Axisymmetric magnetic field effects on hollow cathode generated plasma column in APPEL-device

TL;DR

This study investigates how an axisymmetric magnetic field influences the formation and confinement of a plasma column generated by a hollow cathode discharge, combining experimental diagnostics and fluid simulations.

Contribution

It provides new insights into magnetic confinement effects on hollow cathode plasma columns through combined experimental and simulation approaches.

Findings

Energetic electrons concentrate near the source and converge along the axis.

Plasma length inversely correlates with electron-neutral collision frequency.

Fluid simulations qualitatively match experimental electron distribution trends.

Abstract

An elongated plasma column has been successfully generated and sustained in a linear plasma device using a hollow cathode discharge in the presence of an axisymmetric magnetic field. The confinement of cold energetic electrons produced near the hollow cathode plays a crucial role in guiding the plasma along the device axis. Experimental diagnostics reveal a high concentration of energetic electrons in the peripheral region near the source, which progressively converge toward the axis at a downstream location approximately 3.0 meters from the cathode. The length of the plasma column exhibits an inverse relationship with the electron-neutral collision frequency, indicating the significance of collisional damping in the propagation of energetic electrons. These observations are further supported by fluid simulations performed using COMSOL Multiphysics, which qualitatively reproduce the experimental trends. The results are consistent with a theoretical model previously proposed by the authors, reinforcing the understanding of energetic electron behaviour in magnetically guided plasma columns.