1. Department of Engineering Physics and Key Laboratory of Particle and Radiation Imaging (Tsinghua University) of Ministry of Education, