Damped dust oscillations as a plasma sheath diagnostic

Dust can be suspended in a plasma sheath under certain conditions. An analy sis of the dust trajectory as it approaches its equilibrium suspension heig ht can provide a description of the spatial variation of the potential in t he sheath. We describe an experiment in which we track such trajectories an d calculate their oscillation frequencies, equilibrium heights and damping constants. These three measured parameters are then interpreted in such a m anner as to reveal the neutral drag force on the dust and the curvature of the sheath electric potential in which the dust moves. We then calculate th e charge on the dust particles suspended in the plasma sheath. We also show that, to a high degree of accuracy, the sheath potential predicted by seve ral numerical models in the literature as well as by our experimental resul ts is parabolic, i.e. the sheath field is quite linear.