Scintillating fiber detector for the beam loss proton measurements at J-PARC linac

Konstantinova, O.*; Sako, Hiroyuki   ; Maruta, Tomofumi*; Miura, Akihiko 

The highest beam loss has been observed at the ACS (Annular Coupled Structure) section in the J-PARC linac. We have developed a scintillating fiber detector for beam loss proton measurements at J-PARC linac. It consists of 4 upstream fiber planes and 4 downstream fiber planes. The upstream and downstream planes are separated by 1.6 m for time-of-flight measurements. A charged particle which passes through the 8 planes are either a proton or an electron, which can be distinguished by time-of-flight. We measured the absolute proton beam loss rates of 1.8-3.210. The ratio of H/H was 0.7-1.810, which is closed to the estimated value of 2.710 from residual gas pressure. The energy of protons was measured to be 80-120 MeV, which was consistent with the average simulated value of 90 MeV.