B.J. Lee1, N. Pomphrey2, C.S. Chang3, S.Y. Cho1, S.C. Jardin2, G.S. Lee1, G.H.Neilson2, H. Park1, 2, W. Reierson2, and KSTAR team1, 2
1 Korea Basic Science Institute, 52 Yeoeun-Dong, Taejeon, 305-333, KOREA
2 Princeton Plasma Physics Laboratory, P.O.Box 451, Princeton, NJ 08543, USA
3 Korea Advanced Institute of Science and Technology, Taejeon, KOREA
The Korean Superconducting Tokamak Advanced Research (KSTAR) will have superconducting magnets for both the poloidal field (PF) coils, which are capable of full inductive operation for approximately a 20-s flattop, and the toroidal field (TF) coils. The physical arrangement of the PF set has 14 coils external to the TF coils. The central solenoid consists of four pairs of modules (PF1 - 4) to provide some shaping capability. In addition there is a pair of divertor coils (PF5) and two pairs of outboard ring coils (PF6-7). Seven and 11 independent power circuits are used for double null (DN) and single null (SN) configurations respectively.
The analysis of the equilibrium flexibility of the KSTAR PF system determines the coil currents required to maintain prescribed equilibrium configurations over the desired range of operational parameters, usually specified in terms of the plasma current Ip (q95), normalized toroidal beta bN, and normalized plasma internal inductance li(3). Four geometric constraints on the plasma separatrix and the flux linkage through the geometric center of the plasma are specified for the free boundary equilibrium calculations. Thus, there are five constraints among the seven independent coil groups. The remaining two degrees of freedom in case of DN plasma are eliminated by regularizing (smoothing) the coil current distribution by minimizing the quantity: summation from 1 to ncoil of (Ij/DAj)2 where DAj is the area of each PF coil.
The ripple magnitude due to the finite number of TF coils and the size of the port for the neutral beam injector determined the number, size, and shape of TF coils in KSTAR. Three ripple criteria for a shaped plasma are used for types of ripple transport such as the collisionless stochastic ripple loss, loss due to the ripple trapping, and collisional ripple loss mechanisms. The current design of the TF coil, 16 coils and D-shape, is big enough to satisfy various requirements on the ripple magnitude at the plasma and to provide an adequate access for tangential NB injection.
* Work supported by the Ministry of Science and Technology of the Republic of Korea