Electronic Stopping Power Values Research Articles

Carbon Elastic and Inelastic Stopping-Power Components for Heavy Ions at Bohr and Higher Velocities

Carbon stopping power (SP) data for heavy ions (HIs), obtained around Bohr velocities, revealed remarkably lower values than those predicted using the SRIM/TRIM calculations/simulations. An attempt was made to extract the elastic (collisional) and inelastic (electronic) components from the available SP data obtained in experiments. A problem is that essentially, total SP is measured in experiments, whereas electronic SP values, usually presented as the results, are derived via the subtraction of the calculated collisional component from the measured values. At high HI reduced velocities (V/v0)/ZHI2/3≳0.3 (V and v0 are HI and Bohr velocities, respectively, and ZHI is the HI atomic number), the collisional component can be neglected, whereas at Bohr velocities it becomes comparable to the electronic one. These circumstances were used to compare the experimental SP data with the SRIM/TRIM calculations/simulations and to empirically obtain corrections to the collisional and inelastic SP components.

Monte Carlo simulations of proton irradiation effects on PTFE, KEVLAR, EFTE, DYNEEMA, and NOMEX polymeric materials used in astronaut space suits

Astronauts suffer from natural space radiation as high-energetic protons, heavy ions, and secondary particles produced in collisions. Galactic cosmic rays and solar particle events are the basic parts of space radiation spectra. Wears and accessories designs for use by astronauts aim to minimize these deleterious effects of this environment. Polymeric materials are preferred in astronaut suits because they are lightweight, inexpensive, and durable. Teflon, KEVLAR, ethylene tetrafluoroethylene, DYNEEMA, and NOMEX polymeric astronaut wear materials were exposed to high energetic proton irradiations by the use of Monte Carlo simulation tools SRIM-2013 and FLUKA 2011.1. Proton energies are applied as 1, 2, and 3 GeV known as in order of space radiation magnitude. Besides, displacement per atom calculations were done and results were discussed in the plane of structural changes in the given polymeric materials. After interacting with protons with 1, 2, and 3 GeV energies, the material with the lowest Displacement per atom value among the five studied materials is DYNEEMA with values of 1.01E − 25, 9.96E − 26, and 1.00E − 25, respectively. Again, among the materials studied for these three proton energies, DYNEEMA has the highest electronic stopping power values are, respectively, 2.11E − 03, 2.10E − 03, and 2.31E − 03. DYNEEMA has the highest nuclear stopping power values as 2.23E − 07, 1.53E − 07, and 4.27E − 07, respectively.

A spatial and temporal characterisation of single proton acoustic waves in proton beam cancer therapy.

An in vivo range verification technology for proton beam cancer therapy, preferably in real-time and with submillimeter resolution, is desired to reduce the present uncertainty in dose localization. Acoustical imaging technologies exploiting possible local interactions between protons and microbubbles or nanodroplets might be an interesting option. Unfortunately, a theoretical model capable of characterising the acoustical field generated by an individual proton on nanometer and micrometer scales is still missing. In this work, such a model is presented. The proton acoustic field is generated by the adiabatic expansion of a region that is locally heated by a passing proton. To model the proton heat deposition, secondary electron production due to protons has been quantified using a semi-empirical model based on Rutherford's scattering theory, which reproduces experimentally obtained electronic stopping power values for protons in water within 10% over the full energy range. The electrons transfer energy into heat via electron-phonon coupling to atoms along the proton track. The resulting temperature increase is calculated using an inelastic thermal spike model. Heat deposition can be regarded as instantaneous, thus, stress confinement is ensured and acoustical initial conditions are set. The resulting thermoacoustic field in the nanometer and micrometer range from the single proton track is computed by solving the thermoacoustic wave equation using k-space Green's functions, yielding the characteristic amplitudes and frequencies present in the acoustic signal generated by a single proton in an aqueous medium. Wavefield expansion and asymptotic approximations are used to extend the spatial and temporal ranges of the proton acoustic field.

