Low-energy Gamma Rays Research Articles

Investigation of gamma-ray radiation shielding properties of zinc borate and paraffin filled sheep wool biopolymer composites: Experimental and theoretical analysis

The present study examines the potential of sheep wool biopolymer composites filled with zinc borate and paraffin wax additives as a gamma-ray radiation shielding material. The selected novel composite samples were prepared with varying proportions of additive materials (10, 20, 30, and 40 wt%) so that impact of the additive amount on radiation shielding could be properly analyzed. Evaluations of specimens were performed at different energy levels ranging from 20 keV to 1.3325 MeV with help of a NaI scintillation detector, MC simulation (GEANT4) and WinXCOM theoretical calculation code. Following the production of shielding samples, the characterization and structural evaluation was performed using X-Ray Diffraction (XRD) and field emission scanning electron microscope (FE- SEM /EDX) supported by EDAX energy dispersive X-ray spectroscopy. The results demonstrate that the incorporation of additives into composite materials enhances the gamma attenuation capacity. The optimal gamma shielding performance is achieved with a 40 wt% ZnB40 composition, which exhibits superior shielding efficacy at lower gamma-ray energies. The MAC value of ZnB40 at 20 keV is about 2.7343 times higher than one of ZnB10 while it is about 1.2675 times greater at 80.9 keV. Moreover, it can be safely said that ZnB40 material can be a suitable option for insulating dentist rooms or buildings that require the use of regular aprons.

The scintillating fiber tracker of the Ziré detector on the NUSES space mission

NUSES is a pathfinder satellite to be deployed in low Earth orbit, equipped with new technologies for space-based detectors. It will carry two payloads: Terzina, for detecting ultra-high-energy cosmic-ray and neutrino air showers, and Ziré, for measuring low energy cosmic rays and gamma rays. Zirè includes several subdetectors: a Fiber TracKer (FTK), a Plastic Scintillator Tower (PST), a calorimeter (CALOg), an AntiCoincidence System (ACS), and a Low Energy Module (LEM). The majority of Ziré will be based on scintillators with Silicon Photomultiplier (SiPM) readout. The FTK is based on thin scintillating fibers readout by SiPM arrays. We assembled several fiber tracker prototypes and tested them with custom developed Front-End Boards (FEBs) based on PETIROC2A and CITIROC. A full, reduced scale protptype of Ziré, Zirettino was designed and assembled. The FTK prototypes and Zirettino were tested in the laboratory and at the CERN PS and SPS facilities.

Advancing gamma radiation shielding with Bitumen-WO₃ composite materials

This research focuses on a manner in which bitumen-WO₃ (petroleum-derived bitumen mixed with tungsten trioxide nanoparticles) materials can be a good shielding candidate against gamma radiation. The objective we set in mixing WO₃ nanoparticles with bitumen was to take advantage of both the bitumen's natural qualities and the WO₃'s excellent shielding capabilities. The prepared composites were tested against various gamma-ray energies emitted from multiple gamma-ray sources to examine their shielding capabilities. The X-ray diffraction (XRD) analysis of the composites' structural properties verified the effective integration of the WO₃ with the bitumen structure. Scanning electron microscopy (SEM) showed that microstructural changes, such as an increase in material density and an improvement in particle dispersion, are caused by a rise in WO3 concentration, which is an essential step toward efficient shielding. Then, the Mean Free Path (MFP), Half-value Layer (HVL), and Linear Attenuation Coefficients (μl) were computed, showing that the composite's capacity to reduce gamma radiation is much enhanced by raising the WO₃ content, especially at lower gamma-ray energies. For instance, at 20 keV, the LAC of 50 wt% WO₃-bitumen composite increased to 9.18 cm⁻1 compared to pure bitumen's 0.40 cm⁻1, while the HVL decreased from 1.73 cm to 0.08 cm, and the MFP dropped from 2.3 cm to 0.1 cm” The results demonstrate the potential of bitumen-WO₃ composites as a sustainable and efficient material for radiation shielding, particularly highlighting their applicability in various sectors, including the development of building wall paints against gamma radiation.

