3

Societal Applications and Benefits

Nuclear physics is ubiquitous in our lives: Detecting smoke in our homes, testing for and treating cancer, and monitoring cargo for contraband are just some of the ways that nuclear physics and the techniques it has spawned make a difference in our safety, health, and security. Many of today’s most important advancements in medicine, materials, energy, security, climatology, and dozens of other sciences emanate from the wellspring of basic research and development in nuclear physics. Answers to some of the most important questions facing our planet will come from nuclear science, interdisciplinary efforts in energy and climate, and marketplace innovations. The economic impact of the applications of nuclear physics is significant. As an example, particle beams from accelerators are used to process, treat or inspect a wide range of products with a collective value of more than $500 billion.1 At the same time, approximately 23 million nuclear medicine procedures are carried out each year in the United States to diagnose and treat cancers, cardiovascular disease, and certain neurological disorders. In the future, basic nuclear science will be a key discipline that provides ideas and insights leading to the intellectual properties and patents with which venture capitalists and entrepreneurs will shape the economies of the future.

Between the chapters of this document the committee has highlighted some of the ways that nuclear physics impacts our lives along with some of the individuals poised for leadership in nuclear physics. In this chapter we provide a more detailed

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1 Department of Energy, 2010, Accelerators for America’s Future, Washington, D.C. Available at http://www.acceleratorsamerica.org/report/index.html; last accessed August 31, 2011.



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3 Societal Applications and Benefits Nuclear physics is ubiquitous in our lives: Detecting smoke in our homes, test- ing for and treating cancer, and monitoring cargo for contraband are just some of the ways that nuclear physics and the techniques it has spawned make a difference in our safety, health, and security. Many of today’s most important advancements in medicine, materials, energy, security, climatology, and dozens of other sciences emanate from the wellspring of basic research and development in nuclear physics. Answers to some of the most important questions facing our planet will come from nuclear science, interdisciplinary efforts in energy and climate, and marketplace innovations. The economic impact of the applications of nuclear physics is signifi- cant. As an example, particle beams from accelerators are used to process, treat or inspect a wide range of products with a collective value of more than $500 billion.1 At the same time, approximately 23 million nuclear medicine procedures are car- ried out each year in the United States to diagnose and treat cancers, cardiovascular disease, and certain neurological disorders. In the future, basic nuclear science will be a key discipline that provides ideas and insights leading to the intellectual properties and patents with which venture capitalists and entrepreneurs will shape the economies of the future. Between the chapters of this document the committee has highlighted some of the ways that nuclear physics impacts our lives along with some of the individuals poised for leadership in nuclear physics. In this chapter we provide a more detailed 1  Department of Energy, 2010, Accelerators for America’s Future, Washington, D.C. Available at http:// www.acceleratorsamerica.org/report/index.html; last accessed August 31, 2011. 153

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154 Nuclear Physics overview of some of the ways in which nuclear physics is being applied to address the nation’s challenges in health, homeland and national security, nuclear energy, and some of the innovations taking place in developing and exploiting new tech- nologies arising from nuclear science. DIAGNOSING AND CURING MEDICAL CONDITIONS Nuclear physics techniques have been revolutionary in medical diagnostics and cancer therapy. Of the 23 million nuclear medicine imaging and therapeutic procedures performed each year in the United States, typically 40-50 percent are for cardiac applications, while 25-40 percent are for cancer identification and therapy. In addition, nuclear medicine procedures are used to diagnose Alzheimer’s disease, treat hyperthyroidism, assess coronary artery disease, localize tumors, and diagnose pulmonary emboli. The science of nuclear medicine, however, goes far beyond the radiopharma- ceuticals used for imaging and treatment. Advances in the field are inevitably tied to basic research in nuclear physics at all levels. These advances include accelerators, detectors, understanding the interaction of radiation with matter, and creating complex statistical algorithms for identifying relevant data. Nuclear Imaging of Disease and Functions Over the past few decades, new nuclear imaging technologies have enhanced the effectiveness of health care and enabled physicians to diagnose different types of cancers, cardiovascular diseases, and neurological disorders in their early stages. Today there are over 100 nuclear imaging procedures available. These procedures have the additional advantage of being noninvasive alternatives to biopsy or sur- gery. Unlike other imaging procedures that are designed mainly to identify struc- ture, nuclear medicine can also provide information about the function of virtually every major organ system within the body. The most important modern advances in nuclear imaging are positron emission tomography (PET) and single-photon emission computed tomography (SPECT). PET, especially when coupled to X-ray computed tomography (CT) scans, has become a highly sensitive probe of abnormal functions, as described in detail in the PET highlight between Chapters 2 and 3. 18F-fluorodeoxyglucose (18F-FDG) is a radiopharmaceutical used in medical- imaging PET scans. This is a glucose analog that is absorbed by cells such as those in the brain and kidneys as well as cancer cells, which use high amounts of glucose. This procedure yields scans such as those displayed in Figure 3.1 and can be used for the study of organ functions and, in the case of cancer cells, for therapeutic applications. The 1.8-hour half-life t1/2 of fluorine-18 results in very high specific

