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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. [ABSTRACT FROM AUTHOR]

A porous tungsten oxide (WO 3 ) NO 2 sensor was developed by a one-step flame based process called Reactive Spray Deposition Technology (RSDT). This nano-crystalline WO 3 film was deposited directly on gold interdigitated electrodes. The sensing characteristics of this NO 2 sensor was measured at the parts per million (ppm) level, (0.17–5 ppm in air) at 300 °C. The sensors showed a relatively fast response time (∼7s) and recovery time (∼5 min), respectively. The stability of the sensor was evaluated for 300 h in 0.5 ppm NO 2 at 300 °C in (2000 response-recovery cycles). The sensor was stable up to 6 days (∼150 h) of continuous operation and degraded between 150–300 h. The morphology and surface properties of the WO 3 film were investigated with XRD, Raman spectroscopy, BET, SEM, TEM, and HRTEM. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nowadays, CdZnTe (CZT) is one of the key materials for the development of room temperature X-ray and gamma ray detectors and great efforts have been made on both the device and the crystal growth technologies. In this work, we present the results of spectroscopic investigations on new boron oxide encapsulated vertical Bridgman (B-VB) grown CZT detectors, recently developed at IMEM-CNR Parma, Italy. Several detectors, with the same electrode layout (gold electroless contacts) and different thicknesses (1 and 2.5 mm), were realized: the cathode is a planar electrode covering the detector surface (4.1×4.1 mm 2 ), while the anode is a central electrode (2×2 mm 2 ) surrounded by a guard-ring electrode. The detectors are characterized by electron mobility-lifetime product ( µ e τ e ) values ranging between 0.6 and 1·10 −3 cm 2 /V and by low leakage currents at room temperature and at high bias voltages (38 nA/cm 2 at 10000 V/cm). The spectroscopic response of the detectors to monochromatic X-ray and gamma ray sources ( 109 Cd, 241 Am and 57 Co), at different temperatures and fluxes (up to 1 Mcps), was measured taking into account the mitigation of the effects of incomplete charge collection, pile-up and high flux radiation induced polarization phenomena. A custom-designed digital readout electronics, developed at DiFC of University of Palermo (Italy), able to perform a fine pulse shape and height analysis even at high fluxes, was used. At low rates (200 cps) and at room temperature (T=25 °C), the detectors exhibit an energy resolution FWHM around 4% at 59.5 keV, for comparison an energy resolution of 3% was measured with Al/CdTe/Pt detectors by using the same electronics (A250F/NF charge sensitive preamplifier, Amptek, USA; nominal ENC of 100 electrons RMS). At high rates (750 kcps), energy resolution values of 7% and 9% were measured, with throughputs of 2% and 60% respectively. No radiation polarization phenomena were observed at room temperature up to 1 Mcps ( 241 Am source, 60 keV), while a detector collapse characterizes the samples at T <10 °C. Comparison with two traveling heater method (THM) grown CZT detectors (REDLEN, Canada), fabricated with the same electrode layout, is also presented. These activities are in the framework of an Italian research project on the development of energy-resolved photon counting (ERPC) systems for high flux energy-resolved X-ray imaging. [ABSTRACT FROM AUTHOR]

Present paper describes a method for obtaining the physical quantities characterizing single-events based on fitting experimental 2-D charge-profiles to two analytical models. First results are presented regarding a 10×10 LuYAP:Ce array of 2×2×10 mm 3 crystal pixels coupled to a H10966 Hamamatsu 8×8 multi-anode assembly under radio-isotopic irradiations and from self-activity. Results show that a photo multiplier tube with cross plate anode configuration would be preferable than a multi anode one due to uniformity, cost, and connections constraints. Among the results a plot of charge spread Vs. charge is to be cited because it was not yet published in scientific literature. [ABSTRACT FROM AUTHOR]

