Energy Loss Of Light Ions Research Articles

Theoretical Study of Alpha Particles Energy loss in essential elements of Human Bones

Energy loss of light ions, such as alpha particles, has measured in human Bones with a different energy, are very important and very useful especially in nuclear therapy and radiation protection. Using SRIM Computer Programs to calculate the stopping power in bones by considering the tissue mostly composed of 7 elements, the alpha stopping powers and Range were calculated for those elements with the energy interval (0.1–4.5) MeV. In addition, the Results of stopping power for alpha in Bones tissues are presented and compared with the latest published data.

Predictions for the energy loss of light ions in laser-generated plasmas at low and medium velocities.

The energy loss of light ions in dense plasmas is investigated with special focus on low to medium projectile energies, i.e., at velocities where the maximum of the stopping power occurs. In this region, exceptionally large theoretical uncertainties remain and no conclusive experimental data are available. We perform simulations of beam-plasma configurations well suited for an experimental test of ion energy loss in highly ionized, laser-generated carbon plasmas. The plasma parameters are extracted from two-dimensional hydrodynamic simulations, and a Monte Carlo calculation of the charge-state distribution of the projectile ion beam determines the dynamics of the ion charge state over the whole plasma profile. We show that the discrepancies in the energy loss predicted by different theoretical models are as high as 20-30%, making these theories well distinguishable in suitable experiments.

Inelastic energy loss of medium energy H and He ions in Au and Pt: Deviations from velocity proportionality

Electronic energy loss of light ions in nm films of Au and Pt has been studied at keV ion energies. For H the electronic stopping power $S$ is found to exhibit the expected velocity proportionality at low ion velocities, which confirms the anticipated excitation mechanisms responsible for the energy transfer between ions and the electrons in the solid. In contrast, for He, $S$ shows a clear deviation from velocity proportionality for both materials at ion velocities below 0.8 atomic units, i.e., 64 keV. This result indicates a change in the interaction mechanisms active at the investigated ion velocities, which cannot exclusively be interpreted from the density of states of the target. Instead, the more complex electronic structure of the He ion enables an additional energy loss channel due to charge exchange by atomic level promotion. Associated energy losses together with a changed equilibrium charge state permit an explanation of the observed phenomenon.

Electronic Excitations of Slow Ions in a Free Electron Gas Metal: Evidence for Charge Exchange Effects

Electronic energy loss of light ions transmitted through nanometer films of Al has been studied at very low ion velocities. For hydrogen, the electronic stopping power S is found to be perfectly proportional to velocity, as expected for a free electron gas. For He, the same is anticipated, but S shows a transition between two distinct regimes, in both of which S is velocity proportional-however, with remarkably different slopes. This finding can be explained as a consequence of charge exchange in close encounters between He and Al atoms, which represents an additional energy loss channel.

Energy loss of light ions in different carbon compounds

Experimental data on the energy loss of light H, Li, B, and N ions in methane and H and N ions in benzene vapor have been presented for the range of ion energies from 0.01 to 0.6 MeV/nucleon. It has been shown that the energy loss in the compounds does not follow the addition rule for small ion energies, which indicates the necessity of taking into account the chemical bonds of the molecular targets. The deviation from the addition rule has been experimentally found to increase with the nuclear charge of the projectile ion.

Vanishing Electronic Energy Loss of Very Slow Light Ions in Insulators with Large Band Gaps

Electronic energy loss of light ions in nanometer films of materials with large band gaps has been studied for very low velocities. For LiF, a threshold velocity is observed at 0.1 a.u. (250 eV/u), below which the ions move without transferring energy to the electronic system. For KCl, a lower (extrapolated) threshold velocity is found, identical for H and He ions. For SiO2, no clear velocity threshold is observed for He particles. For protons and deuterons, electronic stopping is found to perfectly fulfill velocity scaling, as expected for binary ion-electron interaction.

Energy loss of light ions in polypropylene absorber foils

The energy loss of Li, C and O ions in polypropylene absorber foils has been measured using 15 UD Pelletron Accelerator facility at Inter University Accelerator Centre (IUAC), New Delhi, India. The actual experiment has been performed in low flux chamber attached to the General Purpose Scattering Chamber (GPSC). These experimental energy loss values have been compared with the computed values based on various empirical/semi-empirical formulations. Some interesting trends have been observed.

