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This study presents a new dead-time measurement method using the gamma attenuation law and generalized dead-time models for nuclear gamma-ray detectors. The dead-time of the Nal(TI) detection system was obtained to validate the new dead-time determination method using very thin lead and polyethylene absorbers. Non-paralyzing dead-time was found to be 8.39 mu s, and paralyzing dead-time was found to be 8.35 mu s using lead absorber for Nal(TI) scintillator detection system. These dead-time values are consistent with the previously reported dead-time values for scintillator detection systems. The gamma build-up factor's contribution to the dead-time was neglected because a very thin material was used. (C) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC.

[EN] Molecular imaging systems, such as positron emission tomography (PET), use detectors providing energy and a 3-D interaction position of a gamma ray within a scintillation block. Monolithic crystals are becoming an alternative to crystal arrays in PET. However, calibration processes are required to correct for nonuniformities, mainly produced by the truncation of the scintillation light distribution at the edges. We propose a calibration method based on the Voronoi diagrams. We have used $50 \times 50 \times 15$ mm(3) LYSO blocks coupled to a $12\times 12$ SiPMs array. We have first studied two different interpolation algorithms: 1) weighted average method (WAM) and 2) natural neighbor (NN). We have compared them with an existing calibration based on 1-D monomials. Here, the crystal was laterally black painted and a retroreflector (RR) layer added to the entrance face. The NN exhibited the best results in terms of XY impact position, depth of Interaction, and energy, allowing us to calibrate the whole scintillation volume. Later, the NN interpolation has been tested against different crystal surface treatments, allowing always to correct edge effects. Best energy resolutions were observed when using the reflective layers (12%-14%). However, better linearity was observed with the treatments using black paint. In particular, we obtained the best overall performance when lateral black paint is combined with the RR., This work was supported in part by the European Research Council through the European Union's Horizon 2020 Research and Innovation Program under Grant 695536, and in part by the Spanish Ministerio de Economia, Industria y Competitividad under Grant TEC2016-79884-C2-1-R.

Radiation detectors, especially for X- and gamma-rays, are being developed rapidly that utilize the advantages of semiconductor detectors operating at room temperature. CdTe and CdZnTe based detectors have successfully dominated the commercial market. Both the materials, however, face limitations due to the presence of high concentrations of intrinsic defects such as Te inclusions and sub-grain boundaries. In the recent years, we have observed that the addition of selenium circumvents many issues pertaining to CdTe/CdZnTe. As a result, the new quaternary material Cd1−xZnxTe1−ySey (CZTS) is emerging as a next-generation room temperature radiation detector material with the potential to supersede CdZnTe, competing in both cost and detector performance. In this presentation we will discuss the path toward optimization of the composition of the quaternary compound for the best detector performance.

The detection efficiency of a gamma ray detector should be calibrated prior to the measurement of activity in samples. The aim of this research is to develop a simple experimental technique to calibrate the efficiency of detectors for geometrical sources by replicating their responses from virtually equivalent sources (VES) constructed from a collection of Standard Point Source (SPS) measurements. Experiments were performed to replicate the response of a disk source of 5.2 cm radius by equivalent disk sources (EDS) reconstructed from a collection of 19, 91 and 169 SPS measurements to optimize the number of measurements, response of detector for radially symmetric SPS locations was verified through Absolute Peak Efficiency (APE) calculations. APE was calculated experimentally for the actual disk source and EDS as well as using EGS5 simulations. The difference between experimentally measured and simulated APE for 5.2 cm EDS was observed to be about 7.8 %, 5.2 % and 5.4 % for 137Cs and about -1.3 %, 1.3 % and 2.7 % for 22Na for the EDS constructed from 19, 91- and 169 SPS measurements respectively

The relevance and benefits of the new TAIGA gamma observatory complex in the Tunka Valley (50 km from Lake Baikal) are discussed. The main aim of the TAIGA installation is to study high-energy gamma radiation and search for cosmic pevatrons. The first series of gamma stations was commissioned in 2019 and covers an area of 1 km2. Its expected integral gamma radiation sensitivity at an energy of 100 TeV over 300 h of source monitoring is (2–5) × 10−13 TeV cm−2 s−1. It is planned to expand the effective area of TAIGA gamma observation to 10 km2 in the future.

