Laser Wakefield Acceleration from Nebular-Shaped Plasmas*

Intense lasers made available for the first-time high-energy electron sources at university scale laboratories. For the past two decades, the community focused on optimizing the accelerated beam quality in terms of higher energy, sharper energy spectrum, and improved repeatability.

Early works observed ultra-collimated, multi-MeV beams of electrons, that were generated following multi-TW irradiation of thin solid foils pre-exploded by uncontrollable precursor light. In these experiments, the unprecedented conversion efficiency of laser light to electrons was hypothesized to relate to the nearly critical density of the plasma plume.

I will present a first controlled investigation of laser wakefield acceleration from nebular-shaped plasmas. In these experiments, which were conducted on the high-contrast 20 TW laser system at Tel-Aviv U., we pre-exploded thin foil targets with a controlled pre-pulse,  nanoseconds prior to the interaction with the main beam. We tailored the pre-plasma plume profile by varying the pre-pulse energy, and the time delay between the pre- and main-pulses.

I will present our preliminary results, along with an analytical model for the plasma expansion, and discuss insights of the underlaying dynamics gained from particle-in-cell simulations. I will conclude with the prospects of scaling this method to PW-level lasers, and using the accelerated electrons for photo-nuclear reactions studies.