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内容記述 |
Two types of poloidal magnetic field coils, superconducting poloidal field (SCPF) coils and in-vessel coils called fast plasma position control (FPPC) coils, will be installed in JT-60SA. We presented different roles in SCPF and FPPC coils. The SCPF coils control plasma position and shape (P/S) and plasma current (Ip), whereas the FPPC coils stabilize the perturbation of n = 0 mode of magnetohydrodynamic (MHD) instability, such as vertical instability. This study developed a controller that outputs a coil voltage command for the power supply connected to each coil based on an ISO-FLUX scheme by an equilibrium control simulation code, MHD equilibrium control simulator MECS. This controller stabilizes the horizontal and vertical plasma displacements using FPPC coils. The FPPC coils have the advantage of fast plasma position control due to a fast coil current response; however, the induced current is also driven in FPPC coils. Thus, we propose a control logic to mitigate the induced currents, particularly when the induced voltage is large. The difference in coil current response for SCPF and FPPC coils causes the coupling problem. Thus, the decoupling between the SCPF and FPPC coils was established by employing the derivative treatment on the ISO-FLUX scheme in the FPPC control. To investigate the effectiveness of the FPPC control, using MECS we evaluated the allowable Ip disruption intensity, which causes the plasma horizontal displacement, in the high elongation plasma, which relates to the plasma vertical displacement. The higher Ip disruption intensity and elongation were allowed by adding the FPPC control. We investigated the controllability in the plasma ramp-up and flat-top operations. The support of FPPC control for SCPF control expands the plasma operation region which contributes to achieve the planned plasma operation in JT-60SA. |