Electronic Stopping Powers of Formvar and Mylar Polymeric Materials for Heavy Ions: LSS Modified Theory and Monte Carlo Simulation

The stopping power of Formvar and Mylar polymeric materials for energy region (0.1 to 1.0) MeV/nucleon 19F, 23Na, 24Mg, 27Al, 28Si, 31P, 32S, 35Cl, and 40Ar ions have been determined. The energy loss and stopping power of Mylar were calculated for 11B having energies between 0.31 and 0.85 MeV/nucleon. In fact, the factor ξe and exponential function f(E) involved in Lindhard, Scharff, and Schiott (LSS) theory has been modified in light of the available simulation electronic stopping power values. The results obtained by the LSS modified theory and Monte Carlo simulations are compared with MSTAR, the SRIM predictions code, and experimental data. The obtained results show a close agreement qualitatively with MSTAR, experimental data, and those generated by the SRIM computer code.

Influence of temperature and electronic stopping power of UO2 irradiated with swift ions on Mo migration

Molybdenum migration was studied in polycrystalline UO2 pellets under irradiation with swift ions. 95Mo isotope was introduced in the samples by ion implantation at a maximum concentration of 0.8 at.%. Irradiation conditions were chosen in order to understand, from a fundamental point of view, the behaviour of Mo in nuclear fuel during reactor operation. In this paper, the effect of three electronic stopping power values (7, 15 and 30 keV.nm−1) were investigated at different temperatures (room temperature, 600 °C and 1000 °C). The Mo concentration profiles before and after irradiation were measured by SIMS (Secondary Ion Mass Spectrometry). Raman spectroscopy was used to probe the defect creation or annealing in the UO2 microstructure. It was evidenced that Mo is very stable in the UO2 matrix as it migrates only for irradiation conditions combining a Se value of 15 or 30 keV.nm−1 and a temperature value of 1000 °C.

Stopping power and range calculations in human tissues by using the Hartree-Fock-Roothaan wave functions

The object of this work is to present the consequences for the stopping power and range values of some human tissues at energies ranging from 1MeV to 1GeV and 1–500MeV, respectively. The considered human tissues are lung, intestine, skin, larynx, breast, bladder, prostate and ovary. In this work, the stopping power is calculated by considering the number of velocity-dependent effective charge and effective mean excitation energies of the target material. We used the Hartree-Fock-Roothaan (HFR) atomic wave function to determine the charge density and the continuous slowing down approximation (CSDA) method for the calculation of the proton range. Electronic stopping power values of tissues results have been compared with the ICRU 44, 46 reports, SRIM, Janni and CasP data over the percent error rate. Range values relate to tissues have compared the range results with the SRIM, FLUKA and Geant4 data. For electronic stopping power results, ICRU, SRIM and Janni's data indicated the best fit with our values at 1–50, 50–250MeV and 250MeV–1GeV, respectively. For range results, the best accordance with the calculated values have been found the SRIM data and the error level is less than 10% in proton therapy. However, greater 30% errors were observed in the 250MeV and over energies.

Spectroscopic study of chemical modifications induced by swift heavy ions on polymers: the contribution of the CIRIL Platform and the CIMAP Laboratory

This paper gathers results obtained on the chemical ageing of polymers, at the CIRIL platform, using Swift heavy ions (SHI) from the GANIL accelerator. Swift heavy ions induce high values of electronic stopping power or LET (Linear Energy Transfer) and deposit their energy in the polymer through electronic processes, in a few nanometer size cylinder centered on the ion path. This results in huge local doses and dose rates. Both defects created in the polymer chain and gas release were quantified using spectroscopic methods (FTIR and Residual gas analysis (RGA)). Defects created in polymers submitted to SHI can be separated in two main series: defects common to all ionizing radiations and defects specific to SHI. A common trend of the evolution of these defects, under inert environment, is the following: 1) for the first group of defects, in most of the polyolefins, there is a limited (if inexistent) effect of LET on the radiation chemical yield of creation at low doses. Among defects of this first series, the behavior of vinyl groups is particular, 2) LET effect on SHI specific defects (triple bonds and cumulenes) is tremendous. Triple bonds (alkynes, alkyl or aryl cyanates) are created after a LET threshold value, depending on the polymer chemical structure. The dose effect on macromolecular defects, under inert environment, is also presented. The study of the LET effect on gas release, in various polyolefines, gives an insight on the mechanism of bond cleavage in presence of high ionization and excitation densities. Finally, few results on radiation-induced oxidation are presented. Compared to low-ionizing radiations, oxidation is reduced and unsaturated bonds are created under SHI.

