Status of beam loss evaluation at J-PARC linac

Miura, Akihiko ; Sako, Hiroyuki   ; Yamamoto, Kazami   ; Kikuzawa, Nobuhiro ; Maruta, Tomofumi; Sato, Susumu  ; Imai, Kenichi; Adachi, Satoshi; Sugimura, Hitoshi; Igarashi, Zenei*; Miyao, Tomoaki*; Ikegami, Masanori*

Ar-CO gas proportional counters are employed for the measurement of beam loss in the current linac operation, but they are also sensitive to background noise of X-ray emitted from RF cavities. In SDTL section, protons, secondary hadrons and rays would be mainly generated as a beam loss, but it is not easy to estimate real beam loss using the proportional counter. The plastic scintillation counters with less X-ray sensitivity and He proportional counters with high thermal neutron sensitivity will be also employed to measure the beam loss. This paper reports the signals obtained during the beam operation using the Ar-CO gas proportional counter and the plastic scintillation counter. Finally, a measurement of emission position and angle distributions of protons due to negative hydrogen ion (H) beam loss is being planed. This plan is introduced and this result would lead to clarify the source of beam loss.