© 2018 Elsevier B.V. The quantitative determination of radionuclides by gamma ray spectrometry requires a high accuracy of detection efficiency determination. Different software codes for efficiency determination are available. The aim of this work was to compare different methods and software used for efficiency calibration modeling and analyses. For that purpose, same samples of vegetation and soil of known activities were measured using HPGe detectors in two laboratories which are employing different software for mathematical efficiency calibrations and analyses, LabSOCS which is based on purely mathematical calculations and Angle which uses a semi-empirical approach. The codes were also tested on samples with unknown reference values (different geometries and matrices). The main advantages and disadvantages of both software were compared. Both Angle and LabSOCS gave comparable and consistent results for different detectors, matrices and geometries used. Deviations of the order of 10% or less obtained from the comparison of different sets of parameters are acceptable and imply that Angle and LabSOCS can be considered reliable for gamma ray detector efficiency calibrations. The main limitation of LabSOCS is in its inability to be used on newly installed detectors (factory characterization needed first), as for Angle the main drawback is in its demand for reference materials which can be costly as well as the need for plenty detector characteristics which are not always provided by the manufacturer.

International audience; Monte Carlo simulations are used to test the Pulse Shape Comparison Scanning (PSCS) technique implemented at the IPHC scanning table. The technique allows the full volume characterization of a given position sensitive detector resulting in the construction of the corresponding database of pulses. The tests, performed on a high purity germanium (HPGe) detector unit of the AGATA array, aim to quantify the accuracy of the technique and validate it through the evaluation of parameters extracted from the resulting database. The simulations use a combination of tools such as Geant4, SIMION and the Agata Detector Library (ADL). Quality parameters are extracted at various gamma-ray energies and the impact of the input statistics on the parameters is also analyzed.

Radiation detectors with different thickness are needed to detect gamma rays with various energies. In this paper, a post-growth annealing method was used to improve the properties of CdMnTe:In (CMT:In) crystals with different thickness for gamma-ray detectors. The results indicated that Te inclusions in CMT:In crystals with different thickness were reduced remarkably after annealing. Both the resistivity and IR transmittance of annealed CMT:In crystals with different thickness increased obviously, which suggested that the crystal quality was improved. For the detectors fabricated by annealed CMT:In slices with 1 mm, 2 mm and 5 mm thickness, the energy resolutions were enhanced about 252%, 193% and 141%, respectively. And ( μτ ) e values were enhanced about 80%, 80% and 76%, respectively. The performance of the detectors was greatly improved after annealing.

Purpose: The sentinel lymph node (SLN) biopsy technique has highly evolved during the last 20 yr. Consequently, the intraoperative use of Gamma Probes (GPs) for SLN mapping is increased. This preliminary study evaluates a novel directional GP prototype. This proof-of-concept prototype is designed to identify the direction of radiopharmaceuticals uptakes, by combining the information from multiple detectors. The purpose of this work is to develop a tool able to effectively guide the surgeon reducing the surgery time. Methods: The proposed prototype consists of three CsI(Tl) scintillation crystals, each coupled with an S10931 silicon photomultiplier (Hamamatsu Photonics K.K., Hamamatsu, JP). The three detectors lie on the same plane with an angle of 30° between them. The central detector is placed as in a com- mon GP, so it can be used to pinpoint the target tissue. Meanwhile, the lateral sensors provide a broader view of the surgical field. A dedicated data acquisition system digitizes and processes the signals from the front-end electronics. Finally, an embedded system, based on ARM processor, calcu- lates and displays the acquired count rates. In order to assess the prototype behavior, the isosensitivity curves for the three detectors were measured. Meanwhile, for the central one, the main quality criteria measurements were also performed (i.e., sensitivity, radial sensitivity, and spatial resolution). Results: For the central detector, the measured sensitivity at the tip of the probe is better than 5 cps/kBq. The full width at half maximum (FWHM) of the radial sensitivity is less than 30° and the FWHM of the lateral sensitivity (spatial resolution) is about 7.2 mm. The central detector measured isosensitivity distribution shows a narrow profile in agreement with the spatial resolution measured. On the contrary, the two lateral detectors exhibit widespread isosensitivity distributions that mean a larger field of view. The system had shown satisfactory performance and reliability, meeting the mini- mal requirements of gamma probe systems. Conclusions: The prototype presented in this paper allows a rapid localization by the use of the whole system, while the sole central detector can be used to pinpoint the target source. This device, unlike common GPs, allows localizing simultaneously different areas of radiopharmaceuticals uptake, thus precisely guiding the surgeon to the region of interest. These preliminary results encour- age to develop a further prototype for intraoperative validation.

