High Repetition Rate Exploration of the Biermann Battery Effect in Laser Produced Plasmas Over Large Spatial Regions

TL;DR

This study introduces a high-repetition-rate experimental setup to measure the spatial structure and evolution of Biermann magnetic fields in laser-produced plasmas over large areas, extending previous millimeter-scale work.

Contribution

It provides detailed spatial measurements of magnetic fields in laser plasmas over centimeter scales and compares experimental results with simulations, advancing understanding of magnetic field dynamics.

Findings

Magnetic fields range from 60 G to 7 G over 0.7 to 4.2 cm from the target.

Magnetic Reynolds number is approximately 1.4×10^4, indicating dominant magnetic advection.

Experimental results qualitatively agree with FLASH simulations.

Abstract

In this paper we present a high-repetition-rate experimental platform for examining the spatial structure and evolution of Biermann generated magnetic fields in laser-produced plasmas. We have extended the work of prior experiments, which spanned over millimeter scales, by spatially measuring magnetic fields in multiple planes on centimeter scales over thousands of laser shots. Measurements with magnetic flux probes show azimuthally symmetric magnetic fields that range from 60 G at 0.7 cm from the target to 7 G at 4.2 cm from the target. The expansion rate of the magnetic fields and evolution of current density structures are also mapped and examined. Electron temperature and density of the laser-produced plasma are measured with optical Thomson scattering and used to directly calculate a magnetic Reynolds number of $1.4\times 10^4$, confirming that magnetic advection is dominant $\ge 1.5$ cm from the target surface. The results are compared to FLASH simulations, which show qualitative agreement with the data.