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Executive Summary

The purpose of this assessment of the fusion energy sciences program of the Department of Energy's (DOE's) Office of Science is to evaluate the quality of the research program and to provide guidance for the future program strategy aimed at strengthening the research component of the program. 1 The committee focused its review of the fusion program on magnetic confinement, or magnetic fusion energy (MFE), and touched only briefly on inertial fusion energy (IFE), because MFE-relevant research accounts for roughly 95 percent of the funding in the Office of Science's fusion program. Unless otherwise noted, all references to fusion in this report should be assumed to refer to magnetic fusion.

Fusion research carried out in the United States under the sponsorship of the Office of Fusion Energy Sciences (OFES) has made remarkable strides over the years and recently passed several important milestones. For example, weakly burning plasmas with temperatures greatly exceeding those on the surface of the Sun have been created and diagnosed. Significant progress has been made in understanding and controlling instabilities and turbulence in plasma fusion experiments, thereby facilitating improved plasma confinement—remotely controlling turbulence in a 100-million-degree medium is a premier scientific achievement by any measure. Theory and modeling are now able to provide useful insights into instabilities and to guide experiments. Experiments and associated diagnostics are now able to extract enough information about the processes occurring in high-temperature plasmas to guide further developments in theory and modeling. Many of the major experimental and theoretical tools that have been developed are now converging to produce a qualitative change in the program's approach to scientific discovery.

The U.S. program has traditionally been an important source of innovation and discovery for the international fusion energy effort. The goal of understanding at a fundamental level the physical processes governing observed plasma behavior has been a distinguishing feature of the program. This feature, a strength of the program, was formalized in the 1996 restructuring, with the new emphasis on



1 Because OFES funding so dominates the funding of plasma science in the United States, this report uses the terms “fusion science,” “plasma physics,” “plasma science,” and “the fusion program” interchangeably.



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Page 1 Executive Summary The purpose of this assessment of the fusion energy sciences program of the Department of Energy's (DOE's) Office of Science is to evaluate the quality of the research program and to provide guidance for the future program strategy aimed at strengthening the research component of the program. 1 The committee focused its review of the fusion program on magnetic confinement, or magnetic fusion energy (MFE), and touched only briefly on inertial fusion energy (IFE), because MFE-relevant research accounts for roughly 95 percent of the funding in the Office of Science's fusion program. Unless otherwise noted, all references to fusion in this report should be assumed to refer to magnetic fusion. Fusion research carried out in the United States under the sponsorship of the Office of Fusion Energy Sciences (OFES) has made remarkable strides over the years and recently passed several important milestones. For example, weakly burning plasmas with temperatures greatly exceeding those on the surface of the Sun have been created and diagnosed. Significant progress has been made in understanding and controlling instabilities and turbulence in plasma fusion experiments, thereby facilitating improved plasma confinement—remotely controlling turbulence in a 100-million-degree medium is a premier scientific achievement by any measure. Theory and modeling are now able to provide useful insights into instabilities and to guide experiments. Experiments and associated diagnostics are now able to extract enough information about the processes occurring in high-temperature plasmas to guide further developments in theory and modeling. Many of the major experimental and theoretical tools that have been developed are now converging to produce a qualitative change in the program's approach to scientific discovery. The U.S. program has traditionally been an important source of innovation and discovery for the international fusion energy effort. The goal of understanding at a fundamental level the physical processes governing observed plasma behavior has been a distinguishing feature of the program. This feature, a strength of the program, was formalized in the 1996 restructuring, with the new emphasis on 1 Because OFES funding so dominates the funding of plasma science in the United States, this report uses the terms “fusion science,” “plasma physics,” “plasma science,” and “the fusion program” interchangeably.

