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Proceedings Paper

Appearance of vacuum-arc cathode spots imaged by emitted light
Author(s): Erhard Hantzsche; B. Juettner
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Paper Abstract

The present paper discusses the appearance of arc cathode spots observed in emission. Photographs yield a size of about 100 micrometers when using line radiation, whereas imaging by absorption techniques or emission pictures with continuum radiation result in values of about 10 micrometers , comparable to the crater traces left at the surface. Besides the size, the slope of the spot profiles is considered. Experimentally, it is found that the light intensity decreases with the distance r from the spot center proportional to r-2. This slope is much less than the expected dependence proportional to r-(beta), (beta) > 4, i.e. the observed spot edge is much less sharp than expected. The behavior of the radiation is theoretically studied by modeling the radial dependence of particle densities and temperature. It is shown that the line radiation stems from a region which is greatly influenced by the plasma expansion in competition with the finite transition probability of excited levels. It is concluded that emission pictures of cathode spot yield considerably higher spot diameters than corresponding to the spot core.

Paper Details

Date Published: 1 May 1994
PDF: 4 pages
Proc. SPIE 2259, XVI International Symposium on Discharges and Electrical Insulation in Vacuum, (1 May 1994); doi: 10.1117/12.174625
Show Author Affiliations
Erhard Hantzsche, Max-Planck-Institut fuer Plasmaphysik (Germany)
B. Juettner, Max-Planck-Institut fuer Plasmaphysik (Germany)

Published in SPIE Proceedings Vol. 2259:
XVI International Symposium on Discharges and Electrical Insulation in Vacuum
Gennady A. Mesyats, Editor(s)

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