Observation and Analysis of Paired-Particle Motions in Fine-Particle Plasma

We found that steady-state paired-particle motion was often observed in a fine-particle cloud in the argon plasma produced by a 100-kHz high-frequency discharge. Monodispersed spherical silica particles with a diameter of 5.0 μm were trapped in the plasma. The 2-D motion of these charged particles was carefully recorded using a microscope camera, and their orbits and perturbation frequencies were analyzed. The loci and fast Fourier transform spectra of many paired particles were obtained. By moving the camera horizontally, 3-D images of the particles were recorded, and a 3-D map of the positions of charged particles was obtained. It is considered that the forces inducing the paired-particle motion were generated by the Debye shielding and the electric field surrounding the paired particles.