Search

Upward Terrestrial Gamma‐Ray Flashes (TGFs) are mainly produced during the upward propagating negative leaders inside thunderclouds. The exact source position of TGFs, which is crucial to understanding TGF source properties, is still unclear. The link between positive energetic in‐cloud pulses (+EIPs) and TGFs provides us with a potential target to aim at. In this study, the low‐frequency radio emissions of 75 +EIPs are analyzed to retrieve the source altitudes with an improved ray theory model. Furthermore, the meteorology contexts of +EIPs derived from the ground‐based weather radars and satellite‐based infrared cloud top temperature measurements are investigated. +EIPs are produced at 8.8–13.7 km, with an average of 11.3 km inside thunderclouds, and at an average of ∼2.5 km below cloud tops. These altitudes indicate that a total number of 1.7 × 1016 to 2.6 × 1018 gamma ray photons with energy greater than 1 MeV are required for an EIP‐TGF to be measured by spaceborne detectors. Plain Language Summary: Terrestrial gamma‐ray flashes (TGFs) are high‐energy photon emissions generated during thunderstorms and related to the initial development of intra‐cloud discharges. How TGFs are produced inside thunderclouds is still an open question, and one crucial issue is where TGFs are produced. Till now, it has been challenging to obtain the TGF positions directly. Recently, a distinct type of high‐peak current events, which are named energetic in‐cloud pulses (EIPs), are found to be closely linked to TGFs. The radio emissions of EIPs can be measured by ground‐based radio sensors deployed hundreds of kilometers away from the source. In this study, a ray theory model is improved to retrieve the signature of very low‐frequency/low‐frequency radio signals of EIPs propagating in the Earth‐ionosphere waveguide to obtain the source altitudes of EIPs. A total of 75 EIPs were found to be produced at 8.8–13.7 km, with an average of 11.3 km inside thunderclouds, and at an average of ∼2.5 km below cloud tops. With the source position information and combining the previously reported method to estimate the total number of source electrons, we suggest a total number of about 1017 is needed for TGFs being detected by spaceborne gamma ray detectors. Key Points: An improved ray theory model is developed to retrieve energetic in‐cloud pulse (EIP) positionsSeventy‐five +EIPs are located at 8.8–13.7 km, with a mean altitude of 11.3 kmA mean gap of ∼2.5 km between EIPs and cloud tops was estimated [ABSTRACT FROM AUTHOR]

The integration of the ORION digital signal processing-based MCA system coupled with a 3″ × 3″ NaI(Tl) detector assembly with a GM detector for counting beta (β) has eliminated the need for a standalone β-γ method in which U3O8 is determined by gross β and gross γ counting. Uraniferous and mixed U-Th samples were taken up for study and compared with the results obtained from Canberra p-type coaxial high resolution gamma ray spectrometry detector. In uraniferous samples, U3O8 values obtained are within ±10%, whereas in the case of mixed U-Th samples, U3O8 values are within ±15%. Regression graphs drawn between the outcomes from the two analytical systems indicate R2 > 0.95 for Ra(eU3O8) and ThO2. In uraniferous samples, the R2 value for U3O8 was found to be > 0.99, but in mixed U-Th samples, it is 0.92. The closeness of agreement between the results obtained from two methods at various concentrations over the analytical range shows that the integrated system is suitable for the quantitative determination of eU3O8, U3O8, Ra(eU3O8), ThO2 and K in geological rock samples. [ABSTRACT FROM AUTHOR]

In the present study, the highly recommended lead iodide (PbI2) nanoparticles and thin films based on PbI2 nanoparticles have been prepared for optoelectronics and solar cell applications. PbI2 is an anisotropic p-type semiconductor with a band gap of 2.57 eV at room temperature. PbI2 material has large potential applications in optical detector, digital X-ray imaging, gamma ray detector, etc. PbI2 layered semiconductor nanoparticles were stabilized using thioglycerol and investigated by Ultraviolet-Visible (UV-Vis) absorption spectroscopy, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The chemical bath deposition (CBD) method was used to deposit PbI2 thin films on fluorine-doped tin oxide (FTO) glass substrates. These films were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), mapping and atomic force microscopy (AFM). The thicknesses of the PbI2 thin films were estimated using a laser profilometer. The blue shift was observed in UV-Vis absorption and PL spectra of PbI2 nanoparticles. TEM was used to obtain quantitative information on the PbI2 particle size distribution. Due to the low solubility of PbI2 in acetonitrile, approximately 20-30 nm sized circular particles are obtained. The variation of 18 Å was observed in the lateral dimensions of PbI2 nanoparticles. Pb4fXPS core level appeared at 138.5 eV corresponding to PbI2. There is no report published wherein the PbI2 nanoparticles and the PbI2 thin films were prepared by the aqueous chemical method and the CBD method respectively. In this study, the characterization results of PbI2 nanoparticles and PbI2 thin films were better than many other materials. [ABSTRACT FROM AUTHOR]

In recent years, rare earth silicate compounds have attracted the extensive attention of researchers owing to their potential for applications in scintillation crystals in gamma ray or X-ray detectors, as well as in thermal or environmental barrier coatings. Large high quality crystals of three members of the rare earth monosilicates family of compounds, R 2 SiO 5 (with R = Dy, Ho, and Er), have been grown by the floating zone method, using a laser-diode-heated floating zone furnace. Crystal growths attempts were carried out using different parameters in order to determine the optimum conditions for the growth of these materials. The phase purity and the crystalline quality of the crystal boules were analysed using powder and Laue X-ray diffraction. Single crystal X-ray diffraction experiments were carried out to determine the crystal structures of the boules. The optimum conditions used for the crystal growth of R 2 SiO 5 materials are reported. The phase purity and high crystalline quality of the crystals produced makes them ideal for detailed investigations of the intrinsic physical and chemical properties of these materials. [ABSTRACT FROM AUTHOR]

Scientific payloads onboard CubeSats usually have complex geometries and occasionally narrower allowed temperature ranges with respect to the rest of the spacecraft. In these cases, the capability to correctly predict the thermal behaviour of the payload once in orbit is mandatory. To achieve this ability, a thermal balance test is required to correctly identify the thermal model of the payload. The test consists in the application of different external thermal boundary conditions together with the addition of heat dissipation to simulate the thermal load produced by active electronics during operation. Those experimental data are fundamental to validate the numerical thermal model and make its predictions reliable. This paper presents the configuration and procedures of the thermal balance test performed on the Demonstration Model of the payload to be embarked on each satellite of the HERMES constellation. The test data is compared with the results of a finite volume thermal model of the payload, proving the application of this method to be reliable for space thermal analyses. The obtained test results show the temperature jumps caused by the heat dissipation applied to active components. A weak correlation between the payload interface and internal equipment has been observed, thus proving that the payload is almost decoupled from the Service Module temperature variations. Based on test outcomes, some modifications in the payload design have been implemented, with the aim to lower the operative temperature on critical, temperature-sensitive equipment. [ABSTRACT FROM AUTHOR]

