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The Langmuir-Debye space charge sheath between plasma and wall changes its properties if electrons are emitted from the surface and enter the plasma. At sufficiently high emission yields the sheath, normally homogeneous and stationary, may become unstable, disintegrating finally into separate unipolar plasma-induced arc spots. Several parameters of the stationary sheath are calculated taking into account the feedback of the electron emission processes. The results show a very strong dependence of the sheath properties on the absolute current densities, and a decisive change of the sheath parameters with the start of thermo-field-emission (TF). Several possibilities resulting in sheath instability and sheath transition to plasma-induced arc spots are indicated and discussed. Finally, possible and significant extensions of the sheath model are proposed, in particular the additional consideration of evaporation from the wall and the explicit temporal development of the sheath transition processes.

Additional information

Authors: HANTZSCHE E, Humboldt-Universität Berlin, Institut für Physik (DE)
Bibliographic Reference: Report: IPP 8/12 DE (1997) 64pp.
Availability: Available from the Max-Planck-Institut für Plasmaphysik, 85748 Garching bei München (DE)
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