Shock Wave in Leader Discharge Observed Using Mach-Zehnder Interferometry

TL;DR

This study observes shock waves in air-gap leader discharges using Mach-Zehnder interferometry, revealing their propagation at near sound speed and linking energy injection to shock wave formation.

Contribution

First direct observation of shock waves in leader discharges with high temporal resolution and validation through thermo-hydrodynamic modeling.

Findings

Shock wave propagates at nearly the speed of sound.

Simulation aligns well with experimental shock front positions.

Energy injection causes over-pressure leading to shock wave formation.

Abstract

A leader is an electric discharge mechanism in long-air-gap discharges. In this work, we report the shock wave phenomenon in an air-gap leader discharge observed using a Mach-Zehnder interferometer with a time resolution of several microseconds. The continuous temporal evolution of the shock wave and the plasma channel was recorded and reproduced with a thermo-hydrodynamic model based on the measured current. The wave propagated at nearly the speed of sound, and the simulation results for the shock wave front positions and the plasma channel radius showed good consistency with the experimental measurements. Detailed thermal parameters obtained through the simulation showed that continuous energy injection by the current results in a temporary over-pressure process in the plasma channel and produces the shock wave.