Search

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]

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]

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]

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]

The analysis of amplitude spectra from a thin polystyrene-based scintillation counter on muon-enriched and hadron beams of channel 18 of the U-70 accelerator complex in Protvino has been presented. On the basis of statistics of 150 million events on the Hyperon-M setup, the contribution of the -fragmentation processes are highlighted and the cross sections of these processes on hadron and pion beams with a momentum of 7 GeV/c have been measured. In the future, the obtained result may be of interest for the method of analyzing the age of gas fields based on the concentration of helium in natural gas, the formation of which is possible in the reaction of fragmentation of carbon nuclei in interactions induced by high-energy cosmic muons. [ABSTRACT FROM AUTHOR]

We considered the main passive and active neutron methods for detecting fissile material in a sample which are used, for example, in inspection installations and in the control of waste from the nuclear fuel cycle. Calculations are presented to assess the possibilities of using these methods to detect enriched uranium. The differential die-away analysis (DDAA) is considered in detail. A model has been developed for detecting the presence of 235U in a sample by using DDAA with the Geant4 software package. In the developed model, a criterion for determining the mass of 235U is proposed and verified. The proposed model and criterion can significantly simplify the process of developing and optimizing the parameters of expensive devices for detecting fissile substances by creating a digital model. [ABSTRACT FROM AUTHOR]

Gamma rays are electromagnetic radiation with ionising properties resulting from the decay of an unstable atomic nucleus. It can cause cancer-like damage to live cells due to their high penetrating properties. This radiation is widely used in medicine industry and nuclear applications. The development of protective drug agents has started to gain prominence to reduce or stop the damage caused by γ-rays. In this study, the radioprotective effects of 11 different active pharmaceutical ingredients (acetaminophen, amikacin disulphate salt, amoxicillin trihydrate, cephalexin monohydrate, chlortetracycline hydrochloride, gentamicin sulphate, lincomycin hydrochloride, potassium iodide, spectinom dihydrochloride pentahydrate, tetracycline hydrochloride and trimethoprim) were investigated both experimentally and theoretically. Gamma transmission measurements were conducted with a 100 mCi 59.54 keV energy 241Am point source and an ultra-high purity Ge detector. Gamma radiation shielding parameters, such as mass attenuation coefficient (MAC), linear attenuation compound (LAC), half-value layer (HVL), mean free path (MFP) and Zeff, were calculated using the WinXCom program. The obtained results were compared with the experimental results. All samples have gamma radiation shielding ability. However, the PAC8 and PAC9 samples have higher absorption ability than the others (PAC stands for pharmacologically active compound). In addition, it was investigated whether gamma radiation caused any changes in the chemical structure of these active substances with tandem mass spectrometry and FTIR spectroscopy. The present study determined pharmaceutically active substances that can develop new radiation-shielding drugs in nuclear applications such as medical diagnosis and radiation therapy. [ABSTRACT FROM AUTHOR]

The Chasing All Transients Constellation Hunters (CATCH) space mission plans to launch three types of micro-satellites (A, B, and C). The type-B CATCH satellites are dedicated to locating transients and detecting their time-dependent energy spectra. A type-B satellite is equipped with lightweight Wolter-I X-ray optics and an array of position-sensitive multi-pixel Silicon Drift Detectors. To optimize the scientific payloads for operating properly in orbit and performing the observations with high sensitivities, this work performs an in-orbit background simulation of a type-B CATCH satellite using the Geant4 toolkit. It shows that the persistent background is dominated by the cosmic X-ray diffuse background and the cosmic-ray protons. The dynamic background is also estimated considering trapped charged particles in the radiation belts and low-energy charged particles near the geomagnetic equator, which is dominated by the incident electrons outside the aperture. The simulated persistent background within the focal spot is used to estimate the observation sensitivity, i.e. 4.22 × 10 - 13 erg cm - 2 s - 1 with an exposure of 10 4 s and a Crab-like source spectrum, which can be utilized further to optimize the shielding design. The simulated in-orbit background also suggests that the magnetic diverter just underneath the optics may be unnecessary in this kind of micro-satellites, because the dynamic background induced by charged particles outside the aperture is around 3 orders of magnitude larger than that inside the aperture. [ABSTRACT FROM AUTHOR]

