showcase for the Drawbacks of Fusion Energy - Daniel Jaasby
MIT's Nuclear Cure-Alls - Daniel Jassby
Tritium Breeding Strategy for Advanced Fusion Power Plants - L.A. El-Guebaly
Reshaping the Fusion Radwaste Management Approach - L. A. El-Guebaly et al.
Important Gaps in the ST and AT Programs - Roger Raman
Comments on the Interim Report - S.A. Cohen
White Paper on U.S. Domestic Tokamak Program - C.M. Greenfield, D.N. Hill, M.R. Wade
Accelerating Fusion Through Integrated Whole Device Modeling - Amitava Bhattacharjee et al.
Development of a Steady State Fusion Core: The Advanced Tokamak Path - R J Buttery et al.,General Atomics, LLNL, ORNL, Oak Ridge Associated Universities
Sustained High Performance Tokamak as the Leading Magnetic Fusion Path to Net Electricity
Production - R.J. Buttery et al.
Accelerated Compact Fusion Development and Innovations Leveraging Spherical Tokamaks Steven Sabbagh, Columbia University
A U.S. Strategic Plan for Timely Fusion Energy Development - M.R. Wade, General Atomics
Need For 14 MeV Neutrons - Mohamed Abdou
Pre-FNSF Research and Development, C.E. Kessel, Princeton Plasma Physics Laboratory
The Fusion Nuclear Science Facility (FNSF) is a Critical Step Before Proceeding to Larger andElectricity Producing Fusion Plants - C.E. Kessel, Princeton Plasma Physics Laboratory
Producing Electricity in a Fusion Nuclear Science Facility or Similar - C.E. Kessel, Princeton
Plasma Physics Laboratory
A Brief Historical Summary of Fusion Alternatives - Charles W. Hartman, Harry McLean, Uri
ShumlakWhy Fusion? - Robert J. Goldston, Princeton Plasma Physics Laboratory
A Mid-Scale Quasi-Helically Symmetric Experiment Would Significantly Accelerate Fusion
Development Through the Stellarator Line - D.T. Anderson et. al, University of WisconsinMadison

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G
Major Research Facilities of the United States and Other Nations
This appendix briefly describes major research facilities within the United States and of othernations. These facilities include: the DIII-D facility (San Diego, CA), NSTX-U (Princeton Plasma
Physics Laboratory), smaller U.S. confinement research facilities, and the larger devices in Europe andAsia. All fusion research experiments with superconducting magnets are located outside the UnitedStates: EAST (China), KSTAR (ROK), WEST (formerly Tore Supra, located in France), Large Helical
Device (LHD, located in Japan), and Wendelstein 7-X (Germany). The JT-60SA superconducting
experiment is under construction in Japan and operation is expected to begin shortly after 2020. Recently,
Italy announced intention to design and construct the superconducting Divertor Tokamak Test Facility(DTT).
DIII-D
DIII-D1,2 is a medium-sized tokamak at conventional aspect ratio (R/a ≥ 2.5) that is the largest
magnetic fusion research experiment in the U.S. It is a multi-institutional user facility whose primaryresearch goal is to:Provide solutions to physics and operational issues critical to the success of ITER,
Develop the physics basis for steady-state tokamak operation required for efficient power
production,
Contribute substantially to the technical basis for a fusion nuclear science facility, andAdvance the fundamental understanding and predictive capability of fusion science.

The DIII-D project commenced in 1986, and its technical capabilities have continually evolved sothat DIII-D is presently a flexible device that can study confinement, stability and divertor physics with avariety of heating and current drive techniques. This, in turn, allows for the development of the highperformance, advanced tokamak concept, which requires targeted simultaneous control of multiple
plasma profiles both in the plasma core and at the edge. Near-term research on DIII-D addresses thedevelopment of plasma scenarios scalable to the high fusion gain ITER target. Longer-term research
focuses on developing techniques to produce stable, high-performance, steady-state (i.e., non-inductive)
operation for ITER and beyond.
DIII-D has a major and minor radius of 1.67 and 0.67 m respectively, with a nominal aspect ratioof 2.5. It has a maximum operating capacity of 2.2 T toroidal magnetic field and 3 MA plasma current,
although it generally operates at lower currents, ≤2 MA. Eighteen field-shaping coils operated by aplasma control system provide great flexibility in plasma shape, discharge evolution, and divertor
configuration. Divertor cryopumps control the plasma density. DIII-D presently has 26 MW of external
heating capability, split between 20 MW of neutral beam (NB) heating and 6 MW of electron cyclotron(EC) heating and current drive. The neutral beams are configured on and off-axis, and in the co- andcounter-current direction to provide a range of torque and neutral beam driven non-inductive current
profiles. Another key feature of DIII-D is the set of internal and external coils that can provide a wide
spectral range of applied 3D magnetic perturbations for edge-localized mode (ELM) suppression and12

Buttery, R., et al., Nucl. Fusion 55 104017 (2015)
Solomon, W., et al., Nucl. Fusion 57 102018 (2017)

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FIGURE G.1 The DIII-D National Fusion Facility, operated by General Atomics for the Departmentof Energy, is the largest magnetic fusion experiment in the United States. See http://www.ga.com/diiid-national-fusion-facility-begins-transformation-to-prepare-for-future-reactors

other edge profile control studies. Shattered pellet injection and argon pellet systems are employed for
disruption and runaway electron mitigation, a lithium and boron “dropper” is used for wall-conditioning,
and a laser blow-off instrument is available for impurity transport studies. DIII-D has an outstanding,comprehensive set of core, edge and divertor diagnostics. A close relation between Theory andExperiment enables the data to be readily used to validate first-principles physics simulations for thedevelopment of high-confidence predictive tools.
A few examples from the diverse, multi-faceted research program are given below.
In ITER, unmitigated ELMs will rapidly erode first-wall materials. DIII-D was the first tokamak
to use 3D magnetic perturbations to suppress ELMs. Design of the ITER 3D coils relied heavily on DIIID results. In support of developing operational scenarios for ITER, many recent experiments explore
stability and confinement in plasmas with low injected torque, and with significant electron heating, as is
expected in ITER. In particular, validation of transport models against ITER baseline discharges in DIIID have revealed the importance of certain drift-wave modes that cause particle transport into the center ofthe plasma. This model3, when used to simulate ITER scenarios, predicts a peaking of the density profile,which is a necessary condition for achieving the Q = 10 ITER target4. Electron cyclotron heating wasshown to be effective in expelling impurities from the core of these plasmas5.
Demonstration of non-inductive scenarios with high confinement is another major program
element. Experiments in the “hybrid” operational regime have achieved a normalized pressure of βN = 3.7
with a confinement enhancement factor of 1.6 and zero loop voltage, indicating that a significant portionof the plasma current was self-driven6.
Divertor and plasma-material solutions are key for a successful fusion reactor. A recent upgrade
to the upper divertor module allowed DIII-D to study the physics of the small angle slot (SAS)configuration. This configuration can cause the divertor to radiatively “detach” from the hot upstream
3

Staebler, F.M. et al., Phys. Plasmas 12 102508 (2005)
Grierson, B., et al., Phys. Plasmas 25 022509 (2018)5
Unterberg, E.A., et al., “Characterization of divertor tungsten sourcing and transport into the SOL and core for
DIII-D ELMy H-mode conditions”, submitted to Nucl. Fusion (2017)6
Turco, F., et al., Phys. Plasmas. 22 056113 (2015)
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plasma at lower densities, giving lower temperatures across the divertor region, and presents a potential
divertor solution to mitigate high heat fluxes. In materials studies, tungsten inserts installed during a
metal-rings campaign provided measurements of tungsten erosion, migration, and redeposition.
The DIII-D program emphasizes scientific understanding to develop a predictive capability that
improves fusion performance. A model was developed that explains the observed height and width of thepressure “pedestal” at the plasma edge when the tokamak operates in the “H-mode” confinement
regime7,8. Further analysis suggested that, by judicious choice of the plasma shape and discharge
evolution, access to a higher pressure “super H-mode” was possible. Subsequent experiments accessed
this higher performance regime, and produced plasmas with equivalent QDT of up to 0.6.
Modifications of DIII-D are currently underway. A major goal is demonstration of a steady-state
condition with high confinement and pressure. To drive more off-axis current, one neutral beamline isbeing reoriented to inject off-axis. New methods to use plasma waves to drive current off-axis are also
being prepared, including installation of a high-power helicon antenna.
Organizationally, DIII-D is managed by a private company, General Atomics (GA). Multiple
national-laboratory and universities, as well as GA employees, constitute the scientific staff. Generally,
GA employees operate the major systems, with several major subsystems the responsibility of national
laboratory teams; diagnostic systems are the responsibility of university, national laboratory, and GA
personnel. Experiments are selected after a “Research Opportunities Forum” that is open to all, review by
a “Research Council” with experienced team members from GA, laboratories, and universities, and final
allocations by GA management. Experiments are conducted by multi-institutional teams that often
include international visitors. The research program is influential. As a measure of impact, consider thepapers selected for oral presentations at the most recent IAEA Fusion Energy Conference (the highest
visibility conference in the field). Of 42 experimental magnetic fusion papers, 15 utilized DIII-D data, themost of any facility in the world.
NSTX-UThe National Spherical Torus Experiment – Upgrade (NSTX-U)9 is one of 17 tokamaks designed
to operate in the low aspect ratio regime. It is a high-powered, medium-sized device that is one of the twolargest and most capable low aspect ratio tokamaks in the world, the other being MAST-U10 in the U.K.
The mission of NSTX-U is to:Advance the spherical tokamak (ST)11 as a candidate for a Fusion Nuclear Science Facility(FNSF)Develop solutions for the plasma-material interface, including the snowflake divertor andlithium/liquid metal plasma facing components (PFCs)
Advance toroidal confinement physics predictive capability for ITER and beyond
Develop the ST for fusion energy production, for example as an ST Pilot Plant.

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Snyder, P.B., et al., Phys. Plasmas 16 056118 (2009)
Snyder, P., et al., Nucl. Fusion 51 103016 (2011)9
Menard, J.E., et al., Nucl. Fusion 52 083015 (2012)10
Morris A.W. IEEE Trans. Plasma Sci. 40 682 (2012)11
Peng, M. and D. Strickler, Nucl. Fusion 26 769 (1986)
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FIGURE G.2 The U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) runs the
National Spherical Torus Experiment Upgrade (NSTX-U), which has undergone an upgrade allowing
experimental tests of high-performance plasma under conditions of extreme heat and power. See
https://www.pppl.gov/nstx.

The ST concept, in which R/a ≤ 2, offers a potential development path for a more compact andlower-cost energy production system and/or materials testing facility through optimization of the fusion
triple product nT, where n is density, T is temperature and  is energy confinement time. In particular,
improvements in energy confinement are inherent in the ST due to the stabilizing properties of its hightoroidicity, high plasma flow velocities and high flow shear. STs also naturally achieve high- due tooperation at lower toroidal magnetic field, and the spherical nature of the plasma configuration leads tohigh natural elongation. Also because of the low toroidal field, the fast ion population that results fromneutral beam injection in STs resides in a parameter space expected for -heated plasmas at bothconventional and low aspect ratio. These unique physics regimes, along with the compact nature of theST, which leads to stringent requirements for developing power handling and non-inductive current drive
capabilities, offers great leverage in testing tokamak physics models for improved predictive capability.
Many of the ST physics challenges were explored in NSTX12,13, the predecessor device to NSTXU. NSTX had an aspect ratio of R/a=0.85/0.68~1.25, operated with plasma currents and toroidal magnetic
fields of up to 1.5 MA and 0.55 T respectively, had pulse lengths of up to 1.5 sec, and operated in either
D+ of He++. NSTX was equipped with a three-source neutral beam capable of injecting 6 MW of D0
power at 90 keV, and up to 6 MW of High Harmonic Fast Wave RF power for heating and current drive.
Co-axial Helicity Injection (CHI) was used for non-inductive plasma startup. Close-fitting passive
conductors, coupled with application of active control algorithms using applied 3D magnetic fields as
actuators, were used to stabilize MHD instabilities and maintain high-performance operations.
NSTX made significant progress in achieving a goal of high-, long-pulse performance, including theachieving T values up to 35%, with N up to 6.5 m-T-MA-1 and N/li, a metric for maximizing bootstrap
current, to 14. Its accomplishments include14:
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Ono, M., et al., Nucl. Fusion 40 557 (2000)
Kaye, S.M., et al., Fusion Technology 36 16 (1999)
14
Kaye, S.M., Chapter 11 in “Magnetic Fusion Energy: From Experiments to Power Plants”, ed. By G.H.
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Pulse lengths up to 1 s with 60 to 65% of the current being driven non-inductively by bothbootstrap and neutral beam current drive H-mode operation with E/98y,2 values up to 1.5 andE/89p values over 2.
Confinement trends showing that performance improved with decreasing collisionality in anearly linearly inverse fashion (see Fig. 6).
Impurity transport rates near predicted neoclassical values in turbulent L-mode plasmas.
Identification and development of approaches to control neoclassical tearing modes andresistive wall modes.
Observation of different classes of fast ion-induced MHD, with modes in the conventional
Alfvén Eigenmode (AE) range of frequencies (tens of kHz), but also with frequencies of 0.5-1
MHz, near the ion cyclotron frequency.
Significant electron heating (Te0 > 6 keV) and indications of current drive with HHFW.
Noninductive startup currents of up to 400 kA using CHI.
Utilization of advanced divertor configurations (e.g., snowflake) with partial detachment to
mitigate divertor heat flux.
Use of lithium wall coatings to improve plasma performance and mitigate ELMs.

Coupled with these experimental achievements was the development of the theoreticalunderpinnings necessary for understanding the results. For instance, first-principles gyrokinetic
simulations identified the microtearing mode, which is electromagnetic in nature and exists at high-, as
the microinstability responsible for most of the energy loss from the plasma, which was through theelectron channel15. This mode becomes more stable as collisionality is reduced, consistent with the strong
increase of global confinement time with decreasing collisionality. Theory development related to the fastion-driven AE modes led to a deeper understanding of how these instabilities affect both the fast ion andthermal populations16. This understanding led to the development of models of fast ion transport that havebeen applied successfully at low and conventional aspect ratio. Furthermore, development of the theory ofkinetic stabilization of Resistive Wall Modes in NSTX17 was found to also explain stability trends atconventional aspect ratio.
NSTX-U will continue to explore physics issues critical to both low aspect ratio, but withenhanced capabilities. The toroidal magnetic field will be increased from 0.55 to 1 T, the plasma current
from 1.5 to 2 MA, and the pulse length from 1 to 5 sec. A second, more tangentially injecting neutralbeam was added, doubling the total available power up to 12 MW under normal operating conditions.
These additions make NSTX-U the most powerful ST in the world, with the highest toroidal field andhighest accessible pressure and . This will allow NSTX-U to achieve up to ten times higher fusion triple
produce (nT) and four times higher divertor heat fluxes, reaching levels expected in ITER.
The increased current, field and power will enable NSTX-U to operate at higher temperature andup to five times lower collisionality than in NSTX. Operation at reduced collisionality is critical toresolving how confinement varies with this parameter. If the favorable confinement trend withcollisionality continues at these lower values, in contrast to the weaker dependence of confinement on
collisionality at conventional aspect ratio, this would certainly be critical information for optimizing theultimate design of a tokamak reactor, and would present the low aspect ratio, high- regime as apotentially attractive one for a compact, more attractive reactor.
NSTX-U is an excellent test-bed for simulating -particle physics applicable to burning plasmas
and ITER. Neutral beam-heated NSTX-U plasmas will operate in the largest fast ion dynamic range of15

Guttenfelder, W., et al., Nucl. Fusion 53 093022 (2013)
Podesta, M., et al., Plasma Phys. Cont. Fusion 56 055003 (2014)17
Berkery, J.W., et al., Phys. Plasmas 17 082504 (2010)
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parameter space of any ST or conventional aspect ratio tokamaks, and in the regime expected for heated plasmas at both low and higher aspect ratio (see Fig. 7). Experiments on NSTX-U have alreadyshown the flexibility of the more tangential neutral beam in being able to phase space engineer the fastion distribution in pitch angle and deposition profile in order to control the fast-ion instabilities18.
NSTX-U will be the leader in assessing whether high-performance STs can be sustained without
a transformer, a critical research component since the compact nature of an ST-based Pilot Plant, forinstance, will preclude a substantial OH transformer. The flexibility of the more tangential neutral beam
will allow for additional non-inductive current with profiles that can be controlled actively. Beam torque
will induce rotation, and both active and passive stabilization of global MHD modes through the passive
conducting plate and applied 3D magnetic fields, along with production of favorable current profiles, willallow sustainment of high performance. Additional non-inductive current will be produced by the plasma
through the bootstrap effect, which can be optimized through the high N/li that will be attained, andwhich could be twice as high as that produced on NSTX. Predictive simulations indicate that 100% noninductive operation at 1 MA is possible.
While there is significant overlap between the two major ST devices, NSTX-U will focus on core
physics, and in a complementary fashion MAST-U will focus on boundary physics. MAST-U is equippedwith a significant number of PF coils that will allow for much more flexible, long-legged divertor
configurations than those that can be produced in NSTX-U. However, NSTX-U can contribute and, insome instances, lead in power exhaust studies. NSTX-U will be using solid lithium coatings to protect
PFCs from high heat fluxes, to improve confinement and to suppress ELMs, as was done in NSTX. Solidlithium injectors on both the top and bottom of the vessel will serve to double the lithium deposition overthat in NSTX. Long-term plans include the development of liquid metal divertors as a possible
transformative wall solution.
NSTX-U operated for ten weeks in 2016 and had a productive scientific campaign. However, by
the end of that period, it was discovered that one of the PF coils failed, necessitating NSTX-U to shut
down for an extended Recovery outage. The NSTX-U Recovery is ongoing, with numerous design
improvements, including modification of the vacuum chamber, in order to support flexible operations andincrease reliability to achieve key mission goals. New requirements for the divertor heat fluxes have been
defined, based on recent SOL heat flux width models. New halo currents loads have been determinedbased on data from NSTX, NSTX-U, MAST and conventional aspect ratio devices. New error field
analysis has been conducted, with the goal of optimizing both the global MHD stability and minimizing
PFC heat flux asymmetries for scenarios with large poloidal flux expansion. New designs of graphite
plasma facing components utilize castellations to reduce the mechanical stresses, allowing tiles to reachsurface temperature limits, ~1600 C. Improved divertor coil designs simplify fabrication and facilitate
turn-to-turn testing. The NSTX-U Recovery project is on track to enhance reliability and safety andprovide the highest performance ST device as a robust user facility. NSTX-U is expected to resume
operations during CY2020.
Smaller Confinement Research Facilities within the United States
Pegasus is an ultra-low aspect ratio tokamak at the Univ. of Wisconsin that operates with R~0.35
m, R/a~1.13 – 1.3 BT=0.17 T and elongation ~ 2. Its mission is to explore very high- confinement andstability, and to develop non-inductive discharge start-up techniques. Pegasus has achieved T values near
100%, and it has also achieved H-mode plasmas, with threshold powers for accessing the H-mode well
above (~15x) that predicted for the Pegasus operating parameters19,20. Localized DC helicity injection
18

Fredrickson, E.D., et al., Phys. Rev. Lett. 118 265001 (2017)
Thome, K., et al., Phys. Rev. Lett. 116 175001 (2016)20
Thome, K., et al., Nucl. Fusion 57 022018 (2017)19

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utilizing plasma guns has produced induction-free plasmas with plasma currents up to 100 kA with theplasma current scaling with injected edge current in accordance with the Taylor relaxation mechanism21.
LTX-is also a low aspect ratio tokamak which is situated at Princeton Plasma Physics
Laboratory, Princeton University, with R=40 cm, R/a~1.55, BT≤0.17 T and Ip≤100 kA that is the followon device to LTX. The purpose of LTX-is to develop the approach to using liquid lithium walls, and to
study their effect on plasma performance. LTX used lithium coatings on a high-Z wall, and it exhibited
flat electron temperature profiles and enhanced confinement without having the lithium dilute the coreplasma or radiate power22. LTX-will extend the capabilities of LTX with 700 kW of neutral beam
heating and fueling, 100 kW of ECH/EBW for electron heating, higher BT and Ip, longer pulse length, andupgraded diagnostics.
The Madison Symmetric Torus (MST)23 at the University of Wisconsin is a reversed-field pinch(RFP) physics experiment, which relies on a transient burst of current to create the plasma and theconfining magnetic fields. In the RFP, the toroidal magnetic field is weaker than the poloidal magnetic
field, and it actually reverses direction in the plasma near the edge. The mission of MST, presently aformal User Facility, is to study fusion and astrophysical implications of reconnection24, turbulence25 anddynamo formation. A 1 MW neutral beam injector will be used to heat the plasma and enable studies offast particles and their role in the reconnection process. A wide range of diagnostics is available forcharacterizing the plasma.
HSX26, also at the University of Wisconsin, is a quasi-helically symmetric (QHS) stellarator with
R=1.2 m, a=0.15 m and BT up to 1.25 T. It has up to 200 kW of EC heating, which can heat the electrons
up to 2 to 2.5 keV in the core. By nature of its QHS design, neoclassical electron thermal transport was
reduced27. Furthermore, HSX exhibited reduced damping of plasma flow28, important for ulitmately
reducing turbulence-driven transport, reduced bootstrap and Pfirsch-Schlüter currents for maintaining
plasma stability29, and good particle confinement of transpped high-energy electrons30. HSX also serves
as a flexible divertor test platform, able to produce either an island or non-resonant divertor.
HIDRA (Hybrid Illinois Device for Research and Applications) at the University of Illinois is aclassical stellarator with R=0.72 m and a=0.19 m, with magnetic fields up to 0.5 T. The main focus of
HIDRA is to study plasma-material interactions, including liquid lithium science and technology31.

21

Bongard, M., et al., “Non-solenoidal injection on the Pegasus Spherical Tokamak”,
https://www.researchgate.net/publication/318987686 (2017)
22
Boyle, D., et al., Phys. Rev. Lett. 119 015001 (2017)23
Dexter, R.N., et al., Fusion Technology 19 131 (1991)
24
Fridstrom, R., et al., Phys. Plasmas 23 062504 (2016)25
Williams, Z.R., et al., Phys. Plasmas 24 122309 (2017)26
Anderson, D., et al., Fusion Technology 27 273 (1995)
27
Canik, J.M., et al., Phys. Rev. Lett. 98 085002 (2007)
28
Gerhardt, S.P., et al., Phys. Rev. Lett. 94 105002 (2005)
29
Schmitt, J.C., et al., Phys. Plasmas 21 092518 (2014)30
Anderson, D.T., et al., Fusion Sci. and Technology 50 171 (2006)31
Andruczyk, D., et al., Fusion Sci. and Technology 68 497 (2017)

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FIGURE G.3 Experimental Advanced Superconducting Tokamak (EAST) is a superconducting
tokamak demonstrating high-fusion confinement performance in steady-state. EAST has a major
radius of 1.8 m, and the EAST superconducting magnets are energized to 320 MJ. See
http://english.ipp.cas.cn/rh/east/.

The Compact Toroidal Hybrid (CTH)32 device at Auburn University is designed to study how
MHD stability in a stellarator depends on 3D shaping of the plasma. It has R=0.75 m, a=0.29 m, BT=0.7
T, and it has independently controlled magnet coils that can produce magnetic configurations over a large
range of vacuum transforms, as well as having additional coils to control plasma shape as well as
horizontal and vertical position. There is an ohmic system that produces plasma current, and when
operated in this mode, disruptions due to vertical displacement events, density limits and low-q have been
observed33.
The mission of the HBT-EP34 device at Columbia University is to utilize an adjustable closefitting conducting wall for passive stabilization35, and applied external magnetic perturbations36 for active
control of MHD modes to study and extend the -limit. It has R=0.92 m, a=0.15 m and BT=0.35 T.
The Helimac37 is an R=1 m, BT=0.1T is a toroidal device that is used to study plasma turbulence
at high collisionality38. Because its magnetic field lines have low pitch, its geometry approximates that ofan infinite cylinder. Flow shear is externally applied and can be controlled. The plasma is colder, with Te~10 eV and densities of only 1017 m3.

32

Hartwell, C.J., et al., Fusion Sci. and Technology 72 76 (2017)
Pandya, M.D., et al., Phys. Plasmas 22 110702 (2015)
34
Sanhar, M.K.V., et al., J. Fusion Technology 12 303 (1993)
35
Levesque, J.P., et al., Phys. Plasmas 22 056102 (2015)36
Rath, N., et al., Nucl. Fusion 53 073052 (2013)
37
Zimmerman, E.D. and S.C. Luckhardt, J. Fusion Energy 12 289 (1993)
38
Rowan, W.L. et al., Pulsed Power Plasma Science, IEEE Conf. Abstracts (2001)
33

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FIGURE G.4 KSTAR is a superconducting magnetic fusion experiment at the National Fusion
Research Institute in Daejeon, South Korea. KSTAR has a major radius of 1.8 m and superconducting
magnets energized to 450 MJ. See https://www.nfri.re.kr/eng/pageView/74.

FIGURE G.5 JT60-SA is a joint international research project, involving Japan and Europe, and underconstruction in Naka, Japan. This is an upgrade of the JT-60 experiment. SA stands for "super,advanced", and will study advanced modes of plasma operation. http://www.jt60sa.org/b/index.htm.

