Recently, behavior of dust particles in the several kinds of plasma sources such as DC and RF discharges has been attractively studied. Particularly, the parallel plate RF plasma has been often applied in experiments on dusty plasma such as the coulomb crystal [1]-[3]. The wake potential, which is formed by the interaction between charged dust particle and ion flow in the sheath, seems to strongly affect the vertical structure formation of the coulomb crystal. On the other hand, in the ion sheath of the DC plasma[4]-[6], the charged dust particles form the Coulomb crystal horizontally, but they are hard to line up vertically without strongly magnetic or electrostatic field. In this work, we carry out the separate operation of dust levitation and plasma production using the ring-shaped RF antenna for understanding it's phenomena more clearly. The experiments are performed in the stainless chamber with 30cm in diameter and 40cm in height. Ring-shaped RF antenna with a inner diameter of 18 cm was located the center of the chamber to coupled RF power supply of 13.56 MHz through the matching network. Typical plasma parameter were n_e ~ 10⁹cm^-3 and T_e ~ 3eV for RF power of 40W and Ar gas at 5 Pa. The negative biased electrodes, located at 4cm down from the ring antenna, were composed of the disk electrode and ring electrode of 9cm in diameter for vertical and horizontally levitation control. Dust particles with about 10μm in diameter were dropped from a dust feeder located at 3cm up from the ring antenna. The observation of dust particles was carried out using the charge coupled device (CCD) camera with the microscopic lens, imaging the scattered light from the dust particles by the expanded semiconductor laser. The spatial structure of dust cloud was found to be flask shape above the disk electrode with the vertical length of 2-3cm and the horizontal width of 2-4cm. Levitation region, shape and dynamics of dust cloud were large influenced by the height of ring antenna from the disk electrode and other experimental configuration.

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