Study On Density Wave In A Binary Complex Plasma

As a new research topic,complex plasma experiment is attracting more and more attention of researchers.With the discovery of various physical phenomena in the complex plasma system,the unique advantages of this method have been highlighted as a medium that can simulate the physical properties from the molecular level.Experimental studies have evolved from ground-based experiments to the complex plasma experiments under microgravity environment,from singular systems to binary and multivariate systems.The research of PK-3 Plus,a classic experimental device on board the International Space Station,has provided many new perspectives for the researchers in physics,such as lattice,density wave and phase separation.In the experiment,the wave propagation phenomena are unintentionally discovered,and these waves are generated by self-excitation,which leads to the experimental exploration of the selfexcited density wave of complex plasmas.Under certain experimental conditions,the existence of free energy is a prerequisite for excitation of density waves.The propagation of waves in the onecomponent complex plasma system can cause phenomena such as rupture and bifurcation of corrugations.Studies of these phenomena at microscopic level play an important role in the interpretation of many macro-phenomena.In a binary complex plasma system with two types of particles of different size,the smaller particles will occupy the inner space of the dust cloud,while the larger particles occupy the outside.There is a clear interface between the contact surfaces of the two particles,exhibiting a phase separation.The propagation direction of the density wave spreads from the void in the middle of the dust cloud to the surrounding sphere.When the wave propagates from the inner space of the small particle with a certain frequency,it will collide with the wave propagating in the large particle.As a result,the wave propagation in the opposite direction back to the inner space where the small particles are located.The wave with a frequency of small particles spreads to the outer part.This wave is gradually dissipated.In order to verify the existence of reflected waves,we identify the particles,making a periodic kinetic energy map of particles.On the other hand,in order to understand the kinetic process of the medium,we tracked the individual particles.We found that between two wave fronts in the periodogram,the big particles vibrate one period and small particles vibrate two periods with different amplitudes.It seems that the vibration form of the particle is affected by the wave.When a form of wave propagates into the medium in the positive direction,the medium exhibits the frequency and the energy of the wave(Amplitude),and then another wave(the reflected wave in the experiment)propagates to the medium,the incident wave and the reflected wave are coupled and it shows the characteristics of both waves.The whole process is a good illustration of the characteristics of wave propagation on the interface and the role of the medium in the process of wave propagation.