Plasma Dynamics in ultra-short relativistic laser-solid matter interactions and synthetic diagnostics using XFELs

Abundant and complex plasma dynamics are triggered by optical ultra-short high power lasers interacting on solid targets: such as atomic ionization, hot electron generation and transportation, collisions between the charged particles, return current, bulk electron heating, ion heating and acceleration, instabilities and so on. Controlling the relative dynamic processes requires modelling of transient, non-equilibrium processes on the atomic scale. We present particle-in-cell simulations which studied enhanced ion heating in buried layer targets [1], ionization dynamics and instabilities. In order to connect the plasma dynamics seen in simulations with experiments we will discuss the role of in-situ synthetic diagnostics that mimic experimental diagnostics. As one key example we propose to use X-Ray Free Electron Lasers for probing laser-driven solid-density plasmas by small angle X-ray scattering [2] which allows for femtosecond and nanometer resolution of transient plasma processes. With these techniques, probing fundamental plasma properties will allow for direct comparison to simulations, challenging state of the art theoretical modeling of collisions, ionization, radiation transport and atomic processes.