International Fusion Research Facilities
The current U.S. fusion research strategy has an increasing focus on U.S. participation in newer
international long-pulse experiments with superconducting magnets including EAST (China)39, KSTAR

39

Wu, S., et al., Fusion Eng. and Design 82 463 (2007)

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(Republic of Korea)40, andWendelstein 7-X(Germany)41. EAST began
operation in 2006 and
KSTAR began in 2009. The
Wendelstein 7-X stellarator
began operation in December
2015, requiring €350 million
for the stellarator device42
and additional amounts for
personnel and materials
during construction. The HL2M tokamak is underconstruction at theSouthwestern Institute ofPhysics43 as an upgrade to theexisting HL-2A44 device. HL2M will have higher plasma
heating power and magnetic
FIGURE G.6 WEST is an upgrade of the former Tore Supra
field strength to explore
superconducting tokamak located at the CEA Cadarache Center inhigher-pressure, fusionFrance. WEST achieved divertor operation with a tungsten first wall
relevant plasma. The JTin 2018. See http://west.cea.fr/en/index.php.
60SA tokamak in Japan isunder construction as aJapan-Europe project and is
expected to begin operation in 202045. Non-U.S. proposals for new facilities include the superconducting
Divertor Tokamak Test facility46 that would be built by the Italian National Agency for New
Technologies, Energy, and Sustainable Economic Development’s fusion laboratory in Frascati, Italy, andthe China Fusion Engineering Test Reactor (CFETR) under consideration as a new fusion facility todemonstrate self-sufficient tritium breeding. While researchers in the U.S. fusion community welcome
these international opportunities, presentations to the committee47 and during the first fusion community
workshop48 did not foresee how international cooperation by itself will allow the U.S. fusion researchers
to maintain a world leadership position without new facility starts within the United States.
The United States has made and continues to make important contributions to the world’s largest
currently operating fusion device, Joint European Tours (JET). This includes involvement in testing
important auxiliary systems relevant to ITER (e.g., the ITER-like Shattered Pellet Injector49), plasma
diagnostics (e.g., Faraday cups), and experimental operating scenarios (e.g., involvement in developing

40

Oh, Y.-K., et al., Fusion Eng. and Design 84 344 (2009)
Bosch, H.-S., et al., Nucl. Fusion 57 116015 (2017)42
see http://www.ipp.mpg.de/4010154/02_16
43
Liu, D., et al., Fusion Eng. and Design 96-97 298 (2015)
44
Duan, X., et al., Nucl. Fusion 57 102013 (2017)45
Shirai, H., et al., Fusion Eng. and Design 109 1701 (2016)46
Crisantia, F., et al., Nucl. Mat. and Energy 12 1330 (2017)47
See “A reinvigorated US fusion energy program,” Stewart Prager, presented to the NAS Committee for a
Strategic Plan for U.S. Burning Plasma Research (August 29, 2017)48
For example, “Perspectives on a Restructured US Fusion Energy Research Program,” T. Carter, R. Fonck, M.
Haynes, D. Maurer, D. Meade, G. Navratil, S. Prager, G. Tynan, D. Whyte, presented to the Workshop on U.S.
Magnetic Fusion Research Strategic Directions (July 24, 2017)49
Baylor, L, et al., IEEE Trans Plasma Sci, 38 419 (2010)41

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deuterium-tritium
scenarios50). Additionally,
simulation codes (e.g.,
TRANSP51) developed by
U.S. scientists have been
adopted by international
partners and are now
routinely used for scenario
modeling within the JET
program and acrossEUROfusion ITER-related
activities. Since 2016, 9 of
the 33 articles appearing in
the International Atomic
Energy Agency (IAEA)
journal Nuclear Fusion andreporting results from the
JET device involved coauthors from the UnitedStates.
For intermediatesized tokamaks (ASDEX
Upgrade, Germany; TCV,
Switzerland; MAST
FIGURE G.7 Photographs of the world’s two large superconducting
Upgrade, United Kingdom),stellarator experiments. LHD located in Japan has a major radius of 3.5
many bilateralm, and the LHD magnets are energized to 900 MJ. W7-X is located incollaborations exist between
Germany, with a major radius of 5.5 m and superconducting magnets
the United States and EU
with 640 MJ.
partners. Prominent recent
examples of U.S.
contributions include temporarily moving diagnostic devices from U.S. facilities to EU machines andjoint experiments on multiple machines to develop understanding and robust demonstration of control
schemes and new plasma scenarios. Since 2016, about 10 percent of the articles appearing in Nuclear
Fusion describing research with these medium-sized tokamaks involved co- authors from the UnitedStates.
Another important U.S. contribution to fusion research in the EU has been the participation in the
Wendelstein 7-X stellarator project. This includes the construction and operation of five large auxiliary
coils52 (installed on the outside of the device to assist in precise setting of the magnetic fields at theplasma edge) and an X-ray spectrometer, as well as the development of fluctuation diagnostics and apellet injector. This work is carried out at three U.S. national laboratories (Princeton Plasma Physics
Laboratory, Oak Ridge, and Los Alamos) and three U.S. universities (Auburn University, University
Wisconsin–Madison, and Massachusetts Institute of Technology), supporting Wendelstein 7-X withequipment that has been funded, designed, and produced in the United States and with related magnetic
field and plasma diagnosis and modeling. Since 2016, more than half of the articles appearing in Nuclear
Fusion describing research with the Wendelstein 7-X stellarator involved co-authors from the UnitedStates.
50

Budny, R., et al., Nucl. Fusion 48 075005 (2008)
Hawryluk, R., in An empirical approach to tokamak transport Physics of Plasmas Close to Thermonuclear
Conditions: Proceedings Course (Varenna, Italy, 1979) vol 1, p 19 (1980)
52
Lazerson, S., et al., Nucl. Fusion 57 046026 (2017)51

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The United States is actively playing a significant role in developing new fusion programs in
Asia. Major contributions have been made to the programs on new Asian devices since the 2004 NRC
report, notably in EAST (China), KSTAR (Republic of Korea), HL-2A (China), and J-TEXT (Japan), anda strong relationship continues with smaller spherical tokamaks (QUEST at Kyushu University, Japan;
VEST at Seoul National University, Republic of Korea; SUNIST at Tsinghua University, China). In
particular, non-inductive plasma startup and ramp-up using Co-axial Helicity Injection and Electron
Cyclotron Wave Heating and Current Drive is the focus of a multi-domestic institution collaboration withQUEST. A major focus of this international partnership has been in the use of long-pulse superconducting
devices to develop steady-state plasma scenarios.53 As an example, collaborations on EAST have madeadvances in plasma control and wall conditioning techniques developed collaboratively with and initiallydemonstrated on DIII-D. Novel computer science hardware and software infrastructure has improved data
movement, visualization, and communication and allow scientists in the United States to remotely
conduct experiments using the EAST facility54. In July 2017, the Chinese researchers using EAST
achieved a stable 101.2-second steady-state high confinement plasma, setting a world record in long-pulse
H-mode operation55. Similarly, physicists at Princeton Plasma Physics Laboratory have connected
remotely to run experiments on KSTAR.
Recent U.S.-Asia cooperation is also seen in the development of HL-2M under construction in
China and in the physics design of CFETR burning plasma facility under consideration in China, where
the United States provides design expertise and simulation codes56.
International Collaboration in U.S. ResearchInternational collaboration with U.S. researchers in burning plasma science involves all parts ofthe program, including use of experimental facilities and involvement with theory, simulation, andmodeling groups. As a metric of international involvement since 2016, of those articles appearing in the
IAEA journal Nuclear Fusion describing research with U.S. medium-sized tokamaks, one-fourth involved
co-authors from Europe and one-fourth involved co-authors from Asia. Half of all articles appearing in
Nuclear Fusion since 2016 reporting advancements in fusion simulation involved collaboratinginternational co-authors. In the area of fusion technology and engineering science, the EUROfusion Work
Package for Plasma Facing Components pays to use the PISCES-B facility at University of California,
San Diego, helping to identify first wall materials for ITER and future fusion energy systems. Currently,
no other linear plasma facility is capable of performing experiments with beryllium samples. One main
goal of this collaboration is to study the interaction between deuterium or helium plasmas with beryllium
and tungsten surfaces. Another example of a long-standing U.S.-Japan collaboration is the study of highdose irradiation effects in in an experiment on the High Flux Isotope Reactor at Oak Ridge National
Laboratory.
International participation from Asia (China and Korea in particular) in the U.S. program also has
the goal of importing established U.S. scientific knowledge such as 3D physics, tokamak scenario
development, diagnostic techniques, Heating & Current Drive technology (ECH, Klystron for helicon
CD, LHCD high field launch), advanced plasma control systems including real time control and tokamak
design and construction (e.g., HL-2M design and construction was based on knowledge gained from DIIID). Joint experiments such as those performed on EAST and DIII-D, simulation and modeling codes such
as BOUT++, technology transfer on linear plasma source for PMI study such as PISCES are also areas
where the current focus of the collaborating Asian scientists is to absorb leading scientific expertise of the
U.S.

53

Garafalo, A., et al., Nucl. Fusion 57 076037 (2017)
Schissel, D.P. et al., Nucl. Fusion 57 056032 (2017)55
See https://phys.org/news/2017-07-china-artificial-sun-world-steady-state.html
56Chen, J., et al., Plasma Phys. Cont. Fusion 59 075005 (2017)
54

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H
Schedule and Budget Implications
This appendix summarizes input examined by the committee regarding cost and schedule. These
were used by the committee in its considerations of the budget implications of its recommended strategicplan for U.S. burning plasma research.
The committee examined estimates for the cost and schedule for the two main research activities:(i) construction and operation of the ITER burning plasma experiment and (ii) a national program ofaccompanying research and development leading to the construction of a compact fusion pilot plant. It
also examined the schedule and budget implications of a decision by the United States to withdraw fromthe ITER project. Because the committee’s long-term strategic guidance covered the next several decades,
all cost and schedule estimates are necessarily notional. They were based on information andrecommendations provided to the committee by way of previous studies. Implementation of thecommittee’s strategic guidance and the development of budget estimates based on detailed facility
designs and program missions will require significant planning and effort by the fusion researchcommunity, involvement with international partners, and oversight by the U.S. Department of Energy.
Additionally, because the committee’s strategic plan involves research and technology development over
several decades, the impact of unanticipated discoveries, breakthroughs, or technical setbacks that would
influence the schedule and cost of the strategic plan could not be determined.
Costs of U.S. Participation in the ITER Project
The project cost and schedule for the U.S. contributions to ITER first plasma construction were
finalized in January 2017 and detailed in the Project Execution Plan for the U.S. Contributions to ITER
Subproject-1.1 This plan, when combined with the ITER cost and schedule information in the Secretary ofEnergy’s Report to Congress in May 2016,2 provides a basis for cost and schedule for the first main
recommendation of the committee: to remain an ITER partner as the most cost-effective way to gain
experience with a burning plasma at the scale of power plant. This schedule was developed by the U.S.
DOE Office of Science based upon the Updated Long-Term Schedule (ULTS) to first plasma. The ULTS
was approved by the ITER Council in June 2016 and independently reviewed by an ITER Council
Review Group (ICRG) in April 2016.3 As the committee notes, a measure of the reliability of ITER’s newschedule is the fact that two years after the creation of the updated long-term schedule, the projectremains on schedule for first plasma in 2025 and, since January 2016, has achieved all 33 scheduled
project milestones.
Consistent with the ULTS, the ITER Research Plan (IRP) was updated in September 2018 anddescribes the overall research activities for ITER during both the first, non-nuclear, operations andexperimentation and the second, nuclear operations phase, using deuterium and tritium (DT).4
1

DOE, Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, Office of Science,
Fusion Energy Sciences, Washington, D.C., January 2017.
2
U.S. Department of Energy, U.S. Participation in the ITER Project, Report to Congress, Washington, D.C.,
May 2016.
3
ITER Council Working Group on the Independent Review of the Updated Long-Term Schedule and Human
Resources (ICRG), (15 April 2016); available online[http://www.firefusionpower.org/ITER_ICRG_Report_2016.pdf].
4
ITER Organization, ITER Research Plan within the Staged Approach (Report ITR-18-003; 17 September
2018)

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H-1

FIGURE H.1 Research and cost schedule for U.S. participation in the ITER Project. (a) The ITER
Research Plan calls for operation in two phases: the non-nuclear hydrogen and helium phase (20262033) and the fusion nuclear phase using deuterium and tritium fuel (2036-2041). (b) The annual costs
for U.S. contributions to ITER. These costs include SP-1 and SP-2 construction and contributions tooperations and research. The FY17, FY18, and FY19 enacted funding levels for ITER are indicatedwith “◆”.

The estimated the cost of construction, operation, and maintenance for U.S. continued partnershipin the ITER Project was described in Section 4 (pp. 10-13) of the Secretary of Energy’s Report toCongress delivered in May 2016.2 Two cost and schedule estimates were presented, recognizing theuncertainty of the achievement of the first plasma milestone in 2025. If construction progress continues
according to the updated long-term schedule (ULTS), first stage construction (Subproject-1, SP-1) will becompleted in calendar year 2025. The total project cost for the U.S. will be minimum, but the peak annual
funding will be $275M. If ITER construction proceeds more slowly than scheduled, first plasma will
occur in 2028. In this case, the sum total U.S. construction cost would increase slightly (by $43M for the
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H-2

entire SP-1 construction project), but the peak annual funding would be lower, at $250M. According to
the U.S. DOE Report, a late first-plasma date of 2028 is consistent with schedule contingency while
maintaining the start of DT experiments in 2035. Construction costs include in-kind contributions ofcomponents and materials (e.g. the superconducting central solenoid, microwave and radio-frequency
transmission lines, tokamak cooling water systems) and cash contributions to the ITER Organization (IO).
Cash to the IO support essential tasks, including construction management, ITER research anddevelopment, on-site assembly and testing of all ITER components.
After completion of first-plasma construction, U.S. continues to provide in-kind and cash
contributions for the “post-first-plasma” activities, called Subproject-2 (SP-2), leading to thecommencement of burning plasma experiments with deuterium and tritium.
For the purposes of estimating the budget implications of its strategic guidance, the committee
adopted the 2028 first plasma construction profile. Including both SP-1 and SP-2 estimated costs, the U.S.
ITER funding profile requires annual funding at $250M for more than a decade.
Fig. H.1 shows both the most recent ITER research plan4 and the estimated cost and schedule ofU.S. contributions to ITER. The achievement of first plasma is a high-level technical achievement andwill represent the successful operation of the world’s largest superconducting magnet system. Nonnuclear experiments begin in the 2025-2028 time-frame, and DT fusion nuclear experiments begin in
2035. As detailed in the ITER Research Plan, important scientific and technical research will beaccomplished in both the non-nuclear and nuclear phases.
After construction is completed and operations begin, the United States share of ITER operations
increases from the 9.09% share of ITER construction to 13% of ITER operations. Using the ITER
operating cost estimated in the ICRG Report, U.S. contributions to ITER operations will beapproximately $40M. As an ITER member, the U.S. receives full access to all ITER research; however,the U.S. research program at the ITER facility will need to be funded through U.S. DOE/FES funds.
As indicated in Fig. H-1(b), present U.S. funding for ITER construction does not meet
obligations. The FY2019 enacted budget provides $132M, and the annual costs for U.S. participation in
ITER needs to increase by approximately $100M for more than a decade. Upon completion of ITER
construction beginning FY2034, U.S. ITER annual research costs are expected to be $75M.
Costs of a National Program leading to Construction of a Compact Pilot Plant
While the cost and schedule for U.S. participation in ITER are well characterized, the cost andschedule of a national program of accompanying research and technology leading to the construction of acompact fusion pilot plant are not. As a consequence, the committee’s cost and schedule estimates for thishalf of the program were based on examination of previous reports of U.S. burning plasma strategy andfusion development. Additional inputs from the fusion science and technology community, including
definition of detailed program activities and facilities, are needed to elaborate these costs and schedules.
For the purposes of cost and schedule estimates, the committee considered five broad research
categories: (i) national fusion energy science user facilities, (ii) fusion technology research, including
materials research, high-field superconducting magnets, tritium science and technologies, and fusion
nuclear science and components, (iii) discovery and innovation research in fusion science and technology,(iv) theory, modeling and predictive simulation, and (v) engineering studies and design activities for thecompact pilot plant.

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H-3

Fusion Energy Science (Annual M$ US)

Notional Budget for U.S. StrategicPlanfor BurningPlasmaResearch

ITERConstructionandOperation

U.S. FusionResearchFacilities(DIII-DandNSTX-U)

SustainedHPDFacility(Operation)

SustainedHigh-Power DensityFacility(DesignandConstruction)

Compact Pilot Plant(DesigntoPhase1)

FusionTechnology(MaterialsResearch, Magnets, Tritium, FusionNuclear Science)

DiscoveryFusionScienceandTechnology
Theory, Modeling, andPredictiveSimulation

FIGURE H.2 Notional budget, in FY2018 dollars, implied by the committee’s strategic guidance
for a national program of burning plasma research. The figure shows, in addition to the U.S. ITER
costs, the evolution of five broad research categories: (i) national fusion user facilities, (ii) fusion
technology research, (iii) discovery research in fusion science and technology, (iv) theory, modelingand predictive simulation, and (v) engineering studies and design activities for the compact pilot
plant. The total U.S. DOE/FES funding levels for FY17, FY18, and FY19 are indicated with “◆”.

Fig. H-2 illustrates the committee’s notional cost and schedule implications for these fiveresearch categories along with the cost and schedule for U.S. participation in the ITER project. The graphshows an aggregated funding, and is provided to illustrate notional allocations. Any actual funding profile
would be allocated after vetting, particularly with respect to the phasing in and out of the different facility
contributions.
The DIII-D experiment (located at General Atomics, San Diego) and the NSTX-U experiment(located at the Princeton Plasma Physics Laboratory) are the two major research facilities presently
supported by the U.S. DOE/FES as national user facilities. During the next decade, these facilities will be
used to answer key scientific questions and will also develop promising operating scenarios in preparation
for ITER experiments. Additionally, the committee’s strategic plan calls for these facilities to play anessential role beyond ITER, including optimizing the configurations that will demonstrate the science andtechnology for sustained operation at high-power density and informing the design for a next-stepresearch facility. As explained in Ch. 5, the committee’s strategic guidance necessitates an evolution ofmajor research facilities. The operation of the DIII-D and NSTX-U facilities will end, near completion of
ITER construction, and allowing construction of a new national research facility to begin.
Three recent FESAC Reports provided cost estimates of facilities and programs that wereconsidered by the committee. These are:

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





Report of the FESAC Subcommittee on the Prioritization of Proposed Scientific User Facilities(March 2013) available online.5 This report reported costing estimates for four facilities andupgrades: (i) a fusion materials irradiation facility, (ii) a fusion nuclear science facility, (iii) a
quasi-symmetric stellarator facility, and (iv) upgrade to the DIII-D national fusion facility.
Report of the FESAC Subcommittee on Strategic Planning: Priorities Assessment and Budget
Scenarios (October 2014) available online.6 This report describes a budget scenario having“modest growth” that results in additional funding, approximately $100M/annually, to non-ITER
research that allows the start of a fusion nuclear science initiative and allows construction of afusion neutron irradiation facility in collaboration with U.S. DOE/BES and a linear divertor
simulator for plasma-materials interaction studies.
Report of the FESAC Subcommittee on Transformative Enabling Capabilities Toward Fusion
Energy (February 2018) available online.7 This report describes several “revolutionary” ideas thatwould dramatically increase the rate of progress towards fusion power through increased fusion
performance, device simplification, reduced cost or time to delivery, or improved reliability
and/or safety. The committee’s consideration for the budgetary implications of the strategic planassume continued progress in the innovative technologies that lower the cost and fully enablefusion electricity.

In addition to the above mentioned FESAC Reports, the committee examined the budget
estimates provided in the 2003 Report of the FESAC Subcommittee for a Plan for the Development of
Fusion Energy,8 the 2016 U.S. Magnet Development Program Plan9 initiated by the DOE Office of
Science and HEPAP, and the 1987 Report of the Office of Technology Assessment (OTA) Starpower:
The U.S. and the International Quest for Fusion Energy,10 which reported the cost of the Large Coil Task
(p. 159) and serves as a model for similar superconducting research for new high-field superconducting
magnets as discussed in Ch. 4.
As indicated in Fig. H-2, besides ITER construction and operation, the U.S. DOE needs tosignificantly expand the U.S. research program in fusion nuclear technology, advanced materials, safety,
and tritium and blanket technologies to fully enable fusion energy. The committee estimates the U.S.
fusion energy science research program will require an additional $100M/annually for this expanded
fusion technology research. This increase is consistent with (i) the 2014 FESAC “modest growth”
strategy that supports the start of a fusion nuclear science initiative including research on plasma-material
studies with a linear divertor simulator, design and construction of a new materials neutron-irradiation
facility that leverages existing neutron spallation source, and increased research on blanket technologies
and tritium science, and (ii) the fusion materials testing program of the 2003 FESAC fusion development
5

Report of the FESAC Subcommittee on the Prioritization of Proposed Scientific User Facilities (March2013); available online athttps://science.energy.gov/~/media/fes/fesac/pdf/2013/FESAC_Facilities_Report_Final.pdf
6Report of the FESAC Subcommittee on Strategic Planning: Priorities Assessment and Budget Scenarios(October 2014); available online athttps://science.energy.gov/~/media/fes/fesac/pdf/2014/October/FESAC_strategic_planning_rept_dec14.pdf
7Report of the FESAC Subcommittee on Transformative Enabling Capabilities Toward Fusion Energy(February 2018); available online athttps://science.energy.gov/~/media/fes/fesac/pdf/2018/TEC_Report_15Feb2018.pdf
8Report of the FESAC Fusion Development Panel (March 2003), A Plan for the Development of Fusion
Energy, DOE/SC-0074; also available as Goldston, R., Abdou, M., Baker, C. et al. Journal of Fusion Energy (2002)
21: 61. https://doi.org/10.1023/A:1025038002187 .
9
S. A. Gourlay, S. O. Prestemon, A. V. Zlobin, L. Cooley, D. Larbalestier, The U.S. magnet development
program plan, Lawrence Berkeley Nat. Lab., Jun. 2016; available online http://www2.lbl.gov/LBLPrograms/atap/MagnetDevelopmentProgramPlan.pdf
10
U.S. Congress, Office of Technology Assessment, Starpower: The U.S. and the International Quest for
Fusion Energy, OTA-E-338 (Washington, DC: U.S. Government Printing Office, October 1987).

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plan. The committee’s budget guidance emphasizes innovative technology research, careful-planning, andstaged, cost-effective facility steps. A fusion component testing facility (sometimes also called a fusion
nuclear science facility) is among the costliest facilities discussed in these previous reports. However, as
described in the recent FESAC Transformative Enabling Capabilities Toward Fusion Energy,
innovations are expected to lower cost of fusion technology development and testing. Additionally,schedule planning will occur as part of a staged research plan in the compact fusion pilot plant so that
integrated testing of fusion blankets can be carried out as part of national user facility licensed for tritium
operation.
An important addition to an expanded fusion technology program that was not previously
described is the testing of large-bore, high-field HTS magnets for fusion. Ch. 4 presents the committee’s
recommendation to demonstrate the ability to achieve high magnetic fields using high-critical temperature
superconductors (HTS). A reference for this program is the Large Coil Task (LCT) which required about$94M (current dollars) with each superconducting test coil costing between $28M and $35M to construct.
As was also described in Ch. 4, the expanded fusion technology research program would include
advanced manufacturing, engineering systems studies, and research to enable advancements in heating,control, and diagnostics needed for the compact fusion pilot plant.
Fig. H-2 indicates one evolution for the major research facilities in the U.S. (i.e. the DIII-D and
NSTX-U facilities). The operations of these facilities end prior to 2030, and construction of a newnational research facility will begin to demonstrate the science and engineering needed to sustain amagnetically confined plasma having the high-confinement property and compatible plasma exhaustsystem that are needed for a compact fusion pilot-plant. Provided the U.S. remains an ITER partner, theresearch goal of this new national facility would be to address the divertor and first-wall issues for acompact pilot plant. It would a major, world-class research facility to resolve critical needs, but it would
not be a fusion nuclear facility and would not involve those burning plasma science questions that require
injection of tritium. Fig. H-2 indicates approximately $1.5B US for the design and construction of thisfacility. This construction cost was estimated in the 2003 Plan for the Development of Fusion Energy (p.
37) as $550M, comparable to the construction costs for the German superconducting stellarator
experiment (Wendelstein 7-X)11 and to the Italian-proposed Divertor Tokamak Test Facility (DTT).12
Proposals provided to the committee from the U.S. fusion community for such a new research facility also
considered approaches having reduced costs through the upgrade of some existing research capabilities
from the two major fusion user facilities in the United States.13
Engineering systems studies for the compact fusion pilot plant would begin immediately in the
U.S. strategic plan. These studies would identify science and technology areas for additional research andguide program decision. As shown in Fig. H.2, design activities for the compact fusion pilot plant would
guide essential research for the next two decades and help coordinate progress in burning plasma science,fusion technologies, and the integrated science encompassing the divertor-pedestal-core needed forsustained high-power density magnetic confinement fusion.
The annual funding to implement the committee’s recommendation, including both continued
participation in ITER and the start of a national research program for a compact pilot-plant, requires
nearly $200M higher than currently enacted funding levels. About half of this additional amount isrequired to meet ITER commitments and the other half is needed to launch the science and technology
supporting the research leading to a compact fusion pilot-plant. The budget profile after completion of
11

See “Wendelstein 7-X fusion device produces its first hydrogen plasma: Federal Chancellor switches plasma
on / Start of scientific experimentation,” IPP Max-Planck-Institut für Plasmaphysik (February 3, 2016); available
online at https://www.ipp.mpg.de/4010154/02_16
12
Divertor Tokamak Test facility - Project Proposal, Italian National Agency for New Technologies, ENEA
(ISBN: 978-88-8286-318-0; July 2015, ENEA Frascati Research Center, Italy); available at
http://www.enea.it/it/pubblicazioni/pdf-volumi/V2015_TokamakProposal.pdf
13
See, for example, Wade, M., (March 2018) “A U.S. Strategic Plan for Timely Fusion Energy Development,”
White Paper submitted to the Committee and Buttery, R.J., et al., (March 2018) “Development of a Steady State
Fusion Core – The Advanced Tokamak Path,” White Paper submitted to the Committee.

