Γ-ray Detector Research Articles

Supernova Shock Breakout/Emergence Detection Predictions for a Wide-field X-Ray Survey

There are currently many large-field surveys that are operational and are being planned including the powerful Vera C. Rubin Observatory Legacy Survey of Space and Time. These surveys will increase the number and diversity of transients dramatically. However, for some transients, like supernovae (SNe), we can gain more understanding by directed observations (e.g., shock breakout and γ-ray detections) than by simply increasing the sample size. For example, the initial emission from these transients can be a powerful probe of these explosions. Upcoming ground-based detectors are not ideally suited to observing the initial emission (shock emergence) of these transients. These observations require a large field-of-view X-ray mission with a UV follow-up within the first hour of shock breakout. The emission in the first 1 hr to even 1 day provides strong constraints on the stellar radius and asymmetries in the outer layers of stars, the properties of the circumstellar medium (e.g., inhomogeneities in the wind for core-collapse SNe and accreting companions in thermonuclear SNe), and the transition region between these two areas. This paper describes a simulation for the number of SNe that could be seen by a large field-of-view lobster-eye X-ray and UV observatory.

Analytical-numerical formula for estimating the characteristics of a cylindrical NaI(Tl) gamma-ray detector with a side-through hole

NaI(Tl) scintillation materials are considered to be one of many materials that are used exclusively for γ-ray detection and spectroscopy. The gamma-ray spectrometer is not an easy-to-use device, and the accuracy of the numerical values must be carefully checked based on the rules of the calibration technique. Therefore, accurate information about the detection system and its effectiveness is of greater importance. The purpose of this study is to estimate, using an analytical-numerical formula (ANF), the purely geometric solid angle, geometric efficiency, and total efficiency of a cylindrical NaI(Tl) γ-ray detector with a side-through hole. This type of detector is ideal for scanning fuel rods and pipelines, as well as for performing radio-immunoassays. The study included the calculation of the complex solid angle, in combination with the use of various points like gamma sources, located axially and non-axially inside the through detector side hole, which can be applied in a hypothetical method for calibrating the facility. An extended γ-ray energy range, the detector, source dimensions, “source-to-detector” geometry inside the side-through hole, path lengths of γ-quanta photons crossing the facility, besides the photon average path length inside the detector medium itself, were studied and considered. This study is very important for an expanded future article where the radioactive point source can be replaced by a volume source located inside the side-trough hole of the detector, or by a radioactive pipeline passing through the well. The results provide a good and useful approach to a new generation of detectors that can be used for low-level radiation that needs to be measured efficiently.

Excitation functions of proton-induced reactions on natW target for rhenium isotope production

The proton-induced reaction cross-sections on natural tungsten within the proton energy range of 12.50 ± 0.79 MeV to 44.08 ± 0.33 MeV are determined by using the stacked-foil activation method and offline γ-ray spectrometry at the MC50 cyclotron of the Korea Institute of Radiological and Medical Science. The proton beam intensity is determined by using the natCu(p,xn)62Zn and natCu(p,xn)65Zn monitor reactions. The residual nuclide activities are measured using an HPGe γ-ray detector. The experimental results in this work contains 63 individual measured points for seven identified nuclides 181;182m,g;183;184m,g;186Re via the natW(p,xn) reactions. In addition, the thick target yields are determined for the 181;182m,g;183;184m,g;186Re products produced from the natW(p,xn) reactions. The present data are compared with literature data and the theoretical predictions from the TALYS-1.9 code and the TENDL-2019 library.

Assessment of the associated particle technique with high-resolution gamma-ray spectroscopy for in-field identification of chemical warfare agents and explosives

High-resolution prompt γ-ray neutron activation analysis (PGNAA) is performed using the associated particle (AP) technique with a deuterium–tritium neutron generator and high-purity germanium detector. Although the time resolution is inferior compared to similar systems employing fast scintillation γ-ray detectors, the strong background suppression combined with the high γ-ray energy resolution provides an important boost in sensitivity to certain key elements, especially relevant to field measurements of complex chemicals encased within thick layers of metal, such as in recovered chemical warfare (CW) munitions. Results for various CW and explosive simulants contained within mock munitions are presented and compared with results obtained from traditional PGNAA measurements without the aid of the AP technique. Significant improvements in identification and discrimination between certain chemicals are achieved with the high energy resolution AP technique.

