Simulations of laser-target interactions are investigated using the open source, plasma physics simulation code EPOCH (Extendable PIC Open Collaboration) provided in 1D, 2D and 3D versions by CCP-Plasma (The Collaborative Computational Project in Plasma Physics). This relativistic, MPI parallelised PIC code includes, among others, physical processes that may take place in laser-target interactions at ultra-high laser intensities, such as barrier suppression ionisation, quantum electrodynamics (QED) emission and pair production via Breit-Wheeler and Trident processes (in which probabilities of gamma-photon emission or electron-positron pair generation are modelled using a Monte-Carlo technique). Therefore, with the EPOCH code it is possible to simulate laser-target interactions at intensities that ELI-Beamlines is expected to achieve. Data obtained from these simulations can be consequently analysed by several visualisation tools like Mathworks MatLab, VisIt or IDL.

The potential for laser-produced plasmas to yield fundamental insights into high energy density physics (HEDP) is of great interest. Plasmas created in laser laboratory experiments resemble to exciting physical phenomena like astrophysical jets, inertial confinement fusion (ICF) or warm dense matter (WDM). In order to investigate crucial plasma properties (e.g. opacities, equation of state) corresponding to HEDP relevant densities and temperatures, scientists at ELI employ and develop radiation hydrodynamics simulation codes appropriate to reflect theoretical and experimental results. These codes are designed to cover either macroscopic (e.g. expanded plasma profile) or microscopic (e.g. photon spectra) properties of plasma generated in long time scales. This is of special importance in the design of ultra-short pulses experiments, where an expansion of plasma occurs due to nanosecond pre-pulse.

Beside the simulations dedicated to laser-target interactions, at ELI-Beamlines the Monte Carlo transport code FLUKA is used to study the propagation of the radiation. It is an integrated particle physics simulation package developed in cooperation between CERN and INFN. It has many applications in high energy experimental physics and engineering, shielding, detector and telescope design, cosmic ray studies, dosimetry, medical physics and radio-biology. Particularly, at ELI-Beamlines it is used for radiation protection studies and to simulate experiments.