Author: McMahan, C.J.
Paper Title Page
MOPB115 Surface Studies of Plasma Processed Nb Samples 438
 
  • P.V. Tyagi, R. Afanador, B. DeGraff, M. Doleans, B.S. Hannah, M.P. Howell, S.-H. Kim, J.D. Mammosser, C.J. McMahan, J. Saunders, S.E. Stewart
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work is supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
Contaminants present at top surface of superconducting radio frequency (SRF) cavities can act as field emitters and restrict the cavity accelerating gradient. A room temperature in-situ plasma processing technology for SRF cavities aiming to clean hydrocarbons from inner surface of cavities has been recently developed at the Spallation Neutron Source (SNS). Surface studies of the plasma processed Nb samples by Secondary ion mass spectrometry (SIMS) and Scanning Kelvin Probe (SKP) showed that the NeO2 plasma processing is very effective to remove carbonaceous contaminants from top surface and improves the surface work function by 0.5 to 1.0 eV.
*M. Doleans et al., Proc. 2013 SRF, Paris, France.
**P. V. Tyagi, et al., Proc. Linac14, Geneva, Switzerland.
***M. Doleans et al., These proceedings.
 
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THBA01
Plasma Processing to Improve SRF Accelerating Gradient  
 
  • M. Doleans, R. Afanador, J.A. Ball, D.L. Barnhart, W. Blokland, M.T. Crofford, B. DeGraff, B.S. Hannah, M.P. Howell, S.-H. Kim, S.W. Lee, J.D. Mammosser, C.J. McMahan, T.S. Neustadt, J. Saunders, S.E. Stewart, W.H. Strong, P.V. Tyagi, D.M. Vandygriff
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work is supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE
A new In-situ plasma processing technique is being developed at the SNS (Spallation Neutron Source) to improve the performance of the cavities in operation. The technique utilizes a reactive low-density room-temperature plasma to remove top-surface hydrocarbons. This increases the work function of the cavity surface and reduces the overall amount of electron activity; In particular it increases the field-emission onset, which enables to operate a cavity at higher accelerating gradient. Development of the basic plasma processing parameters and effect on the Niobium surface can be found elsewhere *,**. Details on the results for in-situ plasma processing of dressed cavities in the SNS HTA (horizontal test apparatus) will be reported here.
* M. Doleans et al. “Plasma processing R&D for the SNS superconducting linac RF cavities” SRF2013 Proceedings
** P. V. Tyagi, et al. “Surface Studies of Plasma Processed Nb samples” These proceedings
 
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