Localization of rf breakdowns in a standing wave cavity

At SLAC, a five-cell, normal-conducting, L -band (1.3 GHz), standing-wave (SW) cavity was built as a prototype positron capture accelerator for the ILC. The structure met the ILC gradient goal but required extensive rf processing. When rf breakdowns occurred, a large variation was observed in the de...

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Bibliographic Details
Published in:Physical review special topics. PRST-AB. Accelerators and beams 2009-04, Vol.12 (4), p.042001, Article 042001
Main Authors: Wang, Faya, Adolphsen, Chris
Format: Article
Language:English
Subjects:
ACCELERATORS
Accelerators,ACCPHY
BREAKDOWN
DECAY
Decay rate
EQUIVALENT CIRCUITS
Internal energy
PARTICLE ACCELERATORS
POSITRONS
PROCESSING
SPECTRA
STANDING WAVES
STANFORD LINEAR ACCELERATOR CENTER
STORED ENERGY
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Summary:At SLAC, a five-cell, normal-conducting, L -band (1.3 GHz), standing-wave (SW) cavity was built as a prototype positron capture accelerator for the ILC. The structure met the ILC gradient goal but required extensive rf processing. When rf breakdowns occurred, a large variation was observed in the decay rate of the stored energy in the cavity after the input power was shut off. It appeared that the breakdowns were isolating sections of the cavity, and that the trapped energy in those sections was then partitioned among its natural modes, producing a distinct beating pattern during the decay. To explore this phenomenon further, an equivalent circuit model of cavity was created that reproduces well its normal operating characteristics. The model was then used to compute the spectra of trapped energy for different numbers of isolated cells. The resulting modal patterns agree well with those of the breakdown data, and thus such a comparison appears to provide a means of identifying the irises on which the breakdowns occurred.
ISSN:1098-4402
1098-4402
2469-9888
DOI:10.1103/PhysRevSTAB.12.042001