Fusion Science and Technology / Volume 45 / Number 4 / June 2004 / Pages 521-528
Technical Paper / dx.doi.org/10.13182/FST04-A527
A 1.5-dimensional 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 the JT-60SC large superconducting tokamak. A steady-state operation scenario with HHy2 = 1.4 and N = 3.7 has been obtained at Ip = 1.5 MA, Bt = 2 T, and q95 = 5, where noninductive 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 ~75% of the plasma current, and the current hole region is enlarged up to ~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 present transport simulation shows that heating equipment designed for JT-60SC is capable of forming and sustaining the current hole only by using off-axis beam-driven currents and bootstrap currents. The stability analysis shows that the beta limit with the conducting wall can be ~N = 4.5, which is substantially above the no-wall ideal magnetohydrodynamic limit.