X’tal cube is the cubic depth of interaction (DOI) PET detector which our research group developed. In this work, aiming to get higher sensitivity, we developed the long rectangular shape X’tal cube (long-XC) by extending the cubic X’tal cube structure in one direction. We verified performance of this long-XC and also studied detector parameters for optimization. The same as the X’tal cube, the crystal block of the long-XC is composed of a 3D array of cubic scintillation crystal elements. Reflectors are not inserted between these crystal elements. The scintillation light then spreads without being obstructed by reflectors and is detected by multiple numbers of the multi-pixel photon counters (MPPCs) coupled on all six sides of the crystal block. For crystal element identification, a simple Anger-type calculation is used. In this study, we arranged 3.0 mm \times 3.0 mm \times 3.0 mm LGSO crystal elements in a 6\times 6\times 14 array for the long-XC. In a previous study, we had already confirmed that for the X’tal cube consisting of a 6\times 6\times 6 or 50\,\,\mu \text {m}\,\,\times 50\,\,\mu \text {m} pixel sizes; the material between the crystal elements, an air gap or an optical glue having a closer refractive index to that of LGSO than air has; and the MPPC signals used in the Anger-type calculation. Results of the crystal element identification performance showed that reducing the number of the edge MPPCs caused performance degradation only at the part near the edge. For the MPPC type, the 50~\mu \text {m} type was better than the 25~\mu \text m type, and for the material, air was much better than the optical glue. We found that the choice of MPPC signals for the Anger-type calculation was effective in the optical glue condition. For the long-XC in the air gap condition and using the 50~\mu \text m type MPPCs, we observed it had good performance and there was no significant degradation at the central part which is far from the edge MPPCs. For irradiation of 662 keV gamma-rays, we measured approximately 11 - 13 % energy resolution for each crystal element and there was only a small difference in light outputs between crystal elements at the central part and at the edges. These results at the central part suggested the possibility of further extension of the long-XC for higher sensitivity. [ABSTRACT FROM AUTHOR]

Despite the fact that timing capabilities for devices based on BGO are limited when compared with LYSO or LSO based systems, the cost of BGO is considerably lower and could thus, be an option for devices with high scintillator volumes (as in the case of nuclear medicine scanners), but also in smaller dedicated imagers. Recently, many studies have been carried out in order to determine the potential capabilities of BGO for PET and SPECT applications, where BGO scintillator crystals have been coupled to SiPM photosensor devices. However, so far these studies have only been done on small-size BGO samples. In this work, we have studied three different BGO size configurations, coupled to a \ 12 \times \ 12 low-noise SiPM array. Each SiPM has an active area of \ 3 \times \ 3\ \mm^2 with a pixel pitch of 4.2 mm. A special charge division network providing information for each row and column output of the SiPM array has been used. The first tested BGO configuration has 2.5 mm crystal pixel pitch and 10 mm thickness, while the second makes use of smaller 1.5 mm pixels with 1.67 mm pitch but only 3 mm thick. The third evaluated configuration provided limited photon depth of interaction (DOI) information by using two staggered layers of BGO pixels also with 2.5 mm pitch and with a total thickness of 20 mm. Performances of these configurations in terms of spatial and energy resolutions have been determined. Energy resolution as good as 14.2% was obtained. Our results indicate that single layer crystal arrays with pixel values as low as 1.5 mm or two staggered layers with 2.5 mm pitch are well suited for PET applications, such as low-cost and high performance dedicated PET systems or large systems. [ABSTRACT FROM AUTHOR]

Silicon photomultipliers (SiPMs) were considered as photodetectors in Cherenkov time-of-flight positron emission tomography (TOF PET) due to their relatively high photon detection efficiency (PDE) which resulted in a higher gamma detection efficiency of the Cherenkov PET detector. SiPMs produced by KETEK, AdvanSiD, SensL and Hamamatsu were tested in this application. The coincidence time resolution, gamma detection efficiency and single side event rates were measured in a simple experimental setup, consisting of two detectors placed in a coincidence configuration. The apparatus was cooled to - 25^ \circ C in order to reduce the SiPM dark count rates. A single side gamma detection efficiency of up to 26% was measured, which is a marked improvement over previous Cherenkov TOF PET measurements. The best measured coincidence time resolution of 297 ps FWHM was limited by the time response of the SiPMs used for this experiments. [ABSTRACT FROM AUTHOR]

