Presented to FESAC by
Farrokh Najmabadi
on behalf of
The FESAC/SCICOM Alternative Concept Panel:
July 16, 1996
Dr. Farrokh Najmabadi (Chair) University of California, San Diego Dr. James Drake University of Maryland Dr. Jeffrey Freidberg Massachusetts Institute of Technology Dr. David Hill Lawrence Livermore National Laboratory Dr. Michael. Mauel Columbia University Dr. Gerald Navratil Columbia University Dr. William Nevins Lawrence Livermore National Laboratory Dr. Masayuki Ono Princeton Plasma Physics Laboratory Dr. Stewart Prager University of Wisconsin, Madison Dr. Marshall Rosenbluth University of California, San Diego Dr. Emilia Solano* University of Texas, Austin Dr. Ronald Stambaugh General Atomics Dr. Yuichi Takase Massachusetts Institute of Technology Dr. Kenneth Wilson Sandia National Laboratories
CONSULTANTS: Dr. Osamu Motojima National Inst. for Fusion Studies, Japan Dr. Tom Todd UKAEA Government Division, Fusion Dr. Friedrich Wagner IPP Garching
*Dr. Solano resigned from the Panel before this report was completed.
In order to focus the discussion, Panel distributed a set of standard questions for each concept and proponents provided a written "assessment" paper for each concept.
The Panel maintained a World Wide Web site for the panel activities. The Panel actively solicited input and received many written comments and assessment papers. Full text of this community input can be found on the Web site:
http://aries.ucsd.edu/SCICOM/AC-PANEL/index.html
The Panel deliberations were also guided by the FESAC January 1996 report, "A restructured Fusion Energy Sciences Program," and by the FEAC Panel 3 report on "Concept Improvement" (1992).
Fusion research has historically pursued many configurations. In late 1960's the tokamak proved to have a superior confinement and became the focus of the worldwide program.
Programmatic distinction between "mainlines" and "alternatives" was put in a place in U.S. to "protect" the alternative concepts and maintain the program breadth. Up to late 1980's, a healthy but modest level of research in alternatives was carried out in U.S.
In fall of 1990, the alternative concepts program was essentially terminated.
In 1992, the OFES was re-evaluating this decision. FEAC Panel 3 report notes a miscommunication between community and OFES as the community believed that alternative concept research has a low priority and will not be supported.
Alternatives and tokamaks are viewed by OFES and part of the community as "competitors" rather than complimentary.
This ignores the strong connection between most magnetic confinement approaches and the research techniques they share. Examples of past discoveries of significance to tokamaks and fusion plasma physics includes the discovery of bootstrap current, development of neutral beam heating, to name a few.
In fact, a fusion power plant will likely draw on the broad-based physics foundation that comes from experimental and theoretical studies in a variety of plasma confinement approaches including alternative concepts.
OFES and the community should strive to remove any programmatic and cultural distinction between confinement concepts and alternatives. The decision to expand and/or reduce the research effort in any concept should be solely based on its contribution to the goals of the fusion program and evaluation specific proposals.
2) Advancement of fusion plasma physics;
3) Contribution to fusion energy development;
4) Development of candidates for fusion power plants.
Potential as an attractive fusion power plant should not be used as a litmus test for fusion concepts that are at early stages of development because (1) the large extrapolation required for such an assessment makes these tests arbitrary and meaningless, and (2) some concepts may prove to be unattractive as power plants but my contribute significantly to understanding key issues.
In early stages, the major benefits are in the first two criteria. At later stages, the emphasis shifts towards the latter two.
Many independent experiments and theory activities are preferred. High risk, large payoff research is desirable. Activities should be of short duration in order to allow for a high turnover rate.
Proof-of-Principle. This is the lowest-cost program aimed at developing an integrated and broad understanding of basic scientific aspects of a concept which can be scaled with great confidence. Requires at least one device with plasma of sufficient size and performance that can examine a range of physics issues. Key physics and technological issues for the concept should be identified at this stage.
Programs are about 8-10 years of duration. and should be national programs. Sufficient resources should be committed both to large experiment as well as supporting smaller experiments, theory and modeling, and power plant studies in order to ensure a healthy return on investment.
