27D27P
平衡制御シミュレータの開発とJT-60SA運転シナリオの検討	 
Investigation of JT-60SA Operation Scenario throughDevelopment of Equilibrium Control Simulator
鈴木隆博、宮田良明、井手俊介、浦野創、藤田隆明
SUZUKI Takahiro, MIYATA Yoshiaki, IDE Shunsuke, URANO Hajime, FUJITA Takaaki
日本原子力研究開発機構
Japan Atomic Energy Agency (JAEA)
Stable and reliable control of plasma shape,
position and current are essential for not only themachine safety but also the efficient execution ofphysics study. That is, plasma operation scenariocontaining current ramp up/down as well as
formation of divertor configuration must be drawn
using the equilibrium controller within the limit ofmachine capabilities, e.g. poloidal field (PF) coilcurrents and voltages, avoiding the verticalinstability. In order to develop and design such
equilibrium controller, we are intensively
developing an equilibrium control simulator for theJT-60SA tokamak as well as ITER, DEMO andfuture reactor. In this study, current status andfuture plan of the equilibrium control simulator aredescribed and JT-60SA operation scenario isinvestigated using the simulator developed.
The equilibrium control simulator consists of(1) plasma simulator and (2) equilibrium controller.
(1) The plasma simulator gives free-boundary
Grad-Shafranov equilibrium solution coupled withclosely placed conducting wall under given PF coilcurrents and prescribed plasma parameters (poloidal
beta βp and internal inductance li). Poloidal
magnetic flux is consumed according to Ejima
scaling during current ramp and surface loop
voltage during current flattop. (2) The equilibrium
controller controls PF coil currents according to theisoflux scheme, where the poloidal flux at specified
multiple control points is adjusted to the poloidalflux at the plasma surface so that the plasma surface
approaches to the control points. A set of PF coilcurrents that individually adjust the poloidal flux ateach control point is identified in every control
cycles.
A JT-60SA operation scenario with plasma
current ramp-up and pressure increase is developed
using the equilibrium control simulator; see figure.
Waveforms of βp and li (Fig. b) are prescribedassuming auxiliary heating application. Plasma
current (Fig. a) is raised along the given waveformsof its reference value to 5.5MA through flux swing(Fig. c) by controlled change in center solenoidcurrents (CS2 in Fig. d). The equilibrium controller
also controls plasma configuration from limiter todivertor by increasing plasma elongation, according
to the given position change of the control points(up to 8). Distance between one of the control
points near outboard mid-plane and plasma surface
is shown in Fig. e. The distance approaches to zeroby the control of coil currents (mainly EF1 locatedoutboard side; the coil current shown in Fig. d) The
outboard plasma surface is Highly elongatedplasma (κ~1.8) is stably sustained without verticalinstability with help of passive conducting wall andactive control of PF coils including two in-vessel
coils. Equilibrium control capability against change
in plasma parameter (βp, li) or flux consumption is
also to be discussed in the presentation.

Figure: Waveforms of current ramp-up simulation(left). Poloidal cross-section of the JT-60SA device
modeled in the simulator with PF coils (CS1-4,EF1-6 and two in-vessel coils; green) (right).
Plasma surfaces at t=2.7s (limiter; blue) and 24.6s(divertor; red) are shown with control points(crosses).