Measurements of characteristic transients of planar electrostatic probes in cold plasmas

This article describes how to extract accurate information about a plasma f rom a capacitively coupled planar probe that is biased using pulsed radio-f requency excitation. The conditions necessary to observe correct saturation of the probe current are investigated, particularly the use of correct geo metry and biasing for the guard ring. With these precautions the probe is a n effective diagnostic for electron tail temperature at energies beyond tho se probed by conventional cylindrical probes. The dynamic response of the p robe is investigated using conventional sweep voltages and shows the onset of displacement current and inertial effects associated with ions and elect rons. In addition the effect of insulating films on the probe surface is ex amined, showing how the probe continues to operate even when it is coated. Characteristic changes caused by the presence of an insulating film give in formation about its electrical properties and its thickness. (C) 2000 Ameri can Institute of Physics. [S0034-6748(00)01707-X].