Investigation of electron cyclotron wave absorption and current drive in CFETR hybrid scenario plasmas

The investigation of electron cyclotron (EC) wave absorption and current drive has been performed for the China Fusion Engineering Test Reactor (CFETR) hybrid scenarios using the TORAY code. To achieve the physics goal of the EC system in CFETR, a total of four wave frequency values and nine locations of launching antennas have been considered, and the injection poloidal and toroidal angles have been scanned systematically. The electron cyclotron current drive (ECCD) efficiency of the 170 GHz EC system is quite low due to the wave-particle interactions being located at the low-field side. To optimize the ECCD efficiency, the wave frequency is increased up to 221-250 GHz, which leads to the power being deposited at the high-field side. The off-axis ECCD efficiency can be significantly enhanced by launching EC waves from the top window and injecting them towards the high-field side. The optimized ECCD efficiency at rho = 0.32 and at rho = 0.4 is 2.9 and 2.2 times that of 170 GHz, respectively.