RF tuning and fabrication status of the first module for J-PARC ACS

Ao, Hiroyuki; Morishita, Takatoshi  ; Ueno, Akira  ; Hasegawa, Kazuo; Yamazaki, Yoshishige; Ikegami, Masanori*; Paramonov, V.*

J-PARC Linac starts with 180-MeV SDTL temporary, and it is upgraded to 400-MeV with 21 ACS (Annular Coupled Structure) modules and two ACS bunchers and two debunchers. First buncher module is under fabrication, and second buncher and a few accelerating modules are also planed until FY2006. The first ACS module consists of two 5-cell ACS tanks and a 5-cell bridge cavity for the buncher module. Three RF tuners are installed to the bridge cavity for fine RF tuning. An operating frequency should be tuned to 972 MHz within the fine-tuning range before a brazing process in a factory. The tuning procedure has been studied with RF simulation analysis and cold-model measurements for ACS and bridge cells. This paper describes RF tuning results, fabrication status and related development items.