Abstract
Shock-driven hydrodynamic instabilities in a plasma usually lead to interfacial mixing and the generation of electromagnetic fields, which are nonequilibrium processes coupling kinetics with meso- and macroscopic dynamics. The understanding and modeling of these physical processes are very challenging tasks for single-fluid hydrodynamic codes. This work presents a new framework that incorporates both kinetics and hydrodynamics to simulate shock waves and hydrodynamic instabilities in high-density plasmas. In this hybrid code, ions are modeled using the standard particle-in-cell method together with a Monte Carlo description of collisions while electrons are modeled as a massless fluid, with the electron heat flux and fluid–particle energy exchange being considered in the electron pressure equation. In high-density plasmas, Maxwell’s equations are solved using Ohm’s law instead of Ampère’s law. This hybrid algorithm retains ion kinetic effects and their consequences for plasma interpenetration, shock wave propagation, and hydrodynamic instability. Furthermore, we investigate the shock-induced (or gravity-induced) turbulent mixing between a light and a heavy plasma, where hydrodynamic instabilities are initiated by a shock wave (or gravity). This study reveals that self-generated electromagnetic fields play a role in the formation of baroclinic vorticity along the interface and in late-time mixing of the plasmas. Our results confirm the ability of the proposed method to describe shock-driven hydrodynamic instabilities in a plasma, in particular, nonequilibrium processes that involve mixing and electromagnetic fields at the interface.
Highlights
INTRODUCTIONScitation.org/journal/mre hohlraum wall/gas interface, the standard single-fluid descriptions are inadequate
In inertial confinement fusion (ICF),1 understanding and suppressing shock-driven hydrodynamic instabilities2,3 and the ion mix4,5 are crucial for achieving ignition
We present a fundamental study of shock-driven instabilities, which indicates that hydrodynamic instabilities could be more harmful to ICF than predicted by hydrodynamic simulations: the increased ion mix can enhance thermal energy loss and reduce the implosion performance in ICF, and the distortion of the transmitted shock wave may affect shock convergence in the ICF implosion
Summary
Scitation.org/journal/mre hohlraum wall/gas interface, the standard single-fluid descriptions are inadequate. Fully kinetic simulation methods, such as standard PIC and Fokker–Planck codes, are computationally expensive because they need to resolve the plasma frequency ωpe 4πnee2/me.11 In these regimes, electromagnetic hybrid fluid–PIC codes (in which ions are treated as particles and electrons as constituting a massless fluid) are more reliable and adaptable tools for investigating such complex kinetic plasma behavior. Electromagnetic hybrid fluid–PIC codes (in which ions are treated as particles and electrons as constituting a massless fluid) are more reliable and adaptable tools for investigating such complex kinetic plasma behavior This hybrid approach is valid because the simulation time is much longer than the relaxation time of electron–electron collisions and the simulated plasma scale is much larger than the Debye length of the plasma. This should provide motivation for future studies of shock-driven hydrodynamic instabilities under more realistic plasma conditions
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