A dust particle based technique to measure the potential profile in a plasma

We present the experimental measurement of the potential profile around a wire attached to a grounded cathode in a DC glow discharge Argon plasma by using dust particles as dynamical micro-probes. The experiments are performed in a Π shaped Dusty Plasma Experimental device, in which the plasma is produced by applying a DC voltage between a circular anode and a grounded tray cathode. A few Melamine formaldehyde (MF) particles are then introduced in the plasma and are seen to be levitated in the cathode sheath region. These particles are made to move over the grounded wire by suddenly changing the flow rate of argon gas. Tracing the position of individual particles and calculating their velocities, the sheath potential profile is estimated over a wide range of discharge parameters using energy conservation arguments. The potential profiles are found to be Gaussian in axial direction whereas it is parabolic in the radial direction for a given discharge condition. The maximum potential strength increases whereas the width of the potential hill decreases with the increase of the discharge voltage and the background neutral gas pressure. (author)