@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{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{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={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 1σ 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{yan_mueller_ahmed_hao_huang_li_litvinenko_liu_mikhailov_popov_et al._2019, title={Precision control of gamma-ray polarization using a crossed helical undulator free-electron laser}, volume={13}, ISSN={["1749-4893"]}, DOI={10.1038/s41566-019-0467-6}, number={9}, journal={NATURE PHOTONICS}, author={Yan, Jun and Mueller, Jonathan M. and Ahmed, Mohammad W. and Hao, Hao and Huang, Senlin and Li, Jingyi and Litvinenko, Vladimir N. and Liu, Peifan and Mikhailov, Stepan F. and Popov, Victor G. and et al.}, year={2019}, month={Sep}, pages={629–635} }
 @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={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 CeBr3 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} }
 @inproceedings{mueller_ahmed_weller_2018, title={Measurements and simulations of prompt neutron polarization asymmetries in photofission}, booktitle={Fission and Properties of Neutron-Rich Nuclei}, author={Mueller, J. M. and Ahmed, M. W. and Weller, H. R.}, year={2018}, pages={547–554} }
 @article{matei_mueller_sikora_suliman_ur_weller_2016, title={Investigation of the d(gamma,n)p reaction for gamma beam monitoring at ELI-NP}, volume={11}, journal={Journal of Instrumentation}, author={Matei, C. and Mueller, J. M. and Sikora, M. H. and Suliman, G. and Ur, C. A. and Weller, H. R.}, year={2016} }
 @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{mueller_ahmed_davis_karwowski_markoff_myers_spraker_stave_tompkins_weller_et al._2015, title={Polarization asymmetries in the Be-9(gamma, n(0)) reaction}, volume={92}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.92.034604}, abstractNote={Measurements of the $^{9}\mathrm{Be}(\ensuremath{\gamma},{n}_{0})$ reaction were performed using nearly 100% linearly polarized, high-intensity, and nearly monoenergetic $\ensuremath{\gamma}$-ray beams having energies between 5.5 and 15.5 MeV at the High Intensity $\ensuremath{\gamma}$-ray Source located at Duke University and Triangle Universities Nuclear Laboratory. Eighteen liquid scintillator detectors were used to measure neutron yields parallel and perpendicular to the plane of beam polarization. Polarization asymmetries, which are the differences between yields observed in detectors located in-plane and out-of-plane divided by their sums, were measured for the neutrons which left the residual nucleus $(^{8}\mathrm{Be})$ in its ground state, termed the ${n}_{0}$ group. Asymmetries between 0.4 to 0.7 were discovered over this energy region in addition to a clear trend of increasing asymmetries with increasing beam energy. A prediction of the polarization asymmetry based on a pure $E1$ direct capture model shows good agreement with the experimental measurements. These data and the prediction could be of interest for methods that rely on neutron measurements following photofission to identify the presence of special nuclear material.}, number={3}, journal={PHYSICAL REVIEW C}, author={Mueller, J. M. and Ahmed, M. W. and Davis, B. J. and Karwowski, H. J. and Markoff, D. M. and Myers, L. S. and Spraker, M. C. and Stave, S. and Tompkins, J. R. and Weller, H. R. and et al.}, year={2015}, month={Sep} }