A floating potential method for measuring ion density

Abstract

A simple method for analyzing cylindrical Langmuir probe curves in a cold-ion plasma is described which yields the ion density in weakly collisional plasmas for which purely collisionless theories give erroneous results. The method is based on an extrapolation to the floating potential of the saturation ion current raised to the 4/3 power. This procedure is not supported by theory but apparently works because effects neglected in the theory tend to cancel.