Robust direct laser acceleration of electrons with flying-focus laser pulses

TL;DR

This paper demonstrates that flying-focus laser pulses significantly improve electron acceleration and x-ray production in direct laser acceleration by mitigating nonlinear plasma effects, as shown through 3D simulations.

Contribution

The study introduces superluminal flying-focus pulses as a novel method to enhance electron acceleration efficiency in DLA, overcoming nonlinear propagation challenges.

Findings

80x more electrons above 100 MeV with FFPs

20% increase in electron cutoff energy

Tripling of high-energy x-ray yield

Abstract

Direct laser acceleration (DLA) offers a compact source of high-charge, energetic electrons for generating secondary radiation or neutrons. While DLA in high-density plasma optimizes the energy transfer from a laser pulse to electrons, it exacerbates nonlinear propagation effects, such as filamentation, that can disrupt the acceleration process. Here, we show that superluminal flying-focus pulses (FFPs) mitigate nonlinear propagation, thereby enhancing the number of high-energy electrons and resulting x-ray yield. Three-dimensional particle-in-cell simulations show that, compared to a Gaussian pulse of equal energy (1 J) and intensity (2x10^20 W/cm^2), an FFP produces 80x more electrons above 100 MeV, increases the electron cutoff energy by 20%, triples the high-energy x-ray yield, and improves x-ray collimation. These results illustrate the ability of spatiotemporally structured laser pulses to provide additional control in the highly nonlinear, relativistic regime of laser-plasma interactions.