The objective of this experiment is to accelerate electrons to multi-GeV energies in an optically controlled plasma waveguide created from a light gas. Today, one of the main challenges for the scientific community working on laser-plasma acceleration of electrons is to increase the length of the laser-plasma interaction to maximize the energy transfer from the laser to the electrons and thus increase the energy of the accelerated beam. In most laser-plasma accelerators, laser diffraction limits the acceleration length to the Rayleigh length or a few Rayleigh lengths through plasma self-focusing. The key idea of this project is to create a plasma channel, with a first low-intensity pulse, that acts as an optical fiber to propagate the beam with relativistic intensities over distances of several centimeters. This plasma waveguide, coupled with a controlled injection technique, will allow obtaining high-quality electron beams with energies of several GeV.

The project continues an experiment conducted in 2022, during which we demonstrated the concept by producing electron beams with peaked spectra at 2.2 GeV. We lacked time to optimize the beam during this first experiment. Here, we aim to use this experiment feedback to produce stable, high-quality beams at 4 GeV.

Such achievements would pave the way to further scientific experiments requiring high-energy electron beams, notably in regimes where the quantum electrodynamics (QED) mechanisms become significant, for instance, with the collision of a relativistic electron beam with an ultra-intense laser beam.