@article{meric_alagoz_hysing_koegler_lathouwers_lionheart_mattingly_obhodas_pausch_pettersen_et al._2023, title={A hybrid multi-particle approach to range assessment-based treatment verification in particle therapy}, volume={13}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-023-33777-w}, abstractNote={Abstract}, number={1}, journal={SCIENTIFIC REPORTS}, author={Meric, Ilker and Alagoz, Enver B. and Hysing, Liv and Koegler, Toni and Lathouwers, Danny and Lionheart, William R. B. and Mattingly, John and Obhodas, Jasmina and Pausch, Guntram and Pettersen, Helge E. S. N. and et al.}, year={2023}, month={Apr} }
 @article{an_awe_barbeau_becker_belov_bernardi_bock_bolozdynya_bouabid_brown_et al._2023, title={Measurement of Electron-Neutrino Charged-Current Cross Sections on <SUP>127</SUP>I with the COHERENT NaIνE Detector}, volume={131}, ISSN={["1079-7114"]}, DOI={10.1103/PhysRevLett.131.221801}, abstractNote={Using an 185-kg NaI[Tl] array, COHERENT has measured the inclusive electron-neutrino charged-current cross section on ^{127}I with pion decay-at-rest neutrinos produced by the Spallation Neutron Source at Oak Ridge National Laboratory. Iodine is one the heaviest targets for which low-energy (≤50  MeV) inelastic neutrino-nucleus processes have been measured, and this is the first measurement of its inclusive cross section. After a five-year detector exposure, COHERENT reports a flux-averaged cross section for electron neutrinos of 9.2_{-1.8}^{+2.1}×10^{-40}  cm^{2}. This corresponds to a value that is ∼41% lower than predicted using the MARLEY event generator with a measured Gamow-Teller strength distribution. In addition, the observed visible spectrum from charged-current scattering on ^{127}I has been measured between 10 and 55 MeV, and the exclusive zero-neutron and one-or-more-neutron emission cross sections are measured to be 5.2_{-3.1}^{+3.4}×10^{-40} and 2.2_{-0.5}^{+0.4}×10^{-40}  cm^{2}, respectively.}, number={22}, journal={PHYSICAL REVIEW LETTERS}, author={An, P. and Awe, C. and Barbeau, P. S. and Becker, B. and Belov, V. and Bernardi, I. and Bock, C. and Bolozdynya, A. and Bouabid, R. and Brown, A. and et al.}, year={2023}, month={Dec} }
 @article{akimov_an_awe_barbeau_becker_belov_bernardi_blackston_bock_bolozdynya_et al._2022, title={COHERENT constraint on leptophobic dark matter using CsI data}, volume={106}, ISSN={["2470-0029"]}, DOI={10.1103/PhysRevD.106.052004}, abstractNote={We use data from the COHERENT CsI[Na] scintillation detector to constrain sub-GeV leptophobic dark matter models. This detector was built to observe low-energy nuclear recoils from coherent elastic neutrino-nucleus scattering. These capabilities enable searches for dark matter particles produced at the Spallation Neutron Source mediated by a vector portal particle with masses between 2 and 400 MeV/c 2 . No evidence for dark matter is observed and a limit on the mediator coupling to quarks is placed. This constraint improves upon previous results by two orders of magnitude. This newly explored parameter space probes the region where the dark matter relic abundance is explained by leptophobic dark matter when the mediator mass is roughly twice the dark matter mass. COHERENT sets the best constraint on leptophobic dark matter at these masses.}, number={5}, journal={PHYSICAL REVIEW D}, author={Akimov, D. and An, P. and Awe, C. and Barbeau, P. S. and Becker, B. and Belov, V. and Bernardi, I. and Blackston, M. A. and Bock, C. and Bolozdynya, A. and et al.}, year={2022}, month={Sep} }
 @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{michaud_schmidt_smith_mattingly_2021, title={A hierarchical Bayesian model for background variation in radiation source localization}, volume={1002}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2021.165288}, abstractNote={In this paper, we apply a new model to account for varying background radiation in radiological source localization. We present a hierarchical Bayesian model that simultaneously infers background and source location parameters without requiring separate estimation of the background radiation at each detector location. We employ a simplified photon transport model to reduce the computational expense of Bayesian model calibration. We demonstrate the model accuracy by localizing a cesium-137 source in a simulated city block, and we analyze experimental field measurements with varying background. In both cases, the model provides sufficient fidelity that we can locate the source while simultaneously estimating background radiation.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Michaud, Isaac J. and Schmidt, Kathleen and Smith, Ralph C. and Mattingly, John}, year={2021}, month={Jun} }
 @article{miles_cook_angers_swenson_kiedrowski_mattingly_smith_2021, title={Radiation Source Localization Using Surrogate Models Constructed from 3-D Monte Carlo Transport Physics Simulations}, volume={207}, ISSN={["1943-7471"]}, DOI={10.1080/00295450.2020.1738796}, abstractNote={Abstract Recent research has focused on the development of surrogate models for radiation source localization in a simulated urban domain. We employ the Monte Carlo N-Particle (MCNP) code to provide high-fidelity simulations of radiation transport within an urban domain. The model is constructed to employ a source location ( ) as input and return the estimated count rate for a set of specified detector locations. Because MCNP simulations are computationally expensive, we develop efficient and accurate surrogate models of the detector responses. We construct surrogate models using Gaussian processes and neural networks that we train and verify using the MCNP simulations. The trained surrogate models provide an efficient framework for Bayesian inference and experimental design. We employ Delayed Rejection Adaptive Metropolis (DRAM), a Markov Chain Monte Carlo algorithm, to infer the location and intensity of an unknown source. The DRAM results yield a posterior probability distribution for the source’s location conditioned on the observed detector count rates. The posterior distribution exhibits regions of high and low probability within the simulated environment identifying potential source locations. In this manner, we can quantify the source location to within at least one of these regions of high probability in the considered cases. Employing these methods, we are able to reduce the space of potential source locations by at least 60%.}, number={1}, journal={NUCLEAR TECHNOLOGY}, author={Miles, Paul R. and Cook, Jared A. and Angers, Zoey V. and Swenson, Christopher J. and Kiedrowski, Brian C. and Mattingly, John and Smith, Ralph C.}, year={2021}, month={Jan}, pages={37–53} }
