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

The spectral lines of C 2 + and C 3 + 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 C 3 + (ionization of C 2 + and recombination of C 4 + ) and the loss flux of C 3 + (ionization and recombination of C 3 + ). It has been found that C 3 + is produced by the volume recombination of C 4 + and the ionization of C 2 + comparably. In contrast, the volume recombination of C 3 + is not detected, and the ionization flux of C 3 + is less than 1% of the C 3 + generation flux. Thus, the C 3 + generation flux is higher by two orders of magnitude than the loss flux. This result suggests that another loss mechanism of C 3 + such as transport loss from the X-point is significant.