Attaining a strong-field QED signal at laser-electron colliders with optimized focusing

Abstract

Colliding bunches of high-energy electrons with intense laser pulses provides a basis for studying strong-field QED processes enabled by high values of quantum nonlinearity parameter χ. Nevertheless, the signal deconvolution is intricate due to the probabilistic nature of the processes and shot-to-shot variation of the impact parameter, which disfavors the use of tight focusing. We propose a concept for distinguishing the signal of high-χ emissions that enables the use of optimal focusing to attain the highest χ≈5.25[(1GeV)][P/(1PW)]1/2[(1μm)/λ] for a given electron energy, laser power P, and wavelength λ. Reaching such a χ with f/2 focusing requires more than 10 times higher power.