This PDF file contains the front matter associated with SPIE Proceedings Volume 11114, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists

Recent developments in radiation detection and imaging in combination with the enormous advances in sensing technologies and associated data processing capabilities enable unprecedented ways to detect, map, and visualize radiation relevant for radiation safety and nuclear security and safeguards, surveillance, emergency response, consequence management, decommissioning, and remediation. We have developed a new concept called 3-D Scene Data Fusion that enables to map scenes in three dimensions and fuse this scene data with nuclear radiation data in near real time while the instrument is freely moving through the scene, independently of the deployment platform and independently of the radiation detection or imaging concept. We have demonstrated this concept in a range of configurations on unmanned and manned aerial and ground-based platforms. It not only provides new means in the detection, mapping, and visualization of radiological and nuclear materials relevant for operators and experts but also in the communication with the public.

Two-step annealing (i.e. first in Cd vapor and second in Te vapor) is essential process for obtaining high quality CdZnTe (CZT) materials. During the post-growth two-step annealing, main defects in CZT, that is, Te inclusions, were successfully removed while maintaining its resistivities. Additionally, commonly observed nano-scale defects, that is, dislocation and stacking faults in CZT were also disappeared. A Frisch-grid CZT detector made via the two-step annealing process exhibited improved energy resolution and low backscattering counts in Cs-137 gamma spectra. In this presentation, we will present the evolution of nano-scale defects in annealing process through in-situ transmission electron microscopy (TEM) measurement.

Photon detection is a key factor to study many physical processes in several areas of fundamental physics research as well as industrial application (i.e. medical equipment, environmental measurement equipment, quantum computing and oil well logging). Focusing the attention on photodetectors for particle astrophysics, we understand that we are very close to new discoveries and new results. In order to push the progress in the study of very high-energy or extremely rare phenomena (e.g. dark matter, proton decay, neutrinos from astrophysical sources) the current and future experiments require additional improvements in linearity, gain, quantum efficiency and single photon counting capability. To meet the requirements of these classes of experiments, we propose a new design for a modern hybrid photodetector: the VSiPMT (Vacuum Silicon PhotoMultiplier Tube). The idea is to replace the classical dynode chain of a PMT with a SiPM, which therefore acts as a single stage Geiger electron detector and amplifier, without statistical fluctuations. The aim is to match the large sensitive area of a photocathode with the performances of the SiPM technology. The previous VSiPMT prototypes already showed many attractive features such as low power consumption, very large dynamic range, excellent photon counting capability and low voltage driven gain. We now present the results of the full characterization of the latest and largest version achieved up to now, a 2-inches VSiPMT manufactured by Hamamatsu.

This paper will focus on next-generation inorganic scintillation detectors that could be used to study neutral emission from the high-energy Sun. Recent developments in detector technology have yielded candidate materials for future heliophysics missions, namely elpasolites (Cs2LiYCl6:Ce – CLYC and Cs2LiLaBr6:Ce – CLLB). At a modest cost, these detectors yield superior spectroscopic performance compared to previously used materials (NaI:Tl and CsI:Tl). Additionally, elpasolites can detect and measure thermal to fast (<10 MeV) neutrons, simultaneously with γ rays. In the following sections, we discuss: the importance for measuring neutral emission from the Sun, laboratory performance of candidate scintillators and novel light readout devices, a proposed instrument concept, and the expected response to a γ-ray line-producing and neutron-producing solar flares from the vantage points of 1 AU, 0.3 AU, and 0.04 AU.

The development of efficient, robust plastic scintillators with pulse shape discrimination (PSD) has been of much interest in recent years. As is the case with many new technologies, initial formulations for PSD plastics provided new capabilities that have required in-depth research to refine. Herein we describe continued results from extensive optimization studies that have led to the development of PSD plastics with improved scintillation performance and physical properties. Improvements in the formulation for PSD plastics provide a groundwork from which element-loaded PSD plastics can be further advanced. Two separate approaches for incorporating lithium compounds into plastic scintillators are explored based on the identity of the lithium salt used. Aliphatic and aromatic lithium compounds require different methods of incorporation, resulting in different mechanisms of light quenching and reduction in PSD. These quenching mechanisms are explored and discussed for each type of lithium salt. Since at large size physical and scintillation characteristics are much more sensitive to preparation conditions, performance characterization of scaled plastics is described and compared among different formulations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

The efficient and accurate detection of neutrons is essential in many instruments developed for nuclear nonproliferation and safeguards applications. Recent advances in silicon photomultiplier (SiPM) technology and new organic scintillator materials have made it possible to develop new capabilities for neutron detection that have the potential to improve the current systems used in the field. Areas of application include multiplicity counters for fast neutrons emitted by spontaneous and induce fission in the actinides, and imaging systems used for detecting, locating, and characterizing fission sources. Our group has shown the ability of SiPMs to be used as a replacement for traditional photomultiplier tubes to achieve better timing while retaining pulse shape discrimination capabilities (i.e., the ability to distinguish neutroninduced pulses from gamma ray-induced pulses) for stilbene detectors. In this work, we show the application of arrays of organic fast neutron detectors for multiplicity, imaging, and other applications.

ASTRI-Horn is a prototypal telescope of an imaging atmospheric Cherenkov telescope developed by the Italian National Institute of Astrophysics (INAF), proposed for the Cherenkov Telescope Array (CTA) Observatory. The CTA Observatory represents the next generation of imaging atmospheric Cherenkov telescopes and will explore the very highenergy domain from a few tens of GeV up to few hundreds of TeV. It will be composed of large-, medium-, and small sized telescopes; ASTRI-Horn is an end-to-end prototype proposed for the Small Sized array.

The main scientific instrument of the ASTRI-Horn telescope is an innovative and compact Camera with Silicon- Photomultiplier based detectors and a specifically designed fast read-out electronics based on a custom peak-detector mode. The thermo-mechanical assembly is designed to host both the entire electronics chain, from the sensors to the raw data transmission system and the calibration system, and the complete thermoregulation system.

This contribution gives a high level description of the T/M and electrical design of the Cherenkov Camera, it describes the assembling procedure of its different subsystems and their integration into the complete camera system. A discussion about possible design improvements coming from the problems/difficulties encountered during assembly is also presented. Finally, results from engineering tests conducted in-field are also presented.