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S o c i e t a l A pp l i c a t i o n s and Benefits 155 FIGURE 3.1  PET is a powerful tool to probe the functions of the brain. In these images of the brain, the radionuclide is fluorine-18 while the molecules for each image obviously have different biodistribu- tions. The left-hand figure shows fluorodopa (to probe dopamine integrity) while the right-hand figure shows fluorodeoxyglucose (to probe sugar metabolism). SOURCE: Courtesy of Don Wilson, British Columbia Cancer Agency. activity with no long-term residual activity in the body. However, the short lifetime means that fluorine-18 and 18F-FDG have to be produced very near to where the procedures are to be performed. This often requires in situ small-scale particle accelerators, another capability developed by nuclear physicists, to produce the isotope. Radionuclides that emit gamma-rays have a long history as imaging tools in the diagnosis of cancer. SPECT has been built around the gamma-ray associated with the decay of molybdenum-99. Molybdenum-99 decays (t1/2 = 66 hours) into an isomer of technetium-99m (m indicating metastable), which in turn decays (t1/2 = 6 hours) by emitting a 140-keV gamma-ray. The cameras for this imaging technique are typically made with a cluster of photomultipliers coupled to a large NaI crystal. In recent years, the semiconductor material CdZnTe (CZT) has gained favor because of its higher energy resolution. Having this type of capability means that multiple tracers can be imaged simultaneously through the use of different energy windows. In North America, the main radioisotopes needed for imaging and treatment are produced by the Isotope Development & Production for Research and Appli- cations (IDPRA) program, in the Nuclear Physics Program of the Department of

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156 Nuclear Physics Energy’s (DOE’s) Office of Science, and by two Canadian facilities, TRIUMF and Chalk River. Worldwide, the molybdenum-99/technetium-99m radionuclide pair is used in four out of five, or in about 12 million diagnostic-imaging procedures in nuclear medicine every year. However, the reactors that have been producing molybde- num-99 are approaching the end of their useful lives, which is expected to trigger an “isotope crisis.” One of the reactors, the Canadian National Research Uni- versal (NRU) reactor at Chalk River, is scheduled to stop isotope production in 2016, while potential replacement reactors around the world may not be available until 2020. Research is now focused on exploring accelerator-based production of molybdenum-99 as an alternative technology using, among other reactions, the 100Mo(g,n)99Mo and the 100Mo(p,2n)99mTc reactions. Another option centers on rhenium-186, which has a favorable half-life (t1/2 = 90 hours) and emits beta decay electrons of 0.9 MeV with a 10 percent branch emit- ting a gamma-ray with energy similar to that of technetium-99m. Since rhenium is in the same chemical family as technetium, much of the technology developed for technetium-99m can be applied to rhenium-186. Current efforts are concen- trated on reactor production of rhenium-186 via the 185Re(n,g) reaction, followed by mass separation to yield a sample with the high specific activity needed for therapy (see Box 3.1). New Radioisotopes for Targeted Radioimmunotherapy Radiopharmaceuticals have been developed that can be targeted directly at the organ being treated. These therapy radiopharmaceuticals rely on the destructive power of ionizing radiation at short ranges, which minimizes damage to neighbor- ing organs. A frontier direction is targeted radiopharmaceuticals. This involves attaching a relatively short-lived radioactive isotope that decays via high-energy transfer radia- tion (alpha-particle emission, for example) to a biologically active molecule, like a monoclonal antibody that has a high affinity for binding to receptors on cancer tumors. When the radioactive nuclei decay, the radiation they produce loses energy quickly and because it does not travel far, a lethal dose of radiation is delivered only to adjoining tumor cells. By careful construction of the targeting molecule, the radioactive nuclei will pass through the body quickly if they do not bind to tumor cells, thus minimizing the exposure of healthy tissue to the high-energy transfer radiation. Presently, the most common radionuclides are iodine-131 and yttrium-90, though neither is ideal. Two radiopharmaceuticals, Bexxar (using iodine-131) and Zevalin (using indium-111 or yttrium-90), are now in use to treat non-Hodgkins lymphoma. Many research efforts are focused on the production of alternative isotopes

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S o c i e t a l A pp l i c a t i o n s and Benefits 157 BOX 3.1 Suzanne Lapi and Radionuclide Production Suzanne Lapi is a leader in the effort to develop rhenium-186 for radiation therapy. After receiving her master of science and Ph.D. degrees from Simon Fraser University, British Columbia, she pursued research into the production of rhenium-186 of high specific activity to enhance the therapeutic efficacy of this promising radionuclide. After concluding that accelerator production was not optimal, she focused on increasing specific activity of rhenium-186, produced in a reactor by the 185Re(n,g) reaction, by mass separation of the postirradiated material. This work is the sub- ject of a patent and is also being applied to increasing the specific activity of molybde- num-99, also produced via the (n,g) reaction. Presently Dr. Lapi is an assistant professor at the Mallinckrodt Institute of Radiology at Washington University in St. Louis, Missouri. She is a project leader on radionuclide re- search for cancer applications, oversees pro- duction of nonstandard PET radionuclides, and collaborates with internal and external faculty on grants supported by both DOE and the National Institutes of Health (NIH). FIGURE 3.1.1  Suzanne Lapi. Source Photo courtesy of MIR Photography with superior cytotoxicity for use in therapy. A promising class of isotopes is those that decay by alpha emission, since alpha particles have a very short range in tissue, resulting in an enhanced cytotoxicity. The radionuclide actinium-225 combines several favorable properties, including a half-life of 10 days, high alpha-particle energy, versatile coordination chemistry, and several alpha-emitting daughter iso- topes. Actinium-225 has been used in Phase I and II clinical trials; it is presently being produced at Oak Ridge National Laboratory (ORNL) and at the Institute for Transuranium Elements in Karlsruhe, Germany. Its availability, however, is currently limited, and alternative production mechanisms are being investigated at the Los Alamos National Laboratory (LANL) isotope production facility. More recently, researchers at the Karlsruhe Institute in Germany have reported the efficacy of treating neuroendocrine tumors with the alpha-emitting bismuth-213 nucleus attached to a biological molecule (called DOTATOC) that targets these

