Geant4 Toolkit Research Articles

A matrix effect correction method for fissile nuclear material mass measurement by delayed neutrons

Active neutron interrogation (ANI), extensively employed in nuclear safeguards, is sensitive to the presence of special nuclear materials (SNMs). However, the interaction of the matrix material with neutrons weakens the precision of fissile mass measurements by the ANI system. Therefore, it is paramount to ensure that the evaluation of the fissile mass remains unaffected by the matrix and enhances the assay performance of the ANI system. The present work proposes a matrix correction method based on the neutron flux monitor group (NFMG) response to tackle this issue. Based on the varying influence of different matrices on the neutron energies and fluxes, the NFMG response can be used to quantify the matrix effects. This allows the method to enable the identification of matrices already present in the database and has the potential to compensate for unknown matrix effects. To validate the applicability and accuracy of this method, a Shuffler system model and various matrix compositions were developed using the Geant4 toolkit. The results demonstrate that the improved simulated annealing (SA) algorithm exhibits excellent stability when confronted with varying enrichments and distributions of U3O8 materials. When the threshold is set at α ≥ 0.90, the improved SA algorithm achieves a successful identification rate of 90.4% for matrices. Simultaneously, using the response equation, the average relative deviation of the corrected 235U mass is no more than 7%. For the unknown matrix, the correction capability of this method relies primarily on the construction of the reference database and the response equation. In most cases, the average relative deviation of the corrected 235U mass is less than 28%.

Nanodosimetric investigation of the track structure of therapeutic carbon ion radiation part2: detailed simulation

Objectivea previous study reported nanodosimetric measurements of therapeutic-energy carbon ions penetrating simulated tissue. The results are incompatible with the predicted mean energy of the carbon ions in the nanodosimeter and previous experiments with lower energy monoenergetic beams. The purpose of this study is to explore the origin of these discrepancies.Approachdetailed simulations using the Geant4 toolkit were performed to investigate the radiation field in the nanodosimeter and provide input data for track structure simulations, which were performed with a developed version of the PTra code.Main resultsthe Geant4 simulations show that with the narrow-beam geometry employed in the experiment, only a small fraction of the carbon ions traverse the nanodosimeter and their mean energy is between 12% and 30% lower than the values estimated using the SRIM software. Only about one-third or less of these carbon ions hit the trigger detector. The track structure simulations indicate that the observed enhanced ionization cluster sizes are mainly due to coincidences with events in which carbon ions miss the trigger detector. In addition, the discrepancies observed for high absorber thicknesses of carbon ions traversing the target volume could be explained by assuming an increase in thickness or interaction cross-sections in the order of 1%.Significancethe results show that even with strong collimation of the radiation field, future nanodosimetric measurements of clinical carbon ion beams will require large trigger detectors to register all events with carbon ions traversing the nanodosimeter. Energy loss calculations of the primary beam in the absorbers are insufficient and should be replaced by detailed simulations when planning such experiments. Uncertainties of the interaction cross-sections in simulation codes may shift the Bragg peak position.

RapidBrachyIVBT: A dosimetry software for patient-specific intravascular brachytherapy dose calculations on optical coherence tomography images.

