1. State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
2. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, Anhui, China
3. School of Nuclear Science and Technology, University of South China, Hengyang 421001, Hunan, China
4. Dipartimento di Fisica ‘G. Occhialini’, Università degli Studi di Milano-Bicocca, Milano 20126, Italy
5. Institute for Plasma Science and Technology, National Research Council, Milan 20125, Italy