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158 Nuclear Physics particular tumors. They found that the tumors of seven out of nine patients had become smaller with no discernible negative side effects. If this approach can be validated and brought into routine use, the treatment of cancer will have had a major paradigm shift. In the coming decade, nuclear physics facilities will continue to broaden the range of isotopes for medical applications. For example, the Facility for Rare Iso- tope Beams (FRIB) at Michigan State University (MSU) will be capable of produc- ing shorter-lived isotopes of key elements for more rapid dose kinetics and new medical applications. Future Technologies in Nuclear Medicine The future impact of nuclear science on medical science is difficult to predict. If history is an indicator, one can expect more significant and exciting contributions. At the least, advances in nuclear medicine will likely remain closely connected with advances in nuclear techniques. One future direction is personalized medicine, the attempt to identify and treat disorders based on an individual’s response to the disease process. This will require more sophisticated nuclear tools. As an example, chemistry systems will be reduced to the size of a postage stamp, thus making patient-specific diagnostic tools and treatment truly individualized. An example of an integrated device, designed for multistep radiosynthesis of PET tracers, is displayed in Figure 3.2. Other important new directions involve the coupling of advances in geneti- cally engineered antibodies with radionuclides and the use of nuclear imaging to help us understand the underlying causes of disease by extracting functional and anatomical information in the same image. MAKING OUR BORDERS AND OUR NATION MORE SECURE Nuclear science has a long tradition in national security, from the Manhattan Project to today’s focus on homeland security. Nuclear devices have determined the outcome of wars and changed the political boundaries of the world. Today, nuclear science plays a critical role in global politics: It protects the borders of the United States, safeguards nuclear material and forestalls the proliferation of nuclear weapons, prevents nuclear terrorism (while at the same time preparing for the “unthinkable”), and ensures that the nation’s nuclear weapons stockpile is reliable. The past decade has seen an expansion in the types of nuclear security prob- lems facing society. For example, considerable effort has been devoted to exploit- ing new concepts for nuclear forensics and for border protection. At the same time, traditional fields, such as stockpile stewardship and reactor safeguards, have more needs than ever. The contributions from the nuclear physics community to

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S o c i e t a l A pp l i c a t i o n s and Benefits 159 FIGURE 3.2­  Future technologies in personalized medicine will require smaller patient-specific diag- nostic tools. An example is the chemistry system being designed to produce multiple human doses of FDG, an analog for glucose, on a chip the size of a U.S. penny. In this figure the chip has channels for introducing reagents, channels for opening and closing “pressure valves” by introducing fluids, and channels for venting to allow fluid flow. Flow channels are filled with green dye, control channels with red, and vent channels with yellow. The circle in the center is the reaction chamber. Such devices will reduce time and quantity of reagents and increase efficiency. SOURCE: Courtesy of Arkadij M. Elizarov, Siemens Healthcare. © Copyright Siemens Healthcare 2012. Used with permission. all of these issues have been both numerous and broad, and a significant number of nuclear physics graduate students express an interest in pursuing careers that address these issues. Protecting Our Borders from Proliferation of Nuclear Materials Border Detection of Nuclear Contraband The priority mission of our nation’s Border Patrol is preventing terrorists and terrorists’ weapons, including weapons of mass destruction, from entering the United States. Currently there are radiation portal monitors installed at approxi- mately 300 ports of entry. These monitors detect gamma-rays and neutrons emitted from nuclear material. However, one can shield such radiation from detection by

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160 Nuclear Physics placing absorbing material around the nuclear material being smuggled. To deal with such shielding, numerous research groups at universities and national labs are exploring novel detection schemes. One such scheme scans for high-atomic-number (high-Z) materials hidden in vehicles using cosmic ray muons. As energetic cosmic rays impinge on Earth’s atmosphere, they collide with nuclei in the atmosphere to produce copious quanti- ties of muons. Because muons do not interact strongly with the atmosphere, many reach Earth’s surface and even penetrate for some distance into shallow mines. Muon radiography takes advantage of this penetrability and is designed to measure the scattering of these muons as they pass through motor vehicles at border inspec- tion stations as a means of detecting hidden nuclear contraband. As sketched in Figure 3.3, the muons are detected both above and below the vehicle. The muons interact with matter in two ways: (1) with atomic electrons, which results in con- tinuous energy loss, and (2) with the atomic nuclei, which results in large angle changes in the muon’s path. Each of these interactions provides a radiographic signal that can be used to characterize the material inside a truck. For example, very large angle scattering is a signal that the truck contains high-Z material, such as FIGURE 3.3  Muons passing through high-Z materials (like uranium and plutonium) are scattered more than those passing through other materials (such as steel or water). Cosmic ray muons can therefore be used as an active interrogation probe of nuclear materials by detecting muons above and below a truck. SOURCE: Courtesy of C.L. Morris, Los Alamos National Laboratory (LANL).

