Charging in a dusty plasma with a size distribution: A comparison of three models

There has recently been a renewed interest in the charging of dust grains in a plasma and its effect not only on dust dynamics in astrophysical and solar system environments but also in laboratory plasma processing and semiconductor manufacturing. The calculation of individual dust grain charges in a dust cloud with a size distribution is a challenging one, especially under sufficiently dense cloud conditions and moderately high plasma temperatures when secondary electron currents become significant. Both the capacitance of the dust cloud and the significant charging currents must be taken into account. Three models for calculating individual dust grain charges are compared. The first model considers the dust cloud to consist of isolated grains immersed in plasma. The second model uses a uniform potential for the dust cloud and thus finds the charges using an appropriate capacitance for the cloud. The third model assumes a nonuniform grain surface potential and uses a solution to Poisson's equation to calculate the grain charges. The models are applied to a dense dusty plasma environment, appropriate for Saturn's F-ring. The implications for coagulation in presolar environments are also discussed. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.