Monte Carlo simulation of charged particle interactions*

The effect of electron-electron and electron-ion collisions on the kinetics of an electron swarm is challenging to study due to the long-range character of these interactions, which makes them fundamentally different from electron-neutral collisions. In this work, we include Coulomb collisions in the Monte Carlo solver LoKI-MC. These interactions are implemented either using the well-known null collision method or Nanbu's method for cumulative small-angle collisions. The accuracy of both methods is analysed by comparison with theoretical results and those obtained from the two-term solvers LoKI-B and Bolsig+.

Moreover, we study the effect of Coulomb collisions on the electron energy distribution function and transport coefficients in real and model gases, such as argon, oxygen and the Reid-ramp gas, under constant electric fields. We also examine their effect on the relaxation of electron swarms after electric-field pulses, which is often neglected but can be important in gases with low collisional rates, such as argon.