Effect of plasma resistance on electron temperature measurement by means of an electrostatic probe

The effect of the equivalent plasma resistance between the probe and the reference electrode on the gradient of the semilog plot of the electron-current curve vs voltage of a probe has been studied theoretically for the probes of plane, cylindrical, and spherical types. The probe current-voltage characteristic actually measured deviates from its regular curve because of drawing current through the bulk plasma not having an infinite conductivity. The electron temperature Te determined from the measured electron-current curve by using the usual graphical method will be higher than its true value. The theoretical maximum errors in Te determination for the three kinds of probe studied are all within a factor of 2. Some experiments are also presented and discussed.