The demonstration and classification of photo-discharging silica particles in complex plasmas

The study of complex plasmas is critical to our understanding of how contamination by dust affects the background conditions and processing techniques of practical plasmas. Studies into complex plasmas are limited due to the direct coupling of contaminating microparticle properties, such as charge, to the surrounding plasma conditions, which makes the control of these charged microparticles difficult. Previous studies at the Auburn Magnetized Plasma Research Laboratory (MPRL) have demonstrated that charged microparticles of lanthanum hexaboride (LaB6) can be photo-discharged by a near-ultraviolet (NUV) source, with minimal perturbation of the surrounding plasma. Preliminary tests indicated that silica microparticles, a common contaminant for practical plasmas, would exhibit a similar response to the NUV source as well. Probe measurements and video footage of variably sized silica microspheres exposed to NUV pulses while suspended in an RF argon plasma were collected and are presented. Langmuir probe data and video footage is analyzed to determine the effect of the NUV source on the equilibrium charge of the silica particles. The prospect of a reproducible technique using an NUV source to photo-discharge silica, and other contaminating microparticles, is discussed.