Hydrogen emissions from peripheral plasmas in local island divertor and helical divertor configurations

Superdense core plasmas with a highly peaked electron density profile have been obtained in reduced recycling discharges in the Large Helical Device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)]. The polarization separation spectroscopy technique has been applied to characterize Hα emissions in the peripheral region of superdense core plasmas. Fitting positions of the high intensity Hα line are located just outside of the last closed flux surface in the local island divertor configuration. In the helical divertor configuration, high intensity emissions are observed around the inner and outer X points and along the divertor legs. In both configurations the hydrogen atoms have an inward velocity along the lines of sight.