J. Plasma Fusion Res. SERIES, Vol.4 (2001) 4834g6 Control of Rotational Motion of Fine-Particle Gloud Confinedin a weakly-Magnetized Dc Discharge prasma

A rotation of strongly-coupled fine-particle cloud, levitating above a negatively biased electrode, is observed in a weakly ionized argon dc discharge plasma by applying axial magnetic field in vertical direction ' when the magnetic field is applied, fine-particle cloud, constituting multilayers like the Coulomb lattice in vertical direction, start to rotate in azimuthal direction with keeping the interparticle distance almost constant. The rotation direction of fine-particle cloud is controlled by changing radial plasma density profile. In case ofpeaked-type density profile, the rotation direction is paramagnetic of negatively-charged fine particles. conversely, in case of hollow-type density profile, the rotation direction is diamagnetic. A mechanism of the rotation is explained by an effect of ion motion colliding with fine particles in the presence of vertical magnetic field. Keywords: dc discharge plasma, dusty plasma ' strongly-coupled fine particles, magnetic field, rotation, plasma density profile, ion drag force 1