1. Institute for Fusion Theory and Simulation and School of Physics, Zhejiang University 1 , Hangzhou 310027, China
2. Renewable and Sustainable Energy Institute, Department of Physics, University of Colorado 2 , Boulder, Colorado 80309, USA
3. Department of Plasma Physics and Fusion Engineering, School of Nuclear Science and Technology, University of Science and Technology of China 3 , Hefei 230026, China