Ejecta from compact binary mergers (CBM) emit transient signals known as kilonovae (KN), being one of the electromagnetic counterparts of related gravitational-wave (GW) events. The combined detection of GW170817 and KN transient AT2017gfo has provided observational evidence to rank CBM among the major r-process nucleosynthesis sites, thus making the study of KN a novel challenge for nuclear astrophysics in the multi-messenger astronomy era. Theoretical models, trying to reproduce observed KN light curves, depend on several physical conditions: dynamics, r-process yields, and opacity of the ejecta. In particular, the study of radiative transport in KN is crucial for correct modelling and robust predictions. However, due to the lack of an atomic database, models often oversimplify opacity calculations, causing possible gaps between observations and theory. To bridge this gap, we have recently proposed an experimental setup to measure plasma optical properties in compact magnetic traps in some astrophysical conditions typical of early-stage CBM ejecta. A numerical study in the framework of the PANDORA project has shown that ejecta, at the blue-KN emission stage, reach plasma densities and temperatures around 1012 cm-3 and 1-to-few-eV, respectively. In this work, we report about first tests on the Flexible Plasma Trap at INFN-LNS: plasmas from gaseous elements have been generated via electron cyclotron resonance and explored at different experimental conditions. Reproducible and stable plasma configurations were obtained up to pressures of 10-2 mbar and microwave powers of 400 W, with preliminary measured densities (1011÷1012cm-3) and temperatures (5÷25 eV) promising for the feasibility of the astrophysical task. Plasma parameters were monitored via optical emission spectroscopy and interfero-polarimetric measurements. First attempts of optical properties measurements have been done in hydrogen and argon plasmas reacting to an external white light source, useful for future in-laboratory plasma opacity measurements of metallic plasma species relevant for KN light curve studies.