Enhanced entropy production in heat-flux-driven plasma sheath

TL;DR

This paper investigates how controlling heat flux and ion Mach number influences plasma sheath behavior, revealing that exceeding a heat flux threshold significantly increases ion temperature contrast and entropy production.

Contribution

It introduces a method to analyze the nonlinear coupling of energies in plasma sheath by solving boundary-dependent equations for ion temperature and potential.

Findings

Heat flux control affects plasma sheath profiles.

Exceeding heat flux threshold enhances entropy production.

Ion temperature contrast increases with heat flux.

Abstract

The plasma sheath sets a stage for a strongly nonlinear coupling of the thermal, kinetic, and electric energies of plasma in a non-equilibrium, open environment. The pressure, velocity, and electrostatic potential profiles depend strongly on the boundary condition given on the internal side (pre-sheath). By controlling the boundary values of the heat flux and the ion Mach number, we solve a set of equations for the ion temperature and the electrostatic potential. The boundary values of the ion velocity and the electrostatic potential vary due to the change of the boundary ion temperature. When the heat flux exceeds a threshold value (determined by the ion Mach number), the temperature contrast is enhanced, resulting in a large entropy production.