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Page 2 establishing the knowledge base for fusion energy. 2 An essential tool to unravel the complexities of plasma dynamics is a strong theory program. For several decades, the United States has played a dominant role in plasma theory. The quantitative detail in which experiments are designed and executed in the United States has become a benchmark for the rest of the world. However, the close interaction between the U.S. and international programs since the 1950s makes it difficult to separate the U.S. contributions from those of other countries. Mutual reinforcement of theory and experiment, strong international leadership, and discovery of fundamental principles are hallmarks of a successful scientific enterprise. The committee concludes, therefore, that the quality of the science funded by the United States fusion research program in pursuit of a practical source of power from fusion (the fusion energy goal) is easily on a par with the quality in other leading areas of contemporary physical science. However, in spite of the high quality of the science being carried out, some serious demographic and sociological problems—caused in part by programmatic emphasis and in part by organizational structures—must be addressed. As outlined in the interim report 3 of the committee, there is a history of intellectual interchange between the fusion plasma community and the broader scientific community. Nevertheless, the increasing focus on the fusion energy goal prior to 1996 gradually caused the fusion program to become too inward looking and therefore intellectually isolated from the rest of science— fusion science was not seen as a generator of ideas impacting other scientific disciplines. While many of the scientific challenges that must be overcome in pursuit of the energy goal are sufficiently important to have a potentially broad impact on other branches of science, most scientists funded by the program do not actively participate in the wider scientific culture. As a result, the flow of scientific information out of and into the field is weak. New ideas and techniques developed in allied fields are slow to percolate into the program. Nor is the high-quality science in the program widely appreciated outside the field. Indeed, the broader scientific community holds a generally negative view of fusion science. This isolation, combined with the generally negative perception of the field, is reducing the number of universities and laboratories where plasma and fusion science is being studied to a degree that endangers the future of plasma science. The proportion of the program based on open, competitive, peer-reviewed grants is small, which discourages the entry of new talent into the field and further increases the isolation. The committee believes that a dynamic, outward-looking, science-driven program in which discoveries are regularly communicated beyond the walls of fusion science is essential to alter the outside community's perception of the field. A strong case can also be made that a program organized around critical science goals will also maximize progress toward a practical fusion power source. Scientific discoveries that a decade ago would have been unthinkable are the fundamental drivers of program direction at all levels (see the third finding in Chapter 2 ). Thus, scientific discovery is inherently coupled with progress toward fusion, and the two should not be considered opposing forces. 2 In 1996, the goal of the fusion program as a schedule-driven energy-development program was altered to reflect a longer term strategy for developing and deploying fusion energy sources. The central goal of the restructured program is to establish the knowledge base needed for an economically and environmentally attractive fusion energy source. See Department of Energy (DOE), Fusion Energy Advisory Committee. 1996. A Restructured Fusion Sciences Program. Washington, D.C.: DOE. 3 National Research Council, Fusion Science Assessment Committee. 1999. Interim Report. Washington, D.C.: National Academy Press.

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Page 3 PRIMARY RECOMMENDATIONS The committee makes seven primary recommendations, which address important concerns about the future of the fusion science effort. The findings are summarized in this chapter and explained in full at the end of Chapter 2 , Chapter 3 , and . Those chapters also contain secondary recommendations, which are more specific than the primary recommendations. Recommendation 1. Increasing our scientific understanding of fusion-relevant plasmas should become a central goal of the U.S. fusion energy program on a par with the goal of developing fusion energy technology, and decision making should reflect these dual and related goals. Since the redirection of the fusion program in 1996, a greater emphasis has been placed on understanding the basic plasma dynamics underlying the operation of the various confinement configurations. The new emphasis on exploring scientific issues has been effectively implemented on individual experiments. However, at the programmatic level, performance goals rather than overarching scientific goals continue to act as the primary driver for the allocation of resources. (See Chapter 3 for further discussion.) This emphasis is reflected, for example, in the categorization of experiments as concept exploration, proof of principle, and performance extension, which appears to measure the reactor potential of an experiment rather than its scientific merit—there is no parallel measure of scientific worth. Given the significant historical impact of scientific discovery on the program, the absence of a science-based strategic planning process is inhibiting progress. DOE, in full consultation with the scientific community, needs to define a limited set of important scientific goals for fusion energy science and should formulate concrete and specific strategies to achieve each goal. The committee understands that such a planning process is under way, but it is premature to make a judgement about this new endeavor. The accomplishment of the scientific goals should serve as a metric of the program's success and should have the same weight as performance, which is now the primary measure of progress. Progress in our scientific understanding of fusion-relevant plasmas and progress toward fusion energy are coupled, and both should serve to assess the program. The program planning and budget justification carried out by DOE must be organized around answering key scientific questions in fusion-relevant plasmas as well as around progress toward the eventual energy goal. This recommendation applies to the confinement configuration program and to other programs of a more general nature. Public and congressional advocacy should insist on progress in science as well as progress toward a practical source of fusion power. Recommendation 2. A systematic effort to reduce the scientific isolation of the fusion research community from the rest of the scientific community is urgently needed. Program planning, funding, and administration should encourage connectivity with the broad scientific community. The community of fusion scientists should make a special effort to communicate its concepts, methods, tools, and results to the wider world of science, which is largely unaware of that community's recent scientific accomplishments. Increased connectivity will also facilitate the transfer of new ideas and techniques into the program from allied fields, enhancing the ability of the program to maximize the rate of scientific discovery. There are numerous examples in federally funded research programs of formal coordination mechanisms having been established among related programs in different agencies. In some instances this

