Energetic electrons produced in the interaction of a kiloHertz femtosecond laser with tantalum targets

Abstract

The electrons produced in the interaction of a high repetition rate laser with a thick tantalum target generate a continuous distribution of photons via the bremsstrahlung process occurring mainly in the target. The photon energy distributions, between 50 and 500 keV, are unfolded to obtain the true X-ray energy distributions. These distributions are used in a Monte Carlo simulation to infer the initial electron energy distributions. These properties have been studied at laser intensities ranging from 3 × 1015 to 6 × 1016 W cm− 2. The electron energy distributions are different above ≃2 × 1016 W cm− 2 as compared to lower intensities. This is evidence for a different laser plasma interaction regime.