The Committee to Assess the Current Status and Future Direction of High Magnetic Field Science in the United States was convened by the National Research Council in response to a request by the National Science Foundation. The committee was charged with answering three questions:
1. What is the current state of high-field magnet science, engineering, and technology in the United States, and are there any conspicuous needs to be addressed?
2. What are the current science drivers, and which scientific opportunities and challenges can be anticipated over the next 10 years?
3. What are the principal existing and planned high magnetic field facilities outside of the United States, what roles have U.S. high-field magnet development efforts played in developing those facilities, and what potentials exist for further international collaboration in this area?
A magnetic field is produced by an electrical current in a metal coil. This current exerts an expansive force on the coil, and a magnetic field is “high” if it challenges the strength and current-carrying capacity of the materials that create the field. Although lower magnetic fields can be achieved using commercially available magnets, research in the highest achievable fields has been, and will continue to be, most often performed in large research centers that possess the materials and systems know-how for forefront research. Only a few high field centers exist around
the world; in the United States, the principal center is the National High Magnetic Field Laboratory (NHMFL).
Owing in large measure to the NHFML, high-field magnet science in the United States is currently very strong. The NHMFL operates a variety of magnets including dc superconducting/resistive hybrids, pulsed magnets, a high-field, low-temperature facility, and a 900 MHz (21.1 tesla [T]) nuclear magnetic resonance (NMR) facility. These magnets, along with their advanced measurement instrumentation, constitute a highly successful user program. The recent achievement of 100 T at NHMFL’s Los Alamos venue represents the state of the art for high magnetic fields and has already produced new scientific results. In addition to NHMFL, other laboratories in the United States, including major laboratories supported by the Department of Energy, have made important contributions to high-magnetic field science through the design and deployment of state-of-the-art superconducting magnets for the purposes of high-energy physics and controlled nuclear fusion. However, despite the success of the NHMFL, U.S. leadership has eroded in at least one important area: high-field nuclear magnetic resonance (NMR) spectroscopy for chemical and biological applications. Here, European agencies have made large investments in new magnets and associated equipment that have not been matched in the United States.
The present report considers continued support for a centralized high-field facility such as NHFML to be the highest priority. At the same time, the report notes that if current efforts to develop a 32 T all-superconducting magnet are successful, it could be advantageous also to establish several smaller regional facilities utilizing this technology. The report also contains a recommendation for the funding and siting of several new high field NMR magnets at user facilities in different regions of the United States.
High magnetic fields have enabled major breakthroughs in science and have improved the capabilities of medical care. High field research can be divided into two broad areas. First, high fields, in competition with internal magnetic forces, can create exotic magnetic states in advanced electronic materials. The nature of these states challenges our basic understanding of matter. For example, in the fractional quantum Hall effect, accessed only in strong magnetic fields, electrons organize themselves into a peculiar state of matter in which new particles appear with electrical charges that have a fraction, such as one-third or one-fifth, of the charge of an electron. In other magnetic materials, the field can create analogues of the different forms of ice that exist only in magnetic matter. These exotic states also provide insight for future materials applications. Among these states are phases with spin-charge interactions needed in next-generation electronics. Here, the availability of the highest magnetic fields complements the development of novel materials. In the next 10 years, new materials possessing topological phases and useful functionalities will be advanced by their study in high fields. Future
implementation of high fields collocated with advanced photon and neutron spectroscopies will accelerate such advancements.
Second, in biological and chemical systems, high-field NMR performed on complex molecules has become indispensable for analyzing molecular structure and motion. Since resolution and sensitivity of NMR measurements increases with magnetic field, high magnetic field research translates into leadership in the investigation of the structural and functional properties of biological systems as well as the properties of technologically important materials. New frontiers in biological and medical imaging of human physiology and metabolism are being opened up by access to higher fields than available currently. The impact of high-field studies of biological and chemical systems is amplified by an expanding variety of techniques, including multidimensional NMR, dynamic nuclear polarization, functional magnetic resonance imaging, in vivo magnetic resonance spectroscopy, and Fourier transform ion cyclotron resonance. Applications of these and other techniques depend on increasing magnetic field strengths at the associated facilities.
Future prospects for instruments with higher magnetic fields are bright. Pulsed field magnets, such as that which produced 100 T, can be advanced with higher strength materials to produce even higher fields. Self-destructive magnets now produce fields much higher than 100 T, but at drastically reduced measurement times. Improvements in instrumentation and measurement techniques will make fields of this magnitude more widely available and useful to researchers. Opportunities for superconducting magnets lie in replacing low-Tc materials such as Nb3Sn, which presently produce 24 T dc, with high-Tc materials such as YBa2Cu3O7, which promise to reach 30 T dc in the next 5 years. New superconducting materials that would raise the attainable field even higher are presently being pursued. Superconducting magnets with the highest possible fields are also essential in high-energy physics and fusion physics. In medical devices, better imaging resolution afforded by higher fields will improve the physician’s ability to treat disease.
Continued advancement in high-magnetic-field science requires substantial investments in magnets with enhanced capabilities. The report contains recommendations for the further development of all-superconducting, hybrid, and higher field pulsed magnets that meet ambitious but achievable goals. It also contains recommendations for the development and deployment of high-field magnets at facilities for X-ray and neutron scattering and for the development of a 20 T, wide-bore magnet suitable for research using MRI on large animals and humans. Opportunities for the combination of high magnetic fields with a powerful source of terahertz radiation are also underscored.
High-field magnet facilities require infrastructure for the production of large electrical currents and for handling large amounts of cryogenic liquid; they also need the metal-forming capability to build new magnets. Such facilities have been built in Germany, France, the Netherlands, Japan, and China, but the NHMFL in
the United States is presently considered to be the world leader in both advancing magnet technology and high-field science. The global high-field community has a very good record of scientific collaboration, while retaining the competition between laboratories important for advancing magnet technology and producing scientific results. The report recognizes that future opportunity for U.S. high-field magnet technology lies in exploiting the expertise centered at NHMFL, while involving other laboratories and companies to enhance U.S. commercial competitiveness in such areas as the production of NMR magnets, and the report contains recommendations for pursuing those opportunities.
Finally, the NHMFL is a major multidisciplinary facility, and effective stewardship is critical to its vitality. In this regard, its continued effective management, its exploration of prospective partnerships for facilities development, and a predictable facilities recompetition plan are essential. Accordingly, the report contains a recommendation that NHMFL should have a recompetition cycle that is longer than that of the average major facility.