Laser-Plasma Particle-in-Cell Simulation Reproducibility and QED Effects

The goals of discovering quantum radiation dynamics in high-intensity laser-plasma interactions and engineering new laser-driven high-energy particle sources both require accurate and robust predictions. We demonstrate a characteristic dipole pattern of high-energy photon emission that results when the laser pulse bores through the target, forming a channel that enhances the laser field. We establish that the phenomenon is robust by showing that the dipole pattern gradually switches on as a function of target density, and with no need for wavelength-scale structure in the target, as used in previous work. This phenomenon is robust to experimentally motivated perturbations including a preplasma and non-normal laser-target angle. We analyze statistical uncertainties that result from running the same simulation multiple times with different random seeds and compare results from two particle-in-cell codes.