AbstractWe have calculated time-dependent ion abundances including the C(III) metastable state 2s2p3P (time-dependent metastable model) in order to explain the discrepancies between measurements and simulations for the visible line intensities of C(III) from JT-60U. It is found that the metastable state is produced efficiently by inner-subshell ionization and remains for a long time comparable with the ground state. Consequently the line intensities of the singlet state decrease whereas those of the triplet states increase compared with the results given by a quasi-steady-state model.