**Executive Summary**

The NCSX Review Committee was appointed by the Fusion Energy Sciences
Advisory Committee to respond to a charge from Dr. Raymond Orbach, Under
Secretary of Science, US Department of Energy, that was issued on August
9. Details of the charge, and the procedures used by the Committee in
its deliberations, may be found in the text of this report. The present
summary provides a condensed version of the Committee's answers to each
question (shown in boldface) in the charge.

**1. Critical issues for the US compact stellarator program**

**a. What unique toroidal fusion science and technology issues can a
compact stellarator program address independent of its potential for a
reactor concept?**

Stellarator research programs have the generic mission of studying a
confinement system that addresses two key issues in fusion energy
research: disruption avoidance and steady-state operation. This mission
is approached by means of plasma shaping in three dimensions,
sacrificing the axial symmetry of the tokamak, and thus allowing
scientific exploration of the opportunities and penalties associated
with three-dimensional geometry. The scientific issues to be addressed
in the program include transport, energetic particle confinement,
equilibrium, stability and density limits (including disruption
avoidance), and particle and power handling. Technology issues to be
explored include simpler magnet coils and support structures, metrology,
correction coils and divertors.

The *compact* quasi-axisymmetric stellarator is distinctive in having
relatively small aspect ratio -- typically less than five. In this
respect its geometry approaches that of a tokamak, and indeed the
scientific and technical similarity with the tokamak, along with
improved cost-effectiveness, provides the main scientific impetus for
compactness: there is no strong motivation for low aspect ratio from the
perspective of stellarator physics. One expects experiments on a compact
stellarator to provide particular insights into tokamak physics; and
similarly one expects existing knowledge of tokamak behavior to benefit
particularly a compact stellarator research program. The Committee finds
these potential mutual rewards to be plausible and significant.

> **b. What are the advantages and disadvantages of the quasi-symmetric
> stellarator as a potential fusion system concept? What unique features
> does the compact stellarator offer in this regard?**

Stellarators offer the important advantages of steady-state operation
with relatively soft and forgiving stability limits -- advantages that
might become especially important as the international fusion program
begins to study the DEMO device that is expected to follow ITER.
Quasi-symmetry reduces the effective radial widths of particle
drift-orbits, thereby ameliorating the large neoclassical transport
rates associated with more conventional stellarator designs. Because it
allows for decreased zonal-flow damping, quasi-symmetry may also reduce
turbulent transport rates, although this apparent advantage requires
more study.

The key disadvantage of the stellarator is the complexity and cost of
its field coils, whose precise construction and alignment are essential
for acceptable confinement. Compactness exacerbates this problem, in
that the increased toroidicity for a given rotational transform makes
the flux surfaces more fragile. The Committee points out that present
coil designs significantly complicate external access to the plasma and
to the plasma blanket, for maintenance or other purposes, in a
stellarator reactor.

A study by the ARIES team indicates somewhat smaller construction and
operation costs for a compact stellarator, compared to a stellarator
with large aspect ratio. At the same time it is recognized that, at this
early stage of investigation, there remain many unanswered questions
about compact stellarator reactor performance. In particular the smaller
surface to volume ratio associated with compactness is disadvantageous
with regard to heat removal and tritium self-sufficiency.

> **c. What scientific and technical issues need to be resolved to
> evaluate the compact stellarator as a viable concept for a fusion
> energy system?**

Many issues, detailed in the body of this report, will need to be
addressed in the design of a stellarator for fusion energy production.
Three issues of particular note for compact stellarators as a fusion
concept are: determination of the size scaling of confinement; the
required tolerances for coil construction; and the magnitude of plasma
current below which disruptions due to plasma instabilities are avoided.

2\. **Role of NCSX in the international context:**

**a. What critical, unique contributions does NCSX offer for addressing
the issues identified in (1)?**

NCSX is designed to address most of the critical physics and technology
issues discussed in this report, using a compact, quasi-axisymmetric
configuration that is unique in the world stellarator program. The
Committee finds that, assuming successful construction and testing
phases, the NCSX device is likely to perform at a level sufficient to
address its scientific and technical missions. Therefore the Committee
expects the NCSX experimental program to have a profound impact on
stellarator research worldwide.

There are several methods to ameliorate the large orbital excursions
that can degrade confinement in non-axisymmetric systems.
Quasi-symmetry, the approach now favored in the US, itself includes
several varieties: quasi-poloidal symmetry (QPS), quasi-helical symmetry
(QHS) and quasi-axial symmetry or quasi-axisymmetry (QAS). NCSX is the
only experimental device in the world program that would employ the QAS
concept.

By virtue of both QAS and compactness, NCSX offers a similarity to
tokamak science that is unmatched by any other stellarator device. In
this regard, the hybrid nature of NCSX confinement -- that is, dual
origin of its rotational transform, which is produced partly from
external coils and partly from plasma currents -- should allow a
particularly instructive research program. Similarly its resemblance to
the tokamak should allow NCSX to illuminate a number of issues
concerning symmetry and effects of symmetry-breaking on confinement.

NCSX is a Proof-of-Principle (PoP) class experiment, minimally sized to
provide credible integrated confinement and stability results. Thus it
is larger than such stellarators as HSX at the University of
Wisconsin-Madison, but smaller than, for example, the DIII-D National
Tokamak Facility, and the stellarators W7-X (Germany) and LHD (Japan).
Comparative studies of the three major lines in the international
stellarator program -- LHD , W7-X , and NCSX -- will inform a decision
on which system has the highest reactor potential, and thus influence
discussions on the continuation of the fusion program toward the DEMO
reactor.

**b. Given PPPL's \[Princeton Plasma Physics Laboratory's\] proposed
plans for operation of the National Spherical Torus Experiment \[NSTX\]
and NCSX, what would be the timetable for resolving relevant issues
identified in (1) above?**

NCSX plans to achieve its first plasma in 2012, two years before W7-X
and four years before ITER. For the following several years, the NCSX
team plans to alternate its operation with that of NSTX; thus the key
initial experimental results for NCSX would be obtained in FY2013 and
FY2015. The Committee is concerned about the practical realism of this
plan; we find in particular that the resolution of key experimental
issues is likely to require five years of actual operation.

One technical requirement that the Committee considers likely to affect
the timeliness of physics results is the quality of the magnetic flux
surfaces in three-dimensional geometry. The NCSX team has developed
appropriate strategies, involving both assembly procedures and the use
of an array of trim coils, for constructing and maintaining flux
surfaces with relatively few magnetic islands and relatively small
chaotic regions. While finding these strategies to be well thought out,
the Committee recommends that attention to construction details that may
affect flux-surface quality, and the study of their effects and methods
to counteract them, remain top priorities for the project.

