Reflection of a dust acoustic solitary wave in a dusty plasma.

We report the first experimental observations of the reflection of a dust acoustic solitary wave from a potential barrier in a dusty plasma medium. The experiments have been carried out in an inverted $\Pi$-shaped Dusty Plasma Experimental (DPEx) device in a DC glow discharge plasma environment. The dust acoustic solitary wave is excited by modulating the plasma with a short negative Gaussian pulse that is superimposed over the discharge voltage. The solitary wave structure is seen to move towards a potential barrier, created by the sheath around a biased wire, and turn back after reflecting off the barrier. The amplitude, width, and velocity of the soliton are recorded as a function of time. The experiment is repeated for different strengths of the potential barrier and for different initial amplitudes of the solitary wave. It is found that the distance of the closest approach of the solitary wave to the centre of the barrier increases with the increase of the strength of the potential barrier and with the decrease of the initial wave amplitude. An emissive probe is used to measure the sheath potential and its thickness by measuring the plasma potential profile in the axial direction over a range of resistances connected to the biased wire. A modified Korteweg de Vries equation is derived and numerically solved to qualitatively understand the experimental findings.