Electrostatic modelling of a trigatron spark gap

This paper describes the electrostatic modelling procedures which were undertaken in the design and evaluation of a long lifetime, low jitter, high voltage trigatron spark gap. The parameters studied were the trigger pin diameter, the proximity of this pin to the adjacent earthed electrode, the earthed electrode profile, the high voltage electrode profile and the position of the trigger pin. By employing electrostatic field modelling techniques, the level of field distortion present in the trigatron has been evaluated as a function of the trigger pin dimensions and position. This has allowed the operating lifetime of the spark gap to be predicted by considering the range of trigger pin positions which would result in an acceptable level of field enhancement. Electrostatic profiling of the adjacent conductors and insulators has also been carried out, resulting in an overall switch design with optimised performance and minimal volume. The above procedure has led to the production and testing of a 500 kV triggered switch which has been operated successfully with a sub-nanosecond jitter and relatively long lifetime.