Author: Kim, S.-H.
Paper Title Page
MOPP114 SNS Linac Upgrade Plans for the Second Target Station 320
MOPOL06   use link to see paper's listing under its alternate paper code  
 
  • J. Galambos, D.E. Anderson, M.P. Howell, S.-H. Kim, M.A. Plum, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  • M.E. Middendorf
    ORNL RAD, Oak Ridge, Tennessee, USA
  
  Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
The Second Target Station (STS) upgrade for the Spallation Neutron Source (SNS) proposes the addition of a short pulse, long wavelength neutron scattering station. In order to provide world-class intensity at the additional station, the SNS linac beam power capability is doubled, to 2.8 MW. This will be accommodated by a 30% increase in the beam energy to 1.3 GeV and a 50% increase in beam current. The beam energy increase will be provided by the addition of 7 additional cyro-modules and supporting RF equipment in space provided during the original SNS construction. The beam current increase will be provided by improved ion source and a reduced chopping fraction, and will require increases in the RF and high voltage modulator systems to accommodate the additional beam loading. Initial plans will be presented. The proposed linac upgrade path will be described. 		 
 
MOPP115 Plasma Processing of Nb Surfaces for SRF Cavities 323
MOPOL10   use link to see paper's listing under its alternate paper code  
 
  • P.V. Tyagi, M. Doleans, S.-H. Kim
    ORNL, Oak Ridge, Tennessee, USA
  • R. Afanador, C.J. McMahan
    ORNL RAD, 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.
Field emission is one of the most critical issues to achieve high performances of niobium (Nb) superconducting radio frequency (SRF) cavities. Field emission is mainly related to contaminants present at top surface of SRF cavities that act as electron emitters at high gradient operation and limit the cavity accelerating gradient. An R&D program at the Spallation Neutron Source (SNS) is in place* aiming to develop an in-situ plasma processing technique to remove some of the residual contaminants from inner surfaces of Nb cavities and improve their performance. The plasma processing R&D has first concentrated on removing hydrocarbon contamination from top surface of SRF cavities. Results from the surface studies on plasma processed Nb samples will be presented in this article and showed the removal of hydrocarbons from Nb surfaces as well as improvement of the surface workfuntion (WF).
*M. Doleans et al. “Plasma processing R&D for the SNS superconducting linac RF cavities” Proceedings of 2013 SRF workshop, Paris, France 		 
slides icon Slides MOPP115 [1.405 MB]  
 
THPP109 History of Cryomodule Repairs at SNS 1108
 
  • M.P. Howell, M. Doleans, D.L. Douglas, S.-H. Kim
    ORNL, Oak Ridge, Tennessee, USA
  • R. Afanador, B. DeGraff, B.S. Hannah, C.J. McMahan, T.S. Neustadt, S.W. Ottaway, J. Saunders, P.V. Tyagi, D.M. Vandygriff
    ORNL RAD, Oak Ridge, Tennessee, USA
  
  The operation of the Superconducting linear accelerator (SCL) has matured and now averages less than one trip per day. The availability of the SCL including radiofrequency systems, high voltage converter modulators, controls, vacuum and other support systems over the last three years is approximately 98%. The SNS has been in operation for ten years including the commissioning period. In support of achieving the stability of operation, multiple cryomodule repairs have been performed. Repairs to cryomodules have included instruments, helium leaks, valve actuators, cavity tuners, insulating vacuum repairs and upgrades, power supplies, higher order mode (HOM) feedthroughs, coupler windows, and coupler cooling components. Performance degradation has been experienced in multiple cavities. This has been corrected by thermal cycling the cryomodules with the affected cavities. Only two cavities have displayed slight permanent degradation that could not be corrected by thermal cycling. Repairs made to the SNS cryomodule will be detailed in this paper.