Density and potential wake past an insulating obstacle in a partially magnetized flowing plasma

TL;DR

This study investigates how an insulating obstacle affects plasma potential and density in a partially magnetized flow, revealing off-centered potential minima and ion focusing influenced by magnetic field strength.

Contribution

It provides new experimental insights into plasma wake behavior around obstacles and introduces a phenomenological model to explain observed potential and density profiles.

Findings

Potential minima shift off-center near the obstacle edge

Ion focusing occurs around the obstacle edge

Magnetic field strength influences drift velocity and potential depth

Abstract

The radial characteristics of plasma potential and density around an insulating disc obstacle, placed inside a partially magnetized plasma flow created in cylindrical chamber by hot cathode filament are presented. In the absence of obstacle, centrally sharp minima in potential and maxima in plasma density is observed; however when a macroscopic obstacle is introduced in plasma flow, a clear radially off-centred minima in plasma potential is observed having plasma density peaking near the edge of the obstacle. The depth of potential around the obstacle depends on the axial magnetic field strength. This off-centred radial potential profile in the plasma flow gives rise to focusing of ions around the obstacle edge. Experimentally it is found that the drift velocity of focused positive ions is directly depended on the magnetic field strength and axial positive ion flow velocity. A phenomenological model based on short-circuiting effect is applied to explain the plasma density and potential in the wake region.