New scintillation type beam loss monitor to detect spot area beam losses in the J-PARC RCS

Yoshimoto, Masahiro  ; Harada, Hiroyuki  ; Kato, Shinichi; Kinsho, Michikazu  ; Okabe, Kota  

In the J-PARC RCS, a large fraction of our effort has been concentrated on reducing and managing beam losses to achieve 1MW high power proton beam operation. Standard beam loss monitor (BLM), which is installed outside of the magnet in every cell of beam optics and detect the beam loss at wide area in each cell, is insufficient to investigate finer beam loss mechanism in the ring. Thus we developed new scintillation type BLM to detect the beam loss at spot area on the vacuum chamber inside the magnet. The new BLM has separating structure a photomultiplier (PMT) from a plastic scintillator and connecting with optical fibres. Because small plastic scintillator is installed on the vacuum chamber directly, it has capability to have high sensitivity for localized spot area beam loss. On the other hand, the PMT can precisely be operated without being affected by magnetic field by keeping the PMT from the magnet. The new BLM leads the RCS to achieve the stable high power beam operation. In this presentation, we report the detail of the performance of the new BLM.