Monte Carlo simulation of the breakdown in copper vapour at low pressure

The breakdown conditions of copper vapour at low pressure are studied in a Monte Carlo simulation of electrons, copper ions and fast copper atoms. This is of interest for the dielectric breakdown strength of a vacuum interrupter after current zero, where hot vapour is still emitted from the electrodes. A one-dimensional model with given voltage drops in the kV range is applied to study the charge carrier multiplication in the gap. Initiated by the thermionic emission the electron impact ionization of copper atoms produces singly as well as twofold charged ions and causes electron avalanches. The simulation allows studying detailed energy distributions of electrons, ions and fast atoms across the gap. By scanning a large range of gas densities and electric voltages, the boundary of the breakdown region has been determined.