• M. Ikegami
  KEK, Ibaraki
• H. Ao
  JAEA/LINAC, Ibaraki-ken
• T. Morishita, H. Sako, Y. Yamazaki
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

The output energy of J-PARC linac is planned to be upgraded from 190 MeV to 400 MeV by adding an ACS (Annular Coupled Structure linac) section. The ACS is a variety of coupled-cavity structure linac newly devised for former JHP (Japan Hadron Project), and its original beam dynamics design for J-PARC was presented in LINAC02 [M. Ikegami et. al., in Procs. of LINAC02, p. 629]. Extensive R&D studies have been conducted since then to establish the feasibility of ACS, where four ACS modules have been fabricated and successfully high-power tested. In parallel, the beam dynamics design of the ACS has been further optimized to reflect the experience obtained in the R&D studies and reduce the cost for mass production. In this paper, the revised beam dynamics design of the J-PARC ACS is presented with some simulation results with a particle simulation code.

• S. Sato, K. Hasegawa, A. Miura, T. Morishita, H. Sako, A. Ueno, H. Yoshikawa
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• Z. Igarashi, M. Ikegami
  KEK, Ibaraki
• T. Tomisawa
  JAEA/LINAC, Ibaraki-ken

In the J-PARC LINAC, BPMs with 4 strip lines (up, down, right, left) have been used to monitor the beam position by taking log ratio of signals on the opposite (facing) sides of stirp lines. We are studying possibility to monitor beam phase by measuring phase of summed signal of all four stlip lines. In this paper, status of the study is presented.

• A. Miura, K. Hasegawa, T. Morishita, H. Sako, H. Yoshikawa
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• Z. Igarashi, M. Ikegami
  KEK, Ibaraki
• S. Sato, T. Tomisawa, A. Ueno
  JAEA/LINAC, Ibaraki-ken
• H. Takahashi
  JAEA, Ibaraki-ken

Over hundred beam loss monitors (BLM) in the J-PARC LINAC have been used to measure the beam loss observed during the accelerator operation. Dose rates distributed in LINAC area were compared with beam loss records taken by the BLMs. This paper describes the results of the operational data and their comparisons with the dose rates of LINAC area.

• M. Ikegami
  KEK, Ibaraki
• T. Morishita, H. Sako
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• T. Ohkawa
  MHI, Kobe

The output energy of J-PARC linac is planned to be upgraded from 181 MeV to 400 MeV by adding an ACS (Annular Coupled Structure linac) section. The debuncher system for J-PARC linac is also replaced in this energy upgrade. The new debuncher system will consist of two 972-MHz debuncher cavities with the separate-function configuration. In this configuration, the momentum jitter is corrected with the first debuncher, whereas the momentum spread is controlled with the second debuncher. This configuration is advantageous in simplifying the tuning procedure, and it is also beneficial in reducing the nonlinear effects of the debuncher cavities. In this paper, the beam dynamics design of the debuncher system is presented with some simulation results.

• H. Sako, T. Morishita, S. Sato
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• M. Ikegami
  KEK, Ibaraki

Wire Scanner Monitors (WSMs) and Bunch Shape Monitors (BSMs) are going to be installed in the entrance part of ACS (Annular Coupled Structure) section at the energy upgraded J-PARC linac. WSMs are used to measure transverse beam profiles, and BSMs are used to measure longitudinal beam profiles. Both are used to match beams from upstream SDTL (Separated-type Drift Tube Linac) accelerator cavities to ACS. Only a BSM will be installed in the beggining and the best location for the BSM has been chosen through studies of the tuning schemes.