Search

AbstractThis paper details the conceptual design of a thermal–to–14-MeV neutron converter consisting of a mixture of lithium and deuterium in a blanket material. Such a device operates a two-step reaction, first generating tritons via thermal neutron absorption in the tritium breeding material, and in the second step, high-energy neutrons are produced either via deuterium-tritium fusion reaction or with tritium reacting with lithium. A thermal–to–14-MeV neutron converter significantly hardens the neutron spectrum by virtually removing thermal neutrons and adding a high-energy, 14-MeV component to the neutron spectrum. While similar concepts have been previously proposed and tested in other reactors, the unique characteristics of the Advanced Test Reactor (ATR), namely, its important thermal flux (up to $$1{0^{15}}$$1015 n∙cm$$^{ - 2}$$ −2∙s$$^{ - 1}$$ −1), make it markedly attractive for obtaining a very large fast neutron flux, usable for irradiation studies under neutron flux conditions prototypical of fusion reactors. The paper provides a description of a new computational scheme developed for handling the coupled neutron-triton transport mechanism using the Geometry and Tracking version 4 (Geant4) toolkit. Resulting neutron spectra and high-energy neutron yields are summarized for different irradiation positions and potential neutron breeder materials. Maximum predicted thermal–to–14-MeV neutron yields are on the order of 2 × 10–4, which is consistent with previous studies found in the literature. Thus, when placed inside the ATR, such a neutron converter will be providing the largest high-energy neutron source available for activation and irradiation studies of materials foreseen for use in fusion reactors. Future steps will involve qualifying the computational scheme using the ATR critical facility using activation foil measurements. [ABSTRACT FROM AUTHOR]

Geant4 offers constructive solid geometry (CSG) for modeling detector geometries, but representing intricate computer-aided design (CAD) structures can be cumbersome. This article presents a novel approach that overcomes this limitation. A new CSG solid type called "half-space solid" enables the equivalent representation of complex CAD solids within Geant4. An automatic program utilizes optimized decomposition algorithms to convert CAD solids into half-space solids. The geometry description markup language (GDML) has been extended to accommodate the half-space solid type alongside the development of interfaces for exporting converted geometries and their subsequent import into Geant4. These advancements establish a fully automated workflow for converting CAD geometries into CSG-based representations suitable for Geant4 simulations. The reliability of the half-space solid-based modeling approach has been verified through comparisons with established Geant4 solids for both simple shapes and a complex fusion reactor model. The excellent agreement obtained from these comparisons demonstrates the efficiency of this new approach. [ABSTRACT FROM AUTHOR]

External exposure to skin from beta-emitter radionuclides following severe reactor accidents or nuclear testing can result in beta burning and other health complications. The skin absorbed dose coefficient (SADC) measures the energy deposition into the skin during such accidents. The U.S. Environmental Protection Agency has published several reports to measure the possible energy deposition into the skin in such accidents. However, the most recent SADC published by Federal Guidance Report (FGR) 12 was computed only at one meter above the contaminated surface. Therefore, it was necessary to develop a model to estimate the absorbed dose coefficients for skin at different heights. In this manuscript, Geant4, a Monte Carlo simulator toolkit, was used to estimate the absorbed dose coefficients from electron sources located on the soil surface with energies ranging from 0.1 to 4 MeV. The energy deposited from primary electrons, secondary electrons, and photons in a 50 µm thick layer of epidermis tissue (Basal Cells Layer) located at a depth of 50 µm from the skin surface was estimated at several discrete heights of human leg phantom. More than 40% of the total energy deposited comes from secondary electrons and photons in energy sources of 0.1 and 0.2 MeV on average, but for higher energies, this percentage is less than 1%, which indicates primary electrons are the main source of the deposited energy in the skin. Furthermore, the results showed the energy deposited into skin closer to the ground was 50–100% higher than the previously estimated doses for 1 m above the ground. The results from Geant4 showed a great correlation (R2 = 0.972) with the FGR 12 data at one meter height, and they were aligned with the published values from FGR 12, which validated the simulation results. Therefore, the calculated dose coefficients for different energy sources and different heights could be used in radiation protection measurements. [ABSTRACT FROM AUTHOR]

This study involved the preparation of natural rubber-based composites incorporating varying proportions of heavy metals and rare earth oxides (Sm2O3, Ta2O5, and Bi2O3). The investigation analyzed several parameters of the samples, including mass attenuation coefficients (general, photoelectric absorption, and scattering), linear attenuation coefficients (μ), half-value layers (HVLs), tenth-value layers (TVLs), mean free paths (MFPs), and radiation protection efficiencies (RPEs), utilizing the Monte Carlo simulation software Geant4 and the WinXCom database across a gamma-ray energy spectrum of 40–150 keV. The study also compared the computational discrepancies among these measurements. Compared to rubber composites doped with single-component fillers, multi-component mixed shielding materials significantly mitigate the shielding deficiencies observed with single-component materials, thereby broadening the γ-ray energy spectrum for which the composites provide effective shielding. Subsequently, the simulation outcomes were juxtaposed with experimental data derived from a 133Ba (80 keV) γ-source. The findings reveal that the simulated results align closely with the experimental observations. When compared to the WinXCom database, the Geant4 software demonstrates superior accuracy in deriving radiation shielding parameters and notably enhances experimental efficiency. [ABSTRACT FROM AUTHOR]

