Laser-driven electron breakout from ultra-thin targets

The acceleration of electrons from ultra-thin foils using high-intensity lasers has recently gained high interest due to the outstanding characteristics of the generated electron beam observed in particle-in-cell simulations. Here, the generation of a relativistic electron bunch of ultra-high density was demonstrated which may be well-suited for the generation of ultra-short coherent x-ray radiation via Thomson back-scattering. With the advent of ultra-high contrast, high power lasers and the fabrication of ultra-thin, few nm thick targets, this new concept to generate a relativistic electron mirror may now become feasible in experiment. We report on the electron acceleration from ultra-thin diamond-like carbon (DLC) foils using the Trident 200 TW ultra-high contrast laser pulse. While thick targets show maxwellian shaped electron spectra a pronounced, quasi- monoenergetic characteristic peaked at 30 MeV is observed at a target thickness as thin as 5 nm³. The experimental findings give first indication that laser- driven relativistic electron mirrors can be generated from ultra-thin foils, which in future may be used to generate intense X-ray beams by the coherent reflection of a second laser.