MALS SALT-NOT Survey of MIR-selected Powerful Radio-bright AGN at 0 < z < 3.5

We present results of an optical spectroscopic survey using SALT and the Nordic Optical Telescope to build a Wide-field Infrared Survey Explorer mid-infrared color-based, dust-unbiased sample of powerful radio-bright (>200 mJy at 1.4 GHz) active galactic nuclei (AGN) for the MeerKAT Absorption Line Survey (MALS). Our sample has 250 AGN (median z = 1.8) showing emission lines, 26 with no emission lines, and 27 without optical counterparts. Overall, our sample is fainter (Δi = 0.6 mag) and redder (Δ(g−i) = 0.2 mag) than radio-selected quasars, and representative of fainter quasar population detected in optical surveys. About 20% of the sources are narrow-line AGN (NLAGN)–65% of these, at z < 0.5 are galaxies without strong nuclear emission, and 10% at z > 1.9, have emission line ratios similar to radio galaxies. The farthest NLAGN in our sample is M1513-2524 (z em = 3.132), and the largest radio source (size ∼330 kpc) is M0909-3133 (z em = 0.884). We discuss in detail 110 AGN at 1.9 < z < 3.5. Despite representing the radio loudest quasars (median R = 3685), their Eddington ratios are similar to the Sloan Digital Sky Survey quasars having lower R. We detect four C iv broad-absorption line (BAL) QSOs, all among AGN with least R, and highest black hole masses and Eddington ratios. The BAL detection rate (%) is consistent with that seen in extremely powerful (L 1.4GHz > 1025 W Hz−1) quasars. Using optical light curves, radio polarization, and γ-ray detections, we identify seven high-probability BL Lacertae objects. We also summarize the full MALS footprint to search for H i 21 cm and OH 18 cm lines at z < 2.

Radiation Monitoring in the Residential Environment: Time Dependencies of Air Dose Rate and 137Cs Inventory

Background: Residential areas have some factors on the external exposure of residents, who usually spend a long time in these areas. Although various survey has been carried out by the government or the research institutions after the Fukushima Daiichi Nuclear Power Plant accident, the mechanism of radiocesium inventory in the terrestrial zone has not been cleared. To better evaluate the radiation environment, this study investigated the temporal changes in air dose rate and 137Cs inventories (Bq/m2) in residential areas and agricultural fields.Materials and Methods: Air dose rate and 137Cs inventories were investigated in residential areas located in an evacuation zone at 5–8 km from the Fukushima Daiichi Nuclear Power Plant. From December 2014 to September 2018, the air dose rate distribution was investigated through a walking survey (backpack survey), which was conducted by operators carrying a γ-ray detector on their backs. Additionally, from December 2014 to January 2021, the 137Cs inventories on paved and permeable grounds were also measured using a portable γ-ray detector.Results and Discussion: In the areas where decontamination was not performed, the air dose rate decreased faster in residential areas than in agricultural fields. Moreover, the 137Cs inventory on paved surfaces decreased with time owing to the horizontal wash-off, while the 137Cs inventory on permeable surfaces decreased dramatically owing to the decontamination activities.Conclusion: These findings suggest that the horizontal wash-off of 137Cs on paved surfaces facilitated the air dose rate decrease in residential areas to a greater extent compared with agricultural fields, in which the air dose rate decreased because of the vertical migration of 137Cs. Results of this study can explain the faster environmental restoration in a residential environment reported by previous studies.