Recently, there has been considerable interest in x-ray and gamma ray detectors with large volume and high energy resolution that operate at room temperature. To improve detector energy resolution, the carrier mobility-lifetime product needs to be increased, and the electronic trap state concentration needs to be minimized. Defect concentrations in the part per billion range can alter the charge transport and carrier recombination lifetime. In this work, thermally stimulated current spectroscopy measurements were systematically carried out in bulk halide perovskite single crystals of CsPbBr3 over a temperature range of 80–320 K. The origins and trap parameters of CsPbBr3 crystals from the solution growth and melt growth procedures were determined and compared. Trap concentrations were ranged from 1 × 1011 to 1 × 1016 cm−3. Appreciable detector performance was observed for CsPbBr3 crystals with trap concentrations less than 1 × 1014 cm−3. The comparison of spectral responses of crystal samples grown using two different methods shows that, after purification, solution-grown crystals are comparable to melt-grown crystals in terms of low defect concentration and improved detector performance. For an improved mobility-lifetime product and enhanced spectral response to high energy radiation from fissile materials, trap states in either type of a crystal ingot must be reduced closer to 1011 cm−3. [ABSTRACT FROM AUTHOR]

The Gamma Ray Imager (GRI) is a pinhole camera providing 2D imaging of MeV hard x-ray (HXR) bremsstrahlung emission from runaway electrons (REs) over the poloidal cross section of the DIII-D tokamak. We report a series of upgrades to the GRI expanding the access to RE scenarios from the diagnosis of a trace amount of REs to high flux HXR measurements during the RE plateau phase. We present the implementation of novel gamma ray detectors based on LYSO and YAP crystals coupled to multi-pixel photon counters, enabling a count rate in excess of 1 MHz. Finally, we highlight new insights into the RE physics discovered during the current quench and RE plateau phase experiments as the result of these upgrades. [ABSTRACT FROM AUTHOR]

Background: Radiotracer extravasations, caused largely by faulty tracer injections, can occur in up to 23% of 18F-fluorodeoxyglucose (FDG) PET/CT scans and negatively impact radiological review and tracer quantification. Conventional radiological assessment of extravasation severity on PET has limited performance (e.g., extravasations frequently resolve before scanning) and practical drawbacks. In this study, we develop a new topical detector-based FDG extravasation severity classifier, calibrated from semi-quantitative PET measurements, and assess its performance on human subjects. Methods: A retrospective study examined patients whose FDG injections had been monitored as part of their standard workup for PET/CT imaging. Topical uncollimated gamma ray detectors were applied proximal to the injection site and on the same location on the opposing arm, and readings were acquired continuously during radiotracer uptake. Patients were imaged with their arms in the PET field of view and total extravasation activity quantified from static PET images through a volume of interest approach. The image-derived activities were considered ground truth and used to calibrate and assess quantification of topical detector readings extrapolated to the start of PET imaging. The classifier utilizes the calibrated detector readings to produce four extravasation severity classes: none, minor, moderate, and severe. In a blinded study, a radiologist qualitatively labeled PET images for extravasation severity using the same classifications. The radiologist's interpretations and topical detector classifications were compared to the ground truth PET results. Results: Linear regression of log-transformed image-derived versus topical detector tracer extravasation activity estimates showed a strong correlation (R2 = 0.75). A total of 24 subject scans were cross-validated with the quantitatively based classifier through a leave-one-out methodology. For binary classification (none vs. extravasated), the topical detector classifier had the highest overall diagnostic performance for identifying extravasations. Specificity, sensitivity, accuracy, and positive predictive value were 100.0%, 80.0%, 95.8%, and 100.0%, respectively, for the topical detector classifier and 31.6%, 100.0%, 45.8%, and 27.8%, respectively, for the radiological analysis. The topical detector classifier, with an optimal detection threshold, produced a significantly higher Matthews correlation coefficient (MCC) than the radiological analysis (0.87 vs. 0.30). Conclusions: The topical detector binary classifier, calibrated using quantitative static PET measurements, significantly improves extravasation detection compared to qualitative image analysis. [ABSTRACT FROM AUTHOR]

Inorganic lead-halide perovskite, cesium lead bromide (CsPbBr3), shows outstanding optoelectronic properties. Both solution- and melt-based methods have been proposed for CsPbBr3 crystal growth. The solution-based growth was done at low-temperature, whereas the melt-based growth was done at high-temperature. However, the comparison of optical, physical, and defect states using these two different growth conditions has been scarcely studied. Here, we have compared the thermal and optical properties of solution-grown and melt-grown single crystals of CsPbBr3. Positron Annihilation Lifetime Spectroscopy (PALS) analysis showed that melt-grown crystal has a relatively smaller number of defects than the chemical synthesis method. In addition, crystals grown using the chemical method showed a higher fluorescence lifetime than melt-grown CsPbBr3. [ABSTRACT FROM AUTHOR]

An experimental method was described to calibrate the depth of interaction (DOI) of high-energy $\gamma $ -ray in large-size thick pixel CdZnTe detector. The experimental results indicated that the ratio of the cathode and anode amplitude strongly showed linear relationship with the DOI of incidence $\gamma $ -rays and the detector. The correlation coefficients were optimized. Based on the experimental calibration of DOI, the photoelectric effect signals from the depth range where the energy resolution and the photopeak location are high were screened out to draw the energy spectrum. In this way, the energy resolution of the CdZnTe pixel detector was improved to 0.707% for 137Cs@662 keV. Further combined with the anode rise time, the electron mobility of CdZnTe in 2-D (1 mm accuracy) and 3-D (2 mm $\times $ 2 mm $\times $ 1 mm accuracy) scales was calculated. At different pixel positions and depths in CdZnTe detector, the electron mobility varies between 1000 and 1150 cm2/($\text{V}\cdot \text{s}$). [ABSTRACT FROM AUTHOR]

The article focuses on the U.S. Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E) funding for Low-Energy Nuclear Reactions (LENR) research projects. Eight research teams have received funding to explore LENR as a potentially transformative carbon-free energy source. The projects will investigate various aspects of LENR, including optimizing cathode design, detecting nuclear reactions in metal hydrides, measuring neutron emissions, and exploring nuclear anomalies.