Electronic stopping powers for heavy ions in SiC and SiO2

Accurate information on electronic stopping power is fundamental for broad advances in materials science, electronic industry, space exploration, and sustainable energy technologies. In the case of slow heavy ions in light targets, current codes and models provide significantly inconsistent predictions, among which the Stopping and Range of Ions in Matter (SRIM) code is the most commonly used one. Experimental evidence, however, has demonstrated considerable errors in the predicted ion and damage profiles based on SRIM stopping powers. In this work, electronic stopping powers for Cl, Br, I, and Au ions are experimentally determined in two important functional materials, SiC and SiO2, based on a single ion technique, and new electronic stopping power values are derived over the energy regime from 0 to 15 MeV, where large deviations from the SRIM predictions are observed. As an experimental validation, Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) are utilized to measure the depth profiles of implanted Au ions in SiC for energies from 700 keV to 15 MeV. The measured ion distributions by both RBS and SIMS are considerably deeper than the SRIM predictions, but agree well with predictions based on our derived stopping powers.

Damage profiles and ion distribution in Pt-irradiated SiC

Single crystalline 6H-SiC samples were irradiated at 150K with 2MeV Pt ions. The local volume swelling was determined by electron energy loss spectroscopy (EELS), and a nearly sigmoidal dependence on irradiation dose is observed. The disorder profiles and ion distribution were determined by Rutherford backscattering spectrometry (RBS), transmission electron microscopy, and secondary ion mass spectrometry. Since the volume swelling reaches 12% over the damage region at high ion fluence, the effect of lattice expansion is considered and corrected for in the analysis of RBS spectra to obtain depth profiles. Projectile and damage profiles are estimated by SRIM (Stopping and Range of Ions in Matter). When compared with the measured profiles, the SRIM code predictions of ion distribution and the damage profiles are underestimated due to significant overestimation of the electronic stopping power for the slow heavy Pt ions. By utilizing the reciprocity method, which is based on the invariance of the inelastic energy loss in ion–solid collisions against interchange of projectile and target atom, a much lower electronic stopping power is deduced. A simple approach, based on reducing the density of SiC target in SRIM simulation, is proposed to compensate the overestimated SRIM electronic stopping power values, which results in improved agreement between predicted and measured damage profiles and ion ranges.

Molecular dynamics simulations of ion range profiles for heavy ions in light targets

The determination of stopping powers for slow heavy ions in targets containing light elements is important to accurately describe ion–solid interactions, evaluate ion irradiation effects and predict ion ranges for device fabrication and nuclear applications. Recently, discrepancies of up to 40% between the experimental results and SRIM (Stopping and Range of Ions in Matter) predictions of ion ranges for heavy ions with medium and low energies (<∼25keV/nucleon) in light elemental targets have been reported. The longer experimental ion ranges indicate that the stopping powers used in the SRIM code are overestimated. Here, a molecular dynamics simulation scheme is developed to calculate the ion ranges of heavy ions in light elemental targets. Electronic stopping powers generated from both a reciprocity approach and the SRIM code are used to investigate the influence of electronic stopping on ion range profiles. The ion range profiles for Au and Pb ions in SiC and Er ions in Si, with energies between 20 and 5250keV, are simulated. The simulation results show that the depth profiles of implanted ions are deeper and in better agreement with the experiments when using the electronic stopping power values derived from the reciprocity approach. These results indicate that the origin of the discrepancy in ion ranges between experimental results and SRIM predictions in the low energy region may be an overestimation of the electronic stopping powers used in SRIM.

Electronic stopping power of polymers for heavy ions in the ion energy domain of LSS theory

LSS based computed electronic stopping power values have been compared with the corresponding measured values in polymers for heavy ions with Z = 5–29, in the reduced ion velocity region, v red ≤ 1. Except for limited v red ∼ 0.6–0.85, the formulation generally shows significantly large deviations with the measured values. The ζ factor, which was approximated to be ∼ Z 1 1/6, involved in LSS theory has been suitably modified in the light of the available experimental stopping power data. The calculated stopping power values after incorporating modified ζ in LSS formula have been found to be in close agreement with measured values in various polymers in the reduced ion velocity range 0.35 ≤ v red ≤ 1.0.

