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Opportunities in High Magnetic Field Science Executive Summary In response to an informal request from the National Science Foundation, the National Research Council convened the Committee on Opportunities in High Magnetic Field Science in mid-2003. The committee was charged with four tasks: Assessment of the current state and future prospects of high-field magnet science and technology in the United States. Assessment of the status of U.S. high-field efforts in the international context, and trends in the international arena. Identification of particularly promising multidisciplinary areas for research and development with respect to magnetic fields. Discussion and prioritization of any major new initiatives in the construction of high-field magnets for the coming decade. The committee focused its attention on identifying the compelling scientific opportunities the field affords and the institutional infrastructure that would be required to realize them. Its conclusions and recommendations follow. A magnet is “high field” if its field strength is great enough to test the limits of the mechanical and/or the electromagnetic properties of the materials from which it is built. High-field magnets have been—and continue to be—used for research in many scientific disciplines, including medicine, chemistry, and condensed-matter physics; they are also enabling for fields such as plasma science and high-energy physics. Research that could only have been done with such magnets has produced
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Opportunities in High Magnetic Field Science important insights in a host of areas, ranging from brain function to high-temperature superconductivity. High magnetic fields are of great interest in areas such as astrophysics and magnetohydrodynamics, and high-field magnets also play an increasingly important role in industry. The committee’s task was to identify key scientific and technological challenges and opportunities, not to make specific programmatic recommendations. In general, the committee found that high magnetic field science in the United States is healthy and broadly multidisciplinary. However, there are some important opportunities that will be missed unless attention is paid to them soon. 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. Recent accomplishments include the development of functional magnetic resonance imaging (MRI), 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. It has also provided the first indications of how high-temperature superconductors evolve into unconventional metallic alloys in the extreme quantum limit. Outstanding work continues to be done in the area of magnet engineering, the discipline on which all these activities depend. There is every reason to believe that there will be new accomplishments as interesting as those mentioned above in the decades to come, especially if magnets are built that deliver higher fields than those available today. For instance, pulsed fields offer the opportunity to explore the highest magnetic fields in ways that can take research in new directions. Additionally, advances in high-speed electronics, instrumentation, and miniaturization could also allow greater experimental access to higher fields. 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 in high magnetic field research. For example, condensed-matter physicists and materials researchers 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,
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Opportunities in High Magnetic Field Science but U.S. scientists seldom travel abroad for that reason. An important corroborating observation can be found in the European Science Foundation’s 1998 report The Scientific Case for a European Laboratory for 100 Tesla Science, which states that one of the prime motivations for such a facility was “to be competitive with laboratories elsewhere, particularly in the United States and Japan.”1 In addition, the superconducting magnets being installed in the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN), as well as those contemplated for the International Thermonuclear Experimental Reactor (ITER), depend on magnet technology developed in the United States (although the magnets are in fact being manufactured overseas), as do the magnets installed in several other user facilities overseas. By way of contrast, in the area of nuclear magnetic resonance (NMR), which is an important component of high-field science, the United States is competitive but not dominant. About half of the instrumentation used by NMR spectroscopists in the United States, and virtually all of the magnets in their spectrometers, were manufactured abroad. Further, many of the most important recent advances in NMR have been made overseas, and, in general, European and Japanese companies have been ahead of U.S. companies in commercializing magnet technology advances. 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. It also worth noting that several key facilities in Japan have made important contributions to the development of the technologies required for the generation of the highest steady-state and pulsed magnetic fields. 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. Even the technology of high-field magnets is cross-disciplinary. Materials science and engineering make dominant contributions, but several branches of physics contribute as well. 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.