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S o c i e t a l A pp l i c a t i o n s and Benefits 161 uranium or plutonium. Muon radiography is proving to be a very efficient border protection tool, and experiments have shown that even high-Z material hidden inside the engine of a vehicle is readily detectable. Nuclear Safeguards The International Atomic Energy Agency’s (IAEA’s) safeguards system under the Treaty on the Non-Proliferation of Nuclear Weapons, also known as the Nuclear Nonproliferation Treaty (NPT), is aimed at preventing the diversion of civilian nuclear material into military uses. The IAEA safeguards also include schemes for detecting undeclared nuclear activities, such as illicit operations of nuclear reac- tors. By signing the NPT Treaty, all of the (currently 184) nonnuclear states agree to IAEA safeguard inspections of their nuclear facilities. One of the very challenging problems for the IAEA is protecting against repeated thefts of small quantities of material over extended time periods. Account- ability safeguards largely rely on the detection of gamma-rays and neutrons from nuclear materials, which can be used to deduce inventory anomalies or materials in unauthorized locations. An important component of these schemes is the cou- pling of advanced radiation detection physics with large nuclear decay databases (and their uncertainties). Scientists at Lawrence Livermore National Laboratory (LLNL) have demonstrated the practicality of gamma-ray nondestructive isotopic measurements using high-purity germanuim (HPGe) gamma-ray detectors. For homogenous materials, one HPGe detector is sufficient to extract isotopic ratio information; for inhomogeneous materials, external transmission sources and multidetector tomography scanning are needed. Certifying the Nation’s Nuclear Stockpile What Happens When Neutrons Interact with Actinides? To enable certification of the nation’s stockpile in the absence of nuclear test- ing, a number of nuclear physics measurements, coupled with supporting nuclear theory, are being carried out at university and national laboratories. Many of these studies involve neutron-induced cross sections on fissionable actinides (the 14 chemical elements with atomic numbers from 90 to 103, including uranium and plutonium) and other materials that might be found in a nuclear device. Also of importance is the detailed characterization of the energy resulting from fission and fusion. Current uncertainties on the important fission cross sections for stockpile stew- ardship are on the order of 2 to 3 percent. In the case of plutonium-239, it would

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162 Nuclear Physics be ideal if this uncertainty were reduced to 1 percent, an improved accuracy also important in developing next-generation reactors. Achieving this level of accuracy requires overcoming uncertainties associated with past fission ionization cham- ber measurements. Accordingly, a team of LLNL, LANL, and university scientists is developing a fission time projection chamber (TPC), sketched in Figure 3.4, that will be capable of three-dimensional event reconstruction with a high back- ground rejection. Once completed, this will represent a major advance in fission physics. Understanding fission cross sections, especially on actinides other than uranium-235, uranium-238, and plutonium-239 is also important for developing the next generation of nuclear reactors. In addition to fission, several other neutron-reaction cross sections are needed for stockpile stewardship. Perhaps the most important of these is neutron capture in the tens to hundreds of keV neutron energy region. There is an ongoing neu- tron capture program involving university and national laboratory scientists and FIGURE 3.4  TPCs are sensitive instruments in basic research in high-energy and nuclear physics used, for example, in the solenoidal tracker at RHIC (STAR). A new application of a TPC is being developed to enable measurements of neutron-induced fission probabilities of actinides with unprecedented accuracies. The TPC will measure the energy, mass, and direction of fission fragments. Upgrades to the baseline TPC, including additional detectors, would also measure the energy, direction, and multiplicities of fission neutrons and will be able to correlate gamma-radiation with fission events. Such measurements of fission probabilities and properties are important in a wide range of disciplines including nuclear energy, nuclear forensics, national security, and basic nuclear science. SOURCE: Courtesy of M. Heffner, LLNL.

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S o c i e t a l A pp l i c a t i o n s and Benefits 163 the 4-p BaF2 Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos Neutron Science Center (LANSCE). As an example, some amount of americium-241 is present in all weapons-grade plutonium, and reactions on americium-241 are an important diagnostic for weapon performance. Because the americium-241(n,g) reaction is important for nuclear forensics, there is a close synergy between the stockpile stewardship and nuclear forensics efforts. DANCE is also used to measure neutron cross sections on unstable targets important for s-process nucleosynthesis. The extreme conditions in a nuclear explosion result in many of the reactions taking place on unstable nuclei. In the coming decade, access to a much broader range of important unstable isotopes will become possible as FRIB comes online. For many short-lived isotopes, direct measurements will provide information on key reactions of interest. However, it will not be possible to measure all of the relevant reactions, and for the very shortest-lived isotopes theory and simulations will be necessary. FRIB data from related reactions will provide important bench- marking and tests of theory, thus lending confidence to the predictions for the very short-lived unstable isotopes. Using Protons to See Where Light Can Never Shine Over the last decade, proton radiography has become an increasingly impor- tant scientific diagnostic tool for weapons science. First demonstrated in 1995, the technique involves using high-energy protons in flash radiography of dynamic experiments, such as implosion tests of mock-ups of nuclear weapons. Protons have advantages over X-rays for certain radiography experiments because protons can penetrate dense materials more efficiently. A key to the success of proton radiography was the realization that magnetic “lenses” can focus the scattered protons to produce exceptionally high-resolution images. The unique feature of proton radiography is its ability to produce high-resolution “movies” of an explo- sively driven experiment of up to 32 frames, as displayed in Figure 3.5. This allows scientists to probe and quantify dynamic phenomena important in accessing the nation’s aging stockpile in the absence of nuclear testing. Today, more than 40 proton radiography experiments are conducted at the LANSCE each year. Other experiments have been carried out at the Alternating Gradient Synchrotron (AGS) accelerator at Brookhaven National Laboratory (BNL).

