Real-Time Control of Neoclassical Tearing Mode in Time-Dependent Simulations on KSTAR

Full text: Neoclassical tearing mode (NTM), a type of resistive instability, is one of major concerns in present and future tokamaks aiming at achieving plasmas with high fusion performance. Based on theoretical analyses, the time evolution of NTM can be interpreted and predicted by the modified Rutherford equation (MRE). The method using localised current drive to replace the missing bootstrap current with electron cyclotron current drive (ECCD) is expected to be one of the most promising ways for active stabilisation of the NTMs due to its narrow deposition width and equipment of the real-time steerable mirror. However, it is difficult to align ECCD to NTM accurately because of modification of the ECCD deposition and the island location in time according to evolution of the plasma transport and equilibrium. In this work, real-time feedback control of NTM is simulated using a transport code, ASTRA, coupled with the MRE at KSTAR. The plasma equilibrium, transport and island evolution is calculated self-consistently. Based on the results, performance of the NTM control is expected to be highly improved by optimising alignment between the island and the ECCD in both time and space. This will strongly contribute to ITER as well as forthcoming KSTAR experiments. (author)