A dust particle based technique to measure potential profiles in a plasma

A novel technique to measure potential profiles in a plasma based on the visualization of charged tracer dust particles is reported. The method is used to experimentally determine the potential around a grounded wire that is mounted on the cathode of a DC glow discharge Argon plasma produced in a $\Pi$--shaped Dusty Plasma Experimental (DPEx) device. The tracer particles, consisting of a few micron sized mono-dispersive Melamine Formaldehyde (MF) grains, are made to flow over the grounded wire by suitable variations in the background gas flow. By a visual tracking of the individual particle trajectories, that yields their positions and velocities at various times, the potential values at these positions are directly estimated by using energy conservation arguments. The results agree very well with conventional probe based measurements. The technique is free of some of the inherent limitations of probe based diagnostics and offers a direct and minimally invasive means of visualizing potential profiles in a plasma.

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