1 May 1994 Surface breakdown phenomena in alumina rf windows
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Proceedings Volume 2259, XVI International Symposium on Discharges and Electrical Insulation in Vacuum; (1994); doi: 10.1117/12.174572
Event: XVI International Symposium on Discharges and Electrical Insulation in Vacuum, 1994, Moscow-St. Petersburg, Russian Federation
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.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yoshio Saito, "Surface breakdown phenomena in alumina rf windows", Proc. SPIE 2259, XVI International Symposium on Discharges and Electrical Insulation in Vacuum, (1 May 1994); doi: 10.1117/12.174572; https://doi.org/10.1117/12.174572
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KEYWORDS
Luminescence

Surface finishing

Sapphire

Ceramics

Tin

Dielectrics

Medium wave

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