Continuous Slowing Down Approximation Research Articles

Lithium inelastic cross-sections and their impact on micro and nano dosimetry of boron neutron capture

Objective. To present a new set of lithium-ion cross-sections for (i) ionization and excitation processes down to 700 eV, and (ii) charge-exchange processes down to 1 keV u−1. To evaluate the impact of the use of these cross-sections on micro a nano dosimetric quantities in the context of boron neutron capture (BNC) applications/techniques. Approach. The Classical Trajectory Monte Carlo method was used to calculate Li ion charge-exchange cross sections in the energy range of 1 keV u−1 to 10 MeV u−1. Partial Li ion charge states ionization and excitation cross-sections were calculated using a detailed charge screening factor. The cross-sections were implemented in Geant4-DNA v10.07 and simulations and verified using TOPAS-nBio by calculating stopping power and continuous slowing down approximation (CSDA) range against data from ICRU and SRIM. Further microdosimetric and nanodosimetric calculations were performed to quantify differences against other simulation approaches for low energy Li ions. These calculations were: lineal energy spectra (yf(y) and yd(y)), frequency mean lineal energy yF― , dose mean lineal energy yD― and ionization cluster size distribution analysis. Microdosimetric calculations were compared against a previous MC study that neglected charge-exchange and excitation processes. Nanodosimetric results were compared against pure ionization scaled cross-sections calculations. Main results. Calculated stopping power differences between ICRU and Geant4-DNA decreased from 33.78% to 6.9%. The CSDA range difference decreased from 621% to 34% when compared against SRIM calculations. Geant4-DNA/TOPAS calculated dose mean lineal energy differed by 128% from the previous Monte Carlo. Ionization cluster size frequency distributions for Li ions differed by 76%–344.11% for 21 keV and 2 MeV respectively. With a decrease in the N 1 within 9% at 10 keV and agreeing after the 100 keV. With the new set of cross-sections being able to better simulate low energy behaviors of Li ions. Significance. This work shows an increase in detail gained from the use of a more complete set of low energy cross-sections which include charge exchange processes. Significant differences to previous simulation results were found at the microdosimetric and nanodosimetric scales that suggest that Li ions cause less ionizations per path length traveled but with more energy deposits. Microdosimetry results suggest that the BNC’s contribution to cellular death may be mainly due to alpha particle production when boron-based drugs are distributed in the cellular membrane and beyond and by Li when it is at the cell cytoplasm regions.

Evaluation of shielding and interaction properties of different stainless steel alloys for nuclear power plant shielding

This study evaluated the gamma and neutron-shielding parameters, electron and charge particles’ interaction properties of three different stainless steel-based alloys (2507SS, 304SS and AISI1018) with densities of 7.82, 7.81 and 7.82, respectively for deployment in nuclear reactor construction. Gamma shielding parameters were evaluated with Phy-X/PSD, Py-MLBUF and GRASP computer programs within the energy range of 0.2 MeV to 15 MeV. The relative deviations (RD %) between two of these computational platforms were calculated. Fast Neutrons Effective Removal Cross-Sections (FNRCS) and Macroscopic Removal cross-section (MRCS) values for fast neutrons were calculated with Phy-X/PSD and MRCS software, while thermal/fast neutron attenuation factors were calculated with NGCals software. The continuous-slowing-down approximation (CSDA) range and total stopping power (TSP) values of H+ and He++ ions were estimated with SRIM Monte Carlo code in a wide energy range of 1–20 MeV. The projectile range of electrons was computed with ESTAR NIST software within the kinetic energy of 0.01–1000 MeV. Gamma-ray, thermal neutron and fast neutron transmission factors (TFs) values were calculated for all samples for a range of well-known energies. From the obtained results, all evaluated parameters were dependent on the composition of shielding materials, the type of radiation and the photon energy of the radiation. The maximum MAC values obtained from the three alloy samples are 0.1505 cm2/g for 2507SS, 0.1453 cm2/g for 304SS and 0.1459 cm2/g for AISI1018 at 0.02 MeV. These results projected 2507SS as a better shielding alloy when compared with other investigated alloy samples. Considering the closeness of densities of investigated alloy samples the shielding and interaction properties of all alloy samples gave excellent and similar results implying that all investigated alloys will effectively serve as a radiation-shielding material in a nuclear reactor.

