1. Fusion Simulation Center, Peking University, Beijing 100871, People's Republic of China
2. School of Physics, Nankai University, Tianjin 300071, People's Republic of China
3. University of California, Irvine, California 92697, USA
4. Sichuan University, Chengdu 610064, People's Republic of China
5. Southwestern Institute of Physics, Chengdu 610041, People's Republic of China
6. Harbin Institute of Technology, Harbin 150001, People's Republic of China