Search

Energetic ion beam experiments with major space radiation elements, 1H, 4He, 16O, 28Si and 56Fe, have been conducted to investigate the radiation shielding properties of composite materials. These materials are expected to be used for parts and fixtures of space vehicles due to both their mechanical strength and their space radiation shielding capabilities. Low Z materials containing hydrogen are effective for shielding protons and heavy ions due to their high stopping power and large fragmentation cross section per unit mass. The stopping power of the composite materials used in this work is intermediate between that of aluminum and polyethylene, which are typical structural and shielding materials used in space. The total charge-changing cross sections per unit mass, σ UM , of the composite materials are 1.3–1.8 times larger than that of aluminum. By replacing conventional aluminum used for spacecraft with commercially available composite (carbon fiber / polyether ether ketone), it is expected that the shielding effect is increased by ∼17%. The utilization of composite materials will help mitigate the space radiation hazard on future deep space missions.

The main rationale for using charged particles in radiation therapy is the strong rise of energy loss (deposited dose) with maximum penetration depth ( Bragg peak) and rapid dose deposited behind the peak. Thus, a large dose can be applied to a deep seated tumor, with saving the surrounding normal tissues . Proton radiotherapy is nowadays an established method in the management of cancer diseases, although its availability is still limited to a few specialized centers. In this study, the range and the stopping power for proton interaction in the skeleton and intestine tissues, for an energy range from 0.01 to 300 MeV, was studied. The numerical calculations and analyses of Bethe Ziegler, along with CASP and SRIM software programs, were applied using Matlab program. The absorbed dose and the Bragg peak were calculated and presented as tables and figures .

In the current study, 10PbO-xSrO-(90-x)B2O3 (x is between 20 and 45 mol% with a step of 5 mol%) glasses with SrO inserted in various proportions were surveyed in terms of nuclear shielding qualities. Gamma- ray shielding features of the glasses encoded BPS1-BPS6 were investigated in the energy range of 0.015–15 MeV. The mass attenuation coefficients (MAC) of BPS glasses were composed via GEANT4 simulation codes and the accuracy of the outcomes was checked by WinXCOM software. The MAC values of BPS1 and BPS6 glasses were obtained between 14.934–0.024 g/cm2 and 19.047–0.029 g/cm2 in the energy range of 0.015–15 MeV. Further, other essential parameters, MFP, Zeff, Zeq, EABF, and EBF were derived from the MAC values for the same energies. It was noted that the MFP values of the BPS6 glass are higher than some commercial glasses and ordinary concrete at chosen energy intervals. According to the results achieved, EBF, EABF, and MFP values decline as the percentage of SrO in the BPS glasses increases. The highest Zeff was achieved by BPS6 (with 45% SrO), while the lowest Zeff was obtained by BPS1 (with 20% SrO). Finally, fast neutron removal cross-sections (ΣR), Mass Stopping Power (MSP), and Projected Range (PR) values were computed to investigate the fast neutron, proton and alpha shielding properties of SrO added BPS glasses. It is seen that the ΣR values of BPS glasses vary in the range of 0.126 cm−1–0.117 cm−1. The addition of SrO in the glass leads to reduce the ranges of charged and uncharged particles. According to the outcomes achieved, BPS6 glass with 45% SrO additives can be regarded as an effective radiation shield used in many technological disciplines.

The vacancy production behavior for a broad range of incident ion-target combinations were examined by using both the full cascade (F-C) and quick calculation of damage (Q-C) options of Stopping and Range of Ions in Matter (SRIM-2013) code. Vacancy production for each option was evaluated using both the convenient vacancy text file in SRIM, and by manual manipulation of the energy transfer, ionization, and phonon text file data to calculate the depth-dependent damage energy for the Norgett-Robinson-Torrens (NRT) defect production model. The F-C vacancy text file method was observed to overpredict vacancy production by a factor of ~1.1 to 4 times when compared to values calculated using the F-C damage energy method or either of the SRIM Q-C methods. Based on our extensive data set obtained for 142 unique bombarding ion-target combinations, we show that the SRIM F-C vacancy text file method should not be used for vacancy production calculations. This error appears to be due to mischaracterization within the SRIM F-C option of some near-threshold replacement events as vacancies instead of replacements. Use of the latest SRIM stopping powers in the SRIM F-C approach provides a better calculation of electronic and nuclear stopping compared to the Lindhard stopping power analytical approximation used to calculate the damage energy of recoil atoms in the SRIM Q-C option, and therefore SRIM F-C approach is deemed to provide the best accuracy for vacancy production (within the binary collision approximation) as long as the damage energy method is used. Alternately, the SRIM Q-C option using either the vacancy.txt or damage energy method provides relatively fast calculation speeds with moderate quantitative differences from the F-C damage energy results (~0 to ~ 30% for the investigated ion-target cases).

Stopping powers (SP) for electrons with energies greater than 10 keV are well described through the Bethe approximation. However, for energies below, such an approach is inadequate. SP in LiF, CaF2 and Al2O3 as the luminescent materials commonly used for dosimetry study and liquid-water are scarce at energies below 10 keV. This work investigated SP and CSDA-range of electrons in in these compounds from the energy gap up to 433 keV using the full Penn algorithm. In particular, the influence of the exciton states was evaluated. The experimental optical data were selected after a rigorous evaluation process. The results indicate that the exciton states affect the SP mainly at energies below 100 eV by up to 48%, 39%, 32% and 15% for liquid-water, LiF, CaF2 and Al2O3, respectively. Furthermore, we observed a certain relationship between the minimum excitation-energy (exciton state) and the energy at which the SP is maximum.

