Study Of Mach Cones In 2D Dusty Plasmas

Dusty, or complex, plasma is an ionized gas in which submicron-to-micron sized particles, usually called dust grains, are embedded. Dusty plasmas occur widely in astrophysical environments, as well as in the laboratory settings where they allow direct optical imaging of particle motion in real time. In recent years, the research field of dusty plasmas has seen a sustained rapid growth all over the world. However, people pay attention to it with completely different purposes. In the fusion energy schemes and semiconductor manufacturing, people study dusty plasmas to prevent them as well as to control their motion due to the unexpected influence from the charged particles. Whereas in astrophysical environment and laboratory settings, the existence of charged particles often brings us new and surprising phenomena, among which the observation of the Mach cones in laboratory should be one of the most typical one.The present thesis aims mainly at studying Mach cones in 2D dusty plasma. Firstly, in the second chapter, hydrodynamics description and the quasilocalized charge approximation (QLCA) theory of 2D dusty plasma are used to study the interactions of respectively weakly coupled and strongly coupled dusty plasmas with a test charge. The results show that the test charge excites a V-shaped disturbance of induced potential or so-called Mach cone in the dust layer, while the test particle itself loses it energy. The stopping power of the test particle is found to depend complicatedly on the speed, the height of the test particle, as well as discharge pressures and the property of dusty plasma. In particular, it is found that the strong coupling effect will greatly enhance the stopping power. Furthermore, good agreement is found between the QLCA and MD results when the projectile-dust coupling is weak.Secondly, a hydrodynamic model is proposed to study the laser excited Mach cones in a 2D magnetized dusty plasma, with particular attention being paid to the effect of the magnetic field on the structure of Mach cones. Numerical results for the density perturbation of dust particles exhibit asymmetric Mach cones due to the existence of the constant magnetic field pointing perpendicular to the monolayer of dust particles. It can be found that the asymmetric Mach cones exist in cases of both subsonic and supersonic excitations, and the magnetic field seems to have stronger influence on Mach cone of small Mach number.