> **c. What are the technical differences of the current NCSX design
> compared to other stellarators operating or being built abroad? What
> is the significance of these differences? Does NCSX fill a critical
> void in the development of the stellarator concept as a viable fusion
> energy system?**

As pointed out earlier in this summary, NCSX will be unique in the world
stellarator research program, because of both its quasi-axisymmetry and
its compactness. The W7-X device uses a distinct configuration
optimization, has a large aspect ratio, and moreover is designed to
minimize plasma currents (recall that NCSX will depend upon self-induced
plasma current for a fraction of its rotational transform). The LHD
device achieves reduced orbital excursions by means other than
quasi-symmetry; it has a intermediate aspect ratio. Both W7-X and LHD
employ super-conducting magnets. The Committee finds that the comparison
of these three devices will be extremely useful in understanding the
physics optimization of advanced stellarator configurations.

**3. Options for the US stellarator program**

> **a. If the NCSX program were not continued, what options would exist
> or would be possible to address the key issues of the quasi-symmetric
> stellarator in general and the compact stellarator in particular?**

The present US stellarator research program includes other devices,
planned or in operation, that could address at various levels a subset
of the key issues listed in the response to question 1. However no US
experimental program, present or planned, could provide the breadth of
scientific and technical information that is expected to come from NCSX.
The only PoP scale device in the US repertoire that addresses
quasi-symmetry is NCSX, and NCSX is the only such device capable of
examining the key issues in an integrated context. Therefore, if NCSX
were abandoned, the US would have to reduce significantly its ambitions
in stellarator research, or begin constructing a new PoP stellarator
experiment.

The Committee finds it important that the US have a significant
stellarator presence as part of its magnetic fusion energy research
program. The Committee notes that at present about 75% of the US
stellarator effort is focused on the construction of NCSX, so the loss
of NCSX would change the basic character of the US program. The program
would lose its integrated PoP facility and the most relevant connections
to tokamak research.

> **b. Assuming NCSX is not available, what program elements would be
> required to maintain the US as a significant participant in the
> international stellarator program?**
>
> **i. Identify potential opportunities for US leadership.**
>
> **ii. Include more international collaboration as appropriate.**

The US has the only operating quasi-symmetric stellarator device in the
world, the HSX at the University of Wisconsin-Madison; it allows
fundamental tests of quasi-symmetry and can span a range of
symmetry-breaking geometries. The CTH device is a low aspect-ratio
stellarator at Auburn University that is used to study passive
disruption avoidance. Both of these relatively small experiments provide
valuable scientific information, and both could be upgraded, but neither
could provide the sort of integrated research program of a PoP device
like NCSX.

The proposed QPS device at Oak Ridge National Laboratory is a low aspect
ratio stellarator with quasi-poloidal symmetry. It has some similarity
with the (much higher aspect ratio) W7-X device; furthermore it should
allow strong poloidal flows, unlike those seen on existing toroidal
confinement experiments. Thus QPS could extend the stellarator data base
in a useful way. But it would not replace the scope of the NCSX program,
in particular having much weaker links to tokamak behavior.

The Committee recommends that the construction decision on QPS be
expedited if NCSX is cancelled. However, we find it illogical to cancel
a stellarator project that is nearing its final construction phases only
to begin a new stellarator with poloidal rather than toroidal
quasi-symmetry.

In the absence of NCSX, a restructured US stellarator program could
maintain scientific leadership in selected research topics, but would
have difficulty playing a significant role in the direction of worldwide
stellarator research. International collaboration is already a key
element of US stellarator research and would remain so in the absence of
NCSX. However, the benefits gained from such collaboration would be
diminished without a domestic stellarator experiment on the PoP scale.

Quasi-symmetry is one of many ways to optimize 3-D configurations; other
optimization schemes could be pursued. If NCSX were discontinued, the US
stellarator program should consider a variety of approaches to
stellarator optimization in proposing a new PoP stellarator project.

The US has been a leader in theory and computation on three-dimensional
confinement, in large part because of the impetus provided by the NCSX
and QPS design programs. There are many opportunities for useful
theoretical and computational advance, and encouragement by the Office
of Fusion Energy Sciences of such research would help the US maintain
its presence in the international effort. However, the loss of a
world-class experiment in the US would hurt the recruitment of young
scientists into stellarator theory.

Introduction

The NCSX Review Committee was formed in response to a charge to the
Fusion Energy Sciences Advisory Committee (FESAC) from Dr Raymond
Orbach, Under Secretary for Science at the Department of Energy (DOE),
issued on August 9, 2007. The full charge is appended to this report
(Appendix A); it requests FESAC to "conduct a scientific and
programmatic review focused on evaluating the NCSX program and its
potential effect on the US fusion energy sciences program." The charge
lists four detailed questions concerning technical and scientific
aspects of (i) compact stellarator research, and (ii) the NCSX program
specifically.

It was decided from the start, in discussion with Dr. Fonck, Associate
Director of the Office of Fusion Energy Sciences, that the Review
Committee would focus its attention of the first three of the four
questions; these questions are repeated as headings of the three
numbered Sections in the Committee\'s report that follows.

The ten members of the Review Committee are listed in Appendix B. The
membership includes prominent scientists and engineers from
laboratories, universities and private industry. Leading stellarator
researchers from the US, Europe and Japan are Committee members, as well
as scientists working outside the stellarator program.

The Review Committee began its work by reviewing a large body of
technical literature: technical articles on stellarators and NCSX from
the published literature; unpublished reports and presentations on the
NCSX program, including the May 2001 FESAC Report of the NCSX Physics
Validation Review; and a special summary report, prepared as a service
to the Committee by the ARIES team. In addition, members of the NCSX
team provided documents addressing each question raised in the Review
Committee\'s charge. The Committee takes this opportunity to thank the
ARIES and NCSX scientists for their time and effort in compiling this
extremely helpful material.

Most of the Review Committee\'s discussions were conducted by
teleconference and email. (Email correspondence was simplified by a
Review Committee email reflector, set up with help from the US Burning
Plasma Organization, whom we thank.) The Committee met once at the NCSX
experimental site at the Princeton Plasma Physics Laboratory (PPPL). The
site visit included extensive presentations by members of the NCSX team
addressed specifically to the Committee\'s charge, as well as a brief
tour the NCSX construction.