Ultrafast probing of plasma ion temperature in proton–boron fusion by nuclear resonance fluorescence emission spectroscopy

Aneutronic fusion reactions such as proton–boron fusion could efficiently produce clean energy with quite low neutron doses. However, as a consequence, conventional neutron spectral methods for diagnosing plasma ion temperature would no longer work. Therefore, finding a way to probe the ion temperature in aneutronic fusion plasmas is a crucial task. Here, we present a method to realize ultrafast in situ probing of 11B ion temperature for proton–boron fusion by Doppler broadening of the nuclear resonance fluorescence (NRF) emission spectrum. The NRF emission is excited by a collimated, intense γ-ray beam generated from submicrometer wires irradiated by a recently available petawatt (PW) laser pulse, where the γ-ray beam generation is calculated by three-dimensional particle-in-cell simulation. When the laser power is higher than 1 PW, five NRF signatures of a 11B plasma can be clearly identified with high-resolution γ-ray detectors, as shown by our Geant4 simulations. The correlation between the NRF peak width and 11B ion temperature is discussed, and it is found that NRF emission spectroscopy should be sensitive to 11B ion temperatures Ti &amp;gt; 2.4 keV. This probing method can also be extended to other neutron-free-fusion isotopes, such as 6Li and 15N.

Rejection of the internal α background in LaBr3:(Ce) detectors by using a wavelet-based pulse-shape discrimination method

LaBr3:(Ce) exhibits the best energy resolution among scintillation γ-ray detectors. The excellent energy resolution of this detector has made it suitable for many radiation detection applications such as environmental monitoring, medical imaging, nuclear security, nuclear physics experiments, etc. However, LaBr3:(Ce) crystal endures from internal radioactivity which produces a considerable background in the measurements. The problem of internal radiation is particularly acute with large size detectors, measuring low-intensity γ-rays. A considerable part of the internal radiation comes from the α-decay of 227Ac and its daughters which are present as an impurity in the detector’s crystal. Unfortunately, due to the very similar chemical properties of Actinium and Lanthanum, it is very difficult to remove the 227Ac impurity by using purification processes, and therefore, the α-background is present in all the commercial crystals. A practical approach for the reduction of this problem is to identify the α-events through an electronic analysis of the shape of output pulses of the detector and reject them. In the past, several digital pulse-shape discrimination (PSD) methods have been proposed to suppress the internal α background in LaBr3:(Ce) detectors. These methods exploit the small difference in the shape of scintillation pulses from α- and γ-ray interactions. The PSD methods have demonstrated some degree of success, which are limited to only a partial rejection of the α-background while further reduction of the α background is highly desirable for low-background γ-ray measurements. In this work, a novel digital PSD method that significantly improves the rejection of the internal α background was developed. The PSD method is based on the wavelet transform of the scintillation pulses, leading to an almost complete rejection of the α background. This method is very useful for low-level radiation measurements with LaBr3:(Ce) detectors involving high-energy γ rays.

Recent Progress in Halide Perovskite Radiation Detectors for Gamma-Ray Spectroscopy

Detecting hard X-rays and γ-rays with high energy resolution is critical for medical and industrial applications, high-energy fundamental physics, and homeland security. Two types of radiation detectors, indirect-conversion (scintillators) and direct-conversion (solid-state) detectors, are the most widely used technologies. Semiconductor-based detectors that can directly convert γ-rays into an electrical signal and operate at room temperature are especially important as portable and cost-efficient detectors with high sensitivity and energy resolution. Recently, lead halide perovskites have attracted enormous interest for γ-ray detection, and significant progress has been made toward practical detectors using perovskites as active materials. In this Review, we start with the fundamentals of γ-ray detection and review the recent developments in halide perovskite γ-ray detectors. The key factors affecting the detector performance are summarized. We also give an outlook on the field, with emphasis on the challenges to be overcome.

