Sheaths: More complicated than you think

Journal Article · Sun May 15 04:00:00 EDT 2005 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.1887189· OSTI ID:20736559

Hershkowitz, Noah ^[1]

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1. University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

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.

• OSTI ID: 20736559
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 12; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COLLISIONAL PLASMA
FLUORESCENCE
LANGMUIR PROBE
NONLINEAR PROBLEMS
PLASMA SHEATH