Study on the saturation phenomena of discharge channel number of a gas spark switch gap under nanosecond trigger pulses

Experimental work was carried out to study the variation of nanosecond trigger pulse amplitude on discharge channel numbers in a self-designed coaxial field distortion gas spark switch gap in N₂, SF₆-N₂ or SF₆-Ar gas mixtures. The results show that channel numbers in a unit of length of the edge of trigger electrode make a great difference among three kinds of gases (i.e. N2, SF₆-N₂ mixtures, and SF₆-Ar mixtures). In each kind of gases under a certain pressure, the difference of channel numbers in a unit of length among different mixture ratios is smaller compared with that among different kinds of gases. In view of this, one fitting curve was got based on data of channel numbers in a unit of length varying with overvoltage multiple for each kind of gases under a certain pressure despite of the difference among mixture ratios. It can be seen from these fitting curves that the channel number in a unit of length does not increase evidently and tends to saturation when applied overvoltage multiple across the switch gap exceeds 3 for N₂ and 2.5 for SF₆-N₂. However, the saturation phenomena of channel numbers in SF₆-Ar are not obvious in these experiments.