Reaching supercritical field strengths with intense lasers

Understand

It is conjectured that all perturbative approaches to quantum electrodynamics (QED) break down in the collision of a high-energy electron beam with an intense laser, when the laser fields are boosted to `supercritical' strengths far greater than the critical field of QED.

• As field strengths increase toward this regime, cascades of photon emission and electron-positron pair creation are expected, as well as the onset of substantial radiative corrections.
• Here we identify the important role played by the collision angle in mitigating energy losses to photon emission that would otherwise prevent the electrons reaching the supercritical regime.
• We show that a collision between an electron beam with energy in the tens of GeV and a laser pulse of intensity $10^{24}~\text{W}\text{cm}^{-2}$ at oblique, or even normal, incidence is a viable platform for studying the breakdown of perturbative strong-field QED.