In the present work, a new Monte Carlo Geant4 based code called InterDosi 1.0, was used to simulate specific absorbed fractions (SAFs) in the six reference pediatric voxel-based phantoms developed by the International Commission on Radiological Protection (ICRP). The aim of this study was to assess the ability of this code to estimate SAFs in a variety of voxel-based phantoms. A large number of photon SAFs were calculated for pairs of organs corresponding to three sources and 170 target organs/regions. A total of 108 initial photons were uniformly emitted from the source organs with eight discrete energies. In order to speed up the calculation of SAFs, Monte Carlo multithreaded simulations were started on a workstation with 12 threads, and a Geant4 tracking optimization technique was applied that consists in skipping the voxel boundaries when two adjacent voxels share the same material, which seems to reduce the simulation time by an average of approximately 36%. The results showed good agreement with the reference data produced through the MCNP 2.7 code, with average and maximum absolute discrepancies of 0.5% and 7.68%, respectively. We concluded that these results confirm the feasibility of InterDosi code to perform photon internal dosimetry calculations at a voxel level. [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.

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.

Tens of thousands of chemical warfare agents were abandoned in China by the Japanese army after their defeat of invasion of China. Most of the chemical warfare agents have been buried in the soil for more than half a century and the risk of chemical toxicants leakage has increased sharply due to corrosion, so the disposal of these weapons is urgent. The effective disposal and destruction of chemical warfare agents are based on the accurate identification. Prompt gamma neutron activation analysis (PGNAA) is a multi-element analysis technology with low invasion, good safety and high accuracy. In this paper, to study the discrimination potentiality of PGNAA technology on the Japanese chemical projectiles abandoned in China, which can’t be identified by the visual inspection and X-ray imaging technology, the discriminant logic tree of the projectiles was established by investigating and analyzing the data of these abandoned chemical warfare agents, and the simulation model of neutron activation analysis of these projectiles was established by the use of Geant4 toolkit. The prompt gamma spectra of incendiary, yellow projectile and blue projectile excited by 252Cf source, D-D neutron generator and D-T neutron generator with neutron yield of 1×107 s-1 were calculated respectively. For the generation of neutrons from 252Cf source, the Watt fission spectrum was used in our simulations. Monoenergetic 2.5 MeV neutrons and 14.1 MeV neutrons were set as D-D neutron generator and D-T neutron generator respectively in our simulations. The reflection effect of neutron reflectors made of lead or polyethylene on neutrons has also been studied in the simulation. To verify the simulation results, an experimental platform was set up with a D-T neutron generator and a N-type HPGe detector with relative efficiency of 55%. The samples under test were made up of non-toxic and harmless chemical agent, the elements composition and mass fraction were closed to the real chemical warfare agents. The results show that for characteristic elements P and S, the main detected prompt gamma ray energies are 1 266 keV and 2 230 keV, respectively. The analysis of closely-spaced overlapping peaks requires nonlinear least-squares peak fitting, such as the multiple gamma-ray peaks from the hydrogen region. The peak position counts ratio between 882/1763 keV and 1 951/1 959 keV represent an alternative to the existence of S, which is a key criterion for distinguish yellow projectiles from blue projectiles. This study provides the necessary references from the aspects of neutron source selection, neutron reflector material selection, nuclide library establishment and projectile discrimination method for the chemical warfare agents identification system based on PGNAA technology.

