• A.T. Wu, G. Ciovati, R. Manus, H.L. Phillips, C.E. Reece, R.A. Rimmer, W. Sommer, H. Tian, J.S. Williams
  JLAB, Newport News, Virginia
• F. Eozénou
  CEA, Gif-sur-Yvette
• S. Jin, L. Lin, X.Y. Lu, E. Wang
  PKU/IHIP, Beijing
• J. Mammosser
  ORNL, Oak Ridge, Tennessee

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.

A new surface treatment technique for niobium (Nb) Superconducting Radio Frequency (SRF) cavities called Buffered Electropolishing (BEP) has been developed at JLab. It was found that BEP could produce the smoothest surface finish on Nb samples ever reported in the literature. Experimental results revealed that the Nb removal rate of BEP could reach as high as 4.67 μm/min. This is significantly faster* than that of the conventional electropolishing technique employing an acid mixture of HF and H2SO4. An investigation is underway to determine the optimum values for all relevant BEP parameters so that the high quality of surface finish achieved on samples can be realized within the geometry of an elliptical RF cavity. Toward this end, single cell Nb cavities are being electropolished by BEP at both CEA-Saclay and JLAB. These cavities will be RF tested and the results will be reported through this presentation.

*Xiangyang Lu et al, to be published.

• 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.