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A Simple Model of Diffuse Vacuum arc Plasmas
Author(s) -
Hantzsche E.
Publication year - 1990
Publication title -
contributions to plasma physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0863-1042
DOI - 10.1002/ctpp.2150300504
Subject(s) - plasma , ion , atomic physics , isothermal process , current (fluid) , diffusion , electric field , anode , materials science , electron , ohm's law , electric current , thermal conduction , kinetic energy , mechanics , physics , thermodynamics , classical mechanics , electrode , quantum mechanics
The diffuse expanding plasma of low‐current vacuum arcs is composed of and characterized by an almost thermal electron gas and an ion beam with high kinetic energy. It is described theoretically with a two‐fluid hydrodynamic model. By application of thorough simplifications (such as isothermal conditions, constant composition, one‐dimensional treatment) an analytical solution is found in the form of asymptotic power series of the plasma parameters. This solution is used to analyse the plasma ion acceleration, resulting in the statement that the three forces acting on ions (i.e. the electric field, the ion pressure gradient, the electron‐ion friction) are of comparable importance, contributing to the total ion energy roughly 20%, 35%, and 45%, respectively (in case of Cu vapour arcs). As to the electric field and Ohm's law the solution reveals that the potential is falling towards the anode and that the diffusion current exceeds the opposite conduction current with the consequence of a negative resistance of the arc plasma. Finally, the approximations of the solution, limitations of the validity and possible extensions of the model are shortly discussed.