Observation of spatio-temporal pattern in magnetised rf plasmas

TL;DR

This paper reports the experimental observation of concentric ring patterns in a magnetised rf plasma, which can trap dust particles and be used to measure electric fields, revealing complex spatiotemporal structures.

Contribution

It presents the first experimental observation of radial ring patterns in magnetised rf plasma and introduces a novel technique to measure associated electric fields.

Findings

Concentric rings form and propagate radially in the plasma.

Patterns trap dust particles, enabling electric field measurement.

Various characteristic structures appear under different discharge conditions.

Abstract

We address an experimental observation of pattern formation in a magnetised rf plasma. The experiments are carried out in a electrically grounded aluminium chamber which is housed inside a rotatable superconducting magnetic coil. The plasma is formed by applying a rf voltage in parallel plate electrodes in push-pull mode under the background of argon gas. The time evolution of plasma intensity shows that a homogeneous plasma breaks into several concentric radial spatiotemoral bright and dark rings. These rings propagate radially at considerably low pressure and a constant magnetic field. These patterns are observed to trap small dust particles/grains in their potential. Exploiting this property of the patterns, a novel technique to measure the electric field associated with the patterns is described. The resulting estimates of the corresponding field intensity are presented. At other specific discharge parameters the plasma shows a range of special type of characteristic structures observed in certain other chemical, mechanical and biological systems.