Simulation Of High Field Side Lower Hybrid Current Driving On EAST Tokamak

Density limit is an unavoidable problem in all lower hybrid current drive(LHCD)experiments.How to improve the current drive efficiency under high-density conditions is the focus of LHCD research.Compared with the low field side(LFS),the high field side(HFS)in a tokamak has higher magnetic field and quiescent scrape off layer(SOL).These conditions are beneficial to get higher lower hybrid current drive(LHCD)efficiency.Therefore,using lower hybrid waves(LHW)launched from the HFS for current drive is a potential solution.In this paper,GENRAY / CQL3 D code is used to compare HFS and LFS LHCD.The simulation results show that there is no advantage of HFS LHCD when the overall electron density is small or under the electron density distribution of the non-density platform.With the increase of the overall electron density,the advantages of HFS LHCD gradually appear.The total driving current of the LHW launched form HFS gradually exceeds the LHW launched form LFS.And the radial distribution range of the current is closer to the plasma center than current generation by LFS LHW.Taking consideration of the impact of the SOL,the simulation is based on the difference in density distribution in the SOL on HFS and LFS.The simulation results show that the power loss of the LHW on the LFS SOL is much greater than on the LFS SOL.Simulations were performed by increasing the strength of the toroidal magnetic field.The results show that increasing the strength ofthe magnetic field can effectively improve the ability of LHW to penetrate into the plasma core.LHW launched from the HFS deposits energy closer to the plasma center.Increasing plasma pressure of magnetic equilibrium configuration in the same proportion when the electron density is increased,the results show that HFS lower hybrid current drive effect better than LFS.The above results indicate that under the condition of high electron density distribution,the HFS LHCD has a better current driving effect than the traditional LFS LHCD,which is worthy of further research and promotion.