 @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{clark_mattingly_favorite_2020, title={Application of Neutron Multiplicity Counting Experiments to Optimal Cross-Section Adjustments}, volume={194}, ISSN={["1943-748X"]}, DOI={10.1080/00295639.2019.1698267}, abstractNote={Abstract This paper presents the first application of model calibration to neutron multiplicity counting (NMC) experiments for cross-section optimization that is informed by adjoint-based sensitivity analysis (SA) and first-order uncertainty quantification (UQ). We summarize previous work on SA applied to NMC and describe notable modifications and additions. We give the procedure for first-order UQ and Bayesian-inference-based parameter estimation (PE). We then discuss model calibration applied to NMC of a 4.5-kg sphere of weapons-grade, alpha-phase plutonium metal (the BeRP ball) with the nPod neutron multiplicity counter. For the BeRP ball in bare and polyethylene-reflected configurations, we discuss the sensitivity of the first- and second-moment detector responses (i.e., first and second moments of the NMC distribution, respectively) to the cross sections. We describe the sources of uncertainty in the measured and simulated responses. Specifically, uncertainty in the measured responses is due to both random and systematic sources. Uncertainty in the simulated responses is due to the cross-section covariances. We describe in detail the adjustment to the cross sections and cross-section covariances due to the optimization. Due to the contribution of systematic uncertainties to the measured response uncertainties, the adjustment to the cross sections is similar in trend but larger in magnitude compared to that recommended by previous work. We compare the measured responses to responses simulated with nominal and optimized cross sections, demonstrating that the best-estimate cross sections produce simulations of NMC experiments that are more accurate with reduced uncertainty.}, number={4}, journal={NUCLEAR SCIENCE AND ENGINEERING}, author={Clark, Alexander R. and Mattingly, John and Favorite, Jeffrey A.}, year={2020}, month={Apr}, pages={308–333} }
 @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{bernstein_bowden_goldblum_huber_jovanovic_mattingly_2020, title={Colloquium: Neutrino detectors as tools for nuclear security (vol 92, 011003, 2020)}, volume={92}, ISSN={["1539-0756"]}, DOI={10.1103/RevModPhys.92.011003}, abstractNote={In 1930, Wolfgang Pauli proposed that conservation of energy and momentum in beta decay required the existence of a new particle: the neutrino. Since then experimental methods have matured to the point that neutrino detection now has an important practical application, namely, enhancing nuclear security. In this Colloquium the challenges and advances in the field of neutrino detection and their use in national security are discussed.}, number={1}, journal={REVIEWS OF MODERN PHYSICS}, author={Bernstein, Adam and Bowden, Nathaniel and Goldblum, Bethany L. and Huber, Patrick and Jovanovic, Igor and Mattingly, John}, year={2020}, month={Mar} }
 @article{weldon_mueller_mattingly_2020, title={Exploiting stilbene's scintillation anisotropy for neutron source localization}, volume={967}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2020.163834}, abstractNote={A technique for neutron source localization that exploits the scintillation anisotropy of stilbene is presented. The light output anisotropy of stilbene and constraints on the direction of recorded scatter events imposed by a threshold were used to estimate the direction of a 252Cf neutron source relative to the crystal axes of a stilbene crystal. The neutron source location was determined via triangulation using source directions estimated from multiple detectors. Two measurements that illustrate the efficacy of the technique are presented. The first measurement was designed with a favorable geometry for triangulation, which resulted in low uncertainties in the estimate of the neutron source location. The second measurement was designed with both favorable and unfavorable geometries for triangulation, which exhibited low and high uncertainties in the estimates of neutron source location, respectively. Pair-wise combinations of three detectors were used to estimate the source location for both measurements. The neutron source was localized with errors of 5.0, 8.9, and 3.9 cm for the first measurement with source detector-distance of 89, 90, and 88 cm for the three detectors. The neutron source was localized with errors of 2.8, 14.2, 6.2 cm for the second measurement with source detector-distances of 233, 123, and 130 cm.}, 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 Mattingly, J.}, year={2020}, month={Jul} }
 @article{weldon_mueller_barbeau_mattingly_2020, title={Measurement of EJ-228 plastic scintillator proton light output using a coincident neutron scatter technique}, volume={953}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2019.163192}, abstractNote={The light output function of the fast plastic scintillator EJ-228 was measured using a coincident neutron scatter measurement system and quasi-monoenergetic neutron beams produced by the tandem Van de Graaff accelerator at Triangle Universities Nuclear Laboratory. The measurement of scintillator light output using neutron scatter kinematics provides a model-independent determination of the light output function with quantifiable sources of uncertainty. Consequently, light output measurements performed using this method have a key advantage compared to other techniques: the characterization of the scintillating material depends only on the material itself and not on the size of the detector. This advantage is realized if the light output is defined as the absolute neutron light output relative to the absolute electron light output and two conditions are met: (1) the scintillator volume is fully illuminated and edge effects can be neglected during energy calibration measurements and light output measurements, and (2) the light attenuation length for scintillation photons in the material is long enough that the lowest energy interaction of interest produces a statistically significant number of scintillation photons for an interaction at any position in the scintillator volume. Commonly implemented measurement and analysis techniques for light output characterizations are explored and evidence of bias is provided for characterizations performed by analyzing the full-energy deposition edge of a light output spectrum.}, 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 Barbeau, P. and Mattingly, J.}, year={2020}, month={Feb} }
 @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{ytre-hauge_skjerdal_mattingly_meric_2019, title={A Monte Carlo feasibility study for neutron based real-time range verification in proton therapy}, volume={9}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-019-38611-w}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Ytre-Hauge, Kristian Smeland and Skjerdal, Kyrre and Mattingly, John and Meric, Ilker}, year={2019}, month={Feb} }
 @article{ytre-hauge_skjerdal_mattingly_meric_2019, title={A Monte Carlo feasibility study for neutron based real-time range verification in proton therapy (vol 170, 09001, 2018)}, volume={9}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-019-49488-0}, abstractNote={An amendment to this paper has been published and can be accessed via a link at the top of the paper.}, journal={SCIENTIFIC REPORTS}, author={Ytre-Hauge, Kristian Smeland and Skjerdal, Kyrre and Mattingly, John and Meric, Ilker}, year={2019}, month={Oct} }
