1. Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Physics, Dalian University of Technology, Dalian 116024, China
2. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
3. Tech-X Corporation, Boulder, Colorado 80303, USA
4. Center for Integrated Plasma Studies, University of Colorado, Boulder, Colorado 80305, USA
5. Aerospace Engineering Program, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA
6. High Voltage Laboratory, Electrical and Computer Engineering Department, University of Patras, Rion-Patras 26504, Greece