Numerical simulation of secondary electron emission charging at insulator surfaces

The charging process of insulator surfaces in vacuum at HV due to secondary electron emission has been calculated using numerical simulation. The systems considered consist of two electrodes at a HV difference, separated by a glass plate or a hollow glass channel. The simulations give insight into the critical HV positions and into the influence of the geometry, the initial voltage distribution and the material properties on the charging profiles and the leakage current paths. A HV performance increase of these systems can be obtained by decreasing the impact of free electrons, adding a coating on all insulating surfaces which have a high value of E/sub 1/ (i.e. the first crossover point of the secondary electron yield curve) and/or are weakly conductive, and breaking up the total voltage difference in smaller parts by adding electrodes to all surfaces at intermediate voltages.