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

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-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-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 × 10 ^16 cm ^−3 . For higher electron densities, an additional central spot of electrons in the laser forward direction can be observed. Utilizing 3D particle-in-cell simulations, it is revealed that both electron populations mainly stem from ponderomotive scattering.

Keywords

• laser–plasma acceleration of electrons and ions
• plasma production and heating by laser beams
• cluster targets