Summary

INTRODUCTION TO THE REPORT

The National Academies of Sciences, Engineering, and Medicine have been asked to conduct a study on high-magnetic-field science and technology. The primary goal of the Committee on the Current Status and Future Direction of High-Magnetic-Field Science in the United States, Phase II is to be forward-looking and identify new scientific opportunities enabled by existing and emerging high-magnetic-field technologies for the next decade and beyond. The committee statement of task included the following questions:

1. What is the status of domestic and international high-magnetic-field science and technology?
2. What current and future science disciplines have the most critical needs for new capabilities that could only be enabled by high magnetic fields?
3. What are the most important gaps in current high-magnetic-field science, technology, and infrastructure that must be met to address these critical needs?
4. What approach would the committee recommend to maximize the potential for existing and emerging high-magnetic-field technologies and infrastructure to close these gaps?

This report is a sequel to previous studies from 1979,¹ 2005,² and 2013.³ Each of the previous reports had its own scope; the charge to the present committee is given above, and the full statement of task is reprinted in Appendix A. The committee stresses that this is a forward-looking study, and while it has carefully studied the state of the field its purpose is not to review or judge past progress.

The 2013 National Research Council (NRC) report High Magnetic Field Science and Its Application in the United States: Current Status and Future Directions (“2013 NRC report”) made several recommendations that the committee will refer to, including some which have not been acted upon that it will reiterate. While the committee cannot be fully sure of the reasons for inaction we suspect several causes: budgets have been inadequate for concurrent development of multiple new magnets; the National Institutes of Health (NIH) has turned away from investment in high-field nuclear magnetic resonance (NMR) in favor of cryo-electron microscopy; the United States has not developed a clear agenda for high-field magnetic resonance imaging (MRI) outside the science community; and there is not a robust commercial industry for the highest-performing superconducting wire. On the positive side, the committee notes that the U.S. Accelerator Magnet Program has been well stewarded in a partnership between the National Science Foundation (NSF) and the Department of Energy (DOE) that is aligned with a long-term vision for that field. The National High Magnetic Field Laboratory (NHMFL) has continued to have a world-leading user program, and to develop new magnets within capital constraints.

As part of its study, the committee engaged extensively in fact-finding. This involved site visits of some of the committee in the United States and Europe; several information-gathering sessions, both in person and virtual; invited presentations to the committee; and written submissions. (See Appendix B for details.)

LAYOUT OF THIS REPORT

This summary lays out the scientific and technical background to high-magnetic-field science and technology, including the major application areas; surveys broadly the international landscape of high-field research, noting developments in the past decade and the competitive position of the United States; and previews key recommendations of the report.

Subsequent chapters review science and technology areas in depth, as well as stewardship and training. Each chapter provides background and justification for the recommendations made therein, some of which are elevated to the “key recommendation” section.

WHAT IS A MAGNET?

Magnets and magnetic materials have been known since ancient times in cultures across the world, including ancient China, Greece, and India. A natural ferromagnetic material, the mineral magnetite (Fe₂O₃/Fe₃O₄)—was used as a lodestone to orient a compass to align with Earth’s magnetic field and to fix the magnetic north pole. The compass has oriented travelers for more than 2,000 years.

Magnetic fields can be generated in two ways: through the alignment of quantum-mechanical spins, as in a conventional magnet, and through the passage of an electrical current through a wire. Both these methods are used in modern technology. The unification of the understanding of magnetic fields required the development of electromagnetic theory and relativity in the 19th century and quantum mechanics in the 20th century. Scientific understanding of magnetic fields is relatively recent in comparison to the practical use of magnets; ancient mariners had no inkling that they were exploiting properties of relativistic quantum mechanics. Understanding of materials and their magnetic and conducting properties continues to develop in the 21st century, so discovery continues.

WHAT IS A HIGH MAGNETIC FIELD?

