Anomalous Q{sub 0} Results in the CEBAF South Linac

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While in practice, the performance of cavities - Q{sub 0} versus E{sub acc} - in the assembled CEBAF cryomodule corresponds in nearly every respect to the performance as measured in the vertical test area; there are a few cases where this is not true. On six (6) of the twenty (20) cryomodules installed in the south linac, cavity 4 specifically, and one other cavity in cryomodule 7 have an anomalous low Q{sub 0}. Investigation into the source of the low Q{sub 0} on these particular cavities have centered around trapped magnetic fields, slow cooldowns or maldistribution of He flow during ... continued below

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394 Kilobytes pages

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Schneider, William J.; Drury, M. & Preble, Joe October 1, 1993.

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Description

While in practice, the performance of cavities - Q{sub 0} versus E{sub acc} - in the assembled CEBAF cryomodule corresponds in nearly every respect to the performance as measured in the vertical test area; there are a few cases where this is not true. On six (6) of the twenty (20) cryomodules installed in the south linac, cavity 4 specifically, and one other cavity in cryomodule 7 have an anomalous low Q{sub 0}. Investigation into the source of the low Q{sub 0} on these particular cavities have centered around trapped magnetic fields, slow cooldowns or maldistribution of He flow during cooldown leading to hydride precipitation and Q{sub 0} disease. Other possibilities such as low window Q{sub 0}'s or harmonic content of the klystron were also considered. A detailed investigation to understand the phenomena leading to the low Q{sub 0}'s on cryomodule 7 and 8 is discussed. We have found evidence suggesting cooldown dependent Q{sub 0} disease as well as window heating to account for some of the discrepancies but not all. A complete explanation of the problem is still under further investigation.

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394 Kilobytes pages

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  • 6th RF Superconductivity Workshop, Newport News, VA (US), 10/1993

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  • Report No.: CEBAF-PR-93-060
  • Report No.: DOE/ER/40150-2010
  • Grant Number: AC05-84ER40150
  • Office of Scientific & Technical Information Report Number: 791933
  • Archival Resource Key: ark:/67531/metadc742067

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  • October 1, 1993

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  • Oct. 19, 2015, 7:39 p.m.

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  • Feb. 5, 2016, 7:50 p.m.

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Schneider, William J.; Drury, M. & Preble, Joe. Anomalous Q{sub 0} Results in the CEBAF South Linac, article, October 1, 1993; Newport News, Virginia. (digital.library.unt.edu/ark:/67531/metadc742067/: accessed September 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.