1

Overview

MAGNETS AND MAGNETIC FIELDS

It is not known when humans first noticed the attraction or repulsion between pieces of magnetic material. The first important device depending on these forces was the magnetic compass, which is believed to have been invented in China around 200 BCE. However, the concept of a magnetic field as a description of the forces felt by magnetic objects, and the laws that govern the interactions between magnetic fields and ordinary matter, were first understood in the nineteenth century. It was shown that an electric current, produced by the motion of electrical charges, will generate a magnetic field in the surrounding space, while an electric charge moving in a magnetic field will feel a physical force in a direction perpendicular to the magnetic field and to the direction of motion.

An electric charge that is completely stationary should generate no magnetic field, nor would it feel a force due a magnetic field generated by other sources. However, according to the laws of quantum mechanics, discovered in the early twentieth century, electrons and nuclei are always in motion, even at zero temperature, and electrons and most nuclei also have an internal rotation (spin), which can generate magnetic fields on the atomic scale. In most materials, the electron spins and other

________________

NOTE: Portions of this and other sections in this chapter have been extracted from National Research Council, 2005, Opportunities in High Magnetic Field Science, The National Academies Press, Washington, D.C.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 5
1 Overview Magnets and Magnetic Fields It is not known when humans first noticed the attraction or repulsion between pieces of magnetic material. The first important device depending on these forces was the magnetic compass, which is believed to have been invented in China around 200 BCE. However, the concept of a magnetic field as a description of the forces felt by magnetic objects, and the laws that govern the interactions between magnetic fields and ordinary matter, were first understood in the nineteenth century. It was shown that an electric current, produced by the motion of electrical charges, will generate a magnetic field in the surrounding space, while an electric charge mov- ing in a magnetic field will feel a physical force in a direction perpendicular to the magnetic field and to the direction of motion. An electric charge that is completely stationary should generate no magnetic field, nor would it feel a force due a magnetic field generated by other sources. How- ever, according to the laws of quantum mechanics, discovered in the early twentieth century, electrons and nuclei are always in motion, even at zero temperature, and electrons and most nuclei also have an internal rotation (spin), which can generate magnetic fields on the atomic scale. In most materials, the electron spins and other NOTE:  Portions of this and other sections in this chapter have been extracted from National Research Council, 2005, Opportunities in High Magnetic Field Science, The National Academies Press, Wash- ington, D.C. 5

OCR for page 5
6 High Magnetic Field Science and I t s A pp l i c a t i o n in the US local currents are oriented in random directions, so they do not produce a magnetic field on the macroscopic scale. However, in certain ferromagnetic materials, such as iron, cobalt, and nickel, the local moments can be aligned by application of a modest magnetic field. In many cases this alignment persists when the applied field is removed, and the result is a permanent magnet, which can then act as a source of magnetic fields by itself. Although permanent magnets made using ferromagnetic materials have many important applications, they are not useful for producing the strongest magnetic fields. The highest magnetic fields currently obtainable from permanent magnets are on the order of 2 tesla. (One tesla, abbreviated T, is equal to 10,000 gauss and is approximately 50,000 times the magnetic field of Earth at a latitude of 50 degrees.) Much higher fields can be produced by electromagnets. Electromagnets can be made of any material that conducts electricity, regard- less of the magnetic properties of its atoms, and they produce magnetic fields whenever an electric current flows through the conductor. Electromagnets are commonly made from multiple coils of a conductor. Since the field contributed by each turn in a coil adds to that of its neighbors, and the field per turn increases with electric current, the more turns in the coil and the greater the current put through it, the stronger the magnetic field that results. All high-field magnets—that is, magnets that generate fields substantially greater than 2 T—are electromagnets. Importance of Strong Magnetic Fields Magnetic fields are central to the operation of many devices crucial for the functioning of a modern society. For example, electric motors and generators of electrical power take advantage, respectively, of the force exerted by a magnetic field on a wire that carries an electric current and of the complementary process whereby electrons in a wire moving across a magnetic field will feel a force that can drive a current along the wire. Other devices, such as read-out heads in magnetic disk memories, depend on magnetic-field-induced changes in the electrical resistance of certain materials, which are used to sense the orientations of the microscopic magnetic domains that encode digital information on the disk. Magnetic resonance imaging (MRI) devices, which are now extensively used for medical applications, take advantage of a different aspect of the interactions between fields and matter. Here, the combined effects of ac and dc magnetic fields on the magnetic moments of the spinning nuclei (particularly protons) in the human body are used to obtain detailed information about the environment of the nuclei, which can distinguish between tissues of different types and can reveal changes due to pathological conditions. For motors and generators and many other electromechanical devices, increases in strength of the magnetic fields employed could lead to important improvements

