Fiber optic radiation sensors for accelerators

To optimize the beam loss and beam position along large accelerators systems and to determine the exposure of radiation sensitive components we developed several fiber optic dosimetry systems. Two systems are based on the radiation-induced attenuation which is independent of dose rate for the selected fiber. One of these systems is designed to monitor the radiation levels along the accelerator with a commercial Optical Time Domain Reflectometer (OTDR, distributed sensor). The resolution is limited to about 1 m. The second system consists of several local sensor spools the attenuation increase of which is measured with high precision optical power meters. Both systems allow the measurement of radiation doses up to 1000 Gy. The results are available every 5 minutes so that nearly real-time beam optimization is possible. Another system which is based on the induced Cerenkov light in a radiation hard optical fiber can trigger an accelerator shutdown within milli-seconds.