Search Results (214)

This study investigates whether detector materials with an effective atomic number (Z_eff), density, and light output higher than cesium iodide (CsI) could provide images of better quality in dual-energy cone beam computed tomography (CBCT) breast examinations. Seven different detector material configurations were applied in a simulated micro-CBCT system using GATE v.9.2.1 (GEANT4 application for tomographic emission). Four breast phantoms, containing microcalcifications of Type I and Type II, were imaged. Planar images and tomographic data were analyzed. Microcalcification CNRs (contrast-to-noise ratios) were calculated for each configuration. CZT (cadmium zinc telluride) and GAGG (gadolinium aluminum gallium garnet) materials show a 3–17% increase in relative HAp (hydroxyapatite)-CNR values towards CsI. Full article

Objectives: The main aim of this study consists of testing the consistency and reliability of the BIANCA (BIophysical ANalysis of Cell death and chromosome Aberrations) biophysical model across different radiation transport codes in the framework of cancer ion-therapy research. Methods: Spread-Out Bragg Peak (SOBP) profiles for protons, helium ions and carbon ions were simulated at three different depth ranges (2–3 cm, 5–8 cm, and 10–15 cm) applying two radiation transport codes, FLUKA and Geant4. While BIANCA has been interfaced to FLUKA in a previous work, an interface with Geant4 was purposely developed in this work. Cell survival along all considered SOBP profiles was predicted by BIANCA for two cell lines with very different radiosensitivities: Squamous Cell Carcinoma (SCC), with α/β = 12.68 Gy, and chordoma, with α/β = 2.37 Gy. The agreement between the predictions obtained from the two approaches was quantitatively evaluated by means of Root Mean Square Error (RMSE) and Gamma Index analysis, both for physical dose distributions and for cell survival predictions. Results: The comparison between FLUKA and Geant4 simulations demonstrated good agreement. The Gamma Index analysis yielded passing rates exceeding 94.9% for physical dose profiles (criteria: 3%/2 mm) and 96.0% for cell survival probabilities (criteria: 2%/2 mm) across all considered ion species (protons, He, C) and depths. Root Mean Square Error (RMSE) analysis confirmed average discrepancies below 2.5% for physical dose and 1% for biological survival. Conclusions: This study shows that the BIANCA model can be applied to predict cell killing along hadron therapy beams when interfaced both with FLUKA and with Geant4. Furthermore, the successful implementation of the interface with Geant4 expands the accessibility and applicability of BIANCA, paving the way for its future integration into different transport codes and/or treatment planning systems. Full article

Proton therapy offers superior dose localization, yet the biological effects of low-energy protons relevant to superficial tissues remain underexplored. We report the design and validation of a proton irradiation setup developed at the Tandem Accelerator of NCSR “Demokritos” for controlled radiobiological experiments. Monte Carlo simulations using Geant4 and Monte Carlo Damage Simulation (MCDS—Monte Carlo Damage Simulation) were used to determine proton energy spectra, linear energy transfer (LET), and predicted DNA damage yields. A single layer (15–20 μm in thickness) of human keratinocytes (HaCaT) was irradiated at doses from 0.65 to 3.65 Gy, and γ-H2AX foci were quantified as markers of tracks including one or more DNA double-strand breaks. The system achieved a uniform dose rate of 0.37 Gy/min, as calculated with Geant4, with a mean proton energy of 4.1 MeV (LET ≈ 8 keV/μm). A strong correlation (R² = 0.93) was observed between proton dose and γH2AX foci per nucleus (~10 foci/Gy), reflecting damage-inducing proton tracks rather than individual DNA double-strand breaks. At higher doses, an increased fraction of cells exhibited pan-nuclear γH2AX staining, characterized by a diffuse γH2AX signal throughout the nucleus and commonly associated with extensive or clustered DNA damage and global chromatin phosphorylation. These responses are consistent with the well-established dense ionization patterns produced by low-energy protons, as indicated by the LET spectrum and supported by MCDS-predicted clustered damage yields. While the γH2AX assay does not directly resolve simple versus complex DNA lesions, the agreement between Monte Carlo modeling and the observed cellular stress responses indicates that the irradiation platform reliably reproduces the expected biological signatures of low-energy proton exposure. Consequently, the developed system provides a robust experimental tool for systematic investigations of cellular radiosensitivity and radiotoxicity, with potential applications in skin dosimetry and radioprotection. Full article

