Ionization potential depression in strongly coupled moderately degenerate plasmas generated in supercritical fluids

Strongly coupled plasmas are of significant interest as they occur in diverse astrophysical environments including the Sun's inner region and inertial confinement fusion experiments. While theoretical and simulation-based studies have provided important insights into their properties, experimental investigations have been limited due to the challenges of producing and sustaining such extreme plasma conditions in laboratory. To date, most experimental work on strongly coupled plasmas has focused on solid targets, leaving high-density plasmas generated in supercritical fluids largely unexplored. Our previous work (Lee et al. Plasma Phys. Control. Fusion (2022)) showed that supercritical fluids have several advantages as a medium for the generation of strongly coupled plasmas such as ease of focusing the laser pulse anywhere within the fluid target, and no loss of energy related to phase transition from solid to liquid or gas. We present a progress focusing on the role of ionization potential depression (IPD) in the process of high-density plasma formation in supercritical helium, argon, and krypton. The laser-produced plasmas exhibit the characteristics of strongly coupled and moderately degenerate state (high density and low temperature) confirmed through various optical diagnostics. The comparison of the plasma properties among the three different media shows that IPD is the dominant mechanism driving high-density plasma formation under our experimental conditions.