Barium titanium borate glasses doped with ytterbium with the chemical composition of B2O3-TiO2-BaO-Yb2O3 are described as shields exhibiting excellent performance for β and γ applications. This study used the Phy-X and XCOM codes and the GEANT4 toolkit to calculate and simulate the gamma attenuation factors in a 0.02-MeV to 15-MeV range. From the linear attenuation coefficient and mass attenuation coefficient (MAC) values, the half-value layer (HVL), tenth value layer, mean free path (MFP), effective atomic number (Zeff), electronic cross-section, and atomic cross-section have been determined. In addition, the energy absorption build-up factors and exposure build-up factors values of glass samples were estimated for the energy spectrum spans from 0.02 MeV to 15 MeV and penetration depths up to 40 MFP. Additionally, we analyzed the heaviness (H%) of the selected samples, utilizing this crucial metric as a fundamental parameter to comprehend the distinctive properties of diverse materials. Furthermore, we determined the radiation protection efficiency (RPE), and observed that it is prominent at lower energies, gradually decreasing as the energy level rises. Incorporating Yb3O2 resulted in an augmentation of the RPE values, thereby enhancing the shielding capabilities of the glass system. The ESTAR program assessed the β-shielding action of the inspected glasses by determining the total stopping power (TSP) and the continuous slowing down approximation (CSDA) range. The findings indicate that the incorporation of ytterbium positively impacts the density, consequently enhancing the shielding proficiency, of the sample against β- and γ-rays. In BTBaY4 glass, the variant with the greatest concentration of Yb2O3 exhibits the greatest values for MAC, Zeff, and the most minimal HVL. Moreover, this type of glass has low concentrations of Yb2O3 and is free from lead materials, but shows good shielding properties. [ABSTRACT FROM AUTHOR]

This manuscript describes a neutron counting system based on cylindrical fission counters that can monitor neutron activity for high-energy neutron flux above 10 MeV under electrically noisy environments with intense gamma rays. Miniature fission counters with depleted uranium as sensitive material and modular electronics were built for digital signal processing and high-countrate operation. The counters are 9.5 mm in diameter and 71.1 mm in active length. The author presents the results of Monte Carlo simulations of the fission-counter response for selected neutron sources and energies based on ENDF7.1, JENDL-5, and TENDL-2021 nuclear data libraries from 1 meV to 200 MeV. For a white neutron beam (E‾ = 16.36 MeV) that irradiates the front face of a counter, the intrinsic efficiency is evaluated to be (2.24 ± 0.02) × 10−5 counts/n, while the efficiency of the counter in the array appears to increase by at most 6.7%.

The present work is devoted to implementation of the stilbene-based neutron spectrometer energy calibration method. The results of experiments with portable neutron generators and 238PuBe source and scattering materials with known cross sections are used for this method. It is shown that the submitted method makes it possible to carry out fast neutron spectrometry in the energy range from 1 to 15 MeV with the uncertainty of the unfolded neutron energy no more than 200 keV. Neutron spectra unfolding was carried out based on the measured spectra and a Geant4 simulated response matrix. Unfolded spectra were compared with the literature data and reference spectra.

In this paper, we use a Monte Carlo (MC) simulation based on Geant4 to investigate the influence of four parameters on the spatial resolution of the lens-coupled lutetium yttrium orthosilicate (LYSO) scintillator, including the thickness of the LYSO scintillator, the F-number and minification factor of the lens, and the incident position of the gamma-rays. Simulation results show that when the gamma-rays are incident along the lens axis, the smaller the thickness, the larger the F-number, the larger the minification factor, the higher the spatial resolution, with an isotropic point spread function (PSF). As the incident position of the gamma-rays deviates from the lens axis, the spatial resolution decreases, and the PSF becomes anisotropic. In addition, by analyzing the whole physical process of the lens-coupled LYSO scintillator from gamma-rays to secondary electrons to fluorescence photons, we aim to provide a detailed analysis of the influence of each parameter on the spatial resolution. The results show that the PSF of the secondary electrons energy deposition is almost constant in the simulation, which determines the upper limit of the spatial resolution. Meanwhile, the dispersion process of the fluorescence photons can explain the reason why each parameter affects the spatial resolution.

Accurate reconstruction of radiation field and path planning are very important for the safety of operators in the process of dismantling nuclear facilities. Based on radial basis function (RBF) interpolation algorithm, this paper discussed the application of inverse multiquadric radial basis Function (IMRBF) interpolation method to the reconstruction of gamma radiation field, and proved the feasibility of reconstructing a radiation field with multiple γ sources. The average relative errors of IMRBF interpolation results were 4.28% and 8.76%, respectively, for the experimental scenarios with single and double gamma sources. After comparing the consistency between the simulated scene and the experimental scene, IMRBF method and Cubic Spline method were respectively used to reconstruct the gamma radiation field by Geant4 simulation data. The results showed that the interpolation accuracy of IMRBF method was superior to that of Cubic Spline method. Further, more RBF interpolation algorithms were used to reconstruct the multi-γ source radiation field, and then the Probabilistic Roadmap (PRM) algorithm was used to optimize the human walking path in the radiation field reconstructed by different interpolation methods. The optimal paths in radiation fields generated by multiple interpolation methods were compared. The results herein contribute to a comprehensive understanding of RBF interpolation methods in reconstructing γ radiation fields and their application in optimizing paths in radiation environments. The insights may provide valuable information for decision-making in radiation protection during the decommissioning of nuclear facilities.

Owing to their large accelerating gradients, plasma-based accelerators have attracted considerable interest as potential drivers for future, compact electron-positron colliders. Despite great progress achieved in plasma-based electron acceleration, positron acceleration still remains a challenging task, with an efficient positron source being the prerequisite for such acceleration. Here a concept for a compact, two-stage plasma-based positron source is discussed. In the first stage the positrons are created by a multi GeV electron beam produced by a laser-plasma accelerator interacting with a solid density foil. In the second stage the positrons are captured and accelerated in a plasma wave driven by either an electron beam or a laser pulse. Three potential configurations of such a source are considered: (i) a single electron beam is used for both the creation of positrons in the foil and for driving the wakefield in the second stage; (ii) a train of two electron beams is used: the positrons produced by the trailing beam in the foil are captured and accelerated in the second stage by the plasma wave generated by the leading beam; and (iii) a single electron beam is used to produce positrons in the foil and an independent laser pulse is coupled to the second stage to drive the plasma wave. These three configurations show different degrees of effectiveness with positron capture efficiency, varying from less than a percent to almost half of all produced positrons.