Neutron imaging technology as a means of non-destructive detection of materials is complementary to X-ray imaging. Silicon photomultiplier (SiPM), a new type of optical readout device, has overcome some shortcomings of traditional photomultiplier tube (PMT), such as high-power consumption, large volume, high price, uneven gain response, and inability to work in strong magnetic fields. Its application in the field of neutron detection will be an irresistible general trend. In this paper, a thermal neutron imaging detector based on 6LiF/ZnS scintillation screen and SiPM array readout was developed. The design of the detector geometry was optimized by geant4 Monte Carlo simulation software. The optimized detector was evaluated with a step wedge sample. The results show that the detector prototype with a 48 mm × 48 mm sensitive area can achieve about 38% detection efficiency and 0.26 mm position resolution when using a 300 μm thick 6LiF/ZnS scintillation screen and a 2 mm thick Bk7 optical guide coupled with SiPM array, and has good neutron imaging capability. It provides effective data support for developing high-performance imaging detectors applied to the China Spallation Neutron Source (CSNS).

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.

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.

ObjectiveCerenkov photons have distinctive features from scintillation photons. Among them is their polarization: their electric field is always perpendicular to the direction of propagation of light and parallel to the plane of incidence. Scintillation photons are instead considered unpolarized.ApproachThis study aims at understanding and optimizing the reflectance of polarized Cerenkov photons for optical Monte Carlo simulation of scintillation detectors with Geant4/GATE. First, the Cerenkov emission spectrum and polarization were implemented in the previously developed look-up-table Davis model of crystal reflectance. Next, we modified Geant4/GATE source code to account for scintillation and Cerenkov photons LUTs simultaneously. Then, we performed optical Monte Carlo simulations in BGO using GATE to show the effect of Cerenkov features on the photons' momentum at the photodetector face, using two surface finishes, with and without reflector.Main resultsIn this work, we describe the new features added to the algorithm and GATE. We showed that Cerenkov characteristics affect their probability to be reflected/refracted and thus their travel path within a material.SignificanceWe showed the importance of accounting for accurate Cerenkov photons reflectance while performing advanced optical Monte Carlo simulations.

PurposeDesigning and optimizing scintillator-based gamma detector using Monte Carlo simulation is of great importance in nuclear medicine and high energy physics. In scintillation detectors, understanding the light transport in the scintillator and the light collection by the photodetector plays a crucial role in achieving high performance. Thus, accurately modeling them is critical.MethodsIn previous works, we developed a model to compute crystal reflectance from the crystal 3D surface measurement and store it in look-up tables to be used in the Monte Carlo simulation software GATE. The relative light output comparison showed excellent agreement between simulations and experiments for both polished and rough surfaces in several configurations, that is, without and with reflector. However, when comparing them at the irradiation depth closest to the photodetector face, rough crystals with a reflector overestimated the predicted light output. Investigating the cause of this overestimation, we optimized the LUT algorithm to improve the reflectance computation accuracy, especially for rough surfaces. However, optical Monte Carlo simulations carried out with these newly generated LUTs still overestimate the light output. Based on previous observations, one probable cause is the erroneous assumption of perfect couplings between the reflector and crystal and between the crystal and photodetector, which likely results in an important overestimation of the light output compared to experimental values. In practice, several factors could degrade it. Here, we investigated possible suboptimal optical experimental configurations that could lead to a degraded light collection when using Teflon or ESR reflectors coupled to the crystal with air or grease. We generated look-up tables with a mixture of air and grease and showed the effect of three possible sources of light loss: the presence of a small gap between the crystal and the reflector edges close to the photodetector face, the infiltration of grease in the crystal-reflector coupling, and the presence of inhomogeneities in the photodetector-crystal interface.ResultsThe strongest effect is linked to the presence of a small gap of grease between the edges of the reflector material and the crystal (light loss of 10%-12% for 0.2 mm gap). The optical grease infiltrating the crystal-reflector air coupling decreases the light output, depending on the infiltration's extent and the amount of grease infiltrated. Five percent of air in the crystal-photodetector coupling can cause a light output decrease of 2% to 4%. The individual and combined effect of these advanced models can explain the discrepancy of the relative light output obtained with ESR in simulations and experiments. With Teflon, the study indicates that the light output loss strongly depends on the reflectance deterioration caused by grease absorption.ConclusionsOur results indicate that when studying scintillation detector performance with different finishes, performing simulations in ideal coupling conditions can lead to light output overestimation. To perform an accurate light output comparison and ultimately have a reliable detector performance estimation, all potential sources of practical limitations must be carefully considered. To broadly enable high-fidelity modeling, we developed an interface for users to compute their own LUTs, using their surface, scintillator, and reflector characteristics.