A systematic study of the distribution of the Naturally Occurring Radioactivity in stone dust and crushed stone, has been carried out with an objective of establishing reliable baseline data on the radiation level and hence to evaluate hazard indices approach and the production of radioactive heat (RHP) due to radiation exposure to the workers and to the inhabitants of the studied area. Twenty-six samples have been collected from different locations in the State of Rio de Janeiro (Brazil). To calculate the specific activity, gamma ray spectrometry and a detector of High Purity Germanium (HPGe; Canberra, 30% relative efficiency) was used. The activity concentration of 238U, 226Ra 232Th and 40K ranged from 29.3 ± 18.6 to 206.8 ± 21.5 Bq kg−1, 30.3 ± 1.0 to 134.3 ± 1.8, 27.9 ± 0.7 to 86.2 ± 0.9 Bq kg−1, and 734.9 ± 35.1 to 1204.8 ± 53.5 Bq kg−1, respectively. The mean values of the I ex , I in , I γ , I α , A UI , I RP112Rn , I PA , I PI and I Yu indices were 0.68 ± 0.09, 0.92 ± 0.12, 0.93 ± 0.12, 0.43 ± 0.07, 0.88 ± 0.20, 1.25 ± 0.21, 0.34 ± 0.05, 0.75 ± 0.10, 0.63 ± 0.08 and 34. ± 6.31, respectively. The average radioactive heat production (RHP) of 2.01 ± 0.28 μ Wm−3 was above the values found in the literature, which may contribute to the heat flow in the study area because the raw materials that make up the samples showed a high value of environmental radioactivity. The Brazilian Hazard Index to assess the radiological risk of crushed stone and stone dust was created and the average value was 0.74 ± 0.10, a value below 1, which means only moderate control over the use of these materials, with no indication of restriction to the its use. • High-res gamma spectrometer measured levels of natural radionuclides in stone dust, crushed stone. • Study assesses radionuclide exposure risks in building materials, safety for workers & residents. • Research helps build database to minimize ionizing radiation damage, inform public policy. • A Brazilian Risk Index for samples was created to better adapt to the reality of using these materials in Brazil. [ABSTRACT FROM AUTHOR]

In this work, the attenuation capability of new Borate-based-glass system reinforced with titanium oxide containing PbO, CaO, TiO 2 and B 2 O 3 with different percentages was determined. Four different glass samples were synthesized by experimental technique using high pure germanium detector at different gamma ray sources using narrow beam method. The experimental method was verified by XCOM software. The values of the two methods were close and the relative deviation was satisfactory (less than 5 %) for all gamma energies (0.060, 0.662, 1.173 and 1.333 MeV). The highest linear attenuation coefficient (LAC) values achieved at low radiation energy of 0.0595 MeV. The Highest LAC values were 13.64, 13.97, 14.32 and 14.67 cm−1 for samples PCBT-1, PCBT-2, PCBT-3 and PCBT-4 in the same order, respectively. Conversely, the lowest LAC values in the examined energy range were found at 1.333 MeV. The lowest LAC values were 0.259, 0.266, 0.272 and 0.279 cm−1 for the aforementioned glasses, respectively. At 0.662 MeV, the transmission factor (TF) values decreases as 64.18, 63.54, 62.88 and 62.19 % as TiO 2 content increases as 5, 10, 15 and 20 mol % in the same order, respectively. The decreases in TF values was linked to an observable increase in the radiation protection efficiency (RPE). The increase in RPE with the increase of TiO 2 content confirms that the addition of TiO 2 leads to an improvement in the radiation shielding performance for the prepared glasses. • New borate based glasses were prepared for radiation shielding. • The experimental method was verified by XCOM software. • The highest LAC values achieved at 0.0595 MeV, varied between 13.64 and 14.67 cm−1. • The addition of TiO2 causes an increase in the RPE. [ABSTRACT FROM AUTHOR]

The response of a gamma-ray spectrometer is generally determined by analyzing full-energy peaks. However, full-energy peaks cannot be measured easily in the case of scintillation detectors that consist of light elements, such as glass scintillators. Only a strong Compton plateau appears in the spectrum of such detectors. Therefore, Compton edgers were used to evaluate the response of these detectors. The response of a low-resolution 6 Li-glass detector to gamma rays was measured for the first time by a coincidence method with a high-resolution LaBr 3 :Ce detector using cascade gamma rays (2.75 and 1.37 MeV) from a 24Na source. Coincidence gates were applied at the peaks of the spectrum of the LaBr 3 :Ce detector at the 0.51 MeV annihilation peak, and the sum peaks of a gamma ray and a backscattered gamma ray. By analyzing the gated spectra of the 6 Li-glass detector, the energy-dependent detector response (i.e., the output strength and its dispersion) was determined. • Evaluation of the response characteristics, including signal output and broadening, of a low-resolution 6Li-glass detector to gamma rays up to approximately 2.5 MeV. • Coincidence measurement of cascade gamma rays emitted from a 24Na source with a high-resolution detector, a LaBr 3 :Ce detector. • Peak analysis of the spectra of the 6Li-glass detector gated at gamma ray peaks of the LaBr3:Ce detector. [ABSTRACT FROM AUTHOR]

High-flux X-ray measurements with high-energy resolution and high throughput require the mitigation of pile-up and dead time effects. The reduction of the time width of the shaped pulses is a key approach, taking into account the distortions from the ballistic deficit, non-linearity, and time instabilities. In this work, we will present the performance of cadmium–zinc–telluride (CdZnTe or CZT) pixel detectors equipped with digital shapers faster than the preamplifier peaking times (ballistic deficit pulse processing). The effects on energy resolution, throughput, energy-linearity, time stability, charge sharing, and pile-up are shown. The results highlight the absence of time instabilities and high-energy resolution (<4% FWHM at 122 keV) when ballistic deficit pulse processing (dead time of 90 ns) was used in CZT pixel detectors. These activities are in the framework of an international collaboration on the development of spectroscopic imagers for medical applications (mammography, computed tomography) and non-destructive testing in the food industry. [ABSTRACT FROM AUTHOR]

A group from the University of Science and Technology of China in Hefei used rare earth ion-doped crystals to test the world's first quantum repeater segment based on absorptive quantum memories, and achieved the longest, record-breaking optical storage time of 1 hour. A list of the top 10 domestic science and technology stories was jointly released by the Chinese Academy of Sciences and the Chinese Academy of Engineering in Beijing on 18 January 2022. Graph: Tianwen-1, China's first mission to Mars, was decalred a success. [Extracted from the article]