In this paper, we present an innovative, fully integrated handheld gamma camera, namely designed to gather in the same device the gamma ray detector with the display and the embedded computing system. The low power consumption allows the prototype to be battery operated. To be useful in radioguided surgery, an intraoperative gamma camera must be very easy to handle since it must be moved to find a suitable view. Consequently, we have developed the first prototype of a fully integrated, compact and lightweight gamma camera for radiopharmaceuticals fast imaging. The device can operate without cables across the sterile field, so it may be easily used in the operating theater for radioguided surgery. The prototype proposed consists of a Silicon Photomultiplier (SiPM) array coupled with a proprietary scintillation structure based on CsI(Tl) crystals. To read the SiPM output signals, we have developed a very low power readout electronics and a dedicated analog to digital conversion system. One of the most critical aspects we faced designing the prototype was the low power consumption, which is mandatory to develop a battery operated device. We have applied this detection device in the lymphoscintigraphy technique (sentinel lymph node mapping) comparing the results obtained with those of a commercial gamma camera (Philips SKYLight). The results obtained confirm a rapid response of the device and an adequate spatial resolution for the use in the scintigraphic imaging. This work confirms the feasibility of a small gamma camera with an integrated display. This device is designed for radioguided surgery and small organ imaging, but it could be easily combined into surgical navigation systems. [ABSTRACT FROM AUTHOR]

The hard X-ray Imager and Soft Gamma-ray Detector onboard ASTRO-H demonstrate high sensitivity to hard X-ray (5–80 keV) and soft gamma-rays (60–600 keV), respectively. To reduce the background, both instruments are actively shielded by large, thick Bismuth Germanate scintillators. We have developed the signal processing system of the avalanche photodiode in the BGO active shields and have demonstrated its effectiveness after assembly in the flight model of the HXI/SGD sensor and after integration into the satellite. The energy threshold achieved is about 150 keV and anti-coincidence efficiency for cosmic-ray events is almost 100%. Installed in the BGO active shield, the developed signal processing system successfully reduces the room background level of the main detector. [ABSTRACT FROM AUTHOR]

The variation in intensity of 1.78 MeV silicon, 6.13 MeV oxygen, and 2.22 MeV hydrogen prompt gamma rays from soil samples due to the addition of 5.1, 7.4, 9.7, 11.9 and 14.0 wt% water was studied for 14 MeV incident neutron beams utilizing a LaBr 3 :Ce gamma ray detector. The intensities of 1.78 MeV and 6.13 MeV gamma rays from silicon and oxygen, respectively, decreased with increasing sample moisture. The intensity of 2.22 MeV hydrogen gamma rays increases with moisture. The decrease in intensity of silicon and oxygen gamma rays with moisture concentration indicates a loss of 14 MeV neutron flux, while the increase in intensity of 2.22 MeV gamma rays with moisture indicates an increase in thermal neutron flux due to increasing concentration of moisture. The experimental intensities of silicon, oxygen and hydrogen prompt gamma rays, measured as a function of moisture concentration in the soil samples, are in good agreement with the theoretical results obtained through Monte Carlo calculations. [ABSTRACT FROM AUTHOR]

Some of the more attractive semiconducting compounds for ambient temperature radiation detector applications are impacted by low charge collection efficiency due to the presence of point and volumetric defects. This has been particularly true in the case of BiI3, which features very attractive properties (density, atomic number, band gap, etc.) to serve as a gamma ray detector, but has yet to demonstrate its full potential. We show that by applying growth techniques tailored to reduce defects, the spectral performance of this promising semiconductor can be realized. Gamma ray spectra from >100 keV source emissions are now obtained from high quality Sb:BiI3 bulk crystals with limited concentrations of defects (point and extended). The spectra acquired in these high quality crystals feature photopeaks with resolution of 2.2% at 662 keV. Infrared microscopy is used to compare the local microstructure between radiation sensitive and non-responsive crystals. This work demonstrates that BiI3 can be prepared in melt-grown detector-grade samples with superior quality and can acquire the spectra from a variety of gamma ray sources. [ABSTRACT FROM AUTHOR]