The global shortage of ³He resources has created an urgent need for alternative neutron detection technologies in applications such as national security, neutron scattering, and nuclear energy. This study designed and developed a zero-dimensional planar high-efficiency thermal neutron detector based on a boron-lined multi-wire proportional chamber (MWPC) employing two distinct efficiency-enhancement approaches: a multilayer structure and grazing-incidence geometry. For ease of use, a sealed detector has been developed, eliminating the need for gas cylinders. Geant4 simulations were utilized to optimize the ${\mathrm{B}}_4\mathrm{C}$ thickness of conversion layer and evaluate $\gamma$-ray sensitivity. Prototype detectors were fabricated and experimentally validated at the 20th beamline (BL20) of China Spallation Neutron Source (CSNS). Simulation results indicate that the optimal ${\mathrm{B}}_4\mathrm{C}$ thickness varies with layer count and neutron wavelength, measuring approximately 2.0 µm at 1.8 Å and 1.5 µm at 4 Å for a 10-layer structure, with $\gamma$-ray sensitivity below $5\times {10}^{-6}$. Experimental measurements demonstrate that a five-layer detector achieved neutron detection efficiencies of 28.0 ± 1.5% at 4.78 Å and 17.8 ± 1.8% at 2.87 Å, while a two-layer detector at 11.5° incidence attained 19.2% and 11.7%. This research lays the groundwork for developing large-area, high-efficiency, position-sensitive neutron detectors. Full article

A compact, in situ beta-spectroscopy approach for real-time monitoring of Strontium-90 (Sr-90) in contaminated groundwater has been investigated. Two inorganic scintillators, CaF₂(Eu) and ZnSe(Al,O), were coupled to silicon photomultipliers (SiPMs) and evaluated experimentally using custom front-end electronics. This was also modelled with Monte Carlo simulations using the Geant4 toolkit. Although simulations correctly predicted ZnSe(Al,O) has an advantage due to its higher light yield and optical transport, experimental measurements additionally revealed practical limitations of the readout electronics which were not captured in the simulation model. ZnSe(Al,O) showed excellent agreement with the simulated detector response (R² ≈ 0.86; ${\chi }^2$/NDF ≈ 27). It also attains a higher relative detection efficiency (∼61.5%), yielding faithful capture of the composite Sr-90/Y-90 spectrum with only minor suppression at the extreme high-energy tail. CaF₂(Eu) exhibits a deficit at low-mid energies and an apparent enhancement in the high-energy tail. This is consistent with threshold and photon-statistics losses and leads to poorer agreement with simulation (${\chi }^2$/NDF ≈ 179) and lower overall efficiency (∼22.7%). These findings identify ZnSe(Al,O) as the stronger candidate for an underwater, in situ Sr-90 beta-spectroscopy system and motivate targeted optimisation of SiPM coupling and crystal-edge reflectivity in future designs. Full article

Fast neutron shielding is a critical component of radiation protection design. Conventional exponential attenuation models based on the narrow-beam (beam approximation) assumption often exhibit large deviations in realistic geometries because they neglect the contribution of scattered neutrons—an effect that becomes particularly prominent for thick hydrogenous shields such as polyethylene. To improve the accuracy of rapid shielding estimates, this study systematically investigates how the “source–shield–detector” geometric configuration influences fast neutron scattering in polyethylene. To overcome the limited adaptability of traditional build-up factor corrections in complex geometries, we propose a physics-informed scattering correction (SC) model. By introducing key geometric parameters—source-to-shield distance, shield thickness, and detector distance—the model dynamically modifies the classical exponential attenuation formulation and analytically integrates the scattered-neutron contribution to the detector flux. Validation against 70 representative geometric configurations simulated with the Monte Carlo code Geant4 shows that the proposed model reduces the mean absolute percentage error (MAPE) from approximately 54% for the exponential attenuation model to approximately 20%, effectively addressing severe flux underestimation in moderately thick shielding cases (5–20 cm). The results provide a practical and reliable tool, as well as a semi-empirical theoretical basis, for fast and accurate engineering estimation of polyethylene-based fast neutron shielding. Full article