All members of the Review Committee participated in the discussion of
each charge question, and all members agreed to the conclusions
presented in this report.

Before addressing the specific questions in the Charge, we survey the
scientific and programmatic context of the NCSX project.

The US stellarator program has chosen a research path that emphasizes
simultaneously two design principles: quasi-symmetry and compactness. A
quasi-symmetric configuration is one in which the magnitude of the
magnetic field in a particular direction along the torus is roughly
constant even though the components of B are not. Such a device combines
the inherent steady-state nature of the stellarator as a magnetic
confinement scheme for fusion with the good single-particle confinement
of a tokamak. The main element of the program is the PoP experiment
under construction, NCSX at Princeton Plasma Physics Laboratory (PPPL),
which is quasi-symmetric in the toroidal direction (quasi-axisymmetric,
or QAS). The other experimental elements of the program are the
quasi-helical HSX at the University of Wisconsin-Madison, which is
operating and the quasi-poloidal QPS at the Oak Ridge National
Laboratory (ORNL) which is under prototype development but not yet
approved for construction. In addition, CTH at Auburn University is a
nonsymmetric stellarator with ohmic heating that is exploring
equilibrium and stability issues that are relevant to the operation of a
compact stellarator with substantial plasma current. The designation of
"compact" within the framework of the US stellarator program typically
means that the aspect ratio is less than five. Only HSX has an aspect
ratio greater than this. The other key elements of the US compact
stellarator program are theory and computation.

1.  **Critical Scientific Issues For The US Compact Stellarator
    Program:**

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a.  *What unique toroidal fusion science and technology issues can a
    compact stellarator program address, independent of its potential
    for a reactor concept?*

Tokamaks rely on plasma shaping in the poloidal and radial directions to
improve plasma stability and confinement. The compact stellarator
program utilizes additional shaping of the magnetic surfaces in the
toroidal direction to explore the potential science, technology and
reactor benefits as well as possible challenges. The scientific issues
to be addressed in the program include disruptions, transport, energetic
particle confinement, equilibrium, stability and density limits, and
particle and power handling. Technology issues to be explored include
simpler magnet coils and support structures, metrology, correction coils
and divertors. While operating stellarators at an aspect ratio
comparable to tokamaks may help elucidate differences in scaling laws,
transport and stability, there is no strong motivation for low aspect
ratio from the perspective of stellarator physics. Rather, the
incentives for compactness are a stronger tie to the tokamak database
and the prospect that lower aspect ratio will decrease capital costs and
lead to a more economical fusion reactor.

**Disruptions:** Quasi-axisymmetric stellarators like NCSX would have
large bootstrap currents. Disruptions in currentless stellarators are
generally not observed, even when operated at betas above the ideal
stability limits. The key issue for these devices is to determine at
what level of free energy in the magnetic field due to plasma current do
disruption-like effects begin to appear. Stellarators with plasma
current can also contribute to understanding and controlling tokamak
instabilities such as Neoclassical Tearing Modes (NTM) (which limit many
tokamak operating regimes) and Edge Localized Modes (ELMs) (which may
limit the lifetime of plasma-facing components in large-scale tokamaks).

**Transport:** While tokamaks have good particle confinement due to
symmetry in the toroidal direction, conventional stellarators have poor
neoclassical transport properties at low collisionality because of the
breaking of that symmetry. The innovative concept of quasi-symmetry
bridges the gap between stellarators and tokamaks by restoring a
direction of symmetry in the magnetic field magnitude. Results from the
HSX experiment with quasi-helical symmetry at moderate aspect ratio have
demonstrated reductions in plasma flow damping, particle transport and
electron thermal conductivity.

As neoclassical transport is reduced, it is anticipated that
turbulent-driven transport (so-called "anomalous" transport) as seen in
tokamaks will become increasingly important for the compact stellarator
program. Tokamak transport is believed to be strongly influenced by the
presence of large-scale plasma flows. With quasi-symmetric stellarators,
anomalous transport could be strongly affected in the same manner as in
tokamaks because there is now a direction of symmetry along which plasma
can flow. Zonal flow damping in such configurations may also be reduced.
A stellarator with the capability to heat with or without applied torque
in a magnetic configuration with varying degrees of quasi-symmetry
should be a powerful physics tool for understanding flows and their role
in plasma confinement. Once the character of the turbulence in
stellarators is understood, the design tools created to optimize
quasi-symmetry might also be applied to optimize the magnetic geometry
for neoclassical and anomalous transport simultaneously.

**Energetic Particle Confinement:** Another issue related to transport
is that of energetic particle confinement. Ripple and stochastic
transport are issues for high energy particles in tokamaks and needs to
be explored in the compact stellarator program as well. How susceptible
energetic particles are to Alfvenic instabilities needs to be addressed.
Whether fast particle losses can be mitigated by operation at higher
densities in stellarators or by other means also needs to be explored.

**Equilibrium:** There is some indication that equilibrium limits in
stellarators may be set by the degradation of magnetic surface quality.
The response of the plasma to magnetic perturbations is a cross-cutting
issue with ties to the tokamak program. A key element of the compact
stellarator effort is to accurately reconstruct the 3D magnetic
equilibrium from magnetic coils and other diagnostics. Such capability
would be beneficial to tokamaks which also exhibit signs of 3D behavior.
At present, the CTH stellarator is the primary test bed for this work.
An important addition to the 3D reconstruction effort would be the
inclusion of magnetic islands in the equilibrium.

**Stability and Density Limits:** Experimental evidence indicates that
operational limits of pressure and density in a stellarator are
relatively benign and lead to degraded performance, in contrast to
tokamaks where encounters with the operational boundaries can lead to
termination of the plasma. A volume-averaged beta of 5% was
recently achieved in LHD, which is above the calculated limit for
ballooning modes. Plasma pressure in conventional stellarators is not
limited to the linear ideal MHD stability threshold. A compact
stellarator experiment with significant bootstrap current needs
sufficient auxiliary heating to reach the theoretical beta limit and a
long enough pulse length so that the total rotational transform remains
steady. Data from such an experiment would also allow correlation with
the extensive database of tokamak stability. Similar arguments also
apply to density limits. The density limit in tokamaks and stellarators
may eventually be shown to arise from radiative cooling of the plasma
edge; however, the limit often leads to disruption in tokamaks, while in
stellarators, the plasma simply collapses from
recombination. Experiments are needed to test the density limit in
compact stellarators with plasma current.