International audience; The Timepix chip has been exposed to the outer space for the first time with the SATRAM (Space Application of Timepix-based Radiation Monitor) instrument on Proba-V (Project for On-Board Autonomy Vegetation), a European Space Agency’s (ESA) satellite. This study’s objective is to develop a new technique to improve the separation of protons and electrons, which are detected by the single layer Timepix detector in SATRAM. The current identification method, proposed by S. Gohl et al. [1], is based on pattern recognition and stopping power measurements. In this article, the limitations of this method are discussed. A new method based on neural network trained with Geant4 data is proposed. Its validation with SATRAM data is presented. Similarly, a neural network trained with Geant4 data is introduced. Its purpose is to deduce the particles’ incident energy using the energy deposited in the Timepix.

This experiment investigated the theory of energy loss in charged particles in plasma using a semi-classical method based on quantum scattering theory. The energy loss was expressed in terms of the transport cross-section for electron–ion scattering, which is calculated by semiclassical approximation of the scattering phase shifts. Exact numerical integration of the Schrodinger equation is used to test the derived results. This approach provides a non-perturbative representation of the energy loss, which bridges the gap between classical and quantum descriptions. On the other hand, the semi-classical method shows the correct behaviour of all plasma conditions and projectile charges and velocities. All equations have been programmed to present results using FORTRAN-90, and a program has been written for numerical calculations.

Purpose To develop a particle transport code to compute w-values and stopping power of swift ions in liquid water and gases of interest for reference dosimetry in hadrontherapy. To analyze the relevance of inelastic and post-collisional processes considered. Methods The Monte Carlo code MDM was extended to the case of swift ion impact on liquid water (MDM-Ion). Relativistic corrections in the inelastic cross sections and the post-collisional Auger emission were considered. The effects of introducing different electronic excitation cross sections were also studied. Results The stopping power of swift ions on liquid water, calculated with MDM-Ion, are in excellent agreement with recommended data. The w-values show a strong dependence on the electronic excitation cross sections and on the Auger electron emission. Comparisons with other Monte Carlo codes show the relevance of both the processes considered and of the cross sections employed. W and w-values for swift electron, proton, and carbon ions calculated with the MDM and MDM-Ion codes are in very close agreement with each other and with the 20.8 eV experimental value. Conclusion We found that w-values in liquid water are independent of ion charge and energy, as assumed in reference dosimetry for hadrontherapy from sparse experimental results for electron and ion impact on gases. Excitation cross sections and Auger emission included in Monte Carlo codes are critical in w-values calculations. The computation of this physical parameter should be used as a benchmark for micro-dosimetry investigations, to assess the reliability of the cross sections employed.

A special version of the SHIELD transport code has been developed intended for radiation protection purposes in space. The calculation of the fluxes of primary and secondary particles and the absorbed dose rate in a water phantom behind various shielding under the influence of galactic cosmic rays (GCRs) using the GCR model developed by the Institute of Nuclear Physics, Moscow State University. The code architecture is briefly described as a version of SHIELD including models of nuclear reactions. Stopping power dE/dX(E) is calculated in the energy range of 10 keV/nucleon–100 GeV/nucleon. The calculation was performed in spherical geometry, which allows, in a simple formulation of the problem, to compare the fluxes of particles of different types in the phantom, as well as to estimate the contribution to the dose of different GCR components depending on the protection parameters.

This research article focuses on the significant role of Tb2O3 content on the optical properties and radiation shielding performance of Ga2O3–B2O3–Al2O3–GeO2 glasses named as GBAGT1, GBAGT2, GBAGT3, and GBAGT4 for Tb2O3 of 14, 18, 22 and 25 mol%, respectively. The findings of the optical study indicate that the optical dielectric constant of the present samples increased from 1.85 to 2.06 as the Tb2O3 content increased from 14 to 25 mol%. The results of the radiation shielding confirm that increasing Tb3+-dopant content in GBAGT4 increased its specific gamma ray constant (Γ) values over all other glass samples in the whole energy region. With increasing electron energy, the mass stopping power decreased for all samples and reached the minimum 1.372 and 1.327 (MeV cm2/g) for BGAGT1, BGAGT4, respectively, at 1 MeV electron energy. For a beam of neutrons of 0.1 meV, the total cross section in GBAGT1, GBAGT2, GBAGT3, and GBAGT4 was 294.54, 312.88, 317.24 and 311.69 (cm−1), respectively. The smallest MFP values of GBAGT4 glass sample in all energy regions confirm the superior shielding performance of the studied glass sample among other shielding materials namely traditional concrete and commercial polymers/glasses.

In this work we investigate the energy-loss straggling of low and medium energy protons on available simple materials (C, Al, Si, Ni, Cu, Zn, Ge, Se, Pd, Ag, Sb, Pt, Au, Pb) and demonstrate that the well-known Yang-O’Connor-Wang empirical formula for the energy-loss straggling of protons in matter has a clear physical interpretation. This formula predicts, on empirical grounds, energy-loss straggling values for protons that exceed the values of traditional straggling formulas (e.g., by Lindhard and Chu) at energies around 0.3 MeV/amu by a factor of 2–3. This excess is correlated to the bunching effect, which comes from the inhomogeneity feature of the electron density. Although this effect is specific to each element and can be calculated using e.g. the CasP and PASS programs, a single formula correlates better with overall experimental values. The Yang-O’Connor-Wang formula was refined accounting for subsequent experimental data.

The electronic stopping losses for p–He and p–Ar systems are compared with independent measurements of cross sections for elementary processes. It is shown that quantitative agreement can be reached if the fact that significant energy losses are carried away by knocked-out electrons is taken into account. The dependence of the average energy of knocked-out electrons on the impact velocity for velocities that are smaller than 1.5 a.u. can be described within the framework of dynamic ionization theory. It is established that the equilibrium charge of beam particles depends on the ratio of the stripping and charge-exchange cross sections, and the use of frequently applied universal models for description of the equilibrium charge in the case under consideration is not justified. It is shown that the contribution of excitation processes for the studied cases does not exceed 7–12%, which differs from traditional concepts of equality between the contributions of ionization and excitation processes. The inclusion of multiple ionization processes, which increases the electronic stopping power by 6% in the case of p–He and by 23% in the case of p–Ar, turns out to be important.

