QED cascade saturation in extreme high fields.

Upcoming ultrahigh power lasers at 10 PW level will make it possible to experimentally explore electron-positron (ee) pair cascades and subsequent relativistic ee jets formation, which are supposed to occur in extreme astrophysical environments, such as black holes, pulsars, quasars and gamma-ray bursts. In the latter case it is a long-standing question as to how the relativistic jets are formed and what their temperatures and compositions are. Here we report simulation results of pair cascades in two counter-propagating QED-strong laser fields.