In-situ plasma processing to increase the accelerating gradients of superconducting radio-frequency cavities

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• 作者：M. Doleans ; ^{doleansmm@ornl.gov" class="auth_mail" title="E-mail the corresponding author} ; P.V. Tyagi ; R. Afanador ; C.J. McMahan ; J.A. Ball ; D.L. Barnhart ; W. Blokland ; M.T. Crofford ; B.D. Degraff ; S.W. Gold ; B.S. Hannah ; M.P. Howell ; S-H. Kim ; S-W. Lee ; J. Mammosser ; T.S. Neustadt ; J.W. Saunders ; S. Stewart ; W.H. Strong ; D.J. Vandygriff ; D.M. Vandygriff
• 关键词：Linear accelerator ; SRF technology ; Plasma processing
• 刊名：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• 出版年：2016
• 出版时间：11 March 2016
• 年：2016
• 卷：812
• 期：Complete
• 页码：50-59
• 全文大小：4767 K

文摘

A new in-situ plasma processing technique is being developed at the Spallation Neutron Source (SNS) to improve the performance of the cavities in operation. The technique utilizes a low-density reactive oxygen plasma at room temperature to remove top surface hydrocarbons. The plasma processing technique increases the work function of the cavity surface and reduces the overall amount of vacuum and electron activity during cavity operation; in particular it increases the field emission onset, which enables cavity operation at higher accelerating gradients. Experimental evidence also suggests that the SEY of the Nb surface decreases after plasma processing which helps mitigating multipacting issues. In this article, the main developments and results from the plasma processing R&D are presented and experimental results for in-situ plasma processing of dressed cavities in the SNS horizontal test apparatus are discussed.