CENTRAL COLLISIONS OF CHARGED DUST PARTICLES IN A PLASMA

Elastic dust particle particle interaction in an rf plasma provides a charge measurement method independent of the knowledge of plasma param eters. Assuming a screened Coulomb potential surrounding each particle with a constant charge at fixed plasma conditions, the charge and the screening length can be calculated from the trajectories of two colli ding particles. With this method, we determine the charge and screenin g length of dust particles in the sheath of an rf discharge. The metho d can also be used to determine plasma parameters taking the dust part icles as local probes.