 @article{cook_smith_hite_stefanescu_mattingly_2019, title={Application and Evaluation of Surrogate Models for Radiation Source Search}, volume={12}, ISSN={["1999-4893"]}, DOI={10.3390/a12120269}, abstractNote={Surrogate models are increasingly required for applications in which first-principles simulation models are prohibitively expensive to employ for uncertainty analysis, design, or control. They can also be used to approximate models whose discontinuous derivatives preclude the use of gradient-based optimization or data assimilation algorithms. We consider the problem of inferring the 2D location and intensity of a radiation source in an urban environment using a ray-tracing model based on Boltzmann transport theory. Whereas the code implementing this model is relatively efficient, extension to 3D Monte Carlo transport simulations precludes subsequent Bayesian inference to infer source locations, which typically requires thousands to millions of simulations. Additionally, the resulting likelihood exhibits discontinuous derivatives due to the presence of buildings. To address these issues, we discuss the construction of surrogate models for optimization, Bayesian inference, and uncertainty propagation. Specifically, we consider surrogate models based on Legendre polynomials, multivariate adaptive regression splines, radial basis functions, Gaussian processes, and neural networks. We detail strategies for computing training points and discuss the merits and deficits of each method.}, number={12}, journal={ALGORITHMS}, author={Cook, Jared A. and Smith, Ralph C. and Hite, Jason M. and Stefanescu, Razvan and Mattingly, John}, year={2019}, month={Dec} }
 @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{hite_mattingly_2019, title={Bayesian Metropolis methods for source localization in an urban environment}, volume={155}, ISSN={["0969-806X"]}, DOI={10.1016/j.radphyschem.2018.06.024}, abstractNote={We apply Bayesian techniques to determine the location and intensity of a gamma radiation source in an urban environment using count rates taken from a distributed detector network. A simplified model of the radiation transport process is used to construct a statistical model for the detector count rates in the presence of a randomly varying background. Markov Chain Monte Carlo is used to generate samples from the Bayesian posterior density, which can be used to inform search and interdiction efforts. We also present a modification of the traditional Metropolis sampling algorithm that allows us to incorporate fixed parameter uncertainties in building macroscopic cross sections and account for their effects on the posterior distribution. This method is then applied to a test problem based on a real urban geometry with different levels of uncertainty in the building cross sections. The results show that the uncertainty in the estimated source location is modest, even with a large degree of uncertainty in the building cross sections.}, journal={RADIATION PHYSICS AND CHEMISTRY}, author={Hite, Jason and Mattingly, John}, year={2019}, month={Feb}, pages={271–274} }
 @article{chapman_mueller_newby_mattingly_2019, title={Exploiting fission chain reaction dynamics to image fissile materials}, volume={935}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2019.05.001}, abstractNote={Abstract Radiation imaging is one potential method to verify nuclear weapons dismantlement. We present a method to discriminate between non-multiplying and multiplying neutron sources using a neutron coded aperture imaging system. This method applies time-correlated pulse-height (TCPH) analysis to identify neutrons in fission chain reactions and recreate images using only these events. This analysis was applied to measurements of weapons-grade plutonium (WGPu) metal and 252Cf performed at the Nevada National Security Site (NNSS) Device Assembly Facility in July 2015. The results demonstrate it is possible to eliminate the non-fissile 252Cf source from the image while preserving the fissile WGPu source. TCPH analysis was also applied to additional scenes in which the WGPu and 252Cf sources were measured individually. The results of these separate measurements further demonstrate the ability to remove the non-fissile 252Cf source and retain the fissile WGPu source. Simulations performed using MCNPX-PoliMi indicate that in a one hour measurement, hollow WGPu spheres are retained at a 1 σ level for neutron multiplications M ≃ 2 . 7 and above. This work has potential application to dismantlement verification where it may be valuable to verify that all neutron sources in an image are multiplying.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Chapman, Pete and Mueller, Jonathan and Newby, Jason and Mattingly, John}, year={2019}, month={Aug}, pages={198–206} }
 @article{weldon_mueller_lynch_schuster_hedges_awe_li_barbeau_mattingly_2019, title={High-precision characterization of the neutron light output of stilbene along the directions of maximum and minimum response}, volume={927}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2018.10.075}, abstractNote={The scintillation light output response of stilbene crystals has been measured for protons recoiling along the a, b, and c’ crystalline axes with energies between 1.3 and 10 MeV using neutrons produced with the tandem Van de Graaff accelerator at Triangle Universities Nuclear Laboratory. The proton recoil energy and direction were measured using the coincident detection of neutrons between a stilbene scintillator and an array of EJ-309 liquid scintillators spanning arranged neutron recoil angles. The maximum light output was found to coincide with proton recoils along the a-axis, in disagreement with other published measurements, which reported the b-axis as the direction of the maximum light output. Additional measurements were conducted using two different stilbene crystals to confirm these results: a second measurement using the coincident detection of neutrons; measurements of neutron full energy deposition events along the a and b axes; and measurements of the count rate for 252Cf neutrons traveling along the a and b axes directions. All measurements found that recoils along the a-axis produce the maximum light output.}, 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 Lynch, C. and Schuster, P. and Hedges, S. and Awe, C. and Li, L. and Barbeau, P. and Mattingly, J.}, year={2019}, month={May}, pages={313–319} }