One step of the IRFU GBAR project aims at producing a dense low temperature positronium gaz. In order to characterize the positronium cloud we have tested a detector able to measure gamma energies in the 511 keV domain or lower, which is compact, fast, and insensitive to high magnetic fields. It uses the PreLude 420 scintillating crystal from Saint Gobain and large area Hamamatsu avalanche photodiodes. The performances of the system are presented. It could be used for other purposes.

Measurements of Ra-226 activity from eight HPGe gamma ray detectors at the NC State University PULSTAR Reactor were analyzed for evidence of periodic variations, with particular attention to annual variations. All measurements were made using the same reference source, and data sets were of varying length taken over the time period from September 1996 through August 2014. Clear evidence of annual variations was observed in data from four of the detectors. Short time periodograms from the data sets suggest temporal variability of both the amplitude and frequency of these variations. The annual variations in two of the data sets show peak values near the first of February, while surprisingly, the annual variations in the other two are roughly out of phase with the first two. Three of the four detectors exhibited annual variations over approximately the same time period. A joint statistic constructed by combining spectra from these three shows peaks approximating the frequencies of solar r-mode oscillations with $\nu_R = 11.74$ cpy, $m=1$, and $l=3,5,6.$ The fact that similar variations were not present in all detectors covering similar time periods rules out variations in activity as the cause, and points to differing sensitivities to unspecified environmental parameters instead. In addition to seasonal variations, the modulation of environmental parameters by solar processes remains a possible explanation of periodogram features, but without requiring new physics., Comment: Results in Physics (2016)

Gamma-ray logging tools are applied worldwide. At various locations, calibration facilities are used to calibrate these gamma-ray logging systems. Several attempts have been made to cross-correlate well known calibration pits, but this cross-correlation does not include calibration facilities in Europe or private company calibration facilities. Our aim is to set-up a framework that gives the possibility to interlink all calibration facilities worldwide by using ‘tools of opportunity’ – tools that have been calibrated in different calibration facilities, whether this usage was on a coordinated basis or by coincidence. To compare the measurement of different tools, it is important to understand the behaviour of the tools in the different calibration pits. Borehole properties, such as diameter, fluid, casing and probe diameter strongly influence the outcome of gamma-ray borehole logging. Logs need to be properly calibrated and compensated for these borehole properties in order to obtain in-situ grades or to do cross-hole correlation. Some tool providers provide tool-specific correction curves for this purpose. Others rely on reference measurements against sources of known radionuclide concentration and geometry. In this article, we present an attempt to set-up a framework for transferring ‘local’ calibrations to be applied ‘globally’. This framework includes corrections for any geometry and detector size to give absolute concentrations of radionuclides from borehole measurements. This model is used to compare measurements in the calibration pits of Grand Junction, located in the USA; Adelaide (previously known as AMDEL), located in Adelaide Australia; and Stonehenge, located at Medusa Explorations BV in the Netherlands.

This study reports on nonintrusive depth estimation of a buried caesium-137 radioactive source using a ground penetrating radar (GPR) and a gamma ray detector. Specifically, the bulk density estimates from the GPR was used to fit a gamma ray attenuation model to the data from the detector. The depth of the source was successfully estimated when buried up to 18 cm in sand, gravel and soil. This will help in nonintrusive monitoring of nuclear contaminated sites.

