This PDF file contains the front matter associated with SPIE Proceedings Volume 11494, including the Title Page, Copyright Information, and Table of Contents.

Transparent, crack-free single crystal boules of 1-inch diameter Cs2HfCl6 (CHC) and Cs2HfCl4Br2 (CHCB) have been successfully grown using the vertical Bridgman method. Samples sized dia. 23mm×30mm and dia. 23mm×26mm, respectively, are characterized for their optical and scintillation properties. Energy resolutions of 3.5% and 3.7% (FWHM) at 662 keV as well as light yields of 23,000 ph/MeV and 20,000 ph/MeV have been calculated for CHC and CHCB, respectively. Results comparable to previously reported smaller crystals have been obtained. Studies on decay times, non-proportionality, and detector characterization are also reported. (This work was supported in part by U.S. Department of Energy under Grant #DE-SC0015733, U.S. National Science Foundation under Grant #HRD-1547757, and by U.S. National Aeronautics and Space Administration under Grant #NNX16AK42G).

A new approach for measuring lifetimes of nuclear states at the electronic signal processing stage has been tested. Cerium doped lanthanum bromide inorganic scintillator crystals are used as suitable candidates for fast-timing measurements, in the sub-nanosecond region. The pulse processing of fast timing detectors has been performed using fast amplifiers together with FPGA (field-programmable gate array) based signal discrimination and time measurement in a 10 ps (rms- root mean square) TDC (time-to-digital convertor). The performance from the timing perspective has been tested in an accelerated ion-beam experiment.

Heavy metal selenides have shown very good properties including wavelength conversion in MWIR and LWIR regions, acousto-optic and great potential for radiation detection. We have extensively studied thallium-based compounds for variety of applications. Studies were performed for crystal growth, fabricability and radiation detection characteristics of ternary congruent compounds of thallium mercury iodide system from the melt by Bridgman method. The congruency and phase transition was studied by DTA. Material melts congruently between 300-400 0C and do not show any other phases between room temperature and melting point. Crystal slabs were fabricated as bulk detector to demonstrate good characteristics for detectivity of X-ray and gamma-rays. Effect of impurities on performance were evaluated by using source materials of different purity for synthesis. Crystals with high purity source materials and mixed by vibrating method were determined for resistivity in range of 1012ohm-cm.

Metal halide perovskites have arisen as a new family of semiconductors for room-temperature ionization radiation detectors due to their high stopping power, large and balanced electron-hole mobility-lifetime (mu-tau) product, and tunable bandgap. These materials are low-cost to make using solution process. The mu-tau of some perovskites are already close or superior to best CZT crystals, while the best resolution of gamma-ray spectrum does not catch up yet, most likely due to the ion migration and self-doping behavior in these materials. Here, we report a simple approach of additive-assisted inverse temperature crystallization (ITC) solution method to grow low-defect density single crystal. We also report our recent progress in developing flexible polycrystalline films for X-ray imaging with performance comparable to those of single crystals while they are much simpler to scale up to commercial relevant size.

Inorganic scintillators containing heavy Thallium-(Tl) in the host lattices are the novel emerging class discovered by our research group. In this class of scintillators, we studied elpasolites, ternary lanthanide halides, ternary metal halides and Tl-based hafnium/zirconium halides. These materials were synthesized by conventional melting, rotating melt direction and sublimation techniques. The single crystals were grown by conventional and modified two zones vertical Bridgman techniques and the phases were analyzed by differential scanning calorimetry and powder X-rays diffraction analysis. The emission properties studied at room temperature under X-rays irradiation shown to have efficient intrinsic and Ce³⁺ or Eu²⁺ dopant luminescence, mostly in the 370-530 nm range i.e compatible with the spectral sensitivity response of modern photosensors. The scintillation properties studied under γ-rays and α-particles irradiation shown to have good energy resolution, high light yield, faster timing response and good pulse shape discrimination. The heavy Tl ion give rise to high effective number and moderate densities to these scintillators, make them efficient for the detection of X- and γ-rays. With the modification of crystal growth furnaces, materials synthesis techniques, and purification procedure the scintillation performance of these scintillators improved significantly. The discovery and development for new Tl-based efficient scintillators and improvement in scintillation performance of the already discovered Tl-based scintillators are under investigation and will be reported in our future work.