High energy X-ray non-destructive testing technology can obtain the internal structure information of the inspected object without destroying it. The multi-rod-beam nature of nuclear fuel assemblies can lead to severe scattering ray effects，which can degrade image quality. In order to correct the interference of scattering ray，this study analyzed the limitations of various methods to solve the interference of scattered rays in the non-destructive testing of nuclear fuel assemblies. Geant4 is used to simulate the nondestructive testing process of nuclear fuel components，and ComptonFlag class is constructed to mark the scattered rays of Compton scattering and remove their interference. The simulation results show that the CNR of defective and intact components in the projection image is increased by 69.02% after the scattering ray interference is removed，which can effectively improve the image quality of non-destructive testing of nuclear fuel assemblies.

Abstract Regarding to their unique physical and mechanical features, glasses and glass–ceramics are suitable materials for shielding purposes. The present study evaluates the shielding properties of the CaF2–CaO–B2O3–P2O5–SrO–Ta2O5 glass system using Monte Carlo GEANT4 and MCNPX codes for X-ray radiations with an energy range of 20 to 100 keV. MAC values of the Ta0, Ta1, Ta2, Ta2.5, and Ta3 samples of the CaF2–CaO–B2O3–P2O5–SrO–Ta2O5 glass were computed using Phy-X/PSD, GEANT4, and MCNPX codes and compared. According to the results, the programs have good compatibility with each other. For instance, in the energy of 40 keV and for the Ta2 sample, GEANT4 and MCNP codes are 1.445765406 and 1.517801204 cm2/g, respectively, indicating 7.419529525 and 2.829628418% differences with 1.562 cm2/g obtained using the Phy-X/PSD software. According to recent estimations, the Ta3 sample of the CaF2–CaO–B2O3–P2O5–SrO–Ta2O5 glass system can be selected as the best shield compared with the other samples.

Power electronic devices face harsh radiation environments in deep space exploration. It is significant to study the reliability of solder joints of electronic devices in radiation environments. The effect of electron irradiation on the microstructure and mechanical properties of Sn3Ag0.5Cu (SAC305) Ball Grid Array (BGA) solder joints was investigated in this work. The results show that the central position of the SAC305 solder joint surface was damaged after electron irradiation. Then the surface of the solder joints was remelted. The shear strength of solder joints increases as the electron irradiation dose rises. When the electron irradiation dose reaches 80 Mrad, the shear strength of the solder joint is enhanced by 8.62% compared with that of the unirradiated sample. After irradiation, the number of dimples on the fracture surface of solder joints increases and the depth of dimples decreases. Geant4 simulation results show that the surface of solder joint is subject to more severe electron impact than the inside of solder joint is. The interaction between electrons and solder joints is the primary reason for the surface remelting of solder joints.

Background Purpose Methods Results Conclusions Gold nanoparticles (GNPs) accumulated within tumor cells have been shown to sensitize tumors to radiotherapy. From a physics point of view, the observed GNP‐mediated radiosensitization is due to various downstream effects of the secondary electron (SE) production from internalized GNPs such as GNP‐mediated dose enhancement. Over the years, numerous computational investigations on GNP‐mediated dose enhancement/radiosensitization have been conducted. However, such investigations have relied mostly on simple cellular geometry models and/or artificial GNP distributions. Thus, it is at least desirable, if not necessary, to conduct further investigations using cellular geometry models that properly reflect realistic cell morphology as well as internalized GNP distributions at the nanoscale.The primary aim of this study was to develop a nanometer‐resolution geometry model of a GNP‐laden tumor cell for computational investigations of GNP‐mediated dose enhancement/radiosensitization. The secondary aim was to demonstrate the utility of this model by quantifying GNP‐induced SE tracks/dose distribution at sub‐cellular levels for further validation of a nanoscopic dose point kernel (nDPK) method against full‐fledged Geant4 Monte Carlo (MC) simulation.A transmission electron microscopy (TEM) image of a single cell showing cytoplasm, cellular nucleus, and internalized GNPs in the cellular endosome was segmented into sub‐cellular levels based on pixel value thresholding. A corresponding material density was allocated to each pixel, and, by adding a thickness, each pixel was transformed to a geometric voxel and imported as a Geant4‐acceptable input geometry file. In Geant4‐Penelope MC simulation, a clinical 6 MV photon beam was applied, vertically or horizontally to the cell surface, and energy deposition to the cellular nucleus and cytoplasm, due to SEs emitted by internalized GNPs, was scored. Next, nDPK calculations were performed by generating virtual electron tracks from each GNP voxel to all nucleus and cytoplasm voxels. Subsequently, another set of Geant4 simulation was performed with both Penelope and DNA physics models under the geometry closely mimicking in vitro cell irradiation with a clinical 6 MV photon beam, allowing for derivation of nDPK specific to this geometry and further comparison between Gean4 simulation and nDPK method.The Geant4‐calculated SE tracks and associated energy depositions showed significant dependence on photon incidence angle. For perpendicular incidence, nDPK results showed good agreement (average percentage pixel‐to‐pixel difference of 0.4% for cytoplasm and 0.5% for nucleus) with Geant4 results, while, for parallel incidence, the agreement became worse (–1.7%–0.7% for cytoplasm and –5.5%–0.8% for nucleus). Under the 6 MV cell irradiation geometry, nDPK results showed reasonable agreement (pixel‐to‐pixel Pearson's product moment correlation coefficient of 0.91 for cytoplasm and 0.98 for nucleus) with Geant4 results.The currently developed TEM‐based model of a GNP‐laden cell offers unprecedented details of realistic intracellular GNP distributions for nanoscopic computational investigations of GNP‐mediated dose enhancement/radiosensitization. A benchmarking study performed with this model showed reasonable agreement between Geant4‐ and nDPK‐calculated intracellular dose deposition by SEs emitted from internalized GNPs, especially under perpendicular incidence — a popular cell irradiation geometry and when the Geant4‐Penelope physics model was used. [ABSTRACT FROM AUTHOR]

