## Fusion Energy Sciences  {#fusion-energy-sciences .unnumbered}

#### David P. Schissel {#david-p.-schissel .unnumbered}

#### DIII-D National Fusion Facility {#diii-d-national-fusion-facility .unnumbered}

#### schissel@fusion.gat.com {#schisselfusion.gat.com .unnumbered}

### Science Area Summary

The long--term goal of magnetic fusion research is to develop a reliable
energy system that is environmentally and economically sustainable. To
achieve this goal, it has been necessary to develop the science of
plasma physics, a field with close links to fluid mechanics,
electromagnetism, and nonequilibrium statistical mechanics. Nuclear
fusion, the power source of the stars, has been the subject of
international research since its worldwide declassification in the late
1950s \[1\]. As a result of the highly collaborative nature of Fusion
Energy Sciences (FES) research combined with a few experimental
facilities and a computationally intensive theoretical program, the
community is facing new and unique challenges.

FES research is a worldwide effort conducted at some 90 sites in the
United States, 60 in Europe, 40 in Japan, and several each in South
America, China, and Australia. Fusion experiments have a dual role:
providing data for the advancement of plasma science and increasing
plasma parameters (densities, temperatures, etc.) toward the levels that
would be needed in a power production reactor. In the United States,
experimental magnetic fusion research is centered at three large
facilities (Alcator C--Mod, DIII--D, NSTX \[2,3,4\]) with a present day
replacement value of over \$1B; clearly too expensive to duplicate. As
these experiments have increased in size and complexity, there has been
concurrent growth in the number and importance of collaborations between
large groups at the experimental sites and smaller groups located at
universities, industry sites, and national laboratories.

Teaming with the experimental community is a theoretical and simulation
community whose efforts range from the applied analysis of experimental
data to more fundamental theory like the creation of realistic
non--linear 3D plasma models. The development of a science-based
predictive capability for fusion-relevant plasmas is a challenge central
to fusion energy science, in which numerical modeling has played a vital
role for more than four decades. A combination of the wide range in
temporal and spatial scales, the extreme anisotropy, the importance of
geometric detail, and the causality requirement make it impossible to
parallelize computation over time. Modeling of this problem is one of
the most challenging tasks in computational physics. Computation and
simulation are critical to progress in the field both to enable
scientific understanding, and to design and interpret new experimental
devices containing burning, reactor grade plasmas.

Recognizing the important role computer science plays in the success of
fusion energy research, the SciDAC initiative \[5\] funded high--end
computational fusion projects and a collaboratory project \[7\]. These
projects are creating new simulation capabilities, creating and
deploying a fusion computational and data Grid, new and innovative
collaborative visualization capabilities, and impressive capabilities
for remote control room participants.

### Challenges, Priorities and Requirements

Magnetic fusion experiments operate in a pulsed mode, producing plasmas
up to 10 seconds duration every 10 to 20 minutes, with 25 to 35 pulses
per day. For each plasma pulse, up to 10,000 separate measurements
versus time are acquired, representing about a gigabyte of data.
Throughout the experimental session, hardware and software plasma
control adjustments are discussed by the experimental team and made as
required to optimize the use of the available experimental time. The
experimental team is typically 20 to 40 people, with many participating
from remote locations. Decisions regarding changes to the next plasma
pulse are informed by data analysis conducted during the roughly 15
minute between pulse intervals. Unlike large experimental collaborations
in other fields, such as high-energy or nuclear physics which operate
essentially in a "batch" mode, fusion experiments put a premium on near
real-time interactions with data and among members of the team. This
mode of operation requires rapid data analysis that can be assimilated
and debated in near real time by a geographically dispersed research
team.

Experimental fusion energy research will be greatly enhanced by
facilitating more, and more complex, between pulse data analysis
combined with the ability to effectively utilize the increased
information flow. A more informed decision on the next plasma pulse can
lead to higher quality science and therefore accelerated progress. The
cyclical nature of experimental fusion research has been termed the
collaborative control room. To be fully functional, the collaborative
control room requires (1) secured computational services that can be
scheduled as required, (2) the ability to rapidly compare experimental
data with simulation results, (3) a means to easily share individual
results with the group by moving application windows to a shared
display, and (4) the ability for remote scientists to be fully engaged
in experimental operations through shared audio, video, and
applications. The National Fusion Collaboratory Project has created
prototypes of different pieces of the collaborative control room that
are being tested and used in present day FES research. This work has
demonstrated the value of implementing such a capability.