Coronary artery disease is the most common form of cardiovascular disease. It is caused by excess plaque along the arterial wall, blocking blood flow to the heart (stenosis). A percutaneous coronary intervention widens the arterial wall with the inflation of a balloon inside the lesion area and leaves behind a metal stent to prevent re-narrowing of the artery (restenosis). However, in-stent restenosis may occur due to damage to the arterial wall tissue, triggering neointimal hyperplasia, producing fibrotic and calcified plaques and narrowing the artery again. Drug-eluting stents, which slowly release medication to inhibit neointimal hyperplasia, are used to prevent in-stent restenosis but fail up to 20% of cases. Coronary intravascular brachytherapy (IVBT), which uses -emitting radionuclides to prevent in-stent restenosis, is used in these failed cases to prevent in-stent restenosis. However, current clinical dosimetry for IVBT is water-based, and heterogeneities such as the guidewire of the IVBT device, fibrotic and calcified plaques and stents are not considered. This study aimed to develop a Monte Carlo-based dose calculation software, accounting for patient-specific geometry from Optical Coherence Tomography (OCT)images. RapidBrachyIVBT, a Monte Carlo dose calculation software based on the Geant4 toolkit v. 10.02.p02, was developed and integrated into RapidBrachyMCTPS, a treatment planning system for brachytherapy applications. The only commercially available IVBT delivery system, the Novoste Beta-Cath 3.5F, with a source train, was modeled with 30, 40, and 60mm source train lengths. The software was validated with published TG-149 parameters compared to Monte Carlo simulations in water. The dose calculation engine was tested with OCT images from a patient undergoing coronary IVBT for recurrent in-stent restenosis at Brigham and Women's Hospital in Boston, Massachusetts. Considering the heterogeneities, the images were segmented and used to calculate the absorbed dose to water and the absorbed dose to medium. The prescribed dose was normalized to 23Gy at 2.0mm from the source center, which is the target volume in IVBT. The dose rate values in water obtained using RapidBrachyIVBT aligned with TG-149 consensus values, showing agreement within a range of 0.03% to 1.7%. Considering the heterogeneities present in the patient's OCT images, the absorbed dose in the entire artery segment was up to 77.5% lower, while within the target volume, it was up to 56.6% lower, compared to the dose calculated in a homogeneous waterphantom. RapidBrachyIVBT, a Monte Carlo dose calculation software for IVBT, was developed and successfully integrated into RapidBrachyMCTPS, a treatment planning system for brachytherapy applications, where accurate attenuation of the absorbed dose by heterogeneities isconsidered.

GEANT4 simulation for controlling and focusing of laser-accelerated proton beam for particle therapy using pulsed power solenoids

Laser-accelerated proton beams (LAP) have inspired innovative applications that can leverage proton bunch properties distinct from those of conventionally accelerated proton beams. A new multifunctional LAP beamline has been proposed, utilizing the GEANT4 toolkit, and the solenoids have been simulated using high-precision components.We present the design of the initial segment of the transport beamline and energy selection system for the effective transport of a radiation pressure acceleration source with a high energy spread. This study examines the effects of solenoids on proton beam quality, specifically focusing on profiles, FWHM, and transmission efficiency. The results obtained using our developed GEANT4 toolkit validate the analytical formulas and findings from the DYNAMION code regarding emittance and proton profiles. Additionally, the presented GEANT4 LAP beamline is capable of calculating the flux of secondary particles, such as neutrons and photons. It was observed that careful attention to the precise structure of the solenoids is critical.

Investigating ultra-high dose rate water radiolysis using the Geant4-DNA toolkit and a Geant4 model of the Oriatron eRT6 electron linac

Ultra-high dose rate FLASH radiotherapy, a promising cancer treatment approach, offers the potential to reduce healthy tissue damage during radiotherapy. As the mechanisms underlying this process remain unknown, several hypotheses have been proposed, including the altered production of radio-induced species under ultra-high dose rate (UHDR) conditions. This study explores realistic irradiation scenarios with various dose-per-pulse and investigates the role of pulse temporal structure. Using the Geant4 toolkit and its Geant4-DNA extension, we modeled the Oriatron eRT6 linac, a FLASH-validated electron beam, and conducted simulations covering four distinct dose-per-pulse scenarios – 0.17 Gy, 1 Gy, 5 Gy, and 10 Gy – all featuring a 1.8 µs pulse duration. Results show close agreement between simulated and experimental dose profiles in water, validating the eRT6 model for Geant4-DNA simulations. We observed important changes in the temporal evolution of certain species, such as the earlier fall in hydroxyl radicals (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{ \\bullet } \ ext{O}\ ext{H}$$\\end{document}) and reduced production and lifetime of superoxide (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{O}}_{2}^{{\\bullet\\:}-}$$\\end{document}) with higher dose-per-pulse levels. The pulse temporal structure did not influence the long-term evolution of species. Our findings encourage further investigation into different irradiation types, such as multi-pulse configurations, and emphasize the need to add components in water to account for relevant cellular processes.

