High Repetition-Rate Wakefield Electron Source Generated by Few-millijoule, 30 femtosecond Laser Pulses on a Density Downramp

TL;DR

This paper demonstrates high-repetition-rate laser wakefield electron acceleration using low-energy femtosecond pulses, producing stable, well-collimated electron beams with energies over 100 keV, enabled by a density downramp mechanism.

Contribution

It introduces a novel high-repetition-rate (0.5 kHz) laser wakefield acceleration setup with low-energy pulses, achieving stable electron beams and validating the mechanism through simulations.

Findings

Stable electron beams with >100 keV energy

Achieved 0.5 kHz repetition rate

Excellent agreement between simulations and experiments

Abstract

We report on an experimental demonstration of laser wakefield electron acceleration using a sub-TW power laser by tightly focusing 30-fs laser pulses with only 8 mJ pulse energy on a 100 \mu m scale gas target. The experiments are carried out at an unprecedented 0.5 kHz repetition rate, allowing "real time" optimization of accelerator parameters. Well-collimated and stable electron beams with a quasi-monoenergetic peak in excess of 100 keV are measured. Particle-in-cell simulations show excellent agreement with the experimental results and suggest an acceleration mechanism based on electron trapping on the density downramp, due to the time varying phase velocity of the plasma waves.