Plasma diagnostics from the dynamic current-voltage characteristic of an electric probe

A method for measuring the plasma electron density from the dynamic current-voltage probe characteristic is considered. For this purpose, an additional rectangular negative voltage pulse or a high-frequency sinusoidal voltage is applied to a negatively biased probe. Analytic expressions are derived for two cases: when the space charge sheath obeys the 3/2 law and when the voltage varies over a time shorter than the ion transit time through the sheath so that the sheath does not obey the 3/2 law. Dynamic and statistic probe methods for determining the electron density are compared experimentally