Prompt gamma-ray neutron activation analysis (PGNAA) is a useful approach for determining the concentrations of a variety of elements in natural materials, either online or in situ, without affecting their chemical forms in matter. The current research aimed to improve the yield of a portable PGNAA setup using a dc beam of 2.5 MeV neutrons and a CeBr3 detector to record gamma rays from neutron inelastic scatterings. It is impossible to avoid the superimposition of heavy metal gamma rays and those from the detector's element. However, tests were carried out to improve the signal-to-background ratio. By assessing the minimum detectable concentrations (MDC) of chrome, titanium, and zinc in soil samples, the effectiveness of the new optimization was confirmed. The study shows an improvement in the MDC values. [ABSTRACT FROM AUTHOR]

The prime objective of this study is to estimate the natural radioactivity and their associated radiological hazards in soil samples of Uttara Kannada district having different geological conditions. The 226Ra, 232Th and 40K activities were estimated using HPGe detector based gamma ray spectrometer. The average 226Ra, 232Th and 40K activity concentrations are 36.13 ± 0.96, 48.47 ± 1.26 and 415.76 ± 6.83 Bq kg−1 respectively. The mean annual effective dose equivalent value was found to be 0.40 mSv y−1 and is less than the ICRP proposed value of 1 mSv y−1. The radiological hazard indices were computed and compared with internationally agreed values. [ABSTRACT FROM AUTHOR]

The concentration levels of 226Ra, 232Th and 40K in soil have a great concern in the recent decades, due to its effect on the human health. The radioactivity of some soil samples taken from selected locations in Sylhet District have been measured using a High Purity Germanium Detector based on gamma ray spectroscopy. The present investigation shows that the level of natural radioactivity for 226Ra, 232Th and 40K in such soil is slightly higher than World average value of UNSCEAR, 2000. The artificial radionuclide 137Cs was not observed in statistically significant amounts above background level in this study. The radiological hazard parameters i.e., radium equivalent activity, absorbed dose rate, external hazard index, internal hazard index, representative level index and annual effective dose equivalent are calculated from the measured activity concentrations of the radionuclides 226Ra, 232Th and 40K from soil samples in this study and compared with the world averages. The experimental soil data were subjected to statistical analysis using IBM SPSS software (version 20). Descriptive statistics of the radionuclides of the soil, Pearson's correlation matrix and Cluster Analysis have been carried out in this study. [ABSTRACT FROM AUTHOR]

Cadmium Zinc Telluride (CdZnTe) is a ternary Ⅱ- Ⅵ undeviating band gap semiconductor with cubic Zinc blende formation and it is a propitious material for ambient temperature xray as well as gamma ray sensor detectors. Cadmium Zinc Telluride (CdZnTe) thin layer coating were developed on nickel substrate by chemical bath deposition in non-aqueous approach. The as grown films were inspected by X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), Scanning electron microscope, Fourier transform infrared spectroscopy (FTIR), PL spectra, UV spectra, Raman spectroscopy and Four- Probe analysis. Studies tell that as grown films are poly-crystalline in nature along with cubic zinc blende formation. The structural properties like crystallite size, lattice constant, micro strain as well as dislocation density were evaluated. FESEM and SEM analysis reveals that the as developed films are smooth and equal sized uniform spherical grains distributed in single state as well as in cluster form. The average size of grain film is observed to be 12.33 nm. Optical study reveals the broad transmittance escorted by the band gap energy of 2.2eV. Electrical study reveals that resistivity of as grown film is 5.1×105 Ω-cm at room temperature. [ABSTRACT FROM AUTHOR]

Cs2 LiYCl6∶ Ce(CLYC) is a novel scintillation crystal with the capability of neutron and gamma-ray detection. It can be used in the field of neutron and gamma-ray detection. The CLYC scintillation crystal with 95% enrichment of 6 Li was grown by the vertical Bridgman method. After processing and moisture-proof packaging, a housed sample of ϕ50 mm ×50 mm CLYC scintillation crystal was obtained. 4. 22% energy resolution is measured at 662 keV of 137Cs gamma rays. Neutron-gamma discrimination is also achieved. The figure of merit (FOM) of pulse shape discrimination (PSD) measured with a 252Cf neutron source is 3. 45. With its excellent performance, CLYC scintillation crystal is expected to replacement for Helium-3 gas in the field of neutron detection, and can be used as the preferred material for n/ γ dual detection. So CLYC crystal can be used in neutron radiation detectors, radioisotope identification instruments, personal radiation dosimeters, and other neutrons gamma detection. [ABSTRACT FROM AUTHOR]

CdZnTe detectors play an important role in international astronomy research. In this paper, the spectra response of CdZnTe planar detector for γ-ray was numerically simulated using GEANT4 Monte-Carlo simulation toolkit, and the influence of the factors, such as transport properties of electrons and holes, applied bias voltage, thickness of detector and other factors were studied. The calculated results show that when the charge collection efficiency ( CCE) of electron is high, the dependence of energy resolution on the ratio of electron and hole mobility-lifetime product ((μτ)e/ (μτ)h) is strong, and the resolution increases with the decrease of the ratio. The energy resolution and CCE of carrier can be improved by raising up the bias. When the CCE of electron is high, increasing thickness can weaken the hole signal contribution to the total induced charge, and improve the energy resolution. The value of (μτ)eE /d can be used to evaluate CCE of planar CdZnTe detectors for rays of low energy, and the corresponding relationship was calculated. [ABSTRACT FROM AUTHOR]

Since the discovery of X-rays by Röntgen in 1895, radiation detection technology have developed rapidly and have been widely used in many fields such as medical imaging, security inspection, industrial non-destructive testing, nuclear safety monitoring, resource exploration, basic science and space science. In terms of detection materials and working principles, radiation detectors can be divided into gas detectors, scintillator detectors and semiconductor detectors. This article focuses on semiconductor detectors, starting from the interaction between various radiation and semiconductor materials, as well as the working principle and signal processing process of semiconductor detectors, and discusses the performance requirements and main points of detector design of semiconductor radiation detectors in different types of radiation and different application requirements. The performance and research progress of semiconductor materials in the field of radiation detection are reviewed according to the order of element family. [ABSTRACT FROM AUTHOR]

Recently, there have been several significant improvements in the area of the radiation detection system and its instruments, especially those using scintillation or semiconductor gamma ray detectors. Scientists and technicians are interested in studying this progress, which can be useful for the detector's operation and its basic properties, such as energy, shape, and efficiency calibration. In this work, an extended study of various mathematical formulas was conducted to obtain the efficiency best-fitting function, that covers the measured values from low to high energy regions. They can be used to represent the efficiency of a high-purity germanium detector in the regions where accuracy and maximum speed in optimizing the calibration process are very important for gamma spectroscopy. Determination of the activity of environmental samples mainly depends on the efficiency calibration curve of the detection system. The gamma ray energy in the range from 59.54 up to 1408.01 keV used in this work was obtained by using a set of standard radioactive gamma ray sources of certified intensity. The current data analysis shows that most of the mathematical formulas, which represent the fitting curve for the detector full-energy peak efficiency, were quite agreeable with the experimental results. [ABSTRACT FROM AUTHOR]

