作者机构:[1]Qinghai University, Xining 810016, People's Republic of China, [2]Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031, People's Republic of China
相关基金:The authors gratefully acknowledge the NBI team and the partial support of National Natural Science Foundation of China (No. 61363019), and National Natural Science Foun- dation of Qinghai Province (No. 2014-ZJ-718).