Development of the bunch shape monitor using the graphene in the medium-energy beam transport of the J-PARC linac

Kitamura, Ryo   ; Futatsukawa, Kenta*; Hayashi, Naoki  ; Hirano, Koichiro  ; Kondo, Yasuhiro   ; Kosaka, Satoshi*; Miyao, Tomoaki*; Nemoto, Yasuo*; Morishita, Takatoshi  ; Oguri, Hidetomo  

In the J-PARC linac, the optimization of the longitude beam matching in the medium-energy beam transport1 is on-going using the bunch shape monitor (BSM) to improve the beam quality. In the measurement with the BSM, the phase distribution of the beam bunch is indirectly measured using the secondary electron beam produced from the negative hydrogen ion beam. However, when the bunch shape is measured at the center of the beam, it has not been measured yet, because of the limitation of the thermal loading of the secondary electron target. Therefore, the graphene was adopted as the BSM target, because it could resist the high thermal loading. and the performance evaluation was conducted. When the target was set at the center of the beam, the detection of the signal from the graphene target was successful. Therefore, this graphene target can be used for the BSM to measure the high-intensity beam with the low energy.