Inexpensive spectroscopic personal radiation detectors (SPRDs) are needed to monitor environmental radioactivity and search for sources. For gamma spectroscopy, excellent light yield, material uniformity, light yield proportionality, mechanical and environmental ruggedness can be achieved in polycrystalline ceramic oxide garnets. We are building a compact detector based on 14 cm3 of transparent ceramic garnet, formed into 256 pixels (3mm x 3mm x 6mm each) and mounted on two stacked silicon photodiode arrays. GYGAG(Ce) garnet transparent ceramics offer density = 5.8g/cm3, Zeff = 48, principal decay of <100 ns, and light yield of 50,000 Ph/MeV. We obtain R(662 keV) <4% for the full device, including Compton summing of coincident events in multiple pixels. In addition to excellent gamma spectroscopy, this device provides directional detection, via Compton imaging and active masking, for search applications. This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. We are grateful to Digirad for supporting our implementation of their photodiode array. Thanks to the US Department of Homeland Security, DNDO and CWMD offices, for funding under competitively awarded IAAs HSHQDC-12-X-00149 and HSHQDN-17-X-00016.

Plastic scintillators are in wide use in radiation portal monitors because of their low cost and availability in large sizes. However, due to their low density and atomic number (Z), they offer low intrinsic efficiency and little to no spectroscopic information. The addition of high-Z constituents to these plastics can greatly increase both their total stopping power and the amount of photo-electric absorption, leading to full-energy deposition and thus spectroscopic information in plastics. In this work, we present the performance of the largest bismuth-loaded plastics to date, showing useful spectroscopic information up to relatively high energy (~1 MeV) and their high stopping power compared the current commercially available plastics. These Bi-loaded plastics are based on 20 wt% Bi-pivalate (8 wt% elemental Bi) dissolved in a polyvinytoluene (PVT) matrix and conventional fast fluors (<10 ns decay time). A comparison of performance between slab and cylindrical plastics of similar volumes is presented and large performance improvements (greater than 9 times the sensitivity to 241Am) are shown when used as a drop-in replacement to conventional PVT based portal monitors. This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, and has been supported by the US DOE, Office of NNSA, NA-22.LLNL-ABS-767130.

The first prototype of the Schwarzschild Couder Medium Size Telescope (pSCT) proposed for the CTA observatory has been installed in 2018 at the Fred Lawrence Whipple Observatory. The pSCT camera is composed of 25 modules with 64 channels each, covering only a small portion of the full focal plane of the telescope. The Italian Institute of Nuclear Physics (INFN) has developed and characterized in collaboration with Fondazione Bruno Kessler (FBK) a new generation of Silicon Photomultipliers (SiPMs) sensitive to the Near Ultraviolet wavelengths, based on the High Density technology (NUV-HD devices). The latest generation of 6×6 mm² SiPMs (called NUV-HD3) have been used to equip a subsection of 9 out of 25 modules of the pSCT camera. An upgrade of this camera is foreseen between 2019 and 2020 using the same sensors, aiming to equip the full focal plane with 177 modules, for a total of more than 11000 pixels. We will present a full characterization of the performance of these devices, highlighting why they are suitable for Cherenkov light detection. An overview on the overall behavior of the installed sensors will be also given, providing information on the uniformity of the sensors and of the performance of the camera.

Radiation Portal Monitors (RPMs) based on polyvinyl toluene (PVT) scintillators have been in use since the 1970s. Recently it has been discovered that under certain conditions PVT scintillators can fog at low temperatures. In collaboration with researchers at national laboratories, Eljen Technology has developed methods for the production of Intrinsic Anti-Fogging Scintillators. The production methods have been scaled up to allow for castings of rods and large sheets of scintillators that are deployable in RPMs and other extreme locations. The work is ongoing. The presentation will focus on the properties of the new scintillators and on the ongoing testing results from exposure to extreme environmental conditions.

PROSPECT is a reactor antineutrino experiment whose primary goals are to search for short-baseline neutrino oscillations and perform a precise measurement of the U-235 reactor antineutrino energy spectrum. Since March 2018, PROSPECT has operated a 4 ton antineutrino detector less than 10m from the 85MW High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory. Operating in this environment with tight space constraints and limited overburden to attenuate cosmic ray backgrounds is a significant technical challenge. The PROSPECT detector design uses efficient optical segmentation and a ⁶Li doped liquid scintillator with good light yield and pulse-shape discrimination properties to achieve excellent energy reconstruction and background rejection in a compact, space efficient system. Initial results from PROSPECT have demonstrated the ability to detect 100s of antineutrino events per day with good signal-to-background in this aboveground location and perform precise measurements of the HFIR antineutrino energy spectrum.

One of solutions to develop an energy resolved X-ray imager with sub-100μm pixel pitch is introduced. It consists of a small readout circuit and a data compressor in pixel. To realize spectroscopic readout circuit, charge counting architecture is adopted. And it equips time independence by removing transient response in analog signal processing and detector independence by controllability of time of signal processing for one pulse. An LSI implementing this system has been developed with 0.18um CMOS process. The pixel pitch is 80um and each pixel has 15 energy thresholds. The behavior of readout X-ray photon’s energy and data compression for photon-counting imaging has been verified by using CdTe detector. Furthermore, supporting other detectors such as TlBr and other energy weighting function than photon-counting are progressing.

The description of xenon gamma-ray spectrometers is presented. These devices can be produced with various sensitive volumes (0.2 – 6.0 liters), they provide high energy resolution (~2% at 662 keV) and are capable of operation in unfavorable conditions (wide temperature range and high level of vibro-acoustic influence). Xenon gamma-ray spectrometers can be used for various fundamental and applied tasks, the outcomes of those applications and the prospect of the detector utilization in various fields are also presented.