AbstractIn 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 ($${Z_{eff}}$$Zeff), electron density ($${N_{eff}}$$Neff), and half-value layers (HVLs) for the studied samples are computed based on the simulated mass attenuation coefficient ($${\mu _m}$$μm), 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 $${\mu _m}$$μm value compared with the other samples. The dependence of the photon energy and cement composition on the values of the $${\mu _m}$$μm and HVLs are investigated and discussed. In addition, the values of $${Z_{eff}}$$Zeff and $${N_{eff}}$$Neff for all cement samples behaved similarly in the given photon energy range, and they decreased as the photon energy increased. [ABSTRACT FROM AUTHOR]

As a new member of the high energy astronomical transient monitoring network, Gamma-ray Transient Monitor (GTM) is an all-sky monitor onboard the Distant Retrograde Orbit (DRO) mission which has been launched in March 2024. In this work, we investigate the space radiation environment of DRO, and study the in-flight background of GTM using GEANT4. The background count rate on each of the 5 GTP detectors of GTM is estimated to be about 800 ∼ 1000 counts/s in the energy range from 20 keV to 1 MeV after one-year operation on orbit. We find that there are two distinct spectral lines clearly visible in the background spectrum, i.e. the 59 keV emission line from the embedded calibration source 241 Am and the 511 keV emission line induced by space radiations, which are suitable for the in-flight energy gain calibration. These results provide important reference for the development of payload, design of observation strategies, in-flight calibration of instrument and research of scientific objectives. [ABSTRACT FROM AUTHOR]

A joint neutron-gamma detection system was designed using a two-stage Monte Carlo simulation approach to identify large-volume ammonium nitrate from buried landmines. To investigate possible spectral anomalies associated with the presence of landmines, the phase space shell concept was used to study the response of a LaBr3 scintillator gamma-ray detector to photons from neutron activation of specific chemical elements in the explosive and soil, as well as the response of a He-3 thermal neutron counter to backscattered thermal neutrons. At a neutron emission energy of 5 MeV, the soil-specific gamma-ray peak energies of 4.94 MeV (Al), 7.65 MeV (Al), and 8.45 MeV (Si) showed a decrease in peak area, which increased as the detection system approached the landmine. The ammonium nitrate-specific peak at 10.82 MeV (N) occurred only in the presence of a landmine. The difference in count rate recorded by the He-3 counter between soil without explosive and soil with explosive increased as the detector system approached the landmine. The combined information from the gamma and neutron detectors provides a good fingerprint for the presence of a suspected landmine. The source shielding, featuring a spherical multi-layered graphite, polyethylene, and lead shielding, improved the useful gamma ray intensity and the registered difference in thermal neutron count rate and reduced the background gamma radiation and direct neutrons reaching the same detectors. [ABSTRACT FROM AUTHOR]

X-ray fluorescence imaging (XFI) can localize diagnostic or theranostic entities utilizing nanoparticle (NP)-based probes at high resolution in vivo, in vitro, and ex vivo. However, small-animal benchtop XFI systems demonstrating high spatial resolution (variable from sub-millimeter to millimeter range) in vivo are still limited to lighter elements (i.e., atomic number Z ≤ 45 ). This study investigates the feasibility of focusing hard X-rays from solid-target tubes using ellipsoidal lens systems composed of mosaic graphite crystals with the aim of enabling high-resolution in vivo XFI applications with mid- Z ( 42 ≤ Z ≤ 64 ) elements. Monte Carlo simulations are performed to characterize the proposed focusing-optics concept and provide quantitative predictions of the XFI sensitivity, in silico tumor-bearing mice models loaded with palladium (Pd) and barium (Ba) NPs. Based on simulation results, the minimum detectable total mass of PdNPs per scan position is expected to be on the order of a few hundred nanograms under in vivo conform conditions. PdNP masses as low as 150 ng to 50 ng could be detectable with a resolution of 600 μ m when imaging abdominal tumor lesions across a range of low-dose (0.8 μ Gy ) to high-dose (8 μ Gy ) exposure scenarios. The proposed focusing-optics concept presents a potential step toward realizing XFI with conventional X-ray tubes for high-resolution applications involving interesting NP formulations. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Geant4 offers constructive solid geometry (CSG) for modeling detector geometries, but representing intricate computer-aided design (CAD) structures can be cumbersome. This article presents a novel approach that overcomes this limitation. A new CSG solid type called “half-space solid” enables the equivalent representation of complex CAD solids within Geant4. An automatic program utilizes optimized decomposition algorithms to convert CAD solids into half-space solids. The geometry description markup language (GDML) has been extended to accommodate the half-space solid type alongside the development of interfaces for exporting converted geometries and their subsequent import into Geant4. These advancements establish a fully automated workflow for converting CAD geometries into CSG-based representations suitable for Geant4 simulations. The reliability of the half-space solid-based modeling approach has been verified through comparisons with established Geant4 solids for both simple shapes and a complex fusion reactor model. The excellent agreement obtained from these comparisons demonstrates the efficiency of this new approach.

