Simulation of ultra-intense laser-matter interaction. The onset of cascading

Complete text of publication follows. With the advent of ELI super-intense laser fields will become available that may interact strongly with the quantum vacuum. The most prominent signal to be expected from vacuum in the presence of ultra-intense laser fields are cascades of electrons, positrons and photons starting off from initial seeds that can be either electrons, positrons or photons. Cascading strongly depends on a quantum efficiency parameter that essentially represents the magnitude of the external laser field in terms of the Schwinger field in the rest frame of the charged particle. Since the latter can be smaller than unity for efficient hard photon emission cascading can be observed at laser fields far below the Schwinger limit. The presentation will show simulations about the onset of cascading from an initial electron as well as photon seed in the presence of two circularly polarized counter-propagating laser pulses. The related growth rates are presented. Details of the simulations will be given. Acknowledgements. This work has been funded by the Munich Centre of Advanced Photonics.