The committee defined “high magnetic field” as its application in an instrument to which specialized access needs to be provided that is beyond what is typically available in a small laboratory setting. “High field” must be taken in context: some applications demand uniform and homogeneous fields, some require large volume, and others may need specialized sample environments such as cryogenic temperatures and high pressures.

Magnetic fields are measured in units of teslas (T). Earth’s field is about 50 millionths of a tesla (50 mT). A conventional iron bar magnet can generate a field of 0.5 T. Rare-earth magnets make use of the largest available atomic magnetic moments to generate fields of order 1–2 T. These magnets are widely used in electric motors and dynamos.

To achieve magnetic fields larger than 1–2 T, one needs to pass large currents through metal wires, often superconducting (which have zero electrical resistance) to minimize heating. Current magnets used for human-scale clinical MRI will generate fields of 7 T using refrigerated superconducting wires at 4 K. (The maximum field is growing; see below.) The largest steady magnetic fields that can be currently

• MRI uses NMR and pulsed gradient magnetic fields to produce high-resolution images of soft tissue. MRI is one of the most important noninvasive medical imaging methods, used in medical centers everywhere.
• Electron spin resonance (ESR) is an analogous technique to NMR that is used to understand materials with unpaired electron spins.
• Ion cyclotron resonance (ICR) is a technique for mass spectroscopy that has unparalleled resolution and is particularly useful to analyze complex mixtures of molecules in the environment.

Pushing to higher magnetic fields than used in current mainstream applications invariably produces higher spatial and spectral resolution, sometimes unlocking new capabilities. There are innumerable physical, chemical, pharmaceutical, and biological systems, where the information content that can be tackled improves dramatically with increasing magnetic field strength.

This report will discuss these techniques in detail in Chapters 1 (resonance spectroscopy) and 2 (resonance imaging).

Magnetic Fields to Direct Subatomic Particles

Moving charged particles (electrons, protons, and nuclei) are deflected by magnetic fields. The bigger the field, the more the deflection; the larger the velocity, and more the need for bigger fields.

• Synchrotron radiation sources are accelerators, called storage rings, where electrons are circulating with a speed close to the speed of light. A storage ring consists of a set of bending, focusing, and undulator magnets. Bending and focusing magnets confine electrons within the closed orbit and compress them to extremely small volume. Undulators force electrons to wiggle or rotate around a straight line to generate powerful synchrotron radiation over a spectrum ranging from the infrared to hard X ray. Related to storage ring light sources are free electron lasers that generate extremely short and high-intensity pulses of radiation. These instruments (usually in national facilities) are workhorses for the science and technology community with tens of thousands of users annually. Both higher magnetic fields and the increased precision of magnetic field engineering support the latest generation of facilities now coming online.
• Neutron sources are another important tool for science provided at major facilities that are either nuclear reactor sources or spallation⁴ sources. In the latter, protons are accelerated into a target of a heavy nucleus to generate neutrons in pulses. There is a premium on making compact linear accelerators to produce high-energy protons and then manipulating them into bunches in an accumulator ring.
• Particle accelerators for fundamental physics again rely on large magnets to control the beams. Upgrades to higher energies, and potential new facilities (e.g., a muon collider^5,6), will likely require deploying larger fields that will need high-temperature superconductors.
• Magnetic fusion science requires magnets to confine plasmas whose temperatures are of an order of a million degrees. The only known way to do this on Earth is with a magnetic bottle. Higher fields potentially allow a reduction in size and consequent reduction in cost.

This report will discuss magnets for these systems in Chapters 3 (Superconducting Magnet Technology for Fusion) and 5 (Accelerator Magnets).

Magnetic Fields to Modify Matter

Magnetic forces are characteristically four orders of magnitude weaker than the electrical forces that bind materials. Hence, fields large enough to influence the physical properties of matter are minimally tens, and typically hundreds of teslas, and often require pulsed fields. High-field studies play an important role in discovery science in condensed matter physics, chemistry, and biology and are provided at large user facilities (in the United States, NHMFL). Increasing the field strength allows a broader array of phenomena to be explored, as well as phenomena in near ambient temperatures. Just as important as the strength of the magnetic field is the ability to make accurate measurements under extreme conditions.