Differential die-away analysis (DDAA) technology is a special nuclear material (SNM) active detection analysis technology. Be a nuclear material shielded or not, the technology can reveal the existence of nuclear materials by inducing fission from an external pulsed neutron source. In this paper, a detection model based on DDAA analysis technology was established by geant4 Monte Carlo simulation software, and the optimal sensitivity of the detection system is achieved by optimizing different configurations. After the geant4 simulation and optimization, a prototype was established, and experimental research was carried out. The result shows that the prototype can detect 200 g of 235U in a steel cylinder shield that's of 1.5 cm in inner diameter, 10 cm in thickness and 280 kg in weight.

Evaluating the capabilities of GEANT4 code and COMSOL Multiphysics software can be achieved through coupling for an betavoltaic battery design. Spatial distribution of the deposited energy for the beta particles in the semiconductor transducer has been simulated by using the GEANT4 and then, electron-hole pair generation rate has been obtained. Subsequently, output performances of the battery such as the current-voltage (I–V) characteristics and the maximum electrical power have been determined by using the COMSOL Multiphysics in which the electron-hole pair generation rate from the GEANT4 simulation was utilized as input. Validation is done by considering an optimized planar betavoltaic battery. The results of the current study have been compared with other articles. The results are in good agreement and the relative errors are less than 8%. Our simulation model can be extended to the betavoltaic batteries with other semiconductors and radioactive isotopes, and can be provides a powerful tool for predicting the output performance and optimizing the betavoltaic batteries.

This work describes the creation and experimental validation of DoseMRT, a new software package, and its associated workflow for dose calculations in synchrotron-generated broad beam and microbeam radiation treatment fields. The DoseMRT software package allows users to import CT DICOM datasets into Geant4 for Monte Carlo dose calculations. It also provides basic treatment planning capabilities, simplifying the complexity of performing Geant4 simulations and making our Monte Carlo dose calculation algorithm accessible to a broader range of users. To demonstrate the new package, dose calculations are validated against experimental measurements performed in homogeneous water tank phantoms and the anatomically complex Alderson Radiotherapy Phantom for both broad-beam and microbeam configurations. Additionally, DoseMRT is successfully utilised as the primary method for patient-specific treatment prescription in an in vivo experiment involving tumour-bearing rats at the Imaging and Medical Beamline of the Australian Synchrotron.

Neutron radiography (NRG) is a non-destructive imaging technique for image generation using neutron radiation. In this paper, feasibility studies of neutron radiography for IECF were performed by Geant4 Monte Carlo code. The effects of the different thicknesses of lead on the image and the detection possibility of cavities with different sizes inside a thick lead have been investigated to understand the performance of the device for neutron radiography purposes. The quality of the images was evaluated in terms of contrast. The simulation results showed the efficiency and limitations of NRG for IECF devices and the potential areas where NRG can be performed.

