1. Shenzhen University, College of Physics and Optoelectronic Engineering, Shenzhen 518060, China
2. Chinese Academy of Sciences, Institute of Plasma Physics, Hefei 230031, China
3. Lappeenranta University of Technology, Lappeenranta 53810, Finland
4. Anhui Province Key Laboratory of Special Welding Technology, Huainan 232000, China