The suitability of N2 to replace SF6 in a triggered spark-gap switch for pulsed power applications

The high dielectric strength of sulphur hexafluoride (SF₆) when compared with other gases, coupled with safety benefits such as non-flammability and non-toxicity, has seen the widespread use of SF₆ for the insulation of switching components. However, SF₆ is now widely recognised as a highly damaging greenhouse gas, and investigations of the switching properties of alternative gases to replace SF₆ within the bounds of existing system topologies are required. In the present paper, a comparative study has been carried out on a triggered spark-gap of type presently deployed in industrial pulsed-power machines, to determine the suitability of nitrogen (N₂) to replace SF₆ as the switching medium, without compromising on functionality. Experiments were performed with fast-rising trigger pulses to minimise the delay time to breakdown and jitter, and three distinct operational regimes have been identified for both gases as the pressure inside the switch is increased. The static breakdown characteristics and upper pressure boundaries of operation have been determined for both gases at a range of dc charging voltages. Measurements of the time to breakdown have shown jitters as low as 1.3 ns when operating in N₂, highlighting the potential of N₂ to replace SF₆ without the need for re-design or replacement of the presently used switch.