Steady-state operation scenarios with a central current hole for JT-60SC

Tamai, Hiroshi ; Ishida, Shinichi; Kurita, Genichi; Shirai, Hiroshi; Tsuchiya, Katsuhiko; Sakurai, Shinji; Matsukawa, Makoto; Sakasai, Akira

The 1.5D time-dependent transport analysis has been carried out to investigate steady state operation scenarios with a central current hole by off-axis current drive schemes consistent with a high bootstrap current fraction for a large superconducting tokamak JT-60SC. A steady state operation scenario with HH=1.4 and =3.7 has been obtained at I=1.5 MA, B=2 T and q=5 where non-inductive currents are developed during the discharge to form a current hole with beam driven currents by tangential off-axis beams in combination with bootstrap currents by additional on-axis perpendicular beams. The bootstrap fraction increases up to nearly 75% of the plasma current and the current hole region is enlarged up to about 30% of the minor radius at 35 s from the discharge initiation. The current hole is confirmed to be sustained afterward for a long duration of 60 s. The stability analysis shows that the beta limit with the conducting wall can be about =4.5, which is substantially above the no wall ideal MHD limit.