Omegatron mass spectrometer for analysis of ion concentrations in hydrogenic plasmas

We describe an omegatron-type mass spectrometer used for measurement of the molecular and atomic ion concentrations as well as the ion species temperatures in hydrogenic plasmas. The experiments were performed in the PISCES-A linear plasma experiment with electron densities n≈10 11 –10 12   cm −3 ,...

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Bibliographic Details
Published in:Review of Scientific Instruments 2001-01, Vol.72 (1), p.623-626
Main Authors: Hollmann, E. M., Antar, G., Doerner, R. P., Luckhardt, S. C.
Format: Article
Language:English
Subjects:
08 HYDROGEN
ATOMIC IONS
ELECTRON TEMPERATURE
ELECTRONS
HYDROGEN
ION TEMPERATURE
MAGNETIC FIELDS
MASS SPECTRA
MASS SPECTROMETERS
MOLECULAR IONS
PHYSICS
PLASMA
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Summary:We describe an omegatron-type mass spectrometer used for measurement of the molecular and atomic ion concentrations as well as the ion species temperatures in hydrogenic plasmas. The experiments were performed in the PISCES-A linear plasma experiment with electron densities n≈10 11 –10 12   cm −3 , ion temperatures T i ≈2–8  eV , electron temperatures T e ≈3–30  eV , and magnetic fields B=0.8–1.9  kG . The resulting mass spectra show clear evidence of atomic hydrogen H + , as well as of the molecular ions H 2 + and H 3 + , with H + and H 3 + usually being dominant. It is found that large electron repeller voltages (≈−200 V) are important for preventing electrons from entering the diagnostic region and ionizing the residual gas. The relative peak heights for the different ions are found to vary as a function of ion repeller voltage, probably due to differences in ion temperature.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.1310594