Accuracy Enhancement In Probe Registration Of Anisotropic Charged Particles Distribution Functions In Plasma: Analysis Of Systematic Errors

A well-known technique for measuring anisotropic distribution functions of electrons and ions in plasma, by means of a flat single-sided probe, based on the representation of the distribution function as series expansion in Legendre polynomials, was tested for accuracy and systematic errors
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. Analytical relations between plasma parameters and the necessary quantity of series terms were attained for the ion distribution function when anisotropy was produced through the presence of an electric field in plasma. It was proven that ten terms of the series appear to be sufficient for its accurate description except for powerful fields. The technique of spline test data interpolation for strongly pronounced anisotropic distribution functions of charged particles is proposed. The technique passed an evaluation procedure; as a result, it was verified and confirmed that this method considerably reduced the systematic error at the given quantity of series terms. Experiments with frequently occurring real plasma objects with 'mirror symmetry' (in comparison with the most common cases of asymmetry) provide evidence that at a fixed quantity of Legendre's series terms for the distribution function, the number of the necessary probe positions decrease two-fold.