Beam loss occurred at DTL cavity in J-PARC linac

Miura, Akihiko ; Miyao, Tomoaki*; Ito, Takashi  ; Hirano, Koichiro  ; Nammo, Kesao*; Maruta, Tomofumi; Tamura, Jun  ; Ikegami, Masanori*; Naito, Fujio*

The beam operation of J-PARC linac was suspended until December 2011 due to the damage by the Tohoku earthquake in March 2011. After resumed the operations, we measured the residual radiation along with the beam line during a short interval. Because the higher residual radiation was detected at the surface of drift tube linac (DTL) cavity by radiation survey, we installed the scintillation beam loss monitors (BLM) at the points where the higher radiation was detected to understand the cause of the radiation. Even the DTL section is low energy part of the linac, fine structure of the beam loss was observed by the scintillation BLM. And we measured the beam loss occurred at the DTL with the parameters of beam orbit and cavity settings. Also, the BLM is employed for the linac tuning. In this paper, the result of the radiation measurement and beam loss signals obtained by the scintillation BLMs are presented.