A generator based on the condensation of superheated steam in a small Laval nozzle containing an axial corona electrode is described. Experiments with superheated water vapor at various nozzle flows are presented to show the relationship between the total rate of formation of charged aerosols (expressed as ejection current) and stagnation conditions of the vapor supply, electrode geometry of the nozzle. The characteristics of this type of generator and its optimum operating condition have been investigated.