A conceptual design study is presented for a hemispherical, two-chamber water Cherenkov detector instrumented with bladder-embedded light traps. The detector consists of a rigid aluminium vessel enclosing a water volume that is divided into an outer, optically black chamber and a inner, reflective chamber lined by a flexible bladder. Arrays of light-trap modules, based on plastic scintillators with wavelength-shifting elements and thin silicon photomultipliers, are integrated into the bladder and selected inner surfaces. This geometry is intended to enhance muon tagging, increase acceptance for inclined air showers, and enable improved discrimination between electromagnetic and hadronic components. The study describes the mechanical and optical layout of the detector, the baseline aluminium housing, and the use of 3D-printed hexagonal prototypes to validate integration of the bladder and readout electronics. A first-order structural assessment based on thin-shell and plate theory is presented, indicating large safety margins for the hemispherical shells and identifying the flat base as the mechanically most loaded component. While GEANT4 simulations for detector response to extensive air showers in the atmosphere and performance measurements are left to future work, the present study establishes a mechanically validated, costed baseline design and outlines the steps needed to assess its impact in air-shower arrays. Full article

The accurate simulation of sub-GeV particle detectors is essential for interpreting experimental data and optimizing detector design. This work identifies and addresses several critical aspects in modeling such detectors, taking as a case study the High-Energy Particle Detector (HEPD-02), a space-borne instrument developed within the CSES-02 mission to measure electrons in the ∼3–100 MeV range, protons and light nuclei in the ∼30–200 MeV/n. The HEPD-02 instrument consists of a silicon tracker, plastic and LYSO scintillator calorimeters, and anticoincidence systems, making it a representative example of a complex low-energy particle detector operating in Low Earth Orbit. Key challenges arise from replicating intricate detector geometries derived from CAD models, selecting appropriate hadronic physics lists for low-energy interactions, and accurately describing the detector response—particularly quenching effects in scintillators and digitization in solid-state tracking planes. Particular attention is given to three critical aspects: the precise CAD-level geometry implementation, the impact of hadronic physics models on the detector response, and the parameterization of scintillation quenching. In this study, we present original solutions to these challenges and provide data–MC comparisons using data from HEPD-02 beam tests. Full article

Lightweight, lead-free polymer–mineral composites have attracted increasing interest as radiation-attenuating materials for applications where reduced mass and environmental compatibility are required. In this work, the $\gamma$-ray attenuation behavior of poly(ether ether ketone) (PEEK) reinforced with natural palygorskite and pumice was evaluated at filler concentrations of 10–40 wt%. Photon interaction parameters, including the linear attenuation coefficient ($\mu$), half-value layer (HVL), mean free path ($\lambda$), and effective atomic number ($Z_{\mathrm{eff}}$), were computed over the energy range 15 keV–15 MeV using the Phy-X/PSD platform and validated through full Geant4 Monte Carlo transmission simulations. At 15 keV, $\mu$ increased from $1.46{\mathrm{cm}}^{-1}$ for pure PEEK to $4.21{\mathrm{cm}}^{-1}$ and $8.499{\mathrm{cm}}^{-1}$ for the 40 wt% palygorskite- and pumice-filled composites, respectively, reducing the HVL from 0.69 cm to 0.24 cm and 0.11 cm. The corresponding $Z_{\mathrm{eff}}$ values increased from 6.5 (pure PEEK) to 9.4 (40 wt% palygorskite) and 15.3 (40 wt% pumice), reflecting the influence of higher-Z oxide constituents in pumice. At higher photon energies, the attenuation curves converged as Compton scattering became dominant, although pumice-filled PEEK retained marginally higher $\mu$ and shorter $\lambda$ up to the MeV region. These findings demonstrate that natural mineral fillers can enhance the photon attenuation behavior of PEEK while retaining the known thermal stability and mechanical performance of the polymer matrix as reported in the literature, indicating their potential use as lightweight, secondary radiation-attenuating components in medical, industrial, and aerospace applications. Full article

