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Opportunities in High Magnetic Field Science 4 Conclusions and Recommendations CONCLUSIONS Current State and Future Prospects Conclusion. High magnetic field science and technology are thriving in the United States today, and the prospects are bright for future gains from high-field research. High magnetic field science is having an important impact in many disciplines, including medicine, chemistry, and condensed-matter physics. Recent accomplishments include the development of functional magnetic resonance imaging (fMRI), which is revolutionizing neuroscience; optically pumped magnetic resonance techniques, which allow visualization of new quantum phenomena in semiconductors; and ion cyclotron resonance mass spectroscopy, which is becoming an important tool for exploring the chemical composition of complex systems. High-field research has led to the discovery of new states of matter in low-dimensional systems, and it has also provided the first indications of how high-temperature superconductors evolve into unconventional metallic alloys in the extreme quantum limit. Improvements in ancillary instrumentation and the development of new strategies for using high-field magnets have contributed to these advances and should continue to do so. Outstanding work continues to be done in the area of magnet engineering, the discipline on which all these other activities depend. There is every reason
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Opportunities in High Magnetic Field Science to believe that developments as interesting as these will continue in the decades to come, especially if magnets are built that deliver higher fields than those available today. For instance, discoveries made using pulsed-field magnets, which operate at very high fields and are equipped with instruments that take full advantage of advances in electronics, could take research in fruitful new directions that cannot now be anticipated. U.S. High-Field Efforts in the International Context Conclusion. The United States is a leader in many areas of high-field science and technology, but further investment will be required to make it competitive in some critical areas. There are many indicators of the strength of the U.S. effort. For example, condensed-matter and materials scientists from other parts of the world routinely travel to the National High Magnetic Field Laboratory (NHMFL) to perform experiments that they are unable to do at home, but U.S. scientists seldom travel abroad for that purpose. An important corroborating observation is found in the European Science Foundation’s 1998 report The Scientific Case for a European Laboratory for 100 Tesla Science.1 In that report, a panel of experts was charged with investigating and proving the users’ scientific case for such a world-class laboratory. The report concluded that the scientific case for a 100-T laboratory was compelling and that, in fact, one of the prime motivations was “to be competitive with laboratories elsewhere, particularly in the United States and Japan.” In addition, the superconducting magnets being installed in the Large Hadron Collider (LHC) at CERN, which were built in Europe, as well as those contemplated for the International Thermonuclear Experimental Reactor (ITER), depend on magnet technology developed in the United States, as do the magnets installed in several other user facilities overseas. However, in the area of NMR, which is a major component of high-field science, the United States is competitive but not dominant.2 About half of the instrumentation used by NMR spectroscopists in the 1 European Science Foundation, The Scientific Case for a European Laboratory for 100 Tesla Science, ESF Studies on Large Research Facilities in Europe, 1998. Available online at http://www.esf.org/publication/109/100T.pdf. 2 The issues of (and case for) U.S. international leadership in key research areas and among international leaders in important areas of science and technology is best described in a 1993 report from the National Academies, Science, Technology, and the Federal Government: National Goals for a New Era, Washington, D.C., National Academy Press, 1993.
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Opportunities in High Magnetic Field Science United States, and virtually all of the magnets in their NMR spectrometers, were manufactured abroad. Further, many of the most important recent advances in NMR were made overseas, and, in general, European and Japanese companies have been ahead of U.S. companies in commercializing magnet technology.3 Finally, Europe is far ahead of the United States in equipping its synchrotron light sources and neutron-scattering centers with instruments for studying the x-ray-and neutron-scattering properties of materials in high magnetic fields. Likewise, Japan operates several key facilities that have played large roles in developing technologies for the highest steady-state and pulsed magnetic fields. Promising Multidisciplinary Areas for Research and Development Conclusion. High-field magnet science is intrinsically multidisciplinary. The construction of high-field magnets has always been motivated by the science that could be done with them, and in recent decades, physics, chemistry, biology, and medicine have all benefited from advances in magnet technology. For example, experiments done at the highest available magnetic fields have provided fundamental information about high-temperature superconductors, and instruments incorporating such magnets have enabled biochemists to study the structures and dynamics of large proteins. Physicians routinely use imaging instruments that contain high-field magnets to visualize the interiors of their patients. Since the performance of all such instruments generally improves with increasing field strength, the benefits that would accrue in these areas of science and medicine alone are more than enough to justify continued investment in magnet development. Even the technology that makes the construction of high-field magnets possible is cross-disciplinary. It is dominated by materials science and engineering, but several branches of physics contribute also. Lying at the heart of much of the science done with magnetic fields today is the phenomenon of superconductivity. Investigation of superconductivity is a thriving area of materials science and condensed-matter physics, much of it now aimed at understanding how superconducting materials, especially high-critical-temperature superconductors, respond to magnetic fields. Scientific advances in this area will have widespread benefits because superconducting materials are used to build high-field magnets. The technology for making useful conductors out of high- 3 For instance, both Bruker BioSpin in Germany and the high-field lab in Tsukuba, Japan, are developing 1-GHz NMR machines.
