Book/Report

FZJ-2018-03886

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Untersuchung der Eigenschaften einer Argon-Glimmentladung mit Titankathode mittels Langmuir-Sonde und laserinduzierter Fluoreszenz

Baggio Scheid, V. H. (Corresponding author)FZJ*

1992
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/19203

Report No.: Juel-2655

Abstract: In this work an abnormal Argon glow discharge with Titanium cathode has been investigated. The results presented are the measurements and calculations concerning the electron beam plasma in the negative glow. Two diagnostics have been employed to determine the plasma parameters. A Langmuir probe has been used in the negative glow to measure the spatial distributions of the electron density, temperature and the plasma potential. Two electron groups were found, slow electrons with a temperature of 0.3 eV and density of $\sim$ 10$^{11}$ cm$^{-3}$, and fast electrons with $\sim$ 3.0 eV and $\sim$ 10$^{7}$ cm$^{-3}$. Under all operational conditions the plasma potential was almost constant within the negative glow and about 1.5 V positive with respect to the anode voltage. The electric field has been calculated from the potential profile. It is shown that, within the error of measurement, this electric field is equal to the ambipolar electric field, which has been calculated from the electron density and temperature p rofiles. The density distribution of titanium atoms, ions and $^{3}$P$_{2}$ metastable argon atoms has been measured by means of the laser induced fluorescence. The densities were absolutly calibrated using a carbon arc as a radiation standard. The spatial resolution was 1.5 mm in the axial direction and 3 mm in the radial direction. In the range of operation a titanium density (Ti I) of about 3.0 x 10$^{10}$ cm$^{-3}$ has been found. From the population distribution of the titanium atoms in the ground state levels the temperature profile in the discharge axis has been determined. In the negative glow a nearly constant temperature of about 350 K has been found. Towards the cathode a temperature rise up to 410 K at 0.5 kV (0.2 mb) and up to 540 K at 2.1 kV (0.1 mb) has been observed. A numerical calculation of the electron density distribution has been carried out. By solving the diffusion equation a lot of information concerning the beam electrons has been obtained. The position of the density maxima has been seen to depend on the amount of the low energy beamelectrons. From the shape of the radial density profiles it turned out that the divergency of the beam electrons increased with the length of the cathode fall. With the experimental density profiles several collisional rates have been evaluated and used in a numerical calculation of the axial profiles of the titanium atoms and $^{3}$P$_{2}$ metastable argon atoms. A good agreement with the experimental profiles has been achieved in both cases.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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