Hybrid organic-inorganic perovskite semiconductors represent a promising class of materials for direct conversion X-ray detectors. Due to their processability at low temperatures, perovskite thin films offer the ease of scalable solution-based processing on mechanically flexible substrates, enabling novel device concepts such as lightweight, robust, curved, and folded detectors. In this study, we use digital inkjet printing to realize triple cation perovskite X-ray detectors on mechanically flexible substrates and evaluate the detector performance by the X-ray sensitivity, the dark current, and the X-ray stability. Our results prove the concept of mechanically flexible inkjet-printed triple cation perovskite X-ray detectors for the realization of novel detector designs.

The scope and applicability of detecting gamma-emitting materials by first responders and advanced searchers have changed considerably over the last 15 years. More often than not the searchers are being asked to obtain an image of the gamma sources that are shielded or otherwise inaccessible. They are constantly being tasked to localize a moving source in busy traffic. Commercially available gamma detection units and prototype Government-funded research products use complex techniques such as hybrid imaging processes (combination of traditional Compton imaging with coded aperture masks, for example, modified uniformly redundant array [MURA] patterns). Standalone radiation detection systems are increasingly capitalizing on multi-modal detection, emphasizing on data fusion, informatics, and novel signal/signature exploitations. At the request of the U.S. Department of Homeland Security (DHS) Countering Weapons of Mass Destruction (CWMD) Office, previously known as the Domestic Nuclear Detection Office (DNDO), a study committee from the American Physical Society has recommended that emphasis is kept on the ability to detect shielded special nuclear material with high sensitivity and reliability. Development of new and improved detection algorithms (e.g., principal component analysis, maximum-likelihood estimation algorithm, and others) has been encouraged. CWMD has been urged to focus on signature identification in its nuclear forensic portfolio. Newer materials like SrI₃:Eu²⁺, LaBr₃:Ce, CeBr₃:Ca²⁺ with fast rise time and short decay time of gamma pulses, high intrinsic gamma sensitivity, high gamma energy resolution, and high-efficiency conversion of excitation energy to fluorescent radiation are constantly being sought to build gamma detectors. Neutron detection and associated activation analysis using a gamma ray detection system is highly encouraged. There is a constant demand for miniaturization of gamma radiation detection system for tactical usage in the field– the most sought-after device must be lightweight, easy to use, should be able to withstand harsh environmental conditions, long shelf life with commensurate long battery life, high sensitivity (with preferably high resolution), capable of creating flexible and configurable alarm conditions with directional sensitivity. This array of technical constraints demands stringent specifications on the readout electronics, data acquisition technologies, interoperability and interconnectivity of data output and strict quality assurance of the detection and measurement devices. In recent years the CWMD has developed a system called Intelligent Radiation Sensing System (IRSS) that harnesses the information gathered by ubiquitous radiation monitoring systems deployed by the state, local, and tribal law enforcement organizers [1]. The IRSS was created to better equip law enforcement entities to protect large cities from the threats and harmful effects of nuclear or radiological incidents and emergencies. The IRSS uses a breakthrough technology that networks a group of portable radiation detectors with improved detection, localization, and identification of potential radiological threat. The program created a robust, flexible network architecture along with advanced data fusion algorithms that combine information from many detectors. A study [2] published in the Journal of Materials Research summarized the basic requirements for materials to be used in development of scalable radiation detection systems that considered the critical material performance metrics of energy resolution (1% for semiconductors like CZT, <3% for scintillators like LaBr₃:Ce at 662 keV primary gamma ray energy from ¹³⁷Cs isotope), fast timing including high mobility of electrons and holes in the semiconductors and fast scintillation processes, high spatial resolution for imaging purposes, high intrinsic detection efficiency (requiring high density, high effective atomic number Z_eff), high geometric efficiency achieved sometimes by occlusion processes, neutron detection efficiency and operational factors like cost, ease of use, use of peripheral equipment like thermomechanical engines to stabilize the detection systems. Exciting new research and development work utilizing effective data mining algorithms is being performed at universities, national laboratories, and commercial institutions in gamma ray detection technology. For example, gamma ray imaging techniques first used in space telescopes are being applied in modern security and health systems in a joint project between the University of Southampton and industrial partner Symetrica. The project aims to develop a new coded aperture imaging system that could inspire a new generation of “stand-off” imaging systems. These systems would allow for remote inspection for radioactive materials. This review article intends to capture the synergy of international commercial collaborations exemplified by the United States Defense Advanced Research Projects Agency’s (DARPA’s) SIGMA program in which detector expertise originating from the United Kingdom (Kromek Group plc.) algorithm development and system modelling and analysis developed by United States national laboratories came together under the general guidance provided by a small commercial unit, Invincea Labs, in the area of network algorithm integration and development.