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ITER construction is uncertain and would need an evaluation based on progress in the national research
program.
Fig. H.2 indicates the annual funding for the U.S. DOE/FES program for FY2017, FY2018, andFY2019. The FY2019 U.S. DOE/FES total funding is $564M, which is about $130M less than the annual
funding estimates in Fig. H.2. However, the present U.S. DOE/FES program includes plasma science
research, called discovery plasma science, totaling $84M in FY2019. This funding provides important
support for non-fusion related research, including high energy density laboratory plasma physics, lowtemperature plasma science, and fundamental plasma science. The committee’s strategic guidance
includes funding for discovery fusion science and technology and fusion theory, modeling, and predictive
simulation, but the committee did not consider the funding priorities for the broad discipline of plasma
science that extends beyond establishment of the science and technology needed to develop an
economical source of fusion power.
Cost and Schedule Implications of a U.S. Decision to Withdraw from the ITER ProjectAs explained by the Secretary of Energy (p. ii of Ref. 2), “ITER remains the best candidate today
to demonstrate sustained burning plasma, which is a necessary precursor to demonstrating fusion energy
power.” Because ITER is a major part of the U.S. fusion research program, a decision by the U.S. towithdraw from the ITER project, would significantly disrupt the national effort, isolate U.S. researchers
from the international effort, and eliminate the benefit of sharing the cost of producing a burning plasma
at the power plant scale. Without ITER participation, the United States would need to design, license, andconstruct an alternative means to gain experience creating and controlling an energy-producing burning
plasma. Experience controlling and sustaining a burning plasma is needed as part of the continued U.S.
strategy to design and construct a compact fusion pilot-plant in the long-term.
The committee was unable to estimate the cost and schedule of a research program comparable tothat shown in Fig. H.2 for the scenario without ITER participation. Recent FESAC reports have notconsidered this scenario, and no details were provided to the committee from the research community.
The potential costs associated with a decision to withdraw from the ITER partnership was
described by the Secretary of Energy’s Report to Congress (p. 13 of Ref. 2). The Joint Implementation
Agreement (JIA) for ITER requires the U.S. to continue to deliver or pay the remaining share of ITER
construction costs, estimated to be about $2B. Additional project termination costs were estimated to total$66M.
As discussed in Ch. 5, in order to establish the science and technology basis for the compact
fusion pilot plant, the previously-discussed high-power density experiment to establish the physics basis
for continuous sustainment of high-power density burning plasma would need to be capable of operation
with tritium fuel and designed for the burning plasma studies now envisioned for ITER. The construction
and operation of this experiment would be expensive for the U.S. to undertake alone, but it would becritical for directly addressing the physics of a strongly-coupled burning plasma and reducing the key
barriers for low-cost fusion energy development. For example, a fusion nuclear research facility, like the
FSNF, was examined in the 2013 FESAC Report on Prioritization of Proposed Scientific User Facilities5(p. 13). Estimated total project cost for the FSNF is multi-billion dollars, and significant scientific andengineering challenges needed to be resolved before initiating construction. For this reason, the design
and planning for a fusion nuclear facility to serve as an U.S. alternate to ITER would need to begin
immediately. Considering the time that was required to design the ITER experiment and to develop preconceptual designs for the FNSF, the committee concludes the achievement of electricity production fromfusion in the United States would be delayed significantly and the sum of both ITER termination
obligations and the construction of a larger fusion research facility to study the physics and gain
experience with the technology needed to control and sustain a burning plasma would be larger than the
research program that benefits from the ITER partnership.

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IInterim Report of the Committee on a Strategic Plan for U.S. Burning Plasma Research (National
Academies of Sciences, Engineering, and Medicine, The National Academies Press, Washington, D.C.,
2018) is reprinted here in its entirety. Note that the reprinted report’s page numbers reflect the paginationthat applies for inclusion in the current report, rather than the pages numbers of the original report.

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REPRINTED INTERIM REPORTINTERIM REPORT OF THE
COMMITTEE ON A STRATEGIC PLAN
FOR U.S. BURNING PLASMA RESEARCH

Committee on a Strategic Plan for U.S. Burning Plasma Research
Board on Physics and Astronomy
Division on Engineering and Physical Sciences

A Consensus Study Report of

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REPRINTED INTERIM REPORTTHE NATIONAL ACADEMIES PRESS 500 Fifth Street, NW Washington, DC 20001
This activity was supported by the Contract No. DE-SC0013488 from the Department of Energy. Any opinions,findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any
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Suggested Citation: National Academies of Sciences, Engineering, and Medicine. 2018. Interim Report of theCommittee on a Strategic Plan for U.S. Burning Plasma Research. Washington, DC: The National Academies Press.
doi: https://doi.org/10.17226/24971.

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REPRINTED INTERIM REPORTThe National Academy of Sciences was established in 1863 by an Act of Congress, signed byPresident Lincoln, as a private, nongovernmental institution to advise the nation on issues
related to science and technology. Members are elected by their peers for outstanding
contributions to research. Dr. Marcia McNutt is president.
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Consensus Study Reports published by the National Academies of Sciences, Engineering, andMedicine document the evidence-based consensus on the study’s statement of task by anauthoring committee of experts. Reports typically include findings, conclusions, andrecommendations based on information gathered by the committee and the committee’s
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REPRINTED INTERIM REPORTCOMMITTEE ON A STRATEGIC PLAN FOR U.S. BURNING PLASMA RESEARCHMICHAEL MAUEL, Columbia University, Co-ChairMELVYN SHOCHET, NAS,1 University of Chicago, Co-Chair
CHRISTINA BACK, General Atomics
RICCARDO BETTI, University of Rochester
IAN CHAPMAN, UK Atomic Energy Authority
CARY FOREST, University of Wisconsin, Madison
T. KENNETH FOWLER, University of California, Berkeley
JEFFREY FREIDBERG, Massachusetts Institute of Technology
RONALD GILGENBACH, University of Michigan
WILLIAM HEIDBRINK, University of California, Irvine
MARK HERRMANN, Lawrence Livermore National Laboratory
FRANK JENKO, University of California, Los Angeles
STANLEY KAYE, Princeton University
MITSURU KIKUCHI, National Institutes for Quantum and Radiological Science and Technology
SUSANA REYES, Lawrence Berkeley National Laboratory
C. PAUL ROBINSON, Advanced Reactor Concepts, LLC
PHILIP SNYDER, General Atomics
AMY WENDT, University of Wisconsin, Madison
BRIAN WIRTH, University of Tennessee, Knoxville
Staff
JAMES C. LANCASTER, Director
DAVID LANG, Senior Program Officer, Study Director
ANDREA PETERSON, Program Officer (until August 2017)
CHRISTOPHER J. JONES, Program Officer
NEERAJ GORKHALY, Associate Program Officer
LINDA WALKER, Program Coordinator
HENRY KO, Research Associate
BETH DOLAN, Financial Associate

1

Member, National Academy of Sciences.

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REPRINTED INTERIM REPORTBOARD ON PHYSICS AND ASTRONOMYBARBARA V. JACAK, NAS,1 Lawrence Berkeley National Laboratory, Chair
ABRAHAM LOEB, Harvard University, Vice Chair
FRANCIS J. DISALVO, NAS, Cornell University
TODD DITMIRE, University of Texas, Austin
NATHANIEL J. FISCH, Princeton University
DANIEL FISHER, NAS, Stanford University
WENDY FREEDMAN, NAS, University of Chicago
GERALD GABRIELSE, NAS, Harvard University
JACQUELINE N. HEWITT, Massachusetts Institute of Technology
WENDELL T. HILL III, University of Maryland
ALAN J. HURD, Los Alamos National Laboratory
BARBARA JONES, IBM Almaden Research Center
HERBERT LEVINE, NAS, Rice University
LYMAN A. PAGE, JR., NAS, Princeton University
STEVEN M. RITZ, University of California Santa Cruz
Staff
JAMES C. LANCASTER, Director
DAVID B. LANG, Senior Program Officer
CHRISTOPHER J. JONES, Program Officer
NEERAJ GORKHALY, Associate Program Officer
LINDA WALKER, Program Coordinator
HENRY KO, Research Associate
BETH DOLAN, Financial Associate

1

Member, National Academy of Sciences.

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REPRINTED INTERIM REPORT

Preface
In January 2003, President George W. Bush announced that the United States would begin negotiations tojoin the International Thermonuclear Experimental Reactor (ITER) project and noted that “if successful, ITER
would create the first fusion device capable of producing thermal energy comparable to the output of a power plant,
making commercially viable fusion power available as soon as 2050.”1 In 2007, the United States became an ITER
member after signing a binding international agreement with China, the European Union, India, Japan, the Republicof Korea, and Russia. The United States and the other ITER members are now constructing ITER with the aim to
demonstrate that magnetically confined plasmas can produce more fusion power than the power needed to sustain
the plasma. This is a critical step towards producing and delivering electricity from fusion energy.
Since the international establishment of the ITER project, ITER’s construction schedule has slipped and
ITER’s costs have increased significantly, leading to questions about whether the United States should continue its
commitment to participate in ITER. These concerns resulted in a directive from Congress, appearing in the 2016
Consolidated Appropriations Act, that the Secretary of the Department of Energy (DOE) report to Congress on
United States participation in the ITER project, including budget projections, project schedule, project management,
and foreign policy implementations.
The Secretary’s report was delivered to Congress in May 2016 and recommended that the United Statesremain a partner in the ITER project through fiscal year (FY) 2018. The report acknowledged the significant
construction progress made at ITER and the substantial improvements of ITER project management but also notedthat significant technical and management risks remain. It remains to be seen whether the United States willcontinue its ITER membership beyond FY2018 as well as whether project performance will be sustained and thelarger costs needed for U.S. obligations for ITER construction can be accommodated in future budgets for the DOE
Office of Science. The Secretary’s report stated that, prior to the FY2019 budget submittal, “the U.S. re-evaluate its
participation in the ITER project to assess if it remains in our best interests to continue our participation.”2
In addition to outlining various oversight and management reviews to ensure continued improvement in
ITER project performance, the Secretary’s report requested advice from the National Academies “to perform a studyof how to best advance the fusion energy sciences in the United States, given the developments in the field since the
National Research Council study in 2004, the specific international investments in fusion science and technology,
and the priorities for the next ten years developed by the community and the Office of Fusion Energy Sciences(FES) that were recently reported to Congress. This study will address the scientific justification and needs forstrengthening the foundations for realizing fusion energy given a potential choice of U.S. participation or not in the
ITER project, and will develop future scenarios in either case.”3
In response to this request, the National Academies of Sciences, Engineering, and Medicine established theCommittee on a Strategic Plan for U.S. Burning Plasma Research. The committee’s statement of task is given in
Appendix B.
The statement of task requests the preparation of this interim report prior to submission of strategic
guidance that will be developed later and presented in a final report. Although the committee has not yet completed
its work guiding the long-term fusion research strategies in both scenarios, in which the United States is, or is not, amember in ITER, the committee has completed its assessment of the current status of U.S. fusion research and of theimportance of burning plasma research to the development of fusion energy as well as to plasma science and otherscience and engineering disciplines.
1
George W. Bush: Fact Sheet: ITER, January 30, 2003. Available online by G. Peters and J.T. Woolley, The
American Presidency Project, http://www.presidency.ucsb.edu1/ws/?pid=80124.
2
U.S. Department of Energy, U.S. Participation in the ITER Project, Report to Congress, Washington, D.C.,
May 2016, p. ii.
3
Ibid., p. 16.

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REPRINTED INTERIM REPORTThis interim report is based on the information the committee received in its first two meetings (seeAppendix C), from review of a large number of prior reports and studies, which includes DOE’s Project Execution
Plan for U.S. Contributions to ITER Subproject-1 released in January 2017 (see Appendix D), and from the first of
two community workshops on strategic directions for U.S. magnetic fusion research held at the University of
Wisconsin, Madison, from July 24 through July 28, 2017.
Having completed its assessment of the status and importance of U.S. burning plasma research, thecommittee anticipates that the final report will present strategies that incorporate continued progress toward aburning plasma experiment and a focus on innovation. The committee will receive input from the second community
workshop on strategic directions for U.S. magnetic fusion research to be held at the University of Texas, Austin,
December 11-15, 2017, and several site visits. Additionally, a subcommittee of the Fusion Energy Sciences
Advisory Committee to the DOE Office of Science is expected to complete its report shortly, identifying the mostpromising transformative enabling capabilities for the United States to pursue that could promote efficient advancetoward fusion energy.
To the extent possible, the committee’s final report will include considerations of the health of fusion
research sectors within the United States, the role of international collaboration in the pursuit of national fusionenergy goals, the capability and prospects of private-sector ventures to advance fusion energy concepts andtechnologies, the impact of science and technology innovations, and the design of research strategies that may
shorten the time and reduce the cost required to develop commercial fusion energy.

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Acknowledgment of Reviewers
This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse
perspectives and technical expertise. The purpose of this independent review is to provide candid and criticalcomments that will assist the National Academies of Sciences, Engineering, and Medicine in making each publishedreport as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence,and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect
the integrity of the deliberative process.
We thank the following individuals for their review of this report:
Roger D. Blandford, NAS,1 Stanford University,
Richard Buttery, General Atomics,
James D. Callen, NAE,2 University of Wisconsin, Madison (retired),
Steve Cowley, Corpus Christi College,
Robert Iotti, ARC Nuclear,
Johnathan E. Menard, Princeton University,
Ann White, Massachusetts Institute of Technology, andSteven J. Zinkle, NAE, University of Tennessee, Knoxville.
Although the reviewers listed above provided many constructive comments and suggestions, they were notasked to endorse the conclusions or recommendations of this report nor did they see the final draft before its release.
The review of this report was overseen by Marcia J. Rieke, NAS, University of Arizona, and William Dorland,
University of Maryland, College Park. They were responsible for making certain that an independent examination ofthis report was carried out in accordance with the standards of the National Academies and that all review comments
were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the
National Academies.

1
2

Member, National Academy of Sciences.
Member, National Academy of Engineering.

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REPRINTED INTERIM REPORTContents

SUMMARY

1

1

BACKGROUND

6

2

THE COMMITTEE’S INFORMATION-GATHERING PROCESS

11

3

IMPORTANCE OF BURNING PLASMA RESEARCH

13

4STATUS OF U.S. RESEARCH THAT SUPPORTS BURNING PLASMA SCIENCE

20

5ASSESSMENTS

30

6TOWARD COMPLETION OF THE FINAL REPORT35

APPENDIXESA
BCDWhat Is Magnetic Fusion?
Statement of Task
Agendas from Committee Meetings
Previous Studies of Magnetic Fusion Energy and Strategies for Fusion
Energy Development Consulted by the Committee

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39
42
44
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Summary
In this interim report, the Committee on a Strategic Plan for U.S. Burning Plasma Research makes thefollowing assessments of the importance of burning plasma research to the development of fusion energy and of thecurrent status of U.S. burning plasma research, including current and planned participation in international activities.
Assessment 1: Burning plasma research is essential to the development of magnetic fusion energy andcontributes to advancements in plasma science, materials science, and the nation’s industrial capacity todeliver high-technology components.
All efforts to make fusion energy require a burning plasma—an ionized gas like the Sun and stars that isheated by fusion reactions. Burning plasma research begins with understanding, measuring, and predicting thecomplex physical processes of the plasma and of the energetic particles moving within the plasma created by fusion
reactions. Next, burning plasma research includes the high-technology tools used to control, confine, and heat theplasma to very high temperature and pressure. Finally, burning plasma research embodies the applied andengineering sciences necessary to design reliable structures that surround the plasma and convert fusion energy into
useful heat and power. Burning plasma research is interdisciplinary and results in technological and scientificachievements that touch many aspects of everyday life and lead to new insights in related fields such as optics, fluid
mechanics, and astrophysics.
Although significant fusion power has been generated for short periods in the laboratory (4 MW for 4 s andup to 16 MW for shorter periods) and some processes expected in a burning plasma have been studied at thetemperatures and pressures required for fusion energy, a burning plasma, which is heated predominately by fusion
reactions, has never been created. This requires construction of a burning plasma experiment such as theInternational Thermonuclear Experimental Reactor (ITER). A burning plasma experiment will allow integrated
investigation of the burning plasma with the advanced technology magnetic fusion schemes require. Because of its
large size and complexity, constructing a burning plasma experiment leads to advancements in industrial capability,
such as for large superconducting magnets, vacuum technologies, complex cryogenic systems, ultra-precise
construction, and robotic systems to handle materials.
Assessment 2: The U.S. fusion energy science program has made leading advances in burning plasma sciencethat have substantially improved our confidence that a burning plasma experiment such as ITER will succeedin achieving its scientific mission.
Experiments conducted using research facilities in the United States have been highly productive. New
ideas to control and sustain burning plasma have been discovered, and theoretical and computational models
developed in the United States have substantially improved the ability to control plasma stability, predict plasma
confinement, and enhance fusion energy performance. The understanding of burning plasma science has advanced
significantly, including such critical topics as the transport of heat and particles by multi-scale turbulence, thebehavior of energetic particles produced by fusion reactions, and the physics of the narrow insulating layer at theplasma edge (or “pedestal”). In addition, new techniques have been developed to avoid and mitigate transient events,
which can erode plasma facing materials. Scenarios of burning plasma operation that are expected to simultaneously
satisfy the requirements for stability, confinement, fuel purity, and compatibility with plasma facing components
have been developed experimentally and explored with computational models. These scenarios further increase
confidence in the burning plasma performance that can be achieved in ITER. While important avenues for further
exploration remain, current understanding increases confidence that ITER will achieve its scientific mission. The
widely recognized importance of U.S. research contributions to the field also supports the expectation that, if the

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United States continues to participate in ITER, scientists within the United States will make leading contributions tothe study of fusion energy at the power plant scale.
Assessment 3: Construction and operation of a burning plasma experiment is a critical, but not sufficient,
next step toward the realization of commercial fusion energy. In addition to a burning plasma experiment,
further research is needed to improve and fully enable the fusion power system.
A burning plasma experiment will examine for the first time many of the interconnected scientific andtechnology issues that must be addressed to produce magnetic fusion energy. Among these are the experimental
validation of theoretical predictions related to plasma stability, plasma heating, transport of plasma heat andparticles, alpha particle physics from fusion reactions, and disruption avoidance for tokamaks in substantially
unexplored regimes of magnetic confinement. Equally important are gains in fusion engineering science including
large-scale superconducting magnet technology, progress toward understanding fusion blanket science, tritium
science and management, remote handling of materials and components, and large-scale systems integration. As aburning plasma experiment, ITER is a critical step along the path to advance the science and technology of a fusion
power source.
Still, ITER is a fusion research facility and a long way from being a system for commercial power. In acommercial system, economics requires the thermal power to increase about seven-fold. Continuous operation
requires efficient coupling of radio waves into the plasma to sustain the plasma current. Challenging plasma-wall
problems need inventive solutions in order to safely handle the flux of energetic neutrons on the inner wall and theescaping heat from the plasma that is directed onto the plates of a protective divertor. The self-consistent production
and safe handling of tritium will not be fully addressed in ITER but must be solved for commercial fusion power.
Lastly, the expected gains in engineering and economics that might accrue from technology and materials
innovations, like the newly developed rare-earth, high-temperature superconductors, need to be investigated;
however, these innovations will only impact fusion facilities built beyond ITER. The overall picture is that a burning
plasma experiment, such as ITER, will lead to major gains along the path to fusion energy while other fusion energy
experiments will need to address remaining science and technology challenges and demonstrate innovative solutions
that lead to a reduced size, lower cost, full-scale power source.
Assessment 4: Although our international partners have national strategic plans leading to a fusion energy
demonstration device, the United States does not.
Since the National Research Council’s (NRC’s) study in 2004,1 strategic plans leading to a fusion energy
demonstration have been developed by many of our international partners, all with high-level governmental support
including, in some cases, accompanying legislation. These strategies all recognize that the burning plasma regime
promised by ITER is the most expedient way to demonstrate controlled fusion on commercial scale and,
importantly, elucidate the accompanying research and technology programs needed to progress beyond ITER to acommercial fusion reactor. Such strategic planning guides national research and innovation programs, helps toengage industrial partners, and sets the national priorities of our partners, enabling them to develop key areas ofunique expertise. The absence of such a nationally endorsed strategic plan for delivery of fusion energy in the
United States inhibits the long-term planning of all participants in the fusion endeavor in the United States, fromuniversities, to national laboratories, to industrial partners. Without a long-term plan, the United States risks being
overtaken as our partners advance the science and technology required to deliver fusion energy. Conversely, theadoption of such a plan has the potential to support strategic funding decisions and priorities within the national
program and help foster innovation towards commercially viable fusion reactor designs.
Assessment 5: Recent closures of domestic experimental facilities without new starts, as well as a reduction offusion technology efforts, threaten the health of the field in the United States.
As reported by the 2004 NRC report,2 many of the scientific and technical issues of importance to the longrange development of fusion are best addressed by research facilities having size and complexity much smaller thanthat needed for a burning plasma experiment. A long-term strategy for fusion energy benefits from a domestic effort
1

National Research Council (NRC), Burning Plasma: Bringing a Star to Earth, The National Academies Press,
Washington, D.C., 2004.
2
NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.

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in parallel with the ITER project focused on developing the scientific base for promising fusion reactor concepts andtechnologies.
However, during the past decade, various programmatic decisions have closed domestic experimental
facilities without opportunities for new starts and without compensating programs internationally. In 2005, thebudget for U.S. fusion technology efforts was sharply reduced. In 2013, the Department of Energy’s (DOE’s) Officeof Fusion Energy Sciences implemented an overall reduction in the domestic program while making only a modest
increase in funding for scientific collaborations on non-U.S. experimental facilities. Currently, only one mid-scalefusion experiment is operating in the United States. Mid-scale experimental facilities can attract talent to the field,
provide broad scientific and engineering opportunities, and test innovations that could improve the fusion energy
concept and strengthen U.S. expertise in fusion science and technology.
Assessment 6: Any strategy to develop magnetic fusion energy requires study of a burning plasma. The only
existing project to create a burning plasma at the scale of a power plant is ITER, which is a major componentof the U.S. fusion energy program. As an ITER partner, the United States benefits from the long-recognizedvalue of international cooperation to combine the scientific and engineering expertise, industrial capacity,and financial resources necessary for such an inherently large project. A decision by the United States towithdraw from the ITER project as the primary experimental burning plasma component within a balanced
long-term strategic plan for fusion energy could isolate U.S. fusion scientists from the international effort andwould require the United States to develop a new approach to study a burning plasma.
Past studies of magnetic fusion energy research recommended U.S. entrance into international partnerships
as the most cost-effective approach to undertake large fusion energy experiments. These studies include
Cooperation and Competition on the Path to Fusion Energy,3 Pacing the U.S. Magnetic Fusion Program,4 the 1995
President’s Committee of Advisors on Science and Technology (PCAST) panel report The U.S. Program of Fusion
Research and Development,5 and Realizing the Promise of Fusion Energy.6 After considering various options for aburning plasma experiment, the 2004 NRC report7 recommended that the United States should participate in ITER.
But, if the United States were not to participate in ITER, that committee also recommended the pursuit ofinternational partnership in an alternate burning plasma experiment. A burning plasma experiment at the scale of apower plant is necessarily a large facility and integrates multiple advanced technologies. At the present time, nocountry has the combination of scientific and engineering expertise, industrial capacity, and long-term national
commitment to undertake this critical task alone.
While previous studies concluded that fusion energy research substantially benefits from international
cooperation, they also described a potential for failure if international partners were unable to meet theircommitments. The 2009 NRC report A Review of the DOE Plan for U.S. Fusion Community Participation in the
ITER Program recommended that steps should be taken to “seek greater U.S. funding stability for the international
ITER project to ensure that the United States remains able to influence the developing ITER research program, tocapitalize on research at ITER to help achieve U.S. fusion energy goals, to participate in obtaining importantscientific results on burning plasmas from ITER, and to be an effective participant in and beneficiary of futureinternational scientific collaborations.” 8
The committee has reviewed the recommendations from these past studies in the context of the existing
ITER partnership, the assessments of U.S. burning plasma research listed above, and the benefits international
partnership brings to large multi-year endeavors at the frontier. Based on this review, the committee concludes that
the United States benefits from partnership in ITER as the primary experimental burning plasma component within
its own long-term strategic plan for fusion energy. On the other hand, a decision by the United States to withdraw
from the ITER project would require a new approach to study a burning plasma. Because there is currently no
3

NRC, Cooperation and Competition on the Path to Fusion Energy: A Report, National Academy Press,
Washington, D.C., 1984.
4
NRC, Pacing the U.S. Magnetic Fusion Program, National Academy Press, Washington, D.C., 1989.
5
President’s Committee of Advisors on Science and Technology, The U.S. Program of Fusion Research andDevelopment, Washington, D.C., July 11, 1995.
6
U.S. Department of Energy, Realizing the Promise of Fusion Energy: Final Report of the Task Force on
Fusion Energy, Secretary of Energy Advisory Board, Washington, D.C., August 9, 1999.
7
NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.
8
NRC, A Review of the DOE Plan for U.S. Fusion Community Participation in the ITER Program, The
National Academies Press, Washington, D.C., 2009, pp. 2-3.

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mature burning plasma experiment as an alternative to ITER, the design, construction, and licensing of such analternative to ITER would require significant development by the U.S. program, as well as a new approach to avoid
isolation from the international fusion energy research effort.
The committee’s final report will provide greater detail and analysis of the options for a long-term strategicplan for a national program of burning plasma science and technology research, including developing various
supporting capabilities and participating in international activities. Strategic guidance for scenarios where the UnitedStates both is and is not a participant in ITER will be described.
Work for the final report is at an early stage. Nevertheless, based on the input received by the committee
and the committee’s assessments, if the United States seeks to continue its pursuit for abundant fusion power, thedevelopment of a national strategic plan for fusion energy that spans several decades is necessary. Therefore, thecommittee makes the following final assessment that will guide the strategies for both scenarios in the final report.
Assessment 7: If the United States wishes to maintain scientific and technical leadership in this field, thecommittee concludes that the United States needs to develop its own long-term strategic plan for fusionenergy.
In the development of the final report, the committee views the following elements as important to its
guidance on a long-term strategic plan:

Continued progress towards the construction and operation of a burning plasma experiment leading to
the study of burning plasma,
Research beyond what is done in a burning plasma experiment to improve and fully enable commercial
fusion power,
Innovation in fusion science and technology targeted to improve the fusion power system as acommercial energy source, andA mission for fusion energy research that engages the participation of universities, national
laboratories, and industry in the realization of commercial fusion power for the nation.

