Radiation Physics and Engineering

Abstract This work systematically investigates the cluster radioactivity of superheavy parent nuclei ^{267,270,271,272,274}Bh (Z = 107) and ^{268,269,270,271,272}Hs (Z = 108) within a binary decay model. We consider a wide range of emitted clusters, including ⁶He, ¹⁴C, ^18,20O, ²³F, ^22,24,25,26Ne, ^28,29,30Mg, and ^32,34Si, along with their corresponding daughter nuclei. Using the Wentzel-Kramers-Brillouin (WKB) approximation, we compute Q-values, interaction barriers, driving potentials (V - Q), barrier penetrabilities, decay constants λ, and half-lives for all energetically allowed (Q > 0) cluster–daughter combinations. From the full set of possible emissions, we identify the most probable clusters based on the largest Q-values and significant penetrabilities. The resulting half-lives are tabulated and analyzed as a function of parent mass number, revealing systematic trends that underscore the dominant role of nuclear shell effects in determining favored cluster emissions. Our calculations provide a comprehensive data set on the decay properties of superheavy isotopes for Z = 107 and Z = 108 and mass region A = 267-274, offering valuable insights into their stability and the underlying mechanisms of cluster radioactivity.

Abstract The growing demand for lightweight, high-performance shielding in mixed-field radiation environments exposes the critical limitations of traditional heavy materials like ordinary concrete. This study investigates the dual-shielding efficacy of Polyboron, a composite material, demonstrating its capacity to resolve these practical weight-constraint challenges. Utilizing the MATXCOM code and the EPICS2023 photon data library, we evaluate its fundamental radiological parameters including mass attenuation coefficients, buildup factors, and effective atomic numbers (Z_eff) to establish its operational viability. Crucially, this investigation reveals a significant engineering advantage: Polyboron delivers superior fast neutron moderation alongside effective gamma-ray attenuation. Specifically, it provides a 1.8% higher fast neutron removal cross-section (Σ_R of 0.1128 cm^-1 vs. 0.1108 cm^-1) and an approximate 9.2% improvement in mass-specific gamma-ray attenuation (MAC) at 1 MeV compared to ordinary concrete. Remarkably, it achieves this enhanced dual-field shielding while offering a massive 57.8% reduction in physical weight (0.971 g.cm^-3 versus 2.30 g.cm^-3). By matching or exceeding these mass-based protective capabilities of conventional concrete at a fraction of the weight, Polyboron is established as a highly efficient, deployment-ready alternative for weight-sensitive nuclear applications.

Abstract This study investigates the preparation of alpha-emitting sources using the electrodeposition technique for alpha spectrometry. Since source preparation is often costly and may involve the use of enriched radionuclides, highly efficient methods are essential. Among the available techniques, electrodeposition is one of the most widely employed methods for producing alpha sources. In this work, uranium layers were deposited onto stainless steel discs using the electrodeposition method. Key deposition parameters, including anode material (platinum wire with defined geometry), cathode material (polished stainless steel), current density (0.5 A.cm^-2), electrolyte pH (2-2.4), and deposition time (60 minutes), were carefully selected and applied. Following the preparation of the alpha sources, their characterization was performed using alpha spectrometry with a semiconductor detector and Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (SEM-EDS). Alpha spectrometry confirmed the presence of U-238, U-235, and U-234 isotopes, and SEM-EDS analysis was employed to evaluate the uranium distribution on the disc.

Abstract Calcium phosphates are promising candidates for thermoluminescent dosimetry due to their capacity to host dopants that enhance the thermoluminescent (TL) response, their similarity to bone mineral composition, favorable synthesis conditions, and the flexibility of available synthesis methods. Optimizing the TL response of these materials is a central objective in thermoluminescence research. In this study, hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP) were synthesized via a solid-state method and doped with cerium (Ce), lanthanum (La), gadolinium (Gd), and dysprosium (Dy) at molar concentrations of 1%, 2%, and 3%. The samples were irradiated over a dose range of 20-1500 Gy, relevant for industrial and agricultural applications, and evaluated in terms of sensitivity, linear dose-response range, and glow-curve characteristics. The results indicate that β-TCP generally exhibits superior TL response compared to HAP. Notably, HAP doped with 2% Ce and β-TCP doped with 1% and 3% Dy were identified as optimal compositions. Lanthanum and gadolinium doping had minimal impact on the TL properties of HAP. Overall, while HAP provides a favorable structural framework for dopant incorporation, the highest-performing samples were observed in the β-TCP series.