The first prerequisite for obtaining correct information from an X-ray diffraction pattern is to accurately remove the background. The most commonly used method in experiments is direct subtraction, which ignores the absorption of the sample and other interactions within the sample such as the photoelectric effect and the counting of photons produced by Compton scattering. The "rolling ball" algorithm and the use of software such as Jade deduction background as well as other deduction methods also have their own limitations. Monte Carlo simulation can identify and count the particles, so it is very important to use it for quantitative analysis of XRD background. In this study, the atomic Form Factor of each element in the air was calculated by the Baró fitting formula and the molecular Form Factor was given by the Debye formula and compared with the calculation results of the independent atomic model. Geant4 was used to simulate XRD for crystalline substances such as bone and nylon and amorphous substances such as water, and the background and real signals were effectively separated in the results, then the XRD background was quantitatively analyzed on this basis. The results show that there is a huge difference in counting between the independent atomic model and Debye's formula,and the Debye method produces more scattered particles. XRD background comes from the air scattering and other types of interactions between photons and matter in the sample, the former contributing the most at small angles, the proportion decreases from 100% to less than 40% with the increase of the scattering angle, and the proportion of the latter increases from 0 to more than 60% with the scattering angle. The results indirectly illustrate the inaccuracy of the background subtraction methods in the experiment. Such as the direct subtraction method not only ignores the absorption of X-ray by the sample, but also ignores the background count caused by other interactions of X-ray photons in the sample. To accurately remove the background, all the counts of background mentioned above must be considered. The Monte Carlo method was used to simulate the XRD background, and the simulation was closely connected with the practice. The same XRD background pattern can be obtained by constructing the same geometric model as the experiment, setting the same physical parameters as the experiment, and using the same sample Form Factor as the experiment. Applying the simulation results to actual experiments may become a more accurate method of background deduction.

BackgroundThe total dose effect of ionization on satellites in Geostationary Earth Orbit (GEO) is caused by space particle radiation in GEO.PurposeThis study aims to combine high-performance cerium-doped yttrium-lutetium silicate (LYSO:Ce) crystals with an aluminum layer to shield the effect of proton irradiation for effective electron radiation dose detection.MethodsFirstly, the detector model was established using Geant4, the shielding effects of different materials for LYSO:Ce detector were compared. Then, the response characteristics of the detector were analyzed, and the factors affecting the output response of the detector at different shielding layer thicknesses were investigated.ResultsThe results showed that the effect of proton irradiation can be eliminated by using 0.022 mm aluminum as the shielding layer. The LYSO:Ce crystal-based detector has a good linear response, and the secondary electrons and photons generated when electrons pass through the shield improve the response sensitivity of the detector. The ionization stopping power of the electron is approximately inversely proportional to the square of the incident electron velocity, and the detector response to radiation is enhanced when the transmission distance between the electron and the detector was appropriately increased. The highest electron detection efficiency of the detector occurs in the energy range of 0.04~1 MeV.ConclusionsThis study on the characteristics of electron radiation dose detector on the basis of LYSO:Ce crystals combined with an aluminum layer provides a technical reference and theoretical support for designing new scintillator space radiation detectors.

The inversion of radiation field distribution is of great significance in the decommissioning sites of nuclear facilities. However, the radiation fields often contain multiple mixtures of radionuclides, making the inversion extremely difficult and posing a huge challenge. Many radiation field reconstruction methods, such as Kriging algorithm and neural network, can not solve this problem perfectly. To address this issue, this paper proposes an optimized inverse distance weighted (IDW) interpolation algorithm for reconstructing the gamma radiation field. The algorithm corrects the difference between the experimental and simulated scenarios, and the data is preprocessed with normalization to improve accuracy. The experiment involves setting up gamma radiation fields of three Co-60 radioactive sources and verifying them by using the optimized IDW algorithm. The results show that the mean absolute percentage error (MAPE) of the reconstruction result obtained by using the optimized IDW algorithm is 16.0%, which is significantly better than the results obtained by using the Kriging method. Importantly, the optimized IDW algorithm is suitable for radiation scenarios with multiple radioactive sources, providing an effective method for obtaining radiation field distribution in nuclear facility decommissioning engineering.

The glass series modified by tungsten oxide was created using the compounds (75-x) B2O3– 10SrCO3– 8TeO2– 7ZnO - xWO3, where x = 0, 1, 5, 10, 22, 27, 34, and 40% mole percentage. A UV–visible spectrophotometer and thermogravimetric-differential thermal analysis (TG-DTA) methods were employed to characterize the specimen's optical and phase transition attributes, respectively. The mass-attenuation coefficient (AC) of all created glasses from BSTZW0 to BSTZ7 was estimated using Geant4 code from 0.05 to 3 MeV and compared to the XCOM software results, with a relative difference of less than 2% between the two results. The increase of WO3 percentage lead to an increase in the Linear-AC at each studied energy, and this is mainly due to the fact that the higher the percentage of WO3 in the glass increases its density which causes an increase in the Linear-AC, so an energy of 0.06 MeV, as an example, the values of the Linear-AC was 4.009, 4.509, 5.442, 6812, 8.564, 9.856, 10.999 and 11.628 cm−1 form BSTZW0 too BSTZW7, respectively. The Half-VL (value layer), Mean-FP (free path), Tenth-VL, and Radiation attenuation performance (RAP) were also calculated for the current BSTZW-glass samples and revealed that BSTZW7 had the best gamma ray attenuation performance at all discussed energies when compared to other studied glass samples.

The absorbed fraction and the S factor represent fundamental quantities in MIRD-based dosimetry of radiopharmaceutical therapy (RPT). Although Monte Carlo (MC) simulations represent the gold standard in RPT dosimetry, dose point kernels (DPK) obtained from analytic range–energy relations offer a more practical alternative for charged-particle dosimetry (β- or α-emitters). In this work, we perform DPK- and MC-based calculations of the self-absorbed fractions and S factors for monoenergetic electrons uniformly distributed in intermediate-size target volumes (~mm to cm) relevant to micrometastasis and disseminated disease. Specifically, the aim of the present work is as follows: (i) the development of an analytic range–energy relation, effective over a broad energy range (100 keV–20 MeV) covering most applications of radiotherapeutic interest; (ii) the application of the new formula to DPK-based calculations of the absorbed fraction and S factor and comparison against MC simulations (both published and present work data) as well as the MIRDcell V2.0.16 software, which uses a similar analytic methodology; and (iii) the study of the influence of simulation parameters (step-size, tracking/production cut-off energies, and ionization model) in Geant4-based calculations of S factors. It is shown that the present DPK-based calculations are in excellent agreement (within 1.5%) with the MIRDcell software, while also being in fair agreement with published MC data as well as with the new Geant4 simulations, with average differences of ~20% for the (sub) mm-sized volumes and ~10% for the cm-sized volumes. The effect of the choice of Geant4 simulation parameters was found to be negligible for the examined target volumes (~mm), except for the use of the Penelope ionization model, which may exhibit noticeable discrepancies (up to ~20%) against the Standard and Livermore models. The present work provides quantitative information that may be useful to both the MC- and DPK-based beta dosimetry of micrometastasis and disseminated disease, which represents an important field of application of RPT. [ABSTRACT FROM AUTHOR]