OCR for page 5
Overview 7 in performance—for example, by achieving more power output in a smaller vol- ume. However, the fields used in these devices are generally limited by practical considerations of cost and weight and do not approach the strengths employed in specialized research applications. By contrast, MRI devices require the highest available fields to achieve satisfactory resolution and sensitivity, and the magnets used in these devices are constantly pushing the limits of magnetic field technology. Very high fields are necessary for many crucial research applications in mate- rials science, chemistry, and biology. The success of these experiments may have major impacts on health care and technology. High magnetic fields in very large volumes are also required for accelerators in high-energy physics and in plasma research aimed at the realization of controlled nuclear fusion. Research using high magnetic fields has proven to be a critical tool in solving problems of technological relevance. High field research has led to an increased understanding of matter, to the discovery of entirely new phenomena, and, sub- sequently, to the development of new devices and products of significant techno- logical and societal importance. Many of the most highly demanded products in today’s marketplace involve technology whose development was enabled, in part, by research using high magnetic fields. And magnetic fields continue to be used to attack many problems of scientific and technological interest. One of the current problems being addressed with high field research is in energy generation and storage. Nuclear magnetic resonance (NMR) has been used as an effective tool to probe the transport of Li ions during charge/discharge cycling of Li batteries, where gaining a fundamental understanding of how Li dendrites grow is necessary to optimize battery design. As another example, ion cyclotron resonance (ICR) has proven to be an essential analytical tool for understanding oil-pipeline-clogging deposits and oil-spill pollution. These are just a couple of examples, and more will be presented in the body of this report. Given the important role that high fields have played in past technological advances, it is a good bet that research involving high magnetic fields will continue to yield technological advances in the future. One indication of the broad range of research dependent on the availability of high magnetic fields may be seen in Figure 1.1, which shows the growth in research reports resulting from use of magnets at the National High Magnetic Field Laboratory (NHFML), during the period 1995-2010, classified by field of research. The categories listed are condensed matter physics and materials, engineering (materials, instrumentation, and magnet technology), biology and biochemistry, chemistry, and geochemistry. Figure 1.1 does not tell us about such key areas of high magnetic field research and applications as high-energy physics accelerators, controlled fusion, and human magnetic resonance imaging, which are not repre- sented at NHMFL. These topics are discussed in Chapters 4, 5, and 7.

OCR for page 5
8 High Magnetic Field Science and I t s A pp l i c a t i o n in the US FIGURE 1.1  Research reports resulting from projects using high-field magnets at the NHFML during the period from 1995 to 2010, classified by field of research. SOURCE: National High Magnetic Field Laboratory. Magnets for High Magnetic Fields Scientists have been building electromagnets that deliver fields of ever-increas- ing strength since the nineteenth century. Two issues have had to be confronted at every step of the way. First, the field of an energized electromagnet exerts forces

