Bohm criterion for the collisional sheath

Journal Article · Mon Apr 01 04:00:00 EST 1996 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.871736· OSTI ID:279772

Valentini, H ^[1]

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1. Department of Physics, University of Greifswald, Greifswald (Germany)

Using a two-fluid model it is shown analytically that in collisional slightly ionized plasmas, i.e., for many typical low pressure discharges, at the sheath edge the drift velocity of the plasma can be smaller than the ambipolar sound speed of the ions. This basic result was known earlier by numerical calculations but it is demonstrated here using simple analytical expressions. Under these conditions the Bohm criterion, in its usual formulation, is a sufficient condition for the existence of a positive boundary sheath, but it is not a necessary condition. {copyright} {ital 1996 American Institute of Physics.}

• OSTI ID: 279772
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 4 Vol. 3; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BOHM CRITERION
COLLISIONAL PLASMA
DRIFT VELOCITY
ION-ATOM COLLISIONS
PLASMA SHEATH
PLASMA-WALL INTERACTIONS
SOUND VELOCITY
WALL EFFECTS