1. School of Electrical Engineering and Automation, Hefei University of Technology, Hefei 230009, China
2. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
3. Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550, USA
4. National Fusion Research Institute, Yuseong, Daejeon 305-333, South Korea
5. Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA