Trade-off in perpendicular electric field control using negatively biased emissive end-electrodes

TL;DR

This paper investigates how negatively biased emissive electrodes influence perpendicular electric field control in magnetized plasma, revealing a trade-off between field uniformity and amplitude due to thermionic emission effects.

Contribution

It provides a detailed analysis of the effects of thermionic emission on plasma potential and electric field control, highlighting the trade-offs involved.

Findings

Thermionic emission improves sheath edge potential control.

Emission increases plasma potential drop along magnetic field lines.

A trade-off exists between electric field uniformity and amplitude.

Abstract

The benefits of thermionic emission from negatively biased electrodes for perpendicular electric field control in a magnetized plasma are examined through its combined effects on the sheath and on the plasma potential variation along magnetic field lines. By increasing the radial current flowing through the plasma thermionic emission is confirmed to improve control over the plasma potential at the sheath edge compared to the case of a cold electrode. Conversely, thermionic emission is shown to be responsible for an increase of the plasma potential drop along magnetic field lines in the quasi-neutral plasma. These results suggest that there exists a trade-off between electric field longitudinal uniformity and amplitude when using negatively biased emissive electrodes to control the perpendicular electric field in a magnetized plasma.