Vacuum improvement of bunch shape monitor for J-PARC linac

Miura, Akihiko ; Kawane, Yusuke; Ouchi, Nobuo ; Miyao, Tomoaki*

Bunch shape monitors (BSMs) have been developed and installed in the summer of 2012 at the beginning of new Annular-ring Coupled Structure Linac (ACS) section. Because a problem of the vacuum degradation was found during the BSM operations, BSMs were once dismounted from the beam line and the off-line baking operations with outgas analysis had been performed to reduce the vacuum pressure of BSM surrounding. The impacts of the bias voltage to the target wire and static lens, and the RF power to the deflector were examined in the vacuum test. Finally, we propose the additional vacuum system arrangement for the installation of BSM to the beam line. This paper describes the vacuum test results of BSMs and the additional vacuum system arrangement for the BSM installation.