Energy loss of light ions with allowance for the presence of metastable particles in the ion beam

The change in the average ion charge due to the presence of particles in metastable states in beams of helium-like ions has been studied. The charge distributions and average charges have been calculated for ions with nuclear charges Z = 3−7 and a velocity of 3.65 au in nitrogen. The previously obtained data on the cross sections of loss and capture of electrons by metastable ions and ions in the ground state were used in the calculations. It is shown that the presence of metastable particles in ion beams leads to an increase in the average charge and energy loss for all considered ions.

Energy loss and multiple scattering of light ions in dense and strongly magnetized plasma

The alpha particles produced in inertial fusion reactions are less energetic than (or of the order of) a MeV/amu. The surrounding electronic plasma has a thermal velocity from 0.1 to 10 keV, while Deuterium–Tritium thermal velocity remains usually lower. Then the velocity scale of the different actors is the following one: V thi ⪡ V p < V the , ( V thi and V the being, respectively, the plasma ion and electron thermal velocities, and V p the alpha projectile velocity). In this low projectile velocity regime, we are investigating the influence of a strong external magnetic field on the energy loss of light ions. A brief review of different theoretical approaches results is presented first. Then we study a diffusion coefficient, transverse to the external magnetic field, of a light ion in an electron plasma target to characterize the B-dependence of this diffusion and consequently the energy loss. Finally, we look at the multiple scattering of a light ion by an electron plasma target and how the magnetic field could affect the projectile penetration depth.

Dependence of the etch rate ratio on the energy loss of light ions in CR-39

Mathematical simulation of the etch pit evolution requires the knowledge of the relationship between the etch rate ratio and the restricted energy loss of charged particles. Whereas a unique correlation of both quantities independent of the kind of particle and its initial energy was found for protons, deuterons and alpha particles the results of the depth-dependent track etch rates for 7 Li , 11 B and 12 C ions indicated a different behaviour for heavier ions. A detailed analysis of the etch rate ratio in dependence on the restricted energy loss confirmed the existence of specific relationships for ions of different kind and initial energy. The spread of the corresponding curves is explained by the gradual increase of the track etch rate over a certain distance from the detector surface. The speed of this increase is the higher the lower the restricted energy loss is.

Ion-beam-induced reconstruction of amorphous GaN

Wurtzite GaN can be rendered amorphous by high-dose heavy-ion bombardment. We show here that relatively low-dose reirradiation of such amorphous GaN (a-GaN) with MeV light ions can significantly change some of the physical properties of a-GaN. In particular, light-ion reirradiation of a-GaN results in (i) an increase in material density, (ii) the suppression of complete decomposition during postimplantation annealing, (iii) a significant increase in the values of hardness and Young's modulus, and (iv) an apparent decrease in the absorption of visible light. Transmission electronmicroscopy shows that a-GaN remains completely amorphous after light-ion reirradiation. Therefore, we attribute the above effects of light-ion reirradiation to an ion-beam-induced atomic-level reconstruction of the amorphous phase. Results indicate that electronic energy loss of light ions is responsible for the changes in the mechanical properties and for the suppression of thermally induced decomposition of a-GaN. However, the changes in the density of a-GaN appear to be controlled by the nuclear energy loss of light ions.

Angular dependence of the energy loss of ions in solids: Computer simulations and analysis of models

The angular dependence of the electronic energy loss of light ions in solids is analyzed in the frame of the binary collision approximation (BCA) using an analytical formalism based on multiple scattering (MS) functions, as well as with Monte Carlo (MC) simulations. These simulations have been performed for different collisional models of ions in the solid. A variation of the mean number of collisions with the observation angle is found, for a frequently used random distribution of interatomic distances, which may originate an angular dependence of the energy loss. Additionally the effect of impact parameter restrictions has been investigated, and again a change in the mean number of collisions with the observation angle has been observed. As this variation depends on the model of the solid and the impact parameter criteria applied, uncertainties in the single collision energy loss appear.

