Electromagnetic pulse emission from target holders during short-pulse laser interactions

TL;DR

This paper introduces a comprehensive model linking charge separation in laser targets to electromagnetic pulse emissions, validated with experimental data, and explores how target holder geometry influences EMP characteristics.

Contribution

It presents a novel frequency-domain dipole antenna model that predicts EMP emissions and target charge accumulation, validated across multiple laser facilities.

Findings

EMP amplitude correlates with total target charge.

Charging time does not significantly affect EMP if shorter than antenna time.

Target holder geometry impacts EMP emissions.

Abstract

For the first time, a global model of electromagnetic pulse (EMP) emission connects charge separation in the laser target to quantitative measurements of the electromagnetic field. We present a frequency-domain dipole antenna model which predicts the quantity of charge accumulated in a laser target as well as the EMP amplitude and frequency. The model is validated against measurements from several high-intensity laser facilities, providing insight into target physics and informing the design of next-generation ultra-intense laser facilities. EMP amplitude is proportional to the total charge accumulated on the target, but we demonstrate that it is not directly affected by target charging time (and therefore the laser pulse duration) provided the charging time is shorter than the antenna characteristic time. We propose two independent methods for estimating the charging time based on the laser pulse duration. We also investigate the impact of target holder geometry on EMPs using cylindrical, conical and helical holders.