Electron cyclotron current drive under neutral beam injection on HL-2M

Abstract

Based on OMFIT framework and HL-2M parameters, this paper comprehensively considers the changes in plasma density, temperature, and other transport quantities caused by the interaction of neutral beam injection (NBI) and electron cyclotron wave (ECW) with plasma. The changes in the Shafranov shift of the plasma magnetic surface center are also evaluated. Theoretically, the influence of NBI on the deposition location and current drive efficiency of the ECW is studied. According to the findings, NBI affected the position location and efficiency of the electron cyclotron current drive (ECCD) deposited on both high field side (HFS) and low field side (LFS). NBI can relocate the ECW power deposition location to the core and increase the current drive efficiency when the ECW power is deposited on the LFS. When the NBI power increases to 7 MW, the ECCD deposition location can shift to the core by roughly 0.15 normalized small radii, and the current drive efficiency can be improved by 1.3 times. Moreover, as NBI power increases, the radial region where the dimensionless current drive efficiency equals to zero gets closer to the plasma edge. When ECW power is deposited on the HFS paraxial, increasing NBI power causes the ECW deposition location to move toward the plasma edge, thus lowering current drive efficiency. This trend is caused by an increase in NBI power, which can increase the Shafranov shift of the plasma center, increase the electron density, and change the electron temperature. These studies hold great significance for achieving more effective current drive and controlling the plasma current profile and neoclassical tearing mode instability.