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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:23 |
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Conference: Bucharest University Faculty of Physics 2010 Meeting
Section: Optics, Spectroscopy, Plasma and Lasers
Title:
Numerical method for the determination of the plasma parameters from the experimental Electron Energy Distribution Function
Authors:
Catalin Negrea(1,2), Vladimir Manea(1), Vania Covlea(1), Alexandru Jipa(1)
Affiliation:
(1) Faculty of Physics, University of Bucharest, P.O. Box MG-11, 0771253 Bucharest–Magurele, Romania
(2) Institute of Space Science, P.O. Box MG-23, Magurele – Bucharest, Romania
E-mail
vanea.covlea@yahoo.com
Keywords:
Langmuir probe data, electron concentration, electron temperature, numerical derivative, nonlinear fitting
Abstract:
A numerical application for the processing of the Langmuir probe data is developed. Two important plasma parameters, the electron concentration and temperature, are determined by analyzing the experimental current-voltage characteristic for several data sets. The Electron Energy Distribution Function (EEDF) is numerically derived using the Druyvesteyn method. The method of obtaining the second derivative of the probe current is chosen in order to allow the smoothing of the processed data and also the propagation of the experimental errors. The EEDF is used to calculate the electron concentration and effective temperature, by fitting it with a presumed theoretical form, either a Maxwell or Druyvesteyn distribution. We use the Gauss-Newton nonlinear fitting algorithm, which provides a good fitting sensitivity with respect to the theoretical form of the EEDF, and allows a simple estimation of the errors with which the plasma parameters are determined. We present the algorithm for a plasma with a single electronic group and then apply it to the case of a plasma with two electronic groups. In the latter case, there is no other method of precisely determining the concentration and temperature of the two populations of electrons, which gives a special importance to the proper estimation of the experimental errors.
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