Validation of the single-event method for low-energy electron transport via stopping power calculations with MCNP

Monte Carlo simulations of low-energy (<50 keV) electron transport in matter are essential for a broad range of application fields. Several Monte Carlo codes have developed specialized treatments for this case, but a comprehensive validation of low-energy electron transport for general-purpose simulations remains lacking in the literature. One approach to accomplish this validation is calculation of stopping power using low-energy electron transport physics, as stopping power is a fundamental radiation transport quantity which must be simulated accurately for nearly any application. In this work, we use the Monte Carlo N-Particle (MCNP) radiation transport code with the single-event method for electron transport to calculate stopping powers of low-energy electrons (50 eV to 30 keV) in 41 elemental solids, 14 compound solids, and five rare gas solids, comparing simulation results to published semi-empirical stopping power calculations from optical measurements. In general, the simulations give good agreement (typically within ±10%) with semi-empirical stopping power values at higher energies: 300 eV and above for most elemental solids, 1 keV and above for compound solids, and 400 eV and above for rare gas solids. Agreement between MCNP and semi-empirical values is worse below these energies. The most significant source of error is the EPRDATA14 cross section data, which does not account for changes in electronic structure due to solid-state bonding, particularly in compound materials. The simplistic model of atomic excitation used to generate the EPRDATA14 cross sections is another key source of error. Additionally, the breakdown of the continuous slowing-down approximation introduces significant uncertainty at low energies, although this is a limitation of the calculation method and not of the simulation procedure. Accounting for these and other uncertainty sources, the single event method in MCNP is robust and able to give good accuracy for a variety of low-energy electron transport problems through diverse kinds of materials.

A GPU-based fast Monte Carlo code that supports proton transport in magnetic field for radiation therapy.

This paper presents the effort to extend a previously reported code ARCHER, a GPU-based Monte Carlo (MC) code for coupled photon and electron transport, into protons including the consideration of magnetic fields. The proton transport is modeled using a Class-II condensed-history algorithm with continuous slowing-down approximation. The model includes ionization, multiple scattering, energy straggling, elastic and inelastic nuclear interactions, as well as deflection due to the Lorentz force in magnetic fields. An additional direction change is added for protons at the end of each step in the presence of the magnetic field. Secondary charge particles, except for protons, are terminated depositing kinetic energies locally, whereas secondary neutral particles are ignored. Each proton is transported step by step until its energy drops to below 0.5 MeV or when the proton leaves the phantom. The code is implemented using the compute unified device architecture (CUDA) platform for optimized GPU thread-level parallelism and efficiency. The code is validated by comparing it against TOPAS. Comparisons of dose distributions between our code and TOPAS for several exposure scenarios, ranging from single square beams in water to patient plan with magnetic fields, show good agreement. The 3D-gamma pass rate with a 2mm/2% criterion in the region with dose greater than 10% of the maximum dose is computed to be over 99% for all tested cases. Using a single NVIDIA TITAN V GPU card, the computational time of ARCHER is found to range from 0.82 to 4.54 seconds for 1×107 proton histories. Compared to a few hours running on TOPAS, this speed improvement is significant. This work presents, for the first time, the performance of a GPU-based MC code to simulate proton transportation magnetic fields, demonstrating the feasibility of accurate and efficient dose calculations in potential magnetic resonance imaging (MRI)-guided proton therapy.

Monte Carlo simulations for targeted beta therapy: An optimization for liver lesions and comparison of dose distributions in other organs

ObjectiveTo optimize targeted beta therapy for liver lesions in adult male phantom by comparing the efficacy and safety profiles of five different beta-emitting radionuclides: 90Y, 166Ho, 153Sm, 47Sc, and 177Lu. MethodsThis study includes Monte Carlo simulations of the behavioral characteristics of five different beta emitters that have current or potential use in targeted beta therapy. The energy loss of beta particles moving within the material through ionization or chemical processes, the energy transferred to the material, the energy lost by beta particles along the distance traveled within the tissue, and consequently, the stopping power are calculated using the Bethe-Bloch formula. The CSDA (continuous slowing-down approximation) range of beta particles within the tissue is examined using ESTAR and GEANT codes, while the stopping power of the tissue is investigated using FLUKA, ESTAR, and GEANT codes. Tissue dose calculations for the target organ are obtained using the IDAC-Dose2.1 and MIRDcalc simulation programs, using parameters such as absorbed dose per accumulated activity (S-factor) and specific absorbed fraction (SAF). Additionally, dose and flux values are obtained using the PHITS program. ResultsThe behaviors and dose contribution of beta particles in liver tissue have been addressed in various ways. 90Y, which has the highest average beta energy, was observed to provide a higher absorbed dose value in the liver compared to other beta-emitting isotopes, while the lowest absorbed dose was observed with 177Lu. In other organs, it has been observed that 90Y and 47Sc contribute to a higher absorbed dose compared to other beta-emitting isotopes. ConclusionsThis study emphasizes the complexity and significance of targeted beta therapy optimization.