The present work deals with a 10 x 10 array of (Lu0.7Y0.3)AP:Ce 2 x 2 x 10 mm³ pixels, manufactured by Crytur (Cz), that has been utilized in a previous paper. The crystal-array has been coupled to an 8 x 8 anodes H10966 model Hamamatsu (Jp) Position-Sensitive Photo Multiplier Tube (PSPMT) connected to electronics for single events scintillation read-out. The response of such a detector has been studied under Co-57, or Ba-133, or Cs-137 gamma-ray emissions, as well as with Lu-176 self-activity only. The present work is aimed at characterizing the individual crystal- pixels' single-event responses in terms of pulse-height and of spreads of the 2-D charge-distributions. In particular, the charge-spread characterization pointed out several defects in the crystal-array assembly, not detected by usual pulse-height studies. The diagnostic method based on charge-spread analysis seems also well suited for scintillation array characterizations for gamma-ray detectors studies, as well as for quality controls of such pixelated devices during the lifetime of systems in the field of radionuclide medical imaging (SPECT and PET). The method is also appropriate for other applications where gamma-ray spectroscopy is required, like nuclear physics, astrophysics, astroparticle physics, homeland security, and non-proliferation. [ABSTRACT FROM AUTHOR]

Ceres' regolith contains water ice that has receded in response to insolation‐driven sublimation. Specially targeted, high spatial‐resolution measurements of hydrogen by Dawn's Gamma Ray and Neutron Detector (GRaND) reveal elevated hydrogen concentrations in and around Occator, a young, 90 km diameter, complex crater located at 19.82°N where near‐surface ice is not expected. The excess hydrogen can be explained by impact excavation of water‐rich outer crustal materials and their emplacement in the crater floor and ejecta blanket. This is supported by thermophysical models that show water ice could survive at sub‐meter depths, given Occator's relatively young age (∼20 Myr). We hypothesize that the regolith can be replenished with ice from large impacts and that this process partially controls the distribution and depth of near surface ice. This is supported by results from Occator and similarities in the global distribution of hydrogen and the pattern of large craters (20–100 km diameter). Plain Language Summary: The outermost meter of dwarf planet Ceres contains water ice that is gradually sublimating in response to heating of the surface by sunlight. Since Ceres' axis of rotation is nearly perpendicular to the Sun's rays, ice has receded to greater depths at the equator than the poles. The distribution of subsurface ice within this outer layer was inferred from measurements of hydrogen by Dawn's Gamma Ray and Neutron Detector. Special operations during Dawn's last mission phase brought the spacecraft close to the surface, enabling measurements within and around a large, young crater called Occator. Anomalously high concentrations of hydrogen were detected, suggesting the impact that formed Occator excavated water rich materials from the crust and deposited them on the surface. Comparison of the global distribution of hydrogen with the pattern of large craters on Ceres further supports excavation of crustal ice by impacts as a partial control on the depth of ice near the surface. Results confirm that Ceres' crust is rich in water ice and show that ice can survive in materials ejected by impacts into airless, icy bodies. Key Points: Neutron spectroscopy reveals enhanced hydrogen concentrations in the outermost meter of the surface of a prominent young, complex craterResults confirm Ceres outer crust is ice rich and support retention of water ice within impact ejecta on airless, icy bodiesThe data imply partial control of regolith ice content by large impacts, relaxing constraints on surface age and regolith grain size [ABSTRACT FROM AUTHOR]

Another radon detector measuring in a more shallow well did not observe any changes of radon before or during the earthquake [[3]]. The first observation of radon as a precursor to an earthquake was made in connection to the Tashkent earthquake in 1966, where increased levels of radon were observed prior to the earthquake and then reported in the scientific literature [[4]]. Each one has their own distinct decay chain involving mainly alpha but also beta and gamma radiation, through which different isotopes of the noble gas radon are produced via the alpha decay of radium (Rn). [Extracted from the article]

Imaging atmospheric Cherenkov telescopes (IACTs) are ground-based indirect detectors for cosmic gamma rays with energies above tens of GeV. The major backgrounds for gamma-ray observations in IACTs are cosmic-ray charged particles. The capability to reject these backgrounds is the most important factor determining the gamma-ray sensitivity of IACT systems. Monte Carlo simulations are used to estimate the residual background rates and sensitivity of the systems during the design and construction phase. Uncertainties in the modeling of high-energy hadronic interactions of cosmic rays with nuclei in the air propagate into the estimates of residual background rates and subsequently into the estimated instrument sensitivity. We investigate the influence of the difference in the current hadronic interaction models on the estimated gamma-ray sensitivity of the Cherenkov Telescope Array using four interaction models (QGSJET-II-03, QGSJET-II-04, EPOS-LHC, and SIBYLL2.3c) implemented in the air shower simulation tool CORSIKA. Variations in background rates of up to a factor 2 with respect to QGSJET-II-03 are observed between the models, mainly due to differences in the π0 production spectrum. These lead to ∼30% differences in the estimated gamma-ray sensitivity in the 1–30 TeV region, assuming a 50 h observation of a gamma-ray point-like source. The presented results also show that IACTs have a significant capability in the verification of hadronic interaction models. [ABSTRACT FROM AUTHOR]

The realization of pulsed-laser diffused, thin n + contacts on high purity germanium (HPGe) and their successful segmentation is described. The contacts have been obtained by a laser-induced diffusion of Sb atoms, deposited by sputtering on Ge surface, and then segmented by means of a photolithographic technique. Three small prototypes of gamma ray detectors have been implemented, using the same n + contact (laser diffused Sb) but with three different geometries and a B implanted p + contact. Electrical and detection properties of the prototypes have been characterized, showing low leakage currents and good spectroscopy data with different gamma-ray sources. The stability of the detector performance has also been tested subjecting one of the prototypes to a typical annealing treatment. [ABSTRACT FROM AUTHOR]

Internal conversion electron and gamma-ray spectroscopy measurements were carried out on the 10.551 y 133Ba electron-capture decay with our electron and gamma spectrometers—a mini-orange electron transporter paired to a Si(Li) detector and a large-volume HPGe detector, respectively. The relative and absolute gamma-ray intensities of all the nine transitions in 133Cs were determined. We also report the relative conversion intensities of eighteen conversion lines and their corresponding internal conversion coefficients (ICCs), four of which are being reported for the first time. Transition intensity balance at each energy level, showed that the measured values are self-consistent. This exhaustive dataset of gamma-ray intensities, internal conversion electron intensities and the ICCs that have low uncertainty, will be highly valuable for the purposes of energy and efficiency calibration of semiconductor gamma ray detectors and electron spectrometers. [ABSTRACT FROM AUTHOR]