OCR for page 5
Overview 9 on its own structure that increase as the square of the field strength and that will destroy it if not contained. Second, if the electrical conductor of which the magnet is made is a normal metal, resistive heating produced by the electric currents can cause the magnet to fail. Beginning in the 1960s, scientists learned how to build magnets using superconducting wires, which can carry a current without resistance at sufficiently low temperatures; however, superconductors have their own limita- tions, as will be discussed later in this report. In particular, all superconducting materials have a critical magnetic field above which they can no longer support resistance-less current flow and cannot be used in magnet construction. A major goal of research in high magnetic fields is to learn how to create superconductors with higher critical fields and to learn how to make magnets out of these materi- als. However, the highest magnetic fields attained to date have been produced by resistive magnets that are operated in a pulsed mode to minimize destructive heating effects. The construction of magnets that operate at high fields is, and has always been, an engineering challenge. In this report, in line with previous studies, the committee defines “high magnetic field magnet” as one whose construction tests the limits of our current technological capabilities. The quantities that determine whether a magnet meets this definition are not just the magnitude of the field itself but include the total energy stored in the field, which is proportional to the integral of the square of the field over the volume affected. Thus an MRI magnet having a maximum field strength of 8 T and a bore large enough to accommodate a human being is as much a high-field magnet as a smaller-bore magnet for an NMR spectrometer operating above 20 T. The highest field attained so far in a dc magnet is 45 T, while pulsed field magnets can operate at 60 T and above. In pulsed-field experiments, there is generally an inverse relationship between the field strength attained and the duration of the pulse. The current record for a nondestructive pulsed magnet is 100 T for a duration of about 10 ms. If partial or total destruction of the magnet coil and/or the sample can be tolerated, fields well above 300 T can be generated for several microseconds. (See Figure 1.2 for a graph of field strengths and available measurement times in various types of high-field magnets, and see Box 1.1 for a list of some other magnetic field strengths.) The technological challenges involved in construction and operation of the various kinds of high-field magnets are discussed in Chapter 7 of this report, along with recommendations of goals for new magnet construction in the coming decade. Facilities and Stewardship Issues Magnets at the high-field frontier are necessarily complex and expensive, both to construct and to operate. High-field magnets require a highly skilled staff to keep them running and to maintain the instruments that make them useful. Serious

OCR for page 5
10 High Magnetic Field Science and I t s A pp l i c a t i o n in the US Destructive pulsed fields Non destructive pulsed fields Hybrid magnets Resistive magnets Superconducting magnets 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 10 102 103 104 105 106 FIGURE 1.2  An overview of magnetic fields available with different technologies, showing the cor- responding rise times for the fields and the times during which experiments in these fields can be performed. SOURCE: Graph courtesy of Jan Cornelis Maan, Radboud University Nijmegen, The Netherlands. safety issues must be addressed in the operation of a high-field facility. In addition, resistive magnets require a large infrastructure to supply needed electric energy and cooling power. For these reasons, it is natural that the highest field magnets should be concentrated at a very small number of national facilities. In the United States, the most advanced facilities are run by the NHFML, which provides user access to dc magnetic fields in Florida and to pulsed fields at Los Alamos National Laboratory in New Mexico (see Figure 1.3). Although there are important high-magnetic-field facilities in many other countries, NHFML is unquestionably the world’s leader in this area. It also plays a crucial role in the train- ing of high-magnetic field scientists and in the development of next-generation magnets and magnetic materials. The leading status of the United States in high- magnetic-field science is due in very large measure to the many contributions of NHFML. There are, however, certain areas where it may be more advantageous to create distributed facilities, able to accommodate large numbers of users. An important example of this is in the field of chemical and biological NMR spectroscopy, where the committee envisions the establishment of several state-of-the-art user facilities