Electron beam impact parameters for the creation of excited species in N2 gas

The number of electron–ion pairs and the distribution of excited species created by the passage of an intense electron beam in a gas are important parameters for many applications. The previously published values for molecular nitrogen rely on a differential ionization cross section that uses a number of fitting parameters and excitation cross sections determined from analytical fitting functions [S. P. Slinker, A. W. Ali, and R. D. Taylor, J. Appl. Phys. 67, 679 (1990)]. Slinker used cross section fits to solve the Boltzmann equation which was then used to compute the important beam-impact parameters. In this work, it is shown that an alternative approach based on the continuous slowing down approximation (CSDA) can be used to compute the energy expended per electron-ion pair and the distribution of excited gas species. This method results in an integral equation that can be solved iteratively and converges rapidly. The binary-encounter Bethe (BEB) differential ionization cross section is used [Y. K. Kim and M. E. Rudd, Phys. Rev. A 50, 3954 (1994); W. Hwang, Y.-K. Kim and M. E. Rudd, J. Chem. Phys. 104, 2956 (1996)]. The BEB model naturally extends to relativistic energies and has no free parameters. This makes the BEB considerably easier to use than previous models based on fitting parameters. The BEB model requires orbital constants obtained from quantum chemistry calculations. To demonstrate the technique, the electron-beam impact parameters are computed for nitrogen gas. The tabulated low-energy excitation cross sections are extended to relativistic energies using Bethe's asymptotic value for the inelastic cross sections [M. Inokuti, Rev. Mod. Phys. 43, 297 (1971)]. It is shown that the results for the energy expended per electron–ion pair as well as the distribution of excited states agree with published experimental values and are similar to previously published theoretical results.

Mass stopping power and nuclear shielding behavior of lead borate glasses: Influence of gamma irradiation on physical properties

Four glassy systems with dissimilar PbO ratios were synthesized by the melting method. Raman scattering was used to study the chemical bonds inside the glass structures and follow the chemical changes occurring inside their networks after using the glasses in a radiation field. The glass samples are based on several tetrahedral and triangular groups where in BO3 is predominant. The energy gap of each sample was calculated from two different equations extracted from absorption and transmission measurements as ETauc and ETrans, respectively. Also, chemical durability has been studied to show the stability of these glasses against acidic environmental effect and followed by SEM images. Our findings showed that radiation effect on the prepared samples did not cause significant variations of structural and optical characteristics, however, increasing PbO concentrations resulting in enhancement of several radiation attenuation competencies. This study presented a comprehensive study of the radiation shielding properties of lead borate glass by assessing the effectiveness of proton, electron, neutron, and gamma shielding. Mass stopping power (ψp) and projected range (PR) values were calculated for proton particles (H1) using SRIM Monte Carlo simulation code and its subroutine TRIM, which predicts the radiation damage and atomic displacements per atom (dpa), while the ESTAR program was used to calculate ψe and the continuous slowing down approximation (CSDA) range for electrons. Furthermore; the findings estimate the excess lifetime cancer risk% for radiation workers behind the glass shields. Also, the glass with the lowest PbO content has the highest ΣR value, whereas the sample with the highest PbO content has the highest MAC value of gamma rays.

