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Title: Breakdown phenomena in rf windows

Abstract

The multipactor and flashover phenomena of alumina rf windows used in high-power klystrons have been investigated. Multipactoring due to the high yield of secondary electron emission takes place during rf operation. A spectrum analysis of the 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 to F-centers, even under multipactoring. Flashovers in a tree-like pattern of alumina luminescence occasionally take place on a TiN-coated surface. From the results of surface-charging measurements and high-power examinations of annealed alumina disks, the flashover phenomenon is considered to be an avalanche of electrons which have been trapped in mechanically introduced defects. The effectivenesses of multipactor-suppressing coatings and of a field-reduced window structure were also examined. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Authors:
 [1]
  1. KEK-National Laboratory for High Energy Physics, Tsukuba, Ibaraki, 305 (Japan)
Publication Date:
OSTI Identifier:
172185
Report Number(s):
CONF-9410218-
Journal ID: APCPCS; ISSN 0094-243X; TRN: 96:003275
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 337; Journal Issue: 1; Conference: Pulsed radio frequency sources for linear colliders, Long Island, NY (United States), 2-7 Oct 1994; Other Information: PBD: 5 Jul 1995
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 44 INSTRUMENTATION, INCLUDING NUCLEAR AND PARTICLE DETECTORS; 66 PHYSICS; KLYSTRONS; DESIGN; VACUUM SYSTEMS; ALUMINIUM OXIDES; ELECTRON BEAMS; LUMINESCENCE; PHYSICAL RADIATION EFFECTS

Citation Formats

Saito, Y. Breakdown phenomena in rf windows. United States: N. p., 1995. Web. doi:10.1063/1.48423.
Saito, Y. Breakdown phenomena in rf windows. United States. doi:10.1063/1.48423.
Saito, Y. 1995. "Breakdown phenomena in rf windows". United States. doi:10.1063/1.48423.
@article{osti_172185,
title = {Breakdown phenomena in rf windows},
author = {Saito, Y.},
abstractNote = {The multipactor and flashover phenomena of alumina rf windows used in high-power klystrons have been investigated. Multipactoring due to the high yield of secondary electron emission takes place during rf operation. A spectrum analysis of the 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 to F-centers, even under multipactoring. Flashovers in a tree-like pattern of alumina luminescence occasionally take place on a TiN-coated surface. From the results of surface-charging measurements and high-power examinations of annealed alumina disks, the flashover phenomenon is considered to be an avalanche of electrons which have been trapped in mechanically introduced defects. The effectivenesses of multipactor-suppressing coatings and of a field-reduced window structure were also examined. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.},
doi = {10.1063/1.48423},
journal = {AIP Conference Proceedings},
number = 1,
volume = 337,
place = {United States},
year = 1995,
month = 7
}
  • The breakdown of alumina rf windows being used in high-power rf systems of accelerators has been investigated. The puncture and the thermal fracture often taking place in s-band pulsed rf systems and in UHF cw rf systems, respectively, are found to be induced by alumina surface heating due to an electron multipactor bombardment accompanied by a luminescence of alumina. It is ascertained that TiN coatings on the alumina window suppress the multipactor, and that the window duration for breakdown is dependent on the microstruture of the alumina ceramic.
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