Study of Pile-Up Effects in Decay Energy Spectroscopy.

Pile-up is an unavoidable complication for cryogenic detectors with relatively large heat capacities and slow rise time, such as systems for decay energy spectroscopy employing large Au absorbers. We have simulated the spectral response of such slow cryogenic detectors using Monte-Carlo algorithms to investigate the effects of pile-up on absolute and relative activity measurements. We focus on the impact of non-distinguishable pile-up that occurs when the rising edges of two waveforms originating from different events overlap in time and are interpreted as a single event. This effect can not be readily identified and corrected in experimental data. We investigated two representative cases of absolute decay counting and plutonium isotopic analysis and find that pile-up can distort the reconstruction of both the absolute and relative activities. This Monte-Carlo methodology quantifies of pile-up effects and provides a systematic methodology for calculating corrective factors. [ABSTRACT FROM AUTHOR]