Influence of supersonic ions and nonlocal electron kinetics on the sheath voltage in an expanding plasma

Benjamin Schröder, Ralf Peter Brinkmann, Jens Harhausen, Ruediger Foest, Andreas Ohl

2015 Plasma Sources Sci. Technol. 24 025011


We present the investigation of the sheath potential in an expanding plasma. The properties of the expanding plasma are measured by means of a Langmuir probe. The obtained data is used to calculate the sheath potential and the electron distribution function. We show that the sheath voltage is typically about 40% lower than in a case that neglects supersonic ions and assumes a Maxwellian electron distribution. We explain the magnitude of the measured sheath potential by balancing the ion flux density calculated with an analytical model for the expanding plasma and the electron flux density calculated with the electron distribution function.