A Comparative Study on the Radiation Attenuation Properties of Iron and Stony Meteorites: A Case of Mundrabilla and NWA 7629 Meteorites

The goal of this paper is to compare and investigate the radiation attenuation properties of Mundrabilla and NWA 7629 meteorites in terms of the photon, fast neutron and charged particles. The linear attenuation coefficients of Mundrabilla are higher than those of NWA 7629. The half value layers, tenth value layers and mean free paths of NWA 7629 are greater than those of Mundrabilla. The effective atomic number, effective electron density, equivalent atomic number and effective conductivity of the Mundrabilla are nearly constant between 0.015 MeV–15 MeV. Both the exposure build-up factors and energy absorption build-up factors are maximum at 0.8 MeV for Mundrabilla and NWA 7629. The projected/ continuous-slowing-down approximation (CSDA) ranges for charged particles for NWA 7629 are higher than those of Mundrabilla. The fast neutron attenuation of Mundrabilla is better than those of NWA 7629. Consequently, it can be concluded that photon, fast neutron and charged particles attenuation capability of Mundrabilla are better than NWA 7629 due to the nickel content, higher density and higher content of iron.

A Comparative Study on the Radiation Attenuation Properties of Iron and Stony Meteorites: A Case of Mundrabilla and NWA 7629 Meteorites

The goal of this paper is to compare and investigate the radiation attenuation properties of Mundrabilla and NWA 7629 meteorites in terms of the photon, fast neutron and charged particles. The linear attenuation coefficients of Mundrabilla are higher than those of NWA 7629. The half value layers, tenth value layers and mean free paths of NWA 7629 are greater than those of Mundrabilla. The effective atomic number, effective electron density, equivalent atomic number and effective conductivity of the Mundrabilla are nearly constant between 0.015 MeV–15 MeV. Both the exposure build-up factors and energy absorption build-up factors are maximum at 0.8 MeV for Mundrabilla and NWA 7629. The projected/ continuous-slowing-down approximation (CSDA) ranges for charged particles for NWA 7629 are higher than those of Mundrabilla. The fast neutron attenuation of Mundrabilla is better than those of NWA 7629. Consequently, it can be concluded that photon, fast neutron and charged particles attenuation capability of Mundrabilla are better than NWA 7629 due to the nickel content, higher density and higher content of iron.

Positron CSDA range and stopping power calculations in some human body tissues by using Lenz Jensen atomic screening function

In this study, for some human body tissues, positron stopping power (SP) values were presented, being valid for low and intermediate positron energies. In addition, calculation of the continuous slowing down approximation (CSDA) range from the stopping power is also made. Calculation of the CSDA range for some human body tissues: adipose tissue, skeletal muscle, skin, and soft tissue have been introduced for incident positron in the energy range 20 eV to 10 MeV. The range of positron has been calculated within the continuous slowing down approximation using modified Rohrlich and Carlson formula of stopping power.The calculated results of the SP and CSDA range values for positrons in some materials, such as adipose tissue, skeletal muscle, skin, and soft tissue in the energy range from 20 eV to 100 MeV are found to be in good agreement to with the Penelop 2014 code results above 0.4 keV energies. It makes more meaningful results than penelope 2014 for under 0.4 kev energies.In this work, a model is suggested for the calculation of SP and CSDA ranges for incident positrons on some human body tissues. Simple analytical expressions for the effective number of positrons and effective mean excitation energy (EMEE) and the positron SP have been derived which are suitable for intermediate energies. The results from this study of stopping powers of some humanbody tissues for especially low energy positrons should be useful in PET, diagnostics, and therapy with nuclear radiation.

Modelling energy deposition in polymethyl methacrylate with low-energy electron irradiation

Energy deposition in dielectric materials by electron irradiation is important in evaluating irradiation effects in various applications. Herein, we developed a novel Monte Carlo model to calculate the actual distribution of energy deposition in polymethyl methacrylate (PMMA) by simulating low-energy electron transport, including secondary electron cascades. We compared the energy deposition calculated using this model with the distribution of energy loss based on the continuous slowing down approximation (CSDA). The difference in depth distribution between energy deposition and energy loss near the surface is attributed to the secondary electron emission. The characteristics of energy deposition distributions at various incident angles and primary energy were analysed. Energy depositions based on different energy loss mechanisms were classified. Approximately half of the total energy deposition was formed in paths of the secondary cascade at keV-electron irradiation. The temporal properties of energy deposition show that the fast process of energy deposition occurs first near the surface of the dielectric material, then deep inside and 1-keV electrons deposit their energy in 10−14 s.