One of the pressing demands in our western society is the safety and maintenance of our nuclear legacy. In Germany the dismantling, safe processing and storage of nuclear waste have resulted in a multi-national research program. One of the findings was that nondestructive testing methods and material selective imaging of compound large objects is possible using thermal and fast neutrons. They also identified that a powerful, safe, and compact neutron source would be required. Since the advent of ultra-intense lasers many applications have been investigated using the unique parameter of laser-driven secondary sources. Recently, we have demonstrated the realization of a short-pulse laser- driven neutron source with beam intensities orders of magnitude above earlier attempts. Those sources can lead to a compact and potentially mobile neutron source with a large number of applications. The neutron source is based on a so-called pitcher-catcher approach, where a short burst of energetic, laser-driven deuteron ions are converted into a short pulse of neutrons in a subsequent converter material. Here, in addition to neutron conversion via (d,n) reactions the breakup of energetic deuterons and a non-thermal pre-compound reaction in the converter material result in a directed beam of neutrons and an increase in neutron numbers compared to earlier attempts. The neutron record number so far were produced using high-contrast, high-energy short pulse lasers of a few hundred femtosecond pulse duration and invoking relativistic transparency in solids as a new ion acceleration mechanism. I will present the underlying mechanism of creating an intense pulsed and highly directed beam of neutrons using ultra-intense lasers and the recent experimental results using laser systems in the US and in Europe. Furthermore, I will focus on a few examples of using such sources for applications that are either important for the security of our countries or will have large economical potential in industrial applications. These range from the remote sensing of illicit nuclear material in cargo to the non-destructive analysis of large civil constructions using compact laser systems. The initial ion pulse that is converted into neutrons is of only a few picosecond duration and thus the neutron burst is generated with sub-nanosecond pulse length. This allows for precise energy resolution of the neutrons using time-of flight techniques. As the ion acceleration is of only a few millimeter in length, replacing ten's to hundred's of meter of conventional acceleration length the source is extremely compact. As the ion beams are extremely intense and do not suffer from space charge deterioration the fast neutron source is capable of point projection imaging with an initial source size of around a millimeter. As the pulse duration is short, high energy resolution can be achieved at a much reduced time-of-flight length offering more compact systems. As future laser systems largely increase not only peak power, but also already offer repetition rates up the kHz applications in research and industry become visible. To fully take advantage of those new sources new detector systems should keep up with enhanced spatial and temporal resolution. Also they need to withstand the unavoidable x-ray flash and electro-magnetic pulse originating from the laser plasma interaction. We have started to explore novel detectors and tested them at high-energy short pulse laser systems for fast and thermal neutron beams.

We have previously made improvements to the longevity of TlBr semiconductor gamma ray detectors by applying electrodes having the mixed semiconductor composition Tl(Cl,Br) via surface treatments in HCl, leading to a significant enhancement to the lifetime of the detectors. In order to examine the electron transport properties more closely, we have monitored the first-derivative of the cathode waveform (being proportional to velocity and number of carriers) as a function of time and the point of the gamma-interaction. The observed decay in this signal, especially at lower voltage, would naturally be interpreted as the usual trapping phenomenon. However, this phenomenon alone is not able to account for the observed waveforms, most dramatically for the case of increasing signal as the electrons approach the anode, for waveforms originating at the cathode. After detailed consideration of alternative explanations, the cathode waveform data has been interpreted in terms of a non-uniform field owing to variation in the resistivity as a function of position. We have interpreted the shape of the decay as a “built-in” resistivity profile and have further verified this interpretation by reversing the sense of the field (which as expected reverses the “sense” of the waveform). We modeled this effect in order to quantitatively deduce the resistivity profile and are currently working to relate the waveform observations to the relative orientation of the crystal growth direction and the applied electrodes.

Schottky barrier radiation detectors have been fabricated on n-type 4H-SiC epitaxial layers (E_g = 3.27 eV at 300 K) grown on low-resistive n-type 4H-SiC bulk substrates. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were carried out, and using a thermionic emission model, Schottky barrier height of ~1.42 eV was obtained. Capacitance mode deep level transient spectroscopy (DLTS) revealed the presence of deep levels along with two shallow level defects related to titanium impurities (Ti(c)) and an unidentified deep electron trap located at 1.42 eV below the conduction band minimum. The concentration of the lifetime killer Z1/2 defect was found to be ~10¹³ cm^-3. A 0.1 μCi ²⁴¹Am radiation source was used to investigate the detector performance including charge collection efficiency (CCE) by pulse height spectroscopy (PHS), and an energy resolution of ~ 0.38% full-width half maxima (FWHM) was observed for alpha particles at ~ 5447 keV. The average diffusion length (L_d) of holes (minority carriers) were calculated to be ~ 13.6 μm using a drift-diffusion model and MATLAB code. An electronic noise analysis of front-end readout electronics in terms of equivalent noise charge revealed that the white series noise due to the detector capacitance has substantial effect on their spectroscopic detection performance.

We present the construction and the test of a generic neutrons detector for fusion experiments : OMEGA and NIF(USA), LMJ and APPOLON (FRANCE). The detector can be also used as a safety device on particle physics accelerator (ESS, Sweeden), Spiral2(France) etc.. . This detector is based on the technology CEA / IRFU MICROMEGAS detector. This diagnostic has been designed to achieve neutron spectroscopy in large γ background. Tests have been performed on the 60 beams, 30 kJ OMEGA laser system at the University of Rochester(LLE), and on LINAC4 accelerator at CERN during last november (Switzerland), and AMANDE(CEA). In Inertial Confinement Fusion experiment on facilities such as Laser MegaJoule (LMJ) in France and the National Ignition Facility (NIF) and OMEGA, LLE Rochester, USA we plan to achieve the ignition of capsules by compression deuterium-tritium (DT) or a deuteriumdeuterium (DD) filled target, and thus initiate a thermonuclear burn wave. In these experiments <ρ.R> may be measured using neutrons output from the imploded capsule, like secondary and tertiary neutrons produced respectively in DD and DT targets. Measurement of these neutrons remains a challenge as the γ-rays and scattered neutrons induced by primary neutronsinteractions on the experimental hardware can blind detectors. The concept is based on the association of a Micromegas detector with a neutron-to-charged particle converter associated to a fast low noise electronics (<800ps). Electrons produced by γ-rays go through the Micromegas with a low ionization probability, making the detector γ-rays insensitive. This low γ sensitivity makes this concept appealing for inertial confinement fusion experiments. The good time resolution of the apparatus allows the reconstruction of neutron energy spectra with the time-of-flight technics. In this Inertial Confinement Fusion experiments, we have to deal with huge flux of neutrons. We present here the fast-front end electronics (rise time<800 ps, gain 40dB, noise<450µVrms) which is able to deals with high flux without saturates, with a good dynamic range (to see neutrons from hundred of KeV to14 MeV and above). The data acquisition system is a digitization system. A digitization system offers more flexibility for on-line or off-line treatments than a TOT device (Time Over Threshold) for example. We present the whole electronic-chain (front-end and digitizers). Cable and connectors are described, as a matter of fact, a special care has been given for EMC effects during the study, in order to be able to deals with the huge electromagnetic pulses caused by the shot. The design and the construction of the Micromegas detector are presented.

