Microscopic high speed investigations of vacuum arc cathode spots

The main parameters and dimensions of cathode spots have been under discussion for years. To solve these current questions, a new system was specially designed. The image converting high speed framing camera (HSFC) combines a micrometer lateral resolution with a nanosecond time resolution and a very...

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Bibliographic Details
Published in:IEEE transactions on plasma science 1995-12, Vol.23 (6), p.919-925
Main Authors: Siemroth, P., Schulke, T., Witke, T.
Format: Article
Language:English
Subjects:
Arc discharges
Cameras
Cathodes
Copper
Discharge in vacuum
Electric discharges
Exact sciences and technology
Image converters
Image resolution
Optical microscopy
Optical pulses
Optical sensors
Physics
Physics of gases, plasmas and electric discharges
Physics of plasmas and electric discharges
Vacuum arcs
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Summary:The main parameters and dimensions of cathode spots have been under discussion for years. To solve these current questions, a new system was specially designed. The image converting high speed framing camera (HSFC) combines a micrometer lateral resolution with a nanosecond time resolution and a very high optical sensitivity. This camera was used to study the microscopic 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 that one single cathode spot, as normally observed by optical means, consists of a number of simultaneously existing microscopic subspots, each with a diameter of about 10 /spl mu/m and a mean distance of 30-50 /spl mu/m between them. The mean existence time of these subspots on copper was found to be about 3 /spl mu/s, where the position of a subspot remains unchanged (with an upper limit of about 5 /spl mu/m) during its existence time. The lower limit of the current density in the cathode spots was estimated to be on the order of 10/sup 10/-10/sup 11/ A/m/sup 2/. An upper limit of the crater surface temperature was estimated by a comparison between the brightnesses of a cathode spot and of a black body radiation lamp to about 3000 K.
ISSN:0093-3813
1939-9375
DOI:10.1109/27.476476