Pohl Institute of Solid State Physics Tongji University Shanghai 200092 China;
Pohl Institute of Solid State Physics Tongji University Shanghai 200092 China;
Pohl Institute of Solid State Physics Tongji University Shanghai 200092 China;
China National Center for Quality Supervision and Test of Electric Wire and Cable Shanghai 200093 China;
Pohl Institute of Solid State Physics Tongji University Shanghai 200092 China;
space charge; cross-linked polyethylene; IR;