Diagnosing electric and magnetic fields in laser-driven coil targets

TL;DR

This paper develops methods to accurately distinguish and measure electric and magnetic fields in laser-driven coil experiments using proton radiography, validated by simulations and applied to complex coil configurations.

Contribution

It introduces a systematic analysis and new techniques to separate electric and magnetic field contributions in proton radiographs, improving diagnostic accuracy.

Findings

Methods successfully isolate magnetic and electric fields in radiographs

Validated techniques with experimental benchmarks

Applied to measure current and charge in double coil setup

Abstract

Laser-driven capacitor coils are widely used to generate intense magnetic fields for various applications in high-energy-density physics research. Accurate measurement of the magnetic fields is essential but challenging, due to the overlapping contributions from magnetic and electric fields in proton radiography, which is the primary tool diagnosing the field generation around the coils. In this study, we systematically analyze proton radiographs obtained from laser-driven capacitor-coil targets along two orthogonal axes under various electromagnetic field conditions, including magnetic field only, electric field only, and combined electromagnetic fields. By analyzing key features in the radiographs, we distinguish and characterize the respective contributions from magnetic and electric fields. Using detailed simulations validated by experimental benchmarks, methods to isolate and quantify the magnetic field and electric field are given. The methods are successfully applied to determine the electric current and charge distribution in a double coil configuration. Our findings provide insights into improving the diagnostic capability of proton radiography, potentially leading to more accurate measurements of electromagnetic fields and enhancing the utility of laser-driven capacitor coils in high-energy-density experiments.