Antimony (Sb) doped bismuth tri-iodide (BiI 3 ) radiation detectors were fabricated from large single crystals that were grown using the modified vertical Bridgman technique. Detectors were prepared by subjecting the crystal surfaces to different mechanical and chemical treatments. Surface quality of the detectors was evaluated using optical microscopy. The influence of surface quality on detector performance was analyzed by measuring the leakage current for each of the detectors. The radiation response of the detectors was measured using an Americium ( 241 Am) gamma-ray source at room temperature. The first successful use of BiI 3 detectors for gamma-ray spectroscopy is reported here with energy resolution of 7.5% at 59.5 keV. The mobility-lifetime product for electrons was also estimated to be about 5.2 × 10 −4 cm 2 /V. [ABSTRACT FROM AUTHOR]

H2/Ar electron cyclotron resonance plasma processing of the high-resistivity (111) CdTe crystals was studied to find its effect on the leakage current and the gamma ray detection properties of the detectors. All the crystals were chemically etched in a bromine–methanol (BM) solution prior to the plasma processing to obtain a smooth surface. A remarkable reduction in both the surface and the bulk leakage current was observed in the plasma processed detectors when compared with the unprocessed one. The gamma detection property of the detectors, both the spectral resolution and the peak shape, was also significantly improved. X-ray photoelectron spectroscopy confirmed that an excess Te-rich surface layer was present on the BM etched crystal, however, such layer was removed, and the surface atomic ratio was modified after the plasma processing. The improvement in the detector performance could be related to the change in the surface chemical states of the crystals. Hence, this could be a promising process for improving the detectors performance and their stabilities. [ABSTRACT FROM PUBLISHER]

The bias-induced instability of the internal electric field in Ohmic-type CdTe gamma-ray detectors is investigated by using the time-of-flight technique. Based on the solution of one dimensional Poisson equation, transient current waveforms at different delays of laser excitation from the bias application and at different temperatures are analysed It is shown that under DC bias application, the internal electric field decreases with depth because of the positive space charge buildup in the detectors. Further, the origin of the space charge is attributed to the injection and successive trapping of holes from the anode side at the early stage of evolution and then later to the thermal release of electrons from a deep donor at 0.64 eV. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

This study assesses the terrestrial gamma radiation dose rates from the naturally occurring radionuclides in the lignite coalfield of Ilgın district of Konya. The measurements were performed above the surface soil using NaI(Tl) gamma-ray detector. The average external annual effective doseswere also calculated using these terrestrial gamma radiation dose rates for each measurement location. [ABSTRACT FROM AUTHOR]

Purpose: To determine the effectiveness of FDG-PET/CT in the assessment of inguinofemoral lymph node (IFLN) in patients with vulvar cancer by comparing FDG-PET/CT results, sentinel lymph node (SLN) screening with gamma probe, and the results of frozen section and definitive pathology in these lymph nodes.Study Design: This prospective study included eight patients, who were diagnosed with vulvar cancer at the Gynecology and Obstetrics Department of Erciyes University, Turkey. All patients underwent FDG-PET/CT before surgery. Local excision and IFLN dissection were planned by assessing IFLN involvement with SLN screening with Tc-99m nanocolloid plus frozen section. Intraoperatively, SLN screening was performed by using a gamma probe, and these lymph nodes were excised and then evaluated by frozen section. Regardless of the frozen section results, the IFLNs were totally excised. The FDG-PET/CT scan results, SLN plus frozen section results and definitive pathology results of the inguinal lymph nodes were compared.Results: The mean age was 64.50 ± 13.25 years (min-max 43-79 years). All tumors were squamous cell carcinomas. FDG-PET/CT scan determined vulvar lesions accurately in all patients (8/8; 100 %). When inguinal lymph nodes were assessed by FDG uptake and SUVmax values, lymph nodes were interpreted as reactive in four patients (4/8; 50 %) and metastatic in the others (4/8; 50 %). In all patients frozen section confirmed the FDG-PET-CT results and definitive histopathology results confirmed the frozen section and FDG-PET-CT results (8/8; 100 %).Conclusions: In light of these data, FDG-PET/CT scanning is an effective method for the detection of primary tumor in vulvar cancer. Although it seems to be an effective method for the detection of IFLN metastasis, these findings must be supported by further studies with larger sample size for use in the planning of primary surgery and inguinal lymph node dissection without SLN dissection and frozen section, as a minimal invasive method. [ABSTRACT FROM AUTHOR]

