Estimation of Operational Stability for the KSTAR TF Magnet

During the operation of the Korea Superconducting Tokamak Advanced Research (KSTAR), there exist various disturbances that cause the conductors to become unstable. The KSTAR Toroidal Magnet (TF) system was designed to secure the sufficient stability against them. The stability analysis showed that the energy margin of the TF Cable-In-Conduit (CIC) conductor was sufficiently high so that the expected disturbances could not cause the conductor to quench. During the 2nd KSTAR campaign in 2009, the cryogenic stability of the TF magnet system was analysed by energizing it up to 36 kA that is a bit higher than the designed current of 35.2 kA. The temperature increase measured at helium outlets was less than 0.1 K, which was well consistent with the analysis. Even in the reference plasma scenario, it was expected from the analysis that there still exists the sufficient temperature margin more than 4 K. The quench analysis was carried out to validate the design of the present TF CIC conductor from the magnet protection's point of view. In this paper, the cryogenic stability of the TF magnet system was estimated and the quench detection parameters were derived for protecting possible damages from quenches.