Author: Sugiyama, Y.
Paper Title Page
WEC4I1 RF Systems of J-PARC Proton Synchrotrons for High-Intensity Longitudinal Beam Optimization and Handling 305
 
  • F. Tamura, R. Miyakoshi, M. Nomura, H. Okita, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
  • K. Hara, K. Hasegawa, C. Ohmori, K. Seiya, Y. Sugiyama, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  The ap­pli­ca­tion of mag­netic alloy (MA) cores to the ac­cel­er­at­ing rf cav­i­ties in high in­ten­sity pro­ton syn­chro­trons was pi­o­neered for the J-PARC syn­chro­trons, the RCS and MR. The MA loaded cav­i­ties can gen­er­ate high ac­cel­er­at­ing volt­ages. The wide­band fre­quency re­sponse of the MA cav­ity en­ables the fre­quency sweep to fol­low the ve­loc­ity change of pro­tons with­out the tun­ing loop. The dual har­monic op­er­a­tion, where a sin­gle cav­ity is dri­ven by the su­per­po­si­tion of the fun­da­men­tal and sec­ond har­monic rf volt­ages, is in­dis­pens­able for the lon­gi­tu­di­nal bunch shap­ing to al­le­vi­ate the space charge ef­fects in the RCS. These ad­van­tages of the MA cav­ity are also dis­ad­van­tages when look­ing at them from a dif­fer­ent per­spec­tive. Since the wake volt­age con­sists of sev­eral har­mon­ics, which can cause bucket dis­tor­tion or cou­pled-bunch in­sta­bil­i­ties, the beam load­ing com­pen­sa­tion must be mul­ti­har­monic. The op­er­a­tion of tubes in the final stage am­pli­fier is not triv­ial when ac­cel­er­at­ing very high in­ten­sity beams; the out­put cur­rent is high and the anode volt­ageis also mul­ti­har­monic. We sum­ma­rize our ef­fort against these is­sues in the op­er­a­tion of the RCS and MR for more than 10 years.  
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DOI • reference for this paper ※ doi:10.18429/JACoW-HB2023-WEC4I1  
About • Received ※ 29 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 29 October 2023
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