This paper presents the experimental results for a pixel detector device fabricated with 3.0-μm-diameter gold cone bump connections. The process integrity was checked for a test element group of a stacked heterogeneous X-ray sensor with gold cylindrical bumps.

Aerial radiological search and survey missions have been performed by the United States Department of Energy's (USDOE) Remote Sensing Laboratory for over 40 years. Originally created in 1967 as Aerial Measurement Operations, the Aerial Measuring System (AMS) mission has expanded to include acquiring baseline measurements, performing periodic site monitoring, and responding to radiological emergencies. In an accident scenario, AMS fixedwing and/or rotary-wing systems can be deployed to map radiological deposition. The aircraft are equipped to detect and measure radioactive contamination on the ground. The AMS has a sophisticated radiation detection system to gather radiological information and store it on the cloud using the Advanced Visualization and Integration of Data (AVID) platform or on local computers. This large amount of radiation monitoring data is later used to define and implement public protective guidance. Aerial radiation measurements have proven to be very effective in support of responses to nuclear or radiological emergencies resulting in the dispersal of radioactive material over a large area [viz. Fukushima Daiichi Nuclear power plant measurements done through March and April 2011] [1]. Right after the Fukushima accident, US aerial missions flew 85 flights over 500 hours, covering more than 10,000 square kilometres from the power plant to an 80 km radius to create a common operating picture of the extent of the gamma-emitting radionuclides and the footprint of the deposition from multiple releases. In order to be effective, the aerial measurements must be performed with a system that will collect the data in sufficient detail and quality to support the needs of emergency responders. This paper briefly outlines the technical specifications and functions of a system to be used on an aerial platform (airplane or helicopter) to measure widespread radioactive material (radioactive contamination). The information contained within this paper is intended to help ensure that measurements conducted by multiple AMSs are both technically compatible and comparable with each other and with measurements taken on the ground. Recently AMS has acquired newer and faster aircraft with longer-than-before ranges to deploy radiation monitoring equipment. This article defines and provides guidance for using the US DOE/NNSA’s new aerial measurement platforms with multi-fold return of the investment in mind. The guidance involves technical innovation and optimized use of the platforms and collaboration with other stakeholders like the Department of Homeland Security, the Nuclear Regulatory Commission, and the Environmental Protection Agency. The guidance recommends AMS to reposition itself as a valid and credentialed data provider to other relevant and recognized stakeholders in the area of chemical, biological, radiological, nuclear, and explosives threats. It recommends critical application expansion for AVID to analyse multi-modal data including hyperspectral, infrared, and radiological data through data fusion.

This work presents the characterization and performance of the first 3 mm CdTe sensor connected to a readout chip of the Medipix/Timepix detector family. The integration and parameters of a developed cluster analysis are shown to fully utilize the detector configuration in a gamma camera. Spectroscopic measurements regarding the common radioactive sources 137Caesium, 152Europium and 241Americium are investigated. The absorption efficiency of the 3 mm CdTe sensor is compared to a 0.45 mm CdTe and a 1 mm CdTe detector configuration. The charge sharing effect is successfully reduced with cluster analysis and the thicker sensor profits greatly from the greater absorption efficiency, especially in higher energy ranges (> 100 keV). The information gain of the charge sharing effect regarding cluster size and shape can be further used for identification of the investigated isotopes.

