Distributed Optical Fiber Radiation Sensing in the Proton Synchrotron Booster at CERN

In this paper, we report on the development and first deployment of a distributed optical fiber radiation sensor (DOFRS) for the online monitoring of radiation levels in the high-energy accelerator facilities of CERN. The DOFRS is composed of two basic parts: a set of suitably chosen radiation sensitive optical fibers (OFs), to be installed in the machine tunnel, and an optical time domain reflectometer (OTDR), to be installed in a radiation-free area. We carried out a calibration of the radiation response of a P-doped multimode OF under $^{60}$Co $\gamma$-rays and in the mixed-field radiation environment of the CHARM facility at CERN. By performing OTDR measurements, we are able to probe the radiation-induced attenuation in the OF along its length and calculate the deposited radiation dose with a spatial resolution of 1 m. In this paper, we describe the main features associated with DOFRS implementation in the proton synchrotron booster (PSB) at CERN. We also report the first results obtained from the monitoring of PSB radiation levels since its recommissioning in April 2017. The performances and advantages of the DOFRS system are discussed.