Beam loss measurements with scintillation fibers at the J-PARC linac

Sako, Hiroyuki   ; Kikuzawa, Nobuhiro ; Miura, Akihiko ; Maruta, Tomofumi; Adachi, Satoshi; Imai, Kenichi; Sato, Susumu  ; Sugimura, Hitoshi

At Annular Coupled Structure linac (ACS) in J-PARC linac, high residual radiation due to beam loss has been observed. Since the beam loss is approximately proportional to the residual gas pressure, the observed beam loss may be caused by the H's which are generated by the electron stripping by the residual gas. We are going to evaluate beam loss by counting H's emitted outside the beam duct. We have developed hodoscopes with the sensitive area of 64 mm 64 mm, which consists of 16 fibers of 4 mm 4 mm 64 mm. Scintillation photons are measured by the multi-anode photo-multipliers. We report beam loss measurements by the hodoscopes.