Plasma dynamics of a laser filamentation-guided spark

TL;DR

This study explores how plasma decay in laser filamentation-guided sparks depends on current pulse characteristics, revealing that alternative current can prolong plasma lifetime by aligning electron density with current evolution.

Contribution

It provides experimental insights into plasma decay mechanisms and introduces a criterion for controlling plasma lifetime using different current types.

Findings

Plasma decay is dominated by recombination when current decay is rapid.

Electron density follows current evolution in slow decay cases.

Alternative current extends plasma lifetime compared to direct current.

Abstract

We investigate experimentally the plasma dynamics of a centimeter-scale, laser filamentation-guided spark discharge. Using electrical and optical diagnostics to study monopolar discharges with varying current pulses we show that plasma decay is dominated by free electron recombination if the current decay time is shorter than the recombination characteristic time. In the opposite case, the plasma electron density closely follows the current evolution. We demonstrate that this criterion holds true in the case of damped AC sparks, and that alternative current is the best option to achieve a long plasma lifetime for a given peak current.