Dust plasmas have received considerable attention in recent years due to the fact that a kind of crystal could be established, which is a typical example of an ideal material. In this system, the dust particles are often confined upon a three-dimensional sheath of an axissymmetric concave electrode, where the axial electrostatic force balances the gravitation and the radial electrostatic force keeps the dust from running away horizontally. In this paper, a threedimensional sheath structure is simulated through a liquid model, and the movement of the dust particles is simulated via the dynamic method. The crystals are obtained self consistently. The effect of both the electrode size and the mass of dust particles on the crystals are discussed. The simulation result demonstrates that two kinds of dust crystals could be established by varying the sheath diameter, and some proper conditions are necessary for the formation of a double layer dust crystal.
Numerical simulations based on the finite-difference-time-domain (FDTD) approximation to multi-fluid equations for positive ions, negative ions and electrons are used to study high frequency electromagnetic wave propagation and absorption in an unmagnetized plasma layer. The interaction between the incident high frequency wave and the plasma layer shows that the existence of negative ions and the nonlinear effect reduces the power absorption capability of the plasma. Parameter dependences of the effects are calculated and discussed.
