Balance of ionization and recombination of carbon ions in high density peripheral plasmas of the JT-60 U tokamak.

In high density and low temperature peripheral plasmas of JT-60 U, i.e. detached divertor plasmas, C III and C IV lines were observed by a visible and VUV spectrometers in order to investigate dominant radiators, radiation power and particle balance between the radiators. An emission peak was found between the inner strike and the X-point. With increasing electron density, the emission peak moved to the X-point with a constant electron temperature of ∼7 eV. In the case the emission peak was located on the X-point, the dominant radiators in the emission peak were C2+ and C3+, which contributed 30% and 60% to the total radiative power. It was found that C3+ was produced by the ionization of C2+ and the volume recombination of C4+ at a similar rates. However, the loss flux of C3+ was lower by two orders of magnitude than the C3+ production flux, indicating that another loss mechanism such as transport loss around the X-point was significant. [ABSTRACT FROM AUTHOR]