This study evaluates lead-free high-density polyethylene (HDPE) composites reinforced with high-Z oxides (Bi₂O₃, WO₃, Gd₂O₃, TeO₂, and a Bi₂O₃/WO₃ hybrid) as lightweight materials for gamma-ray and fast-neutron shielding. A hybrid computational framework combining Phy-X/PSD with Geant4 Monte Carlo simulations was used to obtain key shielding parameters, including the linear and mass attenuation coefficients (μ, μ/ρ), half-value layer (HVL), mean free path (MFP), effective atomic number (Z_eff), effective electron density (N_eff), exposure and energy-absorption buildup factors (EBF, EABF), and fast-neutron removal cross section (Σ_R). The incorporation of heavy oxides produced a pronounced improvement in gamma-ray attenuation, particularly at low energies, where the linear attenuation coefficient increased from below 1 cm⁻¹ for neat HDPE to values exceeding 130–150 cm⁻¹ for Bi- and W-rich composites. In the intermediate Compton-scattering region (≈0.3–1 MeV), all oxide-reinforced systems maintained a clear attenuation advantage, with μ values around 0.12–0.13 cm⁻¹ compared with ≈0.07 cm⁻¹ for pure HDPE. At higher photon energies, the dense composites continued to outperform the polymer matrix, yielding μ values of approximately 0.07–0.09 cm⁻¹ versus ≈0.02 cm⁻¹ for HDPE due to enhanced pair-production interactions. The Bi₂O₃/WO₃ hybrid composite exhibited attenuation behavior comparable, and in some regions slightly exceeding, that of the single-oxide systems, indicating that mixed fillers can effectively balance density and shielding efficiency. Oxide addition significantly reduced exposure and energy-absorption buildup factors below 1 MeV, with a moderate increase at higher energies associated with secondary radiation processes. Fast-neutron removal cross sections were also modestly enhanced, with Gd₂O₃-containing composites showing the highest values due to the combined effects of hydrogen moderation and neutron capture. The close agreement between Phy-X/PSD and Geant4 results confirms the reliability of the dual-method approach. Overall, HDPE composites containing about 60 wt.% oxide filler offer a practical compromise between shielding performance, manufacturability, and environmental safety, making them promising candidates for medical, nuclear, and aerospace radiation-protection applications. Full article

Scintillator-SiPM Particle Detectors (SSPDs) are compact, low-power devices with applications including particle physics, underground tomography, cosmic-ray studies, and space instrumentation. They are based on a prism-shaped scintillator with corner-mounted SiPMs. Previous work has demonstrated that analytic algorithms based on a physical model of light propagation can reconstruct particle impinging positions and tracks and estimate deposited energy and Linear Energy Transfer (LET) with moderate accuracy. In this study, we enhance this approach by applying machine learning (ML) methods, specifically gradient boosting techniques, to improve the accuracy of spatial location and energy deposition estimation. Using the GEANT4 simulation toolkit, we simulated cosmic muons and energetic oxygen ions traversing an SSPD, and we trained XGBoost and LightGBM models to predict particle impinging positions and deposited energy. Both algorithms outperformed the analytic baseline. We further investigated hybrid strategies, including hybrid boosting and probing. While hybrid boosting provided no significant improvement, probing yielded measurable gains in both position and LET estimation. These results suggest that ML-driven reconstruction provides a powerful enhancement to SSPD performance. Full article

A Monte Carlo-based model of the CyberKnife M6 6 MV Flattening Filter-Free (FFF) beam was developed to produce the data that can be used to train artificial neural networks. The data include the energy spectra of the beam, its average energy, the spatial distributions of the beam, and the distributions of the photon propagation directions for two selected radiation fields—a large one with a diameter of 60 mm, and a small one with a diameter of 15 mm. The GEANT4 code was used to develop the beam model. The developed model was verified by comparing the depth-dose distributions along the beam axis and the profiles obtained in both simulations and measurements. The data included in this paper, intended for training neural networks, will be made available via Google Drive. Full article