Novel therapeutic strategy in radionuclide therapy use cell-penetrating monoclonal antibodies to carry Auger-emitting radionuclides into the cells. Estimation of dose in normal and tumor cells are important to investigate the efficacy and toxicity of treatment. Monte Carlo simulation is the most suitable method for estimation of absorbed dose at microscopic level. It is therefore useful to carry out Monte Carlo simulation of Auger emitting radionuclides in order to assess the sensitivity of the results with respect to transport approximations generally used in Monte Carlo codes. There are several Auger emitting radionuclides with potential clinical applications, however, based on their half-life 111In is the most suitable for Auger therapeutic purposes and was considered in the present investigation. Geant4 Monte Carlo simulation was performed and specific absorbed dose fraction (or S-values) for 111In were calculated by using different physics model (Standard, Livermore, Penelope and Geant4-DNA) and compared with Medical Internal Radiation Dosimetry (MIRD) S-values. Source was distributed in the cytoplasm (Cy), surface (Cs) and nucleus (N). Average of relative differences (RD) (%) were calculated for self and cross absorbed dose. RD(%) for self-absorption (NßN) were 4.4, 2.36, 6.21 and 1.1 for Standard, Penelope, Livermore and Geant4-DNA respectively. For cross-absorption these values were higher (e.g. for NßCy 15.4, 18.36, 19.21 and 24.8 for Standard, Penelope, Livermore and Geant4-DNA respectively). Cutoff energy considered for electrons and gamma photons affect the results in dose estimation for Auger electrons in Monte Carlo simulation.

The total mass attenuation coefficient of trichloride gadolinium has been investigated utilizing Geant4 compared with WinXCom simulation data at energies; 1–10 MeV. The simulated results are used to calculate the total cross section, atomic and electronic cross sections. The aim of this work is to characterize new materials and their interactions with radiation in order to be able for using in shielding or detection. The GdCl3 is applied for super–Kamiokande detector of neutrons. From our comparison study, it is found that the mass attenuation coefficient of GdCl3 with those of two detectors of X-ray (Si and CdTe) is very closed. Also, the total mass transfer attenuation coefficient increases as high energies increases at pairs effect production. From our comparison study, we can predict that GdCl3 can be a good detector of X-ray and concluded that this material has shown good interaction with electromagnetic radiations at high energies.

Simulation is used by scientists to imitate a real-life experimental setup in order to save time, costs and effort. Geant4, a toolkit based on the Monte Carlo method, has been widely used in investigating the radiation-shielding properties of different materials. In many recent studies, researchers have focused on polymers and their shielding capabilities. Poly(lactic acid) (PLA) is a widely used biopolymer in many applications due to its excellent mechanical properties. However, it has limitations related to its degree of crystallinity and molecular characteristics, which could be improved through blending with other biodegradable polymers such as poly(hydroxybutyrate) (PHB). Previous published studies have shown that the mechanical properties of such blends can be improved further. In this work, the effect of blending PHB with PLA on the photon- and neutron-shielding capabilities will be investigated using Geant4 over a wide energy range, as well as the effect of doping those blends with metal oxides. The results show that the shielding properties of the polymers are affected by blending with other polymers and by doping the polymer blends with different metal oxides, and they confirm that Geant4 is a very reliable tool that can simulate any material's shielding properties against photons and neutrons. [ABSTRACT FROM AUTHOR]

We present a model for the calculation of the production rates of cosmogenic nuclides in extraterrestrial material. The model is based on the Monte Carlo simulation software Geant4. Using this software an application simulating the irradiation of the spherical body with predefined chemical composition by galactic cosmic-ray protons was developed. The fluxes of secondary neutrons and protons generated within the body of the sample are calculated. These are further used for the calculation of the production rates for cosmogenic nuclides. The plausibility of the presented model was tested in case of the well-studied meteoritic sample Knyahinya for which the production rates of cosmogenic nuclides were previously measured and also calculated using MCNP simulation software. The production rates for 3He, 10Be, 21Ne, 22Ne, 26Al, 36Cl, 38Ar, 39Ar, 41Ca and 53Mn have been calculated in Knyahinya meteorite and for 10Be, 26Al and 36Cl in Apollo 17 sample 73,002. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This numerical simulation work investigates the basic physical mechanisms of single events induced in a target layer composed of silicon carbide exposed to natural radiation with atmospheric neutrons at the terrestrial level. Using direct calculations and extensive Geant4 simulations, this study provides an accurate investigation in terms of nuclear processes, recoil products, secondary ion production and fragment energy distributions. In addition, the thorough analysis includes a comparison between the responses to neutron irradiation of silicon carbide, carbon (diamond) and silicon targets. Finally, the consequences of these interactions in terms of the generation of electron–hole pairs, which is a fundamental mechanism underlying single-event transient effects at the device or circuit level, are discussed in detail. [ABSTRACT FROM AUTHOR]