In this work, we investigated x-ray radiation detection capability of β-Ga₂O₃ doped with Fe for minimizing leakage current through Fe n-conductivity compensation. (010) EFG grown Fe-doped β-Ga2O3 was tested as a low-noise X-ray detector with Ti/Au electrodes vertical structure. Its performance at low, high and no applied voltages was examined. The fabricated detector showed high X-ray detection performance manifested in its signal’s short fall and rise time (< 0.3 sec) in all operation modes, and the same temporal response was exhibited by a tested Au/Ni/β-Ga₂O₃/Ti/Au device. The detector’s signal is also characterized by excellent linear relation with X-ray tube power and current and high signal to noise ratio (SNR) optimized at -5 V (> 103). Moreover, the X-ray induced current signal exhibits high stability. Sub-band UV photocurrent signal showed a significantly slower response compared to X-ray induced conductivity signal.

High energy X-rays and neutrons can provide 3-D volumetric views of large objects made of multiple materials. Lenscoupled computed tomography using a scintillator imaged on a CCD camera obtains high spatial resolution, while a surface-mounted segmented scintillator on an amorphous silicon (A-Si) array can provide high throughput. For MeV Xray CT, a new polycrystalline transparent ceramic scintillator referred to as “GLO” offers excellent stopping power and light yield for improved contrast in sizes up to a 12” field-of-view. For MeV neutron CT, we have fabricated both contiguous and segmented plates of “Hi-LY” plastic scintillator, offering light yields 3x higher than standard plastic.

Neutrons and X-rays provide excellent complementary, nondestructive probes to understand internal structure of systems across engineering and material science. With its sensitivity to hydrogen, neutrons excel at separating fluids, such as water or oil, from solid and gas phases in three-phase systems whereas X-rays excel at identifying the solid phase. To fully leverage the complementarity of the two methods, the National Institute of Standards and Technology (NIST) has developed the Neutron and X-ray Tomography (NeXT) system which orients a microfocus X-ray generator orthogonally to a reactor sourced thermal neutron beam. This orientation allows for truly simultaneous acquisition of both modalities so that the multi-modal data sets of samples that are evolving with time or undergoing stochastic processes can be directly correlated. The NeXT system has been available for external researchers since 2015 through the NIST Center for Neutron Research user facility program. Significant efforts have resulted in distributable software packages to facilitate image denoising, tomography reconstruction, volume registration, and bivariate histogram segmentation. This paper will give an overview of the NeXT system, explain the process for bivariate histogram segmentation, and provide several examples of use cases for the system.

In the frame of direct dark matter search, the fast neutrons producing elastic collisions and solar neutrinos by coherent interactions on nuclei are the ultimate background. The MIMAC (MIcro-tpc MAtrix Chambers) project has developed a directional detector providing the directional signature to discriminate them based on 3D nuclear tracks reconstruction. The MIMAC team of the LPSC has adapted one MIMAC chamber as a portable fast neutron spectrometer, the Mimac- FastN detector, having a very large neutron energy range (10 keV – 200 MeV) with different gas mixtures and pressures. The present paper shows its main features and functionality and demonstrates its potential in the energy range from 1 MeV to 15 MeV.

During the dynamic compression of a subcritical object that is simultaneously receiving a neutron pulse, its fission 𝛾-ray signal can be measured and the die-off in its time-response is directly correlated with peak reactivity and neutron multiplication within. Hence, the signal measured by a time-of-flight (TOF) gamma detector array operating in currentmode is a convolution of the incident neutron pulse, detector time response, and fission signal from the object. Accurate determination of the true fission 𝛾-ray emission rate from the object requires a detector that is both highly sensitive (to preserve statistics) and fast (to minimize distortion of the signal shape from the object). In collaboration with scientists at Mission Support and Test Services (MSTS) and the Nevada National Security Site (NNSS), a TOF 𝛾-ray detection system was designed at Los Alamos National Laboratory (LANL) to meet these experimental objectives. This system consists of a 3-m-diameter array of ∼ 150 hexagonal detector pixels, each operating in current mode. Each pixel consists of a large-volume, fast-plastic scintillator coupled to a 5-in photomultiplier tube via a plastic light guide that uses total internal reflection for optical transport to the photocathode. Development details of this pixel design using statistical and time response metrics, laboratory measurements of full pixels and photomultiplier tubes, and high-fidelity GEANT4 simulations, are given. In closing, fielding considerations and expected performance capabilities for the full detector array are also described.

