The Richtmyer–Meshkov instability of thermal, isotope and species interfaces in a five-moment multi-fluid plasma

Abstract

The Richtmyer–Meshkov instability (RMI) results from the impulsive acceleration of a density interface where either it or the acceleration is perturbed. Density interfaces may arise due to a change in gas species, isotope, temperature or a combination of these. We computationally investigate the effect of interface type on the plasma RMI, which is relevant for a range of applications, including inertial confinement fusion. We simulate the evolution of single-mode perturbed thermal, species and isotope interfaces in an ideal ion–electron plasma using the multi-fluid plasma (MFP) model. We find that, in the MFP model, the evolution of different types of interface differs significantly, in contrast to single-fluid models where they behave similarly if the Atwood number is matched. The thermal and species interfaces produce the most severe response to shock acceleration, experiencing the secondary instabilities and enhanced primary mode growth. The isotope interface evolution is restrained in comparison with the former cases, resembling the response predicted by single-fluid models. The determining factor in the severity of the MFP RMI is the density ratio across the initial interface in the electron fluid, which is unity for an isotope interface. We observe that, as the density ratio across the electron interface decreases, so do the magnitudes of the self-generated fields and consequently the severity of the growth amplification. Generally, the evolution of the RMI with different types of interface becomes more similar as the level of coupling between the ion and electron fluids is increased, characterised by reducing the plasma non-dimensional skin depth.

The magnetised plasma Richtmyer–Meshkov instability: elastic collisions in an ion–electron multifluid plasma

“…2017 b ; Tapinou et al. 2022), the primary mode and high-wavenumber secondary instabilities observed in those studies were suppressed (Tapinou et al. 2023).…”

“…2017 b ; Tapinou et al. 2022, 2023). Typically, kinetic models are not employed because of the expense required for simulating the problem scales.…”

“…Importantly, MFP theory distinguishes between the fundamental material interfaces present in an ICF plasma RMI, that are nearly indistinguishable by MHD and HMHD when the Atwood number is matched (Tapinou et al. 2022).…”

“…2021; Tapinou et al. 2022, 2023), though others include mixing in supersonic combustion (Yang, Kubota & Zukoski 1993; Yang, Chang & Bao 2014), astrophysical phenomena (Arnett et al. 1989; Arnett 2000), atmospheric sonic boom propagation (Davy & Blackstock 1971), driver gas contamination in reflected shock tunnels (Stalker & Crane 1978; Brouillette & Bonazza 1999), combustion wave deflagration-to-detonation transition (Khokhlov et al.…”

“…The three fundamental material interfaces (isotope, species and thermal RMI (Tapinou et al. 2022)) experience the phenomena above to varying extents. The isotope case has no density interface in the electron fluid and consequently produces a RMI most similar to the single-fluid limit.…”