As specified in the USDOE Facilities for the Future Report \[38\], the
highest priority for the Office of Science is the International
Thermonuclear Experimental Reactor (ITER), an international
collaboration to build the first fusion science experiment capable of
producing a self-sustaining fusion reaction. This \$5B device, which
will be built outside the United States, is expected to be operational
by the middle of the next decade and would produce fusion power at the
level of an industrial power plant. The importance and cost of this
device requires that it operate at the highest possible level of
scientific productivity. In this sense, it is useful to think of ITER as
the largest and most expensive scientific instrument ever built for
fusion research.

The ITER device will be a unique collaboration for the fusion program,
involving very large numbers of scientists from many different
countries. It is reasonable to assume that not all members of the
experimental team will be on-site for all experiments. In fact, it is
probably desirable and practical to carry out a significant amount of
the scientific work remotely. Effective international collaboration on
this scale is a technically demanding problem since it requires the
presentation of a working environment to off-site personnel for
experimental operations that is every bit as productive and engaging as
when they are physically in the control room. Thus, a fully functional
and implemented collaborative control room is required for the success
of the ITER project and to maximize the value of ITER to the U.S.
program. The technologies needed for ITER will push the frontiers of
data acquisition, data management, visualization, and remote
participation and will be significant to a broad range of other
scientific research disciplines.

The second highest priority in the USDOE Facilities for the Future
Report is Ultra Scale Scientific Computing Capability. This capability
is expected to increase the computing capability available to fusion
energy, by a factor of 100. The proposed Fusion Simulation Program (FSP)
has the goal in the next decade of reliably predicting the behavior of
plasma discharges in a toroidal magnetic fusion device on all relevant
time and space scales; a fully integrated simulation. The long-term goal
is in essence the capability to carry out "virtual experiments" of a
burning magnetically confined plasma through faithful representation of
the salient physics process of the plasma. One key to the success of the
FSP will be effective collaboration between fusion scientists and
computer scientists, between fusion simulation scientists specializing
in different plasma regimes, and between fusion simulation and
experimental scientists. Thus the collaborative technology that is
critical for the success of the experimental science program is equally
critical to the success of the simulation science program.

### A Vision for the Future of Fusion Energy Sciences

With the successful creation and deployment of collaboration technology,
the future working environment for fusion scientists in the United
States will be substantially enhanced. The first plasma for ITER is
scheduled around 2015. One can imagine a U.S. based scientist remotely
participating in real-time in experimental operations. Audio and video
from the control room is seamlessly available to the scientist's desktop
where it is easy to follow the 30 minute plasma cycle. Data from ITER is
available locally and remotely concurrently. The scientist can analyze
in detail the most recent ITER discharge and participate in the planning
for the next plasma pulse through communication her findings back into
the control room. This communication takes the form of audio, video, and
a shared visualization so that her findings can be debated and discussed
amongst the experimental team members including those physically located
in the control room. During times of non-operation, this remote
scientist can actively participate in detailed working meetings that
include interactive data analysis sessions and also give and attend
technical seminars.

To help achieve the 10-year goal of an integrated simulation, a
scientist working on the FSP will need an enhanced working environment
like that of their experimental colleagues. Detailed remotely held
working meetings including shared code debugging and shared
visualization for discussion of results should become routine. In
addition, a closer collaboration between the experimental and simulation
scientists will be developed. For experimental science including ITER,
simulations can be used to predict experiments through close
collaboration between experimental and theoretical scientists.

Creating an enhanced collaborative environment for fusion research
within the next decade is critical to the success of the U.S. fusion
program. With ITER's construction outside of the United States,
effective remote participation is the only way that the U.S. program
will remain vital and keep pace with that of Europe, Japan, China, South
Korea, and Russia. By leading the way in collaborative technology in the
next decade, the U.S. can work to assure substantial and beneficial
involvement in fusion's next generation experimental program.

### References

\[DMW\] DOE Data-Management Workshop Series
http://www-conf.slac.stanford.edu/dmw2004/

\[NCwebsite\] The DOE National Collaboratories Program.
<http://www.doecollaboratories.org/>

\[NC2004\] National Collaboratories 2004 meeting.
<http://www-fp.mcs.anl.gov/nc2004/>

**POINTS OF CONTACT FOR QUESTIONS/MORE INFORMATION:**

**Larry Rahn, SNL**

**Deb Agarwal, LBNL**

**Workshop Organizers**

**nc-organizers@george.lbl.gov**

Dr. Larry A. Rahn Senior Scientist

Sandia National Labs rahn@sandia.gov

PO Box 969 MS 9051 Phone (925)294-2091

Livermore, CA 94551-0969 Fax(925)294-2595

Secretary: Melanie Steadman (mestead@sandia.gov)

Ph(925)294-4947 Fax(925)294-2276

Deb Agarwal e-mail:DAAgarwal@lbl.gov

MS50B-2239 phone :(510)486-7078

Lawrence Berkeley National Lab URL: http://www-itg.lbl.gov/\~deba

Berkeley, CA 94720