Engineering multifunctional polypropylene nanocomposites: Tailoring structural, thermal, and gamma-ray shielding properties with Ni0.9Zn0.1Fe2O4 doping

This study delves into the structural, thermal and shielding processing of polypropylene (PP) modified with Ni0.9Zn0.1Fe2O4 NPs, synthesized via melt processing. The structural analysis confirms the effective integration of Ni0.9Zn0.1Fe2O4 NPs into the PP matrix, leading to enhanced thermal stability. Furthermore, the impact of incorporating Ni0.9Zn0.1Fe2O4 NPs on the radiation shielding properties of the fabricated PP-based composites was assessed using Monte Carlo simulation. The results reveal a significant increase in the linear attenuation coefficient of the composites with higher concentrations of Ni0.9Zn0.1Fe2O4 NPs, resulting in improved radiation shielding efficiency, particularly at lower gamma-ray energies.

Space approaching assessment of SVOM satellite to other space objects

Abstract The SVOM satellite is one of the joint space projects between China and France. It was successfully launched into the preferred orbit in June 2024. Its goal is to monitor the Gamma Ray Burst in space. The mission consists of 4 main instruments: ECLAIRs, MXT, GRM, and VT. The ECLAIRs telescope is used to detect and position gamma bursts in the X-ray band and low-energy gamma rays. Micro-channel X-ray Telescope (MXT telescope) will make the observation of gamma bursts in the soft X-ray range. GRM (Gamma Ray Burst Monitor) is used to measure the spectrum of high-energy bursts. VT telescope (Visible Telescope) operates in the visible range to detect and observe the visible emission produced immediately after a gamma burst. Based on recent orbit elements for the SVOM satellite, which was available via TT&C, SOCRATES Plus software is used to carry out space collision assessment for the SVOM satellite. SVOM and the accompanying satellite shared the same rocket before they were sent into their own preferred orbits. During the simulations, the mean main orbit elements are derived from the GNSS PV data sets, which can help to know the orbit health of SVOM. On June 27, 2024, the distance between SVOM and the accompanying satellite varies between 509 km and 620 km, and the distance between SVOM and the rocket residual varies between 441 km and 5263 km. On July 2, 2024, the distance between SVOM and the accompanying satellite varies between 1067 km and 1180 km, and the distance between SVOM and the rocket residual varies between 357 Km and 5107 Km. In addition, space approaching the SVOM satellite and other objects is simulated for five-day intervals; it turns out that there are three space objects approaching the SVOM satellite with about 4 km - 5 Km separation.

Lung counting with a highly segmented HPGe detector

A highly segmented High-Purity Germanium (HPGe) detector was used to measure 241Am activity located inside the lungs of an anthropomorphic phantom with various active and passive shield configurations. It was found that the background suppression shield does not play a significant role in reducing the Minimum Detectable Activity (MDA) after veto, based on the segmentation in the depth direction of the HPGe, when measuring low-energy gamma rays. A reduction of up to 57% in the MDA was achieved. The MDA could be further improved by a thinner lateral segmentation and an optimized anti-Compton shield coupled with an active or passive backplate. The new detector application would be particularly useful in mobile whole-body counting units, where the natural background radiation poses a challenge when measuring low-energy gamma rays.

Study of a method for theoretical calculation of the efficiency of a LaBr3(Ce) for detecting gamma-rays from point sources

A theoretical model for calculating the full-energy peak efficiency of scintillator detector is proposed in this paper. The effective penetration distance of gamma-rays in Ø3.81cm × 3.81 cm LaBr3(Ce) crystal, aluminum shell and MgO reflector is analyzed. The calculation model for point source detection efficiency is derived, and the attenuation of gamma-rays in the detector shell is computed by theoretical calculation method. This method is used to calculate the efficiency of LaBr3(Ce) with a size of Ø3.81 × 3.81 cm for detecting gamma-rays from point sources of 137Cs and 60Co located in different positions. Compared with experimental data and Monte Carlo (MC) simulation results, the maximum relative deviation is less than 5%. The attenuation of gamma-rays with an energy of 60 keV is more than 50%. The fitted efficiency calibration curve in the energy range of 60 keV–1500 keV is in good agreement with the simulation results. The results show that this method is suitable for calculating the efficiency of the LaBr3(Ce) detector using point sources, especially for analyzing low-energy gamma ray sources. By taking into account the attenuation of the gamma-rays by the detector shell, the measurement accuracy can be effectively improved. The proposed method can be extended for the efficiency calibration of scintillator detectors with various shapes and provides a new approach for 'source-less' efficiency calibration of detectors.

