Ultra-intense laser pulse characterization using ponderomotive electron scattering

TL;DR

This paper introduces an analytical model for relativistic electron scattering in high-intensity laser pulses, enabling laser intensity measurement through electron distribution patterns, validated by simulations.

Contribution

It provides a new analytical solution for electron dynamics in focused laser pulses and links scattering angles to laser parameters for pulse characterization.

Findings

Scattering angles depend on initial electron energy and laser amplitude.

Two regimes identified: focusing-dominated and power-dominated scattering.

Laser intensity can be inferred from electron scattering patterns.

Abstract

We present a new analytical solution for the equation of motion of relativistic electrons in the focus of a high-intensity laser pulse. We approximate the electron's transverse dynamics in the averaged field of a long laser pulse focused to a Gaussian transverse profile. The resultant ponderomotive scattering is found to feature an upper boundary of the electrons' scattering angles, depending on the laser parameters and the electrons' initial state of motion. In particular, we demonstrate the angles into which the electrons are scattered by the laser scale as a simple relation of their initial energy to the laser's amplitude. We find two regimes to be distinguished in which either the laser's focusing or peak power are the main drivers of ponderomotive scattering. Based on this result, we demonstrate how the intensity of a laser pulse can be determined from a ring-shaped pattern in the spatial distribution of a high-energy electron beam scattered from the laser. We confirm our analysis by means of detailed relativistic test particle simulations of the electrons' averaged ponderomotive dynamics in the full electromagnetic fields of the focused laser pulse.