Spatial variation of D-alpha line spectral profile and emission process inthe divertor region of JT-60U

Spatial variation of the D-alpha line spectral profiles emitted from the di vertor region has been measured with a high-resolution visible-light spectr ometer. The observed D-alpha line spectral profiles are compared with the c alculation of a neutral particle transport code. Good agreement is obtained under the attached-plasma conditions. The components of the observed spect ral profiles are identified at each measured position. The dissociative exc itation (direct production of D* (n = 3) by the dissociation of D-2 and D-2 (+)) is important near the divertor target. At positions away from the dive rtor target, the emission due to the electron collisional excitation of the dissociated atoms contributes significantly to both the D-alpha line inten sity and its spectral profile. The contribution of atoms produced by charge exchange and particle reflection are also important in the upstream of the divertor plasma. These fractions increase with the increase in the electro n density, broadening the D-alpha line spectral profile. The D-alpha line s pectral profiles are measured under several plasma conditions. The D-alpha line spectral profile near the target becomes broader during the ELMy phase . Under the detached-plasma condition, the D-alpha line spectral profile is symmetric to the line centre and is narrow, dominated by the low-temperatu re components. A similar feature is observed at the MARFE region.