 @article{hite_mattingly_archer_willis_rowe_bray_carter_ghawaly_2019, title={Localization of a radioactive source in an urban environment using Bayesian Metropolis methods}, volume={915}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2018.09.032}, abstractNote={Abstract We present a method for localizing an unknown source of radiation in an urban environment using a distributed detector network. This method employs statistical parameter estimation techniques, relying on an approximation for the response of a detector to the source based on a simplified model of the underlying transport phenomena, combined with a Metropolis-type sampler that is modified to propagate the effect of fixed epistemic uncertainties in the material macroscopic cross sections of objects in the scene. We apply this technique to data collected during a measurement campaign conducted in a realistic analog for an urban scene using a network of six mobile detectors. Our initial results are able to localize the source to within approximately 8 m over a scene of size 300 m × 200 m in two independent trials with 30 min count times, including a characterization of the uncertainty associated with the poorly known macroscopic cross sections of objects in the scene. In these measurements, the nearest detectors were between 20 m to 30 m from the source, and recorded count rates between approximately 3 and 13 times background. A few detectors had line-of-sight to the source, while the majority were obscured by objects present in the scene. After extending our model to account for the orientation of the detectors and correcting for anomalies in the measurement data we were able to further improve the localization accuracy to approximately 2 m in both trials.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Hite, Jason and Mattingly, John and Archer, Dan and Willis, Michael and Rowe, Andrew and Bray, Kayleigh and Carter, Jake and Ghawaly, James}, year={2019}, month={Jan}, pages={82–93} }
 @article{schmidt_smith_hite_mattingly_azmy_rajan_goldhahn_2019, title={Sequential optimal positioning of mobile sensors using mutual information}, volume={12}, ISSN={["1932-1872"]}, DOI={10.1002/sam.11431}, abstractNote={Abstract}, number={6}, journal={STATISTICAL ANALYSIS AND DATA MINING}, author={Schmidt, Kathleen and Smith, Ralph C. and Hite, Jason and Mattingly, John and Azmy, Yousry and Rajan, Deepak and Goldhahn, Ryan}, year={2019}, month={Dec}, pages={465–478} }
 @article{stefanescu_hite_cook_smith_mattingly_2019, title={Surrogate-Based Robust Design for a Non-Smooth Radiation Source Detection Problem}, volume={12}, ISSN={["1999-4893"]}, DOI={10.3390/a12060113}, abstractNote={In this paper, we develop and numerically illustrate a robust sensor network design to optimally detect a radiation source in an urban environment. This problem exhibits several challenges: penalty functionals are non-smooth due to the presence of buildings, radiation transport models are often computationally expensive, sensor locations are not limited to a discrete number of points, and source intensity and location responses, based on a fixed number of sensors, are not unique. We consider a radiation source located in a prototypical 250 m × 180 m urban setting. To address the non-smooth properties of the model and computationally expensive simulation codes, we employ a verified surrogate model based on radial basis functions. Using this surrogate, we formulate and solve a robust design problem that is optimal in an average sense for detecting source location and intensity with minimized uncertainty.}, number={6}, journal={ALGORITHMS}, author={Stefanescu, Razvan and Hite, Jason and Cook, Jared and Smith, Ralph C. and Mattingly, John}, year={2019}, month={Jun} }
 @article{brayfindley_smith_mattingly_brigantic_2018, title={Automated Defect Detection in Spent Nuclear Fuel Using Combined Cerenkov Radiation and Gamma Emission Tomography Data}, volume={204}, ISSN={0029-5450 1943-7471}, url={http://dx.doi.org/10.1080/00295450.2018.1490123}, DOI={10.1080/00295450.2018.1490123}, abstractNote={Abstract Spent fuel monitoring and characterization has been central to safeguards and nuclear facility monitoring for many years. The Digital Cerenkov Viewing Device (DCVD) has been used since the 1980s as a method of defect detection in spent fuel. In recent years, the accounting for large quantities of spent fuel before storage has renewed interest in this relatively quick and inexpensive method. This has an impact not only in safeguards, but also for nuclear power facilities, as accounting can be a long, arduous, and costly process. Additionally, the DCVD demonstrates limited accuracy in more complex cases such as substitution of a fuel rod with steel or a partial defect detection. A second method, gamma emission tomography (GET) has been explored as an improved defect detection method, but is much more expensive and invasive than DCVD. The present investigation identifies deficiencies in both methods and proposes a combination of data gathered from each method to address these deficiencies for improved spent fuel characterization. Initial results are promising, showing 97% detection of a single missing fuel rod when the data types are combined, versus approximately 50% and 70%, respectively, for DCVD and GET data on their own. These classification results are obtained with algorithms derived from facial recognition and applied to this problem, yielding unique accuracy in near real time while also maintaining the information barrier between output and measurement desired in safeguards.}, number={3}, journal={Nuclear Technology}, publisher={Informa UK Limited}, author={Brayfindley, Eva and Smith, Ralph C. and Mattingly, John and Brigantic, Robert}, year={2018}, month={Aug}, pages={343–353} }
 @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} }
 @article{weinfurther_mattingly_brubaker_steele_2018, title={Model-based design evaluation of a compact, high-efficiency neutron scatter camera}, volume={883}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2017.11.025}, abstractNote={This paper presents the model-based design and evaluation of an instrument that estimates incident neutron direction using the kinematics of neutron scattering by hydrogen-1 nuclei in an organic scintillator. The instrument design uses a single, nearly contiguous volume of organic scintillator that is internally subdivided only as necessary to create optically isolated pillars. Scintillation light emitted in a given pillar is confined to that pillar by a combination of total internal reflection and a specular reflector applied to the four sides of the pillar transverse to its long axis. The scintillation light is collected at each end of the pillar using a photodetector. In this optically segmented design, the (x, y) position of scintillation light emission (where the x and y coordinates are transverse to the long axis of the pillars) is estimated as the pillar's (x, y) position in the scintillator "block", and the z-position (the position along the pillar's long axis) is estimated from the amplitude and relative timing of the signals produced by the photodetectors at each end of the pillar. For proton recoils greater than 1 MeV, we show that the (x, y, z)-position of neutron-proton scattering can be estimated with < 1 cm root-mean-squared [RMS] error and the proton recoil energy can be estimated with < 50 keV RMS error by fitting the photodetectors' response time history to models of optical photon transport within the scintillator pillars. Finally, we evaluate several alternative designs of this proposed single-volume scatter camera made of pillars of plastic scintillator (SVSC-PiPS), studying the effect of pillar dimensions, scintillator material, and photodetector response vs. time. Specifically, we conclude that an SVSC-PiPS constructed using EJ-204 and an MCP-PM will produce the most precise estimates of incident neutron direction and energy.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Weinfurther, Kyle and Mattingly, John and Brubaker, Erik and Steele, John}, year={2018}, month={Mar}, pages={115–135} }
