Electrostatic analysis of triggered spark gaps

One of the major considerations associated with the overall performance of a high pressure trigatron is that of lifetime and this becomes particularly important for high repetition rate pulsed power applications. The problems associated with short trigatron lifetimes are usually related to the erosion of the trigger pin due to successive arcing. Although the erosion per pulse will be dependent upon the specific operating conditions it will eventually lead to an insufficient level of field distortion in the main electrode gas region when triggered, resulting in poor switch performance. In order to maximise the lifetime of a trigatron switch whilst still maintaining good switching performance, an experimental programme was undertaken in which the preliminary design of the trigatron was determined through electrostatic field modelling. 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. The final trigatron design also contains a small corona discharge cell which generates a negative ion population in the gas, which is SF₆. This ensures initiatory electron production through ion detachment resulting in sub-nanosecond jitter. In order to spatially optimise the overall switch design, electrostatic field analysis has been applied to all regions of gaseous and solid insulation in the switch