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Opportunities in High Magnetic Field Science temperature superconductors as well as out of the recently discovered superconductor MgB2 has advanced significantly in the last 2 years. Major Construction Initiatives for the Coming Decade Conclusion. U.S. scientists will be unable to access a wealth of science opportunities if high magnetic field instrumentation is not provided at the Spallation Neutron Source and the nation’s third-generation light sources. Also there are important issues relevant to the advancement of magnet technology that could be more efficiently addressed if the interested constituencies interacted more strongly, communicated with each other more fully, and coordinated their activities better. At present, there are no magnet construction initiatives under consideration in the high-field community that would require major new investments for their execution, aside from some application-specific magnet development plans such as those being considered in connection with the ITER fusion reactor, certain accelerators for high-energy physics, and high-field MRI. However, there are needs that will have to be addressed in the next decade if the United States is to remain internationally competitive in this important, fast-moving field. RECOMMENDATIONS The committee’s recommendations follow below in order of priority, most important recommendations first. In the course of its data gathering and deliberations, the committee made several observations relevant to NHMFL, which has facilities in Tallahassee, Florida; Gainesville, Florida; and Los Alamos, New Mexico. In making the following recommendation, the committee is not evaluating NHMFL. However, in responding to the charge “discuss and prioritize major new initiatives,” the committee could hardly avoid identifying key components of the current laboratory system and highlighting areas that could be optimized. The committee bases the suggestions in its first recommendation on evidence presented in person at its open meetings, written testimony submitted in response to the call for input, impressions gathered during the site visit to NHMFL, and the direct experience of members who have used the facilities at NHMFL. Recommendation 1a. The United States should maintain a national laboratory that provides its scientific community access to magnets operating at the highest possible fields.
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Opportunities in High Magnetic Field Science A facility of this sort is essential to the vitality of many important scientific disciplines. NHMFL has successfully fulfilled this need for about a decade, and its activities have done much to foster the position that the United States currently enjoys in many areas of magnetic science and technology. The recent $10 million special appropriation by the state of Florida to address urgent infrastructure needs at the laboratory will help ensure that NHMFL can continue to perform this function. Recommendation 1b. The quantity and the quality of the supporting instrumentation at NHMFL should be improved. At any high-field magnet laboratory, the capabilities of the devices available for controlling sample environments and measuring sample properties are almost as important as the field strengths of the magnets themselves. If more support personnel were available at NHMFL and more and better instrumentation were available, more effective work could be done and new research avenues would open up. The kinds of instrumentation that would be useful include setups to do magnetization, optical, electron-spin resonance, and pressure dependence measurements. The limited availability of the very low temperature (<10 mK) setup in Gainesville and the maximum field at which it can operate are other constraints. Recommendation 1c. The operating schedule of NHMFL needs to be examined. For perfectly understandable budgetary and logistical reasons, NHMFL does not operate 24 hours a day, 7 days a week. But it is clear from information provided by NHMFL that its facilities are presently oversubscribed, a fact supported by the testimony of many of its users. NHMFL, in cooperation with NSF, should explore ways to maximize the return on capital invested in the national laboratory, such as longer hours of operation and flexible scheduling. The laboratory should undertake a cost-benefit analysis to identify the optimal balance between addressing user demand and the increased operating costs associated with longer hours of operation. The nation’s synchrotron light sources and neutron-scattering centers, by contrast with NHFML, provide access 24 hours a day, 7 days a week, when in full operation, allowing visiting researchers to use their time at the facility to the best advantage. The trade-offs for expanding access to NHMFL need to be identified and weighed carefully, especially in constrained budget situations. The “extra” instrument time that would become available if NHMFL expanded its operations would enhance its scientific productivity and do much to alleviate the competition
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Opportunities in High Magnetic Field Science that now exists for access to its most unique magnets: the 33-T Bitter magnets and the 45-T hybrid magnet. Priority should also be given to improving the instrumentation available at its pulsed magnets so that some of the work now done on its DC magnets can be shifted to pulsed magnets. Recommendation 2. New instruments for studying the neutron- and x-ray-scattering properties of materials in high magnetic fields should be developed in the United States. If history is any predictor of future success, instruments for making x-ray- and neutron-scattering measurements at high magnetic fields will deliver enormous scientific dividends. First-class science could be done with instruments that incorporate current state-of-the-art, high-field magnets; magnets that operate at even higher fields would be desirable but are by no means essential. The development of existing technology instruments is an obvious way to leverage the investments the nation has already made in high magnetic field science and technology and in x-ray- and neutron-scattering facilities. The magnetic moment of neutrons makes them uniquely suited for investigating the magnetic properties of materials. The Spallation Neutron Source (SNS), which is under construction at Oak Ridge, will be the most powerful neutron source in the world when it begins operation, and it is the obvious place to start. The addition of high magnetic field instrumentation at SNS would provide U.S. scientists experimental capabilities unmatched elsewhere in the world. With these combined capabilities, researchers would be able to probe the dynamical properties of magnetic materials, the structure of magnetic moments in solids, and magnetic-field-induced phase transitions. It should also be noted that by improving the high magnetic field instrumentation at existing neutron facilities, capabilities could be obtained that are comparable to, or exceed, those now available in Europe. Because the high-field capability at the nation’s light sources is also limited, the installation of high-field instrumentation at one of its third-generation light sources would be the logical second step in such a program. For economic reasons, the construction of state-of-the-art neutron or x-ray facilities at NHMFL seems an unattractive alternative. It will be difficult to decide what kinds of high-field magnets should be provided at these scattering centers. On the one hand, the scientific opportunities that exist in the area of high-temperature superconductivity argue for installing magnets that generate the highest possible fields. On the other hand, mechanical, heating, cooling, and other considerations may require compromises. This committee was