One of the goals of the MICADO Euratom project is to monitor the gamma-rays emitted by radioactive waste drums in storage sites on a medium to long term basis. For this purpose, 36 low-cost gamma-ray counters were designed and built to act as a demonstrator. These counters, named SciFi, are based on a scintillating fiber readout at each end by a silicon photomultiplier, assembled in a robust arrangement in the form of 80 cm long pipes. Several counters will be placed around radwaste packages in order to monitor the gamma dose-rate by collecting a continuous data stream. The 36 sensors were thoroughly tested with a 22Na and a 137Cs gamma-ray sources, and with an AmBe neutron and gamma-ray source, the results are quite satisfactory, and the next step will be the test in a real environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quality non-polar GaN films (which itself is believed to be challenging) are deposited on the polar substrates using PLD route. • These non-polar GaN films exposed to 60Co Gamma radiations varying dose values from 40 kGy to maximum value of 260 kGy under atmospheric conditions. • The critical investigations reported on the non-polar GaN films for the first time, clearly demonstrate the resistive nature of the films against expose to energetic gamma rays is highly impressive. • The result reported herewith demonstrate use of non-polar GaN films can be one of the options to fabricate next generation of gamma ray detectors. The GaN films/layers exposed to γ-radiations is known to harvest defects and vacancies in the crystals producing donor, acceptor and recombination centers within the bandgap. Therefore it is important to investigate and study the γ- ray irradiation effects on various physical and chemical properties of a material before any optoelectronic and/or electronic devices are being fabricated. To avoid Stark effect which is observed in most of the optoelectronic devices fabricated using GaN films grew along polar face, use of non-polar GaN films is suggested by researchers. To address such issues the article reports the investigations of physical and chemical properties of non-polar GaN films grown on polar substrate using pulsed laser deposition, which were exposed to the 60Co gamma rays varying dose values. Resistive nature against the impairment of the films caused by γ-rays observed herewith is highly encouraging, suggesting the use of non-polar GaN films as radiations harden material suitable for fabricating new generation γ-ray detectors. To our knowledge very limited information is available that report such investigations. [ABSTRACT FROM AUTHOR]

The electrical signals generated by radiation detectors are often subject to undesired effects that can affect the energy resolution of the detector. These effects may be caused by the measurement system itself or by the high rate of events. Traditional methods for shaping the signals and mitigating these effects often have limitations, such as requiring explicit information about the signals. In this paper, the authors propose a deconvolution method based on least square filtering and non-negative sparsity theory to address these limitations. The method is evaluated using simulated data representing a gamma ray detector with a NaI(Tl) crystal and a photomultiplier tube (PMT). The electrical pulses in this system are pre-processed using a CR coupling circuit and a RC integrator. The energy resolution obtained with the traditional method was 6.60%, while the proposed method resulted in an energy resolution of 5.65%. In addition to improving accuracy, the proposed method also reduces implementation complexity. [ABSTRACT FROM AUTHOR]

In this study, albedo parameters are experimentally measured to determine radiation scattering features of some thermoluminescent dosimetry materials (TLD 100, TLD 100h, TLD 200 and TLD 400). In experimental setup, it was used scattering angle of 168°, 59.54 keV gamma rays and HPGe detector. The effective atomic numbers of the investigated materials were determined from the coherent to Compton scattering intensity ratio. Also, the mass attenuation coefficient, the mass energy absorption coefficient and kerma relative to air and ICRU tissue were calculated for the TLD materials. It was observed that TLD 100h is the best tissue equivalent material among other TLD materials and best reflects 59.54 keV gamma rays. • The effective atomic numbers of some thermoluminescent dosimetry materials were obtained from scattering ratios. • The effective atomic number and albedo parameters are obtained for 59.54 keV photon energy. • TLD 100h is the material that best reflects 59.54 keV gamma rays. [ABSTRACT FROM AUTHOR]

Initially intended as student-led projects at universities and research institutions, the CubeSats now represent a unique opportunity to access space quickly and in a cost-effective fashion. CubeSats are standard and miniaturized satellites consisting of multiple identical units with dimensions of about 10 × 10 × 10 cm 3 and very limited power consumption (usually less than a few W). To date, several hundreds of CubeSats have been already launched targeting scientific, educational, technological, and commercial needs. Compact and highly efficient particle detectors suitable for payloads of miniaturized space missions can be a game changer for astronomy and astroparticle physics. For example, the origin of catastrophic astronomical events can be pinpointed with unprecedented resolution by measuring the gamma-ray coincidence signals in CubeSats flying in formations, and possibly used as early warning system for multi messenger searches. In this paper, we will discuss and analyze the main features of a CubeSat mission targeting intense and short bursts of gamma-rays. [ABSTRACT FROM AUTHOR]

Fusion neutron activation experiments have been carried out to investigate the activation of metal materials in Experimental Advanced Superconducting Tokamak (EAST). Some cylindrical samples made of stainless steel 316L, carbon steel (A3), high purity cadmium (Cd), oxygen-free copper (Cu), and high purity aluminum (Al) were transported to Port G in the EAST hall for neutron irradiation. The characteristic gamma rays emitted by activated samples were measured with a spectrometer consisting of a digital multichannel analyzer (MCA) and a high purity germanium (HPGe) detector. Qualitative identification of the dominant radionuclides and quantitative measurement of the specific activity have been performed. The experimental results indicated that the high radioactive nuclides with short half-life were produced, such as 56Mn in 316L and A3, 28Al in Al, 66Cu in Cu, and 111m Cd in Cd. Moreover, the long half-life radionuclides were generated in 316L, A3, Cu and Cd samples, which will become the major factors on environment and personnel. In addition, the normalized dose rate at 10 cm in the air of 316L, A3, Al, Cd, and Cu was 1.53 × 10−23, 4.83 × 10−24, 5.57 × 10−23, 4.90 × 10−24 and 1.10 × 10−23 Sv/h/n, respectively. Finally, the comparison between the experimental neutron activation results and the predicted quantities calculated with FISPACT-2007 was discussed. [ABSTRACT FROM AUTHOR]