The results of numerical calculating the total Mott-Bloch correction to the Bethe stopping formula and the Lindhard-Sorensen correction in the point nucleus approximation, as well as the Mott correction and the difference between the Lindhard-Sorensen and Bloch corrections, which were obtained by some rigorous and approximate methods, are compared for the ranges of a gamma factor of approximately from 1 to 10 and the ion nuclear charge number Z from 6 to 114. It is shown that the accurate calculation of the Mott-Bloch corrections based on the Mott exact cross section using a method previously proposed by one of the authors gives excellent agreement between its values and the values of the Lindhard-Sorensen corrections in the gamma and Z ranges under consideration. In addition, it is demonstrated that the results of stopping power calculations obtained by the two above-mentioned rigorous methods coincide with each other up to the seventh significant digit and provide the best agreement with experimental data in contrast with the results of some approximate methods, such as the methods of Ahlen, Jackson-McCarthy, etc., Comment: 16 pages, 3 tables, 5 figures, PDF

One widely used expression of electronic stopping power is the Bethe stopping power, which is used in many applications such as radiation dosimetry. Various studies have presented methods to approximate the analytical solution of the Bethe stopping power. In this study, analytical solution obtained previously from the study by Gonzalez-Gaxiola et al. is extended to relativistic energies by using relativistic relations prior to implementation of the Laplace–Adomian decomposition method (LADM). The series solution obtained from the LADM method is a function of the path length traversed and the initial energy of the charged particle. Our solution results in relatively good agreement with numerical simulation for different incident energies, absorbing media, and particle types. Plots of relative difference illustrate increasing deviations between LADM and numerical solution towards the end of the particle range due to exclusion of higher order terms.

The present work investigated the 40P2O5−20CaO−(30-x)Na2O−10K2O–xBi2O3 where x: 0, 2.5, 5, 7.5, and 10 mol% for potential use in radiation shielding applications. For this purpose, the BiCKNP series (1–5) were synthesized by using melt quenching technique. The structural properties were determined by applying X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) while glass density was figured out with the use of Archimede’s principle. Furthermore, the radiation shielding characteristics of the proposed glass systems were computed via the user-friendly Phy-X/PSD and MATLAB® softwares. According to the determinations, we found out that the glass density was increased from 2.3337 to 3.5182 g cm− 3 with the insertion of Bi2O3 from 0 to 10 mol%. From the XRD measurements, it was seen that all the selected samples are glassy materials with evident amorphous structures. In this FTIR spectra, the bands at ~ 520 cm− 1, ~ 710 cm− 1, ~ 880 cm− 1, ~ 1080 cm− 1, ~ 12,100 cm− 1, and ~ 1366 cm− 1 were determined, and the related oxide bands were highlighted. Moreover, the radiation shielding computations revealed that BiCKNP5 has the most linear attenuation coefficient (LAC) out of the BiCKNP glasses. Based upon the LAC determinations, the other essential parameters such as mass attenuation coefficient (MAC), mean free path (MFP), half-value layer (HVL), tenth-value layer (TVL), effective atomic number (Zeff), and effective electron density (Neff) were throughly calculated by using MATLAB® software. Additionally, mass stopping power (MSP) and projection range (PR) values were calculated by using SRIM Monte Carlo codes. It was observed that BiCKNP1 glass is greatly effective for protection against H1 and He+ 2, and BiCKNP5 has the largest range of 782.04 × 10− 1 mm, while BiCKNP1 has the lowest range of 689.28 × 10− 1 mm for PR protons (H1) calculated at 10 MeV energy. Lastly, we determined that BiCKNP5 and BiCKNP1 have the lowest and highest values ∑R (0.07886 and 0.09408 cm− 1) respectively.

One of the major problems for attaining fusion is to heat the plasma particles to very high temperatures. High gain is essential for a fusion reactor and greater energy efficiency can reduce energy costs. Ion beam injection is one method used to heat plasma inside a fusion reactor. A fusion of deuteron with the isotope lithium-6, D6Li is more difficult than a fusion of deuterium and tritium,DT. In this paper, it is proposed to inject laser-driven deuteron beam in the fast ignition (FI) scheme for inertial confinement fusion (ICF) in the D6Li plasma. Fusion occurs as injected high-energy deuteron ions slow down in the plasma. The results show that the reaction probability increases by increasing electron temperature. The stopping power of electrons and ions decrease with the increase of temperature. When the energy of deuteron beam is achieved at a few hundred keV, stopping power of the electrons would be more than ions. Nuclear stopping power is considerable at very low deuterons energies. The deuteron beam range reduces as incident energy decreases. At low hot spot temperatures, deuterons can be deposited immediately within a very little range. The contribution of the released energy due to the deuteron beam interaction with ions into D6Li plasma provides the additional heating, which generally increases the energy efficiency. The investigations indicate that fusion energy efficiency is independent of lithium-6 numerical density, initial deuteron beam range and increases with electron temperature. The highest value of energy efficiency occurs with lower energy deuteron beam around the 2.5-MeV range from deuteron beam-target fusion.