TlBr based photon-counting imaging device has been developed by using our photon-charge counting ASIC. TlBr of 0.8mm-thick wafer was used for detector, and it was pixelized as 80um pitch pixel. Tl based electrode was deposited on TlBr surface as common electrode and Ag electrodes were used as pixelized electrode. The ASIC has 32 x 32 pixels with 80um pitch, 16 thresholds, upto 250kcps of count rate by fully digital processing. This ASIC treat generated charge by detector directly, it can be applied CdTe, TlBr and so on. We detected X-ray / gamma-ray signals. We demonstrate X-ray / gamma-ray images taken by this device and discuss with energy discrimination property and so on.

The demand for an alternative to ³He tubes in neutron detectors is growing. Specifically, the increase in challenging requirements for applications in research, industry, safety and homeland security triggered the search for better-suited detectors. Therefore, we developed a high performance, comparatively low-cost and easy to build cold neutron detector prototype (13.6 cm × 13.6 cm active area), employing digital silicon photomultipliers (SiPM) from Philips and a glass scintillator. The optical front end of the detector consists of a GS20 scintillator, enriched in ⁶Li, a light guide, SiPM arrays and an aluminum cap. In order to find the optimal front-end design, a series of Geant4 simulations were performed. In this work, we present a comparison between simulation results and measured validation data, considering the average number of photons detected and the maximum ratio (brightest pixel response divided by the sum of all pixel responses), for multiple design configurations.

Recently we evaluated spectral performance of virtual Frisch-grid (VFG) CdZnTe (CZT) detectors which offer an economical and robust design for high-efficiency detectors for gamma spectroscopy and imaging. We developed and tested several arrays prototypes coupled to a front-end ASIC. Each detector in the array module operates as a mini time-projection chamber offering high energy and position resolution. Previously we reported high-energy resolution of <0.9% FWHM at 662 keV achieved with the individual detectors and the whole arrays. We employ learning algorithms based on extensive detector calibrations to reconstruct positional information and use this information to correct detectors’ response non-uniformities due to the presence of crystal defects and enhance the spectral resolution of the array. In this work, we evaluated the position resolution achievable with virtual Frisch-grid CZT detectors, which is important for making high-resolution imaging instruments. Based on our measurements, we conclude that <100-micron resolution is achievable with these detectors on a small scale. However, it would require very accurate calibrations to ensure such resolution for the entire detector’s volume due to local variations of the electric field. High spectral and position resolution of position-sensitive virtual Frisch-grid CZT detectors make them attractive for a variety of applications including gamma-ray astronomy, medical and industrial imaging, environmental cleanup, nuclear safeguards and security. The arrays consisted of VFG detectors fabricated from 6x6x20 or 5x7x25 mm3 CZT crystals acquired from Redlen, Inc. The detectors have a simple design. Each crystal, furnished with two gold contacts on the top and bottom surfaces (the anode and the cathode) is encapsulated inside the ultra-thin polyester shell for electrical insulation and mechanical protection of the detector as we previously described. The shell tightly envelops the crystal and holds in place two CuBe flat-spring contacts on the cathode and the anode faces. 4.5-mm wide pads, cut from copper adhesive foil, are attached over the shell near the anode side. The detectors were placed vertically on the detector board and gently pressed from the top using the cathode board having the decoupling capacitors and resistors. The anode spring contacts touch the designated anode pads on the board, while the charge-sensing pads were soldered to the board contacts. The signals generated by the incident photons on the anodes, cathodes and 4 position-sensing pads were routed to the corresponding front ASIC inputs (charge-sensitive preamplifiers). The decoupling circuitries are required for reading the signals from cathodes, which were biased at 2500-3000 V. The ASIC used in these measurements allowed us to capture the signals from individual cathodes, anodes and pads. To calculate the normalized X and Y coordinates, we used the center of gravity method. For the Z coordinate we used the C/A ratio. As we described it previously, this approximation is sufficient to for correcting the response non-uniformity. The measured XYZ values constitute a configuration space, which correlates to the spatial variations in the measured anode signals. Thus, by segmenting the XYZ space into small voxels we sort out the signals corresponding to each of them and apply correction accordingly using a 3-dimensional correction matrix (CM) generated during calibration. For comparison purposes, we also apply drift-time corrections, along the Z direction, which are called 1D correction. The detectors calibration was done for several temperatures and using several gamma ray lines. For calibration we collected the pulse-height spectra from known gamma ray sources and use them to evaluate the channels’ baselines, gains and the 3D correction matrixes for each detector.

We present a dual experimental and computational studies on ruthenium (Ru) induced point defects in wide bandgap semiconductor 4H-silicon carbide (4H-SiC) which is of high interest in alpha, x-ray, and low energy gamma spectroscopy due to Ru’s high weighted metal work function of 4.76 eV which forms a high barrier Schottky contact with low leakage current. We first measured the activation energies and concentrations of deep levels in RF sputtered Ru/n-4H-SiC Schottky diodes annealed at 950°C using deep level transient spectroscopy (DLTS) and identified two deep level defects at E_c – (0.89 ± 0.03) eV and E_c - (1.98 ± 0.03) eV which appear unique to Schottky diodes with Ru. In order to correlate these defects theoretically, we then calculated the formation energies and transition levels of Ru induced point defects in 4H-SiC at charge states [-2, 2] for substitutions and [-2,+4] for interstitials using the projector augmented wave method (PAW) with both PBE and hybrid pseudopotentials on a 3 x 3 x 1 supercell. We found two transition levels which correlate very well with our experimental DLTS results. The transition (-1/0) for Ru substituted into the cubic silicon site at Ev + 2.39 eV and the transition (-1/0) for Ru placed in interstitial site with tetrahedral symmetry to carbon at E_v + 1.23 eV respectively.

Identifying particles that interact in materials that exhibit pulse-shape discrimination (PSD) is a statistical classifier problem. The field of statistical classifiers provides a toolkit of elements and principles that PSD can employ and re-use regardless of the detector material and read-out. Journals have published a myriad of PSD papers over the decades featuring useful components and concepts for implementing and/or improving particle identification. This paper categorizes and assembles PSD methods into one consistent taxonomy. Among the essential elements to consider when building a classifier, one encounters features, pre-processed and reduced features, labels, contamination, coverage, the model, the classifier, optimization and performance metrics, training, testing, scoring, performance trade curves, and thresholding.