 @article{mueller_mattingly_2018, title={Passive one-dimensional self-transmission imaging of subcritical metallic plutonium assemblies}, volume={903}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2018.06.070}, DOI={10.1016/J.NIMA.2018.06.070}, abstractNote={We present a new passive technique to assess the spatial extent of subcritical metallic assemblies of plutonium. This technique could be used in disarmament verification where the size of the assembly is a verification attribute. The technique is based on measurements of neutron and gamma-ray coincidences from fission events within special nuclear material (SNM) and is analogous to active transmission imaging where the interrogating source is the SNM itself. Experimental measurements were performed using a 252Cf source and a 4.5 kg sphere of weapons-grade plutonium metal. These measurements and Monte Carlo simulations demonstrate that this technique is highly sensitive to the outer radius of metallic spherical assemblies of plutonium and moderately sensitive to the presence of a void inside the plutonium.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Mueller, J.M. and Mattingly, J.}, year={2018}, month={Sep}, pages={277–286} }
 @article{ştefănescu_schmidt_hite_smith_mattingly_2017, title={Hybrid optimization and Bayesian inference techniques for a non-smooth radiation detection problem}, volume={111}, ISSN={0029-5981}, url={http://dx.doi.org/10.1002/nme.5491}, DOI={10.1002/nme.5491}, abstractNote={We propose several algorithms to recover the location and intensity of a radiation source located in a simulated 250 × 180 m block of an urban center based on synthetic measurements. Radioactive decay and detection are Poisson random processes, so we employ likelihood functions based on this distribution. Owing to the domain geometry and the proposed response model, the negative logarithm of the likelihood is only piecewise continuous differentiable, and it has multiple local minima. To address these difficulties, we investigate three hybrid algorithms composed of mixed optimization techniques. For global optimization, we consider simulated annealing, particle swarm, and genetic algorithm, which rely solely on objective function evaluations; that is, they do not evaluate the gradient in the objective function. By employing early stopping criteria for the global optimization methods, a pseudo‐optimum point is obtained. This is subsequently utilized as the initial value by the deterministic implicit filtering method, which is able to find local extrema in non‐smooth functions, to finish the search in a narrow domain. These new hybrid techniques, combining global optimization and implicit filtering address, difficulties associated with the non‐smooth response, and their performances, are shown to significantly decrease the computational time over the global optimization methods. To quantify uncertainties associated with the source location and intensity, we employ the delayed rejection adaptive Metropolis and DiffeRential Evolution Adaptive Metropolis algorithms. Marginal densities of the source properties are obtained, and the means of the chains compare accurately with the estimates produced by the hybrid algorithms. Copyright © 2016 John Wiley & Sons, Ltd.}, number={10}, journal={International Journal for Numerical Methods in Engineering}, publisher={Wiley}, author={Ştefănescu, Răzvan and Schmidt, Kathleen and Hite, Jason and Smith, Ralph C. and Mattingly, John}, year={2017}, month={Feb}, pages={955–982} }
 @article{o'brien_mattingly_anistratov_2017, title={Sensitivity Analysis of Neutron Multiplicity Counting Statistics Using First-Order Perturbation Theory and Application to a Subcritical Plutonium Metal Benchmark}, volume={185}, ISSN={["1943-748X"]}, DOI={10.1080/00295639.2016.1272988}, abstractNote={Abstract It is frequently important to estimate the uncertainty and sensitivity of measured and computed detector responses in subcritical experiments and simulations. These uncertainties arise from the physical construction of the experiment, uncertainties in the transport parameters, and counting uncertainties. Perturbation theory enables sensitivity analysis (SA) and uncertainty quantification on integral quantities like detector responses. The aim of our work is to apply SA to the statistics of subcritical neutron multiplicity counting distributions. Current SA methods have only been applied to mean detector responses and the eigenvalue. For multiplicity counting experiments, knowledge of the higher-order counting moments and their uncertainties are essential for a complete SA. We apply perturbation theory to compute the sensitivity of neutron multiplicity counting moments to arbitrarily high order. Each moment is determined by solving an adjoint transport equation with a source term that is a function of the adjoint solutions for lower-order moments. This enables moments of arbitrarily high order to be sequentially determined, and it shows that each moment is sensitive to the uncertainties of all lower-order moments. To close our SA of the moments, we derive forward transport equations that are functions of the forward flux and lower-order moment adjoint fluxes. We verify our calculations for the first three moments by comparison with multiplicity counting measurements of a subcritical plutonium metal sphere. For the first three moments, the most influential parameters are ranked, and the validity of first-order perturbation theory is demonstrated by examining the series truncation error. This enables a detailed SA of subcritical multiplicity counting measurements of fissionable material based on transport theory.}, number={3}, journal={NUCLEAR SCIENCE AND ENGINEERING}, author={O'Brien, Sean and Mattingly, John and Anistratov, Dmitriy}, year={2017}, month={Mar}, pages={406–425} }
 @inproceedings{hite_mattingly_schmidt_stelanescu_smith_2016, title={Bayesian metropolis methods applied to sensor networks for radiation source localization}, DOI={10.1109/mfi.2016.7849519}, abstractNote={We present an application of statistical techniques to the localization of an unknown gamma source in an urban environment. By formulating the problem as a task of Bayesian parameter estimation, we are able to apply Markov Chain Monte Carlo (MCMC) to generate a full posterior probability density estimating the source location and intensity based on counts reported from a distributed detector network. To facilitate the calibration procedure, we employ a simplified photon transport model with low computational cost and test the proposed methodology in a simulated urban environment, with calibration data generated using the radiation transport code MCNP. The Bayesian methodology is able to identify the source location and intensity along with providing a full posterior density.}, booktitle={2016 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI)}, author={Hite, J. M. and Mattingly, J. K. and Schmidt, K. L. and Stelanescu, R. and Smith, Ralph}, year={2016}, pages={389–393} }
