MINEA, TiberiuSCHIESKO, LoïcALHARBI, Abdulrahman Saad2026-03-1720252025UPASP173https://hdl.handle.net/20.500.14154/78464This thesis investigates collisional and quantum effects in plasmas under conditions encountered in magnetic confinement fusion devices. Resonant charge-exchange collisions are first analyzed through a collision operator constructed from the Boltzmann equation, which shows that the charge-exchange mean free path acts as a characteristic length scale modifying ion dynamics and dispersion and predicts conditions where coupling to the field drives an instability. The second class of collisions examined is Coulomb collisions, for which the analysis centers on the Coulomb singularity problem. The divergence of the momentum transfer cross section in classical scattering theory is revisited, and the ad hoc introduction of a minimum cutoff through large-angle scattering is examined. At high temperatures, it is shown within the Born approximation that the minimum cutoff becomes the de Broglie wavelength, which yields a modified Coulomb logarithm derived without heuristic assumptions. Because the separation of scales between classical and quantum minimum cutoffs introduces a temperature constraint in which the de Broglie wavelength has a physical meaning microscopically, a quantum kinetic description is developed to investigate this high-temperature regime from a fully quantum perspective. The N-body Schrödinger equation is reduced under the weak-coupling approximation and reformulated in phase space using the Wigner formalism, with the resulting single-particle kinetic equation closed self-consistently with the Poisson equation, yielding a mean-field model to investigate the collective electronic response at short range. Its application reveals a high-temperature quantum regime from which a short-range potential incorporating quantum screening and diffraction emerges. The short-range potential alters electron-electron and electron-ion scattering, and under temperatures relevant for tokamaks, leads to a differential cross section that departs from the Rutherford form. The corresponding momentum transfer cross section and Coulomb logarithm are revisited in light of these findings. The thesis thereby develops a theoretical description of collisional and quantum effects across plasma conditions, encompassing classical resonant charge exchange in partially ionized regimes and the quantum treatment of Coulomb interactions in high-temperature fully ionized regimes.135enplasma physicsmagnetic fusioncollisionsquantum effectsmany-body problemThesis