Impurity emission characteristics of long pulse discharges in Large Helical Device

Line spectra from intrinsic impurity ions have been monitored during the three kinds of long-pulse discharges (ICH, ECH, NBI). Constant emission from the iron impurity shows no preferential accumulation of iron ion during the long-pulse operations. Stable Doppler ion temperature has been also measured from Fe XX, C V and C III spectra

Magnetic Axial Dependency of Hα Emission Location in Peripheral Plasmas of Large Helical Device as Determined by Plasma Polarization Spectroscopy

The behavior of hydrogen neutral particles in and around the ergodic layer of Large Helical Device plasmas has been investigated through Hα emission spectral line profiles using plasma polarization spectroscopy (PPS). The PPS technique enables us to quantitatively evaluate emission locations, atomic temperatures and velocity components along the line-of-sight (LOS) for both inner and outer peripheral regions. The emission locations and the LOS components of atomic velocities are determined by varying the magnetic field axis Rax from 3.60m to 4.00 m, shot by shot. The high intensity region of Hα emissions is localized in the inner ergodic layer for the inward configuration. With an increase in Rax, the high intensity region of Hα emission moves outward