Although low in fluence, high-LET secondary ions and nuclear fragments within spacecraft contribute non-negligibly to astronaut radiation exposure. CR-39 is used for personal dosimetry in space, where a calibrated relationship between the etch-rate ratio V and LET enables particle LET inference and subsequent dose assessment. For low-energy Li, B, and C ions, however, experimental data show that the local etch response is not uniquely determined by REL350 alone and can vary systematically with track position. Discrete beam data cannot cover the continuous energy and incidence-angle ranges encountered in space, while existing simulations mainly address alpha particles and protons. This study developed an experimentally constrained forward-simulation framework for low-energy light-ion tracks in CR-39. The framework takes particle species, initial energy, incidence angle, and removed-layer thickness as inputs. Geant4 calculates the depth-resolved restricted energy loss REL350(x) with a 350 eV cutoff. REL350(x) is coupled with the experimentally derived position-dependent response V(REL350, x) to obtain V(x), which drives a track-evolution model predicting surface-opening dimensions, track depth, and 2D/3D morphology. The framework was evaluated for Li ions against published data and extended to B and C ions. The model reproduced the surface-opening dimensions and main morphological features of Li tracks, while predicted track-depth trends agreed with experiments. The B- and C-ion results showed that the workflow can be extended across species, although quantitative accuracy requires further experimental validation. The framework establishes a forward-response basis for future track interpretation and LET analysis. Whether the framework can quantitatively improve LET-spectrum reconstruction or dose assessment remains to be demonstrated.
Background Robust dosimetric validation is essential for using any new radiation device for clinical purposes. Monte Carlo (MC) simulation techniques have emerged as a powerful tool for dosimetric validation. Recently, ophthalmic plaques embedded with Ruthenium-106 (Ru-106), developed by Bhabha Atomic Research Centre (BARC), Mumbai, India, have been made commercially available for manual brachytherapy. Therefore, dosimetric validation of the plaques at users’ end is needed for safe and optimal clinical application. Purpose For the first time, the BARC-make Ru-106 notched eye plaque was simulated with the MC technique in this study. The 3D dosimetry results obtained with the MC simulations were validated with film dosimetry and with the data provided by the manufacturer. Methods EGS_Brachy MC code and EBT3 radiochromic film were chosen to determine absolute dose, 2D and 3D dose distributions for the eye plaque. A customised water phantom was designed and fabricated in-house for film dosimetry. Results The MC simulation results were consistent with film dosimetry and with the manufacturer's stated values for absolute dose rate (at a clinical depth of 2.0 mm) and percentage depth dose (PDD), showing a deviation of less than 5.0%. The statistical uncertainty in the MC simulations was 0.2% for the dose calculated at a depth of 2.0 mm. Conclusion The 3D dosimetry of BARC-make Ru-106 notched eye plaque was performed using the EGS_Brachy MC code for the first time and validated with film measurements. Thus, it is believed that based on the technical details provided by the manufacturer (BARC), the eye plaques could be reliably simulated for clinical dosimetric planning purposes.
Single-crystal-derived CsPbBr3/PMMA composite scintillating films were developed for alpha-particle radiation detection. Bulk CsPbBr3 single crystals were mechanically milled into micrometer-scale particles with an average size of 1.42±0.41μm and embedded in a poly(methyl methacrylate) (PMMA) matrix by solution casting, providing a scalable route to flexible composite scintillators. This approach enabled the dispersion of single-crystal-derived particles in the polymer matrix while retaining their microsecond-scale photoluminescence characteristics. The optimized film exhibited an amplitude-weighted average photoluminescence lifetime of approximately 1.1μs, indicating that the dominant microsecond-scale photoluminescence dynamics of the single-crystal-derived CsPbBr3 particles were largely preserved after PMMA embedding. The scintillation response was evaluated with alpha-particle excitation from a 241Am source with a nominal alpha energy of 5.486 MeV. By varying the film thickness between approximately 165 and 343μm and the CsPbBr3 loading from 0.5 to 1 wt%, well-resolved alpha-particle pulse-height spectra were obtained. The optimized film, with a CsPbBr3 loading of 0.5 wt% and a thickness of approximately 165μm, achieved an energy resolution (ER) of 14.6% at the nominal alpha energy of 5.486 MeV. A semi-quantitative CsI(Tl)-referenced estimate gave an alpha-excited photon output of approximately 5.1×103 photons/5.486 MeV-α for the optimized film. The same film exhibited an effective scintillation decay time of approximately 85 ns, indicating a fast temporal response. After 15 days of continuous alpha-particle irradiation under ambient conditions, the ER increased from 14.6% to 17.4%, indicating measurable but limited degradation in pulse-height spectral resolution. These results demonstrate a single-crystal-derived particle-to-polymer composite route and clarify the loading- and thickness-dependent factors governing alpha-particle pulse-height resolution in CsPbBr3/PMMA scintillating films.
Indoor radon is an important environmental health concern because long-term exposure increases the risk of lung cancer. The volumetric radon entry rate (VRER) and air exchange rate (AER) are two key parameters controlling indoor radon accumulation and ventilation-related radon removal. In this study, a dynamic radon accumulation model was experimentally tested to simultaneously determine VRER and AER by fitting indoor radon concentration growth curves. The method was validated in a closed room under two experimental scenarios: with and without a standard radon source. Indoor radon concentration was continuously monitored, and the least-squares method was used for curve fitting and parameter inversion. For the test experiment with the standard radon source, the relative differences between the fitted radon entry rate and the combined radon input from the standard source and the building-envelope contribution were below 9%. The AER values obtained from the model agreed with those measured using the CO2 tracer method within the experimental uncertainties, with relative differences of up to approximately 13%. In the test experiment without an external radon source, the VRER determined by the method and that calculated from the radon exhalation rate (RER) of the building envelopes agreed well within the estimated uncertainties. These results preliminarily demonstrate that the dynamic radon accumulation model is feasible for the simultaneous determination of VRER and AER under the tested closed-room conditions, and may provide a useful approach for indoor radon assessment and ventilation optimization.
A portable beta-gamma phoswich detector utilizing GAGG(Ce) and BC-404 plastic scintillators was developed to support the medical screening of workers and evacuees — including skin and thyroid monitoring — during nuclear and radiological emergencies. During such emergencies, the protective measures taken against individuals are largely contingent upon the results of radiation monitoring, and the International Atomic Energy Agency has established guidelines for the formulation and implementation of Operational Intervention Levels (OILs) pertinent to these emergencies, thereby facilitating prompt responses grounded in quantifiable and easily interpretable data. This study focused on the development of a detection system designed to support OIL-based medical screening during such emergencies. To enhance the efficacy of the phoswich detector, the optimal thickness of the BC-404 plastic scintillator was determined to be 3 mm through Geant4 Monte Carlo simulations, maximizing the beta-ray response while suppressing the gamma-ray response. The feasibility of the detector was verified through measurements employing point sources and BC-404 scintillators of varying thicknesses, which showed intrinsic detection efficiencies in good agreement with the simulation results (relative differences of 1%–9%). Pulse shape discrimination was employed to differentiate signals from the two scintillators, and the figure of merit was assessed to be 1.83, confirming adequate signal separation. The monitoring capabilities of this single detector are expected to be practical across diverse emergency conditions, providing a basis for its application to medical screening tasks, such as skin and thyroid monitoring.