Examining Low-Energy Gamma-Ray Protection of a New Promising Saudi Cement Product as Alternative Cementitious Material Using Geant4 Software

In modern life, cement products have become an essential material for the foundations in many structural building designs. Because of this, the natural effects of this material need to be tested and cannot be ignored. Modeling interactions of gamma rays with several cementitious compounds is the focus of this study. Gamma radiations exist naturally and artificially, but with limited gamma-ray energies, which are not easy to access for experimental gamma attenuation studies. So in the current work, a wide range of low gamma-ray energies (0.01 to 0.356 MeV) are applied to investigate the gamma radiation attenuation properties theoretically for different cement materials. Also, the Monte Carlo statistical method is applied using the Geant4 toolkit to simulate the results. The outcomes are compared with theoretical values using XCOM to validate at these energies. The effective atomic number ( Z eff ), electron density ( N eff ), and half-value layers (HVLs) for the studied samples are computed based on the simulated mass attenuation coefficient ( μ m ), as expected. The outcomes show good agreement between the simulated results with those calculated theoretically by XCOM within an 11% deviation. The silica fume sample showed a slightly higher μ m value compared with the other samples. The dependence of the photon energy and cement composition on the values of the μ m and HVLs are investigated and discussed. In addition, the values of Z eff and N eff for all cement samples behaved similarly in the given photon energy range, and they decreased as the photon energy increased.

Machine Learning Based Compton Suppression for Nuclear Fusion Plasma Diagnostics

Diagnostics are critical on the path to commercial fusion reactors, since measurements and characterisation of the plasma is important for sustaining fusion reactions. Gamma spectroscopy is commonly used to provide information about the neutron energy spectrum from activation analysis, which can be used to calculate the neutron flux and fusion power. The detection limits for measuring nuclear dosimetry reactions used in such diagnostics are fundamentally related to Compton scattering events making up a background continuum in measured spectra. This background lies in the same energy region as peaks from low-energy gamma rays, leading to detection and characterisation limitations. This paper presents a digital machine learning Compton suppression algorithm (MLCSA), that uses state-of-the-art machine learning techniques to perform pulse shape discrimination for high purity germanium (HPGe) detectors. The MLCSA identifies key features of individual pulses to differentiate between those that are generated from photopeaks and Compton scatter events. Compton events are then rejected, reducing the low energy background. This novel suppression algorithm improves gamma spectroscopy results by lowering minimum detectable activity (MDA) limits and thus reducing the measurement time required to reach the desired detection limit. In this paper, the performance of the MLCSA is demonstrated using an HPGe detector, with a gamma spectrum containing americium-241 (Am-241) and cobalt-60 (Co-60). The MDA of Am-241 improved by 51% and the signal to background ratio improved by 49%, while the Co-60 peaks were partially preserved (reduced by 78%). The MLCSA requires no modelling of the specific detector and so has the potential to be detector agnostic, meaning the technique could be applied to a variety of detector types and applications.

CdZnTe semiconductor-based dual imager combining collimatorless and Compton imaging: Monte Carlo simulation

Compton imaging excels at visualizing gamma rays in the range of several hundred kiloelectronvolts to several megaelectronvolts. However, this technique has limitations in the imaging of low-energy gamma rays. In contrast, collimatorless imaging technique determines the location of a source by analyzing the distribution of interactions. Because the collimatorless imaging technique excels at imaging low-energy gamma rays that are easily shielded by detector components, it can compensate for the shortcomings of the Compton imaging technique. In this study, we propose a dual-mode imaging technique that selects the imaging method depending on the target gamma-ray energy and fuses them during reconstruction. The collimatorless imaging method demonstrated high angular resolution at low energy levels, whereas the Compton image surpasses it starting from 200 keV within its reconstructible range. The angular resolution of the dual-mode image was between those of the two methods. The trend of the positional error of gamma ray energy was similar to that of the angular resolution, and the dual-mode method exhibited the lowest average error of 0.7°. The dual imaging method exhibited higher efficiency, figure of merit, and signal-to-noise ratio by utilizing events from both imaging modalities. In addition, we investigated the geometrical effects of various structures.

