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 nonideal 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. two-temperature variations (i.e., separate electron and ion temperatures). The desired method would allow for systematic control of plasma properties, including transport and relaxation, ionization-potential depression (IPD), the non-ideal multi-temperature equation of state (EOS), and screening involving strongly coupled electrons. Transport properties [43,44] and relaxation processes [45][46][47][48] are important to validate and model dense plasma experiments. The advent of XFEL [49-51] has renewed interest in IPD (a.k.a.'continuum lowering'), and dense plasma experiments have been used to validate different IPD models [52][53][54][55]. An accurate EOS is essential for examining plasma evolution on the hydrodynamic scale, such as the evolution of fluid instabilities in ICF experiments [56,57] or UCNP expansion into a vacuum [29]. Strongly coupled electrons, which are difficult to create at high densities because of degeneracy, have been of theoretical and experimental interest for several decades [21,22], including, more recently, for their role in the conductance of liquid-helium surfaces [23]. Finally, such an approach could also serve as a platform for measuring coupled electron-ion modes, which have been of recent interest in dense two-temperature plasmas [58]. In fact, isolated experiments at these intermediate densities have been performed successfully [59-61]; however, controllability and tunability of plasma properties were not the focus of those experiments. Here, we pr...

Stability of the helium atom embedded in classical nonideal plasmas

“…0, that is, in the weak limit of non-ideality. The pseudopotential (2) has been used in a number of studies relating to CNP [32][33][34][35]. In this paper, we use the pseudopotential (2) to describe the interaction potential among the charged particles in He embedded in CNP.…”

“…The pseudopotential (2) has been used in a number of studies relating to CNP [32][33][34][35]. In this paper, we use the pseudopotential (2) to describe the interaction potential among the charged particles in He embedded in CNP. At this point it is pertinent to mention that the pseudopotential (2) is static in nature, that is, it does not takes into account the effects of motion of the charges concerned.…”

“…Knowledge on the nonideality (NI) of plasma is crucial for the interpretation of various phenomena associated with astrophysics, plasma physics, exploding wires, x‐ray free electron laser experiments, inertial‐confinement fusion experiments and condensed matter [1, 2]. In particular, it plays an essential role in the understanding of the evolution of stars and planets whose cores prevail in the state of nonideal plasmas [1].…”

Helium atom embedded in non‐ideal classical plasmas: Doubly excited singlet S states

“…In recent years, a number of theoretical investigations have been carried out to explore the effects of NI of the classical plasmas on the structural and collisional behaviour of atomic systems. [ 5,8–22 ]…”

Stability of hydrogen molecular ion in non-ideal classical plasmas

“…In fact, detailed knowledge on the NI is important to improve our understanding about stellar evolution [14]. Beside this, physics of non-ideal plasmas plays important roles in the explanation of various phenomena attached to plasma physics [15], inertial fusion [16], x-ray free electron laser [17], exploding wires [18] and condensed matter [19]. Baimbetov et al [7] deduced a pseudopotential for non-ideal classical (non-degenerate) plasmas from the Bogolyubov equations.…”