Radiative particle-in-cell simulations - plasma based light sources and synthetic spectroscopy

We present simulated far field radiation spectra from plasma based light sources such as high harmonics generation (HHG) during laser foil irradiation and betatron oscillation during laser-wakefield-acceleration (LWFA). The synthetic spectra allow quantifying both total radiation flux of these light sources and the occurring radiation background. We also present applications of far field radiation as spectroscopic diagnostic of the plasma dynamics occurring during LWFA and a variety of plasma instabilities, such as Kelvin-Helmholtz and the Rayleight-Taylor instability. This so-called synthetic diagnostic allows probing the electron dynamics by predicting the emitted radiation spectra thus emulating real experiments.

In order to obtain these results, we developed an in-situ method to compute spectrally and angularly resolved far field radiation based on Liénard-Wiechert potentials. By computing radiation concurrently to simulating the plasma dynamics, using the particle-in-cell code PIConGPU, we are able to take into account all $sim10^{10}$ electrons simulated, thus allowing to quantify both coherent and incoherent radiation. Furthermore, spectra can be computed for thousand of observation directions and frequencies simultaneously. We show that the code’s capability of resolving radiation processes temporally is an indispensable tool for linking the evolution of the plasma dynamics to the emitted radiation.