Design, R&D and assessment of performance of the JT-60SA upper divertor

Sakurai, Shinji; Kawashima, Hisato; Higashijima, Satoru; Shimizu, Katsuhiro; Masaki, Kei; Asakura, Nobuyuki; Shibama, Yusuke; Sakasai, Akira

The entire plasma facing components should be water-cooled in JT-60SA. A cassette module of divertor is introduced for remote maintenance. The divertor targets are mounted on the cassette. A brazed carbon fiber composite target is promising candidate for the divertor target. The latest results of mock-ups test clarified that thermal fatigue life cycles are more than 1000 cycles of 15 MW/m10 sec. The divertor is designed to control divertor detachment for heat load reduction. The vertical targets and a "V-shaped corner" like as that in ITER are adopted to enhance detachment. Divertor heat load and pumping efficiency has been evaluated, using 2D plasma fluid (SOLDOR) and neutral Monte-Carlo (NEUT2D) code. The plasma detachment occurs near the outer-strike point within the "V-shaped corner", which results in low peak heat flux density 5.8 MW/m for the case with additional gas puff of 510/s compared to 11.4 MW/m for the case without "V-shaped corner".