Factors to convert the count rate of a NaI(Tl) scintillation detector to the concentration of radioactive cesium in marine sediments are estimated for a towed gamma-ray detector system. The response of the detector against a unit concentration of radioactive cesium is calculated by Monte Carlo radiation transport simulation considering the vertical profile of radioactive material measured in core samples. The conversion factors are acquired by integrating the contribution of each layer and are normalized by the concentration in the surface sediment layer. At the same time, the uncertainty of the conversion factors are formulated and estimated. The combined standard uncertainty of the radioactive cesium concentration by the towed gamma-ray detector is around 25 percent. The values of uncertainty, often referred to as relative root mean squat errors in other works, between sediment core sampling measurements and towed detector measurements were 16 percent in the investigation made near the Abukuma River mouth and 5.2 percent in Sendai Bay, respectively. Most of the uncertainty is due to interpolation of the conversion factors between core samples and uncertainty of the detector׳s burial depth. The results of the towed measurements agree well with laboratory analysed sediment samples. Also, the concentrations of radioactive cesium at the intersection of each survey line are consistent. The consistency with sampling results and between different lines׳ transects demonstrate the availability and reproducibility of towed gamma-ray detector system. [ABSTRACT FROM AUTHOR]

An improved threshold shift-invariant wavelet transform de-noising algorithm for high-resolution gamma-ray spectroscopy is proposed to optimize the threshold function of wavelet transforms and reduce signal resulting from pseudo-Gibbs artificial fluctuations. This algorithm was applied to a segmented gamma scanning system with large samples in which high continuum levels caused by Compton scattering are routinely encountered. De-noising data from the gamma ray spectrum measured by segmented gamma scanning system with improved, shift-invariant and traditional wavelet transform algorithms were all evaluated. The improved wavelet transform method generated significantly enhanced performance of the figure of merit, the root mean square error, the peak area, and the sample attenuation correction in the segmented gamma scanning system assays. We also found that the gamma energy spectrum can be viewed as a low frequency signal as well as high frequency noise superposition by the spectrum analysis. Moreover, a smoothed spectrum can be appropriate for straightforward automated quantitative analysis. [ABSTRACT FROM AUTHOR]

Plastic scintillators are often used as detectors in High Energy Physics (HEP), but have insufficient radiation hardness. Organization of better light collection inside a single detector may prolong operation life of scintillators. A finger-strip plastic scintillator option has many advantages to keep the excellent detector performance at high luminosity. Measurements assigned to show an advantage of a stripped detector vs. the un-stripped one in the range of increased absorbed doses and the smallest dose rates have been performed. This method has proved to be a good upgrade strategy. [ABSTRACT FROM AUTHOR]

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%. [ABSTRACT FROM AUTHOR]

Particle induced gamma-ray emission (PIGE) is an ion beam technique used for isotopic elemental analysis of materials, based on gamma-ray spectroscopy. In the traditional PIGE setup, the gamma-ray detector is positioned at the neutral angles 55° or 125° with respect to the beam direction in order to measure gamma-rays with different angular distributions. Although these angles permit measurements without an a-priori knowledge of the specific angular distributions, this choice is not efficient if one wants to identify a specific element since a longer acquisition time is needed. In this work, we propose to optimize the PIGE measurements by choosing the detector angle position due to the previous knowledge of the gamma-ray multipolarity and the nuclear reaction. We present the angular distribution calculations for the isotopes most frequently identified by PIGE analysis, specially in Cultural Heritage objects. Calculations demonstrate that a gain in the intensity up to 70% can be achieved allowing the elemental identification in shorter times. This result is promising and represents a more efficient alternative to perform PIGE measurements. [ABSTRACT FROM AUTHOR]

