Abstract
We observe the Balmer-α, -β, and -γ lines of hydrogen atoms and Q branches of the Fulcher-α band of hydrogen molecules simultaneously with their polarization resolved for large helical device. From the fit including the line splits and the polarization dependences by the Zeeman effect, the emission locations, intensities, and the temperatures of the atoms and molecules are determined. The emission locations of the hydrogen atoms are determined outside but close to the last closed flux surface (LCFS). The results are consistent with a previous work (Phys. Plasmas 12, 042501 (2005)). On the other hand, the emission locations of the molecules are determined to be in the divertor legs, which is farer from those of the atoms. The kinetic energy of the atoms is 1 ∼ 20 eV, while the rotational temperature of molecules is ∼0.04 eV. Additionally, substantial wings, which originate from high velocity atoms and are not reproduced by the conventional spectral analysis, are observed in the Balmer line profiles. We develop a one-dimensional model to simulate the transport of the atoms and molecules. The model reproduces the differences of the emission locations of the atoms and molecules when their initial temperatures are assumed to be 3 eV and 0.04 eV, respectively. From the model, the wings of the Balmer-α line is attributed to the high velocity atoms exist deep inside the LCFS, which are generated by the charge exchange collisions with hot protons there.
Original language | English |
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Article number | 012514 |
Journal | Physics of Plasmas |
Volume | 20 |
Issue number | 1 |
DOIs | |
State | Published - Jan 2013 |
Externally published | Yes |
Funding
The authors are grateful to the LHD experimental group for their support. This work was supported by the National Institute for Fusion Science (Grant Nos. NIFS08KOAP020 and NIFS10KLMP003).
Funders | Funder number |
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Japan Society for the Promotion of Science | 23340183 |
National Institute for Fusion Science |