Retrieving transient magnetic fields of ultrarelativistic laser plasma via ejected electron polarization

TL;DR

This paper explores how the polarization of ejected electrons in ultrarelativistic laser-plasma interactions can be used to infer the properties of transient magnetic fields generated in the plasma, offering a new diagnostic approach.

Contribution

It introduces a novel method to retrieve transient magnetic field features in laser-plasma interactions using electron spin polarization data from particle-in-cell simulations.

Findings

Electron polarization correlates with plasma magnetic field structure.

Spin signal magnitude indicates magnetic field strength.

Polarization asymmetry reveals magnetic distribution patterns.

Abstract

Interaction of an ultrastrong short laser pulse with non-prepolarized near-critical density plasma is investigated in an ultrarelativistic regime, with an emphasis on the radiative spin polarization of ejected electrons. Our particle-in-cell simulations show explicit correlations between the angle resolved electron polarization and the structure and properties of the transient quasistatic plasma magnetic field. While the magnitude of the spin signal is the indicator of the magnetic field strength created by the longitudinal electron current, the asymmetry of electron polarization is found to gauge the island-like magnetic distribution which emerges due to the transverse current induced by the laser wave front. Our studies demonstrate that the spin degree of freedom of ejected electrons could potentially serve as an efficient tool to retrieve the features of strong plasma fields.