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S o c i e t a l A pp l i c a t i o n s and Benefits 171 contributing to the quality of life across a wide spectrum of social and economic needs. The applications and manifestations are so entrenched in our daily lives as to be ubiquitous, from simple everyday household items to technologies that pro- vide significant portions of the foundation of medical procedures. Nuclear science has and will continue to play a substantial role in developing solutions for energy, climate, and environmental challenges. Further, the primary tools of modern nuclear science—accelerators and computers—have spawned many applications and economic benefits, some of which are discussed here. Addressing Challenges in Medicine, Industry, and Basic Science with Accelerators Beams of high-energy particles, produced by accelerators, are essential for both fundamental and applied research and for technical and industrial fields. Accelera- tors have become prevalent in our lives, and there are now over 30,000 accelerators worldwide. Of these, the largest number (about 44 percent) are used for radio- therapy, while 41 perecnt are used for ion implantation, 9 percent for industrial research, and about 4 percent for biomedical research. The remaining 1 to 2 per- cent of accelerators are very high-energy accelerators used in nuclear and particle physics to probe the fundamental nature of the matter making up our universe. All accelerators can be described as devices that use electric fields to accelerate charged particles (such as electrons or ions) to high energies, in well-defined beams. Since the discovery of the X-ray in 1895 by Roentgen, many famous nuclear physi- cists have made seminal contributions to new accelerator technologies, including John D. Cockcroft, Ernest Walton, Earnest O. Lawrence, and Robert Van de Graaff. Today accelerator technologies range from the Large Hadron Collider (LHC) capa- ble of producing TeV particles to the lowest energy accelerators used by industry. Accelerators and Medicine Accelerators form the basis for many diagnostic systems, from chest X-ray machines to whole-body X-ray scanners capable of creating a three-dimensional image of the living body. Accelerators such as cyclotrons enable protons and other light nuclei to be used to produce radioactive nuclei that are used in diagnostic medicine. Radioisotopes such as thallium-201 are used to diagnose heart disease. The production of the unstable isotopes of the elements of life, such as oxygen-15, carbon-11, nitrogen-13, and the pseudo-hydrogen fluorine-18, has led to the field of PET. These positron-emitting radionuclides are attached to biologically active molecules. When the tagged molecules are injected, the annihilation radiation can be imaged and the functional capacity of the patient can be determined, as dis- cussed in the PET highlight, located between Chapters 2 and 3. Today PET scanners

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172 Nuclear Physics are combined with computed tomography (CT) scanners so that in one setting, the structural (CT) and functional (PET) capacity of the patient can be determined. CT and PET scanners have revolutionized nuclear medicine. Intense X-rays are now one of the primary modes of treating cancer. Accelera- tors throughout the world generate beams of electrons that are directed to targets that create X-rays, which are then directed at the tumors to destroy them. The modern therapy machine has become extremely sophisticated in that the electron beam can be modulated to increase and decrease the flux to alter the dose of X-rays and thereby spare healthy tissue while maximizing the dose to the tumor. While the standard of care for cancer treatment includes X-ray therapy, there is a growing use of high-energy protons to ablate the tumors. The idea is to deposit as much energy as possible in the tumor cells while sparing the surrounding tissues. In the United States, partnerships between industry and nuclear science labo- ratories have led to new accelerator developments for medical applications. For example, the National Superconducting Cyclotron Laboratory (NSCL) at Michi- gan State University has pioneered the application of superconducting accelera- tor technology in medicine. This work has resulted in the miniaturization of the cyclotron so that it will fit on a gantry and rotate around the subject, simplifying beam delivery and allowing for tighter control of radiation dose delivery. NSCL has also designed and constructed a gantry-mounted, superconducting K100 medical cyclotron, funded by Harper Hospital in Detroit, for neutron therapy. The NSCL’s conceptual design for a superconducting cyclotron for proton therapy has been adopted and further refined by Varian Medical Systems/ACCEL Corporation, with technical advice from NSCL faculty and staff. The success of proton therapy has stimulated interest in using heavier had- rons, such as carbon ions, with the potential of depositing more energy to a small area. Several synchrotrons delivering carbon-12 for therapy have been installed in Europe and Japan. At Brookhaven National Laboratory (BNL), home of the Rela- tivistic Heavy Ion Collider (RHIC), next-generation accelerators for precise, safe cancer radiotherapies are being developed. Accelerators in Industry and for Energy There is a vast enterprise of techniques that use accelerators in a wide range of industries to polymerize plastics, to sterilize food and medical equipment, to weld materials using an electron beam, to implant ions into materials, to etch circuits on electronic devices, to examine the boreholes of oil wells, and to search for dangerous goods. There are approximately 8,500 such devices worldwide. Electron beams dominate the industrial uses, with the curing of wire-cable tub- ing and of ink accounting for more than 60 percent of the market. Other electron beam uses include shrinking films, cross bonding of fibers in tires, and irradiation