The electronic stopping powers of LR-115 and Kapton polymeric foilshave been estimated, using Monte Carlo simulations, for 9 Be, 11 B, 12 C, 14 N, 16 O, and 35 Cl ions covering the energy range ~ 0.1-1.0 MeV/n. Comparison of stopping power based on Lindhard, Scharff, and Schiott (LSS) theory with the corresponding values obtained by SRIM and MSTAR codes in LR-115 and Kapton polymeric foils illustrate a significantly large deviations. However, a semiempirical equation has been proposed here and tested for better stopping power calculations at low-energy regime in the domain of LSS theory for Z = 4-8 ions across materials. Furthermore, the electronic energy losses for 9 Be and 16 O ions in SiO 2 and Al 2 O 3 , respectively, have been calculated in the energy range of ~ 0.1-1.0 MeV/n. The calculated stopping powers exhibit up to 10 % deviation from the experimental values and MSTAR data.

Purpose This paper presents a novel method for the calculation of three-dimensional (3D) Bragg-Gray water-to-detector stopping power ratio (sw,det ) distributions for proton and carbon ion beams. Methods Contrary to previously published fluence-based calculations of the stopping power ratio, the sw,det calculation method used in this work is based on the specific way GATE/Geant4 scores the energy deposition. It only requires the use of the so-called DoseActor, as available in GATE, for the calculation of the sw,det at any point of a 3D dose distribution. The simulations are performed using GATE-RTion v1.0, a dedicated GATE release that was validated for the clinical use in light ion beam therapy. Results The Bragg-Gray water-to-air stopping power ratio (sw,air ) was calculated for monoenergetic proton and carbon ion beams with the default stopping power data in GATE-RTion v1.0 and the new ICRU90 recommendation. The sw,air differences between the use of the default and the ICRU90 configuration were 0.6% and 5.4% at the physical range (R80 - 80% dose level in the distal dose fall-off) for a 70 MeV proton beam and a 120 MeV/u carbon ion beam, respectively. For protons, the sw,det results for lithium fluoride, silicon, gadolinium oxysulfide, and the active layer material of EBT2 (radiochromic film) were compared with the literature and a reasonable agreement was found. For a real patient treatment plan, the 3D distributions of sw,det in proton beams were calculated. Conclusions Our method was validated by comparison with available literature data. Its equivalence with Bragg-Gray cavity theory was demonstrated mathematically. The capability of GATE-RTion v1.0 for the sw,det calculation at any point of a 3D dose distribution for simple and complex proton and carbon ion plans was presented.

Purpose Accurate dose calculation is a critical step in proton therapy. A novel machine learning-based approach was proposed to achieve comparable accuracy to that of Monte Carlo simulation while reducing the computational time. Methods Computed tomography-based patient phantoms were used and three treatment sites were selected (thorax, head, and abdomen), comprising different beam pathways and beam energies. The training data were generated using Monte Carlo simulations. A discovery cross-domain generative adversarial network (DiscoGAN) was developed to perform the mapping between two domains: stopping power and dose, with HU values from CT images incorporated as auxiliary features. The accuracy of dose calculation was quantitatively evaluated in terms of mean relative error (MRE) and mean absolute error (MAE). The relationship between the DiscoGAN performance and other factors such as absolute dose, beam energy and location within the beam cross-section (center and off-center lines) was examined. Results The DiscoGAN model is found to be effective in dose calculation. For the abdominal case, the MRE is found to 1.47% (mean), 3.30% (maximum) and 0.67% (minimum). For the thoracic case, the MRE is found to ~2.43% (mean), 4.80% (maximum) and 0.71% (minimum). For the head case, the MRE is found to ~2.83% (mean), 4.84% (maximum) and 1.01% (minimum). Comparable accuracy is found in the independent validation dataset (different CT images), achieving a mean MRE of ~1.65% (thorax), 4.02% (head) and 1.64% (abdomen). For the energy span between 80 and 130 MeV, no strong dependency of accuracy on beam energy is found. The results imply that no systematic deviation, either over-dose or under-dose, occurs between the predicted dose and raw dose. Conclusion The DiscoGAN framework demonstrates great potential as a tool for dose calculation in proton therapy, achieving comparable accuracy yet being more efficient relative to Monte Carlo simulation. Its comparison with the pencil beam algorithm (PBA) will be the next step of our research. If successful, our proposed approach is expected to find its use in more advanced applications such as inverse planning and adaptive proton therapy.

This paper aims to evaluate the range and stopping power of alpha particles in argon gas at different pressure of 0 to 1 bar, using the alpha radiation energy. The results show that the energy of the passed alpha particles has been decreased with increasing pressure in a small vacuum chamber. It is also observed that the amount of alpha particles reaching the detector follows a decreasing behavior as the distance increases. Experimental, SRIM and theoretical results for range and stopping power are closely in a good agreement. The errors in the measured range and stopping power data results from random. Only random errors have been considered in the present analysis and were estimated from pressure measurements and the uncertainty of the gas temperature.

The current study aims to explore the shielding properties of multi-component borate-based glass series. Seven glass-samples with composition of (80-y)H3BO3–10ZnO–10Na2O–yBaO where (y = 0, 5, 10, 15, 20, 25 and 30 mol.%) were synthesized by melt-quench method. Various shielding features for photons, neutrons, and protons were determined for all prepared samples. XCOM, Phy-X program, and SRIM code were performed to determine and explain several shielding properties such as equivalent atomic number, exposure build-up factor, specific gamma-ray constants, effective removal cross-section (ΣR), neutron scattering and absorption, Mass Stopping Power (MSP) and projected range. The energy ranges for photons and protons were 0.015–15 MeV and 0.01–10 MeV, respectively. The mass attenuation coefficient (μ/ρ) was also determined experimentally by utilizing two radioactive sources (166Ho and 137Cs). Consistent results were obtained between experimental and XCOM values in determining μ/ρ of the new glasses. The addition of BaO to the glass matrix led to enhance the μ/ρ and specific gamma-ray constants of glasses. Whereas the remarkable reductions in ΣR, MSP, and projected range values were reported with increasing BaO concentrations. The acquired results nominate the use of these glasses in different radiation shielding purposes.

