Statistical analysis of cavity RF faults

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During commissioning of the CEBAF accelerator, it was found that cavities could not be operated reliably at the gradients achieved for short periods during individual cavity commissioning. The principal hypothesis for the cause of about two-thirds the faults seen is charging of the cold ceramic RF window, which is 7.6 cm off the beam axis. Beginning in February, 1995, most RF systems faults were automatically logged. Simple statistical analysis of the accumulated fault data was first applied in July, 1995, with a substantial drop in fault rate recorded. The intent of the analysis was to predict the gradient for each ... continued below

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572 Kilobytes pages

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Benesch, J.F. September 1, 1998.

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During commissioning of the CEBAF accelerator, it was found that cavities could not be operated reliably at the gradients achieved for short periods during individual cavity commissioning. The principal hypothesis for the cause of about two-thirds the faults seen is charging of the cold ceramic RF window, which is 7.6 cm off the beam axis. Beginning in February, 1995, most RF systems faults were automatically logged. Simple statistical analysis of the accumulated fault data was first applied in July, 1995, with a substantial drop in fault rate recorded. The intent of the analysis was to predict the gradient for each cavity at which it would fault once every ten days, leading to a fault rate for the machine of about 33/day (330 cavities). This analysis method was pursued through July, 1996, with substantial benefit. Cavity gradients were increased thereafter to obtain information for an upgrade to 6 GeV, with concomitant fault rate increases. In late 1996 and early 1997, in situ helium discharge processing was employed in 88 cavities to reduce field emissions. The methods used for the analysis of 30,000+ faults recorded between February 1995 and December 1997 are presented. Comparisons of performance before and after helium processing are presented.

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572 Kilobytes pages

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  • Other Information: PBD: 1 Sep 1998

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  • Report No.: DOE/ER/40150-1358
  • Report No.: JLAB-ACC-98-12
  • Grant Number: AC05-84ER40150
  • Office of Scientific & Technical Information Report Number: 754514
  • Archival Resource Key: ark:/67531/metadc711963

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • September 1, 1998

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  • Sept. 12, 2015, 6:31 a.m.

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  • Feb. 5, 2016, 8:37 p.m.

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Benesch, J.F. Statistical analysis of cavity RF faults, article, September 1, 1998; Newport News, Virginia. (digital.library.unt.edu/ark:/67531/metadc711963/: accessed October 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.