At this stage, the physics of concept is refined, new physics in fusion-relevant regime is examined and the performance is optimized.
Fusion Energy Development. Aims at developing the technical basis for advancing to the power plant level at full fusion environment. It include devices such as ignition experiments and volume neutron source.
Fusion Demonstration Power Plant. Aims at convincing the electric power producers, industry, and the public that fusion is ready for commercialization.
This parallels process used in parts of NSF and NIH.
It represents an experiment in community governance and can be extended to cover all concepts if successful. (initially charged to oversee alternative concepts.)
We recommend that SciCom to be charged at act as CDP.
2) The OFES organizes a peer review of these proposals with at least one member of CDP participating in each review.
3) The CDP meets once or twice a year to rank proposals which are peer-reviewed during the previous period.
4) The CDP ranks the new and renewal proposals and provide a consensus recommendation to FESAC and DOE as to which should receive funding and at what level so as the maintain the desired emphasis among different approaches to Concept Development.
5) The CDP maintains a set of assessment papers on various concepts including research plans, list of critical issues, and a historical record of progress for each concept.
2) The OFES organizes peer reviews of these proposals as is the case now, with at least one member of CDP participating in each review. The outcome of these reviews should be passed to CDP.
3) The CDP reviews these proposals and will provide a scientific assessment of each. The CDP will also provide recommendation for an implementation strategy or strategies depending on available funding. The goal will be to craft a Proof-of-Principle program that obtains the complete resolution of the issues. In some cases, it may be found that the proposals brought forward are collectively deficient in leaving some subsets of the issues unaddressed, the CDP will note these in its report and advise if further proposal solicitations are recommended.
Growing data base from concept-exploration experiments that confinement in ST is "tokamak-like" and no physics show stoppers to proceeding to next stage has been found.
It appears that a large body of tokamak theoretical and experimental data base help provide a basis for next-step ST experiments.
Benefits. Research in ST can make important contribution to resolve key issues of conventional tokamaks because the ST concepts pushes the tokamak physics to the limit of extreme toroidicity. The ST research fits well with the U.S. emphasis on tokamak concept optimization. It is a financially realistic niche. Preliminary analysis indicates that ST with small size may be possible as fusion devices. However, technological issues such as design for center-post, divertor heat removal, and wall-loading limitations may limit the performance of a ST and set the optimum parameters.
Program Mix. A proof-of-principle experiment, with a broad, community-wide support program in theory/modeling, power plant studies as well small concept-exploration-class experiments.
Benefits. Stellarators are a strong driver of 3-D plasma physics and help define the possibilities and limitations of toroidal confinement systems.
Program Mix. In view of the planned operation of two large proof-of-performance-class devices world-wide (LHD and W7-X), there is little motivation for the U.S. to build similar scale devices. U.S. can play a valuable role at the concept exploration level focusing the effort on reducing the size of stellarator fusion power systems. Possibility exists for additional interesting experiments in the proof-of-principle class.
In order to maintain beneficial contact with the large stellarator efforts abroad and to gain knowledge from those important experiments, the U.S. should (1) seek to gain a support role on LHD and W7-X, (2) seek to provide substantial theory support to LHD and W7-X. This core of theory support could also stimulate concept exploration initiatives.
Program Mix. Most of the RFP proof-of-principle issues can be addressed in existing facilities. The program should include: (1) A broader experimental investigation of advanced RFP issues, such as profile control within the US program; (2) Increased collaboration with the RFX device in Italy; (3) Increased support for RFP theory and computation.
Spheromak is at the concept exploration stage of development. Considerable experimental data already exists in short-duration experiments where equilibrium & stability is passively provided by a close-fitting conducting boundary. Demonstrating reasonable confinement in experiments where the equilibrium & stability is controlled by externally imposed magnetic fields remains as an important milestone for concept exploration. Addressing next-step spheromak issues will require at least one new experiment that can achieve high-temperature in quasi-steady state.
Others. The Panel also heard presentations on many less-developed concepts. These presentations clearly demonstrated to us that there exists a large number of interesting and intriguing ideas to be studied at concept exploration level.
A healthy alternative concept program require an increase in funding as proposed in the FY 97 Presidential budget and should include (not in priority order):