Sheaths: More complicated than you think

Hershkowitz, Noah

doi:doi:10.1063/1.1887189

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Hot plasma effects in gas discharge plasma

The subject of this paper is an abbreviated review of a recent study of rf discharges operating at low pressures where hot electron and nonlinear effects are essential. In this operational regime anomalous skin effect and collisionless electron heating may occur. From the direct measurement of electromagnetic fields and rf current density it was possible to infer the rf power absorption and to distinguish collisional and stochastic regimes of electromagnetic field interaction with bounded plasm...

Pulsed-power-driven high energy density physics and inertial confinement fusion research

The Z accelerator [ R. B. Spielman, W. A. Stygar, J. F. Seamen et al., Proceedings of the 11th International Pulsed Power Conference, Baltimore, MD, 1997, edited by G. Cooperstein and I. Vitkovitsky (IEEE, Piscataway, NJ, 1997), Vol. 1, p. 709 ] at Sandia National Laboratories delivers ∼ 20 MA load currents to create high magnetic fields (>1000 T) and high pressures (megabar to gigabar). In a z-pinch configuration, the magnetic pressure (the Lorentz force) supersonically implodes a plasma c...

Sheaths in low temperature collisionless and weakly collisional plasmas are often viewed as simple examples of nonlinear physics. How well do we understand them? Closer examination indicates that they are far from simple. Moreover, many predicted sheath properties have not been experimentally verified and even the appropriate “Bohm velocity” for often encountered two-ion species plasma is unknown. In addition, a variety of sheathlike structures, e.g., double layers, can exist, and many two- and three-dimensional sheath effects have not been considered. Experimental studies of sheaths and presheaths in weakly collisional plasmas are described. A key diagnostic is emissive probes operated in the “limit of zero emission.” Emissive probes provide a sensitive diagnostic of plasma potential with a resolution approaching 0.1 V and a spatial resolution of 0.1 cm. Combined with planar Langmuir probes and laser-induced fluorescence, they have been used to investigate a wide variety of sheath, presheath, and sheathlike structures. Our experiments have provided some answers but have also raised more questions.

Article Outline

INTRODUCTION
THEORETICAL CONSIDERATION
1. Derivation of sheaths
2. Presheath
3. Electron sheaths
SHEATH AND PRESHEATH MEASUREMENTS
1. Emissive probes
2. Ion sheath data
3. Electron sheath data
ACCELERATION AND “SHEATHS” AWAY FROM THE PLASMA BOUNDARY
MULTIPLE ION SPECIES
1. Theory
2. Laboratory experiments
INSTABILITIES
CONCLUSIONS

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KEYWORDS and PACS

Keywords

plasma sheaths, plasma nonlinear processes, Langmuir probes, fluorescence, plasma collision processes

PACS

52.40.Kh

Plasma sheaths
52.70.Ds

Electric and magnetic measurements
52.35.Mw

Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.20.-j

Elementary processes in plasmas

ARTICLE DATA

Digital Object Identifier

http://dx.doi.org/10.1063/1.1887189

PUBLICATION DATA

ISSN

1070-664X (print)

1089-7674 (online)

Publisher

$abstract.society.value is a Member of CrossRef

American Institute of Physics

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