Portable gamma-ray instrumentation for inspecting pipe wall thickness: Monte Carlo and experimental investigations

This study aims to assess the efficacy of low energy gamma-ray based instrumentation for inspecting the wall thickness of metallic pipes in industrial situations. The primary motivation behind this work is to explore the feasibility of using a Monte Carlo approach, specifically FLUKA simulations, for radiation-based industrial applications. To achieve this objective, laboratory experiments and FLUKA simulations were conducted using 59.5 keV gamma-rays and a NaI(Tl) scintillation detector. The purpose was to detect changes in pipe wall thickness due to erosion and corrosion, enabling timely intervention to prevent any negative consequences. The ability, scoring commands and geometry design of the FLUKA Monte Carlo code were validated in this study by comparing the computed values of gamma-ray scattered/transmitted intensity with experimental data. Regression lines were derived from the computed and experimental data for scattered and transmitted intensity, providing valuable information for pipe wall inspection. The technique exhibited high sensitivity to changes in the wall thickness of metallic pipes, with a detection capability of 1 mm. However, for higher wall thickness, the sensitivity of the low-energy gamma-ray technique decreased due to the influence of overlying scattering/absorption components in the obtained spectra. The maximum sensitivity limit was found to be for a wall thickness of ∼8 mm for metallic pipes. The excellent agreement between simulation results and actual laboratory methods validates FLUKA's high efficacy in checking the condition of industrial pipelines.

Effect of the brightest gamma-ray burst (GRB 221009A) on low energy gamma-ray counts at sea level

A gamma-ray burst, named GRB 221009A, occurred on 9 October 2022 and is the brightest ever observed GRB, whose frequency is now estimated as once in 10,000 years. This GRB was reported to be observed from many space missions, VLF receivers, and ground observations in optical and radio data. Additionally, a strikingly large number of very high energy (VHE) photons associated with this GRB were observed by the gamma-ray and cosmic ray observatory LHAASO. Though gamma-rays of cosmic origin usually tend to be absorbed by the atmosphere, the high fluence of this GRB, along with the observation of more than 5000 VHE photons (0.5 to 18 TeV) by LHAASO from the ground, emphasises the need to explore other possible ground observations of this GRB.With RA = 288.3° and Dec = 19.8°, the exceptionally bright fluence of this GRB was geographically centred on India. The present paper examines the effect of this GRB using gamma-ray data in a low energy range (0.2–6) MeV obtained using NaI (Tl) detectors located at Tirunelveli (Geographic coordinates: 8.71°N, 77.76°E), India. We report no significant change in the observations associated with GRB 221009A. We discuss the extent of attenuation of gamma-rays in the atmosphere that could explain the reported observations. Further, we investigate the likelihood of ground observation of gamma-rays (< 10 MeV) for a much more intense hypothetical GRB and estimate the parameters, such as distance, fluence, and isotropic energy of such a GRB.

Effectiveness of Radiation Transport Variance Reduction Methods for Wide-Area Environmental Contamination Assay Applications

This study compares the accuracy, efficiency, and reliability of variance reduction (VR) methods for Monte Carlo radiation transport simulations involving wide-area ground plane (i.e., “surface”) and buried (i.e., “volumetric”) gamma source emissions from environmental soil. The simulation models are idealized external exposure scenarios intended as a basis for deriving site-specific dose-based or carcinogenic risk–based regulatory limits in the radiological site remediation process. These simulations are computationally resource intensive since particle tracks are transported from an extremely large source region to a relatively small detector region. For each simulation, several VR methods are compared with metrics of accuracy, efficiency, and reliability. The MCNP deterministic transport (DXTRAN) VR method was most effective for problems involving sources emitting low-energy gamma rays, and a coupled multicode method was more effective for problems involving sources emitting higher-energy gamma rays that undergo significant attenuation in the soil.