The Timepix3 hybrid-pixel readout chip consists of a matrix made of 256 × 256 square-shaped pixels with a 55-μm pitch, which can be hybridized to several semiconductors, such as silicon (Si) or cadmium telluride (CdTe) with thicknesses up to 5 mm. Working as an event-based readout chip, it simultaneously records the time-over-threshold (ToT) in each pixel, measuring the deposited energy, as well as the time-of-arrival (ToA), with a time resolution of 1.5 ns. In this article, we present the energy calibration of two Timepix3 chips: the first one was bump-bonded with a 300-μm-thick silicon sensor and the second one with a 1-mm-thick CdTe sensor. Both detectors were calibrated with per pixel calibration, using the monochromatic SOurce of Low-Energy X-rays [SOLEX from Henri Becquerel National Laboratory (LNHB) at CEA Saclay] and a set of calibration-grade sealed radioactive sources. Evaluations were carried out over the energy range 6-122 keV for Timepix3 Si and 20 keV- 1.332 MeV for Timepix3 CdTe. Based on this experimental procedure, an energy resolution of 2.6 keV (3.4%) at 59.5 keV was observed for Timepix3 Si. For Timepix3 CdTe, this parameter was 5.6 keV (9.4%) at 59.5 keV, 27.24 keV (4.1%) at 661.7 keV, and 47.4 keV (3.5%) at 1.332 MeV. It is the first time that CdTe bump-bonded Timepix3 spectral performances were evaluated for gamma rays above 1 MeV. The reconstruction of the full-energy peak for such high energies is possible due to the ToA information, which allows the identification of all interactions caused by a given gamma ray within the detector. [ABSTRACT FROM AUTHOR]

The NDeGRA project is researching the application of novel technologies in the development of position-sensitive detectors for gamma ray astronomy and medical imaging. The project's approach to simulation and some preliminary results on the upper limit of efficiency of a Compton camera design based on monolithic scintillator crystals are discussed. [ABSTRACT FROM AUTHOR]

Pile up and dead time are two important corrections in the analysis of X-ray and gamma ray spectra. The most important of these is pile up correction because these peaks do not really exist in the spectra; they only seem to exist. For this reason, these peaks affect both the qualitative and quantitative accuracy of the analysis. In addition, the pile up pulses forming the pile up peaks increase the background count in the spectrum. Companies that produce X-ray or gamma ray detector systems design pile up reject circuits and integrate them into detector systems to prevent these pulses. These circuits have time limitations because they are made up of electronic devices. For this reason, the pile up problem cannot be solved completely in these circuits. Therefore, mathematical models based on a statistical approach are needed. Such a model was developed in this study. A computer program based on this model was developed. This developed program has been applied to X-ray and gamma ray spectra. It has been shown that this model provides about 2% correction in the main peak regions and significantly reduces background counts. [ABSTRACT FROM AUTHOR]

Cadmium–zinc–telluride (CZT) pixel detectors represent a consolidated choice for the development of room‐temperature spectroscopic X‐ray imagers, finding important applications in medical imaging, often as detection modules of a variety of new SPECT and CT systems. Detectors with 3–5 mm thicknesses are able to efficiently detect X‐rays up to 140 keV giving reasonable room‐temperature energy resolution. In this work, the room‐temperature performance of 3 mm‐thick CZT pixel detectors, recently developed at IMEM/CNR of Parma (Italy), is presented. Sub‐millimetre detector arrays with pixel pitch less than 500 µm were fabricated. The detectors are characterized by good room‐temperature performance even at high bias voltage operation (6000 V cm−1), with energy resolutions (FWHM) of 3% (1.8 keV) and 1.6% (2 keV) at 59.5 keV and 122.1 keV, respectively. Charge‐sharing investigations were performed with both uncollimated and collimated synchrotron X‐ray beams with particular attention to recovering the charge losses at the inter‐pixel gap region. High rate measurements demonstrated the absence of high‐flux radiation‐induced polarization phenomena up to 25 × 106 photons mm−2 s−1. [ABSTRACT FROM AUTHOR]

The unfluctuating running of on-orbit spacecraft equipment has a decisive impact on the smooth implementation of space exploration mission. However, due to the adverse work conditions and complex running states, it is really a challenge for the online monitoring of aerospace equipment. In this paper, an improved growing neural gas method based on incremental learning is proposed, which is dedicated to solving the problem of online anomaly detection. The learning rate of the proposed method is adaptively adjusted according to the process of model training, ensuring the weights update quickly at the beginning of model construction and converge steady at the end of model training. The optimized insertion mechanisms of neurons ensure that the necessary new neurons are inserted at the right time and location dynamically, while the innovative deletion mechanisms of neurons ensure that the worthless neurons be deleted timely and at the same time guarantee the representation ability of model. The comparison results with the conventional methods on public datasets show that the proposed method achieves the better performance obviously, both in the aspects of detection accuracy and computational efficiency, respectively. At last, as a case study, the proposed method is used for online anomaly detection of a real aerospace device, i.e., a gamma ray detector, and the final F1 score of anomaly detection is as high as 98.78%. The results show that the proposed method can be applied to online detection of aerospace equipment health conditions effectively. [ABSTRACT FROM AUTHOR]

Finding and tracking radioactive sources have numerous security applications in civilian energy installations, military facilities, and ports of entry. The price of radiological sensors varies proportionally to size and imaging characteristics such as angular resolution, and the cheapest devices are nearly isotropic–i.e., they integrate radiation from a sphere of directions centered at the sensor. While many radiation sensors have high aspect ratios or odd shapes, the sensors used here are right cylinders, with a near identical directional efficiency such that for analysis purposes, other aspects, such as counting statistics, would make nonisotropy of the sensor negligible. In this article, we propose a simple and robust way to integrate measurements from both isotropic radiological sensors and depth sensors, whose reliability and resolution benefit from recent advances in computer vision and imaging. Our key idea is to convert all sensor measurements into proximity signals based on radial distance variations over time. Based on this sensor fusion model, we show that for moving radiological sources even a simple Kalman filter can trade-off the complementary strength of high-resolution depth sensors and isotropic radiological sensors. We show novel results with a LIDAR sensor and a thermal stereo pair, and demonstrate applications such as tracking and rendering non-line-of-sight imagery behind obstacles and detecting multiple radiological sources in the same scene. [ABSTRACT FROM AUTHOR]

Radiation rays, especially gamma rays, are produced during nuclear fusion plasma discharge. To obtain the gamma rays around the Experimental Advanced Superconducting Tokamak (EAST) during nuclear fusion plasma discharges, Ar-based gamma ray detectors have been adopted in this article, and to fully monitor the gamma ray dose rates inside the EAST hall, three gamma ray detectors have been set at three selected radiation monitoring sites. Due to the long distances between the monitoring personal computer (PC) and each radiation monitoring site, the monitoring system based on the RS-485 differential communication mode has been designed and set up. With each plasma discharge, the gamma ray radiation field undoubtedly appears as a pulsed radiation field in the EAST hall. Based on the gamma ray dose rates obtained by the monitoring system, the pulsed radiation field of gamma ray dose rates has been carefully studied during one lower hybrid current drive (LHCD)-based plasma discharge. Finally, the exponential function model of the gamma ray dose rates during one plasma discharge in the EAST hall was well obtained and presented. [ABSTRACT FROM AUTHOR]

