Impurity accumulation in the main plasma and radiation processes in the divetor plasma of JT-60U

Two studies are included: tungsten accumulation in the main plasma and radiation processes of carbon ions in the detached plasma of JT-60U. [Tungsten] It has been found that tungsten accumulation becomes more significant with increasing plasma rotation velocity against the plasma current direction, where negative radial electric field is formed. The accumulation level does not depend on the tungsten generation flux, suggesting the transport plays a dominant role to determine the accumulation level. In a high density plasma at 62% of the Greenwald density, the tungsten accumulation levels decreased significantly, suggesting a shielding effect of the peripheral plasma. [Carbon] The spectral lines of C and C emitted around the X-point in the detached plasma with MARFE are measured with a VUV spectrometer and a 2-dimensional visible spectrometer in order to compare the generation flux of C ( ionization of C and recombination of C ) and the loss flux of C ( ionization and recombination of C). It has been found that C is produced by the volume recombination of C and the ionization of C comparably. In contrast, the volume recombination of C is not detected, and the ionization flux of C is less than 1% of the C generation flux. Thus, the C generation flux is higher by two orders of magnitude than the loss flux. This result suggests that another loss mechanism of C such as transport loss from the X-point is significant. 1 Impurity accumulation in the main plasma of JT-60U 1.