OCR for page 5
Overview 11 BOX 1.1 SOME MAGNETIC FIELD STRENGTHS • In outer space the magnetic flux density is between 10–10 T and 10–8 T. • Earth’s magnetic field at latitude 50 degrees is 5.8 × 10–5 T and at the equator (latitude of 0 degrees), 3.1 × 10–5 T. • The magnetic field of a horseshoe magnet is ~0.1 T. • In a sunspot, the field is 0.15 T. • The magnets in clinical medical MRI spectrometers operate around 4 T; high-resolution MRI operates at 9.4T, and the highest field used for study of a living animal is 21.1 T. • Strongest NMR magnetic field in use: 23.5 T, or 1 GHz (Lyon, France; 2009) • Strongest continuous magnetic field yet produced in a laboratory: —About 26.8 T with a single superconducting magnet (2007), —35.4 T for any superconducting magnet (2011), —36.2 T with a resistive magnet (2010), and —45.2 T with a hybrid magnet (2003). • Strongest (pulsed) magnetic field yet obtained nondestructively in the laboratory: 100.75 T (2012) for ~10 ms. • Strongest (pulsed) magnetic field ever achieved (with explosives) in the laboratory: 2,800 T (Sarov, Russia; 1998). • The field on a neutron star is 106 T to 108 T. • Maximum theoretical field strength for a neutron star, and therefore for any known phenomenon, is 1013 T. around the country. Also, some important applications of high magnetic fields require the combination of high magnetic field with other expensive facilities, which may be best achieved by the deployment of a specialized magnet at an exist- ing facility such as a synchrotron light source or a neutron source. As mentioned above, the very highest magnetic fields for research are neces- sarily restricted to purpose-built facilities, which require significant infrastructure investments. In the United States, these research capabilities are available at the NHMFL, with operational support from the National Science Foundation (NSF). Because high magnetic field science is inherently multidisciplinary, effective stew- ardship of a major user facility like the NHMFL is critical to the vitality of the scientific enterprise. These facilities must be managed and operated in the most robust manner to provide the strongest possible scientific impact to the research community. This means that attention must be paid to (1) how the facilities are managed, (2) the roles and responsibilities of the federal agencies that steward them, and (3) the partners that join with the steward to leverage them for maxi- mum impact. In addition to making available the highest fields, it is also desirable to translate proven magnet technology to decentralized facilities where appropriate

OCR for page 5
12 High Magnetic Field Science and I t s A pp l i c a t i o n in the US FIGURE 1.3  The NHMFL is the principal high magnetic field research laboratory in the United States. It is located on three campuses—Florida State University in Tallahassee, site of its general head- quarters and much of its research facilities; the University of Florida in Gainesville, Florida, site of its low-temperature and advanced MRI programs; and Los Alamos National Laboratory in Los Alamos, New Mexico, where its pulsed magnetic field facility is located. (Clockwise starting from the top left) Users at the laboratory’s 21.1 T 900 MHz ultra-wide-bore magnet. (Top center) A user prepares an experiment at the MagLab’s High B/T facility in Gainesville, Florida. (Top right) A technician keeps close tabs on the magnets in the control room of the dc field facility. (Middle right) The MagLab’s 45 T hybrid magnet, which holds the record for highest magnetic field for a continuous field magnet. (Bottom right) Amy McKenna, a staff chemist at the ICR facility, examining the flow of a sample in the ion cyclotron resonance magnet. (Bottom center) The 25 T split coil magnet at the MagLab’s dc field facility. (Bottom left) The main sign of the MagLab. SOURCES: (Top left) Photo taken by Ray Stanyard, provided courtesy of NHMFL; (top center) photo taken by Dave Barfield, provided courtesy of NHMFL; (top right) photo courtesy of the NHMFL; (middle right) photo taken by Ray Stanyard, provided cour- tesy of NHMFL; (bottom right) photo courtesy of the NHMFL; (bottom center) photo taken by Dave Barfield, provided courtesy of NHMFL; (bottom left) photo courtesy of the NHMFL.

OCR for page 5
Overview 13 and technically and economically feasible. Furthermore, the long-term viability of this field of research is contingent upon the availability of a workforce capable of advancing the technological frontiers in magnet development. Education and train- ing at the graduate and postgraduate levels are important to ensure this viability. Issues of stewardship and of management of high-field facilities in the United States will be addressed, in some detail, in Chapter 9 of this report. Also, in Chapter 8, this report surveys high magnetic field facilities in foreign countries as well as in the United States and addresses some of the common issues involved in running such facilities. Chapter 8 also explores opportunities for cooperation between laboratories and between nations. Science Drivers Before discussing in detail the vital issues of organization, construction, and stewardship of high-magnetic-field facilities, the committee presents an overview of some of the science drivers that make high-magnetic-field science so impor- tant. Chapter 2 discusses the role of high magnetic fields in condensed matter and materials physics. Chapter 3 is devoted to the use of high magnetic fields for NMR, electron paramagnetic resonance (EPR), and ICR, in chemistry, biochemistry, and biology. Chapter 4 discusses the advantages that could be gained by using higher magnetic fields for MRI and magnetic resonance spectroscopy (MRS) for medical research on human subjects and proposes development of a 20 T magnet suitable for this purpose. Chapter 5 outlines the use of high magnetic fields in accelerator- based high-energy physics experiments and in confined-plasma controlled fusion projects. It also discusses the proposed development of compact superconducting cyclotrons for radiotherapy using charged particles and the possible use of higher magnetic fields in astrophysical particle detectors. In several important research areas, it is necessary to combine magnetic fields with measurement tools that are themselves highly complex and expensive and that may be available only at specialized facilities. For example, experiments may require use of magnetic fields in conjunction with X-ray or neutron scattering facilities available at a synchrotron, nuclear reactor, or spallation source. Other experiments require that intense photon sources in the terahertz range be combined with high magnetic fields. As will be discussed in Chapter 6, improvements in the availability of high magnetic fields in combination with neutron and photon sources in the United States will be necessary if the nation is to maintain a leading role in these fields.

