@article{mishra_mattingly_2022, title={Convolution-based frequency domain multiplexing of SiPM readouts using the DRS4 digitizer}, volume={1025}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2021.166116}, abstractNote={We present 4:1 multiplexing of organic scintillators, each coupled to a silicon photomultiplier (SiPM), to reduce the need for a large number of digitizer input channels to readout highly pixelated radiation detection systems. Frequency domain multiplexing (FDM) encodes a detector pulse by assigning it a unique frequency via convolution before combining the encoded signal into a single channel. The combined signal is then read through a digitizer input channel. We have designed an FDM system to multiplex four SiPMs using DRS4 digitizer evaluation board from Paul Scherrer Institute (PSI). We demonstrate 4:1 multiplexing of the SiPM fast output signals and pulse recovery from the digitized multiplexed signal using deconvolution. The noise in the recovered pulse introduces a bias and uncertainty in the estimate of energy and timing that changes with pulse height. The relative uncertainty in the estimated energy from the recovered pulse decreases with pulse height with a maximum uncertainty of 3.1% for the low energy pulses (corresponding to 100 keV); the uncertainty in the estimated time pick-off also decreases with pulse height with a maximum uncertainty of 110 ps for the low energy pulses.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Mishra, M. and Mattingly, J.}, year={2022}, month={Feb} }
 @article{mishra_mattingly_2021, title={Recovery of coincident frequency domain multiplexed detector pulses using sequential deconvolution}, volume={16}, ISSN={["1748-0221"]}, DOI={10.1088/1748-0221/16/03/P03011}, abstractNote={Multiplexing of radiation detector signals into a single channel significantly reduces the need for a large number of digitizer channels, which reduces the cost and the power consumption of a data acquisition system. We previously demonstrated frequency domain multiplexing by convolution using a prototype system that multiplexed two EJ-309 organic scintillators signals into a single channel. Each detector pulse was converted to a damped sinusoid which was then combined into a single channel. The combined signal was digitized and the original detector signal was recovered from the damped sinusoid by deconvolution. In this paper, we demonstrate the recovery of multiple detector signals that arrive during the same digitized record via a new sequential deconvolution method. When two detectors produce signals in the same digitized record and their pulses do not overlap in time, we found that the charge, arrival time, and particle type can be estimated fairly precisely for the first pulse, but the second pulse exhibits substantial degradation in the precision of the estimated charge and arrival time. When the pulses overlap in time, we demonstrate both theoretically and experimentally that the part of the first pulse that does not overlap with the second can be recovered accurately, so the arrival time and amplitude of the first pulse can be estimated fairly precisely, but not the charge or particle type. None of these quantities can be estimated precisely for the second pulse when the two pulses overlap.}, number={3}, journal={JOURNAL OF INSTRUMENTATION}, author={Mishra, M. and Mattingly, J.}, year={2021}, month={Mar} }
 @article{weldon_mueller_awe_barbeau_hedges_li_mishra_mattingly_2020, title={Characterization of stilbene's scintillation anisotropy for recoil protons between 0.56 and 10 MeV}, volume={977}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2020.164178}, abstractNote={The scintillation anisotropy of the single-crystal organic scintillator trans-stilbene was characterized for recoil protons between 0.56 and 10 MeV. The light output and pulse shape anisotropies were measured at 11 distinct recoil proton energies for over 168 recoil proton trajectories relative to the crystal axes. The measurements were performed using a neutron scatter kinematic measurement system and quasi-monoenergetic neutron beams produced by the tandem Van de Graaff accelerator at Triangle Universities Nuclear Laboratory (TUNL). The extensive recoil proton directional coverage enables interpolation over both energy and direction to form a complete response function of stilbene’s scintillation anisotropy for the measured energy range.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Weldon, R. A., Jr. and Mueller, J. M. and Awe, C. and Barbeau, P. and Hedges, S. and Li, L. and Mishra, M. and Mattingly, J.}, year={2020}, month={Oct} }
