Fibre Optic Sensor For High Energy Radiation

A high bandwidth system has been developed to measure levels of ionising radiation in pulsed systems using a passive sensor head and an optical fibre cable for remote sensing. Optical fibres offer the advantages of very high bandwidth length products (>1GHz km) and freedom from electromagnetic interference, and allow the use of very small electrically passive sensors. These may be used for example to monitor particle accelerators and US work has been reported where similar systems have been investigated for diagnostics during nuclear events (Refs 1 and 2). Using semiconductor scintillator sources, we have achieved risetimes of 1.8ns at a wavelength of 1.311m, enabling the sensor to operate in a region where optical fibres exhibit low material dispersion and low attenuation. A fast optical receiver, with a risetime of 500 ps has been built to monitor the emitted light. Increases of sensor and receiver speeds are anticipated in our future development programmes.