1. State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
2. Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China
3. Suzhou Nuclear Power Research Institute, Suzhou 215004, People's Republic of China