High-Magnetic-Field Research and Facilities: [Final Report] (1979)

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2 Conclusions and Recommendations There has been increasing progress in most areas of research and technology involving magnetic fields. In addition, we can point to investigations in which higher magnetic fields will be critical to the advancement and attainment of knowledge. Hence, we believe that the generation and use of high magnetic fields in the study of the properties of matter is of great importance to the national program in research and technology. Examples of opportunities span such diverse studies as transitions to lower dimensionality and Wigner crystal- lization, metallurgical phase transitions, and antibody-antigen interactions (thus the field of immunology, probably the most fruitful area of cancer research). Because of (a) the pervasive role magnetic fields have played, (b) the gener- ally proven validity of extrapolating future advances from past progress as field strengths were increased, (c) the breadth of interest, application, and potential, and (d) the many exciting scientific opportunities, we recommend increased work toward the attainment of higher magnetic fields. The combined weight of the scientific and technical opportunities in many disciplines, rather than a single, pressing argument, justifies this recommenda- tion. For this reason, and because of the apparent technical and economic problems, we do not recommend a "crash" program, but instead we recom- mend a sustained and orderly approach to the attainment and utilization of higher magnetic fields. In Chapter 3, on Scientific Opportunities, we have identified a large class of experiments that become feasible as magnetic fields are increased by fac- tors of 2 or 3 above today's limit (approximately 30 T). Although scientific opportunities increase as available magnetic field strengths are increased, sci- entific thresholds appear to exist in the vicinity of 75 T (e.g., nuclear mag- netic resonance becomes comparable in frequency, hence sensitivity, to X- band electron spin resonance). This calls for a long-range effort to generate steady-state, high-homogeneity fields of that magnitude. Unfortunately, cur- rent cost estimates for construction of such a facility (see Chapter 5) are

Conclusions and Recommendations 5 prohibitive. We propose below a program of study to identify practical means to achieve that goal, as well as intermediate steps of lower fields, perhaps through the use of techniques and materials not yet available. While steady-state fields are most desirable, quasi-static fields (duration times greater than tens of milliseconds) should be vastly less expensive and yet promise significant payoff (e.g., de Haas-van Alphen experiments near 100 T). We shall, therefore, propose that a program be started to design and construct such facilities. Indeed, diagnostic techniques developed at such fields will be of great value to a static high-field facility. Finally, short-pulse (of the order of microsecond duration) fields of 1000 T can be generated with present technology. A smaller, but nevertheless exciting, subset of unusual opportunities exists in the field regime between 100 T and 1000 T. This is a largely unexplored region of research and may well produce unusual and unexpected results. The relatively low cost and potentially high scientific payoff have led us to propose a program that will lead to experiments in this field range. The scientific, technical, and economic considerations detailed in the sub- sequent chapters lead us to the following recommendations: I. A design program should be started to determine appropriate methods for producing steady-state, highly homogeneous magnetic fields up to 75 T. The design program will involve the study of high-field, superconducting materials and magnets, as well as the study of new approaches to the design of resistive and hybrid magnets. Although the attainment of 75-T fields is the eventual goal of this recommendation, fields of 45 T and 60 T, steps along the way to 75 T, will help to provide the technology necessary for higher- field-magnet development. Significant scientific opportunities exist at these intermediate fields, and their scientific potential should be exploited. Superconducting magnets will play a fundamental role in the attainment of higher steady-state fields and technological applications. Hence, in addition to an increased commitment to basic research in superconducting materials, there should be increased funding for materials processing and magnet tech- nology, so that some of the known higher-field superconductors might be fabricated into practical magnets. A facility affording a higher magnetic field, as discussed above, whether it be 75 T or an intermediate field, achieved on the way toward the long-range goal of 75 T, would be of inestimable value to the high-field superconductiv- ity and magnet development communities. The variety of materials for which critical current densities and critical magnetic fields are measurable would be considerably extended, with the consequent acquisition of information essen-

6 HIGH-MAGNETIC-FIELD RESEARCH AND FACILITIES tial to the effort to utilize advanced high-field superconductive materials for the construction of magnets. II. The design and construction of a quasi-static pulse magnet with fields approaching 100 T should be undertaken. Increased support should be given to one or more centers for the genera- tion of quasi-static fields of about 100 T. Scientific opportunities supporting this recommendation are detailed in Chapter 3. In addition, the development of such facilities will contribute to the technology necessary for attaining higher steady-state fields. III. The design and construction of short-pulse magnets affording fields greater than 1000 T is feasible and should be undertaken. Increased support should be given to one or more centers where fields of about 1000 T can be generated so that experimental work and development of the facilities are stimulated. This ultrahigh field use and development can be implemented immediately, for the technology currently exists (see Chap- ter 5). In choosing a facility to fund, the quality and breadth of the scientific support must be taken into account. As corollaries to these principal recommendations, we add the following: • As a necessary concomitant to the above recommendations, we recom- mend the allocation of research support sufficient to allow the exploitation of high magnetic fields. • We recommend that facilities receive sufficient funds so that the neces- sary supporting equipment (e.g., optical spectrometers, ESR and NMR spec- trometers) be available. • Because large energy sources and technology exist at facilities for fusion research, weapons technology, and high-energy physics, we recommend that incremental funds be allocated to adapt these major resources for high-field research. Finally, IV. Because we feel that small regional facilities containing magnets with field strengths less than 15 T are not in sufficient demand to justify capitalization and operating costs, we recommend that additional general facilities with less than 15 T not be established at this time; however, we

Conclusions and Recommendations 7 do recommend the continued support of such magnets for in-house re- search projects. The chapters that follow provide the background and rationale for the recommendations presented in this section.