Kinetic modeling of Langmuir probe characteristics in a laboratory plasma near a conducting body

Abstract

Results are presented from kinetic modeling of Langmuir probe characteristics measured in the vicinity of a conducting sphere, in a well controlled laboratory plasma. In the experiment, the interaction of a drifting argon plasma with a conducting spherical sphere is studied using two cylindrical Langmuir probes located upstream and downstream of the sphere. Plasma parameters upstream of the sphere are determined by fitting an experimentally measured characteristic with the one obtained from simulations. Using the same upstream plasma parameters as input in simulations, the characteristic computed in the wake of the sphere is compared with the measured one. In addition to validating our simulation model for this type of experiment, the comparison serves to illustrate the importance of effects often neglected in the interpretation of Langmuir probe measurements, such as plasma with gradients and Earth magnetic field.