Radiation sensitivity of Aspergillus niger of low-energy X-rays and Caesium-137 gamma rays

The radiation sensitivities of Aspergillus niger in several energy X-rays and gamma rays were investigated. Experiment and simulation were conducted to evaluate the X-ray energy spectra and depth dose distributions. The result showed that the microbicidal effectiveness of Aspergillus niger could depend only on the dose regardless of photon energy. It should be noted that the depth dose of low-energy X-rays, including characteristic X-rays of tungsten (LⅢab-ray and Lα-ray of 8.4 keV and 10.2 keV, respectively) is variable even at 1 mm.

Simulating gamma-ray production from cosmic rays interacting with the solar atmosphere in the presence of coronal magnetic fields* *Supported in China by the NSFC (12261160362, 12022502). KCYN is supported by grants provided by the NSFC (12322517, N_CUHK456/22) and RGC (24302721, 14305822, 14308023)

Cosmic rays can interact with the solar atmosphere and produce a slew of secondary messengers, making the Sun a bright gamma-ray source in the sky. Detailed observations with Fermi-LAT have shown that these interactions must be strongly affected by solar magnetic fields in order to produce a wide range of observational features, such as a high flux and hard spectrum. However, the detailed mechanisms behind these features are still a mystery. In this study, we tackle this problem by performing particle-interaction simulations in the solar atmosphere in the presence of coronal magnetic fields using the potential field source surface (PFSS) model. We find that low-energy (~ GeV) gamma-ray production is significantly enhanced by the coronal magnetic fields, but the enhancement decreases rapidly with energy. The enhancement directly correlates with the production of gamma rays with large deviation angles relative to the input cosmic-ray direction. We conclude that coronal magnetic fields are essential for correctly modeling solar disk gamma rays below 10 GeV, but above that, the effect of coronal magnetic fields diminishes. Other magnetic field structures are needed to explain the high-energy disk emission.

Mechanism of measuring ash with low-energy gamma rays for equal coal seam thickness

ABSTRACT Considering the issues related to significant fluctuations and errors in the measured data of the dual-energy gamma-ray online ash analyzer caused by various external factors, this study investigates the impact of factors such as the distance between the detector and the radioactive source, coal seam thickness, moisture content, and particle size range on ash measurements. Additionally, a novel low-energy gamma-ray online ash measurement device is proposed, which ensures uniform coal seam thickness. By utilizing this device, the coal samples subjected to measurement exhibit characteristics such as small particle size, a narrow range of particle sizes, a smooth coal flow surface, consistent coal flow density, a fixed distance between the coal seam and the detector surface, and constant coal seam thickness. These conditions collectively provide optimal circumstances for accurate low-energy gamma-ray ash content measurement. Experimental results indicate that during the separation of Suntuan: Tongting raw coal, the average discrepancy between the measured ash content and the assay ash content was only 0.33%, and the standard deviation of the measured ash content was significantly lower than that of the assay ash content. Specifically, when separating Suntuan: Tongting raw coal, the standard deviation reached its minimum at 0.16%. Comparatively, the low-energy gamma-ray online ash measurement device outperforms the dual-energy gamma-ray online ash analyzer, exhibiting enhanced accuracy and stability in ash measurements, thereby better fulfilling the requirements of daily production.

Gamma radiation shielding properties of unsaturated polyester /Bi2O3 composites: An experimental, theoretical and simulation approach

Conventional gamma radiation shielding materials, such as lead and lead-based composites are heavy and hazardous to human health and the environment. This particular aspect has prompted research into alternative shielding materials. The key objective of this work is to investigate Bismuth Oxide and unsaturated polyester resin (UPR)-based polymer composite material as a radiation shielding. The investigation used a gamma spectrometer consisting of an HPGe detector and the radioactive point sources 60Co, 133Ba, and 137Cs that have energies ranging from 81 keV to 1332 keV for experimentally evaluating mass attenuation coefficient (MAC). Subsequently, the experimental results for MAC were compared with the corresponding values obtained from WinXCOM and Geant4 simulation. Our findings indicated that the mass attenuation coefficient values of experimentally investigated composites align well with the theoretical and simulated values. In addition, we examined the half-value layer (HVL), tenth-value layer (TVL), mean free path (MFP), and radiation protection efficiency (RPE) parameters. From the study, it can be inferred that lead (Pb) can be replaced by UPR+50 wt% Bi2O3 composite for low-energy gamma-ray shielding applications.

