Admittance Probe Method of Measuring Time Resolved Plasma Electron Temperatures

It is shown that the plasma electron temperature in electron volts is given by the product of the ion saturation current and the probe-to-plasma resistance at the floating potential. An ac capacitance bridge circuit is described which will measure this resistance with a response time that approaches the ion transit time across the sheath. The method is demonstrated by a measurement of electron temperature in the Wisconsin toroidal octupole.