Geant4 Monte Carlo simulation of human exposure to indoor 222Rn from building materials

The present study aimed to develop a Monte Carlo model to estimate the annual effective dose due to radon exposure sourced by radon gas in the walls and floor of a standard model room. With the purpose of developing a tool for radon level assessment in dwellings and workplaces, Geant4 toolkit was used to simulate the energy deposited by gamma rays emitted by radioactive radon progeny in a water phantom positioned at three different locations within the model room. The energy deposition was then used to estimate the annual effective dose through a deterministic approach. The simulation outcomes showed good agreement with experimental data, with the ratio between the simulated and the experimental data displaying the overestimation by a factor of approximately 1.09. Both simulation and experimental data fell within the same range, with a relative deviation of 7.7%. Additionally, the influence of various parameters, such as receptor position in the room, wall, and floor thicknesses, wall cover, and building material bulk density, on the annual effective dose due to radon inhalation in the room was evaluated. Geant4 Monte Carlo toolkit proved to be a reliable tool for radon modeling in real exposure situations.

PHOTON AND PHOTONEUTRON OUTPUTS SIMULATION FROM A TANTALUM CONVERTER AT THE M-30 MICROTRON

Reliable information about the outputs of bremsstrahlung photons and secondary photoneutrons from converters on electron accelerators with mandatory consideration of their technical characteristics is necessary for optimizing the process of sample irradiation and predicting the results of experimental studies. The results of modeling the de- pendence of photon and photoneutron yields and their ratios on the thickness of the tantalum converter (thickness – 0.04; 0.4; 1.0; 4.0; 10.0 mm) are presented at fixed energies of the initial electron beam – 10.0, 12.5, 14.5, 17.5, and 20 MeV. Calculations were carried out for the electron accelerator of the National Academy of Sciences of Ukraine, the M-30 microtron, taking into account its technical characteristics (electron discharge node). The GEANT4 toolkit was used for computer simulation.

18F RADIOISOTOPE YIELD OF POLYTETRAFLUOROETHYLENE ACTIVATION ON THE M-30 MICROTRON

The experimental and modeled values of the yield of the 18F radioisotope formed during the irradiation of polytetrafluoroethylene (Teflon) with bremsstrahlung photons at the maximum energy of 17.5 MeV are presented. The output was determined using the induced activity method. The activation process was carried out on the M-30 microtron of the Institute of Electronic Physics of the National Academy of Sciences of Ukraine. The yields of the 18F radioisotope for the optimized scheme of stimulation of (γ,n)-reactions were modeled by the GEANT4 toolkit, taking into account the technical characteristics of the M-30 microtron electron output unit. The effectiveness of using the formed beam of bremsstrahlung photons for forming the 18F radioisotope was evaluated, taking into account the reaction cross-section for the optimized irradiation scheme. The possibilities of increasing the output of the 18F radioisotope by optimizing the activation time of the samples and their geometric dimensions were analyzed. The proposed approach can be used to optimize photonuclear reaction stimulation schemes at the M-30 microtron for a wide range of nuclei and predict the yields of the radioisotopes formed.

A Comparative Study of Neutron Shielding Performance in Al-Based Composites Reinforced with Various Boron-Containing Particles for Radiotherapy: A Monte Carlo Simulation.

