title: Diagnostics of the electronegative plasma sheath at low pressures using microparticles.
abstract: Levitated particles are a new powerful diagnostic of the midplasma sheath region. They can reveal features undetectable either to plasma or to surface measurements. The equilibrium position of microparticles suspended in an oxygen plasma sheath, together with a model of the levitation force and Langmuir probe measurements, gives evidence of secondary electropositive plasmas in the already established plasma sheath, in the range of parameters where the modified Bohm criterion breaks down into multiple solutions.
authors.affiliation: Centre for Interdisciplinary Plasma Science, Max-Planck Institut für Extraterrestrische Physik, D-85740 Garching, Germany.
authors.forename: B M
authors.initials: BM
authors.lastname: Annaratone
authors.forename: T
authors.initials: T
authors.lastname: Antonova
authors.forename: H M
authors.initials: HM
authors.lastname: Thomas
authors.forename: G E
authors.initials: GE
authors.lastname: Morfill