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Volume 93, Issue 7, 01 April 2003
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
93(2003); http://dx.doi.org/10.1063/1.1554754View Description Hide Description
The specific features of the probe characteristics in flowing-afterglow plasmas are studied experimentally and in theory. As it was found at a probe potential equal to the plasma one, an electron concentration in a probe vicinity (and a probe current) is decreased due to a predominant outflow of the electrons into an electrical circuit of the probe from the probe vicinity. The expression allowing one to reconstruct the undisturbed-by-probe electron concentration from only experimental data is derived. The reconstructed values of the electron concentration enable one to find from the experiments the semiempiric expressions allowing to describe quantitatively the behavior of the probe characteristics at the electron-attracting as well as at the ion-attracting potential, respectively. The expressions found (both for electron-attracting and ion-attracting potential) include the “separating length,” which merely is the Langmuir length with a factor equal to the square root of the electron mass over the ion mass ratio for two-component plasma. The intermediate part of the probe characteristics is discovered for probes operating with afterglow plasmas. This intermediate part is described in terms of the experimental parameter having a dimension of the length (presumably electron-orbital length). The value of the parameter does not depend on plasma parameters to within the ranges of plasma parameter variations for experimentally investigated plasmas as it was found. The experiments were performed with two cylindrical probes of 10 and 25 μm diam and lengths in the experimentally investigated ranges of the afterglow plasma parameters: and of He gas pressure (corresponding to electron mean-free path) with (or without) Ar addition.