Absorbed dose and stopping power of the target material are two important parameters for determining the radiation effects. In this work, the relationship between these two parameters has been investigated for electron beams incident on skin and muscle tissue. Absorbed dose was obtained by using the EGSnrc code and the stopping power values were calculated by considering the velocity-depended effective charge and mean excitation values. To obtain the relationship between absorbed dose and stopping power values, these parameters were graphed together and simple fitting functions have been obtained. The results obtained show that these parameters are linearly correlated with each other.

Metal halide perovskites have emerged as promising candidates for next-generation optoelectronic applications due to their high absorption coefficient, tunable bandgap, long carrier mobility, and facile solution processability. Besides these excellent physical properties, their unique features, including large bulk resistance, strong stopping power, and high mobility-lifetime product, also favour halide perovskites for radiation detection. Their excellent radiation response and radioluminescence enable them as both direct detectors and indirect scintillators with excellent figures-of-merit, even exceeding the performance of existing commercial radiation detectors. In this review, the background knowledge on ionizing radiation categorized based on the nature of the particles or electromagnetic waves and the requirements for high-performance radiation detectors are provided first. Then, the relevant fundamental characteristics and superiorities of metal halide perovskites for radiation detection are discussed in detail. Thereafter, recent achievements in detecting alpha-, beta-, gamma- and X-rays using halide perovskites are summarised. Finally, the remaining challenges and future perspectives, with particular emphasis on overcoming current obstacles, such as device stability, ion migration, and health concerns, are highlighted.

The production of brachytherapy radio-nuclide 169Yb was investigated in the 169Tm(p,n), 170Yb(p,2n), 171Yb(p,3n), 172Yb(p,4n), 169Tm(d,2n), 168Er(α,3n), 167Er(α,2n) and 166Er(α,n) reactions. The cross section of these reactions were calculated using TALYS 1.9 code and compared with the available experimental results. SRIM-2013 code and GEANT4 toolkit were used to calculate the stopping power, range and projectile flux within the target. The optimum target thickness, theoretical and simulation production yield of 169Yb radioisotope in each reaction were calculated. Finally, the 169Tm(p, n) reaction with high production yield was suggested to produce 169Yb radioisotope.

Most sputtering yield measurements for solid N 2 are reported for stopping powers lower than 10 − 13 eV cm 2 /molecule. We measured the sputtering yield for solid N 2 at stopping powers, in the electronic regime, above 10 − 12 eV cm 2 /molecule, extending the range of such measurements by more than an order of magnitude, using a 33 MeV 58Ni 9 + swift heavy ions beam. The evolution of the thin N 2 ice films was monitored in-situ by mid-infrared spectroscopy (FTIR) during irradiation. As N 2 is only weakly infrared active, and can be hardly monitored directly via an infrared absorption mode in such experiments, we use the Fabry–Perot interference fringes of the ice film to evaluate, via an optical model, the erosion of the N 2 film as a function of ion fluence. A sputtering model including several sputtering crater shapes is developed and tested against experimental data. We derive the sputtering yield for a semi-infinite N 2 ice film and its dependence with the ice thickness for thin film conditions, monitoring the N 2 ice sputtering depth. We combine the results with previous measurements at lower stopping powers to derive the electronic sputtering of solid N 2 over a large stopping power range.

Boron carbide is a material proposed as an alternative to graphite for use as an energy degrader in proton therapy facilities, and is favoured due to its mechanical robustness and promise to give lower lateral scattering for a given energy loss. However, the mean excitation energy of boron carbide has not yet been directly measured. Here we present a simple method to determine the mean excitation energy by comparison with the relative stopping power in a water phantom, and from a comparison between experimental data and simulations we derive a value for it of 83.1 ± 2.8 eV suitable for use in Monte-Carlo simulation. This is consistent with the existing ICRU estimate (84.7 eV with 10–15% uncertainty) that is based on indirect Bragg additivity calculation, but it has a substantially smaller uncertainty. The method described can be readily applied to predict the ionisation loss of other boron carbide materials in which the atomic constituent ratio may vary, and allows this material to be reliably used as an alternative to graphite, diamond or beryllium.

In this paper, the Primary Knock-on Atoms (PKAs) density and energy distributions in InAlAs and InGaAs materials have been analyzed by an energy stopping power improved Monte Carlo (MC) method under proton-radiation with energies of 25 keV, 50 keV, 100 keV, and 150 keV. The results show that in the initial incident stage of protons, the electronic energy loss density is 2–3 orders of magnitude higher than the nuclear energy loss density, afterwards, the injected protons accelerate to deposit more energy and finally stop in the target, producing a large number of PKAs. The injected proton density, PKA density and PKA energy density almost follow a Bragg-shape distribution. With the increase of irradiation energy, their peak-positions shift toward deeper direction with peak values decrease gradually, and moreover, the PKA peaks are always shallower than the irradiated protons. In addition, Frenkel Pairs generation rate has been calculated based on Kinchin-Pease (K-P) model modified by Ziegler, which decreases as proton energy increases because of the reduction of scattering cross section. The verification of this method combines both SRIM 2013 and Northcliffe experimental data and the results have shown compatible trends.

In the present investigation, mass attenuation coefficients ( μ m ) and some related nuclear shielding quantities of various granite samples have been computed at several photon energies of 0.356, ...