 @article{mueller_mattingly_2016, title={Using anisotropies in prompt fission neutron coincidences to assess the neutron multiplication of highly multiplying subcritical plutonium assemblies}, volume={825}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2016.04.027}, abstractNote={Abstract There is a significant and well-known anisotropy between the prompt neutrons emitted from a single fission event; these neutrons are most likely to be observed at angles near 0° or 180° relative to each other. However, the propagation of this anisotropy through different generations of a fission chain reaction has not been previously studied. We have measured this anisotropy in neutron–neutron coincidences from a subcritical highly-multiplying assembly of plutonium metal. The assembly was a 4.5 kg α-phase plutonium metal sphere composed of 94% 239Pu and 6% 240Pu by mass. Data were collected using two EJ-309 liquid scintillators and two EJ-299 plastic scintillators. The angular distribution of neutron–neutron coincidences was measured at 90° and 180° and found to be largely isotropic. Simulations were performed using MCNPX-PoliMi of similar plutonium metal spheres of varying sizes and a correlation between the neutron multiplication of the assembly and the anisotropy of neutron–neutron coincidences was observed. In principle, this correlation could be used to assess the neutron multiplication of an unknown assembly.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Mueller, J. M. and Mattingly, J.}, year={2016}, month={Jul}, pages={87–92} }
 @article{miller_mattingly_clarke_solomon_dennis_meldrum_pozzi_2014, title={Computational Evaluation of Neutron Multiplicity Measurements of Polyethylene-Reflected Plutonium Metal}, volume={176}, ISSN={["1943-748X"]}, DOI={10.13182/nse12-53}, abstractNote={Abstract Simulations of neutron multiplicity measurements of a highly multiplicative plutonium sphere measured with a moderated array of 3He proportional counters have consistently overpredicted the mean and variance of the measured multiplicity distribution. In contrast, identical experiments using a 252Cf source have been accurately simulated. This paper outlines a sensitivity analysis of several key parameters that could account for the overprediction in the simulation of the plutonium sphere. Parameters that were analyzed include source-detector distance, detector dead time, variations in density and volume of the plutonium, and the value of for v̄ 239Pu-induced fission. Of these parameters, the only factor that accounted for the overprediction within reasonable bounds was a change in the value of the 239Pu v̄. The sensitivity analysis showed that a small change (1.14% reduction) in the value of v̄ dramatically improved the simulated results.}, number={2}, journal={NUCLEAR SCIENCE AND ENGINEERING}, author={Miller, E. C. and Mattingly, J. K. and Clarke, S. D. and Solomon, C. J. and Dennis, B. and Meldrum, A. and Pozzi, S. A.}, year={2014}, month={Feb}, pages={167–185} }
 @inproceedings{anderson_mattingly_2014, title={Gamma spectroscopy-based inverse radiation transport problem stability analysis}, booktitle={Institute of Nuclear Materials Management Annual Meeting}, author={Anderson, D. and Mattingly, J.}, year={2014} }
 @article{meric_johansen_mattingly_gardner_2014, title={On the ill-conditioning of the multiphase flow measurement by prompt gamma-ray neutron activation analysis}, volume={95}, ISSN={["0969-806X"]}, DOI={10.1016/j.radphyschem.2012.12.047}, abstractNote={Abstract Prompt gamma-ray neutron activation analysis (PGNAA) in conjunction with the so-called Monte Carlo library least-square (MCLLS) approach for the quantitative analysis is currently considered for rapid, non-intrusive and online measurements of multiphase oil/gas/seawater flow. The results of this work indicate that the current method would be feasible for measurements of multiphase flow provided that the ill-conditioning in the MCLLS approach could be treated appropriately.}, journal={RADIATION PHYSICS AND CHEMISTRY}, author={Meric, Ilker and Johansen, Geir A. and Mattingly, J. and Gardner, R. P.}, year={2014}, month={Feb}, pages={401–404} }
 @article{evans_mattingly_cacuci_2014, title={Sensitivity Analysis and Data Assimilation in a Subcritical Plutonium Metal Benchmark}, volume={176}, ISSN={["1943-748X"]}, DOI={10.13182/nse13-24}, abstractNote={Abstract This work presents the application of first-order adjoint sensitivity analysis, uncertainty quantification, and data assimilation to a subcritical plutonium benchmark experiment using a modified version of the discrete ordinates radiation transport code Denovo. Previous Monte Carlo simulations of this benchmark saw a consistent overprediction of the mean and variance of the measured neutron multiplicity distribution. It was observed that a small scalar reduction in the value of the 239Pu-induced fission neutron multiplicity was capable of significantly reducing the discrepancies. This work extends those results by computing first-order sensitivities to each nuclide, reaction type, energy, and material region in the benchmark. The sensitivities are then used in a data assimilation methodology to simultaneously calibrate all responses and multigroup nuclear data. The resulting best-estimate values for the energy group differential multiplicity ν̄(Eg) are 1σ to 2σ less than the nominal values found in ENDF/B-VII for energies less than ˜1.5 MeV.}, number={3}, journal={NUCLEAR SCIENCE AND ENGINEERING}, author={Evans, Richard T. and Mattingly, John K. and Cacuci, Dan G.}, year={2014}, month={Mar}, pages={325–338} }
 @inproceedings{anderson_mattingly_2013, title={Inverse radiation transport problem stability analysis}, volume={109}, booktitle={American Nuclear Society Winter Meeting}, author={Anderson, D. and Mattingly, J.}, year={2013} }
 @article{alamaniotis_mattingly_tsoukalas_2013, title={Kernel-Based Machine Learning for Background Estimation of NaI Low-Count Gamma-Ray Spectra}, volume={60}, ISSN={["1558-1578"]}, DOI={10.1109/tns.2013.2260868}, abstractNote={Virtually all gamma-ray spectrometry measurements contain background components due to the ubiquitous presence of primordial radionuclides in the Earth's crust and cosmic radiation interactions high in the Earth's atmosphere. In principle, spectral signatures due to radiation source(s) of actual interest can be extracted from the measured gamma-ray spectrum by background subtraction. However, if separate background measurements are unavailable or infeasible, and particularly for measurements exhibiting low signal-to-noise ratio (SNR), background subtraction is nontrivial, and it requires accurate background estimation . An example application of gamma-ray spectroscopy with low SNR is the “source search” scenario, where the position of a source is sought using measurements taken over very short time intervals by a detector in motion. We have developed an algorithm for background estimation in low-count gamma-ray spectra using kernel-based Gaussian processes (GP) taken from the field of machine learning. We have evaluated the performance of our algorithm using a group of three kernels tested against a dataset composed of background spectra measured in an urban environment using a mobile sodium iodide (NaI) detector. We have also simulated datasets containing nonbackground gamma-ray sources in an urban background measured with a NaI detector. The simulated scenarios employed a variety of source-detector distances and different types of source shielding. As a metric of algorithm performance, we calculated correlation coefficients, Theil inequality coefficients, and count difference statistics between estimated and actual backgrounds. We concluded that our method adequately estimates the gamma-ray background, but we also observed a strong dependence of the algorithm's performance on the selected kernel.}, number={3}, journal={IEEE TRANSACTIONS ON NUCLEAR SCIENCE}, author={Alamaniotis, Miltiadis and Mattingly, John and Tsoukalas, Lefteri H.}, year={2013}, month={Jun}, pages={2209–2221} }
