Experimental demonstration of advanced ISO-FLUX equilibrium control during the first JT-60SA operational phase under DEMO-relevant conditions

Abstract In the control of large superconducting tokamaks, particularly for devices like DEMO reactors, where no stabilizing plates or in-vessel coils can be mounted due to the existence of tritium breeding blankets, position, shape, and current of plasmas must be controlled solely with superconducting coils, for which we developed novel control schemes (Inoue et al 2021 Nucl. Fusion 61 096009); an adaptive voltage allocation (AVA) scheme automatically allocates power supply voltages for plasma current and position/shape control, and a last closed flux surface reconstruction scheme can robustly reconstruct the plasma shape in the presence of large eddy currents. This paper reports the first experimental demonstration of these schemes on JT-60SA, which is the world’s largest tokamak and has DEMO-relevant device conditions, such as no stabilization plates and in-vessel coils. During the first operational phase at JT-60SA, interference in control of shape, position, and current of plasmas was successfully resolved by the AVA scheme, achieving several milestones such as an elongation of 1.7 (with a vertical instability growth rate of around 90 s −1 ), and the world’s largest plasma current of 1.2 MA as a superconducting tokamak.