New mechanisms for generating super-ponderomotive electrons in laser-irradiated targets

TL;DR

This paper demonstrates that static electric fields in laser-irradiated sub-critical plasmas can enhance electron acceleration by reducing dephasing, leading to the generation of super-ponderomotive electrons, which is relevant for solid-density target experiments.

Contribution

It introduces new mechanisms involving static electric fields that significantly improve electron acceleration in laser-plasma interactions by reducing dephasing.

Findings

Static electric fields can enhance electron energy in laser-plasma interactions.

Reduced dephasing leads to higher electron axial momentum.

Mechanisms are relevant for experiments with solid-density targets and prepulse effects.

Abstract

It is shown that static longitudinal and transverse electric fields can significantly alter electron acceleration by a long laser beam in a sub-critical plasma, enabling generation of super-ponderomotive electrons. The role of the plasma fields in this regime is not to directly transfer substantial energy to the electron, but rather to reduce the axial dephasing rate between the electron and the laser beam. The reduced dephasing in both cases leads to a subsequent enhancement of the axial momentum and total electron energy. These mechanisms can be relevant to experiments with solid-density targets where a sub-critical plasma layer occurs as a result of a considerable prepulse.