A gamma ray camera is built for the DIII-D tokamak [J. Luxon, Nucl. Fusion 42, 614 (2002)] that provides spatial localization and energy resolution of gamma flux by combining a lead pinhole camera with custom-built detectors and optimized viewing geometry. This diagnostic system is installed on the outer midplane of the tokamak such that its 123 collimated sightlines extend across the tokamak radius while also covering most of the vertical extent of the plasma volume. A set of 30 bismuth germanate detectors can be secured in any of the available sightlines, allowing for customizable coverage in experiments with runaway electrons in the energy range of 1-60 MeV. Commissioning of the gamma ray imager includes the quantification of electromagnetic noise sources in the tokamak machine hall and a measurement of the energy spectrum of background gamma radiation. First measurements of gamma rays coming from the plasma provide a suitable testbed for implementing pulse height analysis that provides the energy of detected gamma photons. [ABSTRACT FROM AUTHOR]

Design of a new type of neutron detector, consisting of a fast neutron converter, plastic scintillator, and Cherenkov detector, to discriminate 14-MeV fast neutrons and gamma rays in a pulsed n – γ mixed field and monitor their neutron fluxes is reported in this study. Both neutrons and gamma rays can produce fluorescence in the scintillator when they are incident on the detector. However, only the secondary charged particles of the gamma rays can produce Cherenkov light in the Cherenkov detector. The neutron and gamma-ray fluxes can be calculated by measuring the fluorescence and Cherenkov light. The GEANT4 Monte Carlo simulation toolkit is used to simulate the whole process occurring in the detector, whose optimum parameters are known. Analysis of the simulation results leads to a calculation method of neutron flux. This method is verified by calculating the neutron fluxes using pulsed n – γ mixed fields with different n / γ ratios, and the results show that the relative errors of all calculations are <5%. [ABSTRACT FROM AUTHOR]

We present the results of the first high-altitude balloon flight test of a concept for an advanced Compton telescope making use of modern scintillator materials with silicon photomultiplier (SiPM) readouts. There is a need in the fields of high-energy astronomy and solar physics for new medium-energy gamma-ray (~0.4–10 MeV) detectors capable of making sensitive observations of both line and continuum sources over a wide dynamic range. A fast scintillator-based Compton telescope with SiPM readouts is a promising solution to this instrumentation challenge, since the fast response of the scintillators permits both the rejection of background via time-of-flight (ToF) discrimination and the ability to operate at high count rates. The Solar Compton Telescope (SolCompT) prototype presented here was designed to demonstrate stable performance of this technology under balloon-flight conditions. The SolCompT instrument was a simple two-element Compton telescope, consisting of an approximately one-inch cylindrical stilbene crystal for a scattering detector and a one-inch cubic LaBr 3 :Ce crystal for a calorimeter detector. Both scintillator detectors were read out by 2×2 arrays of Hamamatsu S11828-3344 MPPC devices. Custom front-end electronics provided optimum signal rise time and linearity, and custom power supplies automatically adjusted the SiPM bias voltage to compensate for temperature-induced gain variations. A tagged calibration source, consisting of ~240 nCi of 60 Co embedded in plastic scintillator, was placed in the field of view and provided a known source of gamma rays to measure in flight. The SolCompT balloon payload was launched on 24 August 2014 from Fort Sumner, NM, and spent ~3.75 h at a float altitude of ~123,000 ft. The instrument performed well throughout the flight. After correcting for small (~10%) residual gain variations, we measured an in-flight ToF resolution of ~760 ps (FWHM). Advanced scintillators with SiPM readouts continue to show great promise for future gamma-ray instruments. [ABSTRACT FROM AUTHOR]