This study aimed to assess and compare the shielding performance of boron-containing materials for neutrons generated in proton therapy and used in boron neutron capture therapy (BNCT). Five composites, including AlB2, Al-B4C, Al-TiB2, Al-BN, and Al-TiB2-BN, were selected as shielding materials, with concrete used as a benchmark. The mass fraction of boron compounds in these materials ranged from 10% to 50%. The Monte Carlo toolkit Geant4 was employed to calculate shielding parameters, including neutron ambient dose equivalent, dose values, and macroscopic cross-section. Results indicated that, compared to concrete, these boron-containing materials more effectively absorb thermal neutrons. When the boron compound exceeds 30 wt.%, these materials exhibit better shielding performance than concrete of the same thickness for neutrons generated by protons. For a given material, its shielding capability increases with boron content. Among the five materials when the material thickness and boron compound content are the same, the shielding performance for neutrons generated by protons, from best to worst, is as follows: Al-TiB2, Al-B4C, AlB2, Al-TiB2-BN, and Al-BN. For BNCT, the shielding performance from best to worst is in the following order: Al-B4C, AlB2, Al-TiB2, Al-TiB2-BN, and Al-BN. The results of this study provide references and guidelines for the selection and optimization of neutron shielding materials in proton therapy and BNCT facilities.

Performance measurements of Total Body PET scanner simulations using the Geant4 toolkit

Total-Body PET (TB PET) is a novel imaging modality that can image the whole body in a single scan. It has increased sensitivity, improved spatial resolution, reduced imaging times compared to conventional clinical PET scanners, and has the potential to detect smaller lesions and multiorgan diseases. Commercially available TB PET scanners include the Siemens Biograph Vision Quadra [1] and the United Imaging uEXPLORER [2]. This study uses the Geant4 toolkit [3] to create a simulation model of two different TB PET detector geometries; Siemens Biograph Vision Quadra and uEXPLORER. Analysis of simulated data and performance measurements were carried out in Python. The study follows the NEMA NU-2 2018 standard [4]. The simulation was used to explore the effect of different scintillator crystals and evaluates the count rate performance and the sensitivity of the scanner. The simulated data was compared to published experimental data from Siemens and Explorer. Good agreement between the count rates of simulated and experimental data was observed for both geometries. The simulated Siemens Quadra measured a system sensitivity value of 178.6 cps/kBq showing a 2% difference compared to the experimental data of 175.3 cps/kBq for LSO crystals. Axial sensitivity profiles plotted also match well. The comparison of different scintillators showed that BGO performs best as it has the highest peak NECR, thus good signal-to-noise ratio. LSO and LYSO also perform well and their physical properties are similar. NaI and CsI exhibit the worst performance; with low true count rates and the random count rates increased almost linearly with activity concentration. Our simulations compared well against experimental data, allowing us to test further scintillator materials and radioisotopes. After implementing image reconstruction and relevant corrections, this simulation can be used for validation of various research ideas in the future. Please click on the 'PDF' for the full abstract!

Rapid cargo verification with cosmic ray muon scattering and absorption tomography

Cosmic ray muon tomography is considered a promising method for the non-invasive inspection of shipping containers and trucks. It utilizes highly penetrating cosmic-ray muons and their interactions with various materials to generate three-dimensional images of large and dense materials, like inter-modal shipping containers, typically not transparent with conventional X-ray radiography techniques. The commonly used methods for imaging with muons are based on muon scattering or absorption-transmission data analysis. Due to large thickness of cargo material in shipping container substantial scattering and absorption occur when muons are passing through cargo. One of the key tasks of customs and border security is to verify shipping container declarations to prevent illegal trafficking, and muon tomography could be a viable choice for this task. In this paper, we demonstrate through Monte Carlo simulations using the GEANT4 toolkit that a combined analysis of muon scattering and absorption data can improve the identification of cargo materials compared to using scattering or absorption data alone. The statistical differences in scattering and absorption data for several cargo materials are quantified. For a particular smuggling scenario where tobacco declared as paper towel rolls, it is demonstrated that the combined analysis can accurately distinguish between tobacco and paper towel rolls with 5.5σ accuracy for detector spatial resolution (FWHM) of 0.235 mm, 4.5σ for 1.175 mm resolution (FWHM), and 3.9σ accuracy for 2.35 mm spatial resolution (FWHM), in a short scanning time of 10 seconds. This rapid detection capability has significant implications for anti-smuggling efforts and cargo inspection.

