We demonstrate laser-driven acceleration of electrons to MeV-scale energies at 1 kHz repetition rate using <10  mJ pulses focused on near-critical density He and H₂ gas jets. Using the H₂ gas jet, electron acceleration to ∼0.5  MeV in ∼10  fC bunches was observed with laser pulse energy as low as 1.3 mJ. Increasing the pulse energy to 10 mJ, we measure ∼1  pC charge bunches with >1  MeV energy for both He and H₂ gas jets.

We report on, to the best of our knowledge, the first results of laser plasma wakefield acceleration driven by ultrashort mid-infrared (IR) laser pulses (λ=3.9  μm, 100 fs, 0.25 TW), which enable near- and above-critical density interactions with moderate-density gas jets. Relativistic electron acceleration up to ∼12  MeV occurs when the jet width exceeds the threshold scale length for relativistic self-focusing. We present scaling trends in the accelerated beam profiles, charge, and spectra, which are supported by particle-in-cell simulations and time-resolved images of the interaction. For similarly scaled conditions, we observe significant increases in the accelerated charge, compared to previous experiments with near-infrared (λ=800  nm) pulses.

No abstract

No abstract

No abstract