This paper presents the evaluation of an alternative solution for detectors of dual energy x-ray absorptiometry systems. Bone mineral density (BMD) evaluation tools are crucial to the proper diagnosis of osteoporosis. The commercially available DEXA systems utilize CZT as the detector of the small dose of ionizing radiation passing through the area of interest. Our paper presents a novel Strontium Iodide doped with Europium (SrI2:Eu²⁺) scintillator crystal coupled to a Silicon Photomultiplier (SiPM) array as a less expensive alternative to CZT detector. Dual energy (60 keV and 122 keV) exposure was used for BMD measurements of a bone phantoms containing CaHPO₄ to mimic bone and resin to mimic soft tissue. Calibration curves was determined for both BMD and for thickness measurements, validated by “unknown” phantoms. Both calibration curves lead to decreased errors compared to commercially available systems.

The Ohio State University Research Reactor's (OSURR) fast neutron beamline is aimed to meet the growing demand for high flux and well-collimated neutron sources for fast neutron radiography and tomography applications. The beam facility consists of two collimators, separated by a neutron-gamma shutter, and a movable beam stop, sitting on a rail system for back/forth and up/down motion to provide an adjustable working space. The beam facility provides a beam diameter of 3.2-cm and has a calculated geometric L/D ratio of ~62. The collimator closer to reactor core includes a 10.16-cm thick polycrystalline Bismuth for filtering gamma-rays, which provides ~2 orders of magnitude reduction in gamma flux at 2-MeV, and a 15.24-cm thick graphite with a 3.2-cm diameter aperture. Various Monte Carlo N-Particle (MCNP) simulations were performed to obtain neutron energy spectrum, neutron and gamma flux distributions, and dose rate values. Simulations showed a fast neutron (@1.6 MeV) flux ~5.4 × 10⁷ n·cm^-2·s^-1 at the collimator exit. While the simulations of neutron and gamma flux distributions have verified that the beam shutter and beam stop provide a decent neutron and gamma shielding, a neutron radiograph of the beam was experimentally obtained using a Polyvinyl Toluene (PVT) based plastic scintillator and a lens-based imaging setup which has further validated the simulated radiographs of the beam. Simulations also provided neutron dose rates around the beam stop with a close agreement with experimental values. However, disagreements were found between experimental and simulated gamma flux dose rates, which needs further validation.

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.

We report on the fabrication and characterization of a high-resolution Schottky barrier radiation detector for high temperature (HT) applications using high quality 150 𝜇m thick n-4H-SiC epitaxial layers with an ultra-low micropipe density of ≤0.1 cm^-2. To evaluate the depletion region parameters of the detector, it was first characterized temperature- dependent capacitance voltage (C-V-T) measurements which showed barrier heights Φ_𝐵 ranging from 2.09 to 2.24 eV and a carrier concentration of ~2 x 10¹⁴ cm^-3 at room temperature (RT) which linearly increased at a rate of 9.65 x 1010 cm^-3/K. From the depletion region simulation studies, it was shown that the change in doping concentration with temperature (T) can increase the needed bias to fully capture charged particles by up to 9V for ²⁴¹Am and over 30V for a higher energy particles from ²¹³Po. To examine the barrier properties and leakage currents of the detectors, we have systematically characterized temperature-dependent current - voltage measurements (I-V-T). The forward bias characteristics showed two linear regions - a low voltage region corresponding to a Shockley-Read-Hall (SRH) recombination center at 𝐸_𝐶 − 0.93 eV and an upper region which corresponded to the barrier height of 2.02 eV. The reverse bias leakage currents were measured to be ~6 pA at ~65V at 300K implying a high signal to noise ratio (SNR) at RT and exhibited a current of less than 1 nA until 500K suggesting that detector should be operable with high SNR at ~200 ^oC. The Arrhenius plot of the reverse I-V-T showed an activation energy of 0.11 eV up to 400K and then 0.73 eV for 450K to 600K suggesting that most of the excess current at HT is derived from deep level state Z_1/2 recombination center. Deep level transient spectroscopy (DLTS) results showed low defect concentrations of ~1011 cm^-3 confirming that charge loss from trapping is negligible. Density functional theory (DFT) calculations suggested that the measured trap levels corresponded primarily to carbon (C) vacancies while the level at 0.93 eV corresponded to Si vacancies near the surface. The pulse height spectra (PHS) of the detector showed an excellent RT energy resolution of 0.55% FWHM at 5486 keV alpha particles after gaussian correction owed gamma response at 59.54 keV.

