The properties of plasma sheath containing the primary electrons with a Cairns-distribution

TL;DR

This paper investigates the effects of non-thermal primary electrons with a Cairns-distribution on plasma sheath properties, deriving new criteria and showing significant dependence on the non-thermal parameter.

Contribution

It introduces a generalized Bohm criterion and floating potential considering non-thermal primary electrons, highlighting differences from Maxwellian assumptions.

Findings

Sheath properties depend strongly on the a-parameter of the Cairns-distribution.

Derived new Bohm criterion and floating potential expressions.

Identified significant deviations from Maxwellian-based sheath models.

Abstract

We study the properties of plasma sheath containing the cold positive ions, the secondary electrons, and the primary electrons with a Cairns-distribution (a non-thermal velocity-distribution). We derive the generalized Bohm criterion and Bohm speed, the new floating potential at the wall, and the new critical secondary electron emission coefficient. We show that these properties of the plasma sheath depend significantly on the a-parameter in the non-thermal a-distribution, and so they are generally different from those of the plasma sheath if the primary electrons were assumed to be a Maxwellian distribution.