Shock waves in dusty plasma

Dusty plasma is an attractive medium to study waves, and in particular, shock waves. The work reported in this thesis was on investigation of shock waves in two-dimensional dusty plasmas. I developed experimental methods for generating two types of shock waves: blast wave and continuously-driven shock wave, and demonstrated these methods in two experiments, each for the corresponding type of shock wave. The continuously driven shock experiment involved an exciter moving at a constant supersonic speed, analogous to a piston in a cylinder. The resulting compressional pulse was a shock that propagated steadily without weakening, ahead of the moving exciter. The propagation speed of such shock depends on the exciter speed. I obtained this dependence experimentally, in a strongly coupled dusty plasma that was prepared as a single two-dimensional (2D) layer of charged microparticles. I compared my experimental results to an empirical form Mshock = 1 + s Mexciter, and to the prediction of a recent simulation. The blast wave experiment in a 2D dusty plasma was based on an abrupt stop of the mechanical motion of the exciter. This advance allowed the generation of blast waves of variable amplitude and with a control of energy input into the system. An absence of decay of a shock wave's amplitude, which was previously reported by other authors in 3D dusty plasmas, was observed in the blast wave experiment. There are indications that this effect can be due to the Schweigert instability. The out-of-plane motion of microparticles, which is a necessary condition for the Schweigert instability, was detected with the help of the side-view camera. A method for improving the spatial resolution for obtaining density profiles of traveling shocks in two-dimensional dusty plasma experiments was developed. Using this method, the shock width was measured with sub-interparticle spacing accuracy, in the blast wave experiment. It was found that the typical shock width was of the order of 3 to 6 interparticle spacings, depending on the shock parameters. Shocks in two phases, solid and liquid, were produced and studied in the blast wave experiment. All parameters, except for the kinetic temperature, were the same for the liquid and solid. It was found that the shock thickness for the liquid phase is close to that of the solid phase but generally smaller. For a stronger shock, density oscillations behind the shock front were observed both for the liquid and solid phase.