Background: The "Geant4 Application for Tomography Emission" (GATE) toolkit comprises advanced open-source Monte Carlo (MC) code for use in medical imaging and radiotherapy simulations. This study aimed to verify the GATE toolkit results against a water phantom and then to show the dose calculation capabilities of the GATE for radiotherapy. The results were compared with three dose calculation algorithms using patients' Computerized Tomography (CT) data. Materials and Methods: A Linac with a 6 MV photon beam was simulated in the GATE code. The code was verified, head CT images of three patients were inserted into the GATE as realistic phantoms, and simulations were performed for different field sizes and angles. The Percent Depth Doses (PDDs) and transverse profiles were extracted from the GATE simulation and calculation algorithms. Their results were compared regarding the Dose Difference (DD) and gamma index for the PDDs and the Full Width at Half Maximum (FWHM) for the profiles. Results: Using the patient CT data for the PDDs, the gamma pass rate with 3%/3 mm criteria in the comparison between the GATE simulation and algorithms for all fields ranged from 89.4% to 9 8.8%, with an average of 92.8%. The extracted FWHMs from the GATE and algorithms were in good agreement, and their differences ranged from 0.1 to 1.2 mm. Conclusions: The GATE MC toolkit has good potential for implementation in radiotherapy Treatment Planning Systems (TPS) for dose calculations. [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.)

This work introduces the instrument design of the medium-energy proton detector (MEPD, detection range: 30 keV–5 MeV) mounted on the Chinese Fengyun-4B (FY-4B) satellite. Compared to a similar detector on the Fengyun-3E (FY-3E) satellite, this instrument has undergone significant changes due to the different orbital radiation environment and solar lighting conditions. Based on the calculation of the radiation model AP8, the geometrical factor is reduced to 0.002 cm2sr, while that of the MEPD on the FY-3E satellite is 0.005 cm2sr. Another difference is that the sensors in some directions are exposed to direct sunlight for 80 min every day on this orbit, depending on the attitude angle of the satellite, which is much worse than that on the FY-3E satellite. According to the calculation results of transmittance of photons through different materials, a 100 nm thickness nickel film is added in front of the sensors to eliminate light pollution completely. The test using a solar simulator shows that the measure is effective and the detector has no error count when the solar irradiance coefficient is 1.0. In addition, the Geant4 software is applied to simulate the particle transportation process under complete machine condition to check the contamination of electrons in the sensors in all directions after magnetic deflection. The data obtained in orbit show that the instrument works properly, and the data are in good agreement with the AP8 model. The observations of the MEPD on board the FY-4B satellite can provide important support for the safety of spacecraft and theoretical research related to space weather. [ABSTRACT FROM AUTHOR]

This work aims to design the experimental system for investigating the effect of low energy electron irradiation on DNA by means of particle tracking and mechanical strength simulations. The electron beam produced with a DC accelerator having uniform kinetic energy of 35 keV and the current of 10 nA is used as a source of primary electrons. Two situations of DNA irradiation, in vacuo and in ambient, are studied. For both cases, the main objective is to choose appropriate materials to serve as the windows for the in vacuo sample cell and the vacuum window for ambient electron beam extraction. Silicon nitride with varied thickness has been proposed to be used as the electron exposing window for the sample cell and has been examined in Geant4 particle tracking simulation and SolidWorks mechanical strength test while titanium (Ti), beryllium (Be), and high-density polyethylene (HDPE) are considered to be used as the vacuum window and the properties are studied with the same method. The optimal materials are used to construct the system where electron beam is irradiated on a DNA sample. The interaction of electrons with the DNA and its damages is performed with the Geant4-DNA simulation. Based on our limiting conditions, it is found that the DNA double strand breaks can only be observed when the DNA sample is irradiated inside the vacuum part of the accelerator unit. [ABSTRACT FROM AUTHOR]