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1
Background
On January 30, 2003, just 6 weeks after the release of the interim report of the National Research Council’s(NRC’s) Burning Plasma Assessment Committee,1 the focus and priority of the U.S. fusion energy sciences programchanged. President George W. Bush announced “that the United States will join an ambitious international research
project to harness the promise of fusion energy, the same form of energy that powers the Sun.”2 The President’s
announcement described the International Thermonuclear Experimental Reactor (ITER) as “the largest and mosttechnologically sophisticated fusion experiment in the world.” The President also acknowledged the NRC’s
recommendation for U.S. participation in ITER and further explained, “This step is critical to the development offusion as a viable energy source. Recent scientific developments have advanced knowledge of this field to the pointthat scientists now believe ITER can demonstrate the feasibility of this technology as part of an ongoing effort todevelop a practical energy-generating device. If successful, ITER would create the first fusion device capable ofproducing thermal energy comparable to the output of a power plant, making commercially viable fusion power
available as soon as 2050.”
The importance of a burning plasma experiment as a required step in the development of practical fusionenergy has been appreciated for decades.3 “A burning plasma experiment would address for the first time thescientific and technological questions that all energy-producing fusion schemes must face.”4 As explained in the1999 Fusion Energy Sciences Advisory Committee (FESAC) report Burning Plasma Physics, “Producing andunderstanding the dynamics of a burning plasma will be an immense physics challenge and the crucial next step inestablishing the credibility of fusion as a source of energy.”5 This finding was also enunciated by previous review
panels, which additionally noted the required international, scientific, and political support for the endeavor toconstruct and operate a burning plasma experiment.6 The President’s Committee of Advisors in Science andTechnology (PCAST) report of the Fusion Review Panel7 and the 1996 report of the Fusion Energy Advisory
Council (FEAC), Restructured Fusion Energy Sciences Program, recommended that the United States should“pursue fusion energy science and technology as a partner in the international effort.”8 The report of the NRC
Fusion Science Assessment Committee recommended that “solid support should be developed within the broad

1

National Research Council (NRC), Letter Report: Burning Plasma Assessment (Phase 1), The National
Academies Press, Washington, D.C., 2002.
2
George W. Bush: Fact Sheet: ITER, January 30, 2003. Available online by G. Peters and J.T. Woolley, The
American Presidency Project, http://www.presidency.ucsb.edu/ws/?pid=80124.
3
See, for example, U.S. Department of Energy (DOE), Final Report of the Fusion Policy Advisory Committee,delivered to Energy Secretary Watkins, Washington, D.C., September 1990.
4
National Research Council (NRC), Letter Report: Burning Plasma Assessment (Phase 1), The National
Academies Press, Washington, D.C., 2002, p. 3.
5
DOE, Burning Plasma Physics, DOE/SC-0041, Fusion Energy Sciences Advisory Committee, Washington,
D.C., September 1999.
6
See, for example, NRC, Cooperation and Competition on the Path to Fusion Energy: A Report, National
Academy Press, Washington, D.C., 1984.
7
President’s Committee of Advisors on Science and Technology, The U.S. Program of Fusion Energy Researchand Development, Fusion Review Panel, Washington, D.C., July 1995.
8
DOE, A Restructured Fusion Energy Sciences Program, Fusion Energy Advisory Committee, Washington,
D.C., January 1996.

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scientific community”9 for U.S. participation in a burning plasma experiment, and the Secretary of Energy Advisory
Board Task Force on Fusion Energy urged “solid support for it throughout the political system.”10
These previous reports, the successful production of 11 MW fusion power in the Tokamak Fusion Test
Reactor experiment11 and 16 MW in JET,12 and the plan for the U.S. magnetic fusion burning plasma experimental
program as developed through the FESAC and Snowmass processes were reviewed by the 2004 NRC Burning
Plasma Assessment Committee.13 The committee’s key recommendation was as follows: “The United States should
participate in the International Thermonuclear Experimental Reactor (ITER) project. If an international agreement tobuild ITER is reached, fulfilling the U.S. commitment should be the top priority in a balanced U.S. fusion science
program.” Following this recommendation, the Department of Energy (DOE) Twenty-Year Outlook14 listed ITER as
the highest priority within the Office of Science.
Following decades of effort, including the International Tokamak Reactor project (1978-1987)15 and the
ITER Engineering Design Activity (1992-1998),16 both facilitated through the International Atomic Energy Agency(IAEA), an international agreement to build and operate a burning plasma experiment was finally formalized in
Paris with the signing of the Agreement on the Establishment of the ITER International Fusion Energy Organization
for the Joint Implementation of the ITER Project in November 2006.17 The ITER International Fusion Energy
Organization is a public international organization, with limited privileges and legal immunities, involving theUnited States with China, the European Union, India, Japan, the Republic of Korea, and the Russian Federation. At
the signing ceremony, DOE Undersecretary for Science Raymond Orbach explained, “ITER is the first stand-alone,
truly international, large-scale scientific research effort in the history of the world.” After an international design
review was completed in 2008,18 ITER construction began in 2010 in Cadarache, France.19 In 2012, by French
Order, ITER became the first of a kind licensed basic nuclear fusion facility.20
By 2013, the estimated cost of ITER construction had grown substantially, and the schedule had slipped bymore than a decade. As a consequence, the ITER Council charged an independent team, chaired by William Madia,
former director of Oak Ridge National Laboratory and Stanford University vice president for the Stanford Linear
Accelerator Center, to determine the causes for ITER’s cost increases and schedule delays and to make management
recommendations. Additionally, a bipartisan group of leaders in the U.S. Senate requested the Government
Accountability Office to investigate the cost and feasibility of ITER and its effect on U.S. fusion programs.21 These
reports helped to motivate significant management improvements taken by the ITER Council,22 which included theaccelerated appointment of a new ITER director general.
In March 2015, Benard Bigot accepted the directorship of the ITER project and created an action plan toimplement the recommendations from the 2013 management review. Following these management improvements,
the resource-loaded plan to first plasma was approved by the ITER Council in June 2016. The ITER Council
9
NRC, An Assessment of the Department of Energy’s Office of Fusion Energy Sciences Program, The National
Academies Press, Washington, D.C., 2001.
10
DOE, Realizing the Promise of Fusion Energy, Final Report of the Secretary of Energy Advisory Board, Task
Force on Fusion Energy, Washington, D.C., August 1999.
11
Hawryluk et al., Results from deuterium-tritium tokamak confinement experiments, Rev. Mod. Phys. 70:537,
1998.
12
Keilhacker et al., High fusion performance from deuterium-tritium plasmas in JET, Nuc Fusion 39:209, 1999.
13
NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.
14
DOE, Facilities for the Future—A Twenty Year Outlook, Office of Science, Washington, D.C., November
2003.
15
See INTOR TEAM, International Tokamak Reactor: Phase 2A, Part III, IAEA, Vienna, 1988.
16
R. Aymar, Present status and future prospect of the ITER project, J Nucl Mater 258:56, 1998.
17
See https://www.iaea.org/sites/default/files/publications/documents/infcircs/2007/infcirc702.pdf.
18
R. Hawryluk et al., Principal physics developments evaluated in the ITER design review, Nuclear Fusion
49:065012, 2009.
19
M. Banks, Construction begins, but ITER’s costs spiral, Phys. World 23(7), 2010.
20
Implementation at ITER of the French Order of 7 February 2012, concerning basic nuclear installations
within the European Domestic Agency, P. Wouters et al., Nucl. Fusion 57:100401m, 2017.
21
U.S. Government Accountability Office, Fusion Energy: Actions Needed to Finalize Cost and Schedule
Estimates for U.S. Contributions to an International Experimental Reactor, Report to Congress, GAO-14-499,
Washington, D.C., June 2014.
22
DOE, U.S. Participation in the ITER Project, Report to Congress, Washington, D.C., May 2016.

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Working Group on the Independent Review of the Updated Long-Term Schedule and Human Resources completed
its review in April 2016, and DOE approved the project execution plan for U.S. contributions to ITER in January
2017.23
Today, ITER construction and fabrication occurs throughout the 100-acre ITER site; more than 1,200
workers are on site; all major buildings are under construction, including cryogenic, tritium, and diagnostic
buildings; and four of six levels of the concrete bioshield for the tokamak have been completed. Importantmilestones have been achieved,24 including completion of the first 2 of 18 110-ton toroidal field coils by aconsortium of European manufacturers in May 2016 and by the Japanese industry in February 2017, followed by thecompletion of the first of two 800-ton vacuum vessel sector sub-assembly tools by Korean manufactures in May
2017. Within the United States, components for the steady state electrical network were delivered in October 2017,
and General Atomics, Inc. (San Diego, California) successfully completed heat treatment of the first of eight central
solenoid coils that, when completed, will be more than 50 feet tall and will be the most powerful pulsed
superconducting magnet in the world. It is noteworthy that after nearly 2 years since the creation of the updated
long-term schedule, the ITER Council reported the project has so far remained on schedule for first plasma in
2025,25 and all 25 milestones due by the end of second-quarter 2017 have been achieved.26
Achievement of government consensus on rejoining ITER, along with broad support within the U.S.
scientific community, was a major accomplishment over the past decade. With this achievement came a necessarychange in focus and priority of the U.S. fusion energy sciences program. As determined by the 2004 NRC Burning
Plasma Assessment Committee, “once the [ITER] decision is made, fulfilling the international commitment to help
construct the ITER facility and participate in the ITER program will necessarily become the highest priority in the
program.”27 The NRC Burning Plasma Assessment Committee further recommended, “A prioritization process
should be initiated by the Office of Fusion Energy Sciences to decide on the appropriate programmatic balance,
given the science opportunities identified and the budgetary situation of the time.” Four years later, the NRC
Committee to Review the DOE Plan for U.S. Fusion Community Participation in the ITER Program28 recommended
that steps should be taken to “seek greater funding stability for the international ITER project to ensure that theUnited States remains able to influence the developing ITER research program, to capitalize on research at ITER to
help achieve U.S. fusion energy goals, to participate in obtaining important scientific results on burning plasmas
from ITER, and to be an effective participant in and beneficiary of future international scientific collaborations.”
Following these NRC recommendations, ITER became a primary research focus of the U.S. program. For
fiscal year (FY) 2014, the U.S. ITER Project received about 40 percent of the U.S. fusion program budget.29 The
DOE Office of Fusion Energy Sciences (FES) annual budget requests to Congress FY2015 through FY2017 statedthat the results from U.S. fusion research “support U.S. goals for future scientific exploration on ITER.”
This focus resulted in significant burning plasma research advancements and improved confidence in ITER
burning plasma performance. However, other fusion energy science and technology efforts that did not directly
support ITER were reduced or eliminated in order to emphasize research in support of ITER. DOE’s FY2005 budget
request to Congress called for reduced U.S. fusion technology efforts. In a letter to FESAC, Undersecretary Orbach
wrote that “funding for the energy relevant technology research and development will wait for the results of ITER”
and further explained, “Until we are confident that we understand the science of fusion, we would be taking an
unacceptable risk to commit the sums required to develop the technology needed to apply that science.”30 The
National Compact Stellarator Experiment under construction at the Princeton Plasma Physics Laboratory was
23
DOE, Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, Office of Science,
Fusion Energy Sciences, Washington, D.C., January 2017.
24
Ned R. Sauthoff, “Perspectives from the US ITER Project,” presented to the NAS Committee for a Strategic
Plan for U.S. Burning Plasma Research on August 29, 2017.
25
International Thermonuclear Experimental Reactor (ITER) Council, Report of the 20th Meeting of the ITER
Council, June 22, 2017, https://www.iter.org/news/pressreleases.
26
Ned R. Sauthoff, “Perspectives from the US ITER Project,” presented to the NAS Committee for a Strategic
Plan for U.S. Burning Plasma Research, August 29, 2017.
27
NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.
28
NRC, A Review of the DOE Plan for U.S. Fusion Community Participation in the ITER Program, The
National Academies Press, Washington, D.C., 2009.
29
DOE FY2015 budget request.
30
Fusion Power Associated, DOE Plans Termination of All Fusion Technology Efforts, FPN04-17, March 10,
2004, http://aries.pppl.gov/FPA/ARC04/fpn04-17.shtml.

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canceled in 2008 in part owing to the higher priority given to participation in ITER, which is based on the tokamak
and not the stellarator concept. Exploratory fusion experiments at the intermediate-scale were eliminated in the
FY2011 budget in favor of research that “can contribute to our understanding and optimizing the tokamak
configuration and configurations closely related to it.”31 The DOE’s FY2013 request for fusion energy science
proposed an “overall reduction in domestic research” while making “a modest increase in funding for scientificcollaborations on major international facilities.” In inflation adjusted amounts, funding for domestic fusion researchhas declined since 2002 while U.S. participation in international research has increased.32
The current priorities of the U.S. DOE/FES program aim to establish a knowledge base that supports U.S.
goals for future scientific exploration on ITER. Using input from three community workshops, the 2015 Ten-Year
Perspective for the DOE/FES program emphasizes three research areas: (1) massively parallel computing with thegoal of validated whole‐fusion‐device modeling, (2) materials research as it relates to plasma and fusion science,and (3) research in the prediction and control of transient events that can be deleterious to toroidal fusion plasma
confinement.33 Research in these areas address two frontiers in fusion and plasma science: “the physics of selfheated burning plasma state” using ITER as the vehicle for gaining access to this state, and the “great scientificchallenge for fusion is to develop materials that can tolerate the extreme conditions created by burning plasma in afusion reactor.” The U.S. DOE/FES program budget is constructed from three elements34: (1) Burning Plasma
Science: Foundations; (2) Burning Plasma Science: Long Pulse; and (3) Burning Plasma Science: High Power. Eachof these three program elements significantly contribute to developing the predictive understanding needed for ITER
operations and providing solutions to high‐priority ITER research needs. A fourth element, Discovery Plasma
Science, supports research that advances fundamental plasma understanding and explores ways to control andmanipulate plasmas for non-fusion applications.
The 2015 Ten-Year Perspective states (p. ii) the overall mission of the U.S. DOE/FES program is “toexpand the fundamental understanding of matter at very high temperatures and densities and build the scientificfoundation needed to develop a fusion energy source.”35 By comparison, EUROfusion (the consortium agreement ofresearch organizations and universities from 26 European Union countries plus Switzerland, Ukraine, and formerly
the European Fusion Development Agreement) is guided by a roadmap to supply fusion electricity to the grid by the2050s.36 Similar national roadmaps leading to the demonstration of fusion power guide research in China37 andJapan.38
Presently, the U.S. fusion research program is focused on future scientific exploration of the burning
plasma state in ITER. If the United States were to withdraw from participation in the ITER project, no alternate plan
exists for accessing critical next-step burning plasma research at a scale leading to commercial fusion energy.
Furthermore, the May 2016 Secretary of Energy’s Report to Congress states, “ITER remains the best candidate
today to demonstrate sustained burning plasma, which is a necessary precursor to demonstrating fusion energy
power.”39
The baseline cost and schedule for U.S. contributions to the ITER’s first plasma subproject are now
formalized.40 Through FY2016, the United States has contributed one-third of its obligated construction costs to firstplasma, or $1,138 million. Including contingency, the remaining U.S. hardware and cash contributions to first
31

T. Feder, U.S. narrows fusion research focus, joins German stellarator, Phys. Today, September 2011, p. 30.
Based on appropriated budgets reported in the DOE Fusion Energy Sciences annual budget requests toCongress for FY2003 and FY2017.
33
DOE, The Office of Science’s Fusion Energy Sciences Program: A Ten‐Year Perspective, Report to Congress,
Washington, D.C., December 2015.
34
See DOE Fusion Energy Sciences annual budget requests to Congress for FY2015 through FY2017.
35
DOE, The Office of Science’s Fusion Energy Sciences Program: A Ten-Year Perspective, Report to Congress,
Washington, D.C., December 2015.
36
European Fusion Development Agreement (EFDA), Fusion Electricity: A Roadmap to the Realization of
Fusion Energy, November 2012, https://www.euro-fusion.org/wpcms/wp-content/uploads/2013/01/JG12.356web.pdf.
37
Wu et al., Identification of safety gaps for fusion demonstration reactors, Nature Energy 1:16154, 2016.
38
Yamada et al., Japanese endeavors to establish technological bases for DEMO, Fusion Eng and Design
109:1318-1325, 2016.
39
DOE, U.S. Participation in the ITER Project, Report to Congress, Washington, D.C., May 2016.
40
DOE, Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, Office of Science,
Fusion Energy Sciences, Washington, D.C., January 2017.
32

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plasma construction is an additional $2,210 million over the next decade. Post-first plasma construction leading toexperiments with a burning plasma will require at least $1,500 million additional summed over the decade after firstplasma. Continued U.S. participation in the ITER project requires an additional $100 million to $125 million
annually for more than two decades, and, “future budget planning for continued support for ITER needs to beconsidered within the context of the total budget for SC [Office of Science], and not merely within the FES
program.”41
These newly baselined cost and schedule estimates for ITER, which is a major component of the U.S.
fusion energy program, and the need for scientific and technological advances in addition to those that will be madewith ITER, define the context for the committee’s consideration of elements within a long-term U.S. fusion energy
research strategy.

41

DOE, U.S. Participation in the ITER Project, Report to Congress, Washington, D.C., May 2016.

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REPRINTED INTERIM REPORT2The Committee’s Information-Gathering Process
The assessments in this report are based on the following: 1












Review of many past studies on magnetic fusion energy and research needs that were written to guidefusion energy research strategy for the United States and for Europe, China, Japan, and the Republic ofKorea;The December 2015 report to Congress from the Acting Director, Department of Energy Office of
Science, titled A Ten-Year Perspective and describing the present U.S. activities in fusion plasma andmaterials science;
The May 2016 report to Congress from the Secretary of Energy on U.S. Participation in theInternational Thermonuclear Experimental Reactor (ITER) Project;
The Project Execution Plan for the U.S. Contributions to ITER Subproject-1 (U.S. ITER SP-1) Project
Number 14-SC-60, released in January 2017;
Narratives from the annual budget request from the Department of Energy, Office of Science Fusion
Energy Sciences Program, and the Reports from the congressional Energy and Water Development
Appropriations Subcommittees;
Briefings, reports of ongoing research, and presentations of strategies provided as input to thecommittee as part of the public record;
Written documents and oral presentations made during the first two meetings of the committee;
Input from the first of two community workshops on strategic directions for U.S. magnetic fusion
research held at the University of Wisconsin, Madison, from July 24-28, 2017;
Relevant review articles published in the scientific literature—for example, describing (1) scientificand technical achievements since the 2004 report of the National Research Council (NRC) Burning
Plasma Assessment Committee,2 (2) the magnetic fusion energy development path,3 (3) the scientificopportunity afforded by study of a burning plasma experiment,4,5 and (4) the plan of Director General
Bernard Bigot to correct organizational problems and sustain ITER construction performance;6 andExpertise of the committee’s membership including magnetic and inertial fusion energy, fusionmaterials science, fusion engineering science, plasma science, and nuclear science and engineering.

A short description of the science and history of magnetic fusion energy research is given in Appendix A.
The statement of task for the committee is in Appendix B. The agendas for the committee’s first two meetings areprovided in Appendix C. A bibliography of prior reports and studies consulted by the committee is provided inAppendix D.

1

See Appendix D for the source material used for the committee’s information-gathering process.
National Research Council, Burning Plasma: Bringing a Star to Earth, The National Academies Press,
Washington, D.C., 2004.
3
C.L. Smith and S. Cowley, The path to fusion power, Philosophical Transactions of the Royal Society A:
Mathematical, Physical and Engineering Sciences 368:1091, 2010.
4
J. Ongena, R. Koch, R. Wolf, and H. Zohm, Magnetic-confinement fusion, Nature Phys 34:398, 2016.
5
A. Fasoli, S. Brunner, W.A. Cooper, J.P. Graves, P. Ricci, O. Sauter, and L. Villard, Computational challenges
in magnetic-confinement fusion physics, Nature Phys 12:411, 2016.
6
B. Bigot, Nuclear physics: Pull together for fusion, Nature 522:149, 2015.
2

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3
Importance of Burning Plasma Research
The committee reaffirms the importance of burning plasma research to the development of fusion energy,
as well as to plasma science and other science and engineering disciplines.

IMPORTANCE TO THE DEVELOPMENT OF FUSION ENERGY: CONTROLLING A BURNING
PLASMAAs explained in the 2004 report of the Burning Plasma Assessment Committee of the National ResearchCouncil (NRC), “A burning plasma experiment would address for the first time all of the scientific andtechnological questions that all magnetic fusion schemes must face. Such an experiment is the crucial element
missing from the world fusion energy science program and a required step in the development of practical fusionenergy.”1 The integrated challenges of understanding the dynamics of a burning plasma and of applying the hightechnology know-how to heat, sustain, and control a burning plasma within the International Thermonuclear
Experimental Reactor (ITER) has helped to focus research, improve understanding and predictive capability, andaddress key concerns such as transients, increasing confidence in the success of ITER as a burning plasma
experiment.
Experiments within the United States have led to significant progress in all important areas identified in the2004 NRC report. These are as described below.
A burning plasma experiment will represent the first time that a confined fusion plasma is dominated byfusion-born alpha particles. Energetic alpha particles from fusion reactions are predicted to drive plasma
instabilities, which could, if not mitigated, substantially reduce fusion power produced and potentially damage thereactor inner wall. Consequently, it is vital to understand how energetic alpha particles affect plasma dynamics. In
2004, such instabilities had been observed and their behavior in different circumstances had begun to be
characterized. Now, the onset of energetic particle instabilities is understood, and promising techniques to control
these instabilities are being investigated. Predictive models are being developed and compared to advanced
fluctuation and fast ion diagnostic measurements. Despite considerable progress understanding fusion-born alphaphysics, detailed identification of nonlinear mechanisms is just beginning. Beyond validation of theoretical models,
important research areas also include methods to control energetic particles instability for helpful purposes such asfavorably modifying the current profile or to govern the nonlinear dynamics to control fusion burn.2,3
A burning plasma experiment advances understanding of plasma transport properties from the core to theboundary. A burning plasma can be divided into an inner high-temperature core where fusion reactions occur, asurrounding insulating layer called the pedestal, and a boundary layer where escaping plasma flows to a protective
divertor. Since 2004, major advances in theory and computation have resulted in detailed understanding of turbulent
transport in the plasma core and the key physics processes regulating the pedestal structure in high-confinementmode (called “H-mode”) plasmas. Recently developed computational techniques to couple core and edge physics
1
National Research Council (NRC), Burning Plasma: Bringing a Star to Earth, The National Academies Press,
Washington, D.C., 2004.
2
Chen and Zonca, Physics of Alfvén waves and energetic particles in burning plasmas, Rev Mod Phys
88:015008, 2016.
3
Gorelenkov, Pinches, Toi, Energetic particle physics in fusion research in preparation for burning plasma
experiments, Nuc Fusion 54:125001, 2014.

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have been extensively tested against experiments, resulting in significantly improved capability to predict fusion
performance.4 For illustration, these computational tools predicted new high-performance regimes that were
subsequently observed in experiments of the U.S. fusion research program.5 Although there has been considerable
progress made in predicting plasma transport, the validity of these predictions must be tested in future burning
plasma experiments. Some of the highest performance discharges studied in DIII-D experiments decrease
performance when produced with lower injected torque, as expected in ITER.6 Furthermore, additional research isneeded to understand confinement scaling towards desirable fusion reactor conditions characterized by high plasmabeta, steady state, and compatible divertors.
A burning plasma experiment enables critical tests to control plasma transients. Due to the large stored
energy of a burning plasma, transient events, which cause rapid energy loss from the plasma, present a significant
risk to material lifetimes. Transients include disruptions (i.e., when plasma current and confinement are lost) andedge localized modes (ELMs) (i.e., the outer edge plasma is lost). Since 2004, the United States has madesubstantial progress understanding transients and demonstrating methods either to avoid or to mitigate transients.
Notably, ELMs can be avoided via U.S.-discovered operation regimes, such as the Quiescent H-Mode (Q-H-mode),7
Enhanced Pedestal H-mode (EP-H-mode), or I-mode regime,8 or actively controlled by applying resonant magnetic
perturbations9 (a technique pioneered in the United States), pellet injection, and position control.10 The United States
has also led the world in the development of techniques for understanding, as well as predicting, avoiding and/or
controlling disruptions of the plasma current—the latter by massive gas injection,11 shattered pellets, and shellpellets.12 These techniques are critical for ITER and other burning plasma devices based on the tokamak; however,additional research is needed to understand the science of both ELM suppression and disruption avoidance at thehigher temperatures, magnetic energies, and potentially longer current quench times expected in a burning plasma
experiment.13
A burning plasma experiment advances divertor science necessary for a fusion power source. Unlesscontrolled, the power escaping from a burning plasma will lead to inner wall damage. Control of escaping heat andparticles is made by carefully shaping the magnetic field so that plasma flows along the plasma boundary14 and intoa divertor, where the plasma heat and particle flux can be nearly extinguished by interaction with recycling
neutrals.15 Additionally, because carbon-based first-wall materials must have low tritium retention,16 important
plasma-material processes such as erosion, tritium co-deposition, dust generation, and neutron-irradiation damage
4

Kinsey et al., ITER predictions using the GYRO verified and experimentally validated trapped gyro-Landau
fluid transport model, Nuc Fusion 51:083001, 2011.
5
Solomon et al., Exploration of the Super H-mode regime on DIII-D and potential advantages for burning
plasma devices, Phys Plasmas 23:056105, 2016.
6
Buttery et al., DIII-D research to address key challenges for ITER and fusion energy, Nuc Fusion 55:104017,
2015.
7
Snyder et al., Stability and dynamics of the edge pedestal in the low collisionality regime: Physics
mechanisms for steady-state ELM-free operation, Nuc Fusion 47:961-968, 2007.
8
Whyte et al., I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator CMod, Nuc Fusion 50:105005, 2010.
9
Evans et al., RMP ELM suppression in DIII-D plasmas with ITER similar shapes and collisionalities, Nuc
Fusion 48:024002, 2008.
10
Loarte et al., Progress on the application of ELM control schemes to ITER scenarios from the non-active
phase to DT operation, Nuc Fusion 54:033007, 2014.
11
Hollmann et al., Measurements of injected impurity assimilation during massive gas injection experiments in
DIII-D, Nuc Fusion 48:115007, 2008.
12
Commaux et al., Demonstration of rapid shutdown using large shattered deuterium pellet injection in DIII-D,
Nuc Fusion 50:112001, 2010.
13
Lehnen et al., Impact and mitigation of disruptions with the ITER-like wall in JET, Nuc Fusion 53:093007,
2013.
14
Goldston, Heuristic drift-based model of the power scrape-off width in low-gas-puff H-mode tokamaks, Nuc
Fusion 52:013009, 2012.
15
Krasheninnikov et al., Edge and divertor plasma: Detachment, stability, and plasma-wall interactions, Nuc
Fusion 57:102010, 2017.
16
Skinner et al., Recent advances on hydrogen retention in ITER’s plasma-facing materials: Beryllium, carbon,
and tungsten, Fusion Sci and Tech 54:891, 2008.

