Definite vacuum for strong-field quantum electrodynamics experiments

Abstract Ultra-intense lasers can generate the strongest electromagnetic fields in laboratory conditions, and are expected to perform tests of quantum electrodynamics (QED) in yet unexplored parameter ranges. Such experiments require knowledge of the field strengths and all possible interaction pathways. The latter can be simplified if a perfect, particle-free vacuum is present, thereby excluding competing interactions. We propose a method to evacuate all residual gas particles prior to QED interactions, based on tunnel ionization by a preceding auxiliary laser pulse and a static electric field. We present modelling and experimental results of testing this method on a $0.5\;\mathrm{TW}$ chirped pulse amplification laser system. Experimental results match well the simulations for the given conditions and thereby provide valuable understanding to extrapolate this method for QED experiments with PW-class laser systems where it can likewise be employed for in situ peak field strength characterization.