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Inoue, I.H.

Paper Title Page
MOPLS084 Experimental Comparison at KEK of High Gradient Performance of Different Single Cell Superconducting Cavity Designs 750
 
  • F. Furuta, Y. Higashi, T. Higo, I.H. Inoue, S. Kazakov, Y. Kobayashi, H. Matsumoto, Y. Morozumi, R.S. Orr, T. Saeki, K. Saito, K. Ueno, H. Yamaoka
    KEK, Ibaraki
  • J.S. Sekutowicz
    DESY, Hamburg
 
  We have performed a series of vertical tests of three different designs of single cell Niobium superconducting cavities at 2 degrees Kelvin. These tests aimed at establishing that an accelerating gradient of 45 MV/m could be reached in any of the designs, while using the standard KEK surface preparation. The designs tested were the Cornell re-entrant shape (RE), the DESY/KEK low loss shape (LL), and the KEK ICHIRO series. The cavities underwent surface preparation consisting of centrifugal barrel polishing, light chemical polishing, electropolishing, and finally a high pressure water rinse. All three kinds of cavities were used in a series of vertical tests to investigate details of the surface treatment. When using ultra-pure water for the high pressure rinse, the LL cavity reproducibly exceeded a gradient of 45 MV/m, the RE design reproducibly reached a gradient of between 50 MV/m and 52 MV/m, and three of the six ICHIRO cavities reached a gradient of between 45 MV/m and 49 MV/m.  
MOPLS085 Experience with a Zero Impedance Vacuum Flange at He Super-Leak Temperature for the ILC 753
 
  • H. Matsumoto, F. Furuta, I.H. Inoue, K. Saito, S.N. Sakamoto, K. Ueno
    KEK, Ibaraki
 
  Several tens of thousands of vacuum flanges will be used in the construction of the ILC. So the reliability and large scale reproducibility of these elements are important issue. To arrive at a standardized vacuum flange, a new design of a unisex flange has been developed. This important component has to serve in two roles at He-super-leak temperature; both as an rf seal and as a vacuum seal. We chose the unisex type with a 90-degree sharp edge forming the seal. The design is a modification of the DESY S-band rectangular waveguide flange. The variation in flatness between the flange and gasket along the inside wall is within 50 micrometer. This should present zero impedance for a bunched beam and for rf power. The He-super-leak performance was measured using the "build up method", i.e.the test was carried out for three hours at 2 degrees Kelvin. The measured He leak rate was below 1·10-13 Atm*cc/sec for a test flange after three successive tests. We describe the design concept and the operational experience at various rf frequencies. These span the frequency range corresponding to warm and cold accelerators.