The harsh radiation environment of Jupiter imposes significant constraints on the shield design of spacecraft. Due to these constraints, traditional aluminum shields cannot meet the radiation shielding requirements needed for the exploration of Jupiter. In this paper, the design for a highly efficient radiation shield structure is proposed that utilizes a combination of high-Z/low-Z elements. A typical exploration orbit of Jupiter is selected, and the energetic particle radiation environment is calculated using the D&G83 model. The Geant4 toolkit is used to evaluate the shielding performance of materials, and quantitative simulations are performed to analyze the shielding efficiency of bilayer and trilayer shield structures under an areal density constraint of 4.5 g/cm2. Based on the simulations, an optimal shield structure is determined. The simulation results show that the integral electron flux with energy greater than 3 MeV is approximately three orders of magnitude greater than that of geostationary orbit with an orbit of 4000 km at the perijove and 5420000 km at the apojove, resulting in an enormous total dose effect. The optimal shield structure is a bilayer structure that comprises of a tantalum outer layer with a density of 3.5 g/cm2 and a polyethylene inner layer with a density of 1.0 g/cm2. This shield has the ability to reduce the total radiation dose to 1559 Gy per year, which is 32 % lower than that of traditional aluminum shields. Findings in this research are critical for design of radiation shields, and can be used for performing reliability analyses and predicting the lifespan of spacecraft during the development process. [ABSTRACT FROM AUTHOR]

The work presents a study of the parameters of secondary X-ray radiation generated during the operation of a sterilization setup based on a high-current pulse-periodic electron accelerator, SINUS-320. The energy of accelerated electrons equals to 500 keV. Therefore, the issues of radiation protection during the operation of the installation are highly topical, which results in the importance of studying the energy spectrum and dose rate of the secondary X-ray radiation. The studies were carried out by statistical simulation using the GEANT4 toolkit. [ABSTRACT FROM AUTHOR]

The Muon Science Establishment (MUSE) at the Japan Proton Accelerator Research Complex (J-PARC) introduced an intense pulse surface muon beam for material science in late 2017. This development at MUSE enables researchers to utilize this highly controlled muon beam to study materials with enhanced accuracy and reliability. Our work aims to investigate proton transmission, surface muon production, contamination on a surface muon beam, and characteristics of the beam at surface muon beamline. Using Monte Carlo simulation programs, GEANT4 and G4beamline, to study interactions between the 3 GeV proton beam and the muon target. The results showed 95.43% proton transmission through the muon target. At the S-line entrance, the surface muon yield is 1.43 × 10 - 7 . The transverse positional distribution and phase space of the surface muon beam were also provided in this study. Our findings present an asymmetry along the horizontal axis and the beam entering the S-line is characterized as divergent, increasing in its transverse size. In summary, the primary proton beam loss at the muon target is 4.57%, which falls within the acceptable range for neutron facility operations that share the proton beam with the muon facility. The characteristics of the surface muon beam will be used for beam dynamic calculation and compared with the result considering the leakage magnetic fields from neighboring beamlines. [ABSTRACT FROM AUTHOR]

While the recent Van Allen Probes mission has provided a wealth of trapped particle measurements, questions still arise from analysis of their data. In particular, 10–100s of keV electrons exhibit dynamics not well understood with current data. Injections of 33–80 keV electrons can occur during both storm and quiet times as shown by Van Allen Probes data. However, due to the Probes' orbit, they can not distinguish precipitation during these events, necessary to quantify injection rates. Analysis of a Low Earth Orbit (LEO) mission measuring these electron populations found enhancements not explained with current injection sources. Future measurements including the quasi‐trapped and precipitating populations are necessary to resolve these dynamics. We present the Medium Energy Electron Telescope to resolve these uncertainties surrounding 10–100s of keV electrons in the inner belt. This solid‐state particle telescope is optimized for these measurements in the high‐flux inner belt environment, with flight heritage from prior instruments. However, novel instrument design is required to measure these populations at fine energy resolution and fit the instrument into a 1U volume, including that of the detectors, electronics, instrument housing, and collimator components. The design is guided by Geant4 analysis and consideration for expected fluxes using the AE9 and AP9 models for a LEO mission and associated tradeoffs are discussed. We develop 59 energy channels with fine nominal resolution (<20%) for 30–800 keV electrons and show proton measurement capabilities for 1.1–>60 MeV populations. Instrument saturation and proton contamination are quantified by analysis of the instrument's response. Key Points: Medium Energy Electron Telescope is a solid‐state particle telescope designed to measure 30–800 keV electrons with fine energy resolution, and 1.1–>60 MeV protonsGeant4‐guided instrument design includes consideration for collimator geometry, material, teeth, and the expected flux environmentCount rates are quantified for proving viability of science measurements, including proton contamination effects and instrument saturation [ABSTRACT FROM AUTHOR]

In this work, the radiation response of bulk GaN and Ga2O3 materials exposed to ground-level neutrons is studied by Geant4 numerical simulation, considering the whole atmospheric neutron spectrum at sea level, from thermal to high energies (GeV). The response of the two materials is compared in terms of the number and type of interactions and the nature of the secondary products produced, particularly in nuclear reactions. Our results highlight the importance of 14N(n,p)14C neutron capture in the radiation response of GaN, leading to large differences in the behavior of the two materials in terms of susceptibility to thermal and intermediate-energy (below 1 MeV) neutrons. [ABSTRACT FROM AUTHOR]

