Pulse Pileup Restoration Techniques for High Rate Gamma Spectroscopy with LaBr3(Ce) Scintillation detectors

Gamma spectroscopy is limited by the effects of pulse pileup, which occurs when radiation detection events arrive in rapid succession, causing signal contributions from individual events to overlap. Traditionally, pileup events are discarded by a pileup detection algorithm, as the pileup events distort the pulse height spectrum. This mitigates the degradation in energy resolution but greatly increases the dead time of the detection system at high count rates, which are often encountered in gamma spectra measurements at CANDU maintenance areas and refurbishment workplaces. To address this, we are developing a pulse pileup restoration algorithm that identifies and restores pulse height information from overlapping events for a LaBr3(Ce) scintillator. To optimize the pileup restoration algorithm, a simulation tool was developed to refine and evaluate the restoration algorithm’s performance across various pileup cases. The tool generates synthetic pulse shapes to simulate pulse waveform data at different count rates. The rise and decay times were tuned to match expected LaBr3(Ce) pulse shapes, creating a realistic simulation environment. To complement the simulation studies, pulse waveforms were acquired using a LaBr3(Ce) detector with a commercial high speed digitizer. The setup was configured with and without a preamplifier to provide a diverse dataset for the algorithm development. Analysis of both simulated and experimental data, performed in offline postprocessing, demonstrates that the restoration algorithm effectively restores pulse heights from both pileup and non pileup events. Ongoing work will focus on collecting pulses from high rate sources up to 1 million counts per second, and the implementation of this algorithm on an FPGA forreal time spectroscopy.