The committee will discuss the impact of high fields on condensed matter science in Chapter 4. There are several key recommendations on the provision of larger magnets that are of direct impact on this community.

WHAT IS THE CURRENT INTERNATIONAL LANDSCAPE?

The 2013 NRC report⁷ noted that the United States maintained leadership in many areas of high-field science and technology, but that without further investment, that leadership would be threatened. That report noted the growth taking place in Europe and China and made recommendations for U.S. investment that have not taken place for the most part.

The United States, Europe, Japan, and China all maintain large user facilities on concentrated sites, providing access to the highest fields for a broad user community. A map of the largest facilities is shown in Figure 8-1 (in Chapter 8). In the United States, NHMFL is located at three sites: Tallahassee, Florida; University of Florida, Gainesville, Florida; and Los Alamos National Laboratory, Los Alamos, New Mexico (pulsed fields); in Europe, there are direct current (DC) facilities at Grenoble and Nijmegen and pulsed fields at Toulouse and Dresden; in China, Hefei (DC) and Wuhan (pulsed); and in Japan at Sendai (DC), Tokyo, and Osaka (pulsed).

These facilities offer significant differences in their capabilities, as well as variations in their modes of operation. For example, Tokyo offers single-turn pulsed field (destructive) magnets toward 1000 T, which are not available elsewhere; Los Alamos provides generator-driven pulsed magnetic fields that have different characteristics from capacitively generated fields; Nijmegen and Dresden offer a combination of high fields and free-electron lasers.

Notable over the past decade has been the growth in capability in China, which

There are continuing supply chain and sourcing issues. The committee notes that commercial high-field NMR and MRI systems are provided by very few companies. GE Healthcare maintains the manufacturing of 1.5 T and 3.0 T magnets in the United States, but there are no U.S. manufacturers of ultrahigh-field MRI systems (7 T or above) or for commercial-, chemistry-, or biophysics-oriented NMR systems. Current superconducting commercial magnet systems use niobium–titanium (NbTi), having been developed here in the 1970s, which is only partially sourced in the United States. Future magnet technologies will likely use niobium-tin (Nb₃Sn) and high-temperature superconductor (HTS) wire, and there is no U.S. commercial source at scale for the latter. One of the HTS materials (REBCO) includes rare-earth elements, largely sourced from China. High-strength copper-niobium (CuNb) wire, which is the optimal wire for high-field pulsed magnets, is sole-sourced from RusNano, a Russian state–established and funded company. Superconducting magnet systems use liquid helium as a refrigerant, and supplies (and prices) have been highly unpredictable.

This report includes an analysis and recommendations for the future development of magnet technologies using superconducting wire in Chapter 6. Because helium supply is a major issue for researchers across this field (and of course elsewhere), the committee presents a separate discussion in Chapter 7.

As already indicated above, the health of the research community depends on stewardship of valuable resources, both in centralized and distributed facilities; this is addressed in Chapter 8. The need for training across the discipline, both in science and engineering, is discussed in Chapter 9. The opportunities for multimodal capabilities by providing high magnetic fields at other national facilities (X-ray sources, neutron sources) are discussed in Chapter 10.

KEY FINDINGS AND RECOMMENDATIONS

This section pulls from the subsequent chapters’ key findings and recommendations. Note that the key recommendations are not in order of priority. Many of these crosscut the different disciplinary areas. The committee begins by discussing the need for a systematic cross-agency approach on HTS magnet technologies that would make the United States a leader in this area. The committee then follows with recommendations on access and stewardship. Importantly, the committee then insists on the need for the United States to regain leadership in the field by investing in new world-leading magnets. The committee believes that there are specific issues around training of the next generation of scientists, engineers, and technical personnel that can be addressed by modest interventions, some of which have been recommended before. And lastly, the committee wishes to raise the important issue of helium supply.

