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Title: Breakdown phenomena in rf windows

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