OCR for page 5
14 High Magnetic Field Science and I t s A pp l i c a t i o n in the US Principal Conclusions and Recommendations The committee rounds out this overview chapter with a brief discussion of the principal conclusions and recommendations contained in this report. Numbers in parentheses refer to the chapters where the conclusions and recommendations appear. Supporting material for each of the conclusions and recommendations may be found in the discussions preceding them in those chapters. Centralized and Distributed Facilities First and foremost, the committee emphasizes that the status of high-magnetic- field science is very strong, and that this strength is due in large measure to the leadership role of the NHFML. A centralized national user facility that provides the highest magnetic fields in the world for the purposes of research offers numerous benefits to the scientific community; it is an essential part of our national prestige and, as a centralized entity, is a cost-effective resource (more so than an equiva- lent decentralized set of capabilities). The NHMFL provides high-magnetic-field measurement capabilities that are simply not available anywhere else in the United States. Indeed some of the NHMFL’s measurement capabilities cannot be matched anywhere else in the world. By offering these capabilities to the U.S. scientific com- munity, it enables cutting-edge research and enhances the nation’s competitiveness. These magnets, and the associated scientific experiments requiring these fields, depend on a substantial infrastructure such as electricity and cooling. Locating these at a centralized facility, such as at the NHMFL, is a highly cost-effective approach. Moreover, developing high-field magnets requires a special and rare combination of expertise in and extensive knowledge of materials properties, phys- ics, electrical engineering, mechanical engineering, and engineering design. Fur- thermore, locating these magnet developers at a centralized facility is cost-effective and ensures that they are well connected to the needs of a national user facility. Conclusion: There is a continuing need for a centralized facility like the NHMFL because (1) it is a cost-effective national resource supporting user experiments and thus advancing the scientific frontiers and (2) it is a natural central location with expert staff available to develop the next generation of high-field magnets. (9) Recommendation: The National Science Foundation should continue to provide support for the operations of the NHMFL and the development of the next generation of high-field magnets. (9)

OCR for page 5
Overview 15 On the other hand, there are several areas where decentralization may be advantageous. For example, assuming successful completion of the 32 T all-super- conducting magnet under development at the NHMFL, one can envision a time shortly thereafter when this technology becomes available as a standard commercial product. At that time, it might be feasible to consider establishing satellite magnet user facilities at locations distributed around the country. The 32 T magnet technol- ogy would provide the basis for these satellite sites, since they will not require the extensive infrastructure required to power, cool, operate, and maintain the direct currect (dc) resistive magnets. Conclusion: There are benefits to decentralized facilities with convenient access to high magnetic fields for ongoing scientific research. Such facilities need not engage in expanding the frontiers of high magnetic field science nor lead the way in new magnet technology; instead, they should provide the broad user community with the up-to-date high-field magnets to relieve the shortage of user time at the NHMFL-style central facility. (9) Recommendation: Taking into account, among other factors, the estimated costs and anticipated total and regional demand for such facilities, federal funding agencies should evaluate the feasibility of setting up some smaller regional facilities, ideally centered around 32 T superconducting magnets as the technology becomes available, and with optimized geographic locations for easy user access. These would be in addition to the premier centralized facility, which would remain, with its unique mission of expanding the fron- tiers of high magnetic field science. (9) Nuclear Magnetic Resonance Spectroscopy Facilities NMR spectroscopy is another field where decentralized facilities are necessary. At the same time, substantial government support will be necessary if the United States is to retain leadership in the field. Conclusion: Nuclear magnetic resonance (NMR) spectroscopy is one of the most important and widely used techniques for structural, dynamical, and mechanistic studies in the chemical and biological sciences. However, in recent years, U.S. labs have failed to keep up with advances in commercial NMR mag- net technology. If this trend continues, the United States will probably lose its leadership role, as scientific problems of greater complexity and impact are solved elsewhere. (3)