In the present investigation, we examined the efficacy of lithium calcium silicate glasses doped with nickel for various radiation shielding applications. Specifically, we estimated the mass attenuation coefficients (μm) for samples with the composition (11.5–x)CaO-23.5Li2O-(x)NiO-65SiO2 (x = 0, 2.87, 5.75, 8.63, 11.5 mol.%) using Monte Carlo simulation (GEANT4), Phy-X/PSD, and XCOM programs over an energy range of 0.015–15 MeV. The results demonstrate a strong correlation between the extracted μm magnitudes from the simulation and calculation results. Next, we estimated various other parameters, including the linear attenuation coefficients (μ), half-value layer (HVL), tenth-value layer (TVL), mean free path (MFP), effective atomic number (Zeff), fast neutron removal cross sections (ΣR), relative dose distribution (RDD) for gamma rays, energy absorption buildup factors (EABF), and exposure buildup factors (EBF). We also assessed the alpha and beta shielding characteristics of the glass samples by estimating the continuous slowing down approximation range (CSDA) and total stopping power (TSP) magnitudes. Our findings indicate that μm, μ, Zeff, and ΣR magnitudes increased as the ratio of NiO in the samples increased. In contrast, we observed that HVL, TVL, RDD, MFP, EABF, and EBF magnitudes decreased as the NiO ratio increased. A higher percentage of NiO in the samples resulted in the supply of beta and alpha particles with shorter ranges. Overall, we conclude that the lithium calcium silicate glass doped with nickel with an 11.5% NiO percentage is the optimal specimen for obtaining superior photon and charged particle shielding benefits. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the purpose of detecting gravitational waves from space, high-energy particles will infiltrate the satellite's structure and accumulate charges on the test mass, consequently diminishing detection performance. Present investigations into the charging rate of the test mass typically rely on the particle distribution of Earth orbit. However, the influence of the Earth's magnetosphere needs to be considered for the Tianqin detector because of its geocentric orbit. In this paper, artificial neural network is used to fuse satellite data and the galactic cosmic rays model to give the distribution of high-energy particles in the Tianqin orbit. And then, the charging rate is estimated by Monte Carlo simulation. The simulation results show that the flux of hundreds of MeV particles is a little higher than that in Earth orbit, which lead to 3 − 4 e s−1 higher than LISA, i.e. the charging rate of approximately 43 e s−1 during periods of solar minimum and 19 e s−1 during periods of solar maximum. These findings hold substantial implications for guiding the design of the charge management system. [ABSTRACT FROM AUTHOR]

OBJECTIVE This study aims to contribute to the literature the broadened demonstration of energy-related and field size-related responses of three different cylindrical ionization chambers, commonly used for clinical applications of the therapeutic photon beams, using GEANT4 code. METHODS GEANT4 simulation of Varian TrueBeam STx was compared with the real-time measurements. The variations in the output factor (OF) measurements depending on field sizes ranging from 0.6×0.6 cm2 to 30×30 cm2 and photon energies of 6MV, 6MV-FFF, 10MV, 10MV-FFF, and 15MV were recorded for each chamber and compared with the GEANT4 simulations. Response of the chambers was analyzed depending on those OFs. RESULTS The GEANT4 simulation model was validated. All the chambers were in a good agreement within 1.5% for field sizes between 4×4 cm2 and 30×30 cm2. The farmer chamber presented a major deviation up to 22% for the field sizes smaller than 4×4 cm2. Semiflex and pinpoint chambers have an agreement within 2% and 5.5% for 3×3cm2 and 2×2 cm2, respectively. CONCLUSION The chambers evaluated in this study can be used reliably for all photon energies and field sizes between 4×4 cm2 and 30×30 cm2. To obtain accurate measurements for field sizes smaller than 3×3 cm2, it is recommended to use detectors with a smaller sensitive volume instead of the detectors used in this study. [ABSTRACT FROM AUTHOR]

• Simultaneous Geant4 simulations of thousands of multilayer shielding configurations. • The optimum mass allocation for two and three-layer shields can be determined. • Shields with low-Z material on top of high-Z material most effective. • Best Two-layer shields perform similarly to the best with up to five layers. • Results contradict Z-graded shielding, no significant improvements beyond two layers. The rising number of proposed nanosatellite missions with Commercial Off-The-Shelf electronics to higher orbits necessitates innovative, compact, and lightweight radiation shielding. In this study, several thousand multilayer radiation shielding configurations were simulated against trapped particle spectra predicted for a geostationary transfer orbit to demonstrate how material combinations and layer structures can be selected to minimise the total ionising dose inside nanosatellites with constrained mass budgets. The Geant4 Radiation Analysis for Space (GRAS) application was used to calculate ionising dose deposition behind multilayer shielding. Thousands of planar shielding stacks were procedurally generated and simulated on top of silicon plates representing sensitive semiconductor devices. To allow for comparison between configurations, all shielding stacks had a total mass of 1.5 g/cm2, and shielding performance was evaluated based on the total ionising dose absorbed by the silicon plates. The simulations consistently show that configurations with low-atomic-number (low-Z) materials on top of high-Z materials yield the lowest doses. The two- and three-layer mass allocation optimisations demonstrate the non-linear dependence of ionising dose on mass allocation between materials. Optimised polyethylene-lead shields achieved up to 30% lower ionising doses compared to an equal mass of either of the two materials or up to 50% lower than the same mass of aluminium. Contrary to previous claims about Z-graded shielding, no significant improvements were observed for using more than two different materials, and optimisation of multilayer shields tends to reduce them to two-layer structures. Optimal multilayer radiation shielding depends on various factors and must be tailored to specific radiation environments and mission requirements. The primary contributions of this article are the methods presented for achieving this tailoring using open-source software and parallel computing. The multilayer simulations performed for this work resulted in an extensive dataset for multilayer shielding performance that enabled novel visualisations of the ionising dose dependence on shielding composition based on quantitative results. [ABSTRACT FROM AUTHOR]

