Resolving the mystery of electron perpendicular temperature spike in the plasma sheath

Abstract

A large family of plasmas has collisional mean-free-path much longer than the non-neutral sheath width, which scales with the plasma Debye length. The plasmas, particularly the electrons, assume strong temperature anisotropy in the sheath. The temperature in the sheath flow direction ($T_{e\parallel }$) is lower and drops towards the wall as a result of the decompressional cooling by the accelerating sheath flow. The electron temperature in the transverse direction of the flow field ($T_{e\perp }$) not only is higher but also spikes up in the sheath. This abnormal behavior of $T_{e\perp }$ spike is found to be the result of a negative gradient of the parallel heat flux of transverse degrees of freedom ($q_{es}$) in the sheath. The non-zero heat flux $q_{es}$ is induced by pitch-angle scattering of electrons via either their interaction with self-excited electromagnetic waves in a nearly collisionless plasma or Coulomb collision in a collisional plasma, or both in the intermediate regime of plasma collisionality.

References in corpus (5)

• Suppression of electron thermal conduction by whistler turbulence in a sustained thermal gradient
• Vlasov Simulation of Emissive Plasma Sheath with Energy-Dependent Secondary Emission Coefficient and Improved Modeling for Dielectric Charging Effects
• Bohm criterion of plasma sheaths away from asymptotic limit
• Continuum kinetic investigation of the impact of bias potentials in the current saturation regime on sheath formation
• On the collisional damping of plasma velocity space instabilities

Cited by in corpus (2)

• Scaling laws for electron kinetic effects in tokamak scrape-off layer plasmas
• Continuum kinetic investigation of the impact of bias potentials in the current saturation regime on sheath formation