JACoW : The Cherenkov Detector for Proton Flux Measurement (CpFM) in the UA9 Experiment

The UA9 experiment at the CERN SPS investigates the possibility to use bent crystals to steer particles in high energy accelerators. In this framework the CpFM have been developed to measure the beam particle flux in different experimental situations. Thin movable fused-silica bars installed in the SPS primary vacuum and intercepting the incoming particles are used to radiate Cherenkov light. The light signal is collected outside the beam pipe through a quartz optical window by radiation hard PMTs. The PMT signal is readout by the WaveCatcher acquisition board, which provides count rate as well as waveform information over a configurable time window. A bundle of optical fibers can be used to transport the light signal far from the beam pipe, allowing to reduce the radiation dose to the PMT. A first version of the CpFM has been successfully commissioned during the data taking runs of the UA9 Experiment in 2015, while a second version has been installed in the TT20 extraction line of the SPS in 2016. In this contribution the design choices will be presented and the final version of the detector will be described in detail.