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require evaluation in a burning plasma experiment.17 The U.S. research program has significantly advanced
understanding of burning plasma boundary physics, including improved understanding of the narrow “scrape-off
layer” connecting the confined plasma to the divertor. The U.S. research program has also developed andsuccessfully tested several innovative divertor concepts.18,19 Further developments for a divertor with long lifetime
remains a major fusion research challenge.
A burning plasma experiment tests integrated scenarios that simultaneously test the requirements forstability, confinement, fuel purity, and compatibility with plasma-facing components needed for a fusion energy
source. Since 2004, plasma operation and control scenarios have been developed and tested in preparation for ITER
experiments.20 Additionally, high-fidelity integrated models,21 which take full benefit from advances in highperformance computing, are now routinely used to interpret experimental measurements and make progress in
predicting the results of burning plasma experiments.22 The U.S. research program has led the world in thedevelopment of quiescent plasma scenarios not subject to damaging transient events23 and the so-called “advanced
inductive scenario,”24 which can achieve the same plasma performance at reduced plasma current and so minimize
the risk of disruption damage. A burning plasma experiment can also test other advanced scenarios, like the socalled “super H-mode,” which represents an attractive area of innovation aimed to reduce the size of a fusion device
with improved confinement. Further research using a burning plasma experiment is needed to develop understanding
for integrated scenarios that address the challenges of steady-state operation, robust stability at low plasma rotationand high plasma pressure,25 and compatible divertor concept.26,27
The importance of U.S. advances in these key areas has been broadly recognized. For example, theEuropean Physical Society named plasma physicists working in the United States during 6 of the 18 years sinceawarding the prestigious Hans Alfvén Prize.28 Also, 8 of the 11 Nuclear Fusion Awards were presented to U.S.
scientists working on scenarios, transport, stability, transient control, boundary, and pedestal physics.29

IMPORTANCE TO THE DEVELOPMENT OF FUSION ENERGY: FUSION TECHNOLOGY
While burning plasma science has progressed since the 2004 NAS burning plasma assessment, significant
advancements in fusion technology are needed for a burning plasma reactor. Below are brief descriptions of a17

Roth et al. Recent analysis of key plasma wall interactions issues for ITER, J Nuc Materials 390-91:1-9,

2009.
18

Kugel et al., Evaporated lithium surface coatings in NSTX, J. Nuc Materials 390-91:1000-1004, 2009.
Umansky et al., Attainment of a stable, fully detached plasma state in innovative divertor configurations,Phys Plasmas 24:056112, 2017.
20
Solomon et al., DIII-D research advancing the scientific basis for burning plasmas and fusion energy, Nuc
Fusion 57:102018, 2017.
21
McClenaghan et al., Transport modeling of the DIII-D high beta(p) scenario and extrapolations to ITER
steady-state operation, Nuc Fusion 57:116019, 2017.
22
Sips et al., Progress in preparing scenarios for operation of the International Thermonuclear Experimental
Reactor, Phys Plasmas 22:021804, 2015.
23
Hubbard et al., Physics and performance of the I-mode regime over an expanded operating space on Alcator
C-Mod, Nuc Fusion 57:126039, 2017.
24
Luce et al., Development of advanced inductive scenarios for ITER, Nuc Fusion 54:013015, 2014.
25
Evans et al., ELM suppression in helium plasmas with 3D magnetic fields, Nuc Fusion 57:086016, 2017.
26
Wenninger et al., Advances in the physics basis for the European DEMO design, Nuc Fusion 55:063003,
2015.
27
Ongena et al., Magnetic-confinement fusion, Nat Phys 34:398, 2016.
28
Alfvén Prize winners: Marshall N. Rosenbluth (2002), Liu Chen (2008), Allen Boozer (2010), Patrick
Diamond and Akira Hasegawa (2011), Miklos Porkolab (2013), and Nathaniel Fisch (2015). (See
http://plasma.ciemat.es/eps/awards/alfven-prize/).
29
The Nuclear Fusion Award has been given annually since 2006. U.S. award recipients are Tim Luce (2006
General Atomics), Todd Evans (2008 General Atomics), Steve Sabbagh (2009 Columbia University), John Rice(2010 MIT), Pat Diamond (2012 University of California, San Diego), Dennis Whyte (2013 MIT), Phil Snyder(2014 General Atomics), and Rob Goldston (2015 Princeton University). See http://wwwpub.iaea.org/books/iaeabooks/Nuclear_Fusion/NF/NFAward.
19

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selected number of important science and technology contributions from fusion technology research and theirimpacts on fusion energy development.
Fusion blanket design, tritium breeding, fuel processing. A fusion breeding blanket—that is, a nuclear
system that creates tritium via interaction of the fusion-produced 14-MeV neutrons with lithium—is a key fusion
nuclear technology needed for the development of fusion energy. Fusion reactors must operate with more tritium
produced and recovered than is burned. The vast majority of the fuel injected in a fusion chamber will not be burnedin a single pass. Unburned deuterium-tritium fuel will be continuously transported to the plasma edge, where it must
be exhausted, stripped of impurities, and then reinjected into the plasma. A burning plasma experiment provides theopportunity to test and evaluate the performance of prototypical blanket modules and demonstrate technologies fortritium extraction from blankets and for fuel processing systems that can be operated efficiently at large scale.30,31,32
Fusion safety, remote handling, and waste management. A burning plasma experiment offers theopportunity to begin development of the technologies needed for a fusion reactor, including important safety-related
technologies. Many components and systems needed for fusion’s safety objectives are unique, such as source
diagnostics and cleaning technologies, state-of-the-art safety analyses tools, technologies for the remote handling oflarge activated components, technologies for the control of routine tritium releases, and innovative approaches forthe control of tritiated and mixed waste streams.33 A burning plasma experiment will be an integrated demonstrationof the safety, reliability, and effectiveness of these technologies.34
Fusion materials science. The behavior and integrity of materials in a fusion system are of great importanceto the long-term viability of fusion energy.35 The high flux of energetic neutrons to the vessel and structural
materials poses a serious materials problem that will require substantial testing, some of which may be done on aburning plasma experiment.36 The high energy neutrons from the D-T fusion reaction generate between 50- to 100times-higher He/dpa in materials such as ferritic steels than does fission reactor irradiation. Burning plasma
experiments will also aid in the development of high-heat-flux components and will serve as testbeds in which toevaluate the performance of the components in a reactor-like fusion environment. The heat loads on components in aburning plasma experiment will be comparable to those expected in a reactor and will require the application ofstate-of-the-art high-heat-flux technology using materials that satisfy requirements of tritium retention, safety,
structural integrity, lifetime, and plasma compatibility.37,38,39
Plasma heating and current drive systems for fusion. Plasma heating by electromagnetic waves and neutral
particle beams are needed to heat the plasma to a burning state,40 sustain plasma current,41 modify temperature andcurrent profiles, and control plasma instabilities.42 Ion cyclotron heating is one primary method for heating the bulk
plasma, while lower hybrid current drive is perhaps the most efficient radio-frequency method to drive a steady-state

30

Sawan and Abdou, Physics and technology conditions for attaining tritium self-sufficiency for the DT fuelcycle, Fusion Eng and Design 81:1131-1144, 2006.
31
Giancarli et al., Overview of the ITER TBM Program, Fusion Eng and Design 87:395, 2012.
32
National Research Council, Burning Plasma: Bringing a Star to Earth, The National Academies Press,
Washington, D.C., 2004.
33
Girard et al., TER, safety and licensing, Fusion Eng Des 82:506, 2007.
34
Bornschein et al., Tritium management and safety issues in ITER and DEMO breeding blankets, Fusion Eng
Des 88:466, 2013.
35
Zinkle and Snead, Designing radiation resistance in materials for fusion energy, Annu. Rev. Mater. Res.
44:241, 2014.
36
NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.
37
Raffray et al., High heat flux components-Readiness to proceed from near term fusion systems to power
plants, Fusion Eng and Design 85:93-108, 2010.
38
NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.
39
Ibid.
40
Omori et al., Overview of the ITER EC H&CD system and its capabilities, Fusion Eng and Design 86:951954, 2011.
41
Cesario et al., Current drive at plasma densities required for thermonuclear reactors, Nature Comm 1:55,
2010.
42
Sauter et al., On the requirements to control neoclassical tearing modes in burning plasmas, Plasma Phys
Control Fusion 52:025002, 2010.

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toroidal current. Sources are available for both applications.43 Electron cyclotron resonance heating can also be used
for bulk electron heating, profile control, pre-ionization/startup, and current drive in burning plasmas, but here
further source development is still needed. Fusion reactor research continues to push the frontiers of high power
mm-wave and radio-frequency technology.44
High-field magnet technology for fusion. Strong magnetic fields are critical to the success of magnetic
fusion as a source of energy. Achieving higher magnetic field strength extends the allowable plasma properties tohigher plasma density, higher plasma current, and higher plasma pressure while retaining the same dimensionlessscaling parameters found at lower magnetic field strength. This extended range of plasma parameters from highfield magnets allows more compact tokamak devices that may provide a lower cost path to future fusion reactors.
ITER’s superconducting magnet system will be the largest ever made and is designed to operate with the highest
practical magnetic field strength for large toroidal field coils made of Niobium-Tin superconductors and consistent
with the strength of steel.45 New developments of rare-earth barium-copper-oxide high-temperature superconductors
may lead to larger magnetic field strength and potentially improve the prospects for magnetic fusion energy.46,47
However, the costs and performance of these advanced superconductors will not be fully understood without
experience at the industrial scale,48 and new integrated scenarios for high-field fusion must be developed andtested.49
Integrated systems engineering for fusion. Systems engineering combines plasma physics and engineering
constraints into a self-consistent integrated design for large-scale fusion facilities. Systems engineering studies havebeen carried out for various types of tokamak reactors, including the advanced tokamak,50 high-field tokamak,51
spherical tokamak, and stellarator.52 The recent Advanced Reactor Innovation and Evaluation Study—Advanced andConservative Tokamak tokamak studies53 are a good example covering the four possible options of optimistic versus
conservative physics and/or engineering. The value of these studies is to learn the strengths and weaknesses of any
given concept and to point out which physics or engineering quantities have high leverage in improving reactor
performance and economics.

43
Hill et al., DIII-D research towards resolving key issues for ITER and steady-state tokamaks, Nuc Fusion
53:104001, 2013.
44
Thumm, M., Recent advances in the worldwide fusion gyrotron development, IEEE Trans Plasma Sci
42:590-599, 2014.
45
Mitchell and Devred, The ITER magnet system: Configuration and construction status, Fusion Eng. Des.
2017, http://dx.doi.org/10.1016/j.fusengdes.2017.02.085, in press.
46
Fietz et al., Prospects of high temperature superconductors for fusion magnets and power applications, Fusion
Eng Des 88:440, 2013.
47
Takayasu et al., Investigation of HTS twisted stacked-tape cable (TSTC) conductor for high-field, highcurrent fusion magnets, IEEE Trans Applied Superconductivity 27:1, 2017.
48
Green and Strauss, Things to think about when estimating the cost of magnets made with conductors otherthan Nb-Ti, IEEE Trans on Applied Superconductivity 27:1, 2017.
49
Whyte et al., Smaller and sooner: Exploiting high magnetic fields from new superconductors for a more
attractive fusion energy development path, J Fusion Energy 35:41, 2016.
50
Chan et al., Physics basis of a fusion development facility utilizing the Tokamak approach, Fusion Sci andTechnology 57:66-93, 2010.
51
Whyte et al., Smaller and sooner: Exploiting high magnetic fields from new superconductors for a more
attractive fusion energy development path, J Fusion Energy 35:41, 2016.
52
Menard et al., Prospects for pilot plants based on the tokamak, spherical tokamak and stellarator, Nuc Fusion
51:103014, 2011.
53
C.E. Kessel et al., The ARIES Advanced and Conservative Tokamak Power Plant Study, Fusion Science andTechnology 67:1-21, 2015, doi: 10.13182/FST14-794.

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REPRINTED INTERIM REPORTIMPORTANCE TO PLASMA SCIENCE AND OTHER SCIENCE
The process of creating a fusion-based energy supply on Earth has led to technological and scientificachievements of far-reaching impact that touch every aspect of our lives. Those largely unanticipated advances spana wide variety of fields in science and technology and were the focus of a 2015 Fusion Energy Sciences Advisory
Committee report, Applications of Fusion Energy Research: Scientific and Technological Advances Beyond
Fusion.54 There are many synergies between research in plasma physics and other fields, including high-energy
physics and condensed matter physics, dating back many decades. For instance, the formulation of a mathematicaltheory of solitons, solitary waves which are seen in everything from plasmas to water waves to Bose-Einstein
Condensates, has led to an equally broad range of applications in the fields of optics, fluid mechanics, andbiophysics. Another example, the development of a precise criterion for transition to chaos in Hamiltonian systems
has offered insights into a range of phenomena including planetary orbits, two-person games, and changes in theweather.55 Burning plasma physics also contributes to understanding important plasma processes like magnetic
reconnection,56 kinetic turbulent processes in magnetized plasma,57 nonlinear wave-particle interactions andresonances,58 and multi-scale phenomena that are also common to space and astrophysical plasma.59 Materials
research in support of burning plasma science contributes to better understanding of irradiated materials.60,61
Additionally, fusion facilities can be used to advance fundamental and non-fusion plasma physics.62
In assessing the importance of burning plasma research to other fields of science and technology, thecommittee notes that the Department of Energy Office of Fusion Energy Sciences distinguishes “burning plasma
research” from the “discovery plasma science” component of the its program. It is not, in the committee’s opinion,
possible to justify the construction of a burning plasma experiment based on its ability to answer questions of
relevance to other fields (for example, astrophysics), yet the broad program that must necessarily be in place toexploit the results from such an experiment will have a profound effect on other fields. For example, the tremendous
advances made in computational plasma physics addressing burning plasma issues have had, and will continue tohave, important impact on space and astrophysical questions where the intrinsic multi-scale, multi-physics nonlinear
interactions can only be addressed by large-scale computations.63 Generally speaking, burning plasma research acts
as an important driver for the development of novel concepts and methods at the interface between plasma physics,
materials science,64 applied mathematics,65 and computer science,66 with wide visibility and impact.67
54

U.S. Department of Energy (DOE), Applications of Fusion Energy Sciences Research: Scientific Discoveries
and New Technologies Beyond Fusion, Fusion Energy Sciences Advisory Committee, Office of Science, September
2015, https://science.energy.gov/~/media/fes/fesac/pdf/2015/2101507/FINAL_FES_NonFusionAppReport_090215.pdf.
55
Ibid.
56
Yamada, Kulsrud, and Ji, Magnetic reconnection, Rev. Mod. Phys. 82:603, 2010.
57
Howes, Kinetic Turbulence, pp. 123-152 in Magnetic Fields in Diffuse Media (Lazarian, de Gouveia Dal
Pino, and Melioli, eds.), Springer Berlin Heidelberg, Berlin, Heidelberg, 2015.
58
Breizman, Nonlinear consequences of energetic particle instabilities, Fusion Sci and Tech. 59:549-560, 2011.
59
Burch et al., Magnetospheric multiscale overview and science objectives, Space Sci Rev 199:5-21, 2016.
60
Zinkle and Snead, Designing radiation resistance in materials for fusion energy, Annu. Rev. Mater. Res.
44:241, 2014.
61
Bai et al., Efficient annealing of radiation damage near grain boundaries via interstitial emission, Science
327:1631, 2010.
62
See, for example, the DIII-D Frontier Science Campaign, https://fusion.gat.com/global/diii-d/frontier.
63
Schekochihin et al., Astrophysical gyrokinetics: Kinetic and fluid turbulent cascades in magnetized weakly
collisional plasmas, ApJS 182:310, 2009.
64
Odette, Alinger, and Wirth, Recent developments in irradiation-resistant steels, Ann Rev Mat Res. 38:471503, 2008.
65
Dongarra, Hittinger (Co-Chairs) et al., Applied Mathematics Research for Exascale Computing, Report of
DOE Working Group on Exascale Mathematics, 2014,
http://science.energy.gov/~/media/ascr/pdf/research/am/docs/EMWGreport.pdf.
66
Batchelor et al., Simulation of fusion plasmas: Current status and future direction, Plasma Sci and Techn
9:312, 2007.
67
DOE, Scientific Grand Challenges: Fusion Energy Science and the Role of Computing at the Extreme Scale,
Report from the DOE Workshop, held March 18-20, 2009, Washington, D.C.

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REPRINTED INTERIM REPORTThe substantial impacts of burning plasma research on science, technology, and engineering were identified
in the 2004 Burning Plasma Assessment Committee report,68 and these have continued in several areas: (1) basic
plasma science, (2) low-temperature plasmas, (3) space and astrophysical plasmas, (4) high energy density
laboratory plasmas and inertial fusion energy, and (5) particle accelerator technology. Another area of technology
which has benefitted from fusion research is high frequency high power millimeter wave sources (e.g., gyrotrons69),
which have medical and industrial processing applications.70

68

NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.
Rzesnicki et al., 2.2-MW record power of the 170-GHz European Preprototype Coaxial-Cavity Gyrotron for
ITER, IEEE Trans Plasma Sci 38, pp. 1141-1149, 2010.
70
Sabchevski et al., A dual-beam irradiation facility for a novel hybrid cancer therapy, J. Infrared Millimeter
and THz Waves 34:71, 2013.
69

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4
Status of U.S. Research that Supports Burning Plasma Science

Since the National Research Council (NRC) report in 2004,1 the United States has undertaken an enormous
effort in experimental, theoretical, and computational research in support of burning plasma science. The U.S.
research program motivated world-leading contributions to science and technology in support of the International
Thermonuclear Experimental Reactor (ITER) and other major international fusion experiments. However, theclosure of domestic fusion research facilities and the failure either to upgrade or to start new medium-scale
experiments, together with substantially decreased funding to fusion nuclear science and technology research,creates concern as to whether the United States will continue to be a scientific leader in the field.

BURNING PLASMA SCIENCE
U.S. fusion scientists and engineers have contributed a substantial number of new, innovative ideas to thestudy of burning plasma science, including the following examples.

Theory and Simulation to Understand and Predict Burning Plasma Dynamics
The U.S. Department of Energy (DOE) Office of Fusion Energy Sciences (FES) theory and simulation
program is organized into a base program, including several Scientific Discovery through Advanced Computation(SciDAC) centers2 focused on developing advanced simulation capabilities. U.S. scientists are recognizedinternationally as leading the world both in basic theory and in simulation. For example, U.S. researchers led
important efforts in understanding multi-scale turbulent transport,3,4,5 energetic particle physics,6 and pedestal
physics.7 Many of the most widely employed simulation codes and physics models have been developed within the
U.S. theory and simulation program. A recent workshop collaboratively sponsored by the DOE Office of Advanced
Scientific Computing Research and DOE/FES documented the status, codes, opportunities, and challenges of

1

National Research Council (NRC), Burning Plasma: Bringing a Star to Earth, The National Academies Press,
Washington, D.C., 2004.
2
Current fusion SciDAC centers are listed online, with research focus on edge physics, multiscale integrated
modeling, and materials science (http://www.scidac.gov/fusion/fusion.html).
3
Ku, Chang, and Diamond, Full-f gyrokinetic particle simulation of centrally heated global ITG turbulencefrom magnetic axis to edge pedestal top in a realistic tokamak geometry, Nuc Fusion 49:115021, 2009.
4
Howard et al., Multi-scale gyrokinetic simulation of tokamak plasmas: Enhanced heat loss due to cross-scale
coupling of plasma turbulence, Nuc Fusion 56:014004, 2015.
5
N.T. Howard et al., Multi-scale gyrokinetic simulations of an alcator C-Mod, ELM-y H-mode plasma, Plasma
Phys. Control. Fusion 60:014034, 2018.
6
Fasoli et al., Physics of energetic ions, Nuc Fusion 47:S264-S284, 2007.
7
Ferraro, Jardin, and Snyder, Ideal and resistive edge stability calculations with M3D-C-1, Phys Plasmas
17:102508, 2010.

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integrated simulations for magnetic fusion energy sciences.8 In recent years, understanding of key areas such as
coupled core/pedestal transport and stability has advanced to the point where detailed predictions can be made inadvance of experiments. Indeed, new high-performance regimes of operation have been predicted and later observedin experiments motivated directly by theoretical predictions.9 These same predictive tools have been employed todevelop high-performance scenarios for ITER and other planned devices.10 The capability exists to use theoreticalunderstanding to optimize devices and achieve higher performance. While the U.S. theory program is focused
primarily on tokamak research, key innovations have also been developed in other areas, such as the idea of quasisymmetry in stellarators to reduce transport.11
Exascale computing platforms present great opportunities for computational physics.12 The increased
computing power should allow researchers to investigate new and previously inaccessible problems in burning
plasma science.13 Equally important, exascale computing should greatly improve the community’s ability tounderstand and predict experiments with validated sophisticated numerical models. Exascale computing cansubstantially improve our understanding of burning plasma physics and guide experiment planning, but computation
will not be a substitute for actually building and carrying out experiments needed to validate models, even at theexascale. Fusion energy simulations14 have been selected as an application area of the new Exascale Computing
Project, a collaborative effort of the DOE Office of Science and the National Nuclear Security Administration.

Medium-Scale Fusion Research Facilities
Until the end of fiscal year (FY) 2016, the United States supported three medium-scale experimental
facilities: the DIII-D tokamak at General Atomics in San Diego, the National Spherical Torus Experiment-Upgrade(NSTX-U) located at PPPL, and the Alcator C-Mod high-field tokamak at the Massachusetts Institute of Technology(MIT). Descriptions of these three facilities are given, for example, in the DOE FY2016 Congressional Budget
Request (pp. 137-138).15 The DIII-D tokamak began operation in 1986. The DIII-D research goal is to “establish thescientific basis to optimize the tokamak approach to magnetic confinement fusion”16 through the exploration ofplasma control techniques and conditions scalable to ITER and future fusion reactors. NSTX-U is a low-aspect ratio
tokamak designed to assess the spherical tokamak as a possible fusion neutron source, study the plasma-materialinterface, and advance toroidal confinement physics. NSTX-U is an upgrade of the NSTX experiment that operated
from 1999 to 2011. NSTX-U was dedicated in May 2016 but is now undergoing repairs and is not presently
operating. The Alcator C-Mod tokamak began operation in 1991. C-Mod is a compact tokamak using strong
magnetic fields to confine high-pressure plasma in a small volume. The compact size and high magnetic field of the
Alcator C-Mod tokamak allow operation at and above the ITER design values for magnetic field and plasma
density, and it has all-metal walls that experience heat fluxes approaching those projected for ITER. As aconsequence of the DOE/FES 2013 decision to reduce domestic fusion research, the operation of the Alcator C-Mod
tokamak ended in October 2016,17 immediately following experiments that set the world’s record for volume8

U.S. Department of Energy (DOE), Integrated Simulations for Magnetic Fusion Energy Sciences, Report fromthe DOE Workshop held June 2-4, 2015, Washington, D.C.
9
Snyder et al., Super H-mode: Theoretical prediction and initial observations of a new high-performance
regime for tokamak operation, Nuc Fusion 55:083026, 2015.
10
Snyder et al., A first-principles predictive model of the pedestal height and width: Development, testing and
ITER optimization with the EPED model, Nuc Fusion 51:103016, 2011.
11
Xanthopoulos et al., Controlling turbulence in present and future stellarators, Phys Rev Lett 113:155001,
2014.
12
DOE, Scientific Grand Challenges: Fusion Energy Science and the Role of Computing at the Extreme Scale,
Report from the DOE Workshop held March 18-20, 2009, Washington, D.C.
13
DOE, Integrated Simulations for Magnetic Fusion Energy Sciences, Report from the DOE Workshop held
June 2-4, 2015, Washington, D.C.
14
See https://www.exascaleproject.org/pppl-physicists-win-ecp-funding/.
15
DOE, FY2016 Congressional Budget Request for Fusion Energy Sciences, Office of Science, Washington,
D.C., 2015, p. 137-138.
16
See https://science.energy.gov/fes/research/advanced-tokamak/.
17
MIT News, Alcator C-Mod tokamak nuclear fusion reactor sets world record on final day of operation,
October 14, 2016, https://phys.org/news/2016-10-alcator-c-mod-tokamak-nuclear-fusion.html.

