Resistance and Inductance of a Laser Triggered Air Sparkgap in the Range 50kV /20kA / 50ns

This study is related to a high voltage pulse generator meant to trigger 3 trigatrons. The electric charge is stored in 2 sets of 3 ceramic capacitors of 1.1 nF connected in series-T and charged to -50 kV. A laser sparkgap is used for shorting the first set of capacitors whereas a pulse is generated on the second set. The output voltage amplitude depends on the sparkgap resistance Rgap and inductance Lgap. These parameters are studied with an output load of 1.7 Omega in parallel with a shunt of 54 Omega combined with a current monitor. Electric models are proposed to get simulations in accordance with the current recordings. It appears that Rgap and Lgap are different whether the laser beam is focused or not in the gap. Finally, Rgap(t) is compared with a Toepler type formula.