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S o c i e t a l A pp l i c a t i o n s and Benefits 173 of food. Here, electron beams replace traditional thermal heating approaches because of the gain in efficiency that comes from the more uniform distribution of energy. A number of major accelerator developments related to nuclear energy are being pursued, including plasma heating for fusion reactors, inertial fusion reac- tors, nuclear waste transmutation, electronuclear breeding, and accelerator-driven subcritical reactors. Basic and Applied Science The breadth of scientific disciplines that make use of accelerators to perform their studies is considerable. Cutting-edge materials research makes use of syn- chrotron radiation having a wide range of wavelengths. Muon beams and neutrons produced from spallation sources probe the properties of materials such as the high-temperature superconductors. Mass spectroscopy is a standard analytical technique for chemists. As discussed at the end of this chapter, high-resolution mass spectrometry is used in archaeology and geology for dating artifacts by determining the ratio of stable to long-lived isotopes. Free-Electron Lasers A free-electron laser (FEL) is a powerful source of coherent electromagnetic radiation that is produced by a relativistic electron beam propagating through a periodic magnetic field (see Figure 3.9). FELs are capable of producing intense radiation over a wide range of the electromagnetic wave spectrum, from micro- wave to hard X-ray, with average beam powers up to tens of kilowatts and peak powers up to tens of gigawatts. FELs are used for research in many fields, including materials science, surface and solid-state physics, chemical, biological and medi- cal sciences, and nuclear physics. While the principle of operation of all FELs is the same, each device is optimized for its main application. FELs that are used in applications that require high average power are typically operated in the infrared (IR) region and are driven by a high-repetition-rate linear accelerator with an opti- cal resonator. Nuclear physics accelerator facilities are leading new developments in FEL technologies. New investigations in condensed matter studies at accelerator labs in the United States and Germany have already identified previously unknown interstellar molecular emission lines, developed new processes for production of boron nitride nanotubes, and produced nonthermal pulsed laser deposition of complex organics on arbitrary substrates. Superconducting radiofrequency technology developed at the Continuous Electron Beam Accelerator Facility (CEBAF) nuclear physics accelerator is now being commercialized for future implementation in weapons

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174 Nuclear Physics Electron source and accelerator Magnetic structure (undulator) Electron Beam Light beam FIGURE 3.9  FELs are a powerful source of coherent electromagnetic radiation that is produced by a relativistic electron beam propagating through a magnetic field. They are used in numerous basic and applied science applications, including 3-09.eps probing materials, biological systems, and nuclei. Shown is a schematic diagram of the basic with vector masks & type is transported through the bitmap layout of an FEL. The electron beam periodically varying magnet field of an undulator magnet. Microbunching inside the electron beam at a spacing equal to that of the light’s wavelength enables electrons to radiate coherently in order to establish lasing. An FEL can be operated with either an optical resonator or in a single-pass configu- ration with a long undulator section. SOURCE: Image courtesy of Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany. Copyright: DESY 2006. systems for the U.S. Navy. And FEL technologies and applications are strongly coupled to nuclear physics research, including the technologies needed for a future electron-ion collider. Information and Computer Technologies Both nuclear physics experiments and theory have been enabled by and, in turn, have spawned, advances in computer science and technology. For experimen- talists, the enormous quantity of data that characterize modern nuclear physics experiments has required that systems be devised to handle and make such data meaningful. RHIC experiments now routinely collect petabyte‐scale data sets each year, at rates of 1 GB per second. Analysis of such data sets drives technology devel- opment for the sustained use of data grids. For example, the computing groups

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S o c i e t a l A pp l i c a t i o n s and Benefits 175 for the STAR collaboration at RHIC have developed a data movement service to achieve sustained and robust automated data transfers of 5 TB a week, with peak data transfer rates reaching 30 MB per second. This allows next-day access to fresh data from the experiments for analysis. Analogous progress has come out of the need for massive and reliable com- putational approaches to address some of the fundamental problems in nuclear theory. Lattice quantum chromodynamics (QCD) calculations of the structure and properties of protons and hot quark-gluon plasmas that begin with fundamental quark and gluon building blocks are among the most demanding numerical com- putations in nuclear physics. Advancing this basic science drives innovation in computer architectures. In a lattice QCD calculation, space and time are rendered as a grid of points, and the quarks and gluons at one point interact only directly with those at other nearby points. This localization of the particles and their interactions makes these numerical computations particularly well suited for massively parallel supercomputers, with communications between processors having a simple pattern that enables the efficient use of a very large number of processors. This characteristic of lattice QCD calculations drove some physicists to design special-purpose supercomputers that attracted attention in the broader computer hardware arena by achieving lower price-to-performance ratios than contemporary commercial supercomputers. A particularly successful group designing special- purpose lattice QCD supercomputers was based at Columbia University, working in partnership with IBM, which manufactured the computer chips. Originally, the group built a machine based on a low-power, simple, digital signal-processing chip (similar to those in cell phones) and a special-purpose serial communication net- work. This partnership laid the foundation for a new machine called the QCDOC (QCD on a chip), displayed in Figure 3.10, in which the whole processing unit, including a newer more powerful microprocessor, the communication network, and memory, was integrated on one chip. Recently, the LHC, which enables particle and heavy-ion nuclear physics research at the energy frontier, has reached unprecedented volumes of data and requirements for data transfer rates and data processing power. This has led to the development of technology that allows extraordinary data transfer rates at large distances. At Super Computing 2011, the International Conference for High Per- formance Computing, Networking, Storage and Analysis, held in Seattle, Washing- ton, in November 2011, a new world record of bidirectional data transfer rate was achieved: 23 GB per second between the University of Victoria Computing Centre located in Victoria, British Columbia, and the Washington State Convention Center in Seattle. Such technology eventually will influence the Internet infrastructure used in our everyday life. Lattice QCD machines, QCDOC in particular, became the paradigm for a new generation of world-leading massively parallel supercomputers that are currently

