Pulse processing system for the RADMAP radiation modulation aperture imager

We are currently developing a portable radiation imager for emergency responders. The instrument contains a position-sensitive photomultiplier tube with a thin CsI(Na) scintillator and a tungsten radiation modulation aperture. As part of this project, we have designed a novel pulse processing system to record the amplitude and position of incident events. This system consists of four charge-to-pulse-width converters that transfer time-modulated digital pulses to a field- programmable gate array. The design can process data at count rates exceeding 40,000 events per second and transmit data over an Ethernet link at 1 Gb/sec.