@article{saxena_hawari_2023, title={High-Resolution Gamma-Ray Spectrometry of Pebble Bed Reactor Fuel Using Adaptive Digital Pulse Processing}, ISSN={["1943-7471"]}, DOI={10.1080/00295450.2022.2148839}, abstractNote={Abstract In this work, an investigation was performed to assess the feasibility of passive gamma-ray spectrometry using adaptive digital pulse processing for online interrogation of pebble bed reactor (PBR) fuel. This work incorporates the physics of the radiation emission phenomenon with advanced pulse processing techniques to develop a high-resolution gamma-spectrometry system capable of handling ultrahigh count rates in various applications of nuclear science and technology. Computational modeling was used to simulate the irradiation of PBR fuel and to design the adaptive digital pulse processing–based gamma-ray spectrometry system. Monte Carlo simulations were performed to study the gamma-ray spectra of the PBR fuel and to perform coupled photon-electron transport analysis to calculate the pulse-height spectrum of PBR fuel. A Monte Carlo computer routine was used to predict the effect of pulse pileup at high-count-rate conditions. This code utilizes the random interval distribution function based on Poisson statistics to simulate the pileup behavior. Combined with pileup logic, a recursive trapezoid filter with adaptive shaping parameters was implemented to simulate the pileup behavior of a digital gamma-ray spectrometry system. The adaptive shaping algorithm selects the rise time of the trapezoid shaping filter based on the separation between the input pulses for each incoming signal. The simulation results using the proposed adaptive digital pulse processing demonstrated that with the improved energy resolution, the burnup information can be more accurately determined on a pebble-by-pebble basis as compared to fixed shaping, and tasks related to in-core fuel management, safeguards, and waste management become feasible to perform efficiently and accurately.}, journal={NUCLEAR TECHNOLOGY}, author={Saxena, Shefali and Hawari, Ayman I.}, year={2023}, month={Feb} }
 @article{saxena_hawari_2017, title={Investigation of FPGA-Based Real-Time Adaptive Digital Pulse Shaping for High-Count-Rate Applications}, volume={64}, ISSN={["1558-1578"]}, DOI={10.1109/tns.2017.2692219}, abstractNote={Digital signal processing techniques have been widely used in radiation spectrometry to provide improved stability and performance with compact physical size over the traditional analog signal processing. In this paper, field-programmable gate array (FPGA)-based adaptive digital pulse shaping techniques are investigated for real-time signal processing. National Instruments (NI) NI 5761 14-bit, 250-MS/s adaptor module is used for digitizing high-purity germanium (HPGe) detector’s preamplifier pulses. Digital pulse processing algorithms are implemented on the NI PXIe-7975R reconfigurable FPGA (Kintex-7) using the LabVIEW FPGA module. Based on the time separation between successive input pulses, the adaptive shaping algorithm selects the optimum shaping parameters (rise time and flattop time of trapezoid-shaping filter) for each incoming signal. A digital Sallen–Key low-pass filter is implemented to enhance signal-to-noise ratio and reduce baseline drifting in trapezoid shaping. A recursive trapezoid-shaping filter algorithm is employed for pole-zero compensation of exponentially decayed (with two-decay constants) preamplifier pulses of an HPGe detector. It allows extraction of pulse height information at the beginning of each pulse, thereby reducing the pulse pileup and increasing throughput. The algorithms for RC–CR2 timing filter, baseline restoration, pile-up rejection, and pulse height determination are digitally implemented for radiation spectroscopy. Traditionally, at high-count-rate conditions, a shorter shaping time is preferred to achieve high throughput, which deteriorates energy resolution. In this paper, experimental results are presented for varying count-rate and pulse shaping conditions. Using adaptive shaping, increased throughput is accepted while preserving the energy resolution observed using the longer shaping times.}, number={7}, journal={IEEE TRANSACTIONS ON NUCLEAR SCIENCE}, author={Saxena, Shefali and Hawari, Ayman I.}, year={2017}, month={Jul}, pages={1733–1738} }