We already reported TlBr X-ray imager by using our original designed ROIC “photon and charge counting type ROIC”. The silver bumps were used in this imager device for connecting TlBr and ROIC, and this silver bumps were also behaved as silver electrode on TlBr. It is difficult to operate TlBr radiation detector for long time, and Hitomi et.al. reported that the long-time operation could achieved by switching the bias voltage polar for the detector and/or using thallium (Tl) electrode. In our TlBr imager, we designed the ROIC input circuit using bipolar amplifier. In this paper, we use bias polar switching method for long time operation of TlBr X-ray imager, because it is not easy to adapted photo-lithography process of Tl metal for making pixelized TlBr sensor. We use the silver electrode (as also bumping material), and the device structure was TlPb(common electrode)/TlBr/Ag(pixel electrodes and bump material)/ROIC. We will discuss about long time operations in this imager.

In 2010, light scattering defects were observed in several fielded panels of poly(vinyltoluene) plastic scintillators that had experienced losses in radiation sensitivity. Pacific Northwest National Laboratory first deduced that the defects were caused by trapped water. A subsequent multi-lab team funded by the DHS CWMD office found that the defects were produced when the trapped, supersaturated water caused the plastic matrix to yield. In the following years, using sophisticated optical measurements and chemical synthesis, the team discovered that the degree of light scattering and defect appearance was a function of moisture supersaturation in the plastic, scintillator formulation, and cycling history. This report focuses on the recent technical achievements by the team in 1) further understanding the root causes of the observed sensitivity loss, 2) deploying a computational tool to predict when and at which sites fogging may occur, and 3) developing and characterizing a class of fog-resistant formulations that have been demonstrated at full panel-scale and will serve as replacements for failed and at-risk panels.

Plastic scintillators offer a cost-effective and scalable option for detection of special nuclear materials. Traditional plastic scintillators are based on thermoplastics such as poly(vinyl toluene) (PVT) and polystyrene. When over-doped with select fluorescent molecules, PVT and polystyrene scintillators are capable of distinguishing between neutrons and gamma ray via pulse shape discrimination (PSD). While this formulation has been extensively studied and commercialized, the resulting scintillators are restricted to applications involving rigid thermoplastics. In order to achieve flexible and elastomeric properties, a new class of elastomer scintillators based on polysiloxanes has been explored. This work details elastomeric polysiloxane scintillators based on a commercial resin and a commercial primary dopant, 2,5-diphenyloxazole (PPO) and a synthesized dopant, 9,9-dimethyl-2-phenyl fluorene (PhF). PPO-polysiloxane scintillators showed PSD capabilities surpassing commercial thermoplastic analogues at low concentrations of PPO (FoM 1.33 ± 0.03 at 450 keV_ee for 5wt% PPO). PhF-polysiloxane scintillators were also capable of PSD, comparable to the commercial sample, but notably had a high light yield, of 144% EJ-299-33. This work serves as a proof of concept that polysiloxane scintillators can be capable of good PSD and high light yield at low dopant loadings.

Garnet based scintillators have been shown to have high light yield with fast scintillation decay constants. The availability of high refractive index resin enables the fabrication of translucent garnet based scintillating composites; here, this study investigates optical transport improvements through reducing the refractive index difference between composite constituents. The results of this study will demonstrate radiation response characteristics of garnet based scintillating composites, support hard-radiation imaging applications, basic science and explore optical transport limitations in composite technology.

Here we report X- and gamma-ray scintillation properties from solution-processable perovskite (SPP) halide single crystals and quantum dots. We tune the properties of single crystals by replacing the cation, changing the organic ammonium cation spacer, and varying the halide anion. For quantum dots, we tune the properties by changing the halide ion composition while we also try to replace the lead with the bismuth. Finally, we summarize the advantages and disadvantages of SPP single crystals and quantum dots to pave the way the research for the new high light yield scintillators.

