1. International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics, State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
2. Fiat Lux, San Diego, California, USA and 9500 Gilman Dr., La Jolla, California 92093-0417, USA
3. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
4. Forschungszentrum Jülich GmbH, Institut für Energie-und Klimaforschung-Plasmaphysik, 52425 Jülich, Germany
5. Chengdu University, Chengdu 610106, China