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Page 4 coordination can optimize the use of funding. Perhaps more significant, the dialogue among the leaders of these government research programs can encourage interactions among the various scientific communities, foster joint undertakings, and raise the visibility of the discipline as a whole. Recommendation 3. The fusion science program should be broadened in terms of both its institutional base and its reach into the wider scientific community; it should also be open to evolution in its content and structure as it strengthens its research portfolio. The committee is convinced that the opportunity to understand the plasma physics underlying fusion is expanding because of the closer connection between theory and experiment and the great improvements in diagnostics and numerical simulation. To enrich the pool of ideas that will feed this progress, it will be essential to enlarge the sphere of awareness of the critical problems facing the field and to bring in new talent, both individual and institutional. The broadening of the fusion science effort can be approached in a number of ways. One approach would be to set up competitive funding opportunities of sufficient magnitude to elicit responses from potential new institutional participants. The creation of centers of excellence in fusion science (proposed below) and the greater involvement of the National Science Foundation in fusion and plasma science would also broaden the institutional base of fusion science. A larger proportion of fusion funding should be made available through open, well-advertised, competitive, peer-reviewed solicitations for proposals. Fusion program peer review could involve scientists from outside the fusion community where appropriate. The evaluation and ranking of proposals by panels that include individuals with appropriate expertise in allied fields would broaden the intellectual reach of the grant review process. Plasma science research that is not immediately related to the fusion energy goal should play a more influential role in the DOE fusion program. More plasma science could be included in DOE's fusion science portfolio by having a program element for general plasma science. This program element should award individual investigator grants on a competitive, peer-review basis. A small fraction of the present DOE program addresses this need (see Appendix B ), but its role and visibility should be increased. Such funding would encourage new interchanges that enrich fusion science. To ensure that increasing institutional diversity is a continuing goal, the committee recommends that the breadth and flexibility of participation in the fusion energy science program be a program metric. Recommendation 4. Several new centers, selected through a competitive, peer-review process and devoted to exploring the frontiers of fusion science, are needed for both scientific and institutional reasons. Many of the issues in fusion science are now of sufficient complexity that they require closely interacting, critical-mass groups of scientists to make progress. For example, understanding the dynamics of plasma turbulence and transport requires the development of appropriate physical models and computational algorithms for treating disparate space- and timescales, as well as complex magnetic geometries, efficient programming on massively parallel computing platforms, and an understanding of nonlinear physics (energy cascades, intermittency, phase transitions, avalanches) and other topics. Tight coupling with a parallel experimental effort is required to challenge theoretical predictions. No single scientist and no small collaboration of practicing scientists has the breadth of knowledge required to tackle such large and complex problems. In the area of theory and computation, the absence of closely interacting teams of critical mass is inhibiting the successful attack on a number of central

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Page 5 science issues confronting the fusion research program. The loose collaborations that have been periodically established by the program have generally not been successful in establishing the close working relationships required to address the most challenging topics. The new centers (“centers of excellence”) could create a new focus on scientific issues for the U.S. fusion program. A center could serve as a node for a distributed network of close collaborators or it could undertake scientific explorations of significant magnitude at one site, or it could do both. The centers could marry the expertise and approaches of national labs and universities around the country. They should have a number of programmatic and structural features so that they can play their appropriate role in addressing the critical problems of the field. Among these features should be the following: A proposal for a center should have a plan to identify, pose, and answer scientific questions whose importance is widely recognized. One size cannot meet all scientific challenges. The committee envisions a center comparable in size to the current centers sponsored by the National Science Foundation (NSF), which have operating costs of $1 million to $5 million per year, although the size should ultimately be determined by the proposal process. Some centers may need on-site experimental facilities, and some may need only computing facilities and access to larger national computer centers. A team of between four and six coinvestigators with broad expertise and connections to other research groups and laboratories should form the core of the center's personnel. This team should be augmented by a similar number of temporary research staff (funded, at least in part, by the center) and an appropriate number of support staff. The center should enable links to various scientific disciplines, including physics, mathematics, and computer science, depending on the problem it is focusing on. It should have a plan for bringing practitioners of other disciplines from other institutions into the fusion community and should make the community's experimental resources more widely available. The institutions housing or participating in such centers should make a commitment to add faculty or career staff, as appropriate, in plasma/fusion science and/or related areas. The centers should have a strong educational component, featuring outreach to local high schools, undergraduate research opportunities, and a graduate research program. Centers should sponsor multidisciplinary workshops and summer schools focused on their central problem that will bring together students and researchers from various fields and institutions. The workshops would aim to bring in new ideas and collaborators as well as to disseminate to other fields the results they are achieving as they address the fundamental problems of fusion science. Potential focus topics for centers include turbulence and transport, magnetic reconnection, energetic particle dynamics, and materials; other topics would emerge in a widely advertised proposal process. Topics such as these are of broad scientific interest in allied fields. To build another bridge to allied fields, the DOE should cooperate with the NSF in establishing one or more centers addressing a topic of general interest in plasma science. The DOE/NSF centers should have as a central objective establishing collaborations with scientists who have expertise of value to the plasma science and fusion research effort. An explicit goal of the centers should be to convey important scientific results to the broader scientific community as well as the rest of the fusion community. An announcement of opportunity for fusion centers of excellence would, by itself, signal to the broader scientific community the community's intent to significantly bolster the scientific strength of the field. It would be highly desirable for other agencies, particularly NSF, to collaborate in one or more fusion centers of excellence for reasons of disciplinary and institutional diversity as well as to obtain the