Abstract Dynamic contrast-enhanced MRI (DCE-MRI) plays a pivotal role in quantifying tissue hemodynamics, yet accurate pharmacokinetic (PK) parameter estimation remains challenging. We present PKest-LSnet, a novel Long Short-Term Memory (LSTM)-based deep learning framework for robust PK analysis. The network was trained on comprehensive simulated data generated using physiologically plausible ranges of PK parameters (parameetrs of Tofts equation: vp, Ktrans, kep) and a population-based arterial input function (AIF), enabling precise ground-truth validation. Rigorous testing on clinical data from 19 glioblastoma patients demonstrated strong agreement with reference method maximum likelihood estimation (MPE <12% for all parameters), with 99.42% accuracy in classifying tumor signals. The model maintained stability across variable acquisition protocols (time intervals: 2-6 sec; SNR: 5–100), proving its adaptability to real-world clinical variability. While excelling in tumor characterization (DSC=77.27%), leaky vasculature classification challenges (DSC=36.76%) revealed opportunities for architectural refinements. PKest-LSnet eliminates dependency on initial parameter estimates, reduces computational time by orders of magnitude compared to conventional methods, and offers a robustness method to the tested variations in temporal sampling intervals and SNRs-critical for multicenter studies. This work bridges the gap between simulated training and clinical deployment, providing a validated tool for precision DCE-MRI analysis with direct applications in oncology and therapeutic monitoring. Future directions include hybrid architectures for improved intermediate-tissue classification and patient-specific AIF integration.

Abstract Neutron radiography is a non-destructive imaging technique used to study the internal structures of materials. In this work, a computational investigation was conducted to evaluate the effect of sample thickness on neutron radiography of polyethylene- and aluminum-based specimens using emulsion films. The MCNPX 2.7.0 code was employed to simulate the imaging geometry, including the sample, gadolinium converter, and emulsion film, for both polychromatic and monochromatic neutron beams. Sample thicknesses of 2, 4, and 6 cm were analyzed, and the contributions of neutrons and gamma rays to image formation were quantified through (n, γ) reaction rates and gamma deposited energy in the emulsion layer. Results show that increasing sample thickness reduces image quality, particularly for polyethylene due to its high thermal neutron scattering. Gamma-ray energy deposition was found to contribute to film exposure, particularly for thicker specimens, indicating that gamma radiation should be considered when interpreting emulsion-film neutron radiographs. The computational investigations showed that there are noticeable differences between the specimens' images formed by monochromatic and polychromatic neutron beams. These findings provide insights for optimizing imaging conditions, and detector selection in neutron radiography studies.

Abstract This study aimed to optimize the collimator length for a parallel-hole prompt gamma camera dedicated to real-time proton beam range verification, achieving an optimal balance between detection sensitivity and spatial accuracy for clinical application. Comprehensive Monte Carlo simulations were conducted using the GATE platform with the QGSP_BIC_HP_EMZ physics list. A cylindrical PMMA phantom was irradiated with a 90 MeV monoenergetic proton beam, and a PG camera model consisting of an LSO scintillator coupled with a lead parallel-hole collimator was simulated. Collimator length was systematically varied from 4 to 8 cm, and detected PG events were analyzed within a 4.2-6.3 MeV energy window. System performance was evaluated using sensitivity (total detected counts) and spatial accuracy (Δ), defined as the absolute difference between true and reconstructed depth of maximum PG emission. The simulated energy spectrum exhibited characteristic photopeaks from carbon and oxygen, and a strong spatial correlation was confirmed between the distal edge of the Bragg peak and the PG emission maximum. Increasing collimator length decreased sensitivity but generally improved spatial accuracy. The optimal trade-off was achieved with a 7 cm collimator, yielding the best spatial accuracy of Δ = 2 mm. This study identifies 7 cm as the optimal collimator length for a parallel-hole PG camera, achieving spatial accuracy comparable to more complex slit- or pinhole-based systems. The findings provide a quantitative design framework and underscore the critical importance of balancing geometric resolution with sufficient count statistics for precise and timely clinical range verification.

Abstract Neutron radiography is a powerful nondestructive imaging technique widely used at research reactors for industrial and scientific applications. In this study, image formation in neutron radiography was investigated using both computational and experimental approaches. The MCNPX Monte Carlo code was employed to simulate image formation in the film emulsion layer for polyethylene (PE) and aluminum (Al) samples irradiated by the neutron beam of the Tehran Research Reactor (TRR). The samples contained 1-mm-diameter holes filled with air, iron, copper, tin, and lead to evaluate image contrast and spatial resolution. The results show that the sample-converter-film configuration provides superior image quality for the investigated samples. Moreover, the spatial distribution of the (n, γ) reaction rate in the gadolinium converter accurately predicts the radiographic image produced by transmitted neutrons before experimental irradiation. Experimental measurements indicate that the MX125 radiographic film provides higher image contrast and spatial resolution for the investigated polyethylene sample than the CCD-based digital imaging system, whereas the latter significantly reduces imaging time and enables digital image processing and three-dimensional reconstruction. In the case of Aluminum sample, the CCD imaging performance is better regarding CNR parameter.