Guided Electromagnetic Discharge Pulses Driven by Short Intense Laser Pulses: Characterisation and Modelling

TL;DR

This study experimentally characterizes guided electromagnetic discharge pulses generated by intense laser interactions with solid targets, revealing their temporal, spatial, and field properties, supported by modeling and simulations.

Contribution

It provides detailed time- and space-resolved measurements of EMPs along wires driven by ultra-short laser pulses, combining experimental data with analytical and numerical models.

Findings

EMP durations are tens of ps with kA-range currents and GV/m electric fields.

Proton deflectometry reveals focusing effects due to magnetic and electric fields.

Modeling suggests a surface plasma influences pulse dispersion.

Abstract

Strong electromagnetic pulses (EMP) are generated from intense laser interactions with solid-density targets, and can be guided by the target geometry, specifically through conductive connections to the ground. We present an experimental characterization, by time- and spatial-resolved proton deflectometry, of guided electromagnetic discharge pulses along wires including a coil, driven by 0.5 ps, 50 J, 1e19 W/cm2 laser pulses. Proton-deflectometry data allows to time-resolve first the EMP due to the laser-driven target charging and then the return EMP from the ground through the conductive target stalk. Both EMPs have a typical duration of tens of ps and correspond to currents in the kA-range with electric-field amplitudes of multiple GV/m. The sub-mm coil in the target rod creates lensing effects on probing protons, due to both magnetic- and electric-field contributions. This way, protons of 10 MeV-energy range are focused over cm-scale distances. Experimental results are supported by analytical modelling and high-resolution numerical particle-in-cell simulations, unraveling the likely presence of a surface plasma, which parameters define the discharge pulse dispersion in the non-linear propagation regime.