Evaluation of long-term robustness of the International System of Reference (SIR) used in radionuclide metrology based on the meta-analysis of its machine-readable database

In support of the CIPM MRA, the reference system in radionuclide metrology (SIR) is a unique experimental facility that has been able to provide continuous key comparison results for 72 radionuclides for 46 years. These measurement data are now available in a machine-readable format, which allows statistical analysis of these measurement results to be performed efficiently. Such a meta-analysis was conducted to verify whether or not the accumulated data confirmed the bold assumption made in the 1970s of the long-term robustness of the system over decades of operation. It was notably assumed that variation in the properties of the standard solution to be measured or the choice of the 226Ra reference source would have no impact on the measurement. For the majority of radionuclides measured by the SIR, the non-parametric significance tests of the null hypothesis carried out in this study gave no evidence, at the 95% confidence level, that the above statement should be reconsidered. However, this meta-analysis revealed a significant impact of solution density in the case of 109Cd, corroborating previous observations made in the case of 241Am where the robustness of an ionization chamber with respect to the density variation of the solution does not appear to be perfect. The extension of the SIR by a liquid scintillation system is under development. It will improve the robustness of international comparison results for those borderline cases where radionuclides emit only low-energy x-rays or gamma rays (<100 keV).

A Compact Particle Detector for Space-Based Applications: Development of a Low-Energy Module (LEM) for the NUSES Space Mission

NUSES is a planned space mission aiming to test new observational and technological approaches related to the study of relatively low-energy cosmic rays, gamma rays, and high-energy astrophysical neutrinos. Two scientific payloads will be hosted onboard the NUSES space mission: Terzina and Zirè. Terzina will be an optical telescope readout by SiPM arrays, for the detection and study of Cerenkov light emitted by Extensive Air Showers generated by high-energy cosmic rays and neutrinos in the atmosphere. Zirè will focus on the detection of protons and electrons up to a few hundred MeV and to 0.1–10 MeV photons and will include the Low Energy Module (LEM). The LEM will be a particle spectrometer devoted to the observation of fluxes of relatively low-energy electrons in the 0.1–7-MeV range and protons in the 3–50 MeV range along the Low Earth Orbit (LEO) followed by the hosting platform. The detection of Particle Bursts (PBs) in this Physics channel of interest could give new insight into the understanding of complex phenomena such as eventual correlations between seismic events or volcanic activity with the collective motion of particles in the plasma populating van Allen belts. With its compact sizes and limited acceptance, the LEM will allow the exploration of hostile environments such as the South Atlantic Anomaly (SAA) and the inner Van Allen Belt, in which the anticipated electron fluxes are on the order of 106 to 107 electrons per square centimeter per steradian per second. Concerning the vast literature of space-based particle spectrometers, the innovative aspect of the LEM resides in its compactness, within 10 × 10 × 10 cm3, and in its “active collimation” approach dealing with the problem of multiple scattering at these very relatively low energies. In this work, the geometry of the detector, its detection concept, its operation modes, and the hardware adopted will be presented. Some preliminary results from the Monte Carlo simulation (Geant4) will be shown.

An easy tool for the Monte Carlo simulation of the passage of photons and electrons through matter

A simple Monte Carlo (MC) algorithm for the simulation of the passage of low-energy gamma rays and electrons through any material medium is presented. The algorithm includes several approximations that accelerate the simulation while maintaining reasonably accurate results. Notably, pair production and Bremsstrahlung are ignored, which limits the applicability of the algorithm to low energies (≲5MeV, depending on the medium). Systematic comparisons for both photons and electrons have been made against the MC code PENELOPE and experimental data to validate the algorithm, showing deviations in the deposited energy smaller than or around 10% in the energy interval of 0.1–5 MeV in light media. The simulation is also valid for heavy media, but with less accuracy as a consequence of the abovementioned approximations. Also X-ray fluorescence is ignored leading to some limitations for photons with energies slightly over the K-shell. The algorithm has been implemented in an open-source Python package called LegPy, which provides an easy-to-use framework for rapid MC simulations aiming to be useful for applications that do not require the level of detail of available well-established MC programs.