Hydrogen Atomic and Molecular Emission Locations and Intensities in the LHD Edge Plasma Determined from Simultaneously Observed Polarization Spectra

Abstract

We observed polarization-resolved emission spectra of the Balmer-α,-β, and-γ lines of hydrogen atoms and the Q branches of the Fulcher-α band of hydrogen molecules simultaneously with six lines of sight in a poloidal cross section of the Large Helical Device (LHD). From the fit of the spectra including the line splits and their polarization dependence due to the Zeeman effect, we determined the emission locations, intensities and temperatures of the atoms and molecules. The determined emission locations of the hydrogen atoms were just outside the last closed flux surface and the intensities showed small dependence on the location. The emission locations of the molecules were rather around the divertor legs and their emission intensities showed location dependences. The determined atomic temperature was about 1 eV and the molecular rotational temperature was 0.04∼0.07 eV, both of which showed no systematic dependence on the location within the experimental accuracy.

Ro-vibrational population distribution in the ground state of hydrogen isotopologues in LHD peripheral plasmas deduced from emission spectroscopy

“…The results are shown in Tables 4 and 5 for H2 and D2, respectively, and thus estimated ro-vibrational population distributions in the ground state are shown in Figs. 9 To confirm the validity of the analysis procedure, the experimental 𝑛𝑛 𝑑𝑑𝑣𝑣 ′ 𝑁𝑁 ′ obtained from Eq. 1 and the reconstructed 𝑛𝑛 𝑑𝑑𝑣𝑣 ′ 𝑁𝑁 ′ from 𝑛𝑛 𝑋𝑋𝑣𝑣𝑁𝑁 in Figs.…”

“…As in [21], the H2 emission of Q1, 2 lines is peaked in the center of a plasma beam. From [8,9] it is clear that the H2 emission regions are located where ne ~ 10 18 /m 3 and Te ~ 10 eV and that the position dependence of Trot estimated from Q1, 2, 3 lines is very small. The actual origin of the observed bi-Boltzmann distribution is not clear.…”

“…In these works, several repeated shots at a similar discharge parameter were measured because the spectral window per shot was not enough to measure whole Fulcher-α band emission. In the large helical device (LHD) the ro-vibrational population is measured only up to v = 2 and N = 3 for H2 in the 3p 3 Πu state due to the small spectral window [8,9]. On the other hand, the ro-vibrational populations up to high N states in the ground state of H2 and D2 molecule were recently evaluated by Fulcher-α band spectroscopy for inductively coupled radio-frequency discharge [10].…”