Test function for the determination of plasma parameters by electric probes

A "test function" sensitive to the electron distribution function is used t o determine the plasma parameters by Langmuir probes. It was successfully a pplied to determine the parameters of the hot-electron group in a multipola r, magnetically confined Ar plasma, even when the ratio of bulk to hot-elec tron densities is greater than 50. The method can also be used to measure t he positive-ion density from a probe potential slightly below the plasma po tential, and to estimate the electron and negative-ion density and temperat ure in an Ar/SF6 plasma. A characteristic plasma potential is also introduc ed and is correlated with the plasma parameters. (C) 1999 American Institut e of Physics. [S0034-6748(99)01301-5].