Initial transient stage of pin-to-pin nanosecond repetitively pulsed discharges in air

TL;DR

This study investigates the initial transient behavior of nanosecond repetitively pulsed discharges in air, revealing how discharge parameters evolve and stabilize over multiple pulses at different repetition frequencies.

Contribution

It provides detailed measurements of gas and plasma parameter evolution during the transient stage of NRP discharges in air at various frequencies, highlighting memory effects and steady-state formation.

Findings

Memory effects observed at 10 and 100 kHz

Discharge parameters fluctuate significantly after initial pulses at 10 kHz

Steady state achieved after about five pulses at 100 kHz

Abstract

In this work, evolution of parameters of nanosecond repetitively pulsed (NRP) discharges in pin-to-pin configuration in air was studied during transient stage of initial twenty discharge pulses. Gas and plasma parameters in the discharge gap were measured using coherent microwave scattering (CMS), optical emission spectroscopy (OES) and laser Rayleigh scattering (LRS) for NRP discharges at repetition frequencies of 1, 10 and 100 kHz. Memory effects (when perturbations induced by the previous discharge pulse would not decay fully till the subsequent pulse) were detected for the repetition frequencies of 10 and 100 kHz. For 10 kHz NRP discharge, the discharge parameters experienced significant change after the first pulse and continued to substantially fluctuate between the subsequent pulses due to rapid evolution of gas density and temperature during the 100 us inter-pulse time caused by intense redistribution of the flow field in the gap on that time scale. For 100 kHz NRP discharge, the discharge pulse parameters reached a new steady state at about five pulses after initiation. This new steady state was associated with well-reproducible parameters between the discharge pulses and substantial reduction of breakdown voltage, discharge pulse energy, and electron number density in comparison with the first discharge pulse.