IMPROVED CIRCUIT FOR POTENTIAL FLUCTUATION COMPENSATION IN THE PLASMA DURING THE ELECTRON-ENERGY DISTRIBUTION FUNCTION MEASUREMENT BY A PROBE

An improved circuit consisting of a simple voltage follower for the measurement of electron energy distribution function in a plasma has been proposed. This circuit makes it possible to eliminate the fluctuation of plasma space potential, the deviation of dc probe voltage caused by the probe current drawing across the plasma resistance, and the attenuation of the second derivative signal during the measurement, simultaneously. Both the probe circuit considerations and the experimental results are presented.