1. National Key Laboratory of Science and Technology on Vacuum Electronics, School of Electronic Science and Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, China
2. Guoli Vacuum (GLVAC) Industrial Technology Research Institute of High Power Devices Company Ltd., Suzhou, China
3. Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang, China
4. Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM, USA
5. Department of Electronics Engineering, Indian Institute of Technology-BHU, Banaras Hindu University (BHU), Varanasi, India