ABSTRAKT

The electron energy distribution function is generally measured in plasma environment by means of single electrostatic probes. The principle of the technique which uses the second derivative of a current-voltage characteristic is well known but difficulties occur for the mathematical treatment of the experimental data. The calculation of the second derivative may be significantly distorted when smoothing the noisy signal. One of the most important problems is the identification of such artefacts, and the lowering of their effects. In the present work, great care is devoted to this problem for avoiding such distorsion. Then, the local equilibrium or non-equilibrium character of the electron energy distribution function is studied inside a low pressure plasma arc jet. It is concluded that the distribution is more and more in equilibrium as the distance from the nozzle exit increases.