**Particle and Power Handling:** A key challenge for stellarator design
is to deal with the heat and particle fluxes in the complex 3-D magnetic
configuration. It is important to assess these issues in a plasma that
is sufficiently opaque to neutrals and has sufficiently high heat fluxes
so that both the confined plasma and the edge plasma are in regimes
interesting for fusion. In a compact stellarator design, it should be
possible to reach and study these conditions more easily (smaller device
with lower power) than with a conventional design. The sensitivity of
the magnetic configuration at low aspect ratio to applied fields that
break the stellarator symmetry may actually be advantageous to this area
of research. Tokamaks, for example, are investigating symmetry-breaking
at the plasma edge to control ELMs.

**Coils and Structures:** As for technology issues, a main concern that
could be addressed is that of designing and building simpler magnetic
coils and support structures. These are issues that are presently
causing difficulties in the W7-X and NCSX construction projects. Much
depends on understanding the scientific issues within an overall
optimization scheme such as how low an effective ripple is needed or
what constraints are necessary to satisfy stability criteria. Relaxation
of such constraints might lead to coils that are easier to build. Also
the issue of tolerance requirements needs to be addressed for magnet
coil manufacture as well as coil and field period assembly. Field error
control, mode locking and subsequent disruptions are concerns related to
tolerance requirements for tokamaks.

**Metrology:** A necessary adjunct to this effort is the need to
accurately determine the as-built structure of the magnetic coils and
sensors. The development of metrology capabilities significantly beyond
that existing in the US fusion program is being driven by the
stellarator community. This is applied to the quality assurance in
component fabrication and assembly. Such capabilities might be
transferred to other scientific and industrial applications.

**Correction Coils:** Once the coils are built and mounted within the
support structure and the metrology capabilities determine the tolerance
that has been achieved, the next technology issue to be addressed is
that of correction coils. Inevitably there are deviations of the
as-built device from the design coils and correction coils may be
helpful in relaxing tolerance requirements as well. This is an area of
concern for tokamaks as well as stellarators, so understanding the
physics of error correction (and shielding by rotation and plasma
currents) and developing a technology for minimizing the impact of
imperfect design implementation should benefit all magnetic fusion
research.

**Divertors**: Another important technology issue to be addressed in the
compact stellarator program is that of particle and power handling. The
3D shaping capabilities of stellarators allow for flexibility in edge
geometry including local island divertors and ergodic regions. Control
of neutral recycling and impurities needs to be demonstrated. A key
issue to be addressed is whether the divertor in a lower aspect ratio
device can handle the higher heat flux. Also to be determined is what
design constraints can be relaxed by operating at higher densities and
with radiative cooling.

b.  *What are the advantages and disadvantages of the quasi-symmetric
    stellarator as a potential fusion system concept? What unique
    features does the compact stellarator offer in this regard?*

The compact quasi-symmetric stellarator could address questions arising
in the transition from ITER to a DEMO fusion reactor. Specifically,
first-wall lifetime and reactor availability require disruption and ELM
suppression. Stellarators have already demonstrated the ability to
operate disruption-free also at stability boundaries. They rely on
external currents instead of current drive to provide rotational
transform and are inherently steady-state. High density operation is
possible in stellarators without regard for the rotational transform.
This facilitates solutions for divertor operation and allows the density
to be chosen to minimize potential problems due to the fast-particle
population and synchrotron radiation losses.

The quasi-symmetric approach to plasma shaping overcomes the poor
neoclassical confinement of conventional stellarators at low
collisionality. Without the resulting increased gain, a stellarator
reactor would have difficulty reaching ignition conditions.

From the science perspective, a disadvantage of the quasi-symmetric
approach is that the reduction in the effective ripple, while beneficial
for transport, makes access to the electron root of the ambipolarity
constraint more difficult. This could imply that shear stabilization of
turbulence by the neoclassical electric field, through the proximity of
electron and ion roots, may no longer be possible. A quasi-symmetric
stellarator would then have the same problems faced by tokamaks: E x B
shear stabilization may not scale to a reactor because of small ρ\*
(ratio of gyroradius to minor radius); additional momentum input may be
required. Another disadvantage of the quasi-symmetric approach is the
complex technology of the modular coils that are needed for the plasma
shaping.

Compared to a higher aspect ratio stellarator, a compact stellarator
offers the possibility of lower initial capital cost, lower cost of
electricity (COE), lower fusion power output (for more flexible
application) and lower volumes of radioactive waste. These are the major
arguments why the US stellarator community advocates a stellarator
reactor with a tighter aspect ratio. The ARIES-CS (CS for compact
stellarator) fusion reactor design study was completed in 2006 based on
an NCSX-class quasi-axisymmetric configuration. The device has a major
radius of 7.75 m and an aspect ratio of 4.5. The size and mass were
similar to an advanced tokamak power plant.

In a summary report to this Committee, the ARIES-CS team described some
of problems associated with compact stellarator reactor design. For a
major radius less than 7.5 m, there was not enough space for blankets to
provide tritium self-sufficiency. There were concerns with high heat
flux to the first wall and divertors. More work was needed to reduce the
energetic alpha loss further. A complex support structure was designed
which would be difficult to build with conventional manufacturing. A new
fabrication technology called "additive manufacturing" was assumed.
Access to the blanket was challenging because of the modular coils. The
ARIES team emphasized that in their estimates of the COE they did not
include a penalty for the complexity of the components or a possible
lower reliability because of that complexity. Hence they stated that
cross-comparison with a tokamak is not meaningful, although comparisons
with other stellarators was valid.

The ARIES team did make a comparison to a larger aspect-ratio
stellarator reactor design conducted in 1996. This was the SPPS study,
which was based on a configuration similar to HSX. The SPPS reactor has
a major radius of 14 m and an aspect ratio of 8.5. At roughly half the
aspect ratio of SPPS, the ARIES-CS COE was only 20% lower at 78
mills/kWh. Furthermore, they stated "System analysis, however, shows
very little cost benefits in going to smaller size devices."

The ARIES team took special note of two points, which we quote:

a.  "The ARIES-CS study was the first major study of compact
    stellarators. As such, it was conducted in the \`problem finder'
    mode. For example, the design point was pushed to the limit for a
    "compact" configuration with low aspect ratio to better understand
    the constraints imposed by the "compactness" and the possible
    trade-offs. In most areas, we find that increasing the machine size
    compared to ARIES-CS reference design will provide more margins on
    space and engineering constraints such as material stress,
    temperature limits, etc.

b.  Most of the engineering research was performed on NCSX-class
    quasi-\[axi\]symmetric configuration. Caution should be used in
    extrapolating to other compact stellarator configurations."