In this study, the uncharged/charged and photon shielding features of TeO2.Ta2O5.ZnO/ZnF2 tellurite-rich glass system with different ZnO/ZnF2 ratio (encoded as TTZ, TTZF4, TTZF8, TTZF12 and TTZF16) were comprehensively discussed. The mass attenuation coefficients (MAC) were achieved employing MCNPX simulation codes and the outcomes were verified with theoretical data computed by WinXCOM software. The MACs varied between 47.667 to 0.034 for TTZ glass (for ZnO=16 mol%) and the largest MAC values were gained for TTZ glass among the others. Several MAC-based photon attenuation parameters, Half Value Layer (HVL), equivalent atomic number (Zeq) and Exposure Buildup Factor (EBF), of TTZF glasses were also determined for the energy range of 0.015–15 MeV. The results indicated that the enhancement in ZnO grows the gamma-ray attenuation competences of TTZF glasses. Furthermore, removal cross section of fast neutrons (∑R) for TTZF glasses was found and it has been noted that higher glass density has enhanced the ∑R values. The ΣR values of TTZF glasses change between 0.1103-0.1174 cm-1. At last, projected range (PR) and mass stopping power (MSP) for charged particles has been investigated within the kinetic energy range between 0.01–10 MeV. It is found that all TTZF glasses possess nearly close MSP and PR values for proton and alpha particles. We trust that the results of this study will guide the radiation protection capabilities of tellurite-rich glass systems.

It is shown that the excitation of autoionization states during the collisions of keV-energy ions with a solid plays a determining role in the formation of inelastic energy losses and, accordingly, the electronic-stopping cross section Se. It is proposed to estimate the Se values using the relationship between the cross section for autoionization-state excitation and the ionization cross section. For cases where the ionization cross sections are unknown, scaling is used to calculate the ionization cross sections when the L and M shells are excited. The threshold dependence of Se versus the energy of bombarding ions is predicted.

In “Hiroshima in Iran: What Americans Really Think about Using Nuclear Weapons and Killing Noncombatants,” a pathbreaking survey of attitudes toward the laws of war published in the summer 2017 issue of International Security, Scott Sagan and Benjamin Valentino found that Americans are relatively insensitive to the targeting of civilian populations and to international norms and taboos against the use of nuclear weapons. We replicated a key question of this study, where respondents were asked if they would support saturation bombing an Iranian city to end a war. We also introduced some variations into the experiment to directly measure any potential influence of international norms and laws. Overall, our quantitative and qualitative findings are more optimistic than those of Sagan and Valentino's study: Americans do strongly believe it is wrong to target civilians. And in a real-life scenario such as this, a majority would likely oppose such a bombing. These findings suggest, however, that much depends on how survey questions are structured in measuring those preferences and whether legal or ethical considerations are part of any national conversation about war policy.

The stopping power of a material upon interaction with an energetic ion is the key measure of how far that ion will travel. The implications of accurate particle range calculations are tremendous, affecting every single application in which particle radiation is involved, from nuclear power to medicine. An approach is presented which attempts to overcome current shortcomings in the theoretical understanding of stopping power, as well as the methods used to interpret and exploit measured data. This is a considerable challenge, however the use of a novel machine learning methodology is shown to hold great promise in this endeavour: the ultimate aim being the ability to correctly predict the stopping value for any energy, ion and target combination, having no pre-existing experimental data. A random forest regression algorithm is trained using over 34,000 experimental measurements, representing stopping power values for 522 ion-target combinations across the energy range 10 - 3 to 10 2 MeV/amu, and ion and target atomic masses 1 to >240. Evaluation is carried out using several fundamental error metrics, over the whole dataset as well as for individual combinations, to provide the most comprehensive understanding of performance when tested under strict cross-validation criteria. The resulting model is shown to yield predicted stopping power curves corresponding closely to those of the true experimental values, with an ability to generalise across target elements, compounds, mixtures, alloys and polymers, irrespective of phase, and for a wide range of ion masses.

The nuclear stopping power of hydrogen and helium isotopes in Be, C, and W materials that are promising for use as the first wall of a tokamak reactor are calculated. It is shown that the presence of an attracting potential well has a substantial effect on the dependence of the nuclear stopping power on the collision energy. The use of potentials calculated in the approximation of the density functional theory with an attracting potential well has allowed us to obtain more accurate values of the nuclear stopping power for hydrogen isotopes, which differ by 27–60% from the tabular data at low energies. The results for different hydrogen isotopes are well described by a universal curve.

The Adult Male® and Adult Female® phantoms of ORNL were modified with Ir-192 source and additional tally cards from the MCNP® data library. The lung and eleven soft tissues were used for the study. The soft tissues include Liver, Stomach, Ovaries, Testes, Brain, Thyroid, Kidney, Pancreas, Gall Bladder, Heart, and the Small Intestine. The computational simulation was achieved using MCNPX with nps of 107 , and the data set of the lung and soft tissues derived for Malaysian population [14]. The relative error, R was

The ignition stage of deuterium-tritium fuel in inertial confinement fusion is a challenging task affected by many undesirable processes especially material mixing processes in the hot-spot region. In this research, an alternative proposal of the enhanced energy deposition in the proton fast ignition has been suggested. It consists of two primary assumptions of the beam-plasma system. In the first place, we have adopted the proton beam generated by TNSA or RPA mechanisms, each described by a Maxwellian or Gaussian energy distributions. Next, a realistic, non-uniform fuel plasma was adopted. Then, the cumulative stopping power of a proton beam of 10 kJ energy, penetrating the low content metal-contaminated deuterium-tritium fuel has been examined. It has been shown that in the case of the very low impurity fractions, irregular spatial fluctuations in the cumulative stopping power relative to pure fuel plasma emerges. However, at the higher concentrations, a systematic pattern becomes visible such that the contribution of the deep layers in the stopping power reduces. We observe the enhanced energy deposition close to the corona/dense core interface. It has been shown that the corona/dense core energy deposition ratio differs by up to 2.5% between pure and contaminated DT plasma. In the contaminated fuel plasma, energy deposition in the TNSA regime will effectively heat the plasma corona. While in the RPA counterpart, at a similar level of contamination, most of the incident beam energy remains inside the core fuel region.