In high energy physics (HEP) and nuclear physics experiments, total absorption electromagnetic calorimeters (ECAL) made of inorganic crystals are known for their superb energy resolution and detection efficiency for photon and electron measurements. A crystal ECAL is thus the choice for those experiments where precision measurements of photons and electrons are crucial for their physics missions. A crucial issue for crystal detectors to be used in future HEP experiments at the energy and intensity frontiers is radiation damage by ionization dose as well as charged and neutral hadrons. This paper reports recent investigations on hadron-induced radiation damage in various crystal scintillators. Irradiations up 4 ×1015 /cm2 fluence were carried out at the Weapons Neutron Research facility of Los Alamos Neutron Science Center. Results of these investigations show excellent radiation hardness of bright and fast LYSO and BaF2 crystals which may provide a stable detector in an extreme harsh radiation environment, such as the proposed HL-LHC.

Often only a single physical process or component is investigated in the simulation of radiation detector systems. The results are then considered to be representative of what is expected in the correlating physical experiment. Although singular assessments may serve as a good estimate, the overall performance of a radiation detector system depends on several physical processes and the performance of all components within the system. Our Geant4-based multiphysics simulation toolkit couples radiation transport with optical photon processes, providing simulations of radiation detector systems components from the scintillator through the photocathode of the photodetector. Work to incorporate the backend detector components, including the complete photodetector and subsequent electronics (e.g., amplifiers, digitizers), is underway. Geant4 is used to model the radiation transport and optical photon processes that occur in the front-end detector system components when exposed to a chosen source. These components include the scintillator, detector housing, optical coupling to the photodetector, and photocathode of the photodetector. Characteristics of several detector systems that have been studied include time response; pulse height spectra; number of photoelectrons per MeV; detector efficiency versus incident quanta energy; and effects on detector response due to change in geometries, materials, and reflectivity. Comparison of these characteristics by means of this toolkit enables the selection of the optimal individual components; thus, it is possible to specify the radiation detector system best suited to meet the requirements of any physical experiment.

The LANL neutron imaging and fabrication teams completed the fabrication and inspection of the neutron imaging aperture for the National Ignition Facility (NIF) prior to first use in December 2018. The 16 layer aperture contains an array of 87 openings, manufactured by scribing 100 profiles along 20-cm lengths of thin gold foils. The openings consist of 15 penumbral and 72 triangular apertures. The 16 layers are then assembled into a single 15-mm x 16.6-mm x 200- mm component. Images produced from the array of apertures must be deconvolved in order to remove distortions caused by the extended length of the aperture. In order to deconvolve the image, the as-built aperture profile must first be characterized by measuring the scribed apertures at multiple places along their length. Equipment used for inspections included a white-light interferometer, a confocal laser scanner, and an optical coordinate measuring machine. Both sides of each layer were individually inspected, using complementary and overlapping capabilities in order to overcome the aspect ratio and feature size challenges. The result was a three dimensional, as-built model with the interior layer inspection detail overlaid to create a complete as-built model of the aperture array. This paper provides an overview of the purpose of the aperture array and a detailed discussion of the aperture inspection strategies, technology processes and challenges.

Characterization data for the Icarus 2 hybrid-CMOS (hCMOS) imager using near-infrared (NIR) laser pulses is presented. The Icarus 2 hCMOS imagers are four-frame burst mode cameras, with a 1024 x 512 pixel array and 25μm spatial resolution. Designed and built by Sandia National Laboratory for the Ultra-Fast X-ray Imager (UXI) program where they have been used to capture X-ray images at LLNL’s National Ignition Facility and during HED physics experiments. Temporal and spatial characterization is performed using NIR, 1053nm and 1064nm, laser pulses ranging from 43-ps to 20ns. Specific results include gate response, internal reflections, off-gate sensitivity, side-to-side timing skew, and response to a characteristic NIF-like laser pulse. Comparisons between a commercial gated, intensified CCD camera and a commercial time-integrated CMOS camera are included when relevant.

The multi-channel Kirkpatrick-Baez microscope (KBM), currently in use at the National Ignition Facility (NIF), uses grazing incidence multilayer crystals to focus x-rays to form an image. This diagnostic produces four images with a ~11x magnification, with a designed energy response of 10.2 ±1.5 keV at <10 μm resolution over a 300 μm x 300 μm field of view. The KBM has been designed to image the imploded core of inertial confinement fusion (ICF) experiments, which have diameters ranging over 50-100 μm and broadband emission. The self-emission spectrum is broadband and peaked at ~10 keV.

We present a new calibration of the KBM using a molybdenum (W, Z = 42) x-ray microfocus source to measure the spectral response of the instrument over its field of view. Our results measure the variation and dependence on the coalignment of the four imaging channels, relating the region of best resolution and optimal spectral response.

Lawrence Livermore’s National Ignition Facility (NIF) requires a radiation tolerant video camera to remotely monitor varied activities in and around the NIF target chamber. Our present suite of monitor cameras must be either, removed during high yield shots, requiring substantial resources or left in place which greatly reduces their life expectancy. Our goal was to develop a relatively inexpensive, radiation tolerant monitor camera which could be left in place during high yield laser experiments yet continue to give quality data for up to (5) years of operation or about 250 high yield shots. The camera was built around the CMOSIS CMV 2000 / 4000 sensor. Camera components were chosen based on their radiation tolerant performance at the Cobham radiation test facility in CO Springs. The prototype camera was tested both at Cobham and on the NIF during high yield shots. We will present test results as well as predictions for camera life expectancy.

At the National-Ignition-Facility (NIF) and other laser facilities, X-ray transmission photocathodes are used in streak cameras and pulse-dilation framing cameras with temporal resolution well below 100 ps. For X-ray imaging quality assurance, signal-to-noise ratios of at least a couple, and optimally higher, have to be achieved. The signal-to-noise ratio depends on the photon influence and the Detective Quantum Efficiency (DQE). X-ray photocathodes are notoriously noisy, since they have large pulse height distributions, and their DQE is both material and photon-energy dependent. Furthermore, for high temporal resolution, in pulse dilation instruments space charge effects may further limit the achievable signal-to-noise ratio. Here, we look into details on what to consider when choosing photocathode materials to optimize the achievable signal-to-noise and touch on further potential improvements using structured photocathodes.

Fiber optics are an integral part of data collection, often used to transport visible and UV light to streaked spectrometers and photodetectors. Precisely measuring fiber-optic time delay (FOTD) is necessary for absolute data timing or fiber replacement. An optical time domain reflectometer (OTDR) can be used to measure the fiber-optic time delay. Commercial OTDR’s measure only the fiber in telecommunications wavelengths in the IR. To measure fibers at relevant wavelengths for inertial confinement fusion experiments, a solution using a free-space image relay was devised at the University of Rochester’s Laboratory for Laser Energetics (LLE), where readily available equipment has been used to measure the FOTD to within 2 ps at 526.5 nm as well as 351 nm, which is an order of magnitude better than the timing jitter between LLE’s Hardware Timing System and second-harmonic (526.5-nm) fiducial laser pulses.

