Observation of microparticle gyromotion in a magnetized DC glow discharge dusty plasma

Summary form only given. Laboratory observations of the motion of charged microparticles have been made in an argon DC glow discharge plasma created within a strong DC magnetic field. The experimental configuration consists of an anode-cathode pair centered between a pair of neodymium iron boride permanent magnets. The cylindrical axis of the resulting plasma column is directed vertically (i.e., along the direction of the gravitational force). Depending upon the orientation of the magnets, the magnetic field can be directed either upward or downward, with a field strength of approximately 2.5 kG. A pair of Helmholtz magnetic field coils external to the vacuum chamber allows the magnetic field to be varied by approximately /spl plusmn/75 G in the experimental region. Alumina microparticles (/spl sim/1.2 /spl mu/m) placed directly on the grounded cathode provide the source of charged dust in the plasma. Individual dust grains suspended in the plasma can be observed moving in an oscillatory fashion. Measurements of the oscillation frequency, spatial amplitude, and scalings with magnetic field strength and transverse particle velocity have been made. The measurements are consistent with the expected gyromotion of magnetized dust grains under the ambient plasma conditions and the data are shown to provide an effective method for the noninvasive determination of the dust grain charge.