Strong electromagnetic pulses generated in high-intensity short-pulse laser interactions with thin foil targets

TL;DR

This study investigates electromagnetic pulse generation during high-intensity laser interactions with thin foil targets, revealing higher currents and complex magnetic field dynamics compared to thick targets, with implications for laser-plasma physics.

Contribution

It extends previous research on thick targets to thin foils, providing detailed measurements and analysis of electromagnetic emissions and magnetic fields in laser-target interactions.

Findings

Thin foils generate 20-50% higher neutralization current and charge.

Initial magnetic field spike aligns with 1 ns pulse, with sub-ns variations.

Linear correlation between magnetic field maximum and neutralization current, except for very long pulses.

Abstract

Measurements are reported of the target neutralization current, the target charge, and the tangential component of the magnetic field generated as a result of laser-target interaction by pulses with the energy in the range of 45 mJ to 92 mJ on target and the pulse duration from 39 fs to 1000 fs. The experiment was performed at the Eclipse facility in CELIA, Bordeaux. The aim of the experiment was to extend investigations performed for the thick (mm scale) targets to the case of thin (micrometer thickness) targets in a way that would allow for a straightforward comparison of the results. We found that thin foil targets tend to generate 20 to 50 percent higher neutralization current and the target charge than the thick targets. The measurement of the tangential component of the magnetic field had shown that the initial spike is dominated by the 1 ns pulse consistent with the 1 ns pulse of the neutralization current, but there are some differences between targets of different type on sub-ns scale, which is an effect going beyond a simple picture of the target acting as an antenna. The sub-ns structure appears to be reproducible to surprising degree. We found that there is in general a linear correlation between the maximum value of the magnetic field and the maximum neutralization current, which supports the target-antenna picture, except for pulses hundreds of fs long.