Author: Miyahara, F.
Paper Title Page
MOPRO001 Upgrade Status of Injector LINAC for SuperKEKB 59
 
  • T. Miura, M. Akemoto, D.A. Arakawa, Y. Arakida, A. Enomoto, S. Fukuda, Y. Funakoshi, K. Furukawa, T. Higo, H. Honma, R. Ichimiya, N. Iida, M. Ikeda, E. Kadokura, H. Kaji, K. Kakihara, T. Kamitani, H. Katagiri, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, F. Miyahara, H. Nakajima, K. Nakao, T. Natsui, Y. Ogawa, Y. Ohnishi, S. Ohsawa, F. Qiu, M. Satoh, T. Shidara, A. Shirakawa, H. Sugimoto, T. Suwada, T. Takenaka, M. Tanaka, Y. Yano, K. Yokoyama, M. Yoshida, L. Zang, X. Zhou
    KEK, Ibaraki, Japan
  • D. Satoh
    TIT, Tokyo, Japan
 
  The SuperKEKB collider is under construction to achieve 40-times higher luminosity than that of previous KEKB collider. The injector LINAC should provide high-intensity and low-emittance beams of 7-GeV electron and 4-GeV positron for SuperKEKB based on a nano-beam scheme. A photocathode RF-gun for low emittance electron beam has been already installed and the commissioning has started. The construction of positron capture section using a flux-concentrator and the dumping ring for low emittance positron beam is in progress. The simultaneous top-up injections to four storage-rings including photon factories is also required. In the upstream of dumping ring, the compatible optics between positron and electron has been designed. In the downstream of dumping ring, RF phase, focusing, and steering magnets will be switched by pulse to pulse against each beam-mode for optimising beam-transportation. This paper describes recent upgrade status toward the SuperKEKB.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO001  
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MOPRI002 Design, Manufacture and Operation of the Beam Spoiler for Positron Target Protection 573
 
  • L. Zang, K. Kakihara, T. Kamitani, K. Mikawa, F. Miyahara, T. Suwada
    KEK, Ibaraki, Japan
 
  In order to produce positrons, intensive pulsed electron beam is used to strike on a tungsten target. The energy deposition is distributed non-uniformly over the target, leading to a mechanical stress. As a result of large thermal gradient, the target could be potentially damaged. To avoid the target destruction, the peak energy deposition density (PEDD) in the target should be well below the critical limit (35J/g) based on the SLAC operational experience. With an expected primary electron spot size on the target of the SuperKEKB positron source, the PEDD will exceeds the limit. We will introduce a beam spoiler to enlarge the spot size by multiple scattering in thin beam screen and aluminum plate. It reduces the PEDD down to half of the limit. This paper describes the design of the spoiler and the beam screen system used in the positron beam commissioning of the SuperKEKB positron source started in 2014.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI002  
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MOPRI003 Positron Yield Optimization by Adjusting the Components Offset and Orientation 576
 
  • L. Zang, M. Akemoto, S. Fukuda, K. Furukawa, T. Higo, N. Iida, K. Kakihara, T. Kamitani, T. Miura, F. Miyahara, Y. Ogawa, H. Someya, T. Takatomi, K. Yokoyama
    KEK, Ibaraki, Japan
  • S. Ushimoto
    Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
 
  In order to keep high luminosity beam collision condition at SuperKEKB, low emittance electron/positron injection and flexible pulse-to-pulse switching of these beam modes are essential requirements. While a primary electron beam strikes on a target to generate positrons, an injection electron beam passes through a small hole besides the target. Since the injection electron orbit should be on axis to avoid emittance growth, the target and the flux concentrator for positron focusing have a few millimeters offset from the axis. This offset positron generation gives significant degradation in the positron yield. In this paper, we will discuss positron yield improvement by proper orientation of the cut-in slit of the flux concentrator which yields un-symmetric field distribution and primary electron incident point. With particle tracking simulation taking three dimensional field distribution into account, an ideal positron trajectory giving optimum yield was found.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI003  
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MOPRI004 SuperKEKB Positron Source Construction Status 579
 
  • T. Kamitani, M. Akemoto, D.A. Arakawa, Y. Arakida, A. Enomoto, S. Fukuda, Y. Funakoshi, K. Furukawa, T. Higo, H. Honma, N. Iida, M. Ikeda, E. Kadokura, H. Kaji, K. Kakihara, H. Katagiri, M. Kikuchi, H. Koiso, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Mimashi, T. Miura, F. Miyahara, T. Mori, A. Morita, H. Nakajima, K. Nakao, T. Natsui, Y. Ogawa, Y. Ohnishi, S. Ohsawa, M. Sato, T. Shidara, A. Shirakawa, M. Suetake, H. Sugimoto, T. Suwada, T. Takatomi, T. Takenaka, M. Tanaka, M. Tawada, Y. Yano, K. Yokoyama, M. Yoshida, L. Zang, X. Zhou
    KEK, Ibaraki, Japan
  • D. Satoh
    TIT, Tokyo, Japan
 
  The KEKB positron source is under the upgrade for SuperKEKB. The previous positron production target and capture section have been removed and the new system is constructed at a location forty meters upstream to have sufficient energy margin for beam injection to the newly introduced damping ring. A flux concentrator is introduced in the new capture section to make an adiabatic matching system. Large aperture (30mm in diameter) S-band accelerating structures are introduced in the capture section and in the subsequent accelerator module to enlarge the transverse phase space acceptance. The beam focusing system of quadrupoles is also upgraded for a comparable beam acceptance to that of the capture section. This paper reports on the status of the SuperKEKB positron source construction and the preliminary positron beam commissioning.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI004  
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TUPRI109 Construction and Commissioning of Event Timing System at SuperKEKB 1829
 
  • H. Kaji, K. Furukawa, M. Iwasaki, E. Kikutani, T. Kobayashi, F. Miyahara, T.T. Nakamura, M. Satoh, M. Suetake, M. Tobiyama
    KEK, Ibaraki, Japan
  • T. Kudo, S. Kusano
    Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
  • T. Okazaki
    EJIT, Hitachi, Ibaraki, Japan
 
  The Event Timing System of Injector Linac at KEK is upgraded to satisfy the new requirements for the SuperKEKB project. After finishing the design and feasibility studies*, we have constructed the new system at Main Trigger Station of Linac. The new functions are developed in this system to perform the injection control of positrons with the newly constructed damping ring. Besides, we integrate the capability to adjust the trigger timing just 20 ms before injection so that the injection RF-bucket of the ring can be decided at the last minute. Now, both the new system and the current working system are operational at Main Trigger Station. This is important for the smooth taking over of Event Timing System. Even during the construction period, Linac must be operated to provide beams into the two light source rings. In this situation, we can carry out enough tests with the actual condition. These tests do not disturb the regular operation and brush up the Event Timing System to enable the quick startup of the SuperKEKB operation. We report about the detailed configuration of the new system and its commissioning performed in the 2014 spring run period.
* H. Kaji et al., "Upgrade of Event Timing System at SuperKEKB",
proceedings of ICALEPCS13, San Francisco, USA, October 6-11, 2013.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI109  
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