Predictive Particle-in-Cell simulations for a near critical density ion acceleration experiment

A relativisticly intense laser can turn a near critical density plasma slowly transparent, facilitating a synchronized acceleration of ions at the moving relativistic critical density front. While idealized simulations promise extremely high ion energies in in this regime, the challenge resides in realistic assumptions for the laser and plasma parameters. Here we report on a numerical study including the preplasma expansion dynamics and realistic laser pedestal, the challenges in the near critical density regime, and the relevance for predictive capabilities of the simulations.