 @article{alamaniotis_mattingly_tsoukalas_2013, title={Pareto-Optimal Gamma Spectroscopic Radionuclide Identification Using Evolutionary Computing}, volume={60}, ISSN={["1558-1578"]}, DOI={10.1109/tns.2013.2260869}, abstractNote={Detection and identification of special nuclear materials (SNM) in measured gamma spectra is a challenge for nuclear security applications of spectroscopy. There are ongoing international efforts in industry, academia, and government to develop accurate, robust automated methods of gamma spectroscopic analysis to identify signature patterns characteristic of SNM. In this paper, we introduce a new approach for processing gamma-ray spectra measured by an NaI detector. The approach searches for radionuclide signature patterns in the measured spectrum by formulating a multiobjective optimization problem. Search in the multiobjective space is performed by an evolutionary algorithm, which identifies a solution in the context of Pareto Optimality Theory. The proposed approach is composed of two main steps: 1) signature selection, and 2) Pareto-optimal fitting. The output of the algorithm includes a list of all the identified radionuclides and their relative contributions to the gamma spectrum. The methodology is applied to a set of gamma spectra and compared to multiple linear regression fitting. Results demonstrate the superiority of the Pareto-optimal approach over multiple regression in the majority of the tested cases.}, number={3}, journal={IEEE TRANSACTIONS ON NUCLEAR SCIENCE}, author={Alamaniotis, Miltiadis and Mattingly, John and Tsoukalas, Lefteri H.}, year={2013}, month={Jun}, pages={2222–2231} }
 @article{miller_dolan_clarke_pozzi_tomanin_peerani_marleau_mattingly_2013, title={Time-correlated pulse-height measurements of low-multiplying nuclear materials}, volume={729}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2013.06.062}, abstractNote={Methods for the determination of the subcritical neutron multiplication of nuclear materials are of interest in the field of nuclear nonproliferation and safeguards. A series of measurements were performed at the Joint Research Center facility in Ispra, Italy to investigate the possibility of using a time-correlated pulse-height (TCPH) analysis to estimate the sub-critical multiplication of nuclear material. The objective of the measurements was to evaluate the effectiveness of this technique, and to benchmark the simulation capabilities of MCNPX-PoliMi/MPPost. In this campaign, two low-multiplication samples were measured: a 1-kg mixed oxide (MOX) powder sample and several low-mass plutonium–gallium (PuGa) disks. The measured results demonstrated that the sensitivity of the TCPH technique could not clearly distinguish samples with very-low levels of multiplication. However, the simulated TCPH distributions agree well with the measured data, within 12% for all cases, validating the simulation capabilities of MCNPX-PoliMi/MPPost. To investigate the potential of the TCPH method for identifying high-multiplication samples, the validated MCNPX-PoliMi/MPPost codes were used to simulate sources of higher multiplications. Lastly, a characterization metric, the cumulative region integral (CRI), was introduced to estimate the level of multiplication in a source. However, this response was shown to be insensitive over the range of multiplications of interest.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Miller, E. C. and Dolan, J. L. and Clarke, S. D. and Pozzi, S. A. and Tomanin, A. and Peerani, P. and Marleau, P. and Mattingly, J. K.}, year={2013}, month={Nov}, pages={108–116} }
 @article{mattingly_mitchell_2012, title={Implementation and testing of a multivariate inverse radiation transport solver}, volume={70}, ISSN={["0969-8043"]}, DOI={10.1016/j.apradiso.2011.10.020}, abstractNote={Detection, identification, and characterization of special nuclear materials (SNM) all face the same basic challenge: to varying degrees, each must infer the presence, composition, and configuration of the SNM by analyzing a set of measured radiation signatures. Solutions to this problem implement inverse radiation transport methods. Given a set of measured radiation signatures, inverse radiation transport estimates properties of the source terms and transport media that are consistent with those signatures. This paper describes one implementation of a multivariate inverse radiation transport solver. The solver simultaneously analyzes gamma spectrometry and neutron multiplicity measurements to fit a one-dimensional radiation transport model with variable layer thicknesses using nonlinear regression. The solver's essential components are described, and its performance is illustrated by application to benchmark experiments conducted with plutonium metal.}, number={7}, journal={APPLIED RADIATION AND ISOTOPES}, author={Mattingly, John and Mitchell, Dean J.}, year={2012}, month={Jul}, pages={1136–1140} }
 @article{pozzi_clarke_walsh_miller_dolan_flaska_wieger_enqvist_padovani_mattingly_et al._2012, title={MCNPX-PoliMi for nuclear nonproliferation applications}, volume={694}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2012.07.040}, DOI={10.1016/J.NIMA.2012.07.040}, abstractNote={This paper describes the use of the Monte Carlo code MCNPX-PoliMi for nuclear-nonproliferation applications, with particular emphasis on the simulation of spontaneous and neutron-induced nuclear fission. New models for the outgoing neutrons and gamma rays emitted in spontaneous and induced fission are described. For spontaneous fission, the models include prompt neutron energy distributions that depend on the number of neutrons emitted in the individual fission events. For neutron-induced fission, due to lack of data, the prompt neutron energy distributions are independent of the number of neutrons emitted in the individual fission events. Gamma rays are sampled independently of the neutrons. Code validation is performed on well-characterized mixed-oxide fuel and plutonium-oxide samples.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Pozzi, S.A. and Clarke, S.D. and Walsh, W.J. and Miller, E.C. and Dolan, J.L. and Flaska, M. and Wieger, B.M. and Enqvist, A. and Padovani, E. and Mattingly, J.K. and et al.}, year={2012}, month={Dec}, pages={119–125} }