A novel embedded spherical semiconductor neutron detector efficiency estimation using GEANT4 simulation methodology

The present research work explores on the estimation of thermal neutron detection efficiency for the novel embedded spherical configuration design using GEANT4 toolkit. Initially, single and multiple layer of embedded spherical configurations were designed in geometry category class of GEANT4 toolkit using Boron (10B) converter material followed by, estimation of simulated thermal neutron detection efficiency at different radii which varies between 0.05 μm and 5 μm for both single and multiple layer embedded spherical detector configuration. The maximum thermal neutron detection efficiency obtained for the single layer embedded spherical detector configuration is ∼5.1 % at an optimum (critical) radius of ∼4.55 μm. It was noticed that with the rise in the number of layers of embedded spherical detector configuration the thermal neutron detection efficiency was also increasing. Furthermore, investigation the effect of varying level of Low Level Discriminator and different enrichment level of 10B on the efficiency was also studied. Finally, the histoplot was investigated for a typical 10 layers of embedded spherical detector configuration at typical lower (200 nm) and higher (3 μm) radius.

Tracking performances of the ePIC detector at the Electron-Ion Collider

The ePIC (electron–Proton/Ion Collider) experiment is a future facility at the Electron-Ion Collider (EIC) complex, located at the Brookhaven National Laboratory, USA. It will use ∼70% longitudinally polarized beam of electrons, protons, and light ions to study their collisions to understand the properties of the quarks, gluons, and the strong force responsible for the formation of the nucleus. The layout of the central detector of the ePIC experiment is not symmetric along the beams axis consisting of barrel, forward, and backward detectors to achieve a wide pseudorapidity (|η|< 3.5) coverage. There are further far-forward and far-backward tracking detectors to measure the luminosity and reconstruct the particles and fragments for the study of the exclusive deep-inelastic scattering (DIS) processes. The experiment has a challenging environment due to the presence of the background radiations (synchrotron radiation, beam-gas interactions, minimum-bias events, etc.) which will produce additional background hits on the tracker. The synchrotron radiation is suppressed to some extent by coating the beampipe with a 5μm gold layer. The experiment uses state-of-the-art bent wafer-scale silicon monolithic active pixel sensors (MAPS) with a ∼5μs acquisition window, micro-pattern gas detector (MPGD) with a good time resolution (∼20–30ns), and time-of-flight detectors based on AC-LGAD sensors (time resolution ∼30ps). The timing information of each detector will play a crucial role in track finding and rejecting the background hits utilizing the 4-dimensional tracking (space, time) to ensure the excellent performance of the experiment. The article presents the expected tracking performance of the ePIC detector using the modular ePIC software stack for simulation, reconstruction, and analysis. The Geant4 toolkit is employed for full detector simulations, alongside DD4hep (Detector Description for High Energy Physics) for geometry definition and exchange. The reconstruction incorporates the JANA2 framework, in addition to the tracking and vertexing algorithms inherited from A Common Tracking Software (ACTS).

Predicting the production of 51Mn as a useable radionuclide for PET imaging via the 52Cr(p,2n)51Mn reaction using GEANT4, MCNPX, TALYS, and EMPIRE codes

51Mn is an ideal radioisotope for positron emission tomography (PET) in pancreatic imaging dues to its positron emission characteristics (Eβ+ = 963.7 keV, Iβ+ = 97%) and its advantageous short half-life (T1/2 = 46.2 min). In this study, the production of 51Mn via the 52Cr(p,2n)51Mn reaction was predicted by calculating cross-section and production yield parameters using GEANT4-10.7, MCNPX, TALYS-1.96, SRIM, and EMPIRE-3.2.3 nuclear codes. The GEANT4 and SRIM codes were applied to investigate range of protons in 52Cr target. The cross-section of the 52Cr(p,2n)51Mn reaction was determined by GEANT4, EMPIRE, and four methods of TALYS code. The thick yield of the reaction was evaluated via two different ways of GEANT4 toolkit, and also TALYS and MCNPX codes. At the end, the simulated values were compared to previous reported experimental data, which were in good compatibility to each other.

