Investigation of electron cyclotron current drive efficiency on the J-TEXT tokamak


 Electron cyclotron current drive (ECCD) has been extensively used to modify the current profile and stabilize the neoclassical tearing mode (NTM) instability by taking advantage of highly localized driven current. The efficiency of ECCD research is of great importance for the NTM stabilization, since improving the efficiency is beneficial for the reduction of ECCD power threshold. The first result of the ECCD efficiency was obtained by electron cyclotron wave (ECW) power scan on the J-TEXT tokamak. The fully non-inductive current drive efficiency is derived to be approximately η0 = 0.06-0.16×1019 Am-2W-1 on the J-TEXT tokamak. The effect of the residual toroidal electric field has been included in the determination of the current drive efficiency, which will enhance the ECCD efficiency. It can be estimated that the driven current is approximately 24 kA at 300 kW ECW power which can be used to modify the local plasma current density at magnetic island for the stabilization of tearing mode. The ratio of Spitzer conductivity between omhic (OH) and ECCD phases is considered and the experimental data have been corrected. The correction results show that the current drive efficiency η1 caused by the fast electron hot conductivity decreases by approximately 79%.