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Steady-State Operation Scenarios with a Central Current Hole for JT-60SC

Hiroshi Tamai, Shinichi Ishida, Gen-Ichi Kurita, Hiroshi Shirai, Katsuhiko Tsuchiya, Shinji Sakurai, Makoto Matsukawa, Akira Sakasai

Fusion Science and Technology / Volume 45 / Number 4 / June 2004 / Pages 521-528

Technical Paper /

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.

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