Author: Shirakabe, Y.
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TUVIR15 Long-Term Beam Position and Angle Stabilities for the J-Parc Main Ring Slow Extraction 31
  • M. Tomizawa, Y. Arakaki, T. Kimura, Y. Komatsu, S. Murasugi, R. Muto, K. Okamura, Y. Shirakabe, E. Yanaoka
    KEK, Ibaraki, Japan
  A 30 GeV proton beam accelerated in the J-PARC Main Ring (MR) is slowly extracted by the third integer resonant extraction and delivered to the hadron experimental hall. One of the critical issues in slow extraction of a high intensity proton beam is an inevitable beam loss caused by the extraction process at septum devices. A unique dynamic bump scheme for the slow extraction has been applied to reduce the beam loss. We have achieved 51 kW stable operation at 5.2s cycle in the recent physics run. The extraction efficiency is very high, typically 99.5%. However, the dynamic bump scheme is sensitive to the beam orbit angle at the first electrostatic septum (ESS1). The orbit angle of the dynamic bump must be sometimes readjusted to keep such a high efficiency. In future, diffusers and/or a silicon bend crystal, which are more sensitive to the orbit angle fluctuation, would be introduced to achieve a further high slow extraction efficiency. A long-term stability of the beam position and angle at the ESS1 has been investigated. We observed the fluctuations synchronized with tides and estimated to be due to tunnel expansion.  
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About • paper received ※ 09 June 2020       paper accepted ※ 11 June 2020       issue date ※ 30 July 2020  
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