Characterization of an argon-hydrogen microwave discharge used as an atomic hydrogen source. Effect of hydrogen dilution on the atomic hydrogen production |
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Authors: | L Thomas J L Jauberteau I Jauberteau J Aubreton A Catherinot |
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Institution: | (1) URA 320 CNRS, UER des Sciences, 123 av A. Thomas, 87060 Limoges, France |
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Abstract: | This work is devoted to the study of an argon-hydrogen microwave plasma used as an atomic hydrogen source. Our attention has
focused on the effect of the hydrogen dilution in argon on atomic hydrogen production. Diagnostics are performed either in
the discharge or in the post-discharge using emission spectroscopy (actinometry) and mass spectrometry. The agreement between
actinometry and mass spectrometry diagnostics proves that actinometry on the Ha(656.3 nm) and Hβ(486.1 nm) hydrogen Balmer
lines can be used to measure the relative atomic hydrogen density within the microwave discharge. Results show that the atomic
hydrogen density is maximum for a gas mixture corresponding to the partial pressure ratioP
H
2/P
Ar range between 1.5 and 2. The variation of atomic hydrogen density can be explained by a change of the dominant reactive mechanisms.
At a low hydrogen partial pressure the dominant processes are the charge transfers with recombinations between Ar+ and H2 which lead to ArH+ and H
2
+
ion formation. Both ions are dissociated in dissociative electron attachment processes. At a low argon partial pressure the
electron temperature and the electron density decrease with increasing partial pressure ratio. The dominant mechanisms become
direct reactions between charged particles (e, H+, H
2
+
, and H
3
+
) or excited species H(n=2) with H2 producing H atoms. |
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Keywords: | Atomic hydrogen source microwave plasma optical spectroscopy mass spectrometry |
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