In a scintillation detector, the light generated in the scintillator by a gamma interaction is converted to photoelectrons by a photodetector and produces a time-dependent waveform, the shape of which depends on the scintillator properties and the photodetector response. Several depth-of-interaction (DOI) encoding strategies have been developed that manipulate the scintillator’s temporal response along the crystal length and therefore require pulse shape discrimination techniques to differentiate waveform shapes. In this work, we demonstrate how maximum likelihood (ML) estimation methods can be applied to pulse shape discrimination to better estimate deposited energy, DOI and interaction time (for time-of-flight (TOF) PET) of a gamma ray in a scintillation detector. We developed likelihood models based on either the estimated detection times of individual photoelectrons or the number of photoelectrons in discrete time bins, and applied to two phosphor-coated crystals (LFS and LYSO) used in a previously developed TOF-DOI detector concept. Compared with conventional analytical methods, ML pulse shape discrimination improved DOI encoding by 27% for both crystals. Using the ML DOI estimate, we were able to counter depth-dependent changes in light collection inherent to long scintillator crystals and recover the energy resolution measured with fixed depth irradiation (~11.5% for both crystals). Lastly, we demonstrated how the Richardson-Lucy algorithm, an iterative, ML-based deconvolution technique, can be applied to the digitized waveforms to deconvolve the photodetector’s single photoelectron response and produce waveforms with a faster rising edge. After deconvolution and applying DOI and time-walk corrections, we demonstrated a 13% improvement in coincidence timing resolution (from 290 to 254 ps) with the LFS crystal and an 8% improvement (323 to 297 ps) with the LYSO crystal.

A lightweight, low-cost multi-panel direction-sensitive radiation detector prototype has been developed at Oregon State University that is designed to be mounted on a small unmanned aerial system to autonomously search for radiation sources while flying close to the ground. The detection system comprises sixteen BGO-SiPM detector panels with an adjustable view angle, and signal outputs are processed in parallel in an FPGA. The minimum detectable activity was calculated to be 1.3 μCi of 137 Cs at 1 m in under 60 s. The counting response of the detector panels were characterized and found to have 4.7% relative standard deviation, indicating good uniformity in overall design and assembly. The detector was also able to estimate the direction of a 12.3 μCi 137 Cs source 100 cm from the device center with 2.3° accuracy in a 95% confidence width of 10.8° in 60 s.

Range verification of particle beams in real time is considered a key for tapping the full potential of radio-oncological particle therapies. The novel technique of prompt gamma-ray timing (PGT), recently proposed and explored in first proof-of-principle experiments, promises range assessment at reasonable expense but challenges detectors, electronics, and data acquisition. Energy-selected time distributions have to be measured at very high throughput rates to obtain the statistics necessary for range verification with single pencil beam spots. Clinically applicable systems should provide a time resolution of about 200 ps, to be obtained with large (about 2” diameter) scintillators, detector loads in the few-Mcps range, and data acquisition rates around 1 Mcps, if possible with compact and inexpensive systems. Such requirements can be met best with ${\rm CeBr}_{3}$ scintillators read out with conventional photomultiplier tubes, coupled to commercial but customized electronics featuring high-resolution pulse digitization and fast digital signal processing. The paper deduces design parameters from the constraints given by typical treatment conditions, and presents first results obtained with prototype detectors and electronics developed in accordance with the derived specifications.

In this study, direct mathematical formulae are found for measuring the full-energy peak efficiency of an HPGe well-type detector, and the values of the measured efficiencies are compared with published studies on the old experimental and theoretical methods with good agreement. In this new approach, the path length d(θ, φ) is derived as a function of the polar angle θ and the azimuthal angle φ, which will reduce the mathematical formulae to a simple and compact shape.

The longer electron lifetime of today’s CdZnTe (CZT) crystals allows for free carriers to travel longer distances in the crystals, which means that, in principle, thicker devices could be fabricated. These thicker CZT devices would offer greater detection efficiency for high-energy gamma-ray detectors. However, up to now, the thicknesses and sizes of actual detectors have still been limited by the nonuniform detector response, and the biggest devices reported in the literature are ${(20\times 20\times 15)}\hbox{-mm}^3$ pixelated detectors with a drift distance of 15 mm. Although thicker and bigger single crystals are becoming available today, the high requirements on their crystal quality drastically reduce their acceptance yield and increase their cost. Fortunately, in many cases, the inhomogeneity in response can be corrected by segmenting the active volumes of the detectors and correcting the responses generated from each of the voxels. Such high-granularity position-sensitive detectors open up the opportunity for using thicker and less-expensive CZT crystals. The goal of this work is to demonstrate that today’s commercial high electron mobility-lifetime CZT material is suitable for a new class of detectors with 20-25-mm drift distances and even larger in the near future, provided that the detectors’ response nonuniformities can be corrected on a scale comparable to or larger than the sizes of the electron clouds, which is $\sim 100~\mu\hbox{m}$ .