The National Ignition Facility’s (NIF) high-yield DT shots create a harsh radiation environment that can cause electronics to malfunction. This paper documents various design tradeoffs and techniques used for a Microsemi FPGA to reduce the impact of Single Event Upsets (SEUs) that enable a camera to capture images in the NIF target chamber during a high-yield shot.

We present the construction and the test of a generic neutrons detector for fusion experiment : OMEGA and NIF(USA) LMJ and APPOLON (France), usable also on particle physics accelerators such as ESS(Sweden), SPIRAL2(France), Berkley (USA) and for magnetic fusion facilities WEST, ITER (France), DIIID(USA). This detector is based on the MICROMEGAS technology detector. This diagnostic has been designed to achieve neutron spectroscopy in large γ background. Tests have been performed on the 60 beams, 30 kJ OMEGA laser system at the University of Rochester(LLE), and on LINAC4 accelerator at CERN (Switzerland), and AMANDE(CEA). In Inertial Confinement Fusion experiment on facilities such as Laser MegaJoule (LMJ) in France and the National Ignition Facility (NIF) in the U.S.we plan to achieve the ignition of capsules by compression deuterium-tritium (DT) or a deuteriumdeuterium (DD) filled target, and thus initiate a thermonuclear burn wave. In these experiments <ρ.R> may be measured using neutrons output from the imploded capsule, like secondary and tertiary neutrons produced respectively in DD and DT targets. Measurement of these neutrons remains a challenge as the γ-rays and scattered neutrons induced by primary neutronsinteractions on the experimental hardware can blind detectors. The concept is based on the association of a Micromegas detector with a neutron-to-charged particle converter associated to a fast low noise electronics (<800ps). A dedicated study has been performed for the neutron to converter particle (ncp) in order to be efficient of few hundred KeV energy neutrons to 14 MeV neutrons. Electrons produced by γ-rays go through the Micromegas with a low ionization probability, making the detector γ-rays insensitive. This low γ sensitivity makes this concept appealing for inertial confinement fusion experiments. The good time resolution of the apparatus allows the reconstruction of neutron energy spectra with the time-of-flight technique. A time-of-flight spectrometer must satisfy a numberof requirements to perform hr:Ri measurement. Main characteristics are the time resolution, the detection efficiency, the dynamic range (The dynamic range is an important characteristic sincethe primary neutron yield can vary from several decades (nowadays on OMEGA Facility to future experiments on LMJ andNIF), but also transparency to different types of background. We present the main characteristics of the detector and the Front-end and Digitizer boards. The data acquisition system is a digitization system. It allows more flexibility foronline or offline treatments and is particularly useful in the prototyping or early phases of the experiments. A special attention has been given to electromagnetic compatibility(EMC) during the design to sustend the huge electromagnetic pulse caused by the shot, shieldings and connectors are described. This diagnostic can also be usefull for particle physics accelerator as safety diagnostic.

We present first results from experimental data showing the capabilities of an Associated Particle Imaging system to measure carbon in soil and other elements. Specifically, we present results from a pre-mixed soil sample containing pure sand (SiO₂) and 4 % carbon by weight. Because the main isotopes of all those three elements emit characteristic high-energy gamma rays following inelastic neutron scattering, it is possible to measure their distribution with our instrument. A 3D resolution of several centimeters in all dimensions has been demonstrated.

To realize novel photon-counting energy-dispersive X-ray computed tomography (CT), we have developed a low-dose CT scanner using a detector consisting of a cerium-doped yttrium aluminum perovskite [YAP(Ce)] crystal and a small photomultiplier tube (PMT). X-ray photons are absorbed by the YAP(Ce) crystal, and negative outputs are produced from the PMT. The PMT outputs are amplified by an inverse voltage-to-voltage amplifier, and the event pulses are counted by the counter with a low threshold energy of 20 keV. First, almost all the photons are counted without the photon-energy dependence, since the scintillation-photon number produced by one X-ray photon is proportional to the photon energy. Second, the energy-dispersive imaging is performed using the self-beam hardening by the object. The maximum photon count of the projection data is determined after the air absorption, and the effective photon energy increases with increasing digital-amplification factor at the constant maximum count. In the triple-energy CT, the X-ray beam diameter was 0.5 mm, and the spatial resolutions were approximately 0.3×0.3 mm² . The exposure time for DE-CT was 9.8 min at a total rotation angle of 180°.

The linear-plasma flash X-ray generator consists of a high-voltage power supply, a 200-nF high-voltage condenser, a turbomolecular pump, and a demountable flash X-ray tube. In the flash X-ray generator, the condenser is charged up to 50 kV by the power supply, and flash X-rays are then produced by the vacuum discharging. The X-ray tube is a demountable triode with a rod-shaped nickel (Ni) target and a Ni reflector. The Ni-target evaporation leads to the formation of weakly ionized linear plasma, consisting of Ni ions and electrons, around the target. In the plasma, K-series characteristic X-ray photons (K photons) are produced, and bremsstrahlung photons with energies beyond the Ni-K-edge energy are absorbed by the plasma and converted into Ni-K photons. Subsequently, Ni-K photons from the Ni reflector easily penetrate the linear Ni plasma. Thus, intense Ni-K photons (rays) are irradiated from the plasma axial direction by K-ray amplification by spontaneous emission of radiation (KASER).

