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TY - CPAPER AU - Miura, A. AU - Fukuoka, S. AU - Hayashi, N. AU - Liu, Y. AU - Maruta, T. AU - Miyao, T. TI - Bunch Length Analysis of Negative Hydrogen Ion Beam in J-PARC Linac J2 - Proc. of International Beam Instrumentation Conference (IBIC2015), Melbourne, Australia, 13-17 September 2015 AB - We used bunch shape monitors (BSMs) to measure the longitudinal bunch length of a negative hydrogen ion beam in the J-PARC linac. Because we experienced a vacuum degradation to suspend a beam operation during the BSM operations, BSMs were once dismounted for vacuum conditioning. We installed one BSM again in the beam line with additional vacuum equipment. We stared to measure the 191-MeV beam again to tune the buncher amplitude after checking a functioning BSM by comparing its results with those of a simulation. To evaluate the measurement errors with peak beam current increasing, we observed waveforms with various beam currents. Therefore, the RMS bunch length depends on the peak beam current and the bending at the pulse head grows with the peak beam current. Furthermore, to avoid the thermal stress, we compared the data taken at an off-center beam with the ones taken at an on-center beam, because a target wire will be exposed to a higher peak beam current. In this study, we introduced the peak beam current dependence of the bunch length waveforms, and an effect of on-/off-centering of the wire position. Finally, the new buncher tuning method using one BSM is discussed. PB - JACoW CY - Geneva, Switzerland SP - 386 EP - 389 KW - linac KW - operation KW - vacuum KW - emittance KW - electron DA - 2016/01 PY - 2016 SN - 978-3-95450-176-2 DO - 10.18429/JACoW-IBIC2015-TUPB027 UR - http://accelconf.web.cern.ch/AccelConf/IBIC2015/papers/tupb027.pdf ER -