Exploratory research on the multi-life stages mesh-type model of Caenorhabditis elegans in radiation ecology

To address the lack of effective dose quantification methods for the model organism Caenorhabditis elegans (C. elegans) in radiation ecology research, this study employs remeshing techniques to develop a comprehensive mesh-type model covering multi-life stages, from embryonic to larval (L1, L2, L3, L4) and adulthood. Using these models, Dose Coefficients (DC) for C. elegans in a soil environment under different exposure conditions (external and internal), material settings, and radioactive nuclides (³H, ⁶⁰Co, ⁹⁰Sr, 12⁹I, 1³1I, 1³⁴Cs, 1³⁷Cs) were calculated with the Monte Carlo toolkit Geant4. The results show that the difference in DC, when C. elegans material is set as either biological material or water, is within 5%. Under external exposure conditions, the impact of life stages on the population's average DC is minimal (with a maximum deviation not exceeding 10%). However, the distribution within the population varied significantly across life stages (under external exposure to 137Cs, the dispersion was 12.02% for adults and a considerably higher 60.30% for larvae). The earlier the life stage, the greater the variability in DC distribution within the C. elegans population. Furthermore, correlation analysis indicates a strong relationship between DC and life stages under internal exposure scenarios. The mesh-type model of C. elegans established in this study provides a valuable tool for radiation ecology research and has potential applications in broader research fields.

Analytical parameterization of Bragg curves for proton beams in muscle, bone, and polymethylmethacrylate.

Proton dose calculation in media other than water may be of interest for either research purposes or clinical practice. Current study aims to quantify the required parameters for analytical proton dosimetry in muscle, bone, and PMMA. Required analytical dosimetry parameters were extracted from ICRU-49 report and Janni study. Geant4 Toolkit was also used for Bragg curve simulation inside the investigated media at different proton energies. Calculated and simulated dosimetry data were compared using gamma analysis. Simulated and calculated Bragg curves are consistent, a fact that confirms the validity of reported parameters for analytical proton dosimetry inside considered media. Furthermore, derived analytical parameters for these media are different from those of water. Listed parameters can be reliably utilized for analytical proton dosimetry inside muscle, bone, and PMMA. Furthermore, accurate proton dosimetry inside each medium demands dedicated analytical parameters and one is not allowed to use the water coefficients for non-water media.

Validation of a PGNAA sensor model for bulk material sorting

Global mineral demand is forecast to increase significantly to achieve the transition to renewable energy. Greater volumes of ore of lower grade will have to be mined to meet demand. Techniques to process large volumes of low-grade ore efficiently are being investigated to reduce the cost and impact of mining. One technique is to use sensor information to sort mined material, allowing waste to be discarded early in mineral processing. Prompt gamma neutron activation analysis (PGNAA) is a sensing technique that can provide information on the multi-elemental composition of a bulk sample which can be used for bulk material sorting. This paper presents the development of a Monte Carlo simulation model of a PGNAA sensor for bulk sorting using the Geant4 toolkit. The GEOSCAN sensor (Scantech Australia) was used as a case-study to demonstrate the application of the model. The sensor responses for a range of pure mineral samples (Fe2O3, SiO2, S, Na2CO3 and MnO2) were measured to validate the developed model. The sensitivity of the simulation results to the hadronic and electromagnetic physics models used was tested. It was determined that the PGNAA sensor model can reproduce measurements obtained from the GEOSCAN sensor. In particular, the model can provide a good reproduction of the overall spectral shape and the locations of distinct characteristic peaks. The differences between simulated and experimental results are within 30% on average. It was found that the Geant4 HP neutron model best reproduces the activation peaks observed in experimental measurements. Additionally, the PGNAA spectrum was found to be insensitive to the choice of electromagnetic model for the photon interactions. The validated sensor model provides a useful tool for investigating PGNAA sensor applications including a bulk sorting strategy for new materials, sensor calibration, improvements in signal analysis and optimised sensor design.

