Longitudinal and transverse cooling of relativistic electron beams in intense laser pulses

TL;DR

This paper investigates how intense laser pulses cause radiative cooling of relativistic electron beams, revealing classical symmetry and quantum regime asymmetry in phase space contraction, with cooling depending on laser energy distribution.

Contribution

It introduces a new technique to analyze particle distribution evolution, demonstrating quantum effects reduce beam cooling and depend on laser energy distribution.

Findings

Classical regime shows equal transverse and longitudinal cooling.

Quantum regime exhibits reduced longitudinal cooling.

Cooling depends on laser energy distribution, not just total energy.

Abstract

With the emergence in the next few years of a new breed of high power laser facilities, it is becoming increasingly important to understand how interacting with intense laser pulses affects the bulk properties of a relativistic electron beam. A detailed analysis of the radiative cooling of electrons indicates that, classically, equal contributions to the phase space contraction occur in the transverse and longitudinal directions. In the weakly quantum regime, in addition to an overall reduction in beam cooling, this symmetry is broken, leading to significantly less cooling in the longitudinal than the transverse directions. By introducing an efficient new technique for studying the evolution of a particle distribution, we demonstrate the quantum reduction in beam cooling, and find that it depends on the distribution of energy in the laser pulse, rather than just the total energy as in the classical case.