Dust Effects on Surface Charging in Plasmas: Laboratory and Numerical Investigations

Wednesday, 17 December 2014
Joseph Wang, Kevin Chou, William Yu and Daoru Han, University of Southern California, Los Angeles, CA, United States
There are many situations that a spacecraft surface would be covered by a layer of dusts, such as that around a comet and and on the surfaces of the Moon and asteroids. Previous studies of surface charging in plasmas have mostly considered a “clean” conducting or dielectric surface. On the other hand, studies of dust charging in plasmas have mostly considered that of single, isolated dust grains (the “dust-in-plasma” condition), where a dust grain is electrically isolated from its neighboring dusts. This paper considers the charging of a surface covered by a layer of dust grains (the “dusty-surface” condition), where the inter-dust distance is almost zero but the dust grains do not form a solid surface. Under such a condition, the sheath of each individual dust particles overlap to form one single sheath and the charging of individual dust grains is strongly affected by that of the neighboring dust grains and the surface.

Experiments and numerical simulations are carried out to understand the charging of both conducting and dielectric dusty surfaces. Surface charging measurements will be presented for different dust layer thickness, dust grain size, dust density, and different ambient plasma conditions. The effect of the existence of a dusty layer on surface potential as well as the difference between charging of a single dust-in-plasma and that of a dust grain as part of a dusty surface will also be discussed.