Longitudinal beam acceptance of J-PARC drift tube linac

Maruta, Tomofumi; Miura, Akihiko ; Sako, Hiroyuki   ; Wei, G.; Ikegami, Masanori*

Since we have no tool to measure the longitudinal beam profile at the J-PARC linac, we have tuned operational parameters for the matching of both longitudinal and transverse directions only from the measurement of the transverse beam profile by wire scanners at matching sections. Therefore it is very useful for us if the beam profile on the longitudinal phase space can be measured. It motivated us to measure the longitudinal acceptance of the DTL. In the measurement, we introduced a "tank level scan" to measure the shrinkage of the acceptance when we reduce the tank level of 1st DTL cavity in addition to the conventional phase scan. In this presentation, we will present the measurement scheme and experimental results.