Experimental study of the influence of surface-potential variations on the measurement of the electron temperature of a plasma by an electrostatic probe

The quantitative influence of controlled spatial variations of the surface potential of an electrostatic probe on the measurement of the electron temperature has been studied experimentally using an electrostatic probe with an interdigital structure. By statistical treatment of a large number of measurements in an on-line computer, it was possible to detect changes in the apparent electron temperature of as little as 2%. Such changes occurred when potentials of the order of the electron thermal energy were applied to the surface of the probe on spatial scales of the order of the Debye length in the plasma. For larger potential variations, the influence on the apparent temperature was very important, regardless of the spatial scale.