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Microscopical high-speed investigations of vacuum-arc cathode spots

: Siemroth, Peter; Schülke, Thomas; Witke, Thomas


Mesjac, G.A. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
XVI International Symposium on Discharges and Electrical Insulation in Vacuum 1994 : 23 - 30 May 1994, Moscow-St. Petersburg, Russia
Bellingham, WA: SPIE, 1994 (Proceedings of SPIE 2259)
ISBN: 0-8194-1581-2
4 pp.
International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) <16, 1994, Moskau, St. Petersburg>
Conference Paper
Fraunhofer IWS ()

The main parameters and dimensions of cathode spots were under discussion for years. To solve these current questions, a new system was especially designs. The image converting High Speed Framing Camera, which combines a microscopical resolution of 5 micrometers with a nanosecond time resolution and a very high optical sensitivity. This camera was used to study the microscopical behavior of vacuum arc cathode spots in a pulsed high current arc discharge on copper. The direct observation of these spots with high resolution revealed the conclusions that one single cathode spot, as normally observed by optical means consists of a number of simultaneously existing microscopical sub-spots, each of them with a diameter of about 15 micrometers and a mean distance of 30...50 micrometers between them. The mean existence time of these sub-spots on copper was found to be about 3.2 microsecond(s) , where the position of a sub-spot remains unchanged (with an upper limit of about 2...3 micrometers ) during its existence time. An upper limit of the crater surface temperature was estimated by a comparison between the brightness of a cathode spot and of a black body radiation lamp to about 3000 K.