# Size and Density Evolution of a Single Microparticle Embedded in a Plasma

## TL;DR

This paper introduces two measurement techniques to track the size and density evolution of a single dust particle in plasma, revealing surface etching effects and density changes over time.

## Contribution

It presents novel methods combining microscopy and resonance measurements to analyze particle size and density evolution during plasma exposure.

## Key findings

- Significant decrease in particle mass density due to plasma etching.
- Surface roughness and core-shell structure influence particle properties.
- Density reduction is supported by multiple imaging techniques.

## Abstract

This article presents two measurement techniques to determine the diameter of a single dust particle during plasma operation. Using long-distance microscopy (LDM), the particle is imaged from outside the plasma chamber. In combination with phase-resolved resonance measurements the development of the volume-averaged particle mass density is measured over several hours. The measurements show a significant decrease of mass density for polymethyl methacrylate (PMMA) particles due to a plasma etching process on the surface. This is explained by a core-shell model and is supported by a surface roughness effect seen in the LDM images, an out-of-focus imaging of the angular Mie scattering pattern and ex-situ laser scattering microscopy measurements.