Operating temperature margin and heat load in PF superconducting coils of KSTAR

The code SAITOKPF has been developed for the design and analysis of the poloidal field (PF) coil system of KSTAR (Korean Superconducting Tokamak Advanced Research) device. The plasma operation is studied by consideration of flux conservation. An equivalent circuit model is used to simulate the magnetic coupling among the plasma current, superconducting coils, the tokamak supporting structure and the cryostat. Due to the high changing rates in the operating currents of the PF coils, the magnetic coupling can generate high AC losses including the hysteresis loss, the eddy current loss, and the coupling loss. The helium is forced-flowed through the cable in conduit conductor (CICC) to remove the losses and to keep the temperature rise in the superconducting cable lower than its current sharing temperature. The thermal coupling between pancakes, layers, and cooling channels in PF coils is simulated by a quasithree-dimensional thermo-hydraulic model. In this paper, the physical model, the numerical method and the structure of the simulation code are introduced. A nominal operating scenario of the KSTAR device is used to simulate these phenomena.