Dust interferometers in plasmas

TL;DR

This paper introduces an interferometric imaging method for real-time measurement of dust particle sizes in plasmas, utilizing fringe patterns on defocused images to determine diameters of spherical particles and their agglomerates.

Contribution

The novel technique enables instant size measurement of dust particles in plasma using fringe analysis, applicable in both terrestrial and microgravity environments.

Findings

Fringe patterns correlate with particle size above a critical diameter.

Rotational fringe patterns allow size measurement of binary agglomerates.

A lower size limit exists below which fringe patterns are not observed.

Abstract

An interferometric imaging technique has been proposed to instantly measure the diameter of individual spherical dust particles suspended in a gas discharge plasma. The technique is based on the defocused image analysis of both spherical particles and their binary agglomerates. Above a critical diameter, the defocused images of spherical particles contain stationary interference fringe patterns and the fringe number increases with particle diameters. Below this critical diameter, the particle size has been measured using the rotational interference fringe patterns which appear only on the defocused images of binary agglomerates. In this case, a lower cut-off limit of particle diameter has been predicted, below which no such rotational fringe patterns are observed for the binary agglomerates. The method can be useful as a diagnostics for complex plasma experiments on earth as well as under microgravity condition.