• T. Tajima, W.B. Haynes, F.L. Krawczyk, M.A. Madrid, R.J. Roybal, E.I. Simakov
  LANL, Los Alamos, New Mexico
• W.A. Clemens, K. Macha, R. Manus, R.A. Rimmer, L. Turlington
  JLAB, Newport News, Virginia

An update on the study of 805 MHz elliptical SRF cavities that have been optimized for high gradient will be presented. An optimized cell shape, which is still appropriate for easy high pressure water rinsing, has been designed with the ratios of peak magnetic and electric fields to accelerating gradient being 3.75 mT/(MV/m) and 1.82, respectively. A total of 3 single-cell cavities have been fabricated and tested with various conditions. In addition, a 6-cell cavity design has been completed including multipacting simulations.

• T. Tajima, L. Civale, T. Doi, G.V. Eremeev, N.F. Haberkorn, M. Hawley, A. Matsumoto, R.K. Schulze, A.T. Zocco
  LANL, Los Alamos, New Mexico
• V.A. Dolgashev, J. Guo, D.W. Martin, S.G. Tantawi, C. Yoneda
  SLAC, Menlo Park, California
• B. Moeckly
  STI, Santa Barbara, California

In order to overcome the theoretical limit of ~200 mT peak surface magnetic field for niobium SRF cavities, an idea of coating multi-layer thin film superconductors separated with thin dielectric layers has been suggested. We are testing MgB2, NbN and NbC as candidates for the realization of this idea. The results of surface characterization, Auger depth profile, DC magnetization measurements with SQUID, low- and high-field measurements with a TE013-like mode copper cavity coupled with a 11.4 GHz short-pulse Klystron will be presented.