Author: Shimada, M.
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Resonant Coherent Diffraction Radiation System at KEK-cERL  
  • Y. Honda, A. Aryshev, T. Miyajima, T. Obina, R. Ryukou, M. Shimada, R. Takai, N. Yamamoto
    KEK, Ibaraki, Japan
  Coherent radiation from a short bunched electron beam has been expected to be a high power source in THz regime. Especially the feature of the modern energy recovery linac is suitable for a high averaged power source. We propose to test an advanced scheme of resonantly exciting coherent diffraction radiation in an optical cavity. By stimulating the radiation in a multi-bunch beam, highly enhanced radiation power can be extracted. This system can excite all the cavity longitudinal modes at the same time, it can be a broadband source. We are preparing an experimental setup to test the resonant radiation in the cERL at KEK.  
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Proposal of Sharing 6-GeV Class CW Superconducting Linac With ILC and High Brilliance X-ray Light Source  
  • M. Shimada, M. Yamamoto, K. Yokoya
    KEK, Ibaraki, Japan
  • R. Hajima
    QST, Tokai, Japan
  We propose sharing of the 6-GeV class CW superconducting linac with ILC and X-ray light source. ILC utilizes it for the positron source and the two boosters for the 5-GeV damping ring. The conventional positron source, which is based on a collision of the multi-GeV electron with the target, was chosen to lengthen the macro-pulse duration for avoiding the heat loading. In this proposal, the CW linac realizes the long macro-pulse duration beam operation of the positron beam as well as the electron for collision with the target. Simultaneously, the CW linac can used as the 5-GeV booster of the polarized electron beam at the same bunch pattern. Because of the low average current of beams of ILC, the CW linac have enough ability to accelerate/decelerate the high quality electron beam for the high brilliant X-ray light source such as 6-GeV class ERL light source and XFELO. Each electron beam has different injection energy, injects at the different merger and accelerates at the different RF phase. Therefore, the electron energies are different at the end of the CW linac and it makes the simultaneous operation possible.  
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Beam Halo Study at the KEK Compact ERL  
  • O. Tanaka, T. Miyajima, N. Nakamura, M. Shimada
    KEK, Ibaraki, Japan
  • T. Hotei
    Sokendai, Ibaraki, Japan
  • K. Osaki
    Toshiba, Tokyo, Japan
  Funding: Work supported by the Grant-in-Aid for Creative Scientific Research of JSPS (KAKENHI 15K04747).
The beam halo control is of a great importance to attain high intensity beams. Thus, its detailed treatment is indispensable for the stable and safe operation. A systematic beam halo study was established at the KEK Compact ERL (cERL) since machine commissioning in spring 2015 in order to understand the beam halo formation and to have the stable and safe operation. The results of halo simulations have given a reasonable explanation of the low bunch charge (0.2-0.3 pC) beam profiles evaluated during the measurement. Thus, vertical beam halos observed at cERL are supposed to be due to the longitudinal bunch tails transferred into the transverse plane. Tails are mainly produced by the cathode response on the laser excitation. Further, when a beam passing the rf cavity off-center it experiences rf field kicks. The beam tilt could be a complex effect of the steering coils and cavities misalignments. During spring 2017 commissioning the bunch charge was increased up to 40 pC. In present study we are challenging to describe how the space charge effect acts on the beam halo profiles, and how the halo formation mechanisms change in this connection.
slides icon Slides THICCC001 [3.154 MB]  
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