Search

The excitation and propagation of solitary waves is studied experimentally in a two-dimensional strongly coupled dusty (complex) plasma. A single layer with ≈5000 microspheres (8 μm diam) was suspended in an argon plasma with a neutral gas pressure of 3.0 mTorr. The measured Debye shielding parameter was κ≈1.6, where κ=a/λ is the ratio of the lattice constant a to the Debye length λ. Nonlinear, planar longitudinal waves were launched by pushing all the particles in a rectangular region at the center of the crystal in the same direction using an 18 W green laser. Compressive solitary waves with density perturbations δn/n0≲0.8 and widths ≲5a were found to propagate in the forward direction at speeds exceeding the dust acoustic speed. For small amplitude solitary waves, the relations between amplitude, width, and velocity are consistent with those predicted for Korteweg–deVries solitons. Rarefactive perturbations were not observed to evolve into solitary waves. However, oscillatory shocks were seen to move in the backward direction after the laser force was removed. [ABSTRACT FROM AUTHOR]

The propagation of transverse waves in a two-dimensional particle suspension in a plasma is studied in the solid and liquid phase. The different states of the suspension are realized by raising the kinetic temperature of the dust particles with a new laser method. An additional laser beam is used to excite shear waves and the wave is observed by videomicroscopy in terms of the individual velocities of the dust particles. For recovering the spatial wave patterns the method of singular value decomposition is applied and compared with the method of spatial Fourier analysis of complex wave numbers. In the solid phase, weakly damped waves are found which follow the expected dispersion relation. In the liquid phase the existence of strongly damped waves is demonstrated. The real part of the wave number is in overall agreement with the predictions of the Quasi Localized Charge Approximation model for a two-dimensional system. The damping of the waves is discussed. [ABSTRACT FROM AUTHOR]