 @article{meric_johansen_holstad_mattingly_gardner_2012, title={On the treatment of ill-conditioned cases in the Monte Carlo library least-squares approach for inverse radiation analyzers}, volume={23}, ISSN={["1361-6501"]}, DOI={10.1088/0957-0233/23/5/055603}, abstractNote={Prompt gamma-ray neutron activation analysis (PGNAA) has been and still is one of the major methods of choice for the elemental analysis of various bulk samples. This is mostly due to the fact that PGNAA offers a rapid, non-destructive and on-line means of sample interrogation. The quantitative analysis of the prompt gamma-ray data could, on the other hand, be performed either through the single peak analysis or the so-called Monte Carlo library least-squares (MCLLS) approach, of which the latter has been shown to be more sensitive and more accurate than the former. The MCLLS approach is based on the assumption that the total prompt gamma-ray spectrum of any sample is a linear combination of the contributions from the individual constituents or libraries. This assumption leads to, through the minimization of the chi-square value, a set of linear equations which has to be solved to obtain the library multipliers, a process that involves the inversion of the covariance matrix. The least-squares solution may be extremely uncertain due to the ill-conditioning of the covariance matrix. The covariance matrix will become ill-conditioned whenever, in the subsequent calculations, two or more libraries are highly correlated. The ill-conditioning will also be unavoidable whenever the sample contains trace amounts of certain elements or elements with significantly low thermal neutron capture cross-sections. In this work, a new iterative approach, which can handle the ill-conditioning of the covariance matrix, is proposed and applied to a hydrocarbon multiphase flow problem in which the parameters of interest are the separate amounts of the oil, gas, water and salt phases. The results of the proposed method are also compared with the results obtained through the implementation of a well-known regularization method, the truncated singular value decomposition. Final calculations indicate that the proposed approach would be able to treat ill-conditioned cases appropriately.}, number={5}, journal={MEASUREMENT SCIENCE AND TECHNOLOGY}, author={Meric, Ilker and Johansen, Geir A. and Holstad, Marie B. and Mattingly, John and Gardner, Robin P.}, year={2012}, month={May} }
 @article{mattingly_mitchell_harding_2011, title={Experimental validation of a coupled neutron–photon inverse radiation transport solver}, volume={652}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2011.01.139}, DOI={10.1016/J.NIMA.2011.01.139}, abstractNote={Sandia National Laboratories has developed an inverse radiation transport solver that applies nonlinear regression to coupled neutron–photon deterministic transport models. The inverse solver uses nonlinear regression to fit a radiation transport model to gamma spectrometry and neutron multiplicity counting measurements. The subject of this paper is the experimental validation of that solver. This paper describes a series of experiments conducted with a 4.5 kg sphere of α-phase, weapons-grade plutonium. The source was measured bare and reflected by high-density polyethylene (HDPE) spherical shells with total thicknesses between 1.27 and 15.24 cm. Neutron and photon emissions from the source were measured using three instruments: a gross neutron counter, a portable neutron multiplicity counter, and a high-resolution gamma spectrometer. These measurements were used as input to the inverse radiation transport solver to evaluate the solver's ability to correctly infer the configuration of the source from its measured radiation signatures.}, number={1}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Mattingly, John and Mitchell, Dean J. and Harding, Lee T.}, year={2011}, month={Oct}, pages={537–539} }
 @article{miller_dennis_clarke_pozzi_mattingly_2011, title={Simulation of polyethylene-moderated plutonium neutron multiplicity measurements}, volume={652}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2011.01.042}, DOI={10.1016/J.NIMA.2011.01.042}, abstractNote={Neutron multiplicity measurements are a useful technique for the characterization of special nuclear material. This technique relies on the detection of correlated neutrons from fission events. As correlated events are detected it is possible to determine the neutron multiplicity distribution for the sample. This distribution is useful for identifying the material and estimating the mass. This work focuses on the ability of the Monte Carlo code MCNP-PoliMi to simulate measured distributions. The experiment used as the basis of comparison consisted of a 4.5 kg plutonium metal sphere surrounded by up to 6 in. of polyethylene. A bank of 15 3He detectors was used to detect the correlated neutron events. MCNP-PoliMi was used to simulate the particle transport and a post-processing algorithm was developed to apply detector deadtime effects and to determine the neutron multiplicity distributions. These simulated distributions were then compared to the measured results. The simulation provided an adequate estimation of the measured data. However, we observed a systematic over-prediction in both the mean and the variance of the measured distribution.}, number={1}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Miller, E.C. and Dennis, B. and Clarke, S.D. and Pozzi, S.A. and Mattingly, J.K.}, year={2011}, month={Oct}, pages={540–543} }
 @article{mihalczo_mattingly_neal_mullens_2004, title={NMIS plus gamma spectroscopy for attributes of HEU, PU and HE detection}, volume={213}, ISSN={0168-583X}, url={http://dx.doi.org/10.1016/S0168-583X(03)01651-3}, DOI={10.1016/S0168-583X(03)01651-3}, abstractNote={A combined nuclear materials identification system–gamma ray spectrometry system can be used passively to obtain the following attributes of Pu: presence, fissile mass, 240/239 ratio and metal versus oxide. This system can also be used with a small, portable, DT neutron generator to measure the attributes of highly enriched uranium (HEU): presence, fissile mass, enrichment, metal versus oxide; and detect the presence of high explosives (HE). For the passive system, time-dependent coincidence distributions can be used for the presence, fissile mass, metal versus oxide for Pu, 240/239 ratio, and gamma ray spectrometry can also be used for 240/239 ratio and presence, allowing presence and 240/239 ratio to be confirmed by two methods. For the active system with a DT neutron generator, all relevant attributes for both Pu and HEU can be determined from various features of the time-dependent coincidence distribution measurements. Active gamma ray spectrometry would determine the presence of HE. The various features of time-dependent coincidence distributions and gamma ray spectrometry that determine these attributes are discussed with some examples from previous determinations.}, journal={Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms}, publisher={Elsevier BV}, author={Mihalczo, J.T. and Mattingly, J.K. and Neal, J.S. and Mullens, J.A.}, year={2004}, month={Jan}, pages={378–384} }