Instrumentation Division Seminar

The Peak Detector Derandomizer (PDD) ASIC, is an efficient analog data concentration engine for multichannel radiation detector systems. It accepts shaped pulses with random time of arrival on 32 input channels and produces a single derandomized output per event having accurate peak amplitude, timing, and channel address information. The circuit contains an array of eight peak detectors and associated time-to-amplitude converters (PD/TACs) which are shared among 32 input channels. Fast discriminators self-trigger the acquisition while the arbitration logic routes pulses from any input to any available PD/TAC. The PD/TACs behave like analog and digital memories storing amplitude, timing (as an amplitude), and address data for each pulse and present them to the output upon receipt of a Read Request (RR) signal from the data acquisition system. The multiple PD/TACs effectively sparsify and buffer the data resulting in extremely low dead time. The buffering capability of the PD/TAC array derandomizes in the time domain, allowing the external digitizers to operate at a rate close to the average input rate. Earlier work demonstrated the speed and accuracy of the PDD with laboratory pulser input, as well as the performance of the PDD in acquiring high-resolution spectra in realistic experimental settings. In this talk the new features, implemented in the new version of the ASIC, specifically designed for pile up rejection and for the acquisition of simultaneous events, are discussed. The performance of the PDD in extracting amplitude and timing from pulses generated under high-rate conditions is also presented.