Some novel organic plastic scintillators offer substantial improvements in light-yield, detection efficiency, and pulse-shape discrimination over more traditional plastic materials. One promising application for select organic scintillators is in lowcost, portable, and durable dual-particle imaging (DPI) systems to support nuclear safety, security, and safeguards purposes. All candidate materials should first undergo investigation utilizing industry standards to quantify and evaluate their capabilities. In this work, a 21% bismuth-loaded polyvinyl toluene (BiPVT) fabricated by Lawrence Livermore National Laboratory (LLNL) was computationally and experimentally evaluated as a small, pixelated radiographic array, with individual pixel dimensions of 2×2×19 mm. For comparison, the same evaluations were conducted for two samesized arrays made from EJ-200 and EJ-256. ASTM standard test methods and practices were utilized to calculate the modulation transfer function and basic spatial resolution for each array, both from measured and simulated data. Measurements were recorded by pressure coupling all three arrays to a commercial a-Si digital radiographic panel, and the computational model replicated the experimental design. Computational and experimental results were compared for all three arrays in the x-ray environment, whereas only computational results are available at this time for comparison in a fast neutron environment. The x-ray results demonstrate that BiPVT outperformed nearly identical arrays made from EJ- 200 and EJ-256, and the agreement between the simulated and experimental x-ray results validates the applied computational methodology for comparative predictions of neutron performance. Based on these simulations, the BiPVT array is also expected to outperform arrays made from EJ-200 and EJ-256 in fast neutron environments. These findings suggest that DPI systems utilizing BiPVT hold promise over more traditional material alternatives for continued development.

Diamond photoconductive detectors have been shown to detect fast neutrons with high gamma insensitivity. Depending on the application and the incident neutron energy, there are many possible choices when considering how diamond elements may be sized, arranged, and instrumented. As part of our design effort, we are using Geant4 and MCNP6.2 to simulate the effects of fast neutrons impinging on diamond detectors ranging in thickness from a few microns to a few hundred microns that are 4 mm on a side with intervening materials and other physical parameters. The models may be used to compare diamond detector measurements with incident neutrons ranging from ~1 to 14.1 MeV to better understand the nuclear and atomic physics effects contributing to an electronic signal. We are investigating pulse height, signal-to-noise ratio, and timing characteristics of prototype single-crystal chemical vapor deposition diamond detectors.

Peculiarities of morphology and electric properties of X-ray and γ-ray detectors developed by graphene deposition onto commercially available (111) oriented CdTe:Cl wafers has been investigated. Laser treatment of graphene contact using millisecond YAG-laser with an energy density of 0.1–4.5 J/cm² has been carried out in order to modify and improve their structure and phase state.

The electrical and detection properties of the X/γ-ray detectors, fabricated as Cr/CdTe/Au diode structures using semiinsulating p-CdTe single crystals with different concentrations of uncompensated impurities (N ~ 4 × 10¹⁰ cm^-3, 1 × 10¹¹ cm^-3, 2 × 10¹¹ cm^-3 and 2 × 10¹² cm^-3), which determines the width of the space-charge region (SCR), were studied. All the diode-structured detectors were fabricated by the same elaborated technique with vacuum deposition of a Cr electrode (rectifying Schottky contact) and Au electrode (near Ohmic contact) onto the B- and A-face of CdTe(111) crystals pre-treated with Ar-ion bombardment. The dark I-V characteristics of the Cr/CdTe/Au Schottky diodes evidenced steep rectification properties that allowed applying high reverse bias voltage (V = 1-1.5 kV) under moderately low dark currents (I = 3-10 nA at rectifying contact area of 10 mm² and T = 300 K). The charge transport mechanisms in the Schottky diodes were analyzed and attributed to generation currents in the SCR at V < 100 V, charge transport in the conditions when the SCR width exceeded the crystal thickness at elevated V, and currents limited by space charge at higher V. The as Cr/CdTe/Au Schottky-diode detectors, fabricated using CdTe with N ≤ 5×10¹⁰ cm^-3, demonstrated the highest detection efficiency and energy resolution (0.6-1.0 %@662 keV). With increasing N, these characteristics deteriorated. Dependences of detection efficiency on N were calculated for different applied bias voltages V.