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c.  *What scientific and technical issues need to be resolved to
    evaluate the compact stellarator as a viable concept for a fusion
    energy system?*

A number of scientific issues need to be resolved to evaluate the
compact stellarator as a fusion reactor. Some of these issues directly
impact the problems tokamaks face in making the transition from ITER to
DEMO. For a quasi-axisymmetric (QAS) stellarator in particular, because
of the relatively large bootstrap current, it is important to understand
how much external rotational transform is needed to eliminate
disruptions. Does the 3D shaping stabilize neoclassical tearing modes?
What magnetic structure at the plasma edge is effective in eliminating
large ELMs? Does the combination of internal rotational transform (from
the bootstrap current) and externally generated transform indeed lead to
stable steady-state operation?

Some of the scientific issues are generic to the quasi-symmetric
concept. At this time, it is still not clear how low the effective
ripple should be. What is the relative role of neoclassical versus
anomalous transport? To what extent does zonal flow damping affect
turbulent transport? Does drift optimization reduce turbulent transport
as well as neoclassical transport? Is it possible to increase the E x B
shearing rate in a quasi-symmetric stellarator to the extent that it
scales to a reactor? How does quasi-symmetry affect energetic particle
confinement and stability? Finally, which form of quasi-symmetry makes
the best reactor? Do we have to test them all or are there
distinguishing features that favor one form over another?

Other scientific issues are more generic to stellarators in general.
This part of the assessment is carried out within the world-wide
stellarator community, of which the major devices are LHD (a
superconducting heliotron device in Japan that achieves some improvement
in transport by shifting the plasma inward), W7-X (a superconducting,
large aspect ratio device in Germany that relies on transport
optimization that is not quasi-symmetric and also minimizes plasma
currents) and NCSX. Being a compact stellarator with a tokamak-like
aspect ratio and quasi-symmetry, NCSX could play a unique role in this
assessment. What limits the plasma beta and density in a stellarator?
How can impurity transport be controlled? How does the plasma respond to
magnetic perturbations? How do equilibrium islands and flux surface
robustness scale with increasing pressure? Is it possible to do 3D
equilibrium reconstruction that detects the presence of island
structures in a stellarator?

The scaling of energy confinement with size is also important to the
viability of stellarators as a fusion energy concept. The size scaling
determines how large a reactor must be to produce fusion power with
sufficient gain. While most of the issues discussed previously can be
studied effectively in a single stellarator, determination of the size
scaling needs data from an array of stellarators. The two methods now
employed to determine the size scaling of tokamaks, database analysis
and dimensionless parameter scaling, have also been applied to
stellarators. From database analysis, the confinement in stellarators
appears to scale with volume, which is favorable compared with tokamaks.
It will be important to determine whether the scaling of optimized
stellarators also follows such scaling. It will be challenging to
compare the many varieties of stellarators in the absence of a validated
first-principles model for stellarator confinement.

In addition to the issues of fusion science, a number of technical
issues need to be resolved for the compact stellarator to be properly
evaluated. One issue that is very much dependent on a resolution of the
scientific issues is whether certain constraints such as stability or
confinement can be relaxed so that magnet coils can be designed that are
easier to build. An issue that the ARIES-CS team faced is whether a
complex support structure for a compact stellarator reactor could be
built without inventing a new fabrication technology. If such a
technology is needed, how easy is it to develop? Does failure of a
magnet coil compromise the power plant or can the coils be replaced
remotely? Is there a remote handling scheme that can deal with the
complex geometry of a compact stellarator? How reliable are the complex
components needed for a compact stellarator? How does that affect
availability and the cost of electricity (COE)? What is the best way to
control particle and heat fluxes at the plasma edge? Which stellarator
geometries best accommodate divertors?

One central question that needs to be addressed is raised by the report
produced by the ARIES-CS team. They found that for configurations of the
NCSX-type there was little benefit in terms of COE in going to even
lower aspect ratio. Are there any compact stellarator configurations at
aspect ratio much lower than five that show a significant decrease in
the cost of electricity?

2\. The Role of NCSX in an International Context

> \(a\) *What critical, unique contributions does NCSX potentially offer
> for addressing the issues identified in (1)?*

NCSX is designed to address most of the critical physics and technology
issues discussed in this report using a compact, quasi-axisymmetric
configuration that is unique in the world stellarator program. The
Committee finds that, assuming successful construction and testing
phases, the NCSX device is likely to perform at a level sufficient to
address its scientific and technical missions. Thus the Committee
expects the NCSX experimental program to have a profound impact on
stellarator research worldwide.

As described in Section 1, the fusion program\'s strong interest in the
stellarator approach is that it potentially offers solutions to the
important problems of disruption avoidance and steady-state operation
facing tokamaks in going from ITER to a DEMO fusion reactor.
Specifically, first wall lifetime and reactor availability require
nearly complete disruption elimination and ELM suppression. Stellarators
have already demonstrated the ability to avoid disruptions and where
ELMs have been observed, they are not severe. Furthermore, by relying
primarily on external currents instead of current-drive or bootstrap
currents to provide rotational transform in the confining magnetic
field, stellarators can more easily operate in steady state.

To explore the potential advantages of disruption avoidance and steady
state operation in a more compact (low aspect ratio) advanced
stellarator employing the quasi-axisymmetric magnetic configuration, the
NCSX experiment was approved by FESAC in 2001 as a PoP class device in
the US fusion energy science program. This places it between smaller
Concept Exploration experiments, such as HSX at the University of
Wisconsin-Madison, and larger Performance Extension class experiments,
such as the DIII-D National Tokamak Facility in the US, the LHD
stellarator in Japan, the W7-X stellarator under construction in Europe
and the even larger burning-plasma class experiment, ITER.