Influence of Ag2O insertion on the nuclear radiation safety features of sodium zinc-tellurite glasses has been reported. To this end, six glasses of 80TeO2.10ZnO.[(10-x)Na2O.xAg2O)]: x = 0–10 mol% abbreviated as (TZNA0-TZNA10) have been chosen. The mass attenuation coefficients (μ/ρ) were simulated using MCNP-5 simulation codes and the results were matched with which calculated via XCOM software. In term of μ/ρ, half value layer, mean free path (HVL, MFP), effective atomic number, equivalent atomic number (Zeff, Zeq), exposure and energy absorption buildup factors (EBF, EABF), Mass Stopping Power (MSP) and the Projected range (PR) of the proton and alpha particles have been evaluated. Results reveal that the increase in Ag2O from 0–10 mol % enhances the attenuation properties of TZNA glasses and the μ/ρ takes the order that TZNA10>TZNA8>TZNA6>TZNA4>TZNA2>TZNA0. The insertion of Ag2O in the TZNA glasses reduced the HVL, MFP, and exposure buildup factors (EBF and EABF). In addition, the smallest values of MSP and PR for proton and alpha particles observed for TZNA10 glass. Moreover, the insertion of Ag2O leads to enhance the radiation safety capability of the TZNA glasses to apply in various medical applications.

Primary simulations of neutron interactions are performed on Si1− x Ge x alloys with a Monte Carlo (MC) code using the binary collision approximation (BCA). Then, a statistical study of the collision cascades development in Si0.8Ge0.2, Si0.7Ge0.3, and Si0.5Ge0.5 is carried out using molecular dynamics (MD), starting from both Si and Ge primary knock-on atoms (PKAs) of 1, 5, and 10 keV. The well-known Stillinger–Weber (SW) MD potential, which can be used to study Si, Ge, and Si1− x Ge x , is coupled to the Ziegler–Biersack–Littmark (ZBL) universal potential to better describe the collisions between atoms. To account for the stopping power of the electrons, the two-temperature model (TTM) is combined with MD. Similar studies are performed on pure Si and pure Ge in order to be able to compare our Si–Ge alloys damaged structures with reference materials. Moreover, data obtained by TTM-MD on Si, Ge, and Si1− x Ge x are compared with collision cascades statistical data from MC codes.

This paper studies the radiation attenuation properties and build up (EBF and EABF) factors of different types of bioactive glasses in the 0.015–15 MeV photon energy range. EBF and EABF values of investigated bioactive glasses are determined by using the G-P fitting method. Moreover, effective removal cross-section values, alpha/proton mass stopping power (MSP), and alpha/proton projected range values (PR) are determined for fast neutrons and charged particles. The investigation indicates that TiO2 additive in the bioactive glasses causes considerable variations in the attenuation properties of bioactive glasses. The results show that the BT2.5 bioactive glass sample has highest attenuation performance among the samples.

The stopping power and the range of alpha particles emitted from Am-241 source has been investigated in helium gas at different pressures of 0 to 1 bar, using surface barrier silicon detector in the large vacuum chamber. The energy loss has also been obtained at variable distances from 2 to 8 cm. It is observed that as the pressure in a large vacuum chamber increases, the energy loss of the alpha particle decreases. The measured energy loss of alpha particles at lower pressure of 0 bar is less, but at higher pressure of 1 bar is more. As expected from Bethe --- Bloch formula, the stopping power of charged particle in helium gas at different pressure was found to increase significantly when pressure is increased. The measured value of stopping power and range were compared with SRIM and theoretical value. The experimental value of stopping power and range was found to be very close to the SRIM and theoretical value. Then, the measured value of range was compared with experimental using the Bragg --- Kleeman's rule

The direct transfer reaction is a powerful tool in nuclear spectroscopy because the single particle properties of populated energy levels can be studied through the measurement. Furthermore, the transfer reaction using radioactive heavy ion beams in inverse kinematics has become crucial for the study of nuclei far from stability. For the design of a detector system including a scattering chamber for the transfer reaction measurements, the calculations including relativistic kinematics, stopping power, and Gamow window need to be performed many times. To make these calculations easier, we developed a new toolkit written in the Java programming language.

We report bond correction factors that can be used to calculate molecular mean excitation energies including the effects of chemical bonding. The calculations are based on an extension of Bragg’s rule. We report results for several bonds – neutral and charged - involving gas phase atoms in the first, second and third row of the periodic system. The bond correction factors are dimensionless and turn out to be nearly constant and of the order 1–2. The method is applied to the calculations of mean excitation energies of linear hydrocarbons, amino acids and molecules and molecular ions of astrophysical interest. Examples show that chemical binding effects increase the molecular mean excitation energies with between 4% and 15 %, smallest for linear, unsaturated molecules and largest for molecules with longer aliphatic chains.

Plastic scintillators are widely used in radiation portal monitors because of their low cost and availability in large sizes. However, due to their low density and low effective atomic number ( Z ), they offer low intrinsic efficiency and little spectroscopic information. The addition of high- Z constituents to these plastics can greatly increase both their total stopping power and the amount of photoelectric absorption, leading to full-energy deposition and thus useful gamma spectra. In this article, we present the performance of the latest formulation of Bi-loaded plastic scintillators showing their useful spectroscopic information up to relatively high energy (~1 MeV) due to their high stopping power compared to the current commercially available plastics. These Bi-loaded plastics use 20 weight percent (wt%) Bi-pivalate (8 wt% elemental Bi) dissolved in polyvinyltoluene (PVT) matrix and conventional fast fluors (~10 ns decay time). These Bi-loaded plastics achieve up to approximately 6000 photons/MeV and have been produced in sizes up to 17 in3. The performance of these Bi-loaded plastics is also demonstrated in the existing portal monitor hardware (Rapiscan Model TSA Trainer 770) showing the possibility to provide improved sensitivity as a drop-in replacement with continued scale-up.

