Extreme beams and strong-field QED

With today’s accelerator facilities such as the 10 GeV FACET-II facility at SLAC, extreme beam physics is emerging as a promising science area where ultrashort and dense electron beams can be used as a source of TV/m fields, enabling high field matter interaction and new applications in photon science and particle acceleration. Going beyond, many scientific opportunities arise when the beam density approaches that of a solid, of about 1023-24 cm-3 and when the field can exceed the Schwinger field in the electron rest frame, entering the strong-field regime of quantum electrodynamics (QED) where electron-positron pairs are produced from light-vacuum or light-light interactions, notably via the nonlinear Breit-Wheeler process.

 

Alternatively, multi-pettawatt laser facilities also enable to probe strong-field QED by generating extreme beams in laser-plasma accelerators, that can scatter off lasers with extreme intensities.

In this colloquium, I will present scenarios where electron beams interact with plasmas and lasers in extreme conditions, with experimental results obtained at the FACET-II 10 GeV facility in the US, at the APOLLON laser facility in France and at the ELI-NP laser facility in Romania. The first scenario is an original concept where the electron beam is focused by the beam fields reflected by multiple conducting layers that act as solid-density plasmas, with the potential to reach solid-density beams and enter the strong-field QED regime, as well as to generate electron-positron pair jets. The second scenario considers an ultra-intense laser that is used in three plasma stages to drive a laser-plasma accelerator and generate multi-GeV electrons, be boosted by relativistic laser self-focusing to extreme intensities, and finally be reflected by a plasma mirror to collide head-on with the electron beam and to trigger strong-field QED processes.