There are two other PoP class experiments in the US fusion program: the
NSTX experiment at PPPL, exploring the compact torus magnetic
configuration, and the MST experiment at the University of
Wisconsin-Madison, exploring the reversed field pinch magnetic
configuration. The characteristic of a PoP class experiment is that it
has the size, magnetic field, and plasma heating systems to allow study
of key physics behaviour of the magnetic configuration concept with
collisionless ions and electrons for many energy confinement times. With
these parameters, the PoP class experiment is minimally sized to provide
credible integrated confinement and stability results that scale to the
10 keV fusion power plant regime of temperature and collisionality, and
hence prove the basic physics principles of the confinement
configuration under study. This normally requires temperatures of both
ions and electrons at the keV level, 1 to 2 Tesla magnetic fields and
several MW of external heating input to the plasma for several tenths of
a second. In terms of key dimensionless parameters, this requires
collisional mean free paths to be dominated by Coulomb collisions and to
be an order of magnitude larger than toroidal or poloidal connection
length scales; a device size many times the characteristic size of the
ion gyroradius; and a plasma pressure normalized to the magnetic energy
density β of at least several percent.

The NCSX experiment was designed to meet these conditions for the
exploration of the quasi-axisymmetric stellarator (QAS) magnetic
configuration. Using expectations of stellarator confinement based on an
extensive data base, the NCSX design projects central ion temperatures
of 1 to 2 keV, magnetic field values of 1 to 2 Tesla, dimensionless
collisionality, ν\* \~ 0.1, β \~ 5%, and at least 10 poloidal ion
gyroradii across the 0.33 m average minor radius using 6 MW of neutral
beam heating. Thus, NCSX is well positioned to carry out PoP
experimental tests of the QAS magnetic configuration.

Three principal concepts are possible for quasi-symmetry: quasi-helical,
quasi-poloidal and quasi-axisymmetry (QAS). Each of the three principal
quasi-symmetric stellarator concepts is being pursued in the world
fusion program. Quasi-helical symmetry is being studied in HSX, which
has been operating for several years; quasi-poloidal symmetry is the
guiding principle of the configuration design of the QPS device
proposal. There are also techniques for optimizing particle orbits
outside of quasi-symmetry. W7-X (under construction in Germany) and
Heliotron-J (operating in Japan) pursue such alternative approaches to
advanced stellarator design. There is some experimental confirmation
that orbit optimization, using quasi-symmetry or other means,
significantly improves neoclassical confinement. For example HSX has
demonstrated reduced neoclassical losses.

As the only representative of quasi-axisymmetry in the world program,
NCSX is intended to demonstrate the performance of a quasi-axisymmetric
system, and explore the performance consequences of its mix of internal
and external rotational transform. It will demonstrate whether good
confinement, sufficient equilibrium and stability beta limits can be
achieved, specifically with regard to current-driven modes, and whether
the potential for steady-state operation can be achieved simultaneously
by the proper mix of internal and external transform. Because of the
complicated nonlinear interaction between plasma profiles, bootstrap
current and confinement, these are issues considerable scientific and
fusion interest.

Among the advanced stellarators, QAS has two attractive and unique
features. First, the QAS design fits naturally into a low-aspect-ratio
configuration because it requires relatively strong toroidicity compared
to other components of the magnetic field curvature. Thus, the QAS is a
good candidate for a 'compact' (low aspect ratio) stellarator
configuration. Second, confinement studies with QAS would have many
common physics elements to tokamak research. From this aspect, QAS
should produce complementary physics results to tokamak research aimed
at fusion energy development. An important question is whether the
tendency for impurity accumulation is controlled in NCSX by inducing
current-driven core instabilities to prevent it. Finally, when all
systems have been studied in detail, the three major lines -- LHD
(Heliotron), W7-X (optimization outside of quasi-symmetry), and NCSX
will allow us to decide which system has the highest reactor potential.
This information will influence the debate on the continuation of the
fusion program toward a DEMO reactor.

Because sufficient confinement requires a large volume, toroidal systems
deliver fusion power at a level that motivates steady-state operation
from an engineering and grid-integration point of view. Current-driven
tokamaks resort to high bootstrap-current fractions, with the
complications of non-linear interactions between confinement,
equilibrium and stability, NCSX aims to explore these regimes with the
help of external contributions to rotational transform. Thus it should
allow study of the criticality of bootstrap-current based equilibria in
a unique way. For this assessment the low-aspect ratio of NCSX, which is
comparable to that of tokamaks, makes the comparison especially
relevant.

> \(b\) *Given PPPL's proposed plans for operation of the National
> Spherical Torus Experiment and NCSX, what would be the timetable for
> resolving relevant issues identified in (1) above?*

The time scale of fusion development is determined to a large degree by
that of ITER. Major decisions on the direction of DEMO are unlikely to
be made before clear answers are obtained on the critical burning plasma
issues that can only be addressed by ITER, such as stability with
α-particles, burn control and ash removal. When these burning plasma
studies are completed, the stellarator research findings will be needed
to enter into the general debate on how to structure the next steps
beyond ITER. The time scale set by NCSX projects the achievement of
first plasma in 2012 and initial results in 2013. W7-X is scheduled for
first plasma in 2014 and ITER is presently scheduled for operation in
2016. LHD and HSX are operating now and will continue to contribute.

The NCSX team proposed a timetable for the scientific exploration during
the first years including operation in alternate years with NSTX. Since
this schedule extends to a time beyond even the proposed next 5 year
plan for NSTX, it cannot be considered certain. The planned phases of
NCSX device commissioning, preparation of the necessary diagnostics in
line with the major topics to be addressed and the development of the
divertor and the heating periphery are well thought out. The planning
reflects the considerable experience at PPPL on commissioning such
experiments.

The question whether NCSX can indeed meet its proposed resolution of
critical issues with only FY13 and FY15 was discussed in detail by the
committee. Based on the PPPL experience with the comparably sized NSTX
experiment which has a comparable operation budget level as NCSX, a more
likely time frame for resolving the initial set of critical issues is
about 5 years of actual operation, with detailed scientific
understanding and an extrapolable basis for optimization of follow-on
devices requiring about 10 years of experimental operation.

Technical requirements that may extend the time scale for resolving the
initial set of critical issues include achieving (and maintaining)
sufficient quality of the confining flux surfaces. The quality of flux
surfaces depends on symmetry breaking field errors introduced by
tolerance deviations of single components or by errors introduced by
assembly. The project has shown that it follows the development of the
components in detail by calculating the resulting island widths from
resulting mechanical deviations. The project has also developed
strategies how to cope with errors of the components (by compensating it
by slight changes to the geometry of the device during assembly) and by
installation of specific trim coils. Trim coils are also the selected
compensation method on ITER and other stellarators (LHD, W7-X). It is
important that these studies are continued during NCSX assembly. In
addition the Committee recommends that attention to construction details
that may affect flux-surface quality, and the study of their effects and
methods to counteract them, remain top priorities for the project.

