(EX/P4-25) Impurity Accumulation in the Main Plasma and Radiation Processes in the Divetor Plasma of JT-60U

T. Nakano1), H. Kubo, N. Asakura, K. Shimizu, S. Higashijima
1) Japan Atomic Energy Institute, Naka, Japan

Abstract.  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 63% of the Greenwald density, the tungsten accumulation levels decreased siginificantly, suggesting a shielding effect of the peripheral plasma. [Carbbon] 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 2-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.

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