Cooling of relativistic electron beams in chirped laser pulses

TL;DR

This paper investigates how chirped laser pulses influence the cooling of relativistic electron beams, considering quantum effects that modify classical radiation reaction predictions, with implications for next-generation high-power laser facilities.

Contribution

It introduces a semi-classical extension to the Landau--Lifshitz theory to analyze the impact of pulse chirping on beam cooling, highlighting the relative insignificance of chirp compared to quantum effects.

Findings

Chirps cause smaller changes in final beam states than quantum effects.

Quantum effects suppress classical beam cooling predictions.

Pulse energy distribution influences the dynamics significantly.

Abstract

The next few years will see next-generation high-power laser facilities (such as the Extreme Light Infrastructure) become operational, for which it is important to understand how interaction with intense laser pulses affects the bulk properties of a relativistic electron beam. At such high field intensities, we expect both radiation reaction and quantum effects to play a significant role in the beam dynamics. The resulting reduction in relative energy spread (beam cooling) at the expense of mean beam energy predicted by classical theories of radiation reaction depends only on the energy of the laser pulse. Quantum effects suppress this cooling, with the dynamics additionally sensitive to the distribution of energy within the pulse. Since chirps occur in both the production of high-intensity pulses (CPA) and the propagation of pulses in media, the effect of using chirps to modify the pulse shape has been investigated using a semi-classical extension to the Landau--Lifshitz theory. Results indicate that even large chirps introduce a significantly smaller change to final state predictions than going from a classical to quantum model for radiation reaction, the nature of which can be intuitively understood.