Apparent wavelength shifts of H-like ions caused by the spectral fine structure observed in CHS plasmas

A new charge exchange spectroscopy (CXS) system viewing the plasma from the upside and the downside simultaneously was installed on the Compact Helical System (CHS) to detect the absolute value of Doppler shift due to poloidal rotation velocity (< 5 km/s). The apparent Doppler shift, not due to plasma rotation, in charge exchange excited spectral lines is observed in the plasma peripheral region (Ti ∼ 100 eV) and in the after-glow recombining phase (Ti ∼ 30 eV). The apparent Doppler shift is always red-shift regardless the direction of plasma rotation and is explained as the effect of the spectral fine structure of hydrogen-like ions. (author)