The appropriate gamma-ray detector shielding configuration is critical for a precise prompt gamma neutron activation analysis (PGNAA) measurement. The shielding material has to prevent the radiation damage to the detector crystal and it must produce less activation gamma rays, whether prompt or delayed, which may interfere the gamma ray spectrum of the sample. In this research, using common shielding materials, a number of combinations have been studies to form a 50 cm long shield for portable PGNAA system against both fast and slow neutrons as well as gamma rays emitted by 20Ci Am–Be source. The measurement results show that in contrast with conventional shadow cone in which the shielding material starts with 20 cm heavy metals such as iron and ends with 30 cm polymer materials, in portable PGNAA systems, the shielding material gives better results if it starts with about 40 cm borated polymer material and ends with an appropriate thickness (7 cm to 10 cm) of heavy metal such as tungsten. [ABSTRACT FROM AUTHOR]

We investigated the feasibility of long-drift-time CdZnTe (CZT) gamma-ray detectors, fabricated from CZT material produced by Redlen Technologies. CZT crystals with cross-section areas of 5 × 5mm² and 6 × 6mm² and thicknesses of 20-, 30-, 40-, and 50-mm were configured as 3D position-sensitive drift detectors and were read out using a front-end ASIC. By correcting the electron charge losses caused by defects in the crystals, we demonstrated high performance for relatively thick detectors fabricated from unselected CZT material. [ABSTRACT FROM AUTHOR]

The crystal Cs 2 LiYCl 6 :Ce (CLYC) is a very interesting scintillator material because of its good energy resolution and its capability to identify γ-rays and fast/thermal neutrons. The crystal Cs 2 LiYCl 6 :Ce contains 6 Li and 35 Cl isotopes, therefore, it is possible to detect thermal neutrons through the reaction 6 Li(n, α)t while 35 Cl ions allow to measure fast neutrons through the reactions 35 Cl(n, p) 35 S and 35 Cl(n, α) 32 P. In this work two CLYC 1″×1″ crystals were used: the first crystal, enriched with 6 Li at 95% (CLYC-6) is ideal for thermal neutron measurements while the second one, enriched with 7 Li at >99% (CLYC-7) is suitable for fast neutron measurements. The response of CLYC scintillators was measured with different PMT models: timing or spectroscopic, with borosilicate glass or quartz window. The energy resolution, the neutron-γ discrimination and the internal activity are discussed. The capability of CLYC scintillators to discriminate γ rays from neutrons was tested with both thermal and fast neutrons. The thermal neutrons were measured with both detectors, using an AmBe source. The measurements of fast neutrons were performed at the Frascati Neutron Generator facility (Italy) where a deuterium beam was accelerated on a deuterium or on a tritium target, providing neutrons of 2.5 MeV or 14.1 MeV, respectively. The different sensitivity to thermal and fast neutrons of a CLYC-6 and of a CLYC-7 was additionally studied. [ABSTRACT FROM AUTHOR]

