BUNCH LENGTH MEASUREMENT OF 181 MEV BEAM IN J-PARC LINAC

In J-PARC Linac, an energy and intensity upgrade project has started since 2009 using Annular Coupled Structure (ACS) cavities. Because the longitudinal matching before ACS cavities is additionally required, we decided to employ the bunch shape monitors (BSMs) to measure the longitudinal beam profile. After three years from the start of BSM project, three BSMs were fabricated and installed. We tried to measure the longitudinal beam profile exited from SDTL cavities. In this paper, we introduce the outline of BSM, the first beam commissioning and related small problems.