In this research, using Geant4 Monte Carlo simulation tool, we have investigated the shielding properties of aluminum oxide, magnesium fluoride, aluminum fluoride, titanium dioxide, magnesium diboride, magnesium silicide, calcium disilicate, and Fluental in the energy range of 0.015 to 10 MeV. In this review, we have calculated and analyzed the linear attenuation coefficient (LAC) and mass attenuation coefficients (MAC), half-value layer (HVL), tenth value layer (TVL), mean free path (MFP), and effective atomic number, effective electron density, equivalent atomic number and buildup factor. In the continuation of the work, we have compared the calculated results of mass attenuation coefficient by Geant4 Monte Carlo simulation tool with the experimental results of others and with the simulation data by XMuDat code, and they have a very low relative error and are in good agreement with each other. Finally, the results obtained for the selected materials are shown in appropriate figures. [ABSTRACT FROM AUTHOR]

Polyimide material is widely used in the aerospace field, but its secondary electron emission yield is high. In this study, a graphene coating was used to suppress its secondary electron emission, and the secondary electron emission yield of graphene-coated materials with different thicknesses was calculated using the GEANT4 numerical simulation method. The suppression effect of different thicknesses of graphene coatings on the secondary electron emission was analyzed. The simulation results showed that the optimal graphene coating thicknesses for the lowest secondary electron yield of polyimide materials were 1 nm and 5 nm, which reduced the secondary electron emission yield by 13% in terms of simulation. The 5 nm graphene coating reduced the secondary electron emission yield by 6% compared to the polyimide material from an experimental perspective. The 5 nm coating showed better results at higher energies and was experimentally verified by preparing five layers of graphene coating, which showed good agreement between the simulation and experiment. Meanwhile, with the increase in graphene coating thickness, the surface secondary electron emission displacement range decreased, and the secondary electrons produced at the surface were of low energy. The results of this study can provide technical reference for polyimide in aerospace applications and secondary electron emission simulation. [ABSTRACT FROM AUTHOR]

Plastic scintillator detectors are widely utilized in radiation measurement due to their unique characteristics such as fast decay time, low production cost, availability for large-scale production, and tissue equivalence. However, their limited photoelectric absorption cross-section and poor energy resolution make it challenging to accurately detect γ-ray photopeaks. The absence of high-energy γ-ray photopeaks poses a challenge in the energy calibration of plastic scintillator detectors, which is the foundation for radiation energy detection. Nevertheless, it is feasible to calibrate a plastic scintillator detector using the Compton peaks. Numerous studies on the plastic scintillator detector energy calibration based on the Monte Carlo method were reported, but most of them cannot directly simulate energy spectra or calculate the energy values of Compton peaks. An energy calibration method combined with optical simulation was proposed to overcome this obstacle in this paper. This method describes physical processes in plastic scintillator detectors more comprehensively than energy calibration methods based on the regular Monte Carlo simulation. Furthermore, it does not rely on empirical formulas to determine energy resolution. An optical model of the plastic scintillator detector built with GEANT4 10.7 was used to describe the scintillation properties of the plastic scintillator, the properties of optical surfaces, and the photoelectric conversion and photoelectron multiplication processes of the photomultiplier tube. Thus, this model could accurately simulate the energy deposition of γ-rays, the transportation and collection of the scintillation light in the scintillator, as well as the photoelectric conversion process of the scintillation light and photoelectron multiplication process at the photomultiplier tube. These allow for an accurate simulation of the experimental energy spectrum. The simulated energy spectra were calibrated using the photopeaks of low-energy γ-rays. Since the simulated energy spectra are reasonable approximations of experimental energy spectra, the energy values of the Compton peaks in the experimental spectra are the same as Compton peaks in the calibrated simulated energy spectra. Two radiation sources of 137Cs and 60Co were used to calibrate the plastic scintillator detector in the experiment based on this method, and the energy calibration of the plastic scintillator detector was completed using Compton peaks of 137Cs and 60Co. The relative error of the Compton peak energy resolution for 137Cs between the simulated energy spectrum and the calibrated experimental energy spectrum is 0.70%. For 60Co, the value is 0.91%. Either value is less than 1%, which in turn verifies the agreement between simulated energy spectra and experimental energy spectra, and also demonstrates the reliability of the energy calibration result.

This paper reviews the ecosystem of GATE, an open-source Monte Carlo toolkit for medical physics. Based on the shoulders of Geant4, the principal modules (geometry, physics, scorers) are described with brief descriptions of some key concepts (Volume, Actors, Digitizer). The main source code repositories are detailed together with the automated compilation and tests processes (Continuous Integration). We then described how the OpenGATE collaboration managed the collaborative development of about one hundred developers during almost 20 years. The impact of GATE on medical physics and cancer research is then summarized, and examples of a few key applications are given. Finally, future development perspectives are indicated.

In radiotherapy, X-ray or heavy ion beams target tumors to cause damage to their cell DNA. This damage is mainly induced by secondary low energy electrons. In this paper, we report the DNA molecular breaks at the atomic level as a function of electron energy and types of electron interactions using of Monte Carlo simulation. The number of DNA single and double strand breaks are compared to those from experimental results based on electron energies. In recent years, DNA atomistic models were introduced but still the simulations consider energy deposition in volumes of DNA or water equivalent material. We simulated a model of atomistic B-DNA in vacuum, forming 1122 base pairs of 30 nm in length. Each atom has been represented by a sphere whose radius equals the radius of van der Waals. We repeatedly simulated 10 million electrons for each energy from 4 eV to 500 eV and counted each interaction type with its position x, y, z in the volume of DNA. Based on the number and types of interactions at the atomic level, the number of DNA single and double strand breaks were calculated. We found that the dissociative electron attachment has the dominant effect on DNA strand breaks at energies below 10 eV compared to excitation and ionization. In addition, it is straightforward with our simulation to discriminate the strand and base breaks as a function of radiation interaction type and energy. In conclusion, the knowledge of DNA damage at the atomic level helps design direct internal therapeutic agents of cancer treatment.