Head-on collision of dust-acoustic solitons in a strongly coupled dusty plasma

The collision between two counterpropagating dust acoustic solitary waves in a strongly coupled dusty plasma has been observed. The measured velocity and width of the solitary wave agree with the solution of the Korteweg–de Vries equation derived by using the generalized hydrodynamic model. The two counterpropagating solitary waves of equal amplitude merge into a single pulse with twice the individual soliton amplitude and then pass through each other. The solitons suffer a small time delay in propagation after collision. The measured delay time obtained from their trajectories is also presented.

Figure 1

Schematic of the experimental setup. G: graphite plate; E1 and E2: exciters; D: dust particles; F: fence; B: buzzer; C: camera; and L: laser. To excite the linear dust acoustic wave, a continuous sinusoidal signal is applied to E1. For the excitation of single DASW a negative pulse is applied to E1. E2 and the remaining part of the plate are grounded.

Figure 2

Examples of images recorded at different times (after the video recording starts) showing the propagation of a compressional wave excited by a −5 V pulse. Top image shows the undisturbed particles just before excitation. The compression is identified as a dense and bright region of particles. Two bright vertical lines appearing to the left of each image are the two edges of exciter E1.

Figure 3

Spatial evolution of the DASW. Normalized pixel intensity (0.05 per division) versus distance plot of the images recorded at different times. The amplitude of the excitation pulse is −5 V.

Figure 4

Plot of (a) Mach number and (b) width of the DASW versus wave amplitude. Theoretical values are represented by solid curves.

Figure 5

An example of a pixel intensity profile at different times showing a collision between two counterpropagating DASWs marked as A and B excited by a −10 V pulse. The peaks of the outgoing solitary waves are identified as ${\mathrm{A}}^{\prime }$ and ${\mathrm{B}}^{\prime }$. Positions $x$ = 0 and 5.7 cm correspond to the inner edges of E1 and E2, respectively.

Figure 6

Trajectories of incoming and outgoing DASWs corresponding to excitation voltage (a) −15 V, (b) −10 V, and (c) −8 V. Observed trajectories represented by open circles for soliton A and filled circles for soliton B are fitted to straight lines. The time difference between the intersecting points of incoming and outgoing trajectories is the delay time Δ$t$ (indicated by the horizontal solid line).