Probing the plasma sheath confinement in a glass box with a microparticle

Vertical dust chains levitating in the plasma sheath have proven to be convenient systems to investigate topics such as low-dimensional transport, particle–particle interactions and ion wake formation. In the presence of gravity, these types of vertical dust structures can be formed by placing a glass box on the lower electrode of a modified gaseous electronics conference radio frequency reference cell. However, the manner in which the glass box impacts the electric field and provides confinement for the particle is not yet well understood. In this work, a single micrometer-sized dust particle is used to experimentally probe the plasma sheath in a glass box. Both the horizontal and vertical components of the confining electric force are determined using laser excitation measurements and bias pulse-excited oscillation measurements. At low powers, the combination of an increased levitation height and a decreased gradient in the vertical electric force is expected to cause the formation of vertical particle chains. The horizontal confinement close to the center of the box does not depend on the plasma power. These results lead to an increased understanding of the confining forces provided by a glass box, which are key for future analysis of dynamics and interaction of dust structures in the same environment.