OCR for page 5
16 High Magnetic Field Science and I t s A pp l i c a t i o n in the US The report calls specifically for the funding of at least three magnets suitable for NMR spectroscopy at a proton NMR frequency of 1.2 GHz (28.2 T). As the cost of such a magnet is approximately $20 million, and there is currently no mechanism by which funds on this scale can be obtained through the conventional peer-review processes at NIH or NSF or DOE, new mechanisms are needed to fund and site high-field NMR systems in the United States. Recommendation: New mechanisms should be devised for funding and sit- ing high-field NMR systems in the United States. To satisfy the likely demand for measurement time in a 1.2 GHz system, at least three such systems should be installed over a 2-year period. These instruments should be located at geo- graphically separated sites, determined through careful consultation with the scientific community based on the estimated costs and the anticipated total and regional demand for such instruments, among other factors, and managed in a manner that maximizes their utility for the broad community. Moreover, planning for the next-generation instruments, likely a 1.5 or 1.6 GHz class system, should be under way now to allow for steady progress in instrument development. (3) Combining Magnetic Fields with Scattering Facilities and Terahertz Radiation Magnets for neutron or X-ray scattering experiments need to be built and operated at existing facilities that can provide neutrons or photons. High magnetic fields would provide an important complement to the recent advances in scatter- ing capabilities in the United States. It is also important to construct a facility that combines a powerful source of terahertz radiation with high magnetic fields, since typical resonance frequencies of electrons fall in this range for fields above 20 T. Recommendation: New types of magnets should be developed and imple- mented that will enable the broadest possible range of X-ray and neutron scattering measurements in fields in excess of 30 T. This requires, as a first step, the expeditious procurement of modern 10-16 T magnet/cryostat sys- tems for U.S. facilities, together with the recruitment of low-temperature/ high-field specialists. Second, a 40 T pulsed-field magnet should be developed with a repetition rate of 30 s or less. Third, building on the development of a high-temperature all-superconducting magnet, which was recommended earlier, a wider-bore 40 T superconducting dc magnet should be developed specifically for use in conjunction with neutron scattering facilities. New partnerships among federal agencies, including the Department of Energy, the National Institute of Standards and Technology, and the National Science Foundation, will likely be required to fund and build these magnets, as well

OCR for page 5
Overview 17 as to provide the funds and expertise that will be needed to operate these facilities for users once they are built. (6) Recommendation: A full photon spectrum, covering at least all of the ener- gies (from radio-frequency to far infrared) associated with accessible fields, should be available for use with high magnetic fields for diagnostics and control. At any point in the spectrum, transform-limited pulses of variable amplitude, allowing access to linear and nonlinear response regimes, should be provided. Consideration should be given to a number of different options, including (1) providing a low-cost spectrum of terahertz radiation sources at the NHMFL, (2) construction of an appropriate free electron laser (FEL) at NHFML, or (3) providing an all-superconducting, high-field magnet at a centralized FEL facility with access to the terahertz radiation band. (6) Specific Magnet Goals To maintain its leadership, it is essential that the United States support ambi- tious goals for the construction of new magnets that would extend the frontiers of high-field research in several directions. Recommendation: A 40 T all-superconducting magnet should be designed and constructed, building on recent advances in high-temperature super- conducting magnet technology. (7) Recommendation: A 60 T dc hybrid magnet should be designed and built that will capitalize on the success of the current 45 T hybrid magnet at the NHMFL-Tallahassee. (7) Recommendation: Higher-field pulsed magnets should be developed, together with the necessary instrumentation, in a series of steps, to provide facilities available to users that might eventually extend the current suite of thermal, transport, and optical measurements to fields of 150 T and beyond. (7) Magnetic Resonance Imaging Magnet Development Significantly increased field strengths available for MRI and NMR spectroscopy on humans and large animals could enable a number of important advances in medical science. The committee finds that current barriers in MRI medical sci- ence research motivate an initiative to develop a 20 T magnet that can image and perform spectroscopy on the human head, large animals, and plants. Although