Atmospheric Electron Spatial Range Extended by Thundercloud Electric Field Below the Relativistic Runaway Electron Avalanche Threshold

AbstractCosmic‐ray shower, hitting the atmosphere all the time, includes high‐energy electrons. Electric fields in thunderstorms accelerate these electrons so that they can reach farther distances with producing secondary electrons. The strong field above 0.284 MV m−1 causes the Relativistic Runaway Electron Avalanches (RREA) process with an exponential increase of electrons. Even with lower electric fields below this RREA threshold which are usually measured in thunderstorms, an increase in electrons' kinetic energy and production of secondary electrons can occur without avalanche processes, known as Modification Of Spectra (MOS) of the cosmic‐ray shower. Both phenomena are related to observed gamma ray glow, which is bremsstrahlung emission from accelerated electrons in thunderstorms. We calculate an extended range and kinetic energy of electrons below the RREA threshold using an analytical evaluation and Geant4 Monte Carlo simulations. For example, at 0.280 MV m−1 slightly below the RREA threshold, 3 MeV electrons gain 100% of their original kinetic energy through the passage of the continuous slowing down approximation (CSDA) range defined at the null electric field, which is consistent with results in previous studies as the transition to the RREA process. Even at a lower field of 0.260 MV m−1, the energy recovery by the field allows an injected 20 MeV electron beam to extend its average electron range from 73 m, in the null field configuration, to 562 m. We have performed analytical calculation and Geant4 simulations of atmospheric electron behavior for initial electron energy of 0.1–100 MeV and an electric field below 0.290 MV m−1.

Stopping power and CSDA range calculations of electrons and positrons over the 20 eV–1 GeV energy range in some water equivalent polymer gel dosimeters

In this study, the stopping power, CSDA range and radiation yield calculations of electrons and positrons over the 20 eV–1 GeV energy range in some water equivalent polymer gel dosimeters were performed. For collision stopping power calculations of electrons and positrons the effective charge concept proposed by Sugiyama were considered. Here, both the effective charge of incident electrons and positrons (z*) and the effective charge (Z*) and the effective mean excitation energy (I*) of the target material were calculated. For the density effect correction the Fano model was selected. For the radiative stopping power analytical model based on the ratio between the collision and the radiative stopping power discribed by Attix was considered. For CSDA range and radition yield the continuous slowing down approximation (CSDA) was considered and the calculations were performed using numerical integral methods. Because of their water equivalent and 3D dose distribution properties, MAGIC and MAGAS polymer gels were selected as a target materials. The calculations were performed by programming all the equations discribed in this study as a computational code. The results of the stopping power, range and radiation yield were compared with those of ESTAR program and PENELOPE Monte Carlo modelling. Some deviations in low and high energy region between the calculated and reference data were observed. However, the similarity between calculated and reference data is remarkable. For the collision stopping power and CSDA range a good agreement between the calculated and reference data was observed for energies >1 keV. Whereas, for the radiative stopping power a good agreement was observed for energies >100 keV.

Analysis of physical and mechanical traits and nuclear radiation transmission aspects of Gallium(III) trioxide constituting Bi2O3-B2O3 glasses

