The results of calculating the energy spectra of protons transmitted and reflected from thin layers of gold are presented. The simulation results are compared with experimental data. It is shown that the stopping measurement results are affected by such factors as the multiple scattering, the geometry of the experiment, and the morphology and roughness of the target. An analysis of the angular dependence for particles passing through a thin film makes it possible to obtain information about the interaction potential between a particle and a solid. The obtained results on the potential agree with the data from experiments on the reflection of particles from the surface of a solid and differ markedly from the data on the potential determined from the scattering of particles in the gas phase. Keywords: energy spectra, angular distribution, interatomic interaction potentials, electronic stopping, straggling.
An overview of results concerning simulation of various processes which occur due to atomic bombardment of crystalline and amorphous solids is presented. With the use of original computational codes, the following data were obtained: reflection coefficients, projected energy losses and ranges of ions in solids, channeling data as well as sputtering yield and its dependence on incident angle of bombarding particles for Be-W and Ne-W combinations. Be, C and W targets were studied as these are among the plasma-facing materials in tokamaks, including ITER. The emphasis was made on atom-target combinations which lack reliable experimental data. Experimental data on other materials were used to verify calculations. A significant influence of the interaction potential used on the simulation results is shown. The reviewed results are tied by a common subject a study of interaction of plasma ions and first-wall materials of a tokamak-reactor and also by a common method of study the use of an original computational code. Keywords: scattering, ion sputtering, interaction potential, energy release.
The values of the atomic particle-solid potential were obtained for the first time from experimental data on the energy spectra and angular dependences of backscattered particles. The proposed procedure for determining the potential has never been applied previously. It is shown that the obtained data do not depend on the potential approximation used. The ion-solid interaction potential differs markedly from the potential describing collisions in the gas phase. The screening constant increases by 10-15%. The increase in screening is due to an increase in the density of the electron gas in the region between the incident particle and scattering center. Keywords: interatomic interaction potential, energy spectra, scattering of atomic particles on the surface.
The paper reports the calculation of the probabilities of Auger transitions taking place in the process of filling a vacancy on the 2pπ-orbital in an Ne+-Ne quasimolecule, a short-lived system which arises when the ion and atom approach each other and decays when they fly apart. Calculations for various ionization degrees of the quasimolecule particles were performed for the first time. It was found out that the system ionization degree increases very significantly (from 2 to 6) with increasing collision energy and decreasing distance of the particles closest approach. Using of the quantum mechanical approach and taking into account the collision dynamics made it possible to quantitatively describe for the first time the experimental Auger electron spectra of a complex many-electron quasimolecule. The contribution of the transition from the initial 3dπ-3dπ state to the 2pπ orbital was shown to be predominant among the whole variety of possible Auger decay channels. Keywords: atomic collisions, quasimolecule, Auger transitions, electron emission cross sections, vacancy decay
The results of modeling the sputtering coefficients of polycrystalline beryllium by hydrogen isotopes in the range of collision energies of 8 eV-100 keV and their dependences on the angle of incidence of the beam on the surface are presented. This data is necessary for estimating the sputtering of the first wall in the ITER tokamak made from beryllium. A strong surface shape influence on obtained results is shown. The limiting cases of a flat potential barrier (smooth surface) and a spherical potential barrier (a surface consisting of spikes) are considered. The effect of collision cascades on the sputtering coefficient has been established. The dependences of the average depth of sputtered particle formation on the bombarding particles energy are obtained for various angles of beam incidence on the target. The energy spectra and angular dependences of the ejection of sputtered particles are calculated for different energies of bombarding beam atoms. It is shown that the presence of an attractive well in the potential of an incident particle surface changes the sputtering coefficient dependence on incidence angle at small glancing angles. Keywords: Sputtering coefficients, energy and angular distributions of sputtered particles, interatomic potential, hydrogen isotopes, beryllium.
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