This paper presents an assessment of nuclear reaction yields of protons, α -particles, and neutrons in human tissue-equivalentmaterial in proton therapy using a simulation with Geant 4. In this study, we also check an enhancement of nuclear reactions due to the presence of Bi, Au, 11 B, and 10 B radiosensitizer nanoparticles. We demonstrate that a proton beam induces a noticeable amount of nuclear reactions in the tissue. Nevertheless, the enhancement of nuclear reaction products due to radiosensitizer nanoparticles is found to be negligible. [ABSTRACT FROM AUTHOR]

X-ray fluorescence computed tomography (XFCT) is a molecular imaging technique that can be used to sense different elements or nanoparticle (NP) agents inside deep samples or tissues. However, XFCT has not been a popular molecular imaging tool because it has limited molecular sensitivity and spatial resolution. We present a benchtop XFCT imaging system in which a superfine pencil-beam X-ray source and a ring of X-ray spectrometers were simulated using GATE (Geant4 Application for Tomographic Emission) Monte Carlo software. An accelerated majorization minimization (MM) algorithm with an L1 regularization scheme was used to reconstruct the XFCT image of molybdenum (Mo) NP targets. Good target localization was achieved with a DICE coefficient of 88.737%. The reconstructed signal of the targets was found to be proportional to the target concentrations if detector number, detector placement, and angular projection number are optimized. The MM algorithm performance was compared with the maximum likelihood expectation maximization (ML-EM) and filtered back projection (FBP) algorithms. Our results indicate that the MM algorithm is superior to the ML-EM and FBP algorithms. We found that the MM algorithm was able to reconstruct XFCT targets as small as 0.25 mm in diameter. We also found that measurements with three angular projections and a 20-detector ring are enough to reconstruct the XFCT images.

One of the on-line range verification techniques in proton therapy is time -of-flight (TOF) measurement for prompt gamma. In this technique, the prompt gamma timing spectra is measured using the time difference between passage of the particle bunch through the target entrance of the beam and the arrival time of the corresponding prompt γ-ray at the detector.In this study, homogeneous PMMA phantom and PMMA phantoms with a slice of bone or air cavity were simulated in GEANT4 simulation. These targets were irradiated with a proton pencil beam with an initial energy of 150 MeV, and the resulting PGT spectra was recorded by scintillation detectors.Then, a code was programmed in MATLAB software to analytically solve the kinematics of proton movement in the phantom, and the PGT spectrum obtained from GEANT4 was given as an input to this software code and the prompt gamma-ray emission profiles was obtained in the phantom. In this study, the effect of the type and position of the heterogeneous slice on the PGT spectrum and the prompt gamma-ray emission profiles resulting from the PGT transformation was investigated. From the comparison of the prompt gamma-ray emission profile resulting from PGT spectra conversion, with the energy deposition spectra resulting from GEANT4 simulation, it was observed that the range shift and the shift of energy deposition location resulting from an inhomogeneity in PMMA have a significant relationship compared to the reference phantom.The presence of an inhomogeneous slice of bone and air cavity with a thickness of 10 mm shifts the range of the proton compared to its range in the reference phantom by 4 mm and 9.6 mm, respectively, and the spectra of energy deposition for these states are respectively 4.8 mm and 9.9 mm shifted relative to the energy deposition spectra of the reference phantom. Therefore, the PGT spectra reflects the proton transit time in the target material and provides the possibility of determining the prompt gamma-ray emission profiles and the possibility of confirming the delivery of the dose to the patient's body.