Chapter 7 Solar and Heliospheric Physics and Interdisciplinary Research with LHAASO * *Supported in China by National Natural Science Foundation (NSFC) (12047576, U2031101, 11475141), and the National Key R&D Program of China (2018YFA0404201, 2018YFA0404202), and in Thailand by the Thailand Science Research and Innovation (RTA6280002)

In the following sub-sections, studies of solar-heliospheric effects on cosmic rays, investigating a possible link between cosmic ray flux and Earth’s climate, and detection of MeV-range γ-rays from thunderstorms with the data from LHAASO will be discussed; geophysical research with environmental neutrons will be introduced, and some Monte Carlo simulation results about effects of thunderstorm electric fields on LHAASO observations of cosmic rays will be given.

Searching for better X-ray and γ-ray photodetectors: structure-composition properties of the TlPb2Br5-x I x quaternary system.

Developing X-ray and γ-ray detectors with stable operation at ambient temperature and high energy resolution is an open challenge. Here, we present an approach to search for new detector materials, combining binary photodetector compounds. More specifically, we explore quaternary TlPb2Br5−xIx compositions, relying on materials synergy between TlBr, TlI, and PbI2 photodetectors. We discover a broad solid solution in the TlPb2Br5–‘TlPb2I5’ section, which can be derived from a new quaternary compound, TlPb2BrI4, by partial substitution of Br by I atoms on the 4c site or by replacement of I by Br atoms on the 16l site. We carry out a thorough crystallographic analysis of the new TlPb2BrI4 compound and prepare a high-quality standardized structure file. We also complete the phase diagram of the TlPb2Br5–‘TlPb2I5’ section, based on 21 alloys. Furthermore, we synthesize a series of high quality centimeter-sized TlPb2Br5−xIx single crystals (x = 2, 2.5, 3, 3.5, 4, 4.5) by the Bridgman–Stockbarger method and study their structure and properties using a combination of experimental techniques (X-ray diffraction, X-ray photoelectron spectroscopy, and absorption spectroscopy) and theoretical calculations.

New study of the neutron rich 136Te isotope through decay spectroscopy

136Sb is a neutron rich nucleus with one valence proton and three valence neutrons outside the doubly-magic nucleus 132Sn. It plays an important role in the rapid neutron capture process (r-process) as participates in its path further connected to the nucleosynthesis and the type II supernovae. In this work, a new β decay γ ray data on 136Te is obtained. The experiment is performed at the Institute Laue-Langevin using the Lohengrin spectrometer and the thermal neutron-induced fission reaction on $_{92}^{235}{{\rm{U}}_{143}}$. A specific β-β condition method is investigated for the γ-ray detection.

Characterization of Schottky-diode X/[formula omitted]-ray detectors based on CdTe crystals with different uncompensated impurity concentrations

The Schottky-diode X/ γ-ray detectors based on semi-insulating p-like CdTe single crystals with four values of uncompensated impurity concentration (N≈ 2 × 1012 cm−3, 2 × 1011 cm−3, 1 × 1011 cm−3, 4 × 1010 cm−3) were developed and characterized by I-V measurements at low reverse bias (0.005–100 V) and detection of 137Cs and 241Am radioisotope emission spectra. All the detectors were fabricated by the same technique using vacuum evaporation of a Cr electrode (rectifying contact) and chemical deposition of an Au electrode (Ohmic contact) onto the B- and A-face of CdTe(111) crystals, respectively, pre-treated with Ar-ion bombardment. The change of the charge transport mechanism from over-barrier (thermionic) to generation current along with the analysis of the temperature dependence of the differential resistivity evidenced a high concentration of deep level impurities near the middle of the semiconductor bandgap. The detection efficiency η of the detectors was calculated using the corrected expressions for the coordinate dependence of the electrical field strength in a diode which took into account the fact that the depletion region width exceeded the CdTe crystal thickness at higher bias voltages. It was shown that the dependence η(N) decreased with increasing N without a maximum corresponding to an optimal value Nopt as reported earlier. The Cr/CdTe/Au Schottky-diode detectors, fabricated using CdTe with the lowest N, demonstrated the highest energy resolution (0.6% @662 keV and 7.5% @59.5 keV) and it degraded when crystals with higher N were used.

