Optimized multibeam configuration for observation of QED cascades

TL;DR

This paper derives a general expression for the quantum parameter of electrons in arbitrary electromagnetic fields and optimizes multibeam laser configurations to induce QED cascades at feasible laser powers and intensities.

Contribution

It provides a new formula for electron quantum parameter in complex fields and proposes an optimized laser setup for observing QED cascades at upcoming laser facilities.

Findings

Derived a general expression for the quantum parameter $hi$ in arbitrary fields.

Optimized multibeam laser configuration for cascade development below 10 PW.

Feasible parameters for QED cascade observation with upcoming laser technology.

Abstract

QED cascades in intense electromagnetic field can occur if the dynamical quantum parameter $\chi$ of a seed electron, which in Compton units coincides with the electron proper acceleration, attains the order of unity. We derive general expression for $\chi$ of an initially slow electron in an arbitrary electromagnetic field for a time range $t\ll 1/\omega$, where $\omega$ is the field carrier frequency. Using this formula, we consider a special field configuration of multiple colliding focused laser beams and optimize it to provide cascade development at laser power below $10$ PW and intensity of the order of $10^{23}$W/cm$^2$. Such parameters of the beams will be obtained with a new generation of laser facilities, particularly the ELI Beamlines, in the coming years.