Schlumberger produces gamma ray detectors for use in its oil exploration tools. The detectors are based on rugged ceramic photomultiplier tubes (PMTs), produced in house, and various scintillators. For oilfield applications, gamma ray detectors require reliable and stable performance during hundreds of hours of operation in harsh well-logging environment with sustained high shock levels and hot temperatures. Therefore, the scintillator materials must withstand high mechanical and temperature shock. In some environments, the temperature ramp rates can reach as high as 40 C/minute, which could create enough stress to break scintillator materials and their packaging. The mechanical shock levels exceed 100g. The most commonly used scintillator in oilfield nuclear tools is NaI(Tl), in a special shock-proof hermetic packaging, whereas newer Schlumberger tools use LaBr3(Ce) and YAP(Ce) scintillators. We have evaluated ruggedness of a YAP (Yttrium Aluminum Perovskite) scintillator in comparison to the more known behavior of NaI(Tl) and LaBr3(Ce).

著者人数: 42名, Accepted: 2018-03-19, 資料番号: SA1170324000

The average ionization energy required to excite an electron-hole pair in TlBr was estimated to be $5.50 \pm 0.05~\hbox{eV}$ by comparing the peak position of 59.5-keV gamma rays obtained from four pixels of a pixelated TlBr detector to the peak position obtained from a Si PIN photodiode at room temperature.

Several models of (quantum) gravity predict tiny violations of Lorentz Invariance (LI) at microscopic (Planckian) scales, which increase with the energy of the probe and amplified with the distance of the source. Thus, astrophysical/cosmological energetic probes provide the best test grounds of LI. The talk reviews the status and prospects of such tests, using high-energy cosmic γ detectors. The Ĉerenkov Telescope Array (CTA) is an excellent experimental tool for making such tests with sensitivities exceeding those possible using other detectors.

We have evaluated gamma ray detectors built with a rugged YAP(Ce) scintillator and two kinds of photomultiplier devices: a commercial rugged PMT (rated for $200 ^{circ}\mathrm {C}$ operation) and a rugged ceramic PMT with a 1-in. window designed and built in house at the Schlumberger Princeton Technology Center. For oilfield applications, gamma ray detectors require reliable and stable performance during hundreds of hours of operation in the harsh well-logging environment (high shock levels and high temperature). Therefore, the focus of this evaluation was on the characterization of the photomultiplier reliability under high temperature and high shock conditions. Several gamma ray detectors have been built with a YAP scintillator (chosen for stable temperature performance) in two configurations: with a commercial high-temperature PMT and a 721x model Schlumberger PMT produced for its oilfield PNX tools [1].

Searching for new astrophysical sources is an important physical goal of current and nearly further ground-based gamma-ray detectors, such as HAWC, LHAASO and CTA. The gamma-ray signal appears as an excess number of events. The significance of the excess is estimated using statistical method and is used to determine whether to accept the signal or not. Up to now, four main statistical methods, including the classical Li-Ma method, the weighted method, the likelihood method and the chi-squared method, have been used in the majority of ground-based extensive air shower (EAS) experiments, such as Tibet ASγ, MILAGRO, ARGO-YBJ and HAWC. While these methods are not well tested for the accuracy in previous works. In this work, we develop a standard to test the accuracy of different methods basing on different experimental conditions. We find some problems for some methods, which have been already used in experiment data analysis. Finally, we obtain the limitation of different methods and provide application conditions for different methods, respectively. Additionally, we also test the superiority of different statistical methods and provide our best recommendations for different physical analyses.

Currently the detection of Very High Energy gamma-rays for astrophysics rely on the measurement of the Extensive Air Showers (EAS) either using Cherenkov detectors or EAS arrays with larger field of views but also larger energy thresholds. In this talk we present a novel hybrid detector concept for a EAS array with an improved sensitivity in the lower energies ($\sim 100\,$GeV). We discuss its main features, capabilities and present preliminary results on its expected perfomances and sensitivities.This wide field of view experiment is planned to be installed at high altitude in South America making it a complementary project to the planned Cherenkov telescope experiments and a powerful tool to trigger further observations of variable sources and to detect transients phenomena., 5 pages, 5 figures, Proc. of RICAP2016, v2: correct affiliation and doi