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averaged plasma pressure contained within a magnetically confined fusion device. Many of the significant
accomplishments noted in Chapter 3 resulted from pioneering experiments conducted using these three mediumscale facilities.
In addition to mid-scale research facilities, the U.S. fusion energy sciences program provided about 1.6
percent (approximately $7 million) of the FY2016 budget18 to operate small exploratory experiments, primarily atuniversities, in support of foundational burning plasma research and long-pulse burning plasma research.
Proposals for new facilities and facility upgrades were recommended by the 2013 Fusion Energy Sciences
Advisory Committee (FESAC) Subcommittee on the Prioritization of Proposed Scientific User Facilities19 and by
the 2014 FESAC Subcommittee on Strategic Planning.20 These U.S. facility initiatives included major upgrades tothe DIII-D and NSTX-U experiments and plans for construction of a Fusion Nuclear Science Facility. Additionally,
the Advanced Divertor Experiment was proposed as an upgrade to the Alcator C-Mod facility at MIT.21
A strength of the U.S. program is the close coupling between theoretical and experimental research. Owing
to their excellent diagnostics and flexibility, medium-scale facilities are well suited to test and validate experimental
models. These validated models are beginning to provide the ability to predict new, and potentially more attractive,
operating regimes.
The current U.S. fusion research strategy has an increasing focus on U.S. participation in newer
international long-pulse experiments with superconducting magnets including EAST (China),22 KSTAR (Republicof Korea),23 and Wendelstein 7-X (Germany).24 EAST began operation in 2006 and KSTAR began in 2009. The
Wendelstein 7-X stellarator began operation in December 2015, requiring €350 million for the stellarator device25
and additional amounts for personnel and materials during construction. The HL-2M tokamak is under construction
at the Southwestern Institute of Physics26 as an upgrade to the existing HL-2A27 device. HL-2M will have higher
plasma heating power and magnetic field strength to explore higher-pressure, fusion-relevant plasma. The JT-60SA
tokamak in Japan is under construction as a Japan-Europe project and is expected to begin operation in 2020.28 NonU.S. proposals for new facilities include the superconducting Divertor Tokamak Test facility29 that would be built
by the Italian National Agency for New Technologies, Energy, and Sustainable Economic Development’s fusion
laboratory in Frascati, Italy, and the China Fusion Engineering Test Reactor30 under consideration as a new fusion
facility to demonstrate self-sufficient tritium breeding. While researchers in the U.S. fusion community welcome
these international opportunities, presentations to the committee31 and during the first fusion community workshop32
18

DOE, FY2016 Congressional Budget Request for Fusion Energy Sciences, Office of Science, 2015, p. 137-

138.
19

DOE, Report of the FESAC Subcommittee on the Prioritization of Proposed Scientific User Facilities for the
Office of Science, Fusion Energy Sciences Advisory Committee, Washington, D.C., March 21, 2013.
20
DOE, Report on Strategic Planning: Priorities Assessment and Budget Scenarios, Fusion Energy Sciences
Advisory Committee, Washington, D.C., December 2014.
21
LaBombard et al., ADX: A high field, high power density, advanced divertor and RF tokamak, Nuc Fusion
55:053020, 2015.
22
Wu, An overview of the EAST project, Fusion Eng and Design 82:463, 2007.
23
Oh et al., Commissioning and initial operation of KSTAR superconducting tokamak, Fusion Eng and Design
84:344, 2009.
24
Bosch et al., Final integration, commissioning and start of the Wendelstein 7-X stellarator operation, Nuc
Fusion 57:116015, 2017.
25
See http://www.ipp.mpg.de/4010154/02_16.
26
Liu et al., Assembly study for HL-2M tokamak, Fusion Eng Design 96-97:298-301, 2015.
27
Duan et al., Overview of recent HL-2A experiments, Nuc Fusion 57:102013, 2017.
28
Shirai, Barabaschi, and Kamada, Progress of JT-60SA Project: EU-JA joint efforts for assembly andfabrication of superconducting tokamak facilities and its research planning, Fusion Eng and Design 109:1701, 2016.
29
Crisantia et al., The Divertor Tokamak Test facility proposal: Physical requirements and reference design,
Nuc Materials and Energy 12:1330, 2017.
30
Song et al., Concept design of CFETR tokamak machine, IEEE Trans Plasma Sci 42:503, 2014.
31
See, for example, Stewart Prager, A reinvigorated US fusion energy program, presented to the Committee fora Strategic Plan for U.S. Burning Plasma Research, August 29, 2017.
32
See, for example, T. Carter, R. Fonck, M. Haynes, D. Maurer, D. Meade, G. Navratil, S. Prager, G. Tynan, D.
Whyte, “Perspectives on a Restructured US Fusion Energy Research Program,” presented to the Workshop on U.S.
Magnetic Fusion Research Strategic Directions, July 24, 2017.

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did not foresee how international cooperation by itself will allow the U.S. fusion researchers to maintain a world
leadership position without new facility starts within the United States.

FUSION TECHNOLOGY AND ENGINEERING SCIENCE
Many of the program contributions to burning plasma science are interrelated to advancements in fusion
technology and engineering science. The Virtual Laboratory for Technology (VLT) functions as a “virtual”
laboratory with 18 collaborating institutions within the United States, including eight universities, nine national
laboratories, and one private company.33 The VLT facilitates fusion technology and engineering science in the
United States by (1) developing the enabling technology for existing and next-step experimental devices, (2)exploring and understanding key materials and technology feasibility issues for attractive fusion power sources, and(3) conducting advanced design studies that provide integrated solutions for next-step and future fusion devices andcall attention to research opportunities in the field.34
Since the 2004 NRC Burning Plasma Assessment report,35 fusion technology advances have been driven by
ITER research needs and by next-step goals to fully enable the fusion energy system. Key contributions from the
U.S. fusion technology program are fusion fuel cycle, fusion materials, fusion materials modeling,36 fusion plasma
power handling, superconducting magnets, and liquid metals. These contributions have resulted from joint
international projects in support of ITER and from tasks directed by U.S. researchers. Examples include vacuum andgas species management,37,38 tritium fusion fuel cycle development,39 pellet injection for fueling and disruption
mitigation,40 and the manufacture of the ITER central solenoid.41 The United States has made significant
advancements in fusion materials studies, including contributing to the qualification of reduced activation ferritic
martensitic steels for the European demonstration fusion reactor,42 nanostructured43 and oxide dispersed
strengthened steels,44 all aspects of SiC/SiC technology,45 and new understanding of tungsten46 and tungsten
composites47 as fusion plasma-facing materials. Linear plasma simulators allow for long-duration study of material
33

Phil Ferguson, “Response to the NAS Committee for a Strategic Plan for U.S. Burning Plasma Research,”presented to the Committee for a Strategic Plan for U.S. Burning Plasma Research, August 29, 2017. See also
http://vlt.ornl.gov/.
34
C.C. Baker, An overview of enabling technology research in the United States, Fusion Engineering and
Design 61-62:37-45, 2002.
35
NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.
36
Wirth, Hammond, Krasheninnikov, and Maroudas, Challenges and opportunities of modeling plasma’s
surface interactions in tungsten using high-performance computing, J Nucl Mater 463:30, 2015.
37
Duckworth et al., Development and demonstration of a supercritical helium-cooled cryogenic viscouscompressor prototype for the ITER vacuum system, Adv Cryogenic Eng 57A-B:1234-1242, 2012.
38
Perevezentsev et al., Study of outgassing and removal of tritium from metallic construction materials of ITER
vacuum vessel components, Fusion Sci and Technology 72:1-16, 2017.
39
Klein, Poore, and Babineau, Development of fusion fuel cycles: Large deviations from US defense programsystems, Fusion Eng Des 1, 2015.
40
Lyttle et al., Tritium challenges and plans for ITER pellet fueling and disruption mitigation systems, Fusion
Sci and Tech 71:251, 2017.
41
Libeyre, P., Cormany, C., Dolgetta, N. et al., Starting manufacture of the ITER central solenoid, IEEE Transon Applied Superc 26:4203305, 2016.
42
Stork et al., Developing structural, high-heat flux and plasma facing materials for a near-term DEMO fusion
power plant: The EU assessment, J Nuc Materials 455:277-291, 2014.
43
Parish et al., Helium sequestration at nanoparticle-matrix interfaces in helium plus heavy ion irradiatednanostructured ferritic alloys, J. Nuc. Materials 482:21, 2017.
44
Zinkle et al., Development of next generation tempered and ODS reduced activation ferritic/martensitic steels
for fusion energy applications, Nuc Fusion 57:092005, 2017.
45
Snead et al., Silicon carbide composites as fusion power reactor structural materials, J Nuc Materials
417:330, 2011.
46
Baldwin and Doerner, Helium induced nanoscopic morphology on tungsten under fusion relevant plasma
conditions, Nuc Fusion 48:035001, 2008.
47
Garrison et al., Irradiation effects in tungsten-copper laminate composite, J Nuc Materials 481:134, 2016.

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evolution under fusion-relevant plasma flux, but they are not useful to test integrated plasma-material effects
expected in fusion divertors. In the United States, linear plasma simulators include the PISCES facility at Universityof California, San Diego,48 the Tritium Plasma Experiment at Idaho National Laboratory (INL),49 and the recently
completed Material Plasma Exposure Experiment at Oak Ridge National Laboratory.50 The STAR51 facility, part of
the Fusion Safety Program at INL, has unique experimental capabilities that have been used to develop the only
fusion safety code accepted by the French authorities for ITER licensing, the INL fusion-modified MELCOR
code.52,53
The United States has also made progress in the areas of (1) fusion nuclear systems study, leading to thedefinition of requirements for a Fusion Nuclear Science Facility54 for integrated testing of fusion components, and(2) experiments and massively parallel simulations to understand magnetohydrodynamic flows of liquid metal, selfcooled, dual-coolant, and helium-cooled lead lithium blanket concepts at the University of California, Los Angeles,
Magnetohydrodynamic PbLi Experiment facility.55 This effort is well recognized by the international fusion andmagnetohydrodynamics communities for its potential to serve a central role in U.S. and international programs onblankets and plasma-facing components.
Although there have been significant advances in U.S. capabilities since the 2004 NRC report, many
research needs for fusion technology and engineering science remain unresolved. These include fusion plasma
material interactions, fusion blanket materials, fuel cycle safety, breeding and fueling, and opportunities foradvanced materials and manufacturing guided by new high-performance computing tools.

U.S. RESEARCH AND PARTICIPATION IN INTERNATIONAL FUSION ACTIVITIES
Fusion energy research is international. The United States participates actively in Europe and Asia, andinternational scientists from around the world participate in fusion experiments and research programs within the
United States. Many advancements in all key topical areas of fusion research are published collaboratively withinternational co-authors. The International Tokamak Physics Activity (ITPA) provides an international framework
for coordinated fusion research; since 2008, the ITPA operates under the auspices of ITER. 56

U.S. Participation in Fusion Activities in Europe
The United States has made and continues to make important contributions to the world’s largest currently
operating fusion device, Joint European Tours (JET). This includes involvement in testing important auxiliary
systems relevant to ITER (e.g., the ITER-like Shattered Pellet Injector57), plasma diagnostics (e.g., Faraday cups),48

Tynan et al., Mixed material plasma-surface interactions in ITER: Recent results from the PISCES Group, in
Plasma Interaction in Controlled Fusion Devices (Benkadda, ed.), AIP Conference Proceedings 1237, pp. 78-91,
2010.
49
Shimada et al., Tritium plasma experiment upgrade and improvement of surface diagnostic capabilities at
STAR facility for enhancing tritium and nuclear PMI sciences, Fus Sci and Technology 71:310, 2017.
50
Rapp et al., The development of the material plasma exposure experiment, IEEE Trans Plasma Sci 44:3456,
2016.
51
Tynan et al., Mixed material plasma-surface interactions in ITER: Recent results from the PISCES Group, in
Plasma Interaction in Controlled Fusion Devices (Benkadda, ed.), AIP Conference Proceedings 1237, pp. 78-91,
2010.
52
Merrill et al., Modifications to the MELCOR code for application in fusion accident analyses Fusion Eng
Design 51-52:555-563, 2000.
53
Taylor et al., Updated safety analysis of ITER, Fusion Eng Design 86:619-622, 2011.
54
C.E. Kessel et al., The Fusion Nuclear Science Facility, the critical step in the pathway to fusion energy,
Fusion Science and Technology 68:225-236, 2015, doi: 10.13182/FST14-953.
55
Smolentsev et al., Review of recent MHD activities for liquid metal blankets in the US, Magnetohydyamics
53:411, 2017.
56
See https://www.iter.org/org/team/fst/itpa.
57
Baylor et al., Disruption-mitigation-technology concepts and implications for ITER, IEEE Trans Plasma Sci
38:419, 2010.

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experimental operating scenarios (e.g., involvement in developing deuterium-tritium scenarios58), and simulation
codes (e.g., TRANSP59). Additionally, simulation codes developed by U.S. scientists have been adopted byinternational partners and are now routinely used for scenario modeling within the JET program and acrossEUROfusion ITER-related activities. Since 2016, 9 of the 33 articles appearing in the International Atomic Energy
Agency (IAEA) journal Nuclear Fusion and reporting results from the JET device involved co-authors from theUnited States.
For medium-sized tokamaks (ASDEX Upgrade, Germany; TCV, Switzerland; MAST Upgrade, United
Kingdom), many bilateral collaborations exist between the United States and EU partners. Prominent recent
examples of U.S. contributions include temporarily moving diagnostic devices from U.S. facilities to EU machines
and joint experiments on multiple machines to develop understanding and robust demonstration of control schemes
and new plasma scenarios. Since 2016, about 10 percent of the articles appearing in Nuclear Fusion describing
research with these medium-sized tokamaks involved co-authors from the United States.
Another important U.S. contribution to fusion research in the EU has been the participation in the
Wendelstein 7-X stellarator project. This includes the construction and operation of five large auxiliary coils60(installed on the outside of the device to assist in precise setting of the magnetic fields at the plasma edge) and an Xray spectrometer, as well as the development of fluctuation diagnostics and a pellet injector. This work is carried out
at three U.S. national laboratories (Princeton, Oak Ridge, and Los Alamos) and three U.S. universities (Auburn
University, University of Wisconsin, Madison, and MIT), supporting Wendelstein 7-X with equipment that has been
funded, designed, and produced in the United States and with related magnetic field and plasma diagnosis andmodeling. Since 2016, more than half of the articles appearing in Nuclear Fusion describing research with theWendelstein 7-X stellarator involved co-authors from the United States.

U.S. Participation in Fusion Activities in Asia
The United States is actively playing a significant role in developing new fusion programs in Asia. Major
contributions have been made to the programs on new Asian devices since the 2004 NRC report, notably in EAST
(China), KSTAR (Republic of Korea), HL-2A (China), and J-TEXT (Japan), and a strong relationship continues
with smaller spherical tokamaks (QUEST at Q-shu University, Japan; VEST at Seoul National University, Republicof Korea; SUNIST at Tsinghua University, China). One major focus of this international partnership has been in theuse of long-pulse superconducting devices to develop steady-state plasma scenarios.61 As an example, collaborations
on EAST have made advances in plasma control and wall conditioning techniques developed collaboratively withand initially demonstrated on DIII-D. Novel computer science hardware and software infrastructure has improved
data movement, visualization, and communication and allow scientists in the United States to remotely conduct
experiments using the EAST facility.62 In July 2017, the Chinese researchers using EAST achieved a stable 101.2second steady-state high confinement plasma, setting a world record in long-pulse H-mode operation.63
Recent U.S.-Asia cooperation is also seen in the development of HL-2M under construction in China and in
the physics design of CFETR burning plasma facility under consideration in China, where the United States
provides design expertise and simulation codes.64

U.S. Participation in the International Tokamak Physics Activity

58

Budny et al., Predictions of H-mode performance in ITER, Nuc. Fusion 48:075005, 2008.
Budny, Cordey, TFTR Team, and JET Contributors, Core fusion power gain and alpha heating in JET, TFTR,
and ITER, Nuc Fusion 56:056002, 2016.
60
Lazerson et al., Error field measurement, correction and heat flux balancing on Wendelstein 7-X, Nuc Fusion
57:046026, 2017.
61
See, for example, Garofalo et al., Development of high poloidal beta, steady-state scenario with ITER-liketungsten divertor on EAST, Nuc Fusion 57:076037, 2017.
62
D.P. Schissel et al., Remote third shift EAST operation: A new paradigm, Nucl. Fusion 57:056032, 2017.
63
See https://phys.org/news/2017-07-china-artificial-sun-world-steady-state.html.
64See, for example, Chen et al., Self-consistent modeling of CFETR baseline scenarios for steady-state
operation, Plasma Phys Controlled Fusion 59:075005, 2017.
59

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REPRINTED INTERIM REPORTThe International Tokamak Physics Activity (ITPA) began operating in 2001 with urging by the UnitedStates and under the auspices of the IAEA International Fusion Research Council. Since 2008, ITPA operates under
the auspices of ITER. The ITPA provides an international framework for coordinated fusion research useful for all
fusion programs and for broad progress toward fusion energy. The United States continues to make significant
contributions to the ITPA, which coordinates the international tokamak physics research and development activities
and provides the physics basis for the ITER project. Presently, the United States chairs four of the seven ITPA
topical working groups. The United States also actively participates in multiple-facility, joint tokamak experimental
exercises. Until recently, these joint experiments used the C-Mod, NSTX-U, and DIII-D tokamaks in the UnitedStates for dedicated studies and coordinated analysis in support of international joint experiments. For example, joint
experiments coordinated among MAST, ASDEX Upgrade, and DIII-D have recently evaluated the use of resonant
magnetic field perturbations and pellet injection to suppress edge localized modes (ELMs).65 These joint
experiments are in general agreement with plasma response modeling, confirm that magnetic perturbations can limit
ELMs, and have led to a change in the ITER design to introduce ELM control systems. Since the end of Alcator CMod operation, the United States is no longer able to provide scientific support to ITER in the area of tokamak
operation and physics in fusion devices with reactor-relevant metallic walls.

International Participation in the U.S. Program
International fusion researchers from the ITER partnership also collaborate in the U.S. research effort.
International collaboration with U.S. researchers in burning plasma science involves all parts of the program,including use of experimental facilities and involvement with theory, simulation, and modeling groups. Since 2016,of those articles appearing in the IAEA journal Nuclear Fusion describing research with U.S. medium-sized
tokamaks, one-fourth involved co-authors from Europe and one-fourth involved co-authors from Asia. Half of allarticles appearing in Nuclear Fusion since 2016 reporting advancements in fusion simulation involved collaboratinginternational co-authors. In the area of fusion technology and engineering science, the EUROfusion Work Package
for Plasma Facing Components pays to use the PISCES-B facility at University of California, San Diego, helping to
identify first wall materials for ITER and future fusion energy systems. Currently, no other linear plasma facility iscapable of performing experiments with beryllium samples. One main goal of this collaboration is to study theinteraction between deuterium or helium plasmas with beryllium and tungsten surfaces. Another example is thestudy of high dose irradiation effects in a U.S.-Japan collaboration in an experiment with more than 8 years ofirradiation on the High Flux Isotope Reactor at Oak Ridge National Laboratory.

THE ROLE OF ITER IN TODAY’S U.S. BURNING PLASMA RESEARCH ACTIVITIESAs stated in the DOE Office of Science Ten-Year Perspective (2015) (p. 8), “the global magnetic fusion
research community is focused primarily on the commencement of the ‘burning plasma’ era.” This global focus isreflected in the U.S. fusion energy science research program. The three fusion research directions, “burning plasma
science: foundations,” “burning plasma science: long pulse,” and “burning plasma science: high power,” advancethe plasma science, computational science, and materials science in support of burning plasma research that will be
conducted on the ITER device. Research objectives of the DOE Ten-Year Perspective include “urgent scientificquestions—such as how to control transient events—required for ITER to meet needs of the ITER project,”
validating predictive models for “formulating ITER operational scenarios,” and understanding how to confine andcontrol long-pulse fusion plasmas as “essential expertise for U.S. scientists who may participate in research
operations on ITER and future burning plasma experiments.”66
Planning for U.S. participation in the ITER program began in 2006 by the United States Burning Plasma
Organization (USBPO) at the request of DOE/FES in response to a requirement of the Energy Policy Act of 2005.67
65
Liu et al., Comparative investigation of ELM control based on toroidal modelling of plasma response to RMP
fields, Phys Plasmas 24:056111, 2017.
66
DOE, The Office of Science’s Fusion Energy Sciences Program: A Ten-Year Perspective, Report to Congress,
Washington, D.C., December 2015.
67
U.S. Burning Plasma Organization, Planning for the U.S. Fusion Community Participation in the ITER
Program, June 2006, https://www.burningplasma.org/web/ReNeW/EPAct_final_June09.pdf.

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REPRINTED INTERIM REPORTThis plan was endorsed by the 2009 NRC Committee to Review the U.S. ITER Science Participation Planning
Process.68 The 2009 NRC report further stated (p. 2), “U.S. involvement in developing the research program for
ITER will be crucial to the realization of U.S. fusion research goals.”
The USBPO serves the U.S. fusion research community and coordinates burning plasma research throughopen membership in topical groups. Leaders of each topical group coordinate research to address priority scientificissues and provide contact to the international burning plasma research with the ITPA and with the ITER
organization. The director and deputy director of the USBPO explained to the committee69 that burning plasma
research in support of the ITER project has resulted in significant progress in many key areas, including transient
events, plasma material interactions, integrated simulations, operating scenarios, heating and current drive,
diagnostics, plasma control, energetic particles, and transport and confinement, and these advancements “have only
increased our readiness to take the burning plasma step.”
Research in support of ITER has facilitated enhanced multi-national collaborative activities (experiments
and analysis) through the ITER-sponsored ITPA topical groups. As reported earlier in this chapter, U.S. scientists
collaborate with Asian research programs with superconducting tokamaks, EAST and KSTAR. This collaboration
targets the development of long-pulse, high-performance operating scenarios with acceptable heat exhaust that are
target scenarios for ITER operation.
Additionally, because the vast majority (approximately 80 percent) of U.S. ITER construction funding
remains within the U.S. supply chain,70 participation in ITER has resulted in significant advances in U.S. domestic
industrial capabilities and capacities that would not have happened without ITER participation. For example,






The United States has proven its capacity for fabricating superconductor in bulk, producing over four
miles of cable-in-conduit superconductor for the toroidal field magnets;
The United States is fabricating a first-of-a-kind 13 m tall, 13 T central solenoid electromagnet, whichis unique worldwide and has required the development of bespoke fabrication and testing
infrastructure;
U.S. industry is developing microwave and radio-frequency transmission lines to provide
unprecedented power transfer for heating in ITER;
High-throughput cryogenic pellet fueling systems and tritium processing systems have been developedby U.S. national laboratories; andA wide array of instrumentation for harsh nuclear environments has been developed in the U.S. supply
chain.

The United States has also been a key contributor towards the approval of ITER’s license to start
construction, by providing a “pedigreed” version of the fusion-modified safety code MELCOR, developed andmaintained by the Fusion Safety Program at INL, that has been used extensively for the safety analyses presented to
the French Nuclear Regulator (Autorité de Sureté Nucléaire) as part of the Construction Authorization Request.
Of course, in addition to ITER’s role as a focus of both the international and U.S. research programs, theUnited States has committed to contributing 9.09 percent of ITER’s construction costs. According to the DOE
project execution plan for ITER,71 the United States has “made considerable progress in completing its assigned
hardware design, R&D, and fabrication work.” Final design of about two-thirds of U.S. hardware is complete, and 2of 13 in-kind hardware systems have been delivered. A total of $942 million has been obligated by the U.S. ITER
project with contracts spread across U.S. industry, universities, and national laboratories, across 44 states.72 Thetechnical leadership and contributions made by the U.S. fusion science team is and will continue to be important to
the eventual success of the ITER design, operation, diagnostics, and analyses. In addition, the U.S. financial
68

NRC, A Review of the DOE Plan for U.S. Fusion Community Participation in the ITER Program, The
National Academies Press, Washington, D.C., 2009.
69
Charles Greenfield and Amanda Hubbard, Perspectives on Burning Plasma Research, presented to theCommittee for a Strategic Plan for U.S. Burning Plasma Research, June 5, 2017.
70
Ned R. Sauthoff, Perspectives from the US ITER Project, presented to the Committee for a Strategic Plan for
U.S. Burning Plasma Research, August 29, 2017.
71
DOE, Project Execution Plan for U.S. ITER Subproject-1, DOE Project No. 14-SC-60, Office of Science,
Fusion Energy Sciences, Washington, D.C., January 2017.
72
See slides 56-59 in Ned Sauthoff’s presentation to the committee, August 29, 2017, Ref. 23.

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commitment is highly leveraged by the sharing of costs and technology with its international partners. The
performance of the United States in its ITER obligations has been very favorably assessed by the U.S. Government
Accountability Office73 and DOE assessments and quality assurance audits conducted in 2015.
As President George W. Bush announced, ITER is “the largest and most technologically sophisticatedfusion experiment in the world” and “critical to the development of fusion as a viable energy source.” Because
burning plasma research in support of ITER and in preparation for ITER experiments is a primary focus of theinternational and U.S. research programs, ITER is more than a construction project. ITER plays a central role intoday’s U.S. burning plasma research activities, and participation in the ITER project provides formal mechanisms
for U.S. scientists to take leading roles in the international effort to develop fusion energy.

73

U.S. Government Accountability Office, FUSION ENERGY: Actions Needed to Finalize Cost and Schedule
Estimates for U.S. Contributions to an International Experimental Reactor, Report to Congress, GAO-14-499,
Washington, D.C., June 2014.

