Development of a bunch-width monitor for low-intensity muon beam below a few MeV

Sue, Yuki*; Yotsuzuka, Mai*; Futatsukawa, Kenta*; Hasegawa, Kazuo; Iijima, Toru*; Iinuma, Hiromi*; Inami, Kenji*; Ishida, Katsuhiko*; Kawamura, Naritoshi*; Kitamura, Ryo   ; Kondo, Yasuhiro   ; Mibe, Tsutomu*; Miyake, Yasuhiro*; Morishita, Takatoshi  ; Nakazawa, Yuga*; Otani, Masashi*; Saito, Naohito; Shimomura, Koichiro*; Takeuchi, Yusuke*; Ushizawa, Takahiro*; Yamazaki, Takayuki*; Yasuda, Hiromasa*

A destructive monitor to measure the longitudinal bunch width of a low-energy and low-intensity muon beam was developed. This bunch-width monitor (BWM) employed microchannel plates to detect a single muon with high time resolution. In addition, constant-fraction discriminators were adopted to suppress the time-walk effect. The time resolution was measured to be 65 ps in rms using a picosecond-pulsed laser. This resolution satisfied the requirements of the muon linac of the J-PARC E34 experiment. We measured the bunch width of negative-muonium ions accelerated with a radio-frequency quadrupole using the BWM. The bunch width was successfully measured to be 54 11 ns, which is consistent with the simulation.