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Page 6 benefits of interagency collaboration cited in recommendation 3. However, the DOE should play a lead role in these centers, not only for reasons of administrative clarity but also because its leadership will ensure that the impressive capabilities of the fusion energy science community are made available to new participants. DOE leadership will also ensure that progress in the centers would be communicated throughout the fusion community and translated into DOE program plans, to hasten progress towards the fusion energy goal. The procedure for awarding grants for fusion centers of excellence could do much to remedy the isolation of the fusion science community by ensuring that the broader scientific community will participate in the institution-building effort. The selection process for the centers should feature open, competitive peer review employing clear, science-based selection criteria. The committee believes that the establishment of such centers is critical enough to the new science-based approach to fusion energy that ways should be found to fund a first center even in a level budget scenario. The success of the competition and the quality of the first center should guide the decision on launching second or even third centers. In other programs, such centers have been effective mechanisms for broadening and deepening a scientific area. In the committee's view, there is a very strong argument for expanding program funding to give fusion centers of excellence a strong and durable foundation. Recommendation 5. Solid support should be developed within the broad scientific community for U.S. investment in a fusion burning experiment. A burning plasma experiment will eventually be scientifically necessary and is on the critical path to fusion energy. Determining the optimal route to a burning plasma experiment is beyond the scope of the committee; rather, the route should be decided in the near term by the fusion community. Resources above and beyond those for the present program will be required. The U.S. scientific community needs to take the lead in articulating the goals of an achievable, cost-effective scientific burning experiment and to develop flexible strategies to achieve it, including international collaboration. The committee agrees with the Secretary of Energy Advisory Board (SEAB) report that “... development both of understanding of a significant new project and of solid support for it throughout the political system is essential.” 4 However, since the U.S. fusion energy effort is now positioned strategically as a science program, advocacy by the larger scientific community for the next U.S. investments in a fusion burning experiment now becomes even more critical to developing that support. For this reason alone, the scientific isolation of the fusion science community needs to be addressed. Recommendation 6. The National Science Foundation should play a role in extending the reach of fusion science and in sponsoring general plasma science. The mission of OFES, following the restructuring of the program in 1996, has been to establish the knowledge base in plasma physics required for fusion energy, with the result that a substantial number of plasma science problems are being explored within the fusion regime that also have applicability to allied fields such as astrophysics. For this reason, the committee believes that the NSF should begin to play a larger role in the solution of these basic plasma science problems. The greater involvement of NSF could have an intellectual impact on basic plasma science similar to that which it has had on basic 4 Department of Energy (DOE), Secretary of Energy Advisory Board (SEAB), Task Force on Fusion Energy. 1999. Realizing the Promise of Fusion Energy: Final Report of the Task Force on Fusion Energy. Washington, D.C.: DOE, p. 2.