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5Assessments

In this interim report, the Committee on a Strategic Plan for U.S. Burning Plasma Research makes thefollowing assessments of the importance of burning plasma research to the development of fusion energy and of thecurrent status of U.S. burning plasma research, including current and planned participation in international activities.
These seven assessments are also the summary of this interim report.
Assessment 1: Burning plasma research is essential to the development of magnetic fusion energy andcontributes to advancements in plasma science, materials science, and the nation’s industrial capacity todeliver high-technology components.
All efforts to make fusion energy require a burning plasma—an ionized gas like the Sun and stars that isheated by fusion reactions. Burning plasma research begins with understanding, measuring, and predicting thecomplex physical processes of the plasma and of the energetic particles moving within the plasma created by fusion
reactions. Next, burning plasma research includes the high-technology tools used to control, confine, and heat theplasma to very high temperature and pressure. Finally, burning plasma research embodies the applied andengineering sciences necessary to design reliable structures that surround the plasma and convert fusion energy into
useful heat and power. Burning plasma research is interdisciplinary and results in technological and scientificachievements that touch many aspects of everyday life and lead to new insights in related fields such as optics, fluid
mechanics, and astrophysics.
Although significant fusion power has been generated for short periods in the laboratory (4 MW for 4 s andup to 16 MW for shorter periods) and some processes expected in a burning plasma have been studied at thetemperatures and pressures required for fusion energy, a burning plasma, which is heated predominately by fusion
reactions, has never been created. This requires construction of a burning plasma experiment such as theInternational Thermonuclear Experimental Reactor (ITER). A burning plasma experiment will allow integrated
investigation of the burning plasma with the advanced technology magnetic fusion schemes require. Because of its
large size and complexity, constructing a burning plasma experiment leads to advancements in industrial capability,
such as for large superconducting magnets, vacuum technologies, complex cryogenic systems, ultra-precise
construction, and robotic systems to handle materials.
Assessment 2: The U.S. fusion energy science program has made leading advances in burning plasma sciencethat have substantially improved our confidence that a burning plasma experiment such as ITER will succeedin achieving its scientific mission.
Experiments conducted using research facilities in the United States have been highly productive. New
ideas to control and sustain burning plasma have been discovered, and theoretical and computational models
developed in the United States have substantially improved the ability to control plasma stability, predict plasma
confinement, and enhance fusion energy performance. The understanding of burning plasma science has advanced
significantly, including such critical topics as the transport of heat and particles by multi-scale turbulence, thebehavior of energetic particles produced by fusion reactions, and the physics of the narrow insulating layer at theplasma edge (or “pedestal”). In addition, new techniques have been developed to avoid and mitigate transient events,
which can erode plasma-facing materials. Scenarios of burning plasma operation have been developed
experimentally and explored with computational models that are expected to simultaneously satisfy the requirements
for stability, confinement, fuel purity, and compatibility with plasma-facing components. These scenarios further

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increase confidence in the burning plasma performance that can be achieved in ITER. While important avenues forfurther exploration remain, current understanding increases confidence in ITER achieving its scientific mission. The
widely recognized importance of U.S. research contributions to the field also supports the expectation that, if theUnited States continues to participate in ITER, scientists within the United States will make leading contributions tothe study of fusion energy at the power plant scale.
Assessment 3: Construction and operation of a burning plasma experiment is a critical, but not sufficient,
next step toward the realization of commercial fusion energy. In addition to a burning plasma experiment,
further research is needed to improve and fully enable the fusion power system.
A burning plasma experiment will examine for the first time many of the interconnected scientific andtechnology issues that must be addressed to produce magnetic fusion energy. Among these are the experimental
validation of theoretical predictions related to plasma stability, plasma heating, transport of plasma heat andparticles, alpha particle physics from fusion reactions, and disruption avoidance for tokamaks in substantially
unexplored regimes of magnetic confinement. Equally important are gains in fusion engineering science including
large-scale superconducting magnet technology, progress toward understanding fusion blanket science, tritium
science and management, remote handling of materials and components, and large-scale systems integration. As aburning plasma experiment, ITER is a critical step along the path to advance the science and technology of a fusion
power source. Still, ITER is a fusion research facility and a long way from being a system for commercial power. In
a commercial system, economics requires the thermal power to increase about seven-fold. Continuous operation
requires efficient coupling of radio waves into the plasma to sustain the plasma current. Challenging plasma-wall
problems need inventive solutions in order to safely handle the flux of energetic neutrons on the inner wall and theescaping heat from the plasma that is directed onto the plates of a protective divertor. The self-consistent production
and safe handling of tritium will not be fully addressed in ITER but must be solved for commercial fusion power.
Lastly, the expected gains in engineering and economics that might accrue from technology and materials
innovations, like the newly developed rare-earth, high-temperature superconductors, need to be investigated;
however, these innovations will only impact fusion facilities built beyond ITER. The overall picture is that a burning
plasma experiment, such as ITER, will lead to major gains along the path to fusion energy while other fusion energy
experiments will need to address remaining science and technology challenges and demonstrate innovative solutions
that lead to a reduced size, lower cost, full-scale power source.
Assessment 4: Although our international partners have national strategic plans leading to a fusion energy
demonstration device, the United States does not.
Since the National Research Council’s (NRC’s) study in 2004,1 strategic plans leading to a fusion energy
demonstration have been developed by many of our international partners, all with high-level governmental supportand in some cases even adopted federal legislation. These strategies all recognize that the burning plasma regime
provided by ITER is the most expedient way to demonstrate controlled fusion on commercial scale, but importantly,
also elucidate the accompanying research and technology programs needed to progress beyond ITER to acommercial fusion reactor. Such strategic planning guides the national research and innovation programs, helps toengage industrial partners and sets the national priorities of our partners, enabling them to develop key areas ofunique expertise. The absence of such a nationally endorsed strategic plan for delivery of fusion energy in the
United States inhibits the long-term planning of all participants in the fusion endeavor in the United States, fromuniversities, to national laboratories, to industrial partners. Without a long-term plan, the United States risks being
overtaken as our partners advance the science and technology required to deliver fusion energy. Conversely, theadoption of such a plan has the potential to support strategic funding decisions and priorities within the national
program and help foster innovation to drive towards commercially viable fusion reactor designs.
Assessment 5: Recent closures of domestic experimental facilities without new starts, as well as a reduction offusion technology efforts, threaten the health of the field in the United States.

1

National Research Council (NRC), Burning Plasma: Bringing a Star to Earth, The National Academies Press,
Washington, D.C., 2004.

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REPRINTED INTERIM REPORTAs reported by the NRC Burning Plasma Committee in 2004,2 many of the scientific and technical issues ofimportance to the long-range development of fusion are best addressed by research facilities having size andcomplexity much smaller than that needed for a burning plasma experiment. A long-term strategy for fusion energy
benefits from a domestic effort in parallel with the ITER project focused on developing the scientific base forpromising fusion reactor concepts and technologies.
However, during the past decade, various programmatic decisions have closed domestic experimental
facilities without opportunities for new starts and without compensating programs internationally. In 2005, thebudget for U.S. fusion technology efforts was sharply reduced. In 2013, the Department of Energy’s Office of
Fusion Energy Sciences implemented an overall reduction in the domestic program while making only a modest
increase in funding for scientific collaborations on non-U.S. experimental facilities. Currently, only one mid-scalefusion experiment is operating in the United States. Mid-scale experimental facilities can attract talent to the field,
provide broad scientific and engineering opportunities, and test innovations that could improve the fusion energy
concept and strengthen U.S. expertise in fusion science and technology.
Assessment 6: Any strategy to develop magnetic fusion energy requires study of a burning plasma. The only
existing project to create a burning plasma at the scale of a power plant is ITER, which is a major componentof the U.S. fusion energy program. As an ITER partner, the United States benefits from the long-recognizedvalue of international cooperation to combine the scientific and engineering expertise, industrial capacity,and financial resources necessary for such an inherently large project. A decision by the United States towithdraw from the ITER project as the primary experimental burning plasma component within a balanced
long-term strategic plan for fusion energy could isolate U.S. fusion scientists from the international effort andwould require the United States to develop a new approach to study a burning plasma.
Past studies of magnetic fusion energy research recommended U.S. entrance into international partnerships
as the most cost-effective approach to undertake large fusion energy experiments. These studies include
Cooperation and Competition on the Path to Fusion Energy,3 Pacing the U.S. Magnetic Fusion Program,4 the 1995
report of the President’s Committee of Advisors on Science and Technology Panel on U.S. Fusion R&D Programs,5and Realizing the Promise of Fusion Energy.6 After considering various options for a burning plasma experiment,
the 2004 NRC Burning Plasma Assessment Committee7 recommended that the United States should participate in
ITER. But, if the United States were not to participate in ITER, the committee also recommended the pursuit ofinternational partnership in an alternate burning plasma experiment. A burning plasma experiment at the scale of apower plant is necessarily a large facility and integrates multiple advanced technologies. At the present time, nocountry has the combination of scientific and engineering expertise, industrial capacity, and long-term national
commitment to undertake this critical task alone.
While previous studies concluded that fusion energy research substantially benefits from international
cooperation, they also described a potential for failure if international partners were unable to meet theircommitments. The NRC’s report A Review of the DOE Plan for U.S. Fusion Community Participation in the ITER
Program8 recommended that steps should be taken to “seek greater funding stability for the international ITER
project to ensure that the United States remains able to influence the developing ITER research program, tocapitalize on research at ITER to help achieve U.S. fusion energy goals, to participate in obtaining importantscientific results on burning plasmas from ITER, and to be an effective participant in and beneficiary of futureinternational scientific collaborations.”
The committee has reviewed the recommendations from these past studies in the context of the existing
ITER partnership, the assessments of U.S. burning plasma research listed above, and the benefits international
2

Ibid.
National Research Council (NRC), Cooperation and Competition on the Path to Fusion Energy: A Report,
National Academy Press, 1984.
4
NRC, Pacing the U.S. Magnetic Fusion Program, National Academy Press, Washington, D.C., 1989.
5
President’s Committee of Advisors on Science and Technology, The U.S. Program of Fusion Research andDevelopment, Washington, D.C., July 11, 1995.
6
U.S. Department of Energy, Realizing the Promise of Fusion Energy: Final Report of the Task Force on
Fusion Energy, Secretary of Energy Advisory Board, Washington, D.C., August 9, 1999.
7
NRC, Burning Plasma: Bringing a Star to Earth, The National Academies Press, Washington, D.C., 2004.
8
NRC, A Review of the DOE Plan for U.S. Fusion Community Participation in the ITER Program, The
National Academies Press, Washington, D.C., 2009.
3

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partnership brings to large multi-year endeavors at the frontier. Based on this review, the committee concludes that
the United States benefits from partnership in ITER as the primary experimental burning plasma component within
its own long-term strategic plan for fusion energy. On the other hand, a decision by the United States to withdraw
from the ITER project would require a new approach to study a burning plasma. Because there is currently nomature burning plasma experiment as an alternative to ITER, the design, construction, and licensing of such analternative to ITER would require significant development by the U.S. program, as well as a new approach to avoid
isolation from the international fusion energy research effort.
The committee’s final report will provide greater detail and analysis of the options for a long-term strategicplan for a national program of burning plasma science and technology research, including developing various
supporting capabilities and participating in international activities. Strategic guidance for scenarios where the UnitedStates both is and is not a participant in ITER will be described.
Work for the final report is at an early stage. Nevertheless, based on the input received by the committee
and the committee’s assessments, if the United States seeks to continue its pursuit for abundant fusion power, thedevelopment of a national strategic plan for fusion energy that spans several decades is necessary. Therefore, thecommittee makes the following final assessment that will guide the strategies for both scenarios in the final report.
Assessment 7: If the United States wishes to maintain scientific and technical leadership in this field, thecommittee concludes that the United States needs to develop its own long-term strategic plan for fusionenergy.
In the development of the final report, the committee views the following elements as important to its
guidance on a long-term strategic plan:

Continued progress towards the construction and operation of a burning plasma experiment leading to
the study of burning plasma,
Research beyond what is done in a burning plasma experiment to improve and fully enable commercial
fusion power,
Innovation in fusion science and technology targeted to improve the fusion power system as acommercial energy source, andA mission for fusion energy research that engages the participation of universities, national
laboratories, and industry in the realization of commercial fusion power for the nation.

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6
Toward Completion of the Final Report

Having completed its assessment of the status and importance of U.S. burning plasma research, thecommittee is now carrying out the detailed analyses of the many elements required to guide the nation’s long-term
strategic plan for fusion energy development. These analyses will be informed by input from the second community
workshop on strategic directions for U.S. magnetic fusion research to be held at the University of Texas, Austin,
December 11-15, 2017, and by several site visits. Additionally, a subcommittee of the Fusion Energy Sciences
Advisory Committee (FESAC) to the U.S. Department of Energy Office of Science is expected to complete its
report shortly identifying “the most promising transformative enabling capabilities for the United States to pursuethat could promote efficient advance toward fusion energy.” This new FESAC report will also inform U.S. strategies
to improve the fusion power system. The committee anticipates that its final report will present strategies thatincorporate continued progress toward a burning plasma experiment, include a major focus on innovation, include
provisions for regular review in order to accommodate scientific and technological breakthroughs, and be built uponrecent advances in burning plasma science, fusion nuclear science, and the international effort. To the extent
possible, the final report will include considerations of the health of fusion research sectors within the United States,
the role of international collaboration in the pursuit of national fusion energy goals, the capability and prospects ofprivate-sector ventures to advance fusion energy concepts and technologies, the impact of science and technology
innovations, and the design of research strategies that may shorten the time and reduce the cost required to develop
commercial fusion energy.

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REPRINTED INTERIM REPORTAppendixes

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REPRINTED INTERIM REPORTAWhat Is Magnetic Fusion?

While it has long been known that it is nuclear fusion that makes the Sun shine, the first concerted attempts
to harness fusion power on Earth began in the 1950s, first in secret but collaboratively among many nations by 1958.
These first efforts, and the fusion research described in this interim report, employed strong magnetic fields toconfine the hot gases that produce fusion power. By the 1960s, the invention of the laser led to a different approachin which lasers quickly heat a tiny quantity of fuel that explodes as it burns.1 This report deals only with magnetic
fusion, which has had the best performance to date, leading to governmental discussions in the 1990s on how toadvance magnetic fusion energy research as a world-wide endeavor—what is now the International Thermonuclear
Experimental Reactor (ITER) project. Several books describe this history.2,3,4
A magnetic fusion reactor can be thought of as a miniature Sun confined inside a vessel that can be highly
evacuated. A strong magnetic field confines the high-pressure plasma and limits contact between the surrounding
vessel and the high-temperature plasma undergoing fusion reactions. The first fuel will probably be a mixture of
deuterium (D), a form of hydrogen in all water, and another form of hydrogen called tritium (T) that would bemanufactured inside the reactor. The energy potential in the tiny amount of deuterium in a gallon of water isequivalent to 300 gallons of gasoline. It is this abundance of fusion fuel, together with environmental advantages,that has inspired governments to support fusion research over many decades. D-T fuel produces harmless helium,
together with neutrons that can make the reactor vessel radioactive, but with much less chance for danger to the
public than fission reactors, according to studies reported in Chapter 15 of The Fusion Quest. This interim reportdiscusses only fusion using D-T fuel, which is the focus of the world-wide research program. Magnetic fusionenergy using either deuterium (D-D) or deuterium and helium-3 (D-3He) fuel is more challenging due torequirements for higher temperature, reduced impurity concentration, and improved confinement.5
The challenge has been that producing fusion on Earth requires temperatures even hotter than stars and in
the range between 100 and 200 million degrees. Gases this hot become ionized, consisting of a “plasma” of free ionsand electrons, like the gases conducting electricity in a neon sign but requiring 10,000 times higher temperature.
Magnetic fields are needed to confine hot, high-pressure plasmas by way of electric currents inside the ionizedplasma. Many arrangements of magnets to confine a hot plasma have been tested. The most successful, and the one
employed in ITER, is the tokamak configuration, originally developed in Russia and further explored and improved
upon by research in the United States and elsewhere.

The tokamak is a descendant of the linear “pinch” known since the 1930s. In a pinch, a current flowing
through a plasma column confines itself by its own magnetic fields produced by the current. Bending the current
column into a circle prevents leakage out the ends, and doing this inside a “toroidal” or doughnut-shaped vessel
keeps the air out. Coils above and below the toroidal vessel provide the magnetic force that bends the column into a
1
For more information on inertial fusion energy, see National Research Council, An Assessment of theProspects for Inertial Fusion Energy, The National Academies Press, Washington, D.C., 2013.
2
J.L. Bromberg, Fusion, MIT Press, Cambridge, Mass., 1982.
3
T.A. Heppenheimer, The Man-Made Sun, Little-Brown, Boston, Mass., 1984.
4
T.K. Fowler, The Fusion Quest, Johns Hopkins Press, Baltimore, Md., 1997.
5
P.E. Stott, The feasibility of using D–3He and D–D fusion fuels, Plasma Phys Contr F 47:1305, 2005.

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REPRINTED INTERIM REPORTFIGURE A.1 A schematic of a magnetic fusion power plant showing (not to scale) the three parts: a hot burning
plasma undergoing fusion reactions, a lithium “blanket” to capture fusion neutrons, and a heat-exchanger systemwith a turbine-driven electrical generator. SOURCE: C.L. Smith and S. Cowley, The path to fusion power, Phil.
Trans. R. Soc. A 368:1091-1108, 2010.
circle. Other “toroidal field coils” wound on the vessel itself add a stabilizing twist to magnetic field lines inside thecolumn. Thus, the tokamak has three sources of magnetic field: the pinch current that mainly confines the pressure;the “poloidal” coils that bend plasma current into a circle; and the strong “toroidal field coils” that twist the current
into a highly stable confined plasma.
Fusion performance is measured by the pressure of the plasma, P, and the timescale for plasma energy
escape, τE. The fusion power density produced from the fusion of deuterium and tritium (D-T) is equal to 0.08 P2
megawatts per cubic meter (MW m-3) when P is expressed in atmospheres. The record volume-averaged plasmapressure for magnetic fusion is 2.0 atmospheres and was set in October 2016 in the Alcator C-Mod device at theMassachusetts Institute of Technology. The plasma pressure expected in ITER is 2.6 atmospheres resulting in a peakfusion power density exceeding 0.5 MW m-3. Commercial fusion energy systems would need to have plasmapressures between 3 and 8 atmospheres. The energy escape time, τE, determines whether or not the plasma is selfsustaining or whether external power must be injected to keep the plasma hot and at high pressure. ITER is designed
to produce τE ~ 3.7 seconds, and the product of the average pressure and τE is PτE ~ 10 atm⋅sec. If the electron andion pressures of the plasma are equal, the plasma becomes a “burning plasma” when the product PτE is greater thanabout 8 atm⋅sec. This is when the energetic alpha particles generated from fusion reactions in the plasma are able tobalance the energy escaping from the plasma. The highest previous levels of plasma confinement product wereachieved in tokamak experiments conducted in the 1990s: The Tokamak Fusion Test Reactor6 achieved 0.3 atm⋅sec,
the Joint European Tours7 reached 0.7 atm⋅sec, JT-608 reached 0.65, and DIII-D reached a confinement parameter ofPτE ~ 0.5 atm⋅sec.9
Practical problems include how to get heat out of this circular device, how to prevent neutron damage to themagnet coils, and how to respond if, despite all, the strong current ring tries to short-circuit to the wall (called a“disruption”). What makes it worth dealing with these difficult issues is the remarkable fact that plasmas inside
tokamaks can adjust themselves to reduce leakage of heat across the magnetic field. This “H-mode,” or “high-6

Hawryluk et al., Results from deuterium-tritium tokamak confinement experiments, Rev. Mod. Phys. 70:537,

1998.
7

Keilhacker et al., High fusion performance from deuterium-tritium plasmas in JET, Nuc Fusion 39:209, 1999.
H. Kishimoto et al., Advanced tokamak research on JT-60, Nuc Fusion 45:986, 2005.
9
Lazarus et al., Higher fusion power gain with profile control in DIII-D tokamak plasmas, Nuc Fusion 37:7-12,
1997.
8

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REPRINTED INTERIM REPORT
confinement mode,” of tokamak operation, was discovered experimentally in the 1980s10,11 and has been widelyreproduced even as essential aspects of it remain enigmatic. ITER’s baseline operating scenario is an H-mode
plasma. Critical research efforts in the U.S. and abroad are focused both on ensuring that the ITER plasmas willattain and maintain H-mode performance and on developing alternative operating scenarios for ITER, which do not
rely upon uncertain H-mode physics to attain the energy confinement that is required to create a burning plasma.
Whether a tokamak in the image of ITER will be the best path to a commercial reactor is much less certain,
hence the need for continuing innovation to explore other paths. One such path is the stellerator being pursued inGermany and Japan. The stellarator is also a toroidal magnetic system but one not requiring the pinch current—nor
the associated cost of maintaining it—as in tokamak reactors.
In addition to toroidal magnet configurations, a number of linear magnet configurations have been studied,all of which employ external power to create a closed magnetic field configuration of the plasma inside the linear
magnets. Additionally, the tandem mirror configuration uses neutral beam injection and electron cyclotron
resonance heating to modify electrostatic potentials and reduce plasma leakage out the ends. The only linear device
large enough to compete with tokamak performance was the superconducting Mirror Fusion Test Facility thatcompleted construction at the Lawrence Livermore National Laboratory in February 1986, only to be shut down
before operating because of declining magnetic fusion budgets.
Whatever the final magnet shape, the fact that magnets might confine a plasma producing fusion energy on
Earth completes a long journey, beginning with Michael Faraday’s invention of the magnetic dynamo in 1831 andending with Einstein’s discovery that mass becomes energy, very soon leading to speculations about nuclear fusion
long before fission was discovered. It was Faraday’s discovery that prompted Maxwell to create the theory of lightthat eventually posed the puzzle that led to Einstein’s E = mc2.

10

Wagner et al., Regime of improved confinement and high beta in neutral-beam-heated divertor discharges of
the ASDEX Tokamak, Phys Rev Lett 49:1408, 1982.
11
Wagner et al., Development of an edge transport barrier at the H-mode transition of ASDEX, Phys Rev Lett
53:1453, 1984.

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B
Statement of Task
A committee of the National Academies of Sciences, Engineering, and Medicine will be formed to study
the state and potential of magnetic confinement-based fusion research in the United States and provide guidance on
a long-term strategy for the field. The study will focus on research that supports understanding the magneticallyconfined burning plasma state but will take a broad view beyond plasma confinement science, and as such consider
capabilities such as simulation and materials. Specifically, the committee will prepare an interim report that will:
3.
4.

Describe and assess the current status of U.S. research that supports burning plasma science, including
current and planned participation in international activities, and describe international research
activities broadly.
Assess the importance of U.S. burning plasma research to the development of fusion energy as well as
to plasma science and other science and engineering disciplines.

The committee will also prepare a final report, building on the interim report, which will:
3.
4.

Consider the scientific and engineering challenges and opportunities associated with advancing
magnetic confinement fusion as an energy source, including the scientific and technical developments
since the 2004 NAS1 study on burning plasma research.
In two separate scenarios in which, after 2018, (1) the United States is a partner in ITER, and (2) the
United States is not a partner in ITER: provide guidance on a long-term strategic plan (covering thenext several decades) for a national program of burning plasma science and technology research which
includes supporting capabilities and which may include participation in international activities, given
the U.S. strategic interest in realizing economical fusion energy in the long term.

In doing the above, the committee will consider the priorities for the next ten years developed by thecommunity and FES that were recently reported to Congress. The committee will also consider the current level ofparticipation by U.S. scientists in international activities as well as what role international collaboration should playover the next 20 years. The committee will also consider the health of the domestic fusion research sectors(universities, national laboratories, and industry). Elements of any strategic plan for U.S. burning plasma researchshould ensure that the United States maintains a leadership role in this field. The committee may assume that
economical fusion energy within the next several decades is a U.S. strategic interest. The committee may take into
account how unanticipated events or innovations may necessitate mid-course re-directions. The committee will use
the prior work of the Academies as well as that of FESAC and the domestic and foreign communities in its
deliberations. The committee is not to compare fusion as an energy source against other current or potential energy
sources. The committee will consider the budget implications of its guidance but will not make recommendations
about the budget for burning plasma research itself. The committee will only consider magnetically confinedburning plasma research as within its purview. The committee may make recommendations or offer comments onorganizational structure and program balance, with accompanying supporting discussion of the evidentiary bases, as
appropriate.
1

Effective July 1, 2015, the institution is called the National Academies of Sciences, Engineering, andMedicine. References in this report to the National Research Council (NRC) are used in a historical context to referto activities before July 1.

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REPRINTED INTERIM REPORTCAgendas from Committee Meetings

MEETING 1: JUNE 5-6, 2017
Keck Center of the National Academies
Washington, D.C
June 5, 2017
CLOSED SESSION
8:00 a.m.
9:00
12:00 p.m.
1:00

Breakfast
Discussion
Lunch
Discussion

OPEN SESSION
1:45
2:00
3:00
3:15
4:00
5:00
5:30

Reconvene
Perspective from DOE Fusion Energy Sciences, Ed Synakowski, DOE FESBreakPerspectives from Capitol Hill, Adam Rosenberg and Emily Domenech, House Science, Space,and Technology
Perspectives from the U.S. Burning Plasma Organization, Chuck Greenfield, General Atomics,
and Amanda Hubbard, MITOpen public comments
Break

CLOSED SESSION
6:30
8:30

Committee dinner
Adjourn for the day

June 6, 2017
CLOSED SESSION
This day is held entirely in closed session.

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REPRINTED INTERIM REPORTMEETING 2: AUGUST 29-31, 2017
Beckman Center of the National Academies
Irvine, California

August 29, 2017
CLOSED SESSION
8:00 a.m.
9:00

BreakfastCommittee discussion

OPEN SESSION
9:30
10:30
11:00
12:00 p.m.
1:00
2:00
3:00
3:30
4:30

Perspectives from the U.S. ITER Project, Ned Sauthoff, Oak Ridge National Laboratory
Perspectives from the ITER Organization, Bernard Bigot, Director General
Break
Perspective on Fusion Energy Strategy, Stewart Prager, Princeton University
Lunch
Perspective on Fusion Energy Strategy, Tony Taylor, General Atomics
Perspectives from University Fusion Associates,
David Maurer, Auburn University
Break
Perspectives from the Virtual Laboratory for Technology, Phil Ferguson, Oak Ridge National Lab
Public comments

CLOSED SESSION
5:00

Discussion

OPEN SESSION
6:30
8:30

DinnerAdjourn for the day

August 30, 2017
CLOSED SESSION
8:30 a.m.
6:00 p.m.

Committee discussion
Adjourn for the day

August 31, 2017
CLOSED SESSION
8:30 a.m.
2:00 p.m.

Committee discussion
Adjourn

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REPRINTED INTERIM REPORTDPrevious Studies of Magnetic Fusion Energy and Strategies for Fusion Energy
Development Consulted by the Committee, 1984-2017

NRC (National Research Council). 1984. Cooperation and Competition on the Path to Fusion Energy: A Report.
National Academy Press, Washington, D.C.
DOE (U.S. Department of Energy). 1985. Magnetic Fusion Program Plan. DOE/ER-0214. Washington, D.C.
February.
DOE Energy Research Advisory Board. 1986. Report of the Technical Panel on Magnetic Fusion. Washington, D.C.
November.
NRC. 1989. Pacing the U.S. Magnetic Fusion Program. National Academy Press, Washington, D.C.
DOE FEAC (Fusion Energy Advisory Committee). 1990. Final Report. Washington, D.C. September.
DOE FEAC. 1992. Report on Program Strategy for U.S. Magnetic Fusion Energy Research. DOE\ER-0572T.
Washington, D.C. September.
PCAST (President’s Committee of Advisors on Science and Technology). 1995. The U.S. Program of Fusion
Research and Development. Washington, D.C. July 11.
DOE FEAC. 1996. A Restructured Fusion Energy Sciences Program. Washington, D.C., January 27.
DOE FESAC (Fusion Energy Sciences Advisory Committee). 1997. Review of the International Thermonuclear
Experimental Reactor (ITER) Detailed Design Report. Washington, D.C. April 18.
DOE FESAC. 1998. Recommendations on the Nature and Level of U.S. Participation in the International
Thermonuclear Experimental Reactor Extension of the Engineering Design Activities. DOE/ER-0720.
Washington, D.C. January.
DOE FESAC. 1999. Opportunities in the Fusion Energy Sciences Program. Washington, D.C. June.
PCAST. 1999. Powerful Partnerships: The Federal Role in International Cooperation on Energy Innovation.
Washington, D.C. June.
DOE SEAB (Secretary of Energy Advisory Board). 1999. Realizing the Promise of Fusion Energy: Final Report of
the Task Force on Fusion Energy. Washington, D.C. August 9.
DOE SEAB. 1999. Report of the FESAC Panel on Priorities and Balance. Washington, D.C. September 13.
DOE FESAC. 2000. Report of the Integrated Program Planning Activity for the DOE Fusion Energy Sciences
Program. DOE/SC-0028. Washington, D.C. September.
NRC. 2001. An Assessment of the Department of Energy’s Office of Fusion Energy Sciences Program. National
Academy Press, Washington, D.C.
DOE FESAC. 2001. Review of the Fusion Theory and Computing Program. Washington, D.C. August.
DOE FESAC. 2001. Review of Burning Plasma Physics. DOE/SC-0041. Washington, D.C. September.
Bangerter, R., G. Navratil, and N. Sauthoff. 2003. 2002 Fusion Summer Study Report. Report from the 2002 Fusion
Summer Study, Snowmass, Colorado, July 8-19, 2002. June.
DOE FESAC. 2002. Report of the Fusion Energy Sciences Advisory Committee Burning Plasma Strategy Panel: A
Burning Plasma Program Strategy to Advance Fusion Energy. Washington, D.C. September.
DOE FESAC. 2003. Report of the Fusion Energy Sciences Advisory Committee Fusion Development Path Panel: A
Plan for the Development of Fusion Energy. Washington, D.C. March.
NRC. 2004. Burning Plasma: Bringing a Star to Earth. The National Academies Press, Washington, D.C.
DOE FESAC. 2005. Scientific Challenges, Opportunities and Priorities for the U.S. Fusion Energy Sciences
Program. Washington, D.C. April.