Other technical or managerial risks affecting the timetable are not part
of the charge and were not addressed.

> \(c\) *What are the differences of the current NCSX design compared to
> other stellarators operating or being built abroad? What is the
> significance of these differences? Does NCSX fill a critical void in
> the development of the stellarator concept as a viable fusion energy
> system?*

NCSX is designed as quasi-axisymmetric stellarator with low aspect
ratio. In both properties, NCSX is unique. If NCSX were not completed,
both stellarator and tokamak research will suffer. W7-X is optimized
using a different scheme than quasi-symmetry (with superconducting
coils) and all currents in W7-X, apart from the diamagnetic current, are
strongly reduced. In NCSX, with its compact, quasi-axisymmetric
configuration, the bootstrap current is maximal. The comparison between
these two devices will be extremely useful in understanding the physics
optimization of these advanced stellarator configurations. Beyond
obvious criteria (confinement), the stability against current driven
modes, the known differences between tokamaks and stellarators (*e.g.*
the isotopic effect in anomalous confinement), the different flow
pattern and the level of damping will be of extraordinary importance.

With respect to compactness or small aspect ratio, W7-X has a large
aspect ratio, LHD a middle aspect ratio, and NCSX the smallest aspect
ratio. In developing lower aspect ratio approaches in the stellarator
configuration, NCSX clearly plays a significant role. In demonstration
of the potential for steady-state operation, LHD and W7-X are
significant because they employ superconducting magnets. In terms of the
tokamak program benefitting from 3D magnetic configuration physics, NCSX
is also significant because of its quasi-axisymmetry and large bootstrap
driven currents, as discussed above.

**3. Options for the US stellarator program**

a.  *If the NCSX program were not continued, what options would exist or
    would be possible to address the key issues of the quasi-symmetric
    stellarator in general and the compact stellarator in particular?*

In the absence of NCSX, the Committee recommends that the DOE enhance
the remaining US stellarator program to enable the US to continue as a
participant in the worldwide stellarator research program. The present
US stellarator research program includes other devices, planned or in
operation, that could address at various levels a subset of the key
issues listed in Section 1. However, such studies would have to be done
at lower plasma parameters, and at some somewhat less relevant values of
the dimensionless parameters. Examples of such studies are :

-   Effects of strongly reduced effective ripple on energy confinement.

-   Determination of pressure limits in 3D configurations.

-   Disruption stabilization and avoidance.

-   Reduction of turbulent transport by flows and 3D shaping
    optimization.

-   Stabilization of equilibrium islands and tearing modes.

The Committee emphasizes that no US experimental program, present or
planned, could provide the breadth of scientific and technical
information that is expected to come from NCSX. The only PoP scale
device in the US repertoire that addresses quasi-symmetry is NCSX, and
NCSX is the only such device capable of examining the key issues in an
integrated context. Thus, without NCSX there would be no experiment to
address the issues of quasi-axisymmetry and the potential of
lower-aspect ratio stellarators. Furthermore, there would be no way to
study hot-ion and high beta physics in a low-aspect ratio
quasi-symmetric 3D system. NCSX occupies a unique niche in the complex
stellarator design space.

Therefore, if NCSX were abandoned, the US would have to significantly
reduce its ambitions in the quasi-symmetric stellarator research area,
or begin constructing a new PoP stellarator experiment.

The Committee finds it important that the US have a significant
stellarator presence as part of its magnetic fusion energy research
program. The loss of NCSX would have serious negative consequences for
the US and worldwide stellarator research programs. In particular, the
US would lose its world leading position in developing the compact,
quasi-axisymmetric approach to stellarator confinement research. The
Committee notes that at present about 75% of the US stellarator effort
is focused on the construction of NCSX so the loss of NCSX would change
the basic character of the US program. The program would lose its
integrated PoP facility and the most relevant connections to tokamak
research through quasi-axisymmetry.

b.  *Assuming NCSX is not available, what program elements would*

> *be required to maintain the US as a significant participant in the*

*international stellarator program?*

i.  *Identify potential opportunities for US leadership*

ii. *Include more international collaboration as appropriate.*

The US stellarator program has several existing components that make
important contributions to the worldwide stellarator effort. These
activities are addressing selected key issues. In the event that NCSX is
not available, these activities should be strengthened and new
stellarator research opportunities should be explored.

In the absence of NCSX, a restructured US stellarator program could
maintain scientific leadership in selected research topics, but would
have difficulty in playing a significant role in the direction of
worldwide stellarator research. Furthermore, the lack of a domestic PoP
program would diminish the benefits the US could gain from international
collaboration.

Nonetheless international collaboration is a key element to the US
stellarator research effort, as it is to every element of the US fusion
energy science program. With the loss of NCSX, it can be expected that
international collaboration will occupy a larger proportion of the US
effort. In particular the US has the opportunity to participate in
experiments on the LHD device in Japan (currently operating) and the
W7-X device currently under construction in Germany. Although these
devices at not low-aspect ratio, they will provide critical information
on stellarator plasmas at higher density and plasma temperatures, higher
beta and steady-state operation. The US would seek to expand its
opportunities to study 3D physics on LHD and W7-X.

Theory and computation research in the US has developed significantly in
recent years and developed and employed a number of world-class
numerical tools. To a large degree, this resurgence in US stellarator
theory is due to the NCSX and QPS design programs. There have been a
number of recent advances in the theory of magnetic surface fragility,
3D MHD equilibrium and stability, transport, concept improvement and
reactor optimization. Opportunities exist to strengthen this work in
areas such as high-beta and high-density operation of stellarators,
micro instabilities in 3D configurations, zonal flows and flow damping
and simplification of future devices and reactor concepts. However, the
loss of a world-class stellarator experiment in the US would make it
more difficult to attract young theorists to specialize in the area of
3D magnetic confinement research.

The US has the only operating quasi-symmetric stellarator in the world,
the HSX at the University of Wisconsin-Madison. Because of its
quasi-helical symmetry and very low ripple, HSX has a very high
effective transform that is responsible for very narrow banana widths,
reduced Pfirsch-Schlüter and bootstrap currents and low neoclassical
transport. With additional diagnostics and heating capabilities, HSX can
address issues of turbulent transport and zonal flows, confinement
scaling, plasma stability, low collisionality ion transport, energetic
particle confinement and impurity transport.

