1. Key Laboratory of Radiation Physics and Technology of Ministry of Education; Institute of Nuclear Science and Technology; Sichuan University; Chengdu 610064 P. R. China
2. Yibin University; 8 Jiusheng Road Yibin 644000 P. R. China
3. The Second Research Institute of Civil Aviation Administration of China (CAAC); Chengdu 610064 P. R. China