Development of New Magnet Technologies, Materials, and Wire

The committee found that the emergence of practical HTS superconductors indicate their potential use for development of higher field and more compact magnets for a wide range of applications from high-energy physics, high-field science, fusion energy, high-field NMR, and MRI. In Figure 6-1, showing the potential operating space for various wires, the Nb-Ti wire used in the majority of today’s superconducting magnets is limited to the left bottom portion of Figure 6-1. In comparison with the higher field and current carrying capability of the HTS materials, the opportunity is enormous.

The committee concluded that successful exploitation of the potential HTS design space is not guaranteed without substantial investment and oversight. As outlined in a summary history of the development of the early work on superconducting wire⁸ that was largely funded initially by the DOE in support of high-energy physics applications in the 1960s and beyond, the rapid commercial adoption of the NMR and MRI in the 1970s and 1980s drove the quality of the work and established a reliable and cost-effective commercial supply for both research and commercial use. Fusion is emerging as a significant consumer of the HTS materials and is supported by industry, but there is a wide range of potential wire formulations, and the narrow selection for fusion may not be applicable to accelerators, condensed matter physics, or other research applications. In this regard, there is a need to guide the development of multiple wire technologies not targeted to just one application area.

The committee also found that solenoid-type magnets (cylindrical in shape) are most efficient at generating magnetic fields. There are numerous synergies that exist in the high-field solenoid space between high-energy physics, high-field science, fusion energy, high-field NMR, and MRI. The emergence of practical HTS superconductors is allowing for the development of higher-field solenoids across these applications.

Although the applications have a variety of HTS conductor requirements, there are many potential areas that could benefit from similar areas of research and development. For example, no-insulation magnets and cables are being developed for fusion magnets that could also be utilized in the high-field solenoids needed for axion searches and muon colliders. These fields will require the commercialization of HTS superconducting wire at scale, the development of prototyping and test facilities, and demonstration magnets. This would benefit from a coordinated effort among

Key Recommendation 3: Within the next 2–3 years, the United States should implement the installation of multiple commercially made nuclear magnetic resonance instruments with magnetic fields in the 1.0–1.2 GHz range covering all applications from physics and materials through pharma and biophysics and onto microimaging, and provide user access to these systems in the democratized science model followed by other national facilities. Such instruments should build on existing infrastructures by relying on centers that have laid out management plans and proven track records of service to the scientific and industrial communities at large.

Achieving this will require locating instruments at a variety of sites in the United States, preferably sites that have active local user communities and adequate staffing and engineering resources to keep the facilities running at a high level for many years. Institutions that receive federal funding for such NMR instruments should be required to set aside 30–50 percent of the instrument time for outside users from academia and industry. In return, federal agencies should contribute to staffing, maintenance, and operation costs every year. A consortium structure, where institutions with these instruments share expertise and coordinate their efforts and decisions in a way that maximizes their combined impact, could be envisioned. Twelve such instruments would bring high-field NMR instrumentation in the United States to approximately the same level as instrumentation in Europe. Support for ancillary equipment, including high-field dynamic nuclear polarization instrumentation, associated research supplies, and helium recycling systems should also be expanded.

Finding: The lack of funding for operation and maintenance of decentralized facilities is a huge drawback for the advancement of high-magnetic-field research in the United States. While the centralized facilities are well funded and operate high-field instruments with no costs for the users, the decentralized facilities in the United States are strongly disadvantaged as they have to currently recover their operation and maintenance by user fees.

Key Recommendation 4: The National Science Foundation, National Institutes of Health, and Department of Energy together should establish an operation funding system similar to what the worldwide competition has established, where part of the experimental time at the decentralized facilities is managed centrally and in return the facilities are provided with funds for operation, maintenance, and further technology development.

National Centers

Finding: NHMFL supports a critical science program for the United States that is effective and produces world-leading science, although with increasing competition from abroad. There is a strong user community accessing both the steady and pulsed field facilities, which are being used to capacity.

