作者机构:Southwestern Institute of Physics, Chengdu 610041, China
相关基金:supported by the National Magnetic Confinement Fusion Science Program of China(No.2014GB109001); National Natural Science Foundation of China(Nos.11505053 and 11275059)Acknowledgments The authors would like to express thanks to Dr. X. Q. Ji, W. L. Zhong and the HL-2A team for their data support in this work.