The CTH device at the University of Auburn investigates the stability of
current-driven discharges, from tokamak-like ranges of vacuum transform
near zero to values of transform characteristic of NCSX. Furthermore,
CTH evaluates the effects on equilibrium and stability of magnetic
islands and error fields in helical configurations in which the
rotational transform is not tightly prescribed, as in NCSX. Improved
support for reliable electron temperature profile and current profile
diagnostics would directly add to the effectiveness of this research
program.

The proposed QPS device at the Oak Ridge National Laboratory is a
low-aspect ratio quasi-poloidal symmetric configuration that
approximates linear linked mirrors with end losses in a toroidal
geometry. It may allow large poloidal flows and can potentially study
the effects of flow and flow shear on plasma turbulence. The physics
program of QPS would connect to higher-aspect ratio stellarator devices
like W7-X. QPS would extend the stellarator database to very low-aspect
ratio, similar to what the ST does for the tokamak database. However,
while QPS would have an important role in the world stellarator program,
it would not be able to replace the scope of the NCSX research program.
In particular QPS could not address the assessment of quasi-axisymmetry
or the close link to tokamak behavior.

The Committee did not evaluate in detail the merits of the QPS device,
which is currently in an R&D and prototype-fabrication stage. Thus the
Committee cannot judge whether the DOE should proceed with the
construction of QPS. The Committee notes that it would seem illogical to
cancel a stellarator project nearing the final stages of construction
only to begin a new compact stellarator with poloidal rather than
toroidal quasi-symmetry. However, in the situation where NCSX is not
available, the Committee believes that the DOE should expedite the
decision on the construction of QPS.

The Committee also recognizes that it might be possible to consider
adding concept-exploration level stellarator experiments to the US
program. Potentially, such devices could pursue the quasi-axisymmetric
optimization path. However the Committee did not receive any specific
suggestions for such an undertaking nor did the Committee have time to
carefully explore such possibilities.

In the absence of NCSX, the US stellarator program could pursue
stellarator concepts outside of the compact quasi-symmetric path.
Quasi-symmetry is one of many ways to optimize 3-D configurations; other
optimization schemes could be pursued. Without the presence of NCSX, the
US stellarator program should consider a variety of approaches to
stellarator optimization in proposing a new PoP stellarator project.

**Appendix A: Charge to FESAC**

August 9, 2007

Professor Stewart C. Prager, Chair

Fusion Energy Sciences Advisory Committee

Department of Physics

University of Wisconsin

1150 University Avenue

Madison, Wisconsin 53706

Dear Professor Prager:

The National Compact Stellarator Experiment (NCSX) project, which is
being built at the Princeton Plasma Physics Laboratory (PPPL), is
projecting substantial cost (\~\$40 million) and schedule (\~2 year
delay) overruns. These overruns are large enough to add new burdens on
the limited resources of the U.S. fusion energy sciences program, as
well as undermine confidence of the Administration and Congress in the
ability of the Office of Fusion Energy Sciences and the Office of
Science to manage large and technically challenging construction
projects. Given the magnitude of the increases projected for NCSX, all
options, including termination of the project, must be considered. In
that context, we would like the Fusion Energy Sciences Advisory
Committee (FESAC) to conduct a scientific and programmatic review
focused on evaluating the NCSX program and its potential effect on the
U.S. fusion energy sciences program. Below is a list of questions that
we believe must be answered in order to allow us to make a decision on
the best course of action for the U.S fusion energy sciences program.
This review will comprise part of the set of reviews that will be
conducted to inform a decision.

**Questions for Scientific and Programmatic Review of NCSX:**

1.  Critical scientific issues for the U.S. compact stellarator program:

    a.  What unique toroidal fusion science and technology issues can a
        compact stellarator program address, independent of its
        potential for a reactor concept?

    b.  What are the advantages and disadvantages of the quasi-symmetric
        stellarator as a potential fusion system concept? What unique
        features does the compact stellarator offer in this regard?

    c.  What scientific and technical issues need to be resolved to
        evaluate the compact stellarator as a viable concept for a
        fusion energy system?

2.  Role of NCSX in the international context:

    a.  What critical, unique contributions does NCSX potentially offer
        for addressing the issues identified in (1)?

    b.  Given PPPL's proposed plans for operation of the National
        Spherical Torus Experiment and NCSX, what would be the timetable
        for resolving relevant issues identified in (1) above?

    c.  What are the differences of the current NCSX design compared to
        other stellarators operating or being built abroad? What is the
        significance of these differences? Does NCSX fill a critical
        void in the development of the stellarator concept as a viable
        fusion energy system?

3.  Options for the U.S. stellarator program:

    a.  If the NCSX program were not continued, what options would exist
        or would be possible to address the key issues of the
        quasi-symmetric stellarator in general and the compact
        stellarator in particular?

    b.  Assuming NCSX is not available, what program elements would be
        required to maintain the U.S. as a significant participant in
        the international stellarator program?

        i.  Identify potential opportunities for U.S. leadership

        ii. Include more international collaboration as appropriate.

4.  Role of the stellarator and NCSX in the long-term U.S. fusion energy
    sciences program:

    a.  For a compact stellarator to be a viable reactor concept, what
        other experimental facilities would be required to develop the
        required knowledge base?

    b.  For the cases with and without NCSX in the program, how can
        results from the U.S. stellarator program impact the direction
        and/or risk level of the development of the knowledge-base
        needed for a fusion energy system:

        i.  On the timescale for a first-generation DEMO after ITER?

        ii. Longer-term, beyond a first-generation DEMO?

In summary, FESAC should answer all of these questions and provide their
responses so we can evaluate the situation and choose the most
appropriate course of action. Given the urgency of the situation, we
would appreciate it if your answers could be provided by the scheduled
FESAC meeting in October 2007. I very much appreciate your assistance in
addressing these questions on such an expedited basis.

Sincerely,

/s/

Raymond L. Orbach

Under Secretary for Science

**Appendix B: Members of the NCSX Review Committee**

Dr. Charles Baker, Sandia National Laboratories (consultant)

Prof. Richard Hazeltine, University of Texas at Austin (Chair)

Prof. Chris Hegna, University of Wisconsin

Dr. Timothy Luce, General Atomics

Prof. Gerald Navratil, Columbia University

Prof. Shoichi Okamura, National Institute for Fusion Science (Japan)

Prof. Ron Parker, Massachusetts Institute for Technology

Dr. Max Tabak, Lawrence Livermore National Laboratory

Dr. Joseph Talmadge, University of Wisconsin

Prof. Dr. Friedrich Wagner, Max-Planck-Institut für Plasmaphysik
(Germany)