Floating Multiple Probe Systems for Plasma Measurements

A new analysis of the current voltage characteristic of a floating double probe system is given, showing that the electron temperature must be estimated from measurements at the point of inflection of the characteristic if positive ion movement contributes to the probe circuit current. Temperature measurements will still be in error if the rates of variation of positive ion current to the two probes are not closely similar as the potential difference between them is varied. An alternative experimental technique is described which will yield correct temperature estimates in such circumstances, and is simpler and less perturbing to the plasma than the floating triple probe method.