Finding: There is a strong need for advanced instrumentation developments associated with all high-field facilities to optimize the scientific and technological output from these facilities.

Modern measurement techniques using scanning probes at the nanoscience level and squeezed and entangled photons, and that are pushed to the limits of quantum measurement, will have impact in condensed matter physics, quantum information science, and molecular and biological systems. Few if any of these instruments are currently available in NHMFL, whereas scanning probe microscopy for high magnetic fields has been developed in China.

Conclusion: The impact of high-field research should be increased by investment in experimental methods to make precise measurements.

Key Recommendation 5: U.S. government agencies, including the National Science Foundation, National Institutes of Health, Department of Energy, and Department of Defense should jointly provide proper resources that are designated to support a team of talents nationally and at the National High Magnetic Field Laboratory to develop state-of-the-art instruments and methods for high-magnetic-field science and technology.

Key Recommendation 6: The United States must establish its leading role in the combination of high-magnetic-field studies with X-ray free lasers (XFELs), synchrotrons, and neutron sources. This could best be accomplished by a National Science Foundation–supported science and technology center focused on the development of novel technology and cutting-edge science applications for quantum and atomic, molecular, and optical high-magnetic-field studies at XFELs, synchrotrons, and neutron sources.

Other User Facilities

Finding: Neutrons and X rays yield insights into entirely new states of matter that cannot be observed by other methods. National facilities for neutrons (the Spallation Neutron Source and the High Flux Isotope Reactor at the Oak

Ridge National Laboratory) and light sources (the Advanced Photon Source operated by Argonne National Laboratory, the Linac Coherent Light Source at the SLAC National Accelerator Laboratory, the National Synchrotron Light Source II at Brookhaven National Laboratory, the Advanced Light Source at Lawrence Berkeley National Laboratory, and the Cornell High Energy Synchrotron Source [CHESS]) are well developed and serve large research communities. The committee welcomes the plans for a 20 T custom magnet at CHESS but notes that provision of high magnetic fields at U.S. facilities is falling behind international competition.

Conclusion: The United States would benefit from establishing a leading role in the combination of high-magnetic-field studies with light sources and neutron sources.

Key Recommendation 7: End stations dedicated to high-magnetic-field research at light sources (from terahertz to X rays, including the Linear Coherent Light Source at the SLAC National Accelerator Laboratory, Stanford Linear Accelerator Center) and neutron sources in the United States should be co-funded by the National Science Foundation, National Institutes of Health, and Department of Energy.

Construction of New World-Leading Magnets

Finding: The United States has led high-magnetic-field research in the past by pushing boundaries but has fallen back in the past decade. There are strong reasons to believe that given the existing expertise in magnets and materials, for example at NHMFL, it is possible to renew the ambitions to move ahead of the competition.

Conclusion: On the basis of its proven track record as the preeminent magnet laboratory in the world, with an interrupted array of record high-field magnets, and of reliable probes and detectors serving the national and international scientific communities for more than two decades, in the next decade, the NHMFL should play a leading role in the construction of several new world-setting magnets. These include upping NHMFL’s present record of 101 T for pulsed fields; upping NHMFL’s present record of 45.2 T for steady-field hybrid magnets; upping NHMFL’s present record of 32 T for an all-superconducting condensed matter physics magnet; and upping NHMFL’s present record of 21 T for small animal (i.e., mice and rats) imaging magnets.

Finding: The highest accessible pulsed field at NHMFL has exceeded 100 T only once and the highest steady field remains 45 T; there has been no progress over at least a decade worldwide. There are substantial scientific advantages to pushing beyond these boundaries. Higher fields are attainable by developing existing technology.

Key Recommendation 8: The National Science Foundation should fund the National High Magnetic Field Laboratory to construct a successor to their 45 T hybrid magnet with the construction of a direct current magnet to reach 60 T and, with the Department of Energy, a pulsed magnet to a field of 120 T.

The committee already recommended the construction of a 14+ T large-bore demonstrator magnet to support fusion science, accelerator science, and ultrahigh-field NMR (see Key Recommendation 2 above).

