Controllable non-ideal plasmas from photoionized compressed gases

Abstract

Based on a suite of molecular dynamics simulations, we propose a strategy for producing non-ideal plasmas with controllable properties over a wide range of densities between those of ultracold neutral plasmas and those of solid-density plasmas. We simulated the formation of non-equilibrium plasmas from photoionized, cool gases that are spatially precorrelated through neutral–neutral interactions that are important at moderate-to-high pressures. A wide range of physical properties, including Coulomb collisional rates, partial pressures, screening strengths, continuum lowering, interspecies Coulomb coupling, electron degeneracy and ionization states, were characterized across more than an order of magnitude variation in the initial gas pressure. A wide range of plasma properties are also found to vary when the initial pressure of a precorrelated gas is varied. Thus, we propose that non-ideal plasmas with tunable properties can be generated by photo-ionizing a dense, precorrelated gas. We find that the optimal initial density range for the gas is near a Kirkwood/Widom–Fisher line in the neutral-gas phase diagram. This strategy for generating non-ideal plasmas suggests experiments that have significant advantages over both ultracold and solid-density plasma experiments because the collisional, collective and recombination timescales can be tuned across many orders of magnitude, potentially allowing for a wider range of diagnostics. Moreover, the added costs of cooling ultracold plasmas and diagnosing dense matter with x-rays are eliminated.