Impedance probe and DC probe studies on the plasma of a glow discharge

Abstract

A plane probe acting simultaneously as an RF impedance probe and a DC probe has been used for studying the collision-dominated plasma of a glow discharge. The conventional probe methods are suitably modified so as to take into account the effect of the presheath lying between the probe sheath and the undisturbed plasma.Measurements of the electron temperature and electron density have been carried out under different discharge conditions. It is found that the electron temperatures, as given by the RF and DC methods, are in excellent agreement, while the corresponding electron densities differ by a factor of 2-3. The thickness of the positive-ion sheath formed in front of the probe has been determined by the impedance method; the variation of the thickness with sheath voltage, discharge current or operating pressure is as expected.