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Opportunities in High Magnetic Field Science 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 at the nation’s third-generation light sources. The scientific opportunities that are available to those able to study the neutron and x-ray scattering properties of materials at high magnetic fields are attracting growing attention around the world. Certain aspects of magnetism and high-temperature superconductivity have already been elucidated overseas at scattering center laboratories that have high-field instrumentation. Nevertheless, the United States does not currently plan to increase the high magnetic field instrumentation at its national radiation laboratories. Unless steps are taken to rectify this situation, the United States is sure to lag behind in key areas of condensed-matter and materials physics. Conclusion. Some important issues relevant to the advancement of magnet technology could be more efficiently addressed if the interested constituencies would interact more strongly, communicate more fully, and coordinate their activities better. One striking characteristic of all the sciences that use high magnetic fields is how constrained they are by the limitations imposed by magnet technology. Nevertheless, despite a shared need to overcome the same set of fundamental problems, each constituency has historically tended to develop the magnets it needed without much reference to the others. The reasons are several and obvious. The communities that use high-field magnets have different missions, and the magnets they need are specific to the mission of each. In addition, these communities are supported by different funding agencies, each of which has had its own perspective. A coordinated approach to magnet technology based on the pooling of resources and talent would be beneficial. Based on these conclusions, the committee has several recommendations that it offers, with the most important first. Recommendation. The United States should maintain a national laboratory that gives its scientific community access to magnets operating at the highest possible fields. A national high-field magnet facility is essential to the vitality of many important scientific disciplines. NHMFL has successfully fulfilled the need for high-field magnets for about a decade, and its activities have done much to foster the leader-
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Opportunities in High Magnetic Field Science ship position that the United States currently enjoys in many areas of magnetic science and technology. It is important to understand that at any high-field magnet laboratory, the capabilities of the devices available for controlling the environment in which a sample is tested and for measuring a sample’s properties are almost as important as the field strengths of the magnets themselves. Thus it is vital that a national laboratory equip its magnets with the best possible supporting instrumentation and personnel. In addition, ways to maximize the return on capital invested in the national laboratory should be explored, 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. For instance, the nation’s synchrotron light sources and neutron-scattering centers provide access 24 hours a day, 7 days a week when in full operation; this schedule allows visiting researchers to use their time at the facility to the best advantage. The trade-offs for expanding access to the NHMFL need to be identified and weighed carefully, especially in constrained budget situations. Recommendation. New instruments for studying the neutron and x-ray scattering properties of materials in high magnetic fields should be developed in the United States. Nowhere in the domestic research program is the gap between the instrumentation available for experimentation at zero field and that available for high-field experimentation wider than in the areas of neutron and x-ray scattering. This gap in capability is unfortunate, because scattering experiments provide a powerful means for elucidating atomic and magnetic structure, as well as for determining the nature of the spatial and dynamical correlations in materials. Development of new high-field capabilities at x-ray- and neutron-scattering centers in the United States could have an enormous scientific impact. Recommendation. A consortium should be established to foster the development of magnet technology. Rather than supporting an all-out, brute-force effort to build higher-field magnets using current technology, it makes sense to find new approaches that will make it easier (and cheaper) to build the magnets needed for research. Essential to this enterprise will be the development of both resistive and superconducting materials with improved electrical, magnetic, and mechanical properties. Scientists
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Opportunities in High Magnetic Field Science and engineers from all the communities working today on magnet technology should be brought together: the magnet engineers at the NHMFL; academic researchers; the magnet designers in the high-energy physics and fusion communities; commercial vendors of superconducting magnets, including nuclear magnetic resonance and magnetic resonance imaging systems; and manufacturers of advanced materials, such as high-strength materials and superconducting wire. The sharing of information and resources within the larger community, which is now fragmented into components that communicate poorly, would accelerate the rate at which solutions are found to the fundamental problems confronted by all. The committee proposes that the involved communities cooperate to establish a consortium for developing the technology necessary to pursue several aggressive goals that may have different timescales. Some groups might frame their goals in terms of application-specific requirements for magnet performance, such as the development of a 30-T superconducting high-resolution magnet for NMR, a 60-T DC hybrid magnet, or a 100-T long-pulse magnet. Others, such as the high-energy physics and fusion science communities, might focus explicitly on the materials problems intrinsic to enabling high-volume production of quality conductors for a variety of magnet systems. Recommendation. Government agencies supporting high-field magnetic resonance research should directly support the development of technology and instrumentation for magnetic resonance and magnetic resonance imaging. Without the concomitant development of ancillary technologies, the construction of higher-field magnets for magnetic resonance will not produce the scientific dividends it should. While federal funding for the application of existing technology and methods to specific scientific problems has generally been good, federal funding for the development of novel technology and methodology has been poor. Magnetic resonance and MRI instrument manufacturers have done a good job of advancing the supporting technologies for these techniques when commercial markets for their products justified their doing so. However, there are many areas where technological advances are sorely needed but the commercial market is not large enough to attract the attention of instrument manufacturers. For example, optimal coils for high-field MRI will probably not be realized unless groups outside the commercial sector undertake a sizable research program. Likewise, because higher fields cause significant changes in the relative strengths of the interactions that determine how nuclear magnetic moments evolve, pulse sequences and methodologies will have to be improved if magnetic resonance research is to take full advantage of high-field magnet advances.
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