Grain charging in an intermediately collisional plasma

¹ Max-Planck-Institut für extraterrestrische Physik - D-85741 Garching, Germany, EU
² Royal Institute of Technology - Stockholm SE-100 44, Sweden, EU
³ Joint Institute for High Temperatures - 125412 Moscow, Russia

^a thoma@mpe.mpg.de

Received: 8 December 2011
Accepted: 22 December 2011

Abstract

The charges of μm-size particles in the quasineutral bulk plasma of a dc discharge are determined experimentally in a pressure range between 100 and 500 Pa, spanning the transition between the weakly collisional and highly collisional (hydrodynamic) regimes, where the ion mean free path drops below the plasma screening length. The charge is determined using the force balance condition from the measured particle drift velocities in stable particle flows. A simple interpolation formula for the ion flux to the grain in the transitional regime is shown to fit quite well the experimental results.