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Opportunities in High Magnetic Field Science not asked to make more specific recommendations in this area, but it strongly recommends that these issues be pursued as soon as possible. Recommendation 3. A consortium should be established to foster the development of magnet technology. In every scientific area the committee examined, magnets that produce fields higher than those available today would improve the reach of current research and, in many cases, bring new insights into unsolved problems. Order-of-magnitude increases in field strength cannot be expected, but 50 percent increases might be achievable, and they would be significant, as they have been all along. Improvements in field strength and, for pulsed magnets, field duration that are more than incremental will not be obtained unless many basic engineering and materials science problems are resolved, and it is these issues that the proposed consortium should address. This recommendation is aimed primarily at the communities interested in high-field magnets and is motivated by the obvious advantages that might accrue to all if resources were pooled to solve common problems. The committee is open-minded about how this activity should be organized, but the objective is clear: to bring together scientists and engineers from all the communities working today on magnet technology, including the magnet engineers at NHMFL, academic researchers, the magnet designers in the high-energy physics and fusion communities, commercial vendors of superconducting magnets, including NMR and MRI systems, and manufacturers of advanced materials, such as high-strength materials and superconducting wire. The activities to be undertaken by the proposed consortium are sufficiently important to warrant federal support, but it would be wise for the membership to be international. Many of the communities that use high magnetic fields are already supranational in character, and several of the leading industrial magnet development companies are based overseas. The sharing of information and resources within that larger community, which is now fragmented into components that communicate poorly, should accelerate the rate at which solutions are found to the problems they share. The committee proposes that the involved communities cooperate to establish a consortium whose objective would be to address the fundamental materials science and engineering problems that will have to be solved before the next generation of high-field magnets can be built. It is precisely because the needs of the many communities that use high magnetic fields overlap that the consortium approach seems appropriate. The committee envisions an effort that could range from something as small as a series of joint conferences or a virtual laboratory to a broad initiative
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Opportunities in High Magnetic Field Science formally facilitated by the Office of Science and Technology Policy that spans several agencies and has international involvement. It is in the vein of recognizing common challenges that could be better addressed by coordinated efforts that the committee identifies several targets for magnet technology. As the underlying technology advances, some of the communities might decide to articulate more specific goals, such as the construction of magnets having the following specifications: A 30-T superconducting, high-resolution magnet for NMR. This technology would make it possible to build a 1.3-GHz NMR spectrometer for the study of large molecules. It would also permit the manufacture of magnets more suitable for condensed-matter physics and materials science laboratories than any available today. A 60-T DC hybrid magnet. Such a magnet would make it possible to do steady-state measurements at fields that can be accessed today only using pulsed field magnets. A 100-T long-pulse magnet. It will always be possible to reach higher fields with pulsed magnets than with DC magnets. A long pulse (i.e., ~100 ms) magnet of this field strength would enable a wide range of measurements at 100 T that cannot be made using magnets that operate for shorter times at the same field strength. Other communities such as high-energy physics or fusion science might choose to focus on the materials science and engineering issues that surround high-volume production of the conductors needed for their magnet systems. The committee anticipates that it may be appropriate to build an engineering test facility (perhaps leveraging existing investments) to support the activity of such a consortium. It also acknowledges that this ambitious program could span more than a decade. Recommendation 4. Agencies supporting high-field magnetic resonance research should directly support the development of technology and instrumentation for magnetic resonance and MRI. Without improvements in ancillary equipment, such as NMR probes, resonators, MRI coils, and radiofrequency electronics, the scientific benefits of higher magnetic fields will not be fully realized by the magnetic resonance community. Historically, the federal agencies supporting research that depends on magnetic resonance (NMR and electron paramagnetic resonance) and/or MRI have been reluctant to invest directly in this kind of technology. This attitude is short-sighted. Modest
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Opportunities in High Magnetic Field Science investments in NMR/EPR/MRI technology could result in improvements in instrument capability that have a large, beneficial impact on the quality and quantity of the data produced by many of the scientists these agencies support. (The committee recognizes that exploitation of the opportunities offered by the development of higher-field magnets will require concomitant advances in instrumentation and technique for nearly all applications in all disciplines, but in the area of magnetic resonance the need is particularly acute.)
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