Finding: While the previous recommendations would restore the competitiveness that the U.S. NMR community has lost over recent decades, additional sources of funding should be made available to pursue “moonshot” efforts restoring the U.S. supremacy in NMR and in magnetic resonance in general.

Key Recommendation 9: The National High Magnetic Field Laboratory demonstrated engineering capabilities that have led to the 36 T SCH magnet and 32 T all-superconducting magnet must be exploited to reach new but achievable thresholds in solid-state nuclear magnetic resonance spectroscopy via the MagLab-based construction of an all-superconducting 40 T system with parts per million homogeneity and sub-parts per million stability. This magnet should be complemented with the microwave and cryogenic capabilities needed for executing in it electron paramagnetic resonance and dynamic nuclear polarization experiments above 1.0 THz.

Finding: MRI and MRS at ultrahigh magnetic fields in humans and animals are a uniquely important tool to advance the understanding of function and physiology throughout the body in a noninvasive manner.

Key Recommendation 10: The National Institutes of Health and National Science Foundation should also launch the development of a ≥28 T small animal magnetic resonance imaging (MRI) system based on combined low-temperature superconductor/high-temperature superconductor inserts, which, in addition to opening new scientific frontiers, would serve as the future human-size, ultrahigh-field MRI platforms. Notice that as similar platforms that serve small rodent MRI and Fourier transform-ion

cyclotron resonance experiments in both homogeneity and bore demands, this system would simultaneously push the frontiers of this important analytical technique.

Key Recommendation 11: Funding agencies supporting basic biological and medical research, such as the National Science Foundation, National Institutes of Health (NIH), and Department of Defense, whose constituencies are interested in ultrahigh-field magnetic resonance imaging (MRI), should consider a joint funding avenue for enabling the United States to implement human MRI at 14 T+, with NIH taking the lead. In addition to the 14 T+ funded by the Dutch consortium, Germany and China will likely follow with their own national efforts, leaving the United States behind if no action is taken.

This report also notes weaknesses in the training of researchers in the NMR cohort, which would be ameliorated by the support of distributed NMR facilities with open access, allowing the development and integration of a research community.

While there are many efforts needed to support a diverse and inclusive community, one of the key ones is to build that community via training and sharing.

Key Recommendation 12: A high-field magnet science and technology training program should be established in the United States. The school could use the U.S. Particle Accelerator School as a model for its organization. Oversight and support should be drawn from a consortium of government agencies, laboratories, and universities, and possibly, industry. The National High Magnetic Field Laboratory could be the initial host site, with the laboratory facilities providing an excellent resource for laboratory courses.

Helium is a critical refrigerant for all current superconducting magnets as well as for experiments that need to operate at ultracold temperatures. Along with the availability of wire and magnet technology, a supply of helium that is uninterrupted (first and foremost) and at a predictable cost are both major constraints on high-magnetic-field science. In Chapter 7, this report endorses recommendations that have already been made in two National Research Council consensus studies on the sale of the National Helium Reserve, The Impact of Selling the Federal Helium Reserve (2000) and Selling the Nation’s Helium Reserve (2010), but as a key recommendation, the committee focuses on a short-term remedy for the high-magnetic-field community.

Finding: The community is justly and deeply concerned by the scarcity and pricing of helium for basic research and for medical practices, because both

use high-magnetic-field instrumentation. The supply uncertainty (i.e., lack of availability and reduction in quantities supplied via contracts) and price fluctuations have harmed the science, technology, and industry communities that need superconducting magnets.

Key Recommendation 13: To secure helium access for research, as a short-term solution, the U.S. government (through the Department of the Interior or potentially the Department of Commerce) should immediately establish a royalty “in-kind” program for helium, whereby vendors extracting helium from federal lands would be required to refine and sell the helium to federally funded researchers. Doing so will enable preferred access to helium for basic research and development for physics, chemistry, biology, materials science, and medical magnetic resonance imaging support.