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176 Nuclear Physics 2 2 1 1 by (fm) by (fm) ) 0 0 –1 –1 –2 –2 –2 –1 0 1 2 –2 –1 0 1 2 bx (fm) bx (fm) FIGURE 3.10  Nuclear science computing needs have led the community to develop new and innova- tive communication networks, data transport and manipulation systems, and computer architectures. 3-10_lower_left FPp.eps 3-10_Lower_right FPn.eps An example is the QCDOC supercomputer at BNL (shown in the upper figure), a joint venture between RIKEN in Japan and the U.S. Department of Energy, in partnership with IBM. Examples of calculations now possible with the most powerful computers are given in the lower figures. Displayed are lattice QCD calculations of the transverse charge distributions of a proton (lower left) and a neutron (lower right), polarized in the x-direction, as a function of the radial distance from the center of the nucleon computed. These transverse charge densities are shown in a reference frame in which the observer is riding along with the photon (the Breit frame). In both cases, the charge distribution has an electric dipole component in the y-direction. This effect is entirely due to the interplay of special relativity and the internal structure of the nucleon. SOURCE: (top) Courtesy of Brookhaven National Laboratory; (bottom) Courtesy of Huey-Wen Lin and Saul D. Cohen, University of Washington.

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S o c i e t a l A pp l i c a t i o n s and Benefits 177 being used in a vast array of applications having impacts in science and on the broader economy. In particular, IBM built the successful commercial Blue Gene line of computers, which engaged several former Columbia students and postdoctoral scholars. In addition to lattice QCD calculations, these supercomputers have been just as successful in simulating exploding stars or nuclear reactors, both of which require enormous computing power. Climate science researchers at BNL are using a Blue Gene named New York Blue to make significant progress in understand- ing today’s climate and to better predict climate evolution. Genomic sequencing, protein folding, materials science, and brain simulations are also prominent on the list of successful Blue Gene applications. Special-purpose supercomputers for lattice QCD have also been designed in Europe (the Array Processor Experiment) and Japan (the CPPACS and PACS-CS projects in Tsukuba). Cosmic Rays, Electronic Devices, and Nuclear Accelerators Cosmic rays are continuously bombarding Earth: more during active solar periods, more at the poles, and less at the equator. When cosmic rays, or radiation from their secondary products, interact with an electronic device, the function of that device can be compromised. The resulting errors in the functionality of an electronic device, such as the one displayed in Figure 3.11, can have very serious consequences for technologies used by such disparate industries as aerospace and autos. A single event upset (SEU) refers to a change in the state of the logic or support circuitry of an electronic device caused by radiation striking a sensitive location or node in the device. SEUs can range from temporary nondestructive soft errors to hard error damage in devices. The detailed physics determining the rate at which SEUs occur is both complicated and device dependent. Circuit manufacturers try to design around the risks posed by cosmic ray interactions by introducing redun- dancy or other protective measures to compensate for the radiation-induced errors. To do so requires detailed knowledge of the expected rates and types of SEUs that can occur. Thus, experimental testing of semiconductor device response to radia- tion requires beams of particles that provide realistic analogs of cosmic rays and their secondary products. The main particles responsible for SEUs are neutrons, protons, and alpha particles, as well as heavy ions. Thus, the beams needed for this large experimental program require a range of nuclear accelerator facilities to test for device vulnerabilities and to characterize the radiation-induced failure modes of the electronic chips. For this, nuclear physics accelerator facilities are a unique resource, and agencies and companies from all over the world purchase beam time at accelerator facilities to test for device vulnerabilities and to characterize the radiation-induced failure modes of the electronic chips. In the United States

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178 Nuclear Physics FIGURE 3.11  Nuclear physics laboratories across the world are working in collaboration with the aerospace and semiconductor industries to assess the impact of cosmic rays on electronic devices such as computer chips. Ongoing research programs are involved in testing the effects of heavy ions and neutrons on microelectronic devices, such as this one being studied at Texas A&M University. SOURCE: Zig Mantell and Texas A&M University. alone, each year national and university nuclear physics laboratories provide almost 10,000 hours of accelerator time for this important service. Helping to Understand Climate Effects One Nucleus at a Time Applications of nuclear techniques are used to advance other scientific disci- plines, including climate science, cosmochemistry, geochronology, paleoclimate, paleo-oceanography, and geomorphology. Since 1949, when Willard Libby first demonstrated carbon dating, the field of trace analyses of long-lived cosmogenic isotopes has steadily grown. Because they are chemically inert, noble gases play a particularly important role as tracers in environmental studies. Owing to their inertness, the geochemical and geophysical behavior of these gases and their distri- bution on Earth is simpler to understand than that of reactive elements. In addition,