For five Ga2O3-Bi2O3-B2O3 composition glasses for improved Bi2O3 content at 25 to 65 mol% (10% continuously each time) at a fixed 10 mol% Ga2O3 amount, distinct physical and mechanical aspects and nuclear radiation attenuation factors were investigated. Increased Λ (optical basicity) values with a gradual Bi2O3 addition indicate studied samples’ improving basic character. Applying BC (bond compression) model key mechanical traits such as Ybc (Young’s modulus), Kbc (bulk modulus), S (shear modulus), L (longitudinal modulus), and σ (Poisson’s ratio) are evaluated where in all glasses 10Ga2O3-65Bi2O3-25B2O3 (mol%) sample exhibits superior elastic moduli. Enhanced Bi2O3 causes for compactness of the gallium borate network as ǹc (average cross-link density) improves from 2.3 to 3.4 indicating increased rigidity of glasses. Later, PHITS, FLUKA, and MCNPX codes are wielded to derive μ/ρ (mass attenuation coefficient) of all selected samples for photons having energy ranging from 15 KeV to 15 MeV. Simulated μ/ρ quantities exactitude is tested via Phy-X/PSD and WinXCOM programs’ μ/ρ results and identified a fairly good harmony among them. With photon energy, MFP (mean free path), TVL (tenth-value layer), and HVL (half-value layer) values variations show a similar tendency and against the trend which noticed for μ/ρ and μ (linear attenuation coefficient) values. 10Ga2O3-65Bi2O3-25B2O3 (mol%) sample’s MFP and HVL are correlated with five commercial γ-ray glass shields’ respective values at 1.25 MeV, 0.662 MeV (137Cs), and 0.2 MeV energies. Further, Zeq (equivalent atomic number) and using G–P (geometric progression) fitting approach for ten individual PDs (penetration depths) within 1–40 mfp range at 15 – 15 × 103 KeV energy region BUFs (buildup factors) were estimated. Attained RPE (radiation protection efficiency) findings attest all chosen Ga2O3-Bi2O3-B2O3 glasses’ competent absorption capacity for lower energy photons. Next, α-particles and protons MSPs (mass stopping powers), i.e. ΨA and ΨP and PRs (projected ranges), i.e. ΦA and ΦP by utilizing SRIM code as well as for electrons MSPs (ΨE) and CSDA (continuous slowing‐down approximation) ranges by ESTAR database have been calculated within 15–15 × 103 KeV KE (kinetic energy) range. Also, ΣR (fast neutron removal cross-section) and for 0.253 × 10–4 KeV energy neutrons σT (total cross-section) and SP (shielding percentage) values were approximated. With Bi2O3 addition, realized ΣR is changed at 0.1161–0.1213 cm−1 extent. For thermal neutrons absorption, 10Ga2O3-25Bi2O3-65B2O3 (mol%) glass shows larger σT (=17.534 cm−1) and at any considered thickness higher SP whereas 10Ga2O3-65Bi2O3-25B2O3 (mol%) (lead-free) glass has better attenuating features for photons affirming the incorporated Bi2O3 favorable effect.

Continuous slowing-down approximation ranges of biological materials for 0.05–10 MeV alpha particles by using different approach methods

The goal of this study was to calculate the range values of alpha particles in bone, MS20 tissue substitute, and muscle targets using different approach methods. The range values were calculated using Gauss quadrature, Simpson 1/3, and trapezoidal numerical integration methods in continuous slowing-down approximation (CSDA). Overall, the Gauss quadrature method gave the best CSDA range values for the target materials. These results will be conducive to studies involving the interaction of radiation with biological materials.

A Novel Reconstruction Method to Increase Spatial Resolution in Electron Probe Microanalysis

The spatial resolution of electron probe microanalysis (EPMA), a non-destructive method to determine the chemical composition of materials, is currently restricted to a pixel size larger than the volume of interaction between beam electrons and the material, as a result of limitations on the underlying k-ratio model. Using more sophisticated models to predict k-ratios while solving the inverse problem of reconstruction offers a possibility to increase the spatial resolution. Here, a k-ratio model based on the deterministic M1-model in Boltzmann Continuous Slowing-Down approximation (BCSD) will be utilized to present a reconstruction method for EPMA which is implemented as a PDE-constrained optimization problem. Iterative gradient-based optimization techniques are used in combination with the adjoint state method to calculate the gradient in order to solve the optimization problem efficiently. The accuracy of the spatial resolution still depends on the number and quality of the measured data, but in contrast to conventional reconstruction methods, an overlapping of the interaction volumes of different measurements is permissible without ambiguous solutions. The combination of k-ratios measured with various electron beam configurations is necessary for a high resolution. Attempts to reconstruct materials with synthetic data show challenges that occur with small reconstruction pixels, but also indicate the potential to improve the spatial resolution in EPMA using the presented method.

Probing of nuclear radiation attenuation and mechanical features for lithium bismuth borate glasses with improving Bi2O3 content for B2O3 + Li2O amounts