Lead halide perovskites, exemplified by methylammonium (MA) lead iodide (MAPbI₃), combine strong optical absorption, long carrier diffusion lengths, and defect-tolerant electronic structure with facile processing, making them attractive for photovoltaics and radiation detection. Yet, their behavior under electron irradiation remains insufficiently understood, limiting deployment in space and dosimetry contexts. Here, we employ Monte Carlo simulations (Geant4) to model electron interactions with MAPbI₃ across energies from 0.1 to 100 MeV and absorber thicknesses from 10 μm to 1 cm. We quantify deposited energy, event statistics, energy per interaction, non-ionizing energy loss, and dominant radiation effects. The results reveal strong thickness-dependent regimes: thin photovoltaic-type layers (~hundreds of nanometers) are largely transparent to MeV electrons, minimizing bulk damage but allowing localized ionization, exciton self-trapping, and photoexcitation-driven ion migration. Although localized excitations can temporarily improve carrier collection under short-term exposure, their cumulative effect drives ionic rearrangement and defect growth, ultimately reducing device stability. In contrast, thicker detector-type films (10–100 μm) sustain multiple scattering and ionization cascades, enhancing sensitivity but accelerating defect accumulation. At centimeter scales, energy deposition saturates, enabling bulk-like absorption for high-flux dosimetry. Overall, electron irradiation in MAPbI₃ is dominated by electronic excitation rather than ballistic displacements, underscoring the need to optimize thickness and composition to balance efficiency, sensitivity, and durability. Full article

NUSES is a planned space mission aiming to test new observational and technological approaches related to the study of low-energy cosmic rays, gamma rays, and high-energy astrophysical neutrinos. Two scientific payloads will be hosted onboard the NUSES space mission: Terzina and Zirè. Terzina will be an optical telescope readout by SiPM arrays for the detection and study of Cerenkov light emitted by Extensive Air Showers (EASs) generated by high-energy cosmic rays and neutrinos in the atmosphere. Zirè will focus on the detection of protons and electrons up to a few hundred MeV and 0.1–30 MeV photons and will include the Low-Energy Module (LEM). The LEM will be a particle spectrometer devoted to the observation of fluxes of low-energy electrons in the 0.1–7-MeV range and protons in the 3–50 MeV range in low Earth orbit (LEO) followed by the hosting platform. The detection of Particle Bursts (PBs) in this physics channel of interest could provide insights into understanding complex phenomena such as possible correlations between seismic events or volcanic activity with the collective motion of particles in the plasma populating Van Allen belts. With its compact size and limited acceptance, the LEM will allow the exploration of hostile environments such as the South Atlantic Anomaly (SAA) and the inner Van Allen belt, in which the anticipated electron fluxes are on the order of ${10}^6$ to ${10}^7$ electrons per square centimeter per steradian per second. Concerning the vast literature on space-based particle spectrometers, the innovative aspect of the LEM resides in its compactness, within $10\times 10\times 10$ cm³, and in its “active collimation” approach to dealing with the problem of multiple scattering at these low energies. In this work, the geometry of the detector, its detection concept, its operation modes, and the hardware adopted will be presented. Some preliminary results from a Monte Carlo simulation (Geant4) will be shown. Full article

Cherenkov radiation is a widely used detection mechanism in high-energy and astroparticle physics experiments, particularly in water-based detectors operated by leading cosmic-ray observatories. Its popularity stems from its robustness, cost-effectiveness, and high detection efficiency across a broad range of environmental conditions. In this study, we present a detailed Monte Carlo characterization of a Water Cherenkov Detector (WCD) using the Geant4 simulation toolkit as a general, experiment-independent reference for understanding detector responses to secondary cosmic-ray particles. The detector is modeled to register secondary particles produced by the interaction of high-energy cosmic-ray primaries with the Earth’s atmosphere, which give rise to extensive air showers composed of hadronic, electromagnetic, and muonic components capable of reaching ground level. By simulating the differential energy spectra and angular distributions of these particles at the surface, we evaluate the WCD response in terms of energy deposition, Cherenkov photon production, photoelectron generation at the photomultiplier tube, and the resulting charge spectra. The results establish a systematic and transferable baseline for detector performance characterization and particle identification, providing a physically grounded reference that can support calibration, trigger optimization, and analysis efforts across different WCD-based experiments. Full article