Onset of electron-positron pair cascades in the collision of tightly focused 10 GeV-class lepton beams

Electron-positron pair cascades develop in extreme astrophysical environments, such as pulsar magnetospheres, and are of fundamental interest in strong-field quantum electrodynamics. Recently, there has been a significant effort to infer the conditions for the onset of pair cascades in the laboratory, using ultra-intense laser fields, such as those soon to be available at multi-petawatt laser facilities.

Here, we explore the possibility of studying pair cascades in the collision of tightly focused lepton beams. When tightly compressed, these charged particle beams can possess electric fields with strengths comparable to multi-PW laser beams. As highly relativistic particles experience these extreme fields from the opposite beam they can produce copious amounts of high-energy radiation, which will in turn produce pairs (T. Grismayer et al, this conference), and give rise to a cascade. Expanding the work for low disruptions regimes (F. Del Gaudio et al., submitted), we discuss the optimal conditions to study this in the laboratory and the corresponding observables.