실리콘에 고에너지 안티몬이온주입의 실험과 개선된 모델에 관한 연구

Antimony profiles by MeV implantation are measured by secondary ion mass spectrometry (SIMS) and spreading resistance (SR). The moments of SIMS and simulated profiles are calculated and compared for the exact range in MeV energy. SRIM, DUPEX, ICECREM, and TSUPREM4 simulation programs are used for the calculation of range 1D, 2D. SRIM is a Monte Carlo simulation program and different inter-atomic potentials can be used for the calculation of nuclear stopping power cross-section (Sn) and range moments. Nevertheless, the range parameters were not influenced from nuclear stopping power in MeV. Through the modification of electronic stopping power cross-section (Se), the results of simulation are remarkably improved and matched very well with SIMS data. The values of electronic stopping power are optimized for Sb high energy implantation. For the electrical activation, Sb implanted samples are annealed under <TEX>$N_2$</TEX> and <TEX>$O_2$</TEX> ambient. Finally, Oxidation retard diffusion(ORD) effect of Sb implanted sample are demonstrated by SR measurements and ICECREM simulation.

Neutral atom sputtering yields from Gd 3Ga 5O 12 and Y 3Fe 5O 12 garnets: Observation of a velocity effect

The effects of swift heavy ions in insulators, leading e.g. to the appearance of latent tracks, have been extensively studied. In particular, it has been shown that at a fixed value of electronic stopping power the damage cross-section in the yttrium iron garnet (Y 3Fe 5O 12) is larger for low energy ions than for high energy ions. This is the so-called “velocity effect” in the damage creation in the electronic stopping power regime. In order to verify if such a velocity effect also exists for atoms sputtering, the total sputtering yields of yttrium iron garnet (Y 3Fe 5O 12) and gadolinium gallium garnet (Gd 3Ga 5O 12) irradiated at high energy with a lead beam of 19.3 MeV/u, were measured using the catcher technique. The sputtered particles, were collected upon an aluminum foil placed in front of the target and the impurities deposited on the collectors were analysed by Rutherford backscattering. By comparison with previous measurements of the sputtering yield for the same electronic energy loss value at lower velocity, we clearly observed an important velocity effect: the sputtering yield is higher at low velocity than at high velocity.

Sputtering of vitreous SiO2 and Y3Fe5O12 in the electronic stopping power region: A thermal spike description

The thermal spike model was applied to calculate track radii versus electronic stopping power for different beam energies using only one fitting parameter, λ the mean diffusion length of the energy deposited on the electrons by the slowing down of a swift heavy ion in vitreous silica a-SiO2. A λ value of 2.5±0.2 nm is extracted by fitting all the different results of damage creation taking into account a velocity effect. Using the same value of λ the energy necessary to vaporize the vitreous silica is reached for a value of electronic stopping power dE/dx, which corresponds to the appearance of a huge sputtering of silicon in SiO2. So in the thermal spike model one can explain two phenomena with the same value of the free parameter λ. The present paper aims at extending this model to the yttrium iron garnet Y3Fe5O12, abbreviated as YIG. By fitting the latent track radii one can extract the unique following values: λ=5.0±0.3 nm and a latent heat of fusion LH=300±100 J g−1. Then the energy value Lv of 2.2±0.4 eV/atom necessary to sputter this material is extracted. The evolution of sputtering yield versus the electronic stopping power is in good agreement with the experimental results.

Infrared spectrometry observations of SiO2films irradiated by high energy heavy ions

Abstract Thermally-grown silicon dioxide (SiO2) layers have been irradiated at room temperature by high energy, O, Ni and Xe ions with doses up to 1014 ions/cm2. These experiments allow to cover a wide range of electronic stopping power values (from 2 to 60 MeV.cm2/mg). The infrared (IR) absorption spectrometry has been used to evaluate the changes in the atomic arrangement of the SiO4 tetrahedra and to determine the damage production cross section A and the track radii in the amorphous SiO2 films as a function of the electronic stopping power.

High energy ion irradiation of germanium

Irradiations of n- and p-doped germanium samples have been performed at room temperature at GANIL (Caen) using Ar (1415 MeV), Xe (5510 MeV and 751 MeV), Ca (272 MeV), Zn (691 MeV), O (195 MeV) and Kr (427 MeV) ions. The sample resistance and Hall mobility were measured in situ as a function of the ion fluence. In p-Ge samples the conductivity and the majority carrier density steadily increase up to the maximum fluences used (about 10 12 cm −2). The conductivity σ of n-Ge samples first decreases, reaches a minimum at a fluence depending on the initial doping concentration and then increases. At the minimum value of σ, Hall measurements show a transition from n- to p-type conductivity. These results show that acceptor energy levels are created by irradiation induced defects. At low electronic stopping power values, the creation rate of acceptor levels is approximately a linear function of the calculated number of displacements per atom. This linear dependence becomes invalid at high electronic stopping power values. This last result could be explained by assuming a partial annealing of the defects for the largest electronic stopping power.

