Plasma Science: From Fundamental Research to Technological Applications (1995)
Chapter: Wave-Particle Interactions and Plasma Heating
phenomena as sunspots, the formation of stars from interstellar gas clouds, the acceleration of cosmic rays, the formation and dynamics of energetic jets and winds from stars and galaxies, or the interaction of supernova remnants with interstellar gas, without the concepts of plasma science. Plasmas are central to many aspects of space science. The space plasma medium extends from the ionosphere surrounding the Earth to the far reaches of the solar system. "Space-weather" prediction in the ionosphere and magnetosphere is important for global communications, and the properties of space plasmas are important in determining the capabilities and longevity of spacecraft. Thus, although it is often not readily apparent, plasma science affects our society in a myriad of ways.
THE DISCIPLINE OF PLASMA SCIENCE
Common Research Themes
The panel has concluded that plasma science is frequently viewed, not as a distinct discipline, but as an interdisciplinary enterprise focused on a large collection of applications. The underlying, common, and critical feature of plasma science as a discipline is that its goal is to understand the behavior of ionized gases, and this requires fundamentally different techniques from those applicable to uncharged gases, fluids, and solids. This coherence of plasma science as a discipline is apparent when one considers some of the challenging intellectual problems, central to plasma science, that span applications in many of the topical areas. The impact of four such problems on the topical areas assessed in this report are summarized in Table S.1.
Wave-Particle Interactions and Plasma Heating
Understanding the interaction of plasma particles with the collective plasma oscillations and waves is a fundamental question with many practical applications. Basic scientific issues involve the trapping of particles in waves, the nonlinear saturation of wave damping, chaotic behavior induced in particle orbits, and particle acceleration mechanisms. Wave heating is an important method of heating fusion plasmas to the required temperatures for fusion. Waves can be used to drive electrical currents in plasmas. One promising scheme for a steady-state tokamak fusion reactor is to use waves to drive electrical currents to confine the plasma, instead of the present method of driving pulsed currents inductively. Wave-particle interactions are central to the operation of free-electron lasers and other coherent radiation sources, to many advanced accelerator concepts, and to methods of creating and heating low-temperature plasmas for plasma processing applications. Wave-particle processes are important in Earth's magnetosphere and ionosphere, and shock waves are the dominant production mechanism for cosmic rays of astrophysical origin.
TABLE S.1 Applications of Basic Plasma Research, Illustrating the Commonality of Scientific Issues Across Topical Areas
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Scientific Issue |
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Topical Area |
Wave-Particle Interactions and Plasma Heating |
Chaos, Turbulence, and Transport |
Sheaths and Boundary Layers |
Magnetic Reconnection and Dynamos |
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Low-temperature plasmas |
Magnetrons Plasma sprays |
Instabilities in plasma processing |
Plasma processing Lighting |
Plasma torches MHD drag reduction |
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Nonneutral plasmas |
ICR mass spectrometry |
Precision clocks Fluid flows Antimatter storage |
Switches Diodes |
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Inertial confinement fusion |
Parametric instabilities Preheating |
Turbulent mixing Rayleigh-Taylor instability |
Plasma-driver interface |
ICF plasma magnetic fields |
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Magnetic confinement fusion |
rf current drive rf plasma heating |
Energy and particle loss |
Divertor operation Plasma-limiter interaction |
Sawteeth and current profile dynamics in tokamaks Reversed-field pinches |