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REPRINTED INTERIM REPORTU.S. Burning Plasma Organization, Planning for the U.S. Fusion Community Participation in the ITER Program,
June 7, 2006. https://www.burningplasma.org/web/ReNeW/EPAct_final_June09.pdf.
DOE FESAC. 2007. Priorities, Gaps and Opportunities: Towards a Long-Range Strategic Plan for Magnetic
Fusion Energy. Washington, D.C. October.
NRC. 2007. Plasma Science: Advancing Knowledge in the National Interest. The National Academies Press,
Washington, D.C.
NRC. 2009. A Review of the DOE Plan for U.S. Fusion Community Participation in the ITER Program. The
National Academies Press, Washington, D.C.
DOE. 2009. Scientific Grand Challenges: Fusion Energy Science and the Role of Computing at the Extreme Scale.
Report from the DOE Workshop held March 18-20, 2009. Washington, D.C.
DOE. 2009. Research Needs for Magnetic Fusion Energy Sciences. Report from the DOE Workshop held June 8-12,
2009. Washington, D.C.
PCAST. 2010. Report to the President on Accelerating the Pace of Change in Energy Technologies Through an
Integrated Federal Energy Policy. Washington, D.C. November.
DOE FESAC. 2012. Materials Science and Technology Research Opportunities Now and in the ITER Era: A
Focused Vision on Compelling Fusion Nuclear Science Challenges. Washington, D.C. February.
DOE FESAC. 2012. Opportunities for and Modes of International Collaboration in Fusion Energy Sciences
Research during the ITER Era. Washington, D.C. February.
European Fusion Development Agreement. 2012. Fusion Electricity: A Roadmap to the Realization of Fusion
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DOE FESAC. 2013. Report of the FESAC Subcommittee on the Priorities of the Magnetic Fusion Energy Science
Program. Washington, D.C. February 10.
DOE FESAC. 2013. Report of the FESAC Subcommittee on the Prioritization of Proposed Scientific User Facilities
for the Office of Science. Washington, D.C. March 21.
DOE FESAC. 2014. Report on Strategic Planning: Priorities Assessment and Budget Scenarios. Washington, D.C.
December.
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Plasma Materials Interactions. Report from the DOE Workshop held May 4-7, 2015. Washington, D.C.
DOE. 2015. Integrated Simulations for Magnetic Fusion Energy Sciences. Report from the DOE Workshop held
June 2-4, 2015. Washington, D.C.
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Washington, D.C. December.
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DOE. 2017. Project Execution Plan for U.S. ITER Subproject-1. DOE Project No. 14-SC-60. Office of Science,
Fusion Energy Sciences, Washington, D.C. January.
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Federici, G., et al. 2017. European DEMO design strategy and consequences for materials. Nucl. Fusion 57:092002.

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Biographies of Committee Members
MICHAEL MAUEL, Co-Chair, is a professor of applied physics at Columbia University. He received his
B.S., M.S., and Sc.D. at MIT. While at MIT, he was awarded the Fortesque Fellowship from the IEEEand the Ernst A. Guillemin Thesis Award from MIT. Before joining Columbia in 1985, Dr. Mauelconducted post-doctoral research at MIT and conducted high-power electron cyclotron heating
experiments at the Tara Tandem Mirror. His fields of interest include advanced tokamak operating
regimes, feedback techniques to control tokamak instabilities, nonlinear turbulent transport in magnetizedplasma including energetic particle modes, and the relationship between laboratory and space plasma
physics. In 1995, he was elected a fellow for the American Physical Society. From 2000-2006 he waschair of the Department of Applied Physics and Applied Mathematics at Columbia. In 2006, he was a
Jefferson Science Fellow for the U.S. Department of State. Dr. Mauel has served as a member of several
committees in the American Physical Society and served as chair of the APS Division of Plasma Physics
from 2002-2003. He was president of the University Fusion Association from 1997-1998, co-chair of the1999 Fusion Summer Study in Snowmass, chair of the U.S. ITER Forum in 2003, chair of the U.S.
Burning Plasma Council from 2010-2013, and chair of the National Academies Plasma Science
Committee from 2012-2015. He served on several Fusion Energy Sciences Advisory Committee(FESAC) activities, including FESAC Office of Fusion Energy Committee of Visitors (2003-2004),
FESAC Fusion Major Facilities Panel (2012-2013), FESAC Fusion Priorities Panel (2003-2004 and2012-2013). He also served as chair of the physics advisory committees for the National Spherical
Tokamak Experiment (NSTX) at the Princeton Plasma Physics Laboratory and the Alcator C-Mod
experiment at MIT. Dr. Mauel received the Rose Award for Excellence in Fusion Engineering in 2000,
the Teacher of the Year award from Columbia University's School of Engineering and Applied Science,and Certificates of Appreciation from the U.S. Department of Energy (1989) and the U.S. Department ofState (2007). Since 2016, Dr. Mauel serves as editor-in-chief of Physics of Plasmas.
MELVYN SHOCHET [NAS], Co-Chair, is Kersten Distinguished Service Professor of Physics at the
University of Chicago. Before joining the Enrico Fermi Institute at the University of Chicago in 1972, hereceived his PhD from Princeton University and his B.A. from the University of Pennsylvania. His
research involves interactions between elementary particles at the highest manmade energies. He is afounding member of the Collider Detector at Fermilab (CDF) collaboration and served as thecollaboration’s spokesperson from 1988-1995, including the period when nature’s heaviest constituent,
the top quark, was discovered. For the past 15 years, he has been a member of the ATLAS collaboration
at CERN, which discovered the Higgs boson in 2012. He was a member of the HEPAP Particle Physics
Project Prioritization Panel (P5), and from 2005-2011, he served as chair of HEPAP. He also served on
the BPA’s Committee on Elementary Particle Physics from 1995-1998. He is a fellow of the American
Physical Society, the American Association for the Advancement of Science, the American Academy ofArts and Sciences, and a member of the National Academy of Sciences.
CHRISTINA BACK is an experimental physicist with expertise in the study of radiation in high energy
density plasmas, and the development of novel materials for fusion and fission. Currently, she is the Vice
President of Nuclear Technologies and Materials at General Atomics and leads a group developing highdensity uranium fuels and advanced fuel cladding materials. She received her B. S. in Physics from Yalein 1984 and earned her Ph.D. in plasma physics from the University of Florida in 1989. After a 2 year
postdoc with the CNRS at the Ecole Polytechnique in France, she spent 13 years at Lawrence Livermore
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National Laboratory in the Inertial Confinement Fusion and High Energy Density Science programs,
specializing in radiation transport and spectroscopy. In 2005, she moved to General Atomics where she
was worked on target production coordination, development of novel radiation sources, and developmentof new fuel materials for advanced nuclear reactor. She established a dedicated laboratory for researchfabricating and characterizing new fission fuel prototypes, especially those for gas-cooled hightemperature reactors. She has served on many American Physics Society (APS) committees and has been
elected as a APS General Councillor. Other professional service includes serving on the National
Research Council (NRC) Board of Physics and Astronomy Plasma Committee, and as member of the
NRC committee to Review the Quality of Science and Engineering Research at the DOE’s National
Security Laboratories Phase II (2012). Dr. Back is a Fellow of the American Physical Society.
RICCARDO BETTI is a professor of physics and mechanical engineering and of physics and astronomy,
director of the Fusion Science Center of Extreme States of Matter and Fast Ignition, and a scientist at theLaboratory for Laser Energetics at the University of Rochester. His primary expertise is in the theory ofhigh-temperatures plasmas. Dr. Betti is a member of the interdisciplinary High Energy Density Plasma
program at Rochester’s Laboratory for Laser Energetics. Dr. Betti is a member of DOE’s Fusion Energy
Sciences Advisory Committee and was the vice chair of a recent DOE review of inertial fusion energy, as
well as many other review panels. Dr. Betti is a fellow of the American Physical Society. He received his
Ph.D. from MIT in 1992 in nuclear engineering.
IAN CHAPMAN is the CEO of the UK Atomic Energy Authority and Head of the CCFE. His primaryresearch interests are in understanding and controlling macroscopic instabilities in fusion plasmas. Ian
Chapman was previously the head of tokamak science and led the stability program within tokamak
science. He has also held a number of international roles in fusion. He was a task force leader for JET
from 2012 to 2014. He was appointed a member of the program advisory committee for US experiment
NSTX-U in 2013. He has chaired international working groups for ITER and led work packages within
the EU fusion program. He received his Ph.D. in Plasma Physics from the Imperial College and M.Sci. in
Mathematics and Physics from University of Durham.
CARY FOREST is a professor in the Physics Department at the University of Wisconsin Madison. He
obtained his Ph.D. in Astrophysical Science-Plasma Physics from Princeton University in 1992. His
research interests focus on understanding how electrical currents and magnetic fields are generated infusion plasmas and in turbulent flows of liquid metals, with applications to astrophysical and terrestrial
plasmas, basic plasmas, and fusion science. He spent five years working at General Atomics as ascientist, where his work focused on studies of plasma resistivity, non-inductive current drive, rf heatingof plasmas and MHD instabilities in tokamak plasmas. He has served as director of the NSF Physics
Frontier Center for Magnetic Self-Organization. He served as chair of the APS Division of Plasma
Physics. He is a fellow of the American Physical Society. He has served as chair of the National
Academies’ Plasma Science Committee (2003-2006) and as a member of the Committee to Review a Plan
Prepared by the U.S. Burning Plasma Organization for U.S. Fusion Community Participation in the ITER
Program.
T. KENNETH FOWLER [NAS] is Professor Emeritus in the Department of Nuclear Engineering,
University of California, Berkeley. Dr. Fowler received his BE in electrical engineering from Vanderbilt
University in 1953, MS in physics from Vanderbilt in 1955, and Ph. D. in theoretical physics from the
University of Wisconsin, Madison, in 1957. Before joining the Berkeley faculty in 1988, he spent thirty
years in fusion energy research at the Oak Ridge National Laboratory, at General Atomics, and finally at
the Lawrence Livermore National Laboratory, where he served as an Associate Director of the Laboratory
and head of magnetic fusion energy research from 1970 to 1987. During 1987-1988, he was U. S.
Representative on the Working Group that initiated the International Thermonuclear Experimental
Reactor now known as ITER and under construction in France. He has served on numerous governmental
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and academic committees and served as Chair of the Department of Nuclear Engineering at Berkeley
from 1988 to 1994. He was elected to the National Academy of Sciences in 1987. He is also a fellow of
the California Council on Science and Technology that advises the Governor and Legislature on science
important to the State. His honors include the Distinguished Service Citation from the University of
Wisconsin in 1981 and the Berkeley Citation in 1995.
JEFFREY P. FREIDBERG is an emeritus professor of nuclear science and engineering at theMassachusetts Institute of Technology, and a senior researcher at NYU's Courant Institute ofMathematical Sciences. Previously he was the head of the Nuclear Science and Engineering Department
at Massachusetts Institute of Technology. He also formerly served as the Director of MIT Plasma Scienceand Fusion Center. He earned his B.S., M.S. and Ph.D. degrees from Polytechnic Institute of Brooklyn(now New York University Tandon School of Engineering).
RONALD M. GILGENBACH is Chihiro Kikuchi Collegiate Professor in the Nuclear Engineering andRadiological Sciences Department at the University of Michigan. He is also a past associate editor of thejournal Physics of Plasmas. In the 1970's he was a member of the technical staff at Bell Labs, performed
gyrotron research at the Naval Research Lab (NRL), and electron cyclotron heating experiments on the
ISX-B tokamak at Oak Ridge National Lab. He has collaborated in research with scientists at Air Force
Research Lab, Sandia National Labs, NASA Glenn, Northrop-Grumman, L-3 Communications, General
Motors Research Labs, Los Alamos National Lab, Fermilab, Naval Research Lab and Institute of High
Current Electronics (Russia). He earned his Ph.D. in Electrical Engineering from Columbia University
and M.S. and B.S. at the University of Wisconsin.
WILLIAM HEIDBRINK is a professor of experimental plasma physics at the University of California in
Irvine. After working as a staff member on the TFTR tokamak (Princeton) and the DIII-D tokamak(General Atomics), he joined the UCI Physics Department in 1988. Professor Heidbrink studies highenergy “fast” ions in magnetic fusion experiments. Instabilities that are driven unstable by the free energy
in the fast-ion population are a major area of study. Other important topics include diagnostic
development and measurements of fast-ion confinement. The research is conducted on two facilities. The
DIII-D tokamak in San Diego is the leading magnetic fusion facility in the USA. Professor Heidbrinkearned his B.A. degree from the University of California, San Diego and Ph.D. from Princeton
University.
MARK HERRMANN i is the director of the National Ignition Facility (NIF), the world’s largest laser, at
Lawrence Livermore National Laboratory (LLNL). NIF is a key experimental facility for the sciencebased Stockpile Stewardship Program. Dr. Herrmann spent 9 years at Sandia National Laboratories,
where he studied the use of large magnetic fields generated by the Z facility to create and control highenergy density matter. While at Sandia, he held a number of positions, including Director of the PulsedPower Sciences Center. He began his career as a physicist at LLNL, where his research focused oninertial confinement fusion and high energy density science. He has been awarded a Presidential Early
Career Award for Scientists and Engineers, the American Physical Society Award for Outstanding
Doctoral Dissertation in Plasma Physics, and the Fusion Power Associates Excellence in Fusion
Engineering Award. Mark is a fellow of the American Physical Society. He received his undergraduate
degrees from Washington University in St. Louis, and his Ph.D. from the Program in Plasma Physics at
Princeton University.
FRANK JENKO is a professor at the University of Texas at Austin and Director at the Max Planck
Institute for Plasma Physics. He has been serving as professor in the Department of Physics & Astronomy
and Director of the Plasma Science and Technology Institute (PSTI) at the University of California, Los
Angeles (UCLA), as a member of the editorial boards of Computer Physics Communications, Journal of
Plasma Physics, and New Journal of Physics, as a co-director of the International Helmholtz Graduate
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School for Plasma Physics, and as a member of the steering committee of the Max-Planck/Princeton
Center for Plasma Physics. He co-pioneered the development and application of grid-based numerical
techniques for the investigation of kinetic turbulence in magnetized plasmas. Since then, his computer
simulation code GENE has been playing a key role for analyzing both laboratory and natural plasmas,
standing at the forefront of high-performance computing. Frank Jenko obtained his Ph.D. in physics fromthe Technische Universität München (TUM).
STANLEY KAYE is the principle research physicist and Deputy Director of Research on NSTX-U at theU.S Department of Energy’s Plasma Physics Laboratory in Princeton University. He was recently nameda Fellow by the American Physical Society (APS). He is considered a pioneering investigator of thecharacteristics of strongly heated plasmas confined by magnetic fields. Kaye received a Bachelor's degreein physics and math from Hamilton College in Clinton, New York, a Master's degree in geophysics andspace physics from the University of Washington in Seattle, and a Ph.D. in space plasma physics from the
University of California at Los Angeles.
MITSURU KIKUCHI is a supreme researcher at the Naka Fusion Institute, Fusion Research andDevelopment Directorate, Japan Atomic Energy Agency. He joined JAEA in 1981 as a research associate.
He has held visiting and guest professorships at Osaka University (Japan), Southwestern Institute ofPhysics (China), the Modern Physics Institute at Fudan University (China), and the Chinese Academy of
Sciences. He has served as chairman of the Board of Editors of Nuclear Fusion. He is chair of theDivision of Plasma Physics of the Association of Asia Pacific Physical Societies. He received his Doctorof Philosophy in Engineering from the University of Tokyo in 1981 at Japan Atomic Energy Agency.
SUSANA REYES is a nuclear engineer at Berkeley Lab with over 17 years of experience in international
fusion projects. Until recently, she lead LLNL’s fusion energy science efforts for safety and tritium
research, as well as supporting the National Ignition Facility (NIF) Directorate in various Project
Engineering and Strategic Planning activities. Dr. Reyes earned an M.Sci. in Power Engineering from the
Polytechnic University of Madrid in 1998, and a Ph.D. in Nuclear Engineering from the UNED
University in Madrid in 2001. Dr. Reyes joined LLNL's Fusion Energy Program in 1999 to work on thesafety analysis of inertial fusion energy power plant designs. Since then, she has participated in thedesign, construction, and operation of a variety of fusion research projects, including the NIF in LLNL,
and the ITER Organization in Cadarache (France), where she supported the project through thecoordination of safety analyses and associated documentation in preparation for ITER licensing. Her
current interests are focused on the safety and environmental aspects of fusion and the fuel cycle
challenges for future fusion power plants. Dr. Reyes is the recipient of the 2012 American Nuclear
Society (ANS) Mary Jane Oestmann Professional Women’s Achievement Award, and the 2015 Fusion
Power Associates Excellence 9 in Fusion Engineering Award, for her contributions to the safety andenvironmental aspects of both magnetic fusion energy (MFE) and inertial fusion energy (IFE) facilities.
She recently served as chair of the American Nuclear Society’s Fusion Energy Division.
HON. C. PAUL ROBINSON [NAE] is the vice-chairman of the Board of Directors of ARC. He was theambassador to Russia under President Reagan. He spent most of his career at Los Alamos National
Laboratory and Sandia National Laboratories, becoming President of Sandia Corporation in 1995. Dr.
Robinson was elected to the National Academy of Engineering in 1998 and serves on the Committee on
Membership. He received the Outstanding Public Service Medal from the Joint Chiefs of Staff, the Smyth
Nuclear Statesman Award from the American Nuclear Society, the American Physical Society Pake
Prize, the New Mexico Governor’s Distinguished Citizen Award, and the Department of Energy
Secretary’s Gold Award. He has also served as a trustee of the Kazakhstan Nonproliferation Institute. Dr.
Robinson earned a B.S. in Physics from Christian Brothers College and a Ph.D. in Physics from Florida
State University, and received an honorary doctorate from Christian Brothers University.

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PHIL SNYDER is the director of the Theory and Computational Science group for General Atomics’
Energy And Advanced Concepts Group. He joined the General Atomics Theory and Computational
Science Division in 1999, and became manager of the Turbulence and Transport group in 2010. His
recent research has focused on the edge region of fusion plasmas, particularly the physics of the edgetransport barrier (“pedestal”) and edge localized modes in tokamaks. Dr. Snyder has served as chair of the
Sherwood Executive Committee and the Edge Coordinating Committee, and is currently Principal
Investigator of the Edge Simulation Laboratory project. He is a fellow of the APS (2010) and a recipientof the Rosenbluth Award for Fusion Theory (2004). Dr. Philip Snyder studied computational physics at
Yale University, receiving his B.S. degree and then earned his Ph.D. in Plasma Physics from Princeton
University.
AMY WENDT is a professor of Electrical and Computer Engineering at UW-Madison, where she has
been a faculty member since 1990. Her research focus is ionized gas discharges for technologicalapplications. Understanding the behavior of low-temperature plasmas, how they interact with materials
substrates and implications for process and system design are the primary goals of her research. Her
research group conducts experimental studies with activities including diagnostic development, plasma
source design and process development. She is the co-Director of the Women in Science and Engineering
Leadership Institute at UW-Madison, and received the 2015 College of Engineering Equity and Diversity
Award. She served on the NRC Plasma Science Committee from 2007 to 2014, the Fusion Energy
Sciences Advisory Committee (FESAC) from 2017 to 2020 and as chair of the Gaseous Electronics
Conference Executive Committee from 2012 to 2014. Professor Wendt received MS and Ph.D. degrees inElectrical Engineering and Computer Science from UC Berkeley and a B.S. in Engineering from Caltech.
BRIAN D. WIRTH is a professor and Governor’s Chair of Computational Nuclear Engineering in the
Department of Nuclear Engineering at the University of Tennessee, Knoxville, which he joined in July
2010. Dr. Wirth spent four years in the High Performance Computational Materials Science Group at
Lawrence Livermore National Laboratory, where he lead efforts to investigate the microstructural
stability of structural materials in nuclear environments. In 2002 he joined the faculty at the University ofCalifornia, Berkeley as an Assistant Professor of Nuclear Engineering and was promoted to Associate
Professor in 2006. He has received a number of awards, including the 2007 Fusion Power Associates
David J. Rose Excellence in Fusion Engineering Award and the 2003 Presidential Early Career Award for
Scientists and Engineers (PECASE). Brian received a BS in nuclear engineering from the Georgia
Institute of Technology and a PhD in mechanical engineering from the University of California, Santa
Barbara.

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K
Glossary and Acronyms
ANS
APS
ARIES
BPA
BSCCO
CANDU
CD
CEA
CFETR
CFS
CTH
DEMO
DOE
DONES
ECCD
ECFS
EFDA
EHO
ELM
EP
EU
FACA
FES
FESAC
FINESSE
FPCC
FRC
FSNF
FW
FY
GAO
GE
GDC
GDT
HEPAP
HIFR
HSX
HTS
IEEE
IFMIF
IO

American Nuclear Society
American Physical Society
Board on Physics and Astronomy
Bismuth Strontium Calcium Copper Oxide
Canada Deuterium Uranium
Current Drive
French Alternative Energies and Atomic Energy Commission
China Fusion Energy Test Reactor
Commonwealth Fusion Systems
Demonstration Power Plant
U.S. Department of Energy
DEMO-Oriented Neutron Source
Electron Cyclotron Current Drive
Early Career Fusion Scientists
European Fusion Development Agreement
Edge Harmonic Oscillation
Edge Localized Modes
Energetic Particle
European Union
Federal Advisory Committee Act
Office of Fusion Energy Sciences
Fusion Energy Sciences Advisory Committee
Fusion Integral Nuclear Experiments Strategy Study Effort
Fusion Power Coordinating Committee
Field-Reversed Configuration
Fusion Nuclear Science Facility
Fast Waves
Fiscal Year
U.S. Government Accountability Office
General Electric Company
General Dynamics Convair Division
Gas Dynamic Trap
High Energy Physics Advisory PanelHigh Flux Isotope Reactor
Helically Symmetric ExperimentHigh Temperature Superconductors
Institute for Electrical and Electronics Engineers
International Fusion Materials Irradiation Facility
International Organization

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ITPA
IRP
INL
ITER
JET
LCP
LCTF
LH
LHC
LHD
LM
LTC
LTS
NB
MAST-UMaPLEMELCOR
MFR
MGI
MIT
MHD
NAS
NASEM
NERSC
NBCD
NIF
NIFS
NRC
NSTX
NTM
OFES
OPG
ORNL
PFC
PISCES
PMI
PSI
QA
QH
REBCO
RF
RM
ROK
SAS
SLM
SPI
STAR
STARLITETBM
TBRInternational Tokamak Physics Activity
ITER Research Plan
Idaho National Laboratory
International Thermonuclear Experimental Reactor
Large Coil Project
Large Coil Test Facility
Lower Hybrid
Large Hadron Collider
Large Helical Device
Liquid Metal
Low Temperature Superconducting
Low-Critical-Temperature Superconductors
Neutral Beams
Magnetohydrodynamic PbLi Experiment
U.S. Magnetic Fusion Research
Massive Gas Injection
Massachusetts Institute of Technology
Magnetohydrodynamic
U.S. National Academy of Sciences
National Academies of Science, Engineering, and Medicine
National Energy Research Supercomputer Center
National Ignition Facility
National Institute for Fusion Science
U.S. National Research Council
National Spherical Torus Experiment
Neoclassical Tearing Modes
Office of Fusion Energy Sciences
Ontario Power Generation
Oak Ridge National Laboratory
Plasma Facing Components
Plasma Surface Interaction Experimental Facility
Plasma-Material Interactions
Swiss Paul Scherrer Institute
Quasi-Axisymmery
Quasi-Helical-SymmetryRare-Earth Barium Copper-Oxides
Radio Frequency
Remote MaintenanceRepublic of Korea
Small-Angle Slot
Selective Laser Melting
Shattered Pellet Injection
Safety and Tritium Applied Research
Test Blanket Module
Tritium Breeding Ratios

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TEC
TFTR
TGAP
TMAP
TPE
TCV
UFA
USBPO
VLT
VNS
WCM
WDM
WH

Transformative Enabling Capabilities
Tokamak Fusion Test Reactor
Tritium Gas Absorption Permeation
Tritium Migration Analysis Program
Tritium Plasma Experiment
TCV is a medium size tokamak, Tokamak à Configuration Variable, (EPFL Lausanne,
Switzerland, https://spc.epfl.ch/research_TCV_Tokamak)
University Fusion Association
United States Burning Plasma Organization
Virtual Laboratory for Technology
Volume Neutron Source
Weakly Coherent Mode
Whole Device ModelingWestinghouse Electric Corporation

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