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Proceedings Paper

Surface breakdown phenomena in alumina rf windows
Author(s): Yoshio Saito
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Paper Abstract

The multipactor and flashover phenomena of alumina rf windows used in a high-power klystron have been investigated. Multipactoring due to the high yield of secondary electron emission takes place during rf operation. A spectrum analysis of luminescence due to multipactoring shows that multipactor electron bombardment causes an F-center of alumina, thus leading to surface melting. From the results of a high-power examination of rf windows with several kinds of alumina ceramics, it was found that an alumina material with a crystallized grain-boundary and without any voids between the boundaries, thus having a low loss-tangent value, is not liable for F-centers, even under multipactoring. Flashovers in a tree- like pattern of alumina luminescence occasionally take place on a TiN-coated surface where multipactoring is suppressed. A sapphire window, whose surface was polished and having pre- existing F-centers, shows a lower flashover threshold. The annealing effect of polished window surfaces was also investigated.

Paper Details

Date Published: 1 May 1994
PDF: 6 pages
Proc. SPIE 2259, XVI International Symposium on Discharges and Electrical Insulation in Vacuum, (1 May 1994); doi: 10.1117/12.174572
Show Author Affiliations
Yoshio Saito, National Lab. for High Energy Physics (Japan)

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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