• S.-H. Kim, D.E. Anderson, I.E. Campisi, F. Casagrande, M.T. Crofford, R.I. Cutler, G.W. Dodson, J. Galambos, T.W. Hardek, S. Henderson, R. Hicks, M.P. Howell, D. Jeon, Y.W. Kang, K.-U. Kasemir, S.W. Lee, J. Mammosser, M.P. McCarthy, Y. Zhang
  ORNL, Oak Ridge, Tennessee

Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy

The Spallation Neutron Source (SNS) is a second generation pulsed-neutron source and designed to provide a 1-GeV, 1.44-MW proton beam to a mercury target for neutron production. Since the initial commissioning of accelerator complex in 2006, the SNS has begun neutron production operation and beam power ramp-up has been in progress toward the design goal. Since the design beam power is almost an order of magnitude higher compared to existing neutron facilities, all subsystems of the SNS were designed and developed for substantial improvements compared to existing accelerators and some subsystems are first of a kind. Many performance and reliability aspects were unknown and unpredictable, for which it takes time to understand the systems as a whole and/or needs additional performance improvements. A power ramp-up plan has been revised based on the operation experiences and understandings of limits and limiting conditions through extensive studies with an emphasis on machine availability. In this paper the operational experiences of SNS Superconducting Linac (SCL), the power ramp-up status and plans will be presented including related subsystem issues.

• T. Tajima, A. Canabal, G.V. Eremeev
  LANL, Los Alamos, New Mexico
• I.E. Campisi
  ORNL, Oak Ridge, Tennessee
• V.A. Dolgashev, S.G. Tantawi
  SLAC, Menlo Park, California
• X. Xi
  Penn State University, University Park, Pennsylvania

Funding: DTRA

We are currently testing the effect of coating Nb with a thin layer of another superconductor such as NbN and MgB2. Gurevich’s theory of multi-layered coating predicts an enhancement of the critical magnetic field, giving us hope to increase the achievable accelerating gradient to above 50 MV/m in elliptical cavities. CW test results of 3 GHz Nb single-cell cavities coated with ~100 nm NbN at LANL and 11.4 GHz <1 μs high-power pulsed test results of 2” Nb disk samples coated with ~100 nm MgB2 will be presented.