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S o c i e t a l A pp l i c a t i o n s and Benefits 179 their inertness facilitates recovery of minute quantities from very large volumes of other material. Precision tools and techniques developed for basic nuclear phys- ics continue to be applied to answer open questions in climatology, geology, and oceanography. Probing Ancient Aquifers in Egypt A challenging problem in earth science is the determination of the residence times and flow velocities of groundwater circulating deeply through Earth’s crust. Krypton-81, which is produced by cosmic-ray-induced spallation in the atmo- sphere, has been identified as an ideal chronometer for determining fluid residence times on the 105-106 year timescale. However, since krypton-81 is such a rare iso- tope it has been extremely difficult to measure its abundance. A new method, atom trap trace analysis (ATTA), was developed at Argonne National Laboratory to analyze krypton-81 in environmental samples. With a half-life of 230,000 years and an atmospheric isotopic abundance of one part per trillion, krypton-81 can provide unique information on terrestrial issues involving million-year timescales. Individual krypton-81 atoms can be selectively captured and detected with a laser-based atom trap. Joining low-level counting and accel- erator mass spectrometry (AMS), two methods previously developed by nuclear physicists, ATTA is the newest method to detect tracers with an isotopic abundance at parts per trillion. Using ATTA, krypton-81 atoms in environmental samples can now be counted and the isotopic abundance of krypton-81 measured. In the first application of ATTA to a groundwater study, a team of geologists and physicists from the United States, Switzerland, and Egypt sampled krypton from the Nubian Aquifer ground- water (displayed in Figure 3.12), which is of unknown age. Following extraction of krypton from thousands of liters of water at six deep wells, the krypton-81/Kr ratios measured by ATTA indicated groundwater ages ranging from 200,000 to 1,000,000 years. These results characterized the age and hydrologic behavior of this huge aquifer, with important implications for climate history and water resource management in the region. The success of this project suggests that widespread application of krypton-81 in earth sciences is now feasible.3 Tracing Ocean Circulation It is becoming more apparent that the oceans are a major regulator for our world’s climate. One of these “motors” is the Atlantic conveyor belt system, whereby 3  Portions of the discussion in this section are adapted from the Argonne National Laboratory, 2003, Physics Division Annual Report, Chapter IV.

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180 Nuclear Physics FIGURE 3.12  Understanding the flow of groundwater that circulates through Earth’s crust is an open question in geology. In a collaboration of nuclear scientists and geoscientists, the precision technique of atom-trap analysis was used to measure the radioactive isotope krypton-81 in deep wells of the Nubian Aquifer in Egypt. The map shows sample locations and their krypton-81 ages (in 100,000 years) in relation to oasis areas (shaded green). Groundwater flow in the Nubian Aquifer is toward the northeast. SOURCE: Adapted from N.C. Sturchio et al., 2004, One million year old groundwater in the Sahara revealed by krypton-81 and chlorine-36, Geophysical Research Letters 31. Copyright 2004 American Geophysical Union. Reproduced/modified by permission of American Geophysical Union. warm water is chilled in the far North Atlantic, sinks to greater depths, and flows down the Atlantic across the Indian Ocean into the Pacific, where it heats up, rises to the surface, and flows back to the North Atlantic, as displayed in Figure 3.13. The whole cycle takes about 1,000 years. It is becoming increasingly clear that the amount of heat transported from the tropics to the polar regions by the oceans

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S o c i e t a l A pp l i c a t i o n s and Benefits 181 FIGURE 3.13  Thermohaline circulation, commonly referred to as the ocean “conveyor belt,” is made up of ocean currents that transport heat from the tropics to the polar regions. AMS of the radioac- tive isotope argon-39 will be used to explore this conveyor belt and its impact on climate. SOURCE: National Oceanic and Atmospheric Administration. is comparable to the amount transported by the atmosphere. Therefore, it is very important to understand this system. With a half-life of 269 years, argon-39 is particularly well suited to study questions related to ocean circulation. However, its extremely low concentration (argon-39/Ar = 8.1 × 10–16), coupled to its long half-life, makes it impossible to measure the argon-39 decay in any sample of reasonable size.4 AMS using the ATLAS heavy ion accelerator at Argonne National Laboratory has been successful in separating argon-39 from its ubiquitous potassium-39 iso- baric background, the latter being 6-7 orders of magnitude more intense. Measure- ment of isotopic ratios as small as argon-39/Ar = 4 × 10–17 have been achieved. This program is now poised to measure argon-39 concentrations in ocean water samples in order to explore the oceanic “conveyor belt.” 4 Portions of this paragraph have been adapted from M. Gaelens, M. Loiselet, G. Ryckewaert, et al., 2004, Oceans circulation and electron cyclotron resonance sources: Measurement of the AR-39 isotopic ratio in seawater, Review of Scientific Instruments 75: 1916.