Optimization and shielding design of a thermal neutron device based on D-D neutron generator with Geant4 toolkit

Neutron activation analysis is a highly sensitive non-destructive testing technique with important applications in industry, geoscience, medical therapy, etc. This work designed and optimized a thermal neutron device that utilized a portable D-D neutron generator, and the Monte Carlo method with the Geant4 toolkit was applied to simulation. The objective of the optimized design is to maximize the thermal neutron flux at the output surface and increase the utilization efficiency of the neutron generator. A parameter K was defined as a measure of the device's slowing capacity for neutrons and was used to determine the optimized device geometry. The simulation considered the contribution of different types and sizes of moderators and reflectors to the thermal neutron intensity to obtain the optimal size. The shielding protection of the device was then designed. The effectiveness of shielding with different thicknesses was evaluated using three dose reference points. The results indicated that the optimized device can achieve a maximum thermal neutron flux of 1.97 × 105 n∙cm−2∙s−1 at the output surface by using high-density polyethylene (HDPE) as the moderator and nickel as the reflector. It was determined that using 45 cm of HDPE and 9 cm of lead protection in sequence along the neutron head axis would reduce the dose rate at the reference point, located 5 cm from the surface of the device, below the safety limit of 2.5 μSv/h.

Quantitative analysis of dose dependent DNA fragmentation in dry pBR322 plasmid using long read sequencing and Monte Carlo simulations

Exposure to ionizing radiation can induce genetic aberrations via unrepaired DNA strand breaks. To investigate quantitatively the dose–effect relationship at the molecular level, we irradiated dry pBR322 plasmid DNA with 3 MeV protons and assessed fragmentation yields at different radiation doses using long-read sequencing from Oxford Nanopore Technologies. This technology applied to a reference DNA model revealed dose-dependent fragmentation, as evidenced by read length distributions, showing no discernible radiation sensitivity in specific genetic sequences. In addition, we propose a method for directly measuring the single-strand break (SSB) yield. Furthermore, through a comparative study with a collection of previous works on dry DNA irradiation, we show that the irradiation protocol leads to biases in the definition of ionizing sources. We support this scenario by discussing the size distributions of nanopore sequencing reads in the light of Geant4 and Geant4-DNA simulation toolkit predictions. We show that integrating long-read sequencing technologies with advanced Monte Carlo simulations paves a promising path toward advancing our comprehension and prediction of radiation-induced DNA fragmentation.

A Geant4 Monte Carlo toolkit-based radiative transfer model for studying the impact of aerosols

Radiative transfer models are of prime importance in quantifying the earth-atmosphere energy budget. A radiative transfer model based on the Geant4 Monte Carlo toolkit was developed. This model is able to perform calculations of the spectral atmospheric transmittance, surface solar irradiance, as well as the Top of the Atmosphere (TOA) reflected irradiance over the spectral range from 280 nm to 3000 nm. Through this study, the Geant4 toolkit was used to study the effect of rural aerosols concentration on different radiative characteristics. Geant4 radiative calculations in the presence and absence of aerosols were compared to that of DISORT code. For both surface and Top of the atmosphere simulations, good agreement was observed between the two models. Specifically, under atmospheric visibility conditions of 23 km, the mean relative difference between Geant4 and DISORT code was found to be less than 2.46 % for Global irradiance calculations and less than 7.9 % for TOA reflected irradiance. A comparative analysis between the measured total global irradiance in Adrar city and the irradiance estimated by Geant4 demonstrated the general effectiveness of Geant4, with a coefficient of determination of 0.991 and a Mean Absolute Percentage Error (MAPE) of 5.851 %.