Planar probes in diffusive plasmas

Summary form only given, as follows. The planar Langmuir probes and Mach probes (a/l<<1), where a is the probe radius and l is the ion neutral-collision length, were used to investigate an unmagnetized argon plasma in the presence of non-uniform drifting plasmas in density gradients. Mach probe data were compared with double-sided Langmuir probe data. The calculated plasma potentials from the Langmuir probe are found to be approximately equal to the average of the plasma potentials calculated from the data on each side of the Mach probe. A new method is presented to determine the ion drift velocity using the electron saturation currents. This method also allows the ion temperature to be estimated at low plasma densities. It is shown that a single sided planar probe gives information about the plasma located almost an ion neutral collision length away from the probe and should not be used in a non-uniform drifting plasma.