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Page 7 research in other scientific disciplines where mission agencies like DOE play the main funding role. NSF involvement would facilitate linkage to other fields and the involvement of new scientists in the program. Recently, NSF and DOE collaborated on a small but highly effective program to encourage small laboratory plasma experiments and the theoretical exploration of topics in general plasma science. The large number of proposals submitted to this program is an indication of the need for it. The rationale for the expansion of research in general plasma science was well articulated in an earlier document of the National Research Council (NRC).5 The NSF/DOE plasma science initiative, if operated at a dollar level closer to that contemplated in the Plasma Science report (an additional $15 million per year for basic experiments in plasma science), can serve several important functions: Stimulating research on broad issues in plasma science that have potential applications to fusion and Enhancing interagency cooperation and cultural exchange on the approaches used by the two agencies for defining program opportunities, disseminating information on research results to the scientific community, selecting awardees, and judging the outcomes of grants. The optimal process for this partnership, if there is sufficient funding (as requested in the Plasma Science report), would be an annual solicitation of requests for proposals (RFPs). In particular, this frequency would give new Ph.D.s the chance to enter the field and stay there, since new Ph.D.s are produced by degree-granting institutions each year and new graduate students enter school each year. Another limitation of the ongoing NSF/DOE program in basic plasma science is the absence of any provision for modest experiments in the $1-million-per-year class. Historically, neither DOE nor NSF has funded plasma science experiments of this scale. For this reason, the committee recommends a cooperative NSF/DOE effort to broaden the scientific and institutional reach of fusion and plasma research to obtain valuable scientific results. Increased NSF funding and a stronger focus on fusion and plasma science within NSF would be required. As discussed in recommendation 4, NSF could cosponsor one or more centers of excellence in fusion and plasma science. Recommendation 7. There should be continuing broad assessments of the outlook for fusion energy and periodic external reviews of fusion energy science. The committee finds the current pattern of multiple program reviews of different provenance to be excessive. A planned sequence of external reviews of the U.S. fusion science program should replace this pattern. The reviews should be open, independent, and independently managed. They should involve a cross section of scientists from inside and outside the fusion energy program. The manifest independence of the review process will help ensure the credibility of the reviews in the eyes of Congress, the Office of Management and Budget (OMB), and the broader scientific community. The scientific, engineering, economic, and environmental outlook for fusion energy should be reviewed every 10 years or so in a process that draws on fusion scientists, other scientists, engineers, policy planners, environmental experts, economists, and others, from here and abroad. These reviews 5 National Research Council, Panel on Opportunities in Plasma Science and Technology. 1995. Plasma Science: From Fundamental Research to Technological Applications. Washington, D.C.: National Academy Press.

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Page 8 should assess from multiple perspectives the progress in the critical interplay between fusion science and engineering in light of the evolving technological, economic, and social contexts for fusion energy. Consonant with its charge, the committee has not taken up the many critical-path issues associated with basic technology development for fusion, nor has it looked at the engineering of fusion energy devices and power plants, yet it is the combined progress made in science and engineering that will determine the pace of advancement toward the energy goal. Moreover, since much of fusion science research is undertaken in the expectation that it will contribute to the energy goal, regular, formal assessment of the progress towards fusion energy is one important way in which a fusion science program can be made accountable. STRUCTURE OF THE REPORT The report is organized into an overview chapter and three working group chapters: “Scientific Progress and the Development of Predictive Capability,” “Plasma Confinement Configurations,” and “Interactions of the Fusion Program with Allied Areas of Science and Technology.” Chapter 1 summarizes the general findings of the committee that came out of the three working group chapters and committee deliberations. It also refers to other reviews of the program since 1996, touches on the recent history of the tokamak experimental effort, and mentions briefly international efforts to build a fusion reactor, the International Toroidal Experimental Reactor (ITER). The first priority of the committee was an evaluation of the science being carried out by the DOE's OFES program. Chapter 2 of the report examines the science being done in the program, both in areas where there is state-of-the-art understanding and in areas where further work is needed to achieve the predictive capability that will facilitate the design of the optimum magnetic container for holding hot fusion-grade plasmas. Chapter 2 is the longest chapter of the report since the committee felt an in-depth elucidation of the physics was essential to a proper evaluation. Readers who want only a summary of the scientific progress may read the summary section of the chapter. In Chapter 3 of the report the various classes of magnetic container or confinement configuration are discussed. The discussion of the devices is organized around four scientific topics to illustrate the commonality of the physics issues being explored in each class of container. This commonality is too often lost when the devices are discussed separately. Enabling technologies and metrics are also discussed. Appendix C presents paragraph-long descriptions of each of the major confinement concepts. Chapter 4 addresses the interaction between the field of fusion and plasma science and the larger science, engineering, and technology community. Discussed are the deep physics questions that have been addressed by the program, including the generic science results that have impacted other areas of physics, some of the key contributions of U.S. scientists to the international effort, potentially important areas of future interdisciplinary research, leadership in the support of research areas, and recognition for scientific accomplishments. In addition to Appendix A , Appendix B through Appendic C , which were mentioned above, Appendix D is a glossary of technical terms and Appendix E lists acronyms and abbreviations.