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Suggested Citation:"Basic Plasma Experiments." National Research Council. 1995. Plasma Science: From Fundamental Research to Technological Applications. Washington, DC: The National Academies Press. doi: 10.17226/4936.
Page 15
Suggested Citation:"Basic Plasma Experiments." National Research Council. 1995. Plasma Science: From Fundamental Research to Technological Applications. Washington, DC: The National Academies Press. doi: 10.17226/4936.
Page 16

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EXECUTIVE SUMMARY 15 changes in the topology of the field by breaking and reconnecting the magnetic field lines. This process occurs in (magnetohydrodynamic) "sawtooth" oscillations in tokamak plasmas, in sun spots, and in many astrophysical plasmas. Dynamo action is the process by which a flowing plasma converts mechanical energy into magnetic field energy. This process is thought to be the origin of Earth's magnetic field, and it is likely to be one of the mechanisms for producing astrophysical magnetic fields. Very little is understood about magnetic reconnection and dynamo action, yet new techniques are now available to address these problems, by analytic methods, by computer simulation, and by suitably designed laboratory experiments. These and other forefront problems in plasma science are described in Part III, and the relationship of this research to specific topical areas and applications is discussed in Part II. RESEARCH AND EDUCATION IN PLASMA SCIENCE The findings and conclusions regarding the three broad areas of plasma science assessed in Part III are discussed in this section. Basic Plasma Experiments Of any of the topics in the panel's study, basic plasma experiments constitute the area of greatest concern. Progress in the physical sciences has relied historically on the close interplay between theory and experiment. Perhaps nowhere is this more true than in many-body physics, which naturally includes plasma physics. Physical phenomena can be identified, isolated, and studied most efficiently, quickly, and economically in experiments specifically tailored for this purpose. There are many advantages of basic experiments, compared to experiments done in settings determined by other considerations such as particular applications. These advantages include the flexibility to choose the setting to isolate a particular physical phenomenon, the ability to explore the broadest range of plasma parameters, and the ability to make experimental changes quickly, guided by the internal logic of the underlying science and by new results as they unfold. Despite the importance of basic plasma experiments to plasma science, there have been clear warning signs for more than a decade of a deficiency in this area. This was expressed clearly in the Brinkman report, Physics Through the 1990s, written almost a decade ago.2 The finding of the panel is that this situation has worsened since the Brinkman report was issued. There are several causes of this 2 National Research Council, Plasmas and Fluids, in the series PhysicsThrough the 1990s, National Academy Press, Washington, D.C., 1986.

EXECUTIVE SUMMARY 16 problem, which include the narrowing focus of the large applied programs such as fusion and space applications. The future health of plasma science as a discipline hinges on the revitalization of basic plasma science, particularly the revitalization of small-scale basic plasma experiments—the area of most rapid decline in the last 20 years. Plasma science is suffering from application without replenishment: With major emphasis on applying what is known and without maintaining the basic scientific effort, the "seed corn" is quickly disappearing. Although support for basic plasma science has declined over the past two decades, there has been important progress, which provides an idea of the potential contributions that basic research can make. Important achievements include a deeper understanding of the interaction of plasma waves with plasma particles. Many important nonlinear plasma processes have been isolated and understood, including some aspects of double layers, which, as discussed above, are the nonlinear interfaces between regions of plasma with distinctly different plasma properties; the effects of ponderomotive forces in causing the reorganization of plasmas; the filamentation of electromagnetic radiation in plasmas; and some aspects of the reconnection of magnetic field lines and magnetic reconfiguration of plasmas. Recently, the effects of chaotic particle orbits on plasma behavior have begun to be addressed by laboratory experiments. Each of these phenomena has many potential applications, so that progress on one topic is likely to have an impact on several different areas of plasma science. Progress has also been made in developing new techniques for experimental plasma studies, including some developed specifically for plasma applications and others that have resulted from advances in technologies such as electronics and computing. As the development of applications has progressed, the decline of basic plasma experiments over the past 20 years has led to a significant backlog of important opportunities for basic experiments. We lack a basic understanding of many aspects of Alfvén waves, relevant to both space and fusion plasmas. We lack a basic understanding of magnetic reconfiguration processes and a host of other important nonlinear phenomena, including the wave-plasma interactions, plasma sheaths and boundary layers in magnetized plasmas, and dynamo action, discussed above. Progress in understanding each of these phenomena has been hindered by the lack of basic experiments designed to address key issues. To reinvigorate experimental plasma science in the most efficient and cost- effective way, the panel concludes that emphasis should be placed on support for university-scale research programs. This conclusion is based on two findings: Many if not most of the important outstanding problems in basic plasma science can be addressed by this mode of experimentation. In addition, where small and individual principal-investigator-led programs are possible, the degree of flexibility, diversity, and creativity associated with this mode of research optimizes the limited resources that can be expected to be available for basic plasma research in the foreseeable future. The panel estimates the size of the investment that will be required in the

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Plasma science is the study of ionized states of matter. This book discusses the field's potential contributions to society and recommends actions that would optimize those contributions. It includes an assessment of the field's scientific and technological status as well as a discussion of broad themes such as fundamental plasma experiments, theoretical and computational plasma research, and plasma science education.

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