Impact of Snubber Circuit Inductance on Damping Late Currents in a Pulsed Power Circuit

Abstract

The discharge in a repetitively pulsed TE gas laser begins its lasing cycle by being homogenous in nature but quickly (10s of ns later) transitions into filamentary mode due to plasma discharge instabilities. The filamentary discharge transitions into an arc mode which presents a very low impedance path for the pulsed power circuit. Hence the current is weakly damped and continues to oscillate (resonance) until all of the circuit energy is dissipated. This post lasing remnant circuit energy causes electrode erosion and contamination of the lasing gas. Ideally, all of the initially stored energy must be deposited in the homogenous discharge at the optimum pumping intensity but due to the plasma discharge instabilities it is very difficult to avoid the filamentary arc discharge mode. Therefore, an effort is made on reducing the intensity of the current flowing through the discharge and pulsed power circuit in the post-lasing stage (late currents). A snubber circuit is deployed across the main energy storage capacitor in the pulsed power circuit to dissipate a portion of the remnant circuit energy. The snubber circuit consists of a series string of HV diodes and a series resistor. The diodes become forward biased when the storage capacitor voltage reverses polarity and allows current flow through the snubber resistance which dissipates energy. An optimum value of the snubber resistance was experimentally confirmed. The maximum amount of energy dissipated in the snubber is ultimately constrained by mutual induction effects between adjoining loops.