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Yokoyama, K.

Paper Title Page
TUP012 Design and Performance of Optics for Multi-energy Injector Linac 413
 
  • Y. Ohnishi, K. Furukawa, N. Iida, T. Kamitani, M. Kikuchi, Y. Ogawa, K. Satoh, K. Yokoyama
    KEK, Ibaraki
 
 

KEK injector linac provides an injection beam for four storage rings, KEKB high energy electron ring(HER), low energy positron ring(LER), PF-AR electron ring, and PF electron ring. The injection beams for these rings have different energies and intensities. Recently, a requirement of simultaneous injection among these rings arises to make a top-up injection possible. Magnetic fields of DC magnets to confine the beam to the accelerating structures can not be changed between pulse to pulse, although the beam energy can be controlled by fast rf phase shifters of klystrons. This implies that a common magnetic field of the bending magnets and the quadrupole magnets should be utilized to deliver beams having different characteristics. Therefore, we have designed multi-energy optics for the KEKB-HER electron ring(8 GeV, 1 nC/pulse), the PF electron ring(2.5 GeV, 0.1 nC/pulse), and the KEKB-LER positron ring(3.5 GeV, 0.4 nC/pulse). We present a performance of the multi-energy injector linac.

 
TUP010 Pulse-to-Pulse Mode Switching of KEKB Injector Linac 407
 
  • T. Kamitani, K. Furukawa, N. Iida, M. Ikeda, K. Kakihara, M. Kikuchi, T. Mimashi, S. Ohsawa, M. Satoh, A. Shirakawa, T. Sugimura, T. Suwada, K. Yokoyama
    KEK, Ibaraki
 
 

KEKB injector linac supplies electron and positron beams to the KEKB storage rings and the synchrotron radiation facility rings (PF, AR) as well. Injection modes to these four destinations are switched by inserting and extracting positron generation target, changing magnet parameters and acceleration rf phases. To enable pulse-by-pulse switching in three out of the four modes, a pulse bend and pulse steerings are introduced. For DC quads and DC steerings, compatible beam-optical settings for beams of different beam-energy profiles are introduced. We have been performing beam studies to establish the pulse-by-pulse mode switching for daily beam operation. This paper describes a scheme for the mode switching and reports on an achievement of the beam studies.

 
THP053 The Status of Nextef; The X-band Test Facility in KEK 906
 
  • 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 (11.4GHz) test facility in KEK. All of the key devices of this facility are from our old X-band Test Facility(XTF). By combining the power from two klystrons, 100 MW maximum X-band rf power is produced and 75MW is available in the bunker where the high power test of the high gradient accelerator structures will be done. The commissioning of the facility for the structure testing has almost done. The status of the facilityis is reported.

 
THP055 Characteristics of Different Materials on High-Gradient Experiments 912
 
  • K. Yokoyama, S. Fukuda, Y. Higashi, T. Higo, N. Kudoh, S. Matsumoto, Y. Watanabe
    KEK, Ibaraki
 
 

High-gradient experiments have been performed using a narrow waveguide that has a field of approximately 200 MV/m at an rf power of 100 MW. The study investigates the characteristics of different materials at high-gradient rf breakdown. This paper reports the results of high-gradient experiments and observations of the surface of stainless-steel waveguides.

 

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THP061 High Power Test of a Low Group Velocity X-Band Accelerator Structure for CLIC 930
 
  • S. Döbert, A. Grudiev, G. Riddone, M. Taborelli, W. Wuensch, R. Zennaro
    CERN, Geneva
  • C. Adolphsen, V.A. Dolgashev, L. Laurent, J.R. Lewandowski, S.G. Tantawi, F. Wang, J.W. Wang
    SLAC, Menlo Park, California
  • S. Fukuda, Y. Higashi, T. Higo, S. Matsumoto, K. Ueno, K. Yokoyama
    KEK, Ibaraki
 
 

In recent years evidence has been found that the maximum sustainable gradient in an accelerating structure depends on the rf power flow through the structure. The CLIC study group consequently designed a new prototype structure for CLIC with a very low group velocity, input power and average aperture (a/λ = 0.12). The 18 cell structure has a group velocity of 2.4% at the entrance and 1% at the last cell. Several of these structures have been made in collaboration between KEK, SLAC and CERN. A total of five brazed-disk structures and two quadrant structures have been made. The high power results of some of these structures are presented. The first KEK/SLAC built structure reached an unloaded gradient in excess of 100 MV/m at a pulse length of 230 ns with a breakdown rate below 10-6. The high-power testing was done using the NLCTA facility at SLAC.