Residual gas entering high density hydrogen plasma: rarefaction due to rapid heating

TitleResidual gas entering high density hydrogen plasma: rarefaction due to rapid heating
Publication TypeJournal Article
Year of Publication2015
AuthorsN. den Harder, D.C. Schram, W.J Goedheer, H.J de Blank, M.CM van de Sanden, G.J van Rooij
JournalPlasma Sources Science and Technology
Volume24
Issue2
Number2
Pagination025020
Abstract

The interaction of background molecular hydrogen with magnetized (0.4 T) high density (1–5 × 10 20  m −3 ) low temperature (∼3 eV) hydrogen plasma was inferred from the Fulcher band emission in the linear plasma generator Pilot-PSI. In the plasma center, vibrational temperatures reached 1 eV. Rotational temperatures obtained from the Q( v = 1) branch were systematically ∼0.1 eV lower than the Q( v = 0) branch temperatures, which were in the range of 0.4–0.8 eV, typically 60% of the translational temperature (determined from the width of the same spectral lines). The latter is attributed to preferential excitation of translational degrees of freedom in collisions with ions on the timescale of their in-plasma residence time. Doppler shifts revealed co-rotation of the molecules with the plasma at an angular velocity an order of magnitude lower, confirming that the Fulcher emission connects to background molecules. A simple model estimated a factor of 90 rarefaction of the molecular density at the center of the plasma column compared to the residual gas density. Temperature and density information was combined to conclude that ion-conversion molecular assisted recombination dominates plasma recombination at a rate of 1 × 10 −15 m 3 s −1 . The observations illustrate the general significance of rapid molecule heating in high density hydrogen plasma for estimating molecular processes and how this affects Fulcher spectroscopy.

DOI10.1088/0963-0252/24/2/025020
Division

MaSF

Department

MaSF-E

PID

4658451c610d4c6feeb22aabc1bf28eb

Alternate TitlePlasma Sources Sci. Technol.
LabelOA
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