## Modelling of singly charged ion-atom collisions in fusion plasma

##### Dátum

##### Szerzők

##### Folyóirat címe

##### Folyóirat ISSN

##### Kötet címe (évfolyam száma)

##### Kiadó

##### Absztrakt

The inelastic electron processes in ion-atom collisions have great significance in many fields of science, such as particle beam therapy and fusion plasma physics. Among electron processes, ionisation has a great influence in radiation physics, atomic and molecular structure exploration, and modelling and diagnosing the magnetically confined fusion plasmas in tokamak reactors. The dissertation focuses on the collision of singly charged ions with neutral atomic impurities in plasma. The collision systems studied in the dissertation are composed of projectiles of proton, lithium, and sodium ions and atomic targets of nitrogen and noble gases, i.e. He, Ne, Ar, Kr and Xe. Studying the cross sections of these collision systems is essential due to their potential applications in the diagnostic of magnetically confined fusion plasmas. During my PhD studies I used the 3-body Classical Trajectory Monte Carlo (CTMC) method, following its historical development from collinear molecular reactions to its adaptation for ion-atom collisions. The 3-body CTMC approach, a non-perturbative computational technique, is developed for a comprehensive understanding of collision dynamics. Within our CTMC model, the collision system is reduced to a three-body problem by employing the single active electron (SAE) approximation. I presented a discussion of the Garvey-type distance-dependent model potential based on Green et al.'s work, the Hamiltonian of the collision system, and equations of motion. The initial conditions of the projectile and the active electron of the target are determined according to the Reinhold and Falcon's methodology. The cross-section calculations include total cross-sections of electron capture and ionisation channels, as well as the differential cross-sections for ionisation channel. I provided an extensive discussion of nuclear-nuclear interactions, shell contributions, and the impact parameter probabilities of ionisation and charge exchange channels. For instance, the role of nuclear-nuclear interaction (VTP, see Figure 2.1) in {Li}^+-He collision is examined, providing that the cross section change is hardly visible with and without taken into account this interaction. The contribution of inner electron shells in H^+-Xe collisions is analysed, showing distinct patterns for various electron shells. Moreover, it shows insignificance of the contribution of most of the shells. Probabilities of ionisation and electron capture are investigated, exhibiting Gaussian-like shapes with shifting peak positions concerning impact energy. I performed CTMC calculations of {Li}^+-He and {Li}^+-N collision systems. I calculated the ionization and electron capture total cross sections as a function of the impact energy in the range (20 keV-100 MeV), I also determined the impact parameter dependent probabilities. I found excellent agreement with the previous data. I performed CTMC calculations of {Na}^+-N collision systems. I calculated the ionisation total cross sections as a function of the projectile energy in the range between 10 keV and10 MeV. The calculations showed the insignificance contribution of inner shell at low energies, and how they become more important as the impact energy increases. Moreover, I calculated the ionisation differential cross sections for impact energies of 30, 40, 50 and 60 keV as a function of the scattering angle and the energy of the ionised electron, these energies are in the suitable range for diagnosis plasma in tokamak. Furthermore, contour plots of double differential cross sections (DDCS) reveal distinct patterns at different impact energies and scattering angles, with a noticeable Fermi shuttle-type ionization process. This study focuses on the role of the impact energy on the differential cross section for the same system. I found that the majority of electrons are ejected at lower angles followed by backscattered electrons, moreover, the majority of these electrons acquire kinetic energies of 20 eV and below. I studied the collision of singly charged sodium (Na+) with atomic noble gases i.e., neon, argon, krypton, and xenon. I performed calculations of the ionisation and electron capture total cross sections as a function of the projectile energy in the energy range between 10 keV and 50 MeV. Moreover, I calculated the ionisation differential cross sections for impact energy of 60 keV as a function of the scattering angle and the energy of the ionised electron. An extensive discussion is provided for these collision systems. This study focuses on the role of the type of the target on the differential cross section at the same impact energy. I found that electrons with energies below 10 eV are dominant in the forward scattering. Moreover, for 12 eV electrons, the DDCSs of backscattering and scattering at 90° show relatively identical results. I found that the backscattering DDCS was greater than the scattering DDCS at 90° for both Ne(2p) and Ar(3p) at electron energies larger than 12 eV. Furthermore, I found that the backscattering DDCS for Kr(4p) and Xe(5p) was greater than at scattering of 90° with energies larger than 50 eV. I studied the collision of protons with noble gases i.e., neon, argon, krypton, and xenon. I performed calculations of the ionisation and electron capture total cross sections as a function of the projectile energy in the range (0.2 keV-50 MeV). Moreover, I calculated the ionisation differential cross sections for impact energy 35 of keV as a function of the scattering angle and the energy of the ionised electron. In comparing with experimental and theoretical data, I found excellent agreement regarding the total cross section data.