X- and gamma-ray detectors are increasingly becoming essential tools for science and technology in various fields. These detectors offer broad applications such as homeland security, nonproliferation, nuclear security, medical imaging, astrophysics, and high energy physics. All these applications demand high-resolution detectors operable at room temperature and available at a reasonable cost. CdZnTe (CZT) is the material of choice for this purpose; however, the material still suffers from intrinsic defects such as highly decorated subgrain boundary networks and a high concentration of secondary phases. These defects not only hinder the charge transport but also create a spatial inhomogeneity in the charge transport properties, subsequently causing substantial degradation in detector response particularly for relatively thick (>1 cm) detectors. Some of the material deficiencies suffered by CZT have been addressed by adding selenium into the CZT matrix. Selenium was found to be very effective in producing material that is principally free from a subgrain boundary network with the occasional appearance of subgrain boundaries with reduced secondary phases decorating these boundaries. The resulting quaternary compound CdZnTeSe (CZTS) showed excellent material quality mitigating some major deficiencies suffered by CZT. Virtual Frisch grid detectors were fabricated from the as-grown CZTS ingots, and they demonstrated high resolution spectroscopic grade. The excellent CZTS material contained very low defects and was found to potentially increase the yield of high-quality detectors as compared to CZT.X- and gamma-ray detectors are increasingly becoming essential tools for science and technology in various fields. These detectors offer broad applications such as homeland security, nonproliferation, nuclear security, medical imaging, astrophysics, and high energy physics. All these applications demand high-resolution detectors operable at room temperature and available at a reasonable cost. CdZnTe (CZT) is the material of choice for this purpose; however, the material still suffers from intrinsic defects such as highly decorated subgrain boundary networks and a high concentration of secondary phases. These defects not only hinder the charge transport but also create a spatial inhomogeneity in the charge transport properties, subsequently causing substantial degradation in detector response particularly for relatively thick (>1 cm) detectors. Some of the material deficiencies suffered by CZT have been addressed by adding selenium into the CZT matrix. Selenium was found to be very effective in producing m...

The use of large gamma-ray detector arrays with electromagnetic separators is a powerful combination. Various types of gamma-ray detectors have been used; some provide high detector efficiency such as scintillation detector array, others use Ge detectors for good energy resolution, and recently developed Ge energy tracking arrays gives both high peak-to-background ratio and position resolution. Similarly, different types of separators were used to optimize the performance under different experimental requirements and conditions. For example, gas-filled separators were used in heavy element studies for their large efficiency and beam rejection factor. Vacuum separators with good isotope resolution were used in transfer and fragmentation reactions for the study of nuclei far from stability. This paper presents results from recent experiments using gamma-ray detector arrays in combination with electromagnetic separators, and discusses the physics opportunities provided by these instruments. In particular, we review the performance of the instruments currently in use, and discuss the requirements of instruments for future radioactive beam accelerator facilities.

Cs 2 LiYCl 6 (CLYC) is one of the most interesting new scintillators developed during the last fifteen years. Its use as a thermal neutron scintillator was discovered in 1999 at the Delft University of Technology in Netherlands. In 2003, CLYC was selected by Radiation Monitoring Devices (RMD) for further studies and ultimately resulted in a commercial product. RMD's investigation of CLYC showed that it is a very good gamma ray detector with excellent 4% or better energy resolution, making it an ideal choice for dual mode detectors. Recently, Bubble Technology Industries of Canada discovered the possibility of fast neutron detection with CLYC, increasing its versatility even further. In this paper, we present the progress of CLYC’s development since its inception, with a focus on the work conducted at RMD. Our initial results with small crystals are presented, followed by data collected with samples of consecutively larger volumes and quality. We discuss the improvements in the energy resolution from 7% to 3.6%, as well as volume from 1 cm 3 to 100 cm 3 . In addition, we address basic properties, gamma ray and neutron detection, pulse shape discrimination, and recently discovered fast neutron detection.

Monte Carlo simulations were used to model gamma ray interactions at 1 MeV and 11 MeV within liquid krypton to understand geometry effects and energy containment. Two Monte Carlo codes were used in this work: Geant4 and MCNP5. The agreement of the two codes was shown by the comparison of the calculated average energy deposition and fraction of incident gamma energy deposited as a function of chamber lengths and gamma ray offsets. Modeling shows that good energy containment for 1 MeV gamma rays occurs for chamber depths of 20 cm. For gamma rays entering parallel to the central axis of the detector, 1 MeV showers are well contained up to approximately 1 cm of the detectors' edge. For 11 MeV gamma rays the acceptance plateau occurs at a depth of 40 cm and 20 cm from the detectors' edge.