Detectability of electromagnetic counterparts from neutron star mergers: prompt emission versus afterglow

ABSTRACT Electromagnetic observations of the first binary neutron star (BNS) merger detected in gravitational waves, GW170817, have established that relativistic jets can be successfully launched in BNS mergers. Typically, such jets produce emission in two phases: γ-ray prompt emission and multiwavelength afterglow. Because of relativistic beaming and the jet’s angular structure, the detectability of both these counterparts is dependent on the angle (θ${\rm v}$) between the observer’s line of sight and the jet axis. We compare the detectability of prompt and afterglow emission from off-axis jets, assuming standard detector thresholds such as that of Fermi Gamma-ray Burst Monitor (GBM), Chandra, and Jansky Very Large Array (VLA). We find that for top-hat jets, afterglow is a more likely counterpart than the prompt emission even with unfavourable afterglow parameters. For structured jets with a Gaussian profile, prompt emission is more promising than the afterglows at extreme viewing angles, under the assumption that the total energy emitted in the prompt phase equals the kinetic energy of the outflow. Assuming a Gaussian jet profile, we forecast the population of γ-ray detections and find that extreme viewing angle events like GRB 170817A will be rare. In our simulated sample, the observed isotropic equivalent energy in γ-rays is moderately correlated with the viewing angle, such that a low Eiso,γ is almost always associated with a high off-axis viewing angle.

The polarization sensitivity of GRETINA

Compton polarimeters have played an important role in the study of nuclear structure physics, but have often been limited in their applications because of relatively low γ-ray detection efficiency. With the advent of γ-ray tracking detector arrays, which feature nearly 4π solid angle coverage and the ability to identify the location of Compton-scattering events to within a few millimeters, this limitation can be overcome. Here we present a characterization of the performance of the Gamma Ray Energy Tracking In-beam Nuclear Array (GRETINA) as a Compton polarimeter using the 24Mg(p,p′) reaction at 2.45 MeV proton energy. We also discuss a new capability added to the simulation package UCGretina to simulate the emission of polarized photons, and compare it to the measured data. Finally, we use these simulations to predict the performance of the Gamma Ray Energy Tracking Array (GRETA).

Optical Singly-Ionized Iron Emission in Radio-Quiet and Relativistically Jetted Active Galactic Nuclei

The issue of the difference between optical and UV properties of radio-quiet and radio-loud (relativistically “jetted”) active galactic nuclei (AGN) is a long standing one, related to the fundamental question of why a minority of powerful AGN possess strong radio emission due to relativistic ejections. This paper examines a particular aspect: the singly-ionized iron emission in the spectral range 4400–5600 Å, where the prominent HI Hβ and [Oiii]λλ4959,5007 lines are also observed. We present a detailed comparison of the relative intensity of Feii multiplets in the spectral types of the quasar main sequence where most jetted sources are found, and afterwards discuss radio-loud narrow-line Seyfert 1 (NLSy1) nuclei with γ-ray detection and with prominent Feii emission. An Feii template based on I Zw 1 provides an accurate representation of the optical Feii emission for RQ and, with some caveats, also for RL sources. CLOUDY photoionization simulations indicate that the observed spectral energy distribution can account for the modest Feii emission observed in composite radio-loud spectra. However, spectral energy differences alone cannot account for the stronger Feii emission observed in radio-quiet sources, for similar physical parameters. As for RL NLSy1s, they do not seem to behave like other RL sources, likely because of their different physical properties, that could be ultimately associated with a higher Eddington ratio.