This study used PHITS and Geant4 code packages to simulate a Leksell Gamma Knife system in order to determine radiation dose distribution in two types of phantoms. The results observed in the water phantom with configurations of single source and 201 sources are in good accord with the prior research, including both simulation and experiment. Several characteristics of Leksell Gamma Knife 4C, such as dose profiles, output factor, FWHM, and penumbra size, are calculated based on Monte Carlo simulations, which show the best consistency with other results. The output factors for collimators of 14 mm, 8 mm, and 4 mm are 0.984, 0.949, and 0.872, respectively. The simulation results with an adult mesh-type reference phantom reveal considerable similarities with the established radiosurgery plans. It indicates that the absorbed dose in brain tumors was highest when utilizing the 18 mm collimator and subsequently reduced with collimator size to 0.65, 0.25, and 0.5 with the 14 mm, 8 mm, and 4 mm collimators, respectively. The absorbed dose has a very low value for other essential organs and decreases with distance from the brain tumor. These findings may explain why the dose to organs decreases linearly as target distance, volume, and collimator size increase.

In this paper, the fast neutron spectra at altitudes of 3 and 5 km were unfolded by the response of Superheated Drop Detectors and using an Adaptive Network-based Fuzzy Inference System (ANFIS). ANFIS is a Takagi-Sugeno Fuzzy Inference System implemented in the framework of adaptive networks. This tool works similarly to human thinking in dealing with uncertain and erroneous problems. The response matrix of five Superheated Drop Detectors under various external pressures was calculated by an application developed using the Geant4 simulation toolkit and was used to obtain inputs of ANFIS. Also, the neutron spectra of the IAEA technical reports were utilized as the targets. The reference spectra were unfolded with RMSEs of 0.005 and 0.011. The relative agreement between the unfolded and reference spectra shows that these detectors and ANFIS can be used as a new technique for unfolding neutron spectra produced by cosmic radiations in the atmosphere.

We investigated the influence of modifying the voltage of an X-ray tube with a tungsten anode between 30 kV and 225 kV, and therefore its photon energy spectrum (up to 225 keV), on the Total Ionizing Dose deposited in a single-mode, phosphorus-doped optical fiber, already identified as a promising dosimeter. Simulation data, obtained using a toolchain combining SpekPy and Geant4 software, are compared to experimental results obtained on this radiosensitive optical fiber and demonstrate an increase of the deposited dose with operating voltage, at a factor of 4.5 between 30 kV and 225 kV, while keeping the same operating current of 20 mA. Analysis of simulation results shows that dose deposition in such optical fibers is mainly caused by the low-energy part of the spectrum, with 90% of the deposited energy originating from photons with an energy below 30 keV. Comparison between simulation and various experimental measurements indicates that phosphosilicate fibers are adapted for performing X-ray dosimetry at different voltages.

Abstract X‐ray diffraction from a solid crystal shows the wave nature of photons. It is an important electromagnetic (EM) physics process when X‐ray photons interact with a crystal. Bragg diffraction, often called Bragg reflection, is a special case of the general form of X‐ray diffraction, known as Laue diffraction. When the Bragg's law is met, the incident photon beam is reflected from the crystal plane behaving as a specular reflection at the Bragg angle. However, the Bragg reflection physical process has not been integrated into the general‐purpose Monte Carlo simulation toolkit Geant4 for particle physics. In the current study, we developed a new EM physical process class “G4CrystalBraggReflection” and a new EM physical model class “G4DarwinDynamicalModel” for modeling the Bragg reflection physical process within a crystal. We added the Bragg reflection physical process to the EM physics category of Geant4. The preliminary results of photon tracking in a silicon crystal slab have shown the feasibility of simulating the Bragg reflection process in addition to the standard EM processes in the framework of Geant4.