Author: Kimura, T.
Paper Title Page
THDC1 Slow Extraction Operation at J-PARC Main Ring 219
  • M. Tomizawa, Y. Arakaki, T. Kimura, S. Murasugi, R. Muto, H. Nishiguchi, K. Okamura, Y. Shirakabe, Y. Sugiyama, E. Yanaoka, M. Yoshii
    KEK, Ibaraki, Japan
  • K. Noguchi
    Kyushu University, Fukuoka, Japan
  • F. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
  A high-intensity proton beam accelerated in the J-PARC main ring (MR) is slowly extracted by using the third integer resonance and delivered to the experimental hall. A critical issue in slow extraction (SX) is a beam loss caused during the extraction. A dynamic bump scheme under an achromatic condition provides extremely high extraction efficiency. We have encountered a beam instability in the debunch formation process, which is estimated to be triggered by a longitudinal microstructure of the beam. To suppress this instability, the beam to the MR has been injected into the RF bucket with a phase offset. A newly developed RF manipulation, 2-step voltage debunch, has successfully pushed up the beam power up to 64.6 kW keeping a high extraction efficiency of 99.5%. A drastic beam loss reduction has been demonstrated in the beam test using a diffuser installed upstream of the first electrostatic septum (ESS1). 8 GeV bunched slow extraction tests for the neutrino-less muon to electron conversion search experiment (COMET Phase-I) have been successfully conducted.  
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About • Received ※ 18 October 2021 — Revised ※ 22 October 2021 — Accepted ※ 22 November 2021 — Issue date ※ 03 December 2021
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