From the experience during radiation monitoring and data analysis of Fukushima Dai-ichi Accident it was learned that the large amount of data gathered during the nuclear emergency by multi-national organizations needs to be harmonized to speak in “one voice” regarding the evolving radiological status of the environment around the accident location. The International Atomic Energy Agency (IAEA)’s Incident and Emergency Centre (IEC) has introduced the International Radiological Information Exchange (IRIX) [1], a technical standard developed by the IAEA, in cooperation with experts from Member States and the European Commission (EC), meant to enable the development of interoperable systems and solutions for exchanging emergency information and data between organisations at both national and international levels during a nuclear or radiological emergency. IRIX works as the data format for the International Radiation Monitoring Information System (IRMIS) [2], a client server-based web application that provides users a platform to report and visualize large quantities of radiological monitoring data during nuclear and radiological emergencies. IRMIS routinely receives the radiation dose rate data from fixed monitoring stations from close to 40 Member States. The information reported and the tools provided within IRMIS may be used in the decisionmaking process related to the implementation of public protective actions and other response actions during a nuclear or radiological emergency. The IRIX standard comprises two parts: a standard data format and a standard web service interface definition. Among the first applications of the IRIX standards are the interconnection and enabling of automated information exchange between the IAEA’s Unified System for Information Exchange in Incidents and Emergencies (USIE) and the European Community Urgent Radiological Information Exchange system (WebECURIE) [3], and the interchange of environmental radiation monitoring data in the IAEA’s IRMIS. The IAEA-IEC has worked on several emergency radiation monitoring equipment like backpacks, vehicle mounted large sensitivity gamma radiation detectors and has converted the data reports produced by these detection systems into IRIX format so that they could be assimilated in to the IRMIS. The current project has developed interactive decision support not only in the area of public protection but also in optimizing resource allocation during radiological emergencies. One of the main challenges in coordinating a large scale nuclear emergency response is identifying progress of task allocation, sample collection and analysis for a smooth flow of data in response operations. Geographic record of this progress, in the form of a map, can assist in the optimization of resource allocation, and so ensure that demand for sample collector and laboratory services is matching the supply. The adoption of the IRIX format to package radiation monitoring data in a machine readable extensible mark-up language (XML) has reduced the time and human effort (and associated errors) drastically. The language can be universally applied to all types of radiation monitoring and environmental sampling systems. Coupled with the IRMIS system of data management, visualization and analysis tools, IRIX can help analysis of resource gaps (how to distribute monitoring resources most efficiently and effectively) and can become a very strong deployment tool for the Member States. Standardized emergency monitoring data reports from different operational monitoring equipment will go a long way in harmonizing radiation monitoring data acquisition and analysis at national levels to have a sustainable global impact. The ideal system, anticipated to support up to millions of entries of sample and monitoring data, optimizes the data query system and utilizes the least core information to quickly answer questions needed in decision making during emergencies. Incorporating the IRIX format can be an effective part of such new systems.

Sandia National Laboratories has developed a model characterizing the nonlinear encoding operator of the world's first hyperspectral x-ray computed tomography (H-CT) system as a sequence of discrete-to-discrete, linear image system matrices across unique and narrow energy windows. In fields such as national security, industry, and medicine, H-CT has various applications in the non-destructive analysis of objects such as material identification, anomaly detection, and quality assurance. However, many approaches to computed tomography (CT) make gross assumptions about the image formation process to apply post-processing and reconstruction techniques that lead to inferior data, resulting in faulty measurements, assessments, and quantifications. To abate this challenge, Sandia National Laboratories has modeled the H-CT system through a set of point response functions, which can be used for calibration and anaylsis of the real-world system. This work presents the numerical method used to produce the model through the collection of data needed to describe the system; the parameterization used to compress the model; and the decompression of the model for computation. By using this linear model, large amounts of accurate synthetic H-CT data can be efficiently produced, greatly reducing the costs associated with physical H-CT scans. Furthermore, successfully approximating the encoding operator for the H-CT system enables quick assessment of H-CT behavior for various applications in high-performance reconstruction, sensitivity analysis, and machine learning.

To realize novel energy-dispersive X-ray computed tomography (CT) and to reduce the incident dose for the object, we have developed a low-dose low-scattering CT scanner with high spatial resolutions using a room-temperature cadmium telluride (CdTe) detector. X-ray photons are absorbed by the CdTe crystal, and the electric charges flowing through the CdTe crystal are amplified using a current-to-voltage and voltage-to-voltage amplifiers. The first-generation CT is accomplished by repeated translations by the detector and rotations of the object, and the effective photon energy increases with increasing amplification factor of the digital amplifier at a constant maximum output voltage of 5.0 V. The tripleenergy computed tomography (TE-CT) is performed utilizing the beam hardening by the object. In the TE-CT, the scattering photon count is reduced using a 0.5-mm-diam pinhole behind the object, and the spatial resolution is improved by a 0.25-mm-diam pinhole. The exposure time for TE-CT was 9.8 min at a total rotation angle of 180°.

The description of gamma-spectrometric apparatus “Nuclide” intended for the detection and identification of elements of radioactive space debris is presented. This device is planned to be installed on the “Universat-SOCRAT” spacecraft. The results of estimations of the sensitivity of this equipment depending on the distance to the objects under study are presented.

The digital time-resolved spot diagnostic (D-TRSD) is intended to be a fast-response, time-dependent beam diagnostic for measuring the spot size emitted from radiographic x-ray sources. It will measure spot sizes from submillimeters up to several millimeters for photon energies in the range of 150 keV to 20 MeV with doses as low as 0.03 rad up to 500 rad. The D-TRSD performs fast data acquisition as radiographic x-ray sources typically produce pulses in the tens of nanosecond ranges. The system will be optimized to capture multiple individual pulses in time within the same data record. The data collected will be used to support beam tuning and source optimization with on-the-fly evaluation of radiographic source performance. The diagnostic is based on penumbral imaging techniques. A scintillating fiber array of parallel aligned fibers is positioned in the beam path with a high-Z rolled edge inserted between the source and the array, thereby creating the penumbral x-ray signal that is captured by the D-TRSD system. The light from the scintillation conversion is recorded by individual avalanche photodiode detectors integrated into custom digitizer electronics. The penumbra is used to calculate the spot of the beam on the axis orthogonal to the fiber array based on the magnification from the rolled edge, the resolution of the spaced fibers, and the rotation of the array normal to the beam path. Many arrays can be used to capture additional spot widths about different rotations. The D-TRSD system is modular, software-driven, and easier to use than legacy TRSD systems.

We have investigated the effect of incorporation of Se into CdZnTe (CZT) matrix on x-ray response of single crystal direct conversion detectors. We used horizontal Bridgman technique for crystal growth. We have characterized the crystals using an array of diagnostics including photo-induced current transient spectroscopy (PICTS), electric field distribution using Pockels effect, and count rate response to high flux incident x-ray irradiation. We have demonstrated that the density of deep-level traps was significantly reduced by the addition of Se, resulting in more uniform electric field inside the crystal and an associated increase in x-ray count rate. The inclusion of Se within the CZT matrix, combined with additional optimization of the growth recipe enabled linear response at high incident x-ray flux.

