Beam loss monitor using nuclear reaction with high threshold-energy in the vicinity of J-PARC muon target

Yamaguchi, Yuji   ; Meigo, Shinichiro   ; Oi, Motoki ; Harada, Masahide   ; Haga, Katsuhiro  

At the MLF of J-PARC, 1-MW proton beam with 3 GeV is injected into graphite and mercury targets which are aligned in a cascade scheme. The 2-cm-thick graphite target for muon production is placed upstream of the mercury target and emits radiation from proton injection. Although shielding is performed, the beam loss monitor in the vicinity of the muon target detects the radiation as a background event. To detect beam loss accurately, we have started to develop a new counting tube with bismuth foil to distinguish between beam loss events and background events.