Pressure Drop of CICC From Manufacturing Stage to Plasma Operation in KSTAR Superconducting Magnet System

The Korea Superconducting Tokamak Advanced Research (KSTAR) is a superconducting tokamak that consists of cable-in-conduit conductors (CICCs) and has been successfully operated since 2008. KSTAR toroidal field (TF) and poloidal field (PF) coils are cooled by forced-flow supercritical helium of about 4.5 K. The complicated behaviors of the supercritical helium affect the plasma operation and the efficiency of the helium refrigerator system by means of, for instance, pressure drop. The annual measurements of pressure drop of PF coils are carried out including the manufacturing stage at room temperature to check the inside status of the cable-in-conduit conductor. The mass flow distribution of TF coils has also been checked since the individual coil stage. During current charging of the TF coil, we confirmed the change of pressure drop, and the friction factor of PF coils are compared to the ITER case. In this paper, the latest hydraulic behaviors based on pressure drop of the KSTAR superconducting magnet are presented.