1. Blackett Laboratory, Imperial College, London SW7 2BW, United Kingdom
2. Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, F-75005 Paris, France
3. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4. West Virginia University, Morgantown, West Virginia 26506, USA
5. Northwest Institute of Nuclear Technology, Xi'an 710024, China