Against photon energies extending from 0.015 to 15 MeV, MCNPX, FLUKA and PHITS codes are operated to simulate mass attenuation coefficients (μ/ρ) for a total of ten B2O3-Bi2O3-Li2O glass compositions with added Bi2O3 amount from 10 to 55 mol% (5 mol% growth gradually) as a substitute for total (B2O3 + Li2O) mol% content. All the computed μ/ρ values correctness is examined by Py-MLBUF and WinXCOM programs’ μ/ρ outcomes and we found a good agreement among them. 55Bi2O3-35B2O3-10Li2O (mol%) glass half-value layer (HVL) and mean free path (MFP) quantities are compared with distinct commercial γ-ray attenuating glasses, alloys, polymers, concretes and lead and ceramics corresponding values. Next, equivalent atomic numbers (Zeq) and by employing geometric progression (G–P) fitting method at 1–40 mfp PDs (penetration depths), at 0.015–15 MeV energy range ‘buildup factors’ were calculated. At all chosen twenty-five energies derived radiation protection efficiency (RPE) results assured investigated samples exemplary competence for low energy photons absorption. Applying SRIM codes ΨP and ΦP and ΨA and ΦA (mass stopping powers (MSPs) and projected ranges (PRs) for protons and α-particles), and making use of ESTAR database ΨE (electron MSP) and continuous slowing‐down approximation (CSDA) range for electrons are determined at KE (kinetic energy) range of 0.015–15 MeV. Moreover, fast neutron removal cross-sections (ΣR), for 0.0253 eV energy neutrons absorption cross-sections have been estimated. Deduced ΣR was altered at 0.1105–0.1205 cm−1 range with Bi2O3 inclusion in studied samples. 10Bi2O3-70B2O3-20Li2O (mol%) glass has greater total cross-section (=23.251 cm−1) for thermal neutrons absorption while 55Bi2O3-35B2O3-10Li2O (mol%) sample exhibits quality shielding factors for photons and fast neutrons confirming the included Bi2O3 positive impact. Along with nuclear attenuation features various physical and mechanical aspects are also inspected. Derived Vm (molar volume), OPD (oxygen packing density), Vo (oxygen molar volume), Vt (packing density) and Gt (dissociation energy per unit volume) values indicated glasses rigidity. Following Makishima–Mackenzie's theoretical model primary mechanical features like Y, K, S and L (Young's, bulk, shear and longitudinal modulus) and σ (Poisson's ratio) are evaluated where 10Bi2O3-70B2O3-20Li2O (mol%) glass shows better elastic moduli in all samples.

In-depth survey of nuclear radiation attenuation efficacies for high density bismuth lead borate glass system

MCNPX, Geant4 and FLUKA codes are employed to compute mass attenuation coefficients (μ/ρ) for 20Bi2O3-(80-x)B2O3-xPbO (x = 0, 20, 30, 40 and 60 mol%) glasses at 20, 30, 40 and 60 KeV, 133Ba (81, 161, 223, 276, 303, 356 and 384 keV), 57Co (122 and 136 KeV), 22Na (511 and 1275 keV),137Cs (662 keV),54Mn (835 keV), 60Co (1173 and 1333 keV) and 42K (1524 keV) photon peaks where 20, 30, 40 and 60 KeV energies are utilized for Mammography, Dental, General and Computed tomography (CT) scanning accordingly, in this study. All simulated μ/ρ outcomes accuracy was verified by WinXCOM and Phy-X/PSD programs’ μ/ρ findings and we noticed a satisfactory agreement among them. From μ/ρ and linear attenuation coefficient (μ) values effective atomic number (Zeff), effective electron density (Neff), half-value layer (HVL), tenth-value layer (TVL) and mean free path (MFP) have been determined. 20Bi2O3-20B2O3-60PbO (mol%) glass HVL and MFP have been compared with some commercial glasses, alloys, polymers, concretes and lead and ceramics corresponding values. Later equivalent atomic numbers (Zeq) and applying geometric progression (G–P) fitting method at 1 – 40 mfp penetration depths (PDs) at 0.015–15 MeV energy range exposure buildup factors (EBFs) and energy absorption buildup factors (EABFs) were estimated. At all selected twenty energies derived radiation protection efficiency (RPE) results confirmed studied samples’ excellent efficacy for low energy photons absorption. Moreover, applying SRIM codes mass stopping powers (MSPs) and projected ranges (PRs) for protons and α-particles and utilizing ESTAR database electron MSPs and continuous slowing down approximation (CSDA) range for electrons were determined at kinetic energy (KE) range of 0.015–15 MeV. Further fast neutron removal cross-sections (ΣR), for 0.0253 eV energy neutrons coherent and incoherent scattering cross-sections (σcs and σics), absorption cross-section (σA) and total cross-section (σT) quantities were evaluated. Derived ΣR was changed at 0.1166–0.123 cm−1 range depending on PbO addition in chosen samples. 20Bi2O3-80B2O3 (mol%) glass has larger σT (23.094 cm−1) in all studied samples for thermal neutron absorption while 20Bi2O3-20B2O3-60PbO (mol%) sample shows superior attenuation factors for photons and fast neutrons signifying included PbO positive effect.

