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Higo, T.

Paper Title Page
MOPP029 The First Measurement of Low-loss 9-cell Cavity in a Cryomodule at STF 610
 
  • T. Saeki, M. Akemoto, S. Fukuda, F. Furuta, K. Hara, Y. Higashi, T. Higo, K. Hosoyama, H. Inoue, A. Kabe, H. Katagiri, S. Kazakov, Y. Kojima, H. Matsumoto, T. Matsumoto, S. Michizono, T. Miura, Y. Morozumi, H. Nakai, K. Nakanishi, N. Ohuchi, K. Saito, M. Satoh, T. Takenaka, K. Tsuchiya, H. Yamaoka, Y. Yano
    KEK, Ibaraki
  • T. Kanekiyo
    Hitachi Technologies and Services Co., Ltd., Kandatsu, Tsuchiura
  • J. Y. Zhai
    IHEP Beijing, Beijing
 
  We are constructing Superconducting RF Test Facility (STF) at KEK for the R&D of International Linear Collider (ILC) accelerator. In the beginning of year 2008, we installed one high-gradient Low-Loss (LL) type 9-cell cavity into a cryomodule at STF, where we assembled an input coupler and peripherals with the cavity in a clean room, and the assembled cavity packages were dressed with thermal shields and installed into a cryomodule. At the room-temperature, we performed the processing of capacitive-coupling input-coupler upto the RF power of 250 kW. At the temperature of 4 K, we measured the loaded Q of the cavity and the tuner was tested. At the temperature of 2 K, high-power RF was supplied from a klystron to the cavity and the performance of the cavity packeage was tested. This article presents the results of the first test of the Low-Loss (LL) 9-cell cavity package at 2 K in a cryomodule.  
MOPP083 Status of High Power Tests of Normal Conducting Single-cell Structures 742
 
  • V. A. Dolgashev, S. G. Tantawi
    SLAC, Menlo Park, California
  • Y. Higashi, T. Higo
    KEK, Ibaraki
 
  We report results of ongoing high power tests of single cell traveling wave and standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz*. The goal of this study is to determine the gradient potential of normal-conducting, rf powered particle beam accelerators. The test setup consists of reusable mode launchers and short test structures and powered by SLAC’s XL-4 klystron. The mode launchers and structures were manufactured at SLAC and KEK and tested in SLAC klystron test laboratory.

*V. A. Dolgashev, S. G. Tantawi, et al. “High Power Tests of Normal Conducting Single Cell Structures,” SLAC-PUB-12956, PAC07, Albuquerque, New Mexico, 25-29 June 2007, pp 2430-2432.

 
WEPP084 Fabrication of a Quadrant-type Accelerator Structure for CLIC 2716
 
  • T. Higo, Y. Higashi, H. Kawamata, T. T. Takatomi, K. Ueno, Y. Watanabe, K. Yokoyama
    KEK, Ibaraki
  • A. Grudiev, G. Riddone, M. Taborelli, W. Wuensch, R. Zennaro
    CERN, Geneva
 
  In order to heavily damp the higher order modes of an accelerator structure for CLIC, two kind of damping mechanisms are implemented in one of the designs. Here each cell is equipped with electrically coupled damping channels in addition to the magnetically coupled waveguides. This design requires an assembly of longitudinally cut four quadrants to form a structure and the parts are necessarily made with milling. Since KEK has developed a high-precision machining of X-band accelerator cells with milling and turning at the same time, the experience was extended to the milling of this quadrant. Firstly, the fabrication test of a short quadrant was performed with multiple vendors to taste the present-day engineering level of milling. Following this, a full-size quadrant is also made. In this course, some of the key features are addressed, such as flatness of the reference mating surfaces, alignment grooves, 3D profile shape of the cells, surface roughness and edge treatment. In this paper, these issues are discussed from both fabrication and evaluation point of views.  
WEPP096 Nextef: The 100MW X-band Test Facility in KEK 2740
 
  • S. Matsumoto, M. Akemoto, S. Fukuda, T. Higo, N. Kudoh, H. Matsushita, H. Nakajima, T. Shidara, K. Yokoyama, M. Yoshida
    KEK, Ibaraki
 
  Nextef is a new X-band test facility in KEK. By combining the power from two klystrons, 100MW-class X-band RF power will be available. The facility is for researches on future high gradient linear accelerators. The commissioning operation of the whole facility was started in November 2007. It is planed to conduct high power testing of X-band accelerator structures as well as the fundamental researches such as the RF breakdown experiment with specially designed waveguides.  
WEPP106 High-gradient Experiments with Narrow Waveguides 2758
 
  • K. Yokoyama, S. Fukuda, Y. Higashi, T. Higo, N. K. Kudo, S. Matsumoto
    KEK, Ibaraki
 
  High-gradient RF breakdown studies are presently being conducted at Nextef. To study the characteristics of different materials on high-field RF breakdown, we have performed experiments by using a reduced cross-sectional waveguide that has a field of approximately 200MV/m at an RF power of 100MW. A description of the high-gradient testing of copper and stainless-steel waveguides is reported.