Orbital-motion-limited theory of dust charging and plasma response

摘要

The foundational theory for dusty plasmas is the dust charging theory thatprovides the dust potential and charge arising from the dust interaction with aplasma. The most widely used dust charging theory for negatively charged dustparticles is the so-called orbital motion limited (OML) theory, which predictsthe dust potential and heat collection accurately for a variety ofapplications, but was previously found to be incapable of evaluating the dustcharge and plasma response in any situation. Here we report a revised OMLformulation that is able to predict the plasma response and hence the dustcharge. Numerical solutions of the new OML model show that the widely-usedWhipple approximation of dust charge-potential relationship agrees with OMLtheory in the limit of small dust radius compared with plasma Debye length, butincurs large (order-unity) deviation from the OML prediction when the dust sizebecomes comparable with or larger than plasma Debye length. This latter case isexpected for the important application of dust particles in a tokamak plasma.