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TY - CONF AU - Tamura, F. AU - Ohmori, C. AU - Sugiyama, Y. AU - Yoshii, M. ED - Liu, Lin ED - Byrd, John M. ED - Neuenschwander, Regis T. ED - Picoreti, Renan ED - Schaa, Volker R. W. TI - Non-Adiabatic Longitudinal Bunch Manipulation at Flattop of the J-PARC MR J2 - Proc. of IPAC2021, Campinas, SP, Brazil, 24-28 May 2021 CY - Campinas, SP, Brazil T2 - International Particle Accelerator Conference T3 - 12 LA - english AB - The J-PARC MR delivers the high-intensity proton beams for the neutrino experiment. Eight bunches of high peak current are extracted by the extraction kickers, therefore the neutrino beam has a similar time structure. The new Intermediate Water Cherenkov Detector (IWCD) will be constructed for the future neutrino experiment and a low peak time structure is desired by the IWCD. Thus, we consider bunch manipulation at flattop of the MR for reducing the peak current. The manipulation requires a longer repetition period to extend the flattop. This reduces the output beam power. The manipulation should be quickly done to minimize the loss of the beam power. Also, the beam gap must be kept for the rise time of the extraction kicker. We propose a non-adiabatic bunch manipulation using the multiharmonic rf voltage. By using the neighbor harmonic of the accelerating harmonic, the first and eighth bunches can be decelerated and accelerated, respectively. After a certain period, the rf phase is flipped to pi for debunching. Thanks to the initial deceleration and acceleration, the beam gap for the kickers is kept. We present the concept and the longitudinal simulation result. PB - JACoW Publishing CP - Geneva, Switzerland SP - 3023 EP - 3026 KW - bunching KW - extraction KW - kicker KW - experiment KW - flattop DA - 2021/08 PY - 2021 SN - 2673-5490 SN - 978-3-95450-214-1 DO - doi:10.18429/JACoW-IPAC2021-WEPAB178 UR - https://jacow.org/ipac2021/papers/wepab178.pdf ER -