Silicon substrate diamond film detector for gamma dose rate measurement in a high radiation environment

A detector that can accurately measure gamma (γ) rays in a high radiation environment was developed to detect high-intensity and high-energy γ rays in deep space. Traditional semiconductor detectors cannot work in high radiation environments for a long time, and pure single-crystal diamond detectors cannot be popularised on a large scale due to their high cost. We proposed a diamond γ-radiation (SD) detector with a highly oriented diamond film structure on a highly oriented boron-doped silicon substrate to measure γ-dose rate in high radiation environments. The SD detector was developed using several microelectromechanical processes, such as microwave plasma chemical vapour deposition. Consequently, in radiation from the 12,000 Ci 60Co source, when the dose rate was 200 Gy/h, the output signal could stabilise within 1 s. Within the dose rate of 10–190 Gy/h, the output showed a linear relation with the changing dose rate. The detector sensitivity reference value was S = 2.08 × 10−20 C · cm2 at a distance of 3.61 m from the 12,000 Ci 60Co source. Our study can provide guidance for deep space γ-ray detection.

Bias polarization characterization of Al/CdTe/Pt Schottky X-ray detector for industrial applications

Al/CdTe/Pt Schottky diodes are commonly used as X-ray and γ-ray detectors thanks to their high absorption coefficients and room temperature working conditions. One known drawback is the bias induced polarization, which downgrades the spectroscopic performances by progressively decreasing the charge collection efficiency. In the frame of charge accumulation model (CAM), the bias induced polarization is explained with Cd vacancies that create a deep acceptor level inside the gap: when a reverse voltage is applied, this level is thermally populated deforming the electric field inside the detector. We measured the reverse current transient at different temperatures and interpreted the experimental results with the CAM. In particular, we investigated the Schottky barrier height, its relation to the electric field at the anode, the ratio between deep trap concentration and de-trapping time and the energy of the deep acceptor level. We estimate an energy of 0.59eV above the valence band edge for the acceptor level. We propose a variation to the CAM that takes into account two deep acceptor levels, instead of only one, this allows to improve the fittings of the time dependence of the electric field at the anode.

Calibration of cylindrical NaI(Tl) gamma-ray detector intended for truncated conical radioactive source

The computation of the solid angle and the detector efficiency is considering to be one of the most important factors during the measuring process for the radioactivity, especially the cylindrical γ-ray NaI(Tl) detectors nowadays have applications in several fields such as industry, hazardous for health, the gamma-ray radiation detectors grow to be the main essential instruments in radiation protection sector. In the present work, a generic numerical simulation method (NSM) for calculating the efficiency of the γ-ray spectrometry setup is established. The formulas are suitable for any type of source-to-detector shape and can be valuable to determine the full-energy peak and the total efficiencies and P/T ratio of cylindrical γ-ray NaI(Tl) detector setup concerning the truncated conical radioactive source. This methodology is based on estimate the path length of γ-ray radiation inside the detector active medium, inside the source itself, and the self-attenuation correction factors, which typically use to correct the sample attenuation of the original geometry source. The calculations can be completed in general by using extra reasonable and complicate analytical and numerical techniques than the standard models; especially the effective solid angle, and the detector efficiency have to be calculated in case of the truncated conical radioactive source studied condition. Moreover, the (NSM) can be used for the straight calculations of the γ-ray detector efficiency after the computation of improvement that need in the case of γ-γ coincidence summing (CS). The (NSM) confirmation of the development created by the efficiency transfer method has been achieved by comparing the results of the measuring truncated conical radioactive source with certified nuclide activities with the γ-ray NaI(Tl) detector, and a good agreement was obtained after corrections of (CS). The methodology can be unlimited to find the theoretical efficiencies and modifications equivalent to any geometry by essential sufficiently the physical selective considered situation.

Low dose rate γ-ray detection using a MAPS camera under a neutron radiation environment.

We present γ-ray radiation detection in a neutron radiation environment using a monolithic active pixel sensor (MAPS) camera without conversion or shielding layers. The measured output signal is the sum of the pedestal value, noise, and real radiation response signal. The sensor response shows that the MAPS camera is sensitive to neutrons and can capture a single photon. The number of pixels with a signal exceeding 100 exhibits a strong dependence on the dose rate and is the best indicator of this value. Therefore, a MAPS camera can be efficiently used as a radiation detection sensor in a robotic system, further limiting human errors in performing radiation detection in complex nuclear radiation environments.