Langevin Simulation of Rf Corona Discharges for Space Hardware

The corona effect in space radio frequency (RF) hardware is an electric breakdown process at low neutral gas pressures originated by the progressive outgassing of the entire RF system. A small number of seeding electrons are accelerated by the RF electric field and their subsequent inelastic collisions with neutral atoms and ionizations produce the multiplication of charges in the gap between the conducting walls of the RF system. The simulation of the early stages of the corona effect is performed through the numerical integration of the individual trajectories of the electrons in a simplified model of a waveguide made of infinite parallel metallic walls. The electron dynamics is described by dimensionless Langevin equations, where the RF field is the deterministic driving force and an additional stochastic force term describes the interaction between the electrons and the neutral gas background. The charge multiplication process is caused by the electron impact ionization of the neutral atoms and the secondary electron emission at the walls of the waveguide. The physical properties of different materials for the walls of the waveguide are also taken into account. We present the basis of the model and the characteristics of the numerical integration scheme, as well as the physical conditions under which charge multiplication develops. The limitations of the proposed model, as well as the current limitations in the available experimental data, are also discussed.