The first Polaris system was built in September 2010 and has gone through significant testing at multiple DOD and DOE facilities as well as at the University of Michigan. It has been biased almost continuously for the 18 months of its current lifespan without any replacement of its detectors. The second Polaris system was built in June 2011 and has also been almost continuously biased during its lifespan. The continuous operation of both devices has provided the best opportunity to study the long-term stability of pixelated CdZnTe detectors. Spectroscopic performance has been monitored throughout each system's lifespan to study their performance over time and the impact on long term operation of these devices. It is shown that the charge transport properties and spectroscopic performance of these CdZnTe detectors are stable over time and devoid of fabrication or assembly issues. It is expected that future detectors will exhibit excellent stability.

High demand for nuclear reaction cross-section measurements relevant for astrophysical processes requires the development of new experimental techniques that allow for investigation of, often very low, cross-sections. For this purpose, a new 4 π Summing NaI(Tl) detector (SuN) has been constructed, which is an 8-fold segmented NaI(Tl) barrel read by 24 photomultipliers. The design of the detector will be presented and detailed results of the commissioning experiments utilizing standard calibration sources and known Al 27 ( p , γ ) Si 28 resonances will be discussed.

Testing of 20 × 20 × 15 mm3 3D position sensitive, CdZnTe detectors grown by Redlen Technologies Inc. has shown that 98 out of the 145 detectors analyzed achieved sub-1% FWHM at 662 keV for single-pixel events. Improvements in the detector performance over time reflect the improvements in detector growth and fabrication over the past several years. In addition to the spectroscopic performance of the detectors, the imaging performance of each detector was also quantified. The results show that imaging is weakly correlated to the spectroscopic performance, and more strongly correlated to the accuracy of the depth reconstruction. Other detector issues such as gain deficit and gain variation are also discussed.

We have developed a simpler, smaller, and thus less expensive gamma-ray detector that can roughly determine the incident direction of a radiation source with moderate angular resolution, aiming for personal use beyond that afforded by conventional survey meters. The detector consists of six GAGG(Ce) scintillators with dimensions of 20 × 20 × 6 mm3 on each face of a 3-cm cubic lead block. Signals from each scintillator are read by a 3 × 3 mm2 Hamamatsu MPPC. We then applied χ2 fit to the observed count number set in order to determine the incident direction and set our angular accuracy goal of 22.5°. Through simulation, we injected 662 keV gamma rays uniformly from in front of the detector. We found that the R 90 is distributed from 6.0° to 18.3° in all 980 directions for one-minute exposure to a 137Cs source that gives 0.15 μSv/h. Furthermore, our detector achieved the targeted value under BG intensity of 0.25 μSv/h in the experiment.

A maneuverable laboratory device, developed to evaluate the compatibility of a gamma ray detector and MRI magnetic gradients, is presented The tool was designed to characterize the sensitivity to switching gradients of the detector modules of INSERT, a clinical SPECT ring compatible with commercial MRI scanners. The time-varying magnetic fields generated with this tool can be tailored to be identical in amplitude (0-20 mT) and frequency (0.1-3 kHz) to those utilized in common MRI sequences, but can be localized with cm-resolution, in such a way that sensitive points inside the hardware under test can be revealed. The device has been utilized to identify weaknesses inside the ASIC board of the INSERT system. Thanks to its use in mapping the board, a novel layout demonstrated improved rejection of disturbances.

CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability.

