J-PARC LINAC 50 Hz operation verification study

Kondo, Yasuhiro   ; Chimura, Motoki   ; Cicek, E.*; Fukui, Yuji*; Futatsukawa, Kenta*; Fuwa, Yasuhiro   ; Goto, Rikuto*; Hirano, Koichiro  ; Ishikawa, Masaki*; Ito, Takashi ; Kitamura, Ryo   ; Kosaka, Satoshi*; Miyao, Tomoaki*; Mizobata, Satoshi*; Morishita, Takatoshi  ; Moriya, Katsuhiro  ; Nakano, Hideto; Nammo, Kesao*; Okoshi, Kiyonori ; Okabe, Kota  ; Shibata, Takanori*; Shinto, Katsuhiro   ; Takahashi, Hiroki  ; Tamura, Jun  ; Tasaki, Ryuta*

Various upgrade plans of the J-PARC linac are underway, and repetition-rate doubling project is one of the most important part. Currently, the linac supplies a 400~MeV H ion beam to the 3~GeV synchrotron (RCS) at a repetition rate of 25~Hz. However, to deliver the beam to both RCS and proton-beam irradiation facility under planning, it is necessary to raise the repetition rate from 25~Hz to 50~Hz. Prior to construction of the beamline to the irradiation facility, we conducted a verification of the 50~Hz operation of all the linac apparatus simultaneously within the current operational limits in May 2025. And also, the verification of the 50~Hz operation of the particle counter system, which is one of the most important safety device of the J-PARC accelerator, was conducted. As a result, any significant problems were not found out, and it is now ready for the upcoming 50~Hz-beam acceleration demonstration. This paper describes this details of the demonstration of the 50~Hz operation, without beam acceleration, of the J-PARC linac.