 @article{manfredi_adamek_brown_brubaker_cabrera-palmer_cates_dorrill_druetzler_elam_feng_et al._2020, title={The Single-Volume Scatter Camera}, volume={11494}, ISBN={["978-1-5106-3794-8"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2569995}, abstractNote={The multi-institution Single-Volume Scatter Camera (SVSC) collaboration led by Sandia National Laboratories (SNL) is developing a compact, high-efficiency double-scatter neutron imaging system. Kinematic emission imaging of fission-energy neutrons can be used to detect, locate, and spatially characterize special nuclear material. Neutron-scatter cameras, analogous to Compton imagers for gamma ray detection, have a wide field of view, good event-by-event angular resolution, and spectral sensitivity. Existing systems, however, suffer from large size and/or poor efficiency. We are developing high-efficiency scatter cameras with small form factors by detecting both neutron scatters in a compact active volume. This effort requires development and characterization of individual system components, namely fast organic scintillators, photodetectors, electronics, and reconstruction algorithms. In this presentation, we will focus on characterization measurements of several SVSC candidate scintillators. The SVSC collaboration is investigating two system concepts: the monolithic design in which isotropically emitted photons are detected on the sides of the volume, and the optically segmented design in which scintillation light is channeled along scintillator bars to segmented photodetector readout. For each of these approaches, we will describe the construction and performance of prototype systems. We will conclude by summarizing lessons learned, comparing and contrasting the two system designs, and outlining plans for the next iteration of prototype design and construction.}, journal={HARD X-RAY, GAMMA-RAY, AND NEUTRON DETECTOR PHYSICS XXII}, author={Manfredi, Juan and Adamek, Evan and Brown, Joshua A. and Brubaker, Erik and Cabrera-Palmer, Belkis and Cates, Joshua W. and Dorrill, Ryan and Druetzler, Andrew and Elam, Jeff and Feng, Patrick L. and et al.}, year={2020} }
 @article{mishra_mattingly_kolbas_2019, title={Application of deconvolution to recover frequency-domain multiplexed detector pulses}, volume={929}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2019.03.043}, abstractNote={Multiplexing of radiation detectors reduces the number of readout channels, which in turn reduces the number of digitizer input channels for data acquisition.We recently demonstrated frequency domain multiplexing (FDM) of pulse mode radiation detectors using a resonator that converts the detector signal into a damped sinusoid by convolution.The detectors were given unique "tags" by the oscillation frequency of each resonator.The charge collected and the timeof-arrival of the detector pulse were estimated from the corresponding resonator output in the frequency domain.In this paper, we demonstrate a new method to recover the detector pulse from the damped sinusoidal output by deconvolution.Deconvolution converts the frequency-encoded detector signal back to the original detector pulse.We have developed a new prototype FDM system to multiplex organic scintillators based on convolution and deconvolution.Using the new prototype, the charge collected under the anode pulse can be estimated from the recovered pulse with an uncertainty of about 4.4 keVee (keV electron equivalent).The time-of-arrival can be estimated from the recovered pulse with an uncertainty of about 102 ps.We also used a CeBr 3 inorganic scintillator to measure the Cs-137 gamma spectrum using the recovered pulses and found a standard deviation of 13.8 keV at 662 keV compared to a standard deviation of 13.5 keV when the original pulses}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Mishra, M. and Mattingly, J. and Kolbas, R. M.}, year={2019}, month={Jun}, pages={57–65} }
 @article{mishra_mattingly_mueller_kolbas_2018, title={Frequency domain multiplexing of pulse mode radiation detectors}, volume={902}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2018.06.023}, abstractNote={Abstract The capability to multiplex scintillation detectors or other pulse mode radiation detectors is necessary in some applications where a large number of detectors is required. Frequency domain multiplexing has been previously implemented for applications in astronomy using amplitude modulation on radiation detectors such as transition-edge sensors. We propose an alternative method for multiplexing pulse mode radiation detectors in the frequency domain using convolution. We pass the detector signal to a resonator circuit that converts a detector pulse to a damped sinusoid of a specific frequency which gives a unique tag to the detector. We have developed a prototype frequency-domain multiplexed system for four EJ-309 organic scintillator detectors using four resonators of unique frequencies. The resonator outputs are combined using a fan-in circuit which is then connected to a single digitizer input. Using this system, we demonstrate that the charge collected under the original anode pulse can be estimated from the power spectrum of the damped sinusoid with a relative uncertainty of about 2%. The time-of-arrival of the anode pulse can be estimated using constant fraction discrimination applied to the leading edge of the damped sinusoid with an uncertainty of about 450 ps. We also used a CeBr 3 detector to test the performance of our system for spectroscopic applications and found only small degradation in the resolution for a multiplexed detector.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Mishra, M. and Mattingly, J. and Mueller, J. M. and Kolbas, R. M.}, year={2018}, month={Sep}, pages={117–122} }