Metallic magnetic calorimeters (MMCs) combine the excellent energy resolution of cryogenic gamma ray detectors with a very small nonlinearity and a reproducible response, owing to their magnetization-based sensor and their metallic heat flow path. These attributes make MMCs well suited for photon and particle spectroscopy applications requiring the highest accuracy. We are developing high-resolution MMC gamma ray detectors with the goal of improving the quality of key nuclear decay data for nuclear safeguards and fundamental science. Our exploratory "integrated" (SQUIDs and sensors on the same chip) 14-pixel MMC designs recently demonstrated energy resolution of 37.5 eV at 60 keV. Here, we describe the design and optimization for a new generation of MMC detectors using both "integrated" and "split" designs (SQUIDs and sensors on separate chips). The new designs are expected to have an energy resolution < 25 eV (< 5 eV) for MMCs optimized for energies up to 100 keV (10 keV) and have up to 32 pixels. [ABSTRACT FROM AUTHOR]

In order to obtain the relationship between energy and channel, the suitable radionuclides are chosen to calibrate. The result shows a goodness of fitting. The Monte Carlo simulation about the detection efficiency of the high purity germanium (HPGe) gamma-spectrometry system was performed. The distance between radioactive source and the end cap is set 15, 20, 25 and 50 cm, respectively. The maximum absolute efficiency locates at around 80 keV. It can be concluded that the absolute efficiency is declining accompany with the increasing of distance. In the end, at the distance of 25 cm, the authors changed thickness of the dead layer and the source distribution to calculate. The maximum absolute efficiency is 8.56E−03, and the relative deviation is 0.0011. Then it was compared with the experimental result provided with the manufacturer. The result of simulation shows a certain agreement with the experimental results. This work will be helpful for calculating the efficiency of HPGe gamma-spectrometry. [ABSTRACT FROM AUTHOR]

The heavy element semiconductor compound Cs2Hg6S7 is of interest as a potential wide gap semiconductor for gamma ray detection. To determine electrically active defects and their energy levels, photoconductivity (PC) spectroscopy was carried out over the temperature range of 90-295 K. The low temperature spectrum exhibits photoconductive transitions at 1.495, 1.61, 1.66, and 1.68 eV. The optical transitions are tentatively attributed to defects with levels located at energies of 50, 70, 120, and 240 meV from the band edge. A superlinear dependence of photocurrent on illumination intensity is observed that is attributed to a two-center recombination process that involves shallow traps and recombination centers. Near band edge photoluminescence (PL) was observed over the temperature range of 24-80 K. The spectrum revealed three defect related emission bands located at 1.68, 1.66, and 1.62 eV, whose ionization energies are 57 meV, 78 meV, and 115 meV, respectively. From the temperature and excitation dependencies of the observed peak intensities and energies, the radiative recombination mechanisms of the bands were attributed to transitions involving excitons bound to neutral and ionized acceptors. Good agreement of the defect level energies determined by PL and PC were noted, indicating that they were of the same origin. The defects were tentatively attributed to metal vacancies that form shallow acceptor levels. [ABSTRACT FROM AUTHOR]

We report on the indigenous design and development of laboratory scale travelling heater method (THM) system to grow detector grade Cd 0.9 Zn 0.1 Te (CdZnTe) single crystals. THM system mainly consists of two-zone furnace with a tuneable temperature gradient (30–80 °C/cm), high precision translation (1–25 mm/day) and rotation (1–50 rpm) assemblies to meet the stringent conditions that are essential to grow detector grade CdZnTe single crystals. Further, a load cell in the THM system enables continuous monitoring of the growth. Systematic growth experiments were performed to optimize the various growth parameters in order to achieve large grain single crystals. Herein, the effect of temperature gradient and growth rate on the increase in grain size is discussed in detail. Each successful growth experiment yields a minimum of four detector grade elements of dimensions 10 × 10 × 5 mm3 from a starting charge of 100 g of CdZnTe. The crystalline nature and quality of the detector elements were evaluated using Laue, NIR transmission spectroscopy and I–V characteristics. Crystals with resistivity greater than ∼109 - 1010 Ω-cm were identified for testing gamma ray detection. The photo peak of 137Cs was resolved with an energy resolution of 4.2% at 662 keV and its measured electron mobility lifetime product is found to be ∼3.3 × 10−3 cm2/V. The demonstration of the gamma ray detection with a relatively high μτ product is the testimony to the successful growth of detector grade CdZnTe single crystals by an indigenously developed THM system. [Display omitted] • Detector grade CdZnTe crystals are grown using indigeniously developed THM system. • Temperature gradient and growth rate are optimized for high quality crystals. • Atleast 4 detector elements of 10 × 10 × 5 mm3 obtained from 100 g of initial charge. • Indigenous developed CdZnTe detectors display energy resolution of 4.2 % at 662 keV. [ABSTRACT FROM AUTHOR]

The speeding particles may in turn generate gamma rays, for example by colliding with photons and boosting their energy. With its improved resolution and ability to produce detailed spectra of gamma ray energies, CTAO's data should help refine theoretical models of the supernova particle accelerators, Araudo says. [Extracted from the article]

Compact multi-channel radiation detectors rely on low noise front-end application specific integrated circuits (ASICs) to achieve high spectral resolution. Here, a new ASIC developed to readout virtual Frisch-grid cadmium zinc telluride (VFG CZT) detectors for gamma ray spectroscopy is presented. Corresponding to each ionizing event in the detector, the ASIC measures the amplitude and timing at the anode, the cathode and four pad sense electrodes associated with each sensor in a detector array. The ASIC is comprised of 52 channels of which there are 4 cathode channels and 48 channels which can be configured as either anode channels with a baseline of 250 mV or pad sense channels to process induced signals with a baseline of 1.2 V. With a static power dissipation of 3 mW, each channel performs low-noise charge amplification, high-order shaping, peak and timing detection along with analog storage and multiplexing. The overall channel linearity was better than ± 1% with timing resolution down to 700 ps for charges greater than 8 fC in the 3 MeV range. With a 4 × 4 array of 6 mm × 6 mm × 20 mm virtual Frisch-grid bar sensors connected and biased, an electronic resolution of ≈ 270 e−rms for charges up to 100 fC in the 3.2 MeV range was measured. Spectral measurements obtained with the 3D correction technique demonstrated resolutions of 1.8% FWHM at 238 keV and 0.9% FWHM at 662 keV. [ABSTRACT FROM AUTHOR]