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- Y. Sato, K. Hara, Y. Hashimoto, Y. Hori, S. Igarashi, K. Ishii, N. Kamikubota, T. Koseki, Y. Kurimoto, K. Niki, K. Ohmi, C. Ohmori, M. Okada, M. Shimamoto, M.J. Shirakata, T. Sugimoto, J. Takano, M. Tejima, T. Toyama, M. Uota, S. Yamada, N. Yamamoto, M. Yoshii
KEK, Tokai, Ibaraki, Japan
- S. Hatakeyama, H. Hotchi, F. Tamura
JAEA/J-PARC, Tokai-mura, Japan
- S. Nakamura, K. Satou
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
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J-PARC main ring (MR) provides high power proton beams of 200 kW to the neutrino experiment. Beam losses were well managed within capacity of collimation system. Since this beam power was achieved by shortening the repetition rate, following tunings had been applied in order to reduce the beam losses, such as improvement of tune flatness, chromaticity correction, upgrades of injection kickers, dynamic bunch-by-bunch feed-back to suppress transverse oscillation, beam loading compensation using feed-forward technique, and balancing the collimators of MR and the injection beam transport line. The dynamic bunch-by-bunch feed-back was effective to reduce the beam losses to one-tenth during injection and beginning of acceleration. With the beam loading compensation, impedance seen by the beam was significantly reduced, longitudinal oscillations were damped, and the beam power was increased over 5% without increasing the beam losses. Monitors were upgraded to find time structure and location of the beam losses, even in first several turns after each injection. In this presentation these commissioning procedures and beam dynamics simulations are shown, and our upgrade plan is discussed.
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