Multi-laser QED cascades in 2D and 3D geometry

Studying the plasma dynamics in the presence of extreme laser fields requires taking into account physics beyond classical electrodynamics. Pair production seeded by an electron has a lowest threshold among the first quantum mechanisms that appear as the intensity increases, which makes it relevant for the future experiments planned at ELI [1] and other facilities. We have included the two-step pair production process (non linear Compton scattering $+$ Breit-Wheeler) in a massively parallel PIC code (Osiris 2.0 framework) via a Monte Carlo module. With this approach, we take self-consistently into account the interaction of the intense fields with the generated pair plasma. We have also developed a macroparticle merging algorithm that reduces the number of macroparticles in the simulations, while conserving local particle distributions [2]. This algorithm is crucial for simulating scenarios where a large number of pairs are being created, such as QED cascades.~ We present 2D and 3D PIC-QED study of pair cascades induced with multiple laser pulses. The polarization dependence is discussed, together with the properties of the emitted radiation and experimental signatures.~ \\[4pt] [1] http://www.eli-laser.eu/\\[0pt] [2] M. Vranic et al., CPC 191, 65-73 (2015)