Calculation of dose point kernel values for monoenergetic electrons and beta emitting radionuclides: Intercomparison of Monte Carlo codes

Targeted radionuclide therapy (TRT) and beta-emitting seeds brachytherapy (BSBT) exploit the characteristics of energy deposited by beta-emitting radionuclides. Monte Carlo (MC) modelling of electron transport is crucial for calculations of absorbed dose for TRT and BSBT. However, computer codes capable of providing consistent results are still limited. Since experimental validations show several difficulties, the estimation of electron dose point kernel (DPK) is often used to verify the accuracy of different MC codes. In this work, we compared DPK calculations for various point, isotropic and monoenergetic electron sources and several beta-emitting radioisotopes using the codes MCNP, EGSnrc, PENELOPE and TOPAS with different simulation options. The simulations were performed using latest versions of EGSnrc and Penelope, TOPAS version 3.3.1 and MCNP version 6.1 Monte Carlo codes. In our simulations, the geometrical model consists of a point electron source placed at the center of a water sphere emitting isotropically. The water sphere was divided into 28 shells and the energy deposition was scored within these shells. The radius of the outermost shell was 1.2R0, where R0 is the continuous slowing down approximation (CSDA) range. Five monoenergetic beta sources with energies of 0.05, 0.1, 0.5, 1 and 3 MeV were studied. Six beta-emitting radionuclides were also simulated: Lu-177, Sm-153, Ho-166, Sr-89, I-131 and Y-90. Monoenergetic electron simulations showed large deviations among the codes, larger than 13% depending on the electron energy and the distance from the source. In the cases where beta spectra of radionuclides were simulated, all MC codes showed differences from EGSnrc (used as reference value - RV) less than 3% within rE90 range (radius of the sphere in which 90% of the energy of the spectrum electrons would be deposited). TOPAS showed results comparable to EGSnrc and PENELOPE. DPK values for 0.1 MeV monoenergetic electrons, calculated using MCNP6, led to differences higher than ±5% from RV despite our attempts to tune electron transport algorithms and physics parameters.

Binary B2O3–Bi2O3 glasses: scrutinization of directly and indirectly ionizing radiations shielding abilities

For five B2O3–Bi2O3 glasses, detailedly, γ, neutron, & proton, alpha, and electron (charged particles) shielding efficacies were assessed in this work. The crucial photon attenuating (interaction probabilities) parameter i.e., mass attenuation coefficient (μ/ρ) was calculated by Phy-X/PSD software and procured μ/ρ results have been verified through MCNPX, Geant4, & FLUKA codes μ/ρ findings from which a quality unanimity among them was noticed over an energy range of 15 KeV–15 MeV. Following μ/ρ & linear attenuation coefficient (μ) outcomes, Zeff, Neff, HVL, TVL, and MFP have been reckoned and found that all μ/ρ, Zeff, Neff, HVL, TVL, & MFP highly rest on glass chemical contents & photon energy. Zeq and by applying geometric progression (G‒P) fitting parameters (a, b, c, d, & Xk coefficients) EBFs & EABFs were appraised at ten specific penetration depths up to 40 mfp, at energy range of 0.015–15 MeV. The inferred RPE quantities confirmed all chosen glasses quintessential absorption competence for lower energy γ-rays. Utilizing SRIM code the mass stopping powers (MSPs) & projected ranges (PRs) for protons ((ΨP)&(ΦP)) and alpha particles (ΨA)&(ΦA), and with the help of ESTAR database, electron MSP (ΨE) & continuous slowing down approximation (CSDA) ranges for electrons have been approximated at 0.015–15 MeV KE. The fast neutron removal cross-sections (ΣR) were estimated and obtained ΣR was diversified at 0.10978–0.12144 cm−1 range relying on Bi2O3 inclusion in glasses. Based on all acquired outputs, 57.5B2O3-42.5Bi2O3 (mol%) glass possesses superior attenuation capacity for γ-rays and fast neutrons as well as charged particles.