High-resolution Optical Emission Spectroscopy characterization of hydrogen and argon laboratory magneto-plasmas of astrophysical interest.

In the last decades there has been a growing interest to investigate the origin of elements heavier than iron in the Universe, produced via $r$-process nucleosynthesis. Detection of kilonovae, released after the merging of compact binary objects, is relevant to constrain the $r$-process nucleosynthesis elements yield in these astrophysical $loci$. In the framework of the PANDORA project, we are developing a new plasma trap for the emulation of kilonovae ejecta properties at a specific stage of their evolution, providing measurements of plasma opacity and new insights about heavy-elements nucleosynthesis. To verify the feasibility of this kind of measurements in terms of temperature and density (order of eV and $10^{12} {cm^{-3}}$, respectively) we used the Flexible Plasma Trap, operative at INFN-LNS, as testbench for PANDORA, to characterize gaseous plasma ($H_{2}$, Ar) parameters by Optical Emission Spectroscopy. The experimental results will be presented, concerning estimates of plasma density and temperature, deduced by means of the line-ratio method, from spectra analysis in the visible range under different plasma trap configurations.