AC Loss Analysis on the KSTAR PF1L Coil Based on the Long-Term Commissioning Shot Data

The Korea Superconducting Tokamak Advanced Research (KSTAR) uses superconductors for all of its magnets. During plasma operation, various high AC losses, including hysteresis loss, coupling current loss, eddy current loss, and others, are generated in the Central Solenoid (CS) and Poloidal Field (PF) coils. Thus, it is important to analyze AC losses of a superconducting magnet for its reliable operation in two main perspectives: short term quench prevention and long term steady-operation. With 10 years of operation, KSTAR has provided many invaluable data in superconducting magnet operation regarding AC loss issues. This paper focuses on the AC loss of the KSATR CS coil based on the long-term operation data. The CS coil of the KSTAR consists of 4 sets of PF coils, PF1 to PF4. PF1 coil especially experiences the largest magnetic field and variations, and consequently the largest loss due to its central location in CS coil. The experimental results of the total loss measured for PF1 are introduced. Then, each AC loss is calculated numerically to relate to the total loss results. Finally, the results are interpreted qualitatively regarding the critical current density and effective coupling time constant to investigate the possible relation between the AC loss and the magnet's performance.