Optical fiber beam loss monitor

We have been developed an arc sensor with high sensitivity since 2007. When the arc sensor was installed into the cavity coupler located in the beam tunnel, it is found that an arc sensor reacted to beam loss sensitively. This is because Cherenkov light occurs in the optical fiber by the charged particle. This means that the state of the beam loss can be detected by observing the Cherenkov light. Large-diameter optical fibers were set into the acceleration structures and vacuum ducts. We observed light from an optical fiber by the photo-multiplier tube (PMT). When we observed light from the upstream, we can identify the point of the beam loss in position resolution of 8.3 nsec/m. We observed beam loss at various points of the Linac. (author)