Purpose: Respiratory motion can lead to treatment errors in the delivery of radiotherapy treatments. Respiratory gating can assist in better conforming the beam delivery to the target volume. We present a study of the technical aspects of a real time positron emission tracking system for potential use in gated radiotherapy. Methods: The tracking system, called PeTrack, uses implanted positron emission markers and position sensitive gamma ray detectors to track breathing motion in real time. PeTrack uses an expectation-maximization algorithm to track the motion of fiducial markers. A normalized least mean squares adaptive filter predicts the location of the markers a short time ahead to account for system response latency. The precision and data collection efficiency of a prototype PeTrack system were measured under conditions simulating gated radiotherapy. The lung insert of a thorax phantom was translated in the inferior-superior direction with regular sinusoidal motion and simulated patient breathing motion (maximum amplitude of motion ±10 mm, period 4 s). The system tracked the motion of a 22Na fiducial marker (0.34 MBq) embedded in the lung insert every 0.2 s. The position of the was marker was predicted 0.2 s ahead. For sinusoidal motion, the equation used to model the motion was fitted to the data. The precision of the tracking was estimated as the standard deviation of the residuals. Software was also developed to communicate with a Linac and toggle beam delivery. In a separate experiment involving a Linac, 500 monitor units of radiation were delivered to the phantom with a 3?3 cm photon beam and with 6 and 10 MV accelerating potential. Radiochromic films were inserted in the phantom to measure spatial dose distribution. In this experiment, the period of motion was set to 60 s to account for beam turn-on latency. The beam was turned off when the marker moved outside of a 5-mm gating window. Results: The precision of the tracking in the IS direction was 0.53 mm for a sinusoidally moving target, with an average count rate ~250 cps. The average prediction error was 1.1±0.6 mm when the marker moved according to irregular patient breathing motion. Across all beam deliveries during the radiochromic film measurements, the average prediction error was 0.8±0.5 mm. The maximum error was 2.5 mm and the 95th percentile error was 1.5 mm. Clear improvement of the dose distribution was observed between gated and nongated deliveries. The full-width at halfmaximum of the dose profiles of gated deliveries differed by 3 mm or less than the static reference dose distribution. Monitoring of the beam on/off times showed synchronization with the location of the marker within the latency of the system. Conclusions: PeTrack can track the motion of internal fiducial positron emission markers with submillimeter precision. The system can be used to gate the delivery of a Linac beam based on the position of a moving fiducial marker. This highlights the potential of the system for use in respiratory-gated radiotherapy. [ABSTRACT FROM AUTHOR]

Gamma-ray detectors are widely used in many fields like environmental measurements, medicine, space science, and industry, where the detector geometrical, total, photopeak efficiencies and peakto-total ratio could be required. The calculation of the detector efficiency depends mainly on the value of the geometrical efficiency, which depends on the solid angle subtended by the source-detector system. The present work introduces a direct analytical method to calculate the geometrical and total efficiencies of CdZnTe gamma-ray detector using off-axis isotropic radiating γ-ray [point, disk, and cylindrical] sources. To test the validity of the present work, the results are compared with some published data and also to prove how much it is important to determine the efficiency of difficult gammaray detection arrangement. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

Helium-4-based fast neutron scintillation detectors are an attractive alternative to pulse-shape discrimination-capable organic scintillators for fast neutron detection and spectroscopy, as the response of the detectors to gamma rays is intrinsically limited to low energy deposition. Consequently, the neutron recoil distribution can be measured with these detectors without the need for pulse shape analysis. In this work, the response of an Arktis S670 4He scintillation detector to D-D, D-T, and 252Cf neutrons was measured. The detector has a unique construction and readout mechanism, with multiple output channels observing the same scintillation event, and an analysis method was developed to aggregate the outputs from all channels into a single list. The D-D and D-T neutron responses were used to perform a two-point energy calibration, which yielded a near-zero intercept, suggesting that the 4He scintillation medium behaves linearly to a higher energy than previously reported, and that a two-point calibration is sufficient for nuclear recoil energies below 9 MeV. Furthermore, the detector was measured to have 16.7-ns FWHM time resolution when using the developed custom analysis, a reduction of 4.9 ns when compared to the conventional pulse analysis. [ABSTRACT FROM AUTHOR]

BiI 3 single crystals were grown by the physical vapor transport method. The repeated sublimation of the starting material reduced impurities in the BiI 3 single crystal to sub-ppm levels. The detector was fabricated by depositing Au electrodes on both surfaces of the 100-μm-thick BiI 3 single crystal platelet. The resistivity of the BiI 3 single crystal was increased by post-annealing in an iodine atmosphere ( ρ =1.6×10 11 Ω cm). Pulse height spectroscopy measurements showed clear peaks in the energy spectrum of alpha particles or gamma rays. It was estimated that the mobility-lifetime product was μ e τ e =3.4–8.5×10 −6 cm 2 /V and the electron–hole pair creation energy was 5.8 eV. Our results show that BiI 3 single crystals are promising candidates for detectors used in radiographic imaging or gamma ray spectroscopy. [ABSTRACT FROM AUTHOR]