Beam dignosis devices of a high power proton beam line facility

We developed beam diagnosis devices, a residual gas ionization beam profile monitor (RGIPM) and an optical transition radiation (OTR) monitor, for a high power proton beam transfer line at the 50-GeV proton synchrotron (PS) of the Japan Proton Accelerator Research Complex (J-PARC). The RGIPM collects electrons produced by beam ionizing a residual gas in the vacuum beam pipe. Since the RGIPM is operated at a vacuum level of 1 Pa, a magnetic field is required to confine electrons around the magnetic field against the diffusion effect due to interactions of drift electrons to residual gas molecules. We, therefore, developed a magnet-built-in type of RGIPM. The OTR monitor observes OTR photons emitted at beam particles crossing a screen with a video camera. We demonstrated that the OTR can be measured even at the KEK 12-GeV proton synchrotron. In order to maintain radiation doses to imaging devices small, the devices are located at a distance of 5 m from the beam line. The OTR photons are collected by a Newtonian reflecting telescope.