DC PROBE DETECTION OF PHASED EEDFS IN RF DISCHARGES

Detection of non-Maxwellian electron energy distribution functions (EE DFs) by Langmuir probes in the presence of radiofrequency (RF) fluctua tions in the plasma potential is possible if the probe is properly RF compensated. If the non thermal electrons are created by wave accelera tion, however, they usually are bunched at one phase of the RF. In thi s case, the usual method of forcing the probe to follow fluctuations i n the Boating potential (V-f) will be inappropriate, since V-f itself will be rime-dependent in such a way as to ensure that the fast electr on tail is nor detected. The probe must be made to follow fluctuations in the space potential. Computations are given to show the effect of a RF on distributions with high-energy tails with and without the prop er compensation. Singular EEDFs arising in the case of constant energy gain are also treated for the first time.