OCR for page 5
18 High Magnetic Field Science and I t s A pp l i c a t i o n in the US this development would not be for clinical applications, the research could lead to important clinical benefits. Recommendation: A design and feasibility study should be conducted for the construction of a 20 T, wide-bore (65 cm diameter) magnet suitable for large animal and human subject research. The required homogeneity is 1 ppm or better over a 16 cm diameter sphere. The appropriate sponsor- ship might be multiple agencies (e.g., NIH, NSF, and DOE). In parallel, an engineering feasibility study should be undertaken to identify appropriate RF, gradient coils, and power supplies that will enable MRI and MRS and an extension of current health and safety research currently being conducted at lower fields. (4) Stewardship The report addresses a number of issues on stewardship needs for the NHMFL and the workforce that makes NHMFL’s continued success possible. The basis for these conclusions and recommendations is discussed in detail in Chapter 9. Conclusion: Recompetition on timescales as short as 5 years places at risk the substantial national investment in high-field research that is embodied in a national facility like NHMFL and could have disastrous effects on the research communities that rely on uninterrupted access to these facilities. Although this committee believes that recompetition of facilities is appropriate, it also believes a flexible approach should be taken in the implementation of recom- petition of the NHMFL to fulfill the role as a steward and to avoid potential negative consequences of a short time interval between recompetitions. (9) Conclusion: The committee strongly endorses the consideration given to this matter by the Subcommittee on Recompetition of Major Research Facilities.1 It endorses the need for evaluating the long-term strategy and direction of national facilities, as well as for effective periodic reviews of their scientific programs. (9) Recommendation: NSF, the NHMFL, and other interested entities that ben- efit from the use of high magnetic fields should adopt the steward-partner model as the basis for defining the roles in future partnerships in high- magnetic-field science. For magnets not sited at NHMFL, the host institution 1  Report of the Subcommittee on Recompetition of Major Research Facilities, NSF Business and Operations Advisory Committee, January 5, 2012.

OCR for page 5
Overview 19 is in most cases the natural steward, especially for the significant facility- specific infrastructure required for magnet operations. For magnets sited at the NHMFL, NSF should be the steward, although the partner organization could fund the construction and operation of these facilities. (9) Recommendation: A high field-magnet science and technology school should be established in the United States. The school could use the U.S. Particle Accelerator School (USPAS) as a model for its organization. Oversight and support should be drawn from a consortium of government agencies, labo- ratories, and universities, and—possibly—industry. The NHMFL could be the initial host site, with the laboratory facilities providing an excellent resource for laboratory courses. (9) International Cooperation The small community of high-field facilities that exist worldwide has a good record of scientific collaboration and competition that is and will remain important in advancing magnet technology and producing scientific results. Success requires that these large facilities should have a threefold mission: (1) to generate the high- est possible magnetic fields, by developing new magnets needed to produce those fields (magnet technology); (2) to make these fields, together with experimental support and expertise, available to qualified external users (act as a facility); and (3) to perform world-class research led by the facilities’ staff. Recommendation: High-field facilities worldwide should be encouraged to collaborate as much as possible to improve the quality of magnets and service for users. This can be accomplished through the establishment of a global forum for high magnetic fields that consists of representatives of large magnetic field facilities from all continents. Such a forum would fur- ther stimulate collaboration and the exchange of expertise and personnel, thereby providing better service to the scientific community and magnet technology development. The forum should establish a roadmap for future magnets and stimulate the realization of the defined targets on this road- map. (8) Recommendation: Large high-magnetic-field facilities should also have strong collaborations with smaller regional centers, providing them with support and expertise. Users of these regional centers may need the higher fields available in the large facilities, while users of the large facilities could be referred to the regional centers if their proposed experiments are better suited for those centers. (8)