Author: Michizono, S.
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MOIACC002 Development of SRF Gun Applying New Cathode Idea Using a Transparent Superconducting Layer 1
  • T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, K. Umemori, S. Yamaguchi, M. Yamamoto
    KEK, Ibaraki, Japan
  • R. Matsuda
    Mitsubishi Heavy Industries Ltd. (MHI), Takasago, Japan
  • T. Yanagisawa
    MHI-MS, Kobe, Japan
  KEK has been developing a superconducting RF gun for CW ERL since 2013. The SRF gun is a combination of a 1.3 GHz, 1.5-cell superconducting RF cavity and a backside excitation type photocathode. The photocathode consists of transparent substrate MgAl2O4, transparent superconductor LiTi2O4 and bi-alkali photocathode K2CsSb. The reason for using transparent superconductor is to reflect RF by using the feature of penetration depth of superconductor, which is defined from London equation. It protects optical components from RF damage. The critical DC magnetic field of the cathode, quantum efficiency and initial emittance were measured. These show the cathode can be used for the SRF gun. The gun cavity was designed to satisfy the photocathode operation. Eight vertical tests of the gun cavity have been performed. The surface peak electric field reaches to 75 MV/m with the dummy cathode rod which was made of bulk niobium.  
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Resonance Control at the Compact ERL in KEK  
  • T. Miura, D.A. Arakawa, M. Egi, K. Enami, T. Furuya, E. Kako, H. Katagiri, T. Konomi, T. Matsumoto, S. Michizono, F. Qiu, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • N. Liu
    Sokendai, Ibaraki, Japan
  • M. Sawamura
    QST, Tokai, Japan
  The compact energy recovery linac (cERL) in KEK is a test facility for the future 3-GeV ERL light source. The 1.3 GHz superconducting cavities are used in the injector linac cryomodule and the main linac cryomodule. The slide-jack tuner with stepper motor is used for coarse tuning of the resonant frequency, and piezo tuner is used for fine tuning. The digital tuner feedback system based on micro-TCA standard has been employed. The frequency band of the tuner feedback has been set lower than the mechanical resonance frequency. The rf field fluctuation caused by the Michrophonics is compensated by the rf feedback. In the injector linac, one rf source drives two cavities with vector-sum control. The vector-sum calibration error affected the beam energy jitter, but that has been improved after adopting the high gain parameter in resonant frequency feedback in order to keep the field balance of the cavities.  
slides icon Slides MOICCC003 [9.983 MB]  
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