Physically realized electron gas systems usually reside in either the quantum non-degenerate or fully degenerate limit, where the average de Broglie wavelength of the thermal electrons becomes comparable with the interparticle distance between electrons. A few systems, such as young brown dwarfs and the cold dense fuels created in imploded cryogenic capsules at the National Ignition Facility, lie between these two limits and are partially degenerate. The National Ignition Facility has the unique capability of varying the electron quantum degeneracy by adjusting the laser drive used to implode the capsules. This allows experimental studies of the effects of the degeneracy level on plasma transport properties. By measuring rare nuclear reactions in these cold dense fuels, we show that the electron stopping power, which is the rate of energy loss per unit distance travelled by a charged particle, changes with increasing electron density. We observe a quantum-induced shift in the peak of the stopping power using diagnostics that measure above and below this peak. The observed changes in the stopping power are shown to be unique to the transition region between non-degenerate and degenerate plasmas. Our results support the screening models applied to partially degenerate astrophysical systems such as young brown dwarfs. Transitions between non-degenerate and degenerate plasma are observed in laser-driven implosions of cryogenic capsules at the National Ignition Facility. The observed partially degenerate regime is relevant to the physics of young brown dwarfs.

A model for estimating the contribution of autoionization state formation to inelastic energy losses in collisions of keV-energy ions with solids is proposed. Using the suggested scaling for L and M shell excitation it is possible to estimate the ionization cross sections and the contribution of the ionization processes to the electronic stopping power dE/dx. The model predicts a threshold behavior of dE/dx. In the cases studied the formation of autoionization states gives important contribution to the value of dE/dx.

A general approach to modeling the mass loss of polymer composites under space conditions is proposed. The case of the effect of radiation-stimulated evaporation on the mass loss of the polymer composite in vacuum upon irradiation with 10–50 keV electrons is considered in detail. It is shown that the energy loss and density of the electron flow, as well as the mass fraction of the filler in the material, affect the mass loss of the polymer composite. In particular, it is found that the mass loss of the studied materials when irradiated in vacuum at a fixed density of the radiation energy flux decreases with increasing electron energy Е0. This is explained by the fact that the smaller Е0, the greater the stopping power; therefore, in larger quantities and in a thinner surface layer of the material, radiolysis products are produced. In this case, the gas permeability of the irradiated layer of the material grows with the energy absorbed in it, and the products of radiolysis are released into the vacuum more quickly. It is established experimentally that, at φ = 1011 cm–2 s–1, the mass loss of the materials studied occurs mainly via radiation-stimulated gas release, and at φ = 1012 cm–2 s–1 and the value of Е0 = 10 keV, the weight of the evaporated material in the total loss mass of polymeric material is more than 50%.

In the present work extensive stopping power calculations were performed, implementing general–purpose Monte Carlo codes (GEANT4, MCNP6.1, FLUKA, PHITS) and dedicated stopping power compilations (such as SRIM2013, PSTAR/ ASTAR from NIST and ATIMA), having protons, alpha particles, 12C, 16O and 56Fe ions as beam particles, in the energy range between ~1 and ~1000 MeV/u, impinging on a variety of thin or infinitely thick, pure, single–element targets, such as aluminum, iron, copper and silicon, which are typically used as shielding materials or components in complex devices, in order to investigate all the occurring differences and similarities in the obtained results. Water was the only compound target to be examined, since it is commonly used as a close substitute for biological tissue. In all the simulations the process of multiple scattering was ignored or disabled. The obtained results are presented in graphical form, along with all the available experimental data in the studied energy range and the occurring similarities and discrepancies are discussed and analyzed.

Purpose Monte Carlo (MC) simulation of radiation interactions with water medium at physical, physicochemical, and chemical stages, as well as the computation of biologically relevant quantities such as DNA damages, are of critical importance for the understanding of microscopic basis of radiation effects. Due to the large problem size and many-body simulation problem in the chemical stage, existing CPU-based computational packages encounter the problem of low computational efficiency. This paper reports our development on a GPU-based microscopic Monte Carlo simulation tool gMicroMC using advanced GPU-acceleration techniques. Methods gMicroMC simulated electron transport in the physical stage using an interaction-by-interaction scheme to calculate the initial events generating radicals in water. After the physicochemical stage, initial positions of all radicals were determined. Simulation of radicals' diffusion and reactions in the chemical stage was achieved using a step-by-step model using GPU-accelerated parallelization together with a GPU-enabled box-sorting algorithm to reduce the computations of searching for interaction pairs and therefore improve efficiency. A multi-scale DNA model of the whole lymphocyte cell nucleus containing ~6.2 Gbp of DNA was built. Results Accuracy of physical stage simulation was demonstrated by computing stopping power and track length. The results agreed with published data and the data produced by GEANT4-DNA (version 10.3.3) simulations with 10 -20% difference in most cases. Difference of yield values of major radiolytic species from GEANT4-DNA results was within 10%. We computed DNA damages caused by monoenergetic 662 keV photons, approximately representing 137 Cs decay. Single-strand break (SSB) and double-strand break (DSB) yields were 196 ± 8 SSB/Gy/Gbp and 7.3 ± 0.7 DSB/Gy/Gbp, respectively, which agreed with the result of 188 SSB/Gy/Gbp and 8.4 DSB/Gy/Gbp computed by Hsiao et al. Compared to computation using a single CPU, gMicroMC achieved a speedup factor of ~540x using an NVidia TITAN Xp GPU card. Conclusions The achieved accuracy and efficiency demonstrated that gMicroMC can facilitate research on microscopic radiation transport simulation and DNA damage calculation. gMicroMC is an open-source package available to the research community.