The Multimodal Imaging of Neurological Disorders (MINDView) project aims to develop a dedicated brain Positron Emission Tomography (PET) scanner with sufficient resolution and sensitivity to visualize neurotransmitter pathways and their disruptions in mental disorders for diagnosis and follow-up treatment. The PET system should be compact and fully compatible with a Magnetic Resonance Imaging (MRI) device in order to allow its operation as a PET brain insert in a hybrid imaging setup with most MRI scanners. The proposed design will enable the currently-installed MRI base to be easily upgraded to PET/MRI systems. The current design for the PET insert consists of a 3-ring configuration with 20 modules per ring and an axial field of view of ~15 cm and a geometrical aperture of ~33 cm in diameter. When coupled to the new head Radio Frequency (RF) coil, the inner usable diameter of the complete PET-RF coil insert is reduced to 26 cm. Two scintillator configurations have been tested, namely a 3-layer staggered array of LYSO with 1.5 mm pixel size, with 35×35 elements (6 mm thickness each) and a black-painted monolithic LYSO block also covering about 50×50 mm 2 active area with 20 mm thickness. Laboratory test results associated with the current MINDView PET module concept are presented in terms of key parameters׳ optimization, such as spatial and energy resolution, sensitivity and Depth of Interaction (DOI) capability. It was possible to resolve all pixel elements from the three scintillator layers with energy resolutions as good as 10%. The monolithic scintillator showed average detector resolutions varying from 3.5 mm in the entrance layer to better than 1.5 mm near the photosensor, with average energy resolutions of about 17%.

Calibrating the gamma-ray detection efficiency of radiation detectors in a field environment is difficult under most circumstances. To counter this problem we have developed a technique that uses a Cerium doped Lanthanum-Tri-Chloride (LaCl 3 :Ce) scintillation detector to provide gated gammas (Guillot-Noel et al. (1999) [1] and van Loef et al. (2001) [2] ). Exploiting the inherent radioactivity of the LaCl 3 :Ce due to the long-lived radioactive isotope 138 La ( t 1/2 =1.06×10 11 yr) allows the use of the 788 and 1436 keV gammas as a measure of efficiency. In this paper, we explore the effectiveness of using the beta-gamma coincidences radiation LaCl 3 :Ce detector to calibrate the energy and efficiency of a number of gamma-ray detectors.

Sputtered yttrium metal forms a thin hole-barrier contact on both p- and n-type germanium semiconductor detectors. Yttrium contacts can provide a sufficiently high hole barrier to prevent measurable contact leakage current below ∼120 K. Detectors having yttrium contacts produce good gamma-ray spectroscopy data.

There are many systems for counting photons such as gamma-rays emitted from radioactive sources. Many of these systems are also position-sensitive, which means that the system provides directional information about recorded events. This paper investigates whether or not the additional information provided by position-sensitive capability improves the performance of detecting a point-source in background. We analyze the asymptotic performance of the generalized likelihood ratio test (GLRT) and a test based on the maximum-likelihood (ML) estimate of the source intensity for systems with and without position-sensitive capability. When the background intensity is known and detector sensitivity is spatially uniform, we prove that position-sensitive capability increases the area under the receiver operating characteristic curve (AUC). For cases when detector sensitivity is nonuniform or background intensity is unknown, we provide numerical results to illustrate the effect of the parameters on detection performance.

Cerium bromide (CeBr 3 ) has become a material of interest in the race for high-resolution gamma-ray spectroscopy at room temperature. This investigation quantified the potential of CeBr 3 as a room-temperature, high-resolution gamma-ray detector. The performance of CeBr 3 crystals was compared to other scintillation crystals of similar dimensions and detection environments. Comparison of self-activity of CeBr 3 to cerium-doped lanthanum tribromide (LaBr 3 :Ce) was performed. Energy resolution and relative intrinsic efficiency were measured and are presented.

This paper presents the CNES analysis of CCD dark current degradation in orbit. For the first time, data coming from several detectors in orbit have been collected and congregated to extract general trends about in-flight detector behaviours. The in-orbit degradation is therefore compared to the on-ground prediction for each detector. This work has been done in collaboration with the CNES detection subsystem office, the CNES image quality office and the CNES components & environment effects office.

The progress in nanotechnologies has been largely due to the advent of a new generation of gamma-ray sources and position detectors, which can ensure both coordinate and temporal measurements within the nanoand femtoranges. The paper offers scientific and engineering solutions related to designing detector materials and structures for detecting single quanta of x- and γ-rays and high-energy charged particles. These are multielement position detectors of a new generation for nanostructure imaging and examination in gamma rays.

We are beginning development of a Transition Edge Sensor (TES) based gamma-ray detector for use in Coincidence-Doppler-Broadening (CDB) Positron-Annihilation-Spectroscopy (PAS) studies. We are specifically motivated to asses and study damage to nuclear Reactor Pressure Vessels (RPVs) which results from neutron irradiation during reactor operation. In this paper we provide a brief introduction to CDB-PAS and discuss our detector design.