Investigation of numerical thermalization in particle-in-cell simulations

Particle-in-cell (PIC) is a widely used method for plasma modelling. Like any other method it represents only an approximation to real plasma. This fact implies the possibility for development of some parasitic effects in the simulation. It is very important to know the nature of these effects and how they affect the simulation. In this article we investigate one of them known as numerical thermalization (maxwellization) which means the artificial increased rate in which the velocity distribution function of particles relaxes toward Maxwellian. We used a Id model of homogenous plasma to measure how the thermalization time is affected by number of particles per Debye length ND. Recently some works show that explicit introduction of collisions to PIC method may have negative side-effects to the simulation, so we have also studied this phenomena