A compact back-end module for high-rate multielement X-ray spectrometers and gamma-ray imagers

A compact single-ADC back-end module for the derandomization, acquisition a nd memorization of 16 spectra from high-rate multielement radiation detecto rs has been designed and characterized. The input signals, as provided by e xternal peak stretchers, are fed into track- and-hold amplifiers operated i ndependently, which makes it possible to capture randomly-occurring events even in the worst case of time coincidences in different detection elements . The stored signals are then passed along synchronously to a common 12-bit 10-MHz flash ADC, by means of a switch array operated as a multiplexer. Th is provides derandomization of the arrival times of the events. A maximum c ount rate of about 500 kcounts/s/channel is achieved. An homogeneous proces sing rate among the channels is guaranteed by driving the switches with an "intelligent" digital circuitry implemented in two programmable-logic units . Sliding-scale correction is used to reduce by two order of magnitudes the ADC native differential nonlinearity, and so to meet the requirements of t he spectroscopic applications. The measured pulser-peak noise is 1.5 bins r ms over a full scale of similar to 4000 bins.