Plasma adiabatic lapse rate

TL;DR

This paper derives a plasma analog of the adiabatic lapse rate, revealing a new temperature gradient source in ion mixtures that impacts inertial confinement fusion simulations.

Contribution

It introduces a novel plasma temperature gradient mechanism in ion mixtures and derives related thermodiffusion coefficients, highlighting effects not captured by existing models.

Findings

New plasma temperature gradient proportional to concentration and ionization difference

Potentially significant effects in plastic ablators for fusion

Derived plasma thermodiffusion coefficients and charge-state diffusion predictions

Abstract

The plasma analog of an adiabatic lapse rate (or temperature variation with height) in atmospheric physics is obtained. A new source of plasma temperature gradient in a binary ion species mixture is found that is proportional to the concentration gradient and difference in average ionization states . Application to inertial-confinement-fusion implosions indicates a potentially strong effect in plastic (CH) ablators that is not modeled with mainline (single-fluid) simulations. An associated plasma thermodiffusion coefficient is derived, and charge-state diffusion in a single-species plasma is also predicted.