Saturation in the damage efficiency in magnetic insulators irradiated by high energy heavy ions

Abstract Magnetic garnet Y3Fe5O12 and magnetic ferrite BaFe12O19 have been irradiated at room temperature by Kr and Xe ions using the GANIL accelerator at Caen and by U ions using the Unilac accelerator at Darmstadt. These experiments allow to cover a wide range of electronic stopping power values (between 7 MeV/μm and 45 MeV/μm) using the ion beam at energy between 40 MeV/a.m.u. and 8 MeV/a.m.u. Transmission Mossbauer spectrometry has been used to determine the damage cross section A for the corresponding value of electronic stopping power. High resolution electron microscopy observations confirm the A determination for the highest value of dE/dx. The main feature is the appearance of a saturation in the damage efficiency e = A/dE/dx above an electronic stoping power value T M . Using all the previous results, damage evolution and damage morphology description will be proposed and comparison with the chemical etching sensitivity of the magnetic garnet will be done.

Calculation of H+-ranges and H+-range stragglings in the energy region 1–1000 keV

Abstract The use of various approximations in calculating proton projected ranges has been studied by the analytical and the Monte Carlo methods. A correction is presented for the projected ranges given in the compilation (Andersen and Ziegler: Hydrogen Stopping Powers and Ranges in All Elements). The greatest correction factors at 1, 10, 100 and 1000 keV are 3.5, 2.1, 1.4 and 1.2, respectively. The corrections result from the inclusion of the tabulated electronic stopping power values in the calculation of the projected range to the total range ratio and from the estimation of the effect of the reflection. The Monte Carlo calculations show the electronic straggling to be a remarkable factor in the width of the proton range distributions at reduced energies larger than of the order of 100.

Trapping of nitrogen in Mo due to defects generated by 50-400-keVH+andHe+ions

The trapping property of nitrogen diffusing in polycrystalline molybdenum has been used to study the distribution of defects generated by 50-400-keV ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ bombardment. The nitrogen-implanted samples were annealed at $T=600 \mathrm{and} 750\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. The defect concentrations were studied with different ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ doses ranging from ${10}^{14}$ to ${10}^{18}$ ions/${\mathrm{cm}}^{2}$. Increasing the ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ prebombardment doses led to a strong increase in the trapping of nitrogen and to the rapid migration of nitrogen atoms to the damaged region before trapping. The nitrogen defect trapping was observed to be very steady. The depth distributions of trapped nitrogen were measured with the ($p,\ensuremath{\gamma}$) resonance-broadening method. The theoretical defect distributions were calculated using Monte Carlo calculations along with the tabulated electronic stopping-power values and good agreement was found between the theoretical and experimental defect profiles. The modal ranges of the 50-400-keV ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ ions in Mo derived as indirect by-products of the defect measurements agree with the values obtained through the Monte Carlo calculations, where the tabulated data for electronic stopping is employed, but are 20-40% shorter than those where the electronic stopping according to the theory of Lindhard, Scharff, and Schi\o{}tt is used.

Channeling and dechanneling of ion-implanted phosphorus in silicon

Profiles of channeled and dechanneled 31P ions in the energy range 30–900 keV have been measured in 〈100〉, 〈111〉, 〈112〉, and 〈110〉 Si. The maximum range, Rmax, of the channeled ions has been determined and used to calculate values of electronic stopping power. The variation of these values with substrate orientation agrees qualitatively with that predicted by the Firsov theory, although the actual values are 2–3 times the Firsov prediction. Dechanneled profiles (450 keV) were measured in 0.3° steps up to 1.2° for all four orientations and in 2° steps up to 10° for the 〈100〉 and 〈111〉 orientations. The effect of tilt direction on the dechanneling was studied. Dechanneling from the 〈111〉, 〈112〉, and 〈110〉 orientations exhibited a marked sensitivity to the direction of tilt. By tilting in an appropriate maximum-dechanneling direction, dechanneling from the 〈100〉 and 〈111〉 orientations was found to be continuous, starting with the 0.3° tilt and saturating for tilts above 4.2°. The projected range, Rp, determined from the fully dechanneled or random distributions, was found to vary almost linearly with energy and has a slope of ∼1.1 μm/MeV.