Development of the Optical Transition Radiation Monitor for the High Intensity Proton Beam Profile Measurement

We developed the optical transition radiation (OTR) monitor as a profile monitor for a high intensity (750 kW) slow-extraction beam line at the Japan Proton Accelerator Research Complex (J-PARC). The OTR monitor is considered to be one of good candidates for such a profile monitor, because the OTR light intensity only depends on the reflectivity of an OTR screen. We performed an experiment to test a prototype OTR monitor at the slow-extraction beam line of the KEK 12 GeV-PS. We succeeded to observe a beam profile clearly under the conditions of a low gamma factor of about 13.8, a low beam intensity of 4E11 protons per pulse, and a large beam loss of 1 W/m or more. We also checked a beam response, a background level, and a resistance to radiation of the monitor. We designed and developed two types of the image detecting system such as an optical fiber system and a optical system to enhance the S/N and reduce a radiation damage to the system.