Determination of the electronic energy loss of light ions in a silicon lattice by using the transmission ion channeling method

Charged particle activation analysis (CPAA) is able to analyze light elements such as carbon and oxygen at trace levels in semiconductor materials. This technique requires the knowledge of the stopping powers of these materials for channeled ions. The electronic energy loss for ions entering the crystal lattice in a random direction is well established. The electronic energy losses for protons, deuterons, 3He + and 4He + ions entering a 3.6 μm thick silicon single crystal along the 〈1 0 0〉 direction were measured by using the transmission of particles technique. Data obtained were compared with those obtained by other authors using theoretical and experimental methods.

Energy loss of light ions scattered off Al(110) single crystal surfaces at low energy

We present energy loss data taken after grazing incidence scattering of H +, H 0, He 2+, He +, and He 0 off an Al(110) surface. The data is evaluated by means of a procedure that allows to extract surface electron density parameters. The obtained density parameters will be compared to those obtained from a potassium target. The advantage of using Al and K is that both can be described by a jellium model. In order to extract the electron density parameters we employ a method based on a description of the interaction via the force of friction. We find that the experimental data cannot be fitted using calculated bulk friction coefficients. Thus we suggest that the friction of light ions is different at the surface and in the bulk.

Investigation of the electronic energy loss of light ions for materials analysis

The energy loss, straggling and multiple scattering of light ions in materials was investigated. The interaction of charged particles with crystalline materials was calculated on the basis of Lindhard's dielectric response function. The contribution of local and global electronic excitation was taken into account. Simulations and experimental results of other authors in random and low indexed crystal directions are compared with the model calculations.

Dependence of electronic energy loss of light ions on the angle of emergence

The emergence angle dependence of electronic energy loss for energetic light ions transmitted through thin foils is discussed. The connection between this dependence and the impact parameter dependence of energy loss (differential stopping) is considered. Charge asymmetry effects in the differential stopping are examined and the possibility of studying the proton-antiproton transmission through thin foils is discussed. Several aspects of the stopping of light ions carrying their own electrons, including screening effects and charge exchange processes, are considered.

Charge state dependent energy loss of light ions

Energy loss measurements for individual charge states of high energy light ions are expected to give us an important clue to investigate some basic physics behind the stopping process, which we cannot obtain from total energy loss measurements. An overview of experimental works concerning the charge state dependent energy loss is presented.

Impact parameter dependence of light-ion electronic energy loss

We have calculated the dependence of the mean electronic energy loss of light ions on impact parameter by use of the harmonic-oscillator model of atomic stopping. Results are reported for protons incident on atomic hydrogen, helium, neon, and argon at velocities v $ ̆ v o . Considerable care has been taken in selecting proper sets of dipole oscillator strengths to characterize the ensemble of harmonic oscillators. The energy transfer to an individual oscillator is known from our previous work to the three leading orders in the Bom series. Mainly first-order results have been analysed. We find a quasi-Guassian behavior at small impact parameters and a nearly exponential tail at larger impact parameters. The latter approaches Bloch's dipole limit which is asymptotically exact. A single-oscillator model is included in the comparison and turns out to be inadequate in all cases except for high-speed protons incident on hydrogen. Part of our results can be compared with those of Kabachnik et al. The overall agreement is reasonable, but discrepancies of up to a factor of 2 have been found. For atomic hydrogen, these inaccuracies are asserted to originate in their numerical procedure.

Energy loss of light ions and neutrals from surface scattering

The energy spectra of He scattered at grazing incidence from a clean metal surface are measured by a time-of-flight method. The results are interpreted in terms of the dielectric response function of the metal. It is shown that surface effects and straggling have a major influence in the energy range under consideration (1–10 keV). There is also a basic connection between energy loss and charge state, such that these phenomena must be dealt with by the same formalism. It is shown that Auger neutralization is the dominating process and hence the energy loss depends on how long the incoming particle interacts with the surface as an ion or as a neutral.

Dependence of energy loss of light ions in Au on scattering angle and target thickness in the energy interval 25 to 500 keV/amu

The integral energy losses of H +, He + and He 2+ ions in thin gold foils at incident energies 40 to 500 keV have been determined experimentally. Pre-equilibrium stopping in the near-surface metal layers is found. Measurements of the energy loss straggling of protons in Au in the 9–45 nm thickness range are also been made. The straggling data are compard with the theories. The experimental angular dependence of the energy loss for protons are compared with the results of a Monte Carlo simulation of particle penetration through a foil.