Spatial profile of accelerated electrons from ponderomotive scattering in hydrogen cluster targets

TL;DR

This study investigates laser-driven electron acceleration from hydrogen clusters, revealing two electron populations mainly due to ponderomotive scattering, with implications for high-repetition-rate laser applications.

Contribution

It provides experimental and simulation insights into electron acceleration mechanisms from hydrogen clusters, highlighting the role of ponderomotive scattering in different electron populations.

Findings

Electrons reach up to 13 MeV in forward direction.

An outer ring-like electron structure is observed.

Higher electron densities produce a central electron spot.

Abstract

We study the laser-driven acceleration of electrons from overdense hydrogen clusters to energies of up to 13 MeV in laser forward direction and several hundreds of keV in an outer ring-like structure. The use of cryogenic hydrogen allows for high repetition-rate operation and examination of the influence of source parameters like temperature and gas flow. The outer ring-like structure of accelerated electrons, originating from the interaction, that is robust against the change of laser and target parameters can be observed for low electron densities of ca. 3$\times$10$^{16}$ cm$^{-3}$. For higher electron densities, an additional central spot of electrons in the laser forward direction can be observed. Utilizing 3D-PIC simulations, it is revealed that both electron populations mainly stem from ponderomotive scattering.