A SPACE FIBEROPTIC X-RAY BURST DETECTOR

We describe a novel, lightweight x-ray burst detector that can be embe dded in a satellite structure, thus forming a ''smart skin,'' which ha s minimal impact on the host satellite. The design is based on two typ es of optical fibers coupled to photodiodes. The first is a scintillat ing fiber, which gives a fast signal for timing. The second is a germa nium-doped silica fiber, which darkens for a few milliseconds when irr adiated with a burst of x rays. The resulting slow signal is used to d iscriminate against electrostatic discharges. The coincidence of a fas t signal from the scintillating fiber with a slow signal from the dark ening fiber is the signature of an x-ray burst. The response is linear at low doses and becomes nonlinear at high doses. We have two techniq ues to test the instrument in a space experiment scheduled for 1994. F irst, a small, space-qualified flash x-ray unit can illuminate the fib ers. Second, we can detect space background radiation. The cumulative dose will be monitored by RADFET dosimeters. Future work on embedding the fibers and the electronics as Application Specific Integrated Circ uits (ASICs) in the spacecraft skin could lead to use of these detecto rs on many satellites.