High temperature Hall-effect investigations were used to study the change of the concentration and mobility of charge-carriers in Cd_0.85Mn_0.10Zn_0.05Te and Cd_0.85Mn_0.10Zn_0.05Te: In crystals grown by the vertical Bridgman technique. The Cd_0.85Mn_0.10Zn_0.05Te and Cd_0.85Mn_0.10Zn_0.05Te: In samples are characterized by optical and electrical measurements, and by IR-microscopy. We determined that the value of band gap increase with the Mn and Zn amount increasing in the Cd_1-x-yMn_xZn_yTe crystals. We also show that after the high-temperature Hall-effect measurements performed under Cd overpressure the both crystals resistivity increase from 10⁴ Ohm×cm to 10⁶ Ohm×cm, and amount and size of Te inclusions decrease. According to the results of the high temperature Hall-effect investigations the temperatures and Cd vapor pressures intervals were established in which Indium plays major role and controls the concentration of charge carriers.

The structural, electronic and magnetic properties of Cd_1-xMn_xTe alloy in the zinc-blende (ZB) phase within the framework of spin-polarized density functional theory using the generalized gradient approximation (GGA) are studied. In particular, we employ GGA+U^SIC method that gives a better description of systems with strong Coulomb correlations of the d-electrons. First, we discuss implementation of GGA+U method to the ground state calculations of pure CdTe and ferromagnetic MnTe. The alloy is modelled at some selected compositions by ordered structures described in terms of periodically repeated supercells for the compositions x = 0.25, 0.5, and 0.75. The compositional dependence of the lattice constant, electronic band structure and partial densities of states of ferromagnetic Cd_1-xMn_xTe alloy are studied. We estimate the spin-exchange splitting energies produced by the Mn 3d-states and determine the exchange constants for the conduction and valence bands of the alloy. The energy positions of the occupied and unoccupied Mn 3d-bands in the electronic structure of ferromagnetic Cd_1-xMn_xTe alloy are also presented. Our calculations using GGA+U^SIC approach agree well with the available experimental data and other calculations.

The electrical and detection properties of the X/gamma-ray detectors, fabricated using commercial detector-grade p-like CdTe single crystals grown by Acrorad Co., were studied. The detectors were developed as Cr/CdTe/Au Schottky diodes using CdTe wafers with an area of 5 × 5 mm² and different thicknesses (0.25, 0.5, 0.75, 1.0 and 2.0 mm). Both the Schottky and Ohmic contacts were formed on the opposite sides of semi-insulating CdTe(111) crystals after preliminary chemical and Ar-ion etchings using different parameters. The Cr/CdTe/Au Schottky diodes demonstrated steep rectification that made it possible to apply high reverse bias voltage up to V = 1500-2000 V at moderately low dark currents. Having the rectifying contact area of 10 mm², the diodes showed dark currents ~ 2-3 nA at V = 1000 V (T = 300 K). The dominant charge carrier transport mechanisms were analyzed using the I-V characteristics and determined as: generation-recombination in the space-charge region (SCR) at V = 1-100 V, the charge transport in the conditions when the SCR width exceeded the thickness of a semiconductor crystal at elevated voltages and, finally currents limited by space charge at even higher bias voltages. For radiation from a ¹³⁷Cs radioisotope, the Cr/CdTe/Au detectors fabricated on thin (0.5 mm) semiconductor crystals showed the highest energy resolution (FWHM = 0.5%@662 keV). The detection efficiency increased in 4 times with increasing the crystal thickness (up to 2 mm), although the energy resolution deteriorated from 0.5 % to 3 % that, however, was still acceptable for spectroscopic operation of the detectors.

Cd_0.9Zn _0.1Te (CZT) based pixelated radiation detectors have been fabricated and characterized for high-energy gamma ray detection. Large-volume ingots with large single crystalline grains have been grown and several 10 × 10 pixilated detectors have been fabricated from the grown crystals for imaging studies. Guard ring grids have been designed and fabricated to reduce cross-talk and inter-pixel/inter-electrode leakage. The grown crystals were initially characterized in planar configurations through electrical and optical methods prior to the fabrication of pixilated structure. Current-voltage (I-V) measurements revealed very low leakage current in the range of nA at an operating bias voltage of 1000 V and a resistivity of ~ 6×10¹⁰ Ω-cm was obtained. Infrared transmission imaging revealed average tellurium inclusion size of <8 micron. Measurements through Pockels’ effect has revealed a near-uniform depth-wise distribution of the internal electric field. Gamma-ray spectroscopy using ¹³⁷Cs (662 keV) radiation source on the monolithic pixelated structure showed excellent detection performance for all the 100 pixels, with a resolution ~1.5 % FWHM.

The study of the electro-physical properties of n-type semi-insulating crystals of indium-doped Cd(Mn)Te solid solution with a resistivity ~ (4÷5)×10¹⁰ Ohm×cm at T = 300 K was carried out. The structures both with an ohmic (In/Cd(Mn)Te/In) contacts and with the rectifying (Ni/Cd(Mn)Te/In) contact were fabricated. It was found that for the Ni/Cd(Mn)Te/In structure, the main mechanisms of charge transport were: the generation currents in the space-charge region, space-charge limited currents (SCLC) at high voltages, and the Ohm’s law was valid only on initial section the of the volt-ampere characteristics (I-VC). Calculation of the generation current dependence on the voltage according to the theory of Sah-Noyce-Shockley was carried out. For the In/Cd(Mn)Te/In structure it was observed the I-VC initial section, where the Ohm’s law was implemented, and the SCLCs with the participation of deep centers (traps) in semiinsulating crystal - at greater voltages. The concentration of deep centers (N_t ~ 7.4×10¹⁰ cm^-3 ) responsible for the trap mechanism in SCLC In/Cd(Mn)Te/In structures was calculated. The energy position E_t of the deep levels was determined (provided that the energy was calculated from the valence band edge, E_t = 0.89÷0.9 eV). It was discussed and grounded the assumption that SCLC was the main mechanism limiting the operating voltages and, consequently, the use of Cd(Mn)Te-based ionizing-radiation detectors with ohmic contacts.

Assessment of the distribution of radioactive contamination is an essential process for safe decommissioning. Gamma cameras are widely used to investigate the hot spots of radioactive materials. The 3D information of the radioactive contamination is required to reduce the occupational exposure and the radioactive waste. The purpose of this study is to design a multi-pinhole collimator for the 3D gamma ray imaging. The collimator was designed by Monte Carlo simulation and the performance was evaluated by lab test. The collimator consists of four cone-shaped pinholes, tungsten aperture, and lead septa. The acceptance angle and the source to detector distance were 40° and 15 cm, respectively. A number of 2D images were obtained by the linear motion of the gamma camera and the 3D images were reconstructed by filtered back-projection algorithm. As a result, the experimental results were within 2% of the expected values.