Spectroscopic determination of the singly ionized helium density in low electron temperature plasmas mixed with helium in a linear divertor plasma simulator
- Center for Energy Research, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0417 (United States)
The spectroscopic method is developed to obtain the He{sup +} ion density n{sub He+} in low electron temperature, T{sub e}=5-20 eV, plasmas mixed with He. Plasmas were produced in the PISCES-B linear divertor plasma simulator [R. P. Doerner et al., Phys. Scr. T111, 75 (2004)] where the electron densities are n{sub e}=(1-15)x10{sup 18} m{sup -3} and the ionization degree is {approx}1-10%. In the method, the He I line intensity I{sub HeI} at {lambda}=447.1 nm is used, instead of the He II line intensity in the conventional method. The radial confinement time of He{sup +} ions is requisite, and is measured to be at a level of the Bohm confinement time. The He{sup +} ion concentration, n{sub He+}/n{sub e}, is found to be proportional to I{sub HeI}, and to weakly depend on n{sub e} and T{sub e}. Because of the higher ionization energy of He than other species (D{sub 2}, Ne, and Ar), the measured n{sub He+}/n{sub e} becomes systematically lower than the He gas pressure fraction, and agrees with data from an omegatron mass spectrometer. The omegatron measurement and estimates of the He{sup +} ion loss rates indicate that the influences of vibrationally excited deuterium molecules on the particle balance of He{sup +} ions are small at T{sub e}{>=}10 eV.
- OSTI ID:
- 21062057
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 10 Vol. 14; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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