The depth correction method based on cathode to anode signal ratios requires at least two readout electronics for obtaining both cathode and anode signals. In this study, pulse waveform analysis techniques for anode signals, in which only one readout channel is requisite, were applied to capacitive Frisch grid TlBr detectors. A capacitive Frisch grid TlBr detector exhibited an energy resolution of 1.92% FWHM for 662-keV gamma rays without correction. Waveform classification based on 20% to 80% pulse rise time was performed for the anode signals. The energy resolution was improved to be 1.70% FWHM with rise time correction.

Dual-energy CT (DECT) system can provide beneficial CT maps for inspection. To improve material discrimination capability, rich energy information is needed. Moreover, simple equipment is good for generalize DECT system. In this study, we proposed multi energy spectral CT imaging method by a general x-ray tube and a general CdTe energy integrating type flat panel detector (FPD). In the proposed method, x-ray incident to a side of FPD to acquire various energetically distinct datasets. CT images which applied image domain and projection domain subtraction methods were evaluated.

We have developed p-n junction CdTe diodes using the laser doping technology for fabrication of more advanced X/gamma-ray detectors. Using backside laser irradiation, it was expected that the laser intensity and number of irradiation shots could be easily regulated to control the charge carrier concentration in a doped CdTe layer. We have used Nd: YAG laser radiation (1064 nm) for which CdTe is transparent. The I-V characteristics and isotope spectra of the produced structures have confirmed expected diode formation of p-n junction CdTe diodes for X gamma-ray detectors.

This work present a compact, lightweight, low power consumption, a proposal cosmic ray detector based on Silicon photomultipliers (SiPM) and plastic scintillator optimized for use as a payload in standard cubesat systems for suborbital or orbital flights. This instrument use a reconfigurable architecture design for on-board processing of command and handling subsystem using COTS SoCs. Therefore detector is to use a field programmable gate array (FPGA), it is so the detector is designed using Xilinx device ZynQ SoC.

Epitaxial layers and complex heterostructures on the base of the CdTe and Cd1-xMnxTe crystals were obtained by pulsed laser irradiation both in their transparency and absorption regions. Structural perfection of the laser-epitaxial layers, transition regions and distribution of the Te and Cd inclusions in the area of the laser action were studied. Analysis of the U-V and C-V characteristics of the obtained structures indicates a decrease in influence of surface states at the hetero-boundaries as a result of laser treatment in optimal mode, and also a reduction of reverse dark current and loss current. The spectral characteristics of the laser-epitaxial structures on the base of CdTe and Cd1-xMnxTe show, that they are promising materials for X- and gamma-radiation detectors.

Cd_xZn_1-xTe_1-ySe_y (CZTS) is an emerging wide bandgap semiconductor material for the applications of high-resolution room-temperature x-ray and gamma-ray detectors. Large volume Cd_0.9Zn_0.1Te1_-ySe_y single crystal ingots were grown by vertical Bridgman technique with composition 𝑦 = 0.02, 0.03, 0.05, and 0.07. Several planar detectors were fabricated on single grain cut out from the grown ingots and characterized. Current-voltage (I-V) measurements revealed very low leakage current (≤ 1 nA) at an operating bias voltage of ≥ 100 V and a bulk resistivity of ~10¹⁰ Ω-cm. X-ray diffraction (XRD) results showed sharp diffraction peaks, which confirmed a highly crystalline structure of the grown crystals. Energy dispersive x-ray spectroscopy (EDX) showed uniform elemental distribution over a large area and confirmed the stoichiometry of the samples. While all the detectors showed response to alpha particles, the detector with composition 𝑦 = 0.03 showed very good ¹³⁷Cs (662 keV) gamma response. The drift mobility and mobility-lifetime product in all the samples of those compositions were calculated for both electrons and holes. Pulse height spectroscopy using ¹³⁷Cs on the fabricated detectors showed fully resolved 662 keV gamma peaks with an energy resolution of ~2%. A one-to-one correlation between the space charge limited current (SCLC) flow and radiation detection properties was found to exist in these crystals. An anomalous current flow mechanism, falling outside the comprehension of SCLC flow mechanism, has been observed in the rest of the samples. The anomalous behavior has been attributed to the presence of electron traps.