Radiation process of carbon ions in JT-60U detached divertor plasmas

The spectral lines of C2+ and C3+ emitted around the X-point in the detached plasma with MARFE are measured with a VUV spectrometer and a two-dimensional visible spectrometer in order to compare the generation flux of C3+ (ionization of C2+ and recombination of C4+) and the loss flux of C3+ (ionization and recombination of C3+). It has been found that C3+ is produced by the volume recombination of C4+ and the ionization of C2+ comparably. In contrast, the volume recombination of C3+ is not detected, and the ionization flux of C3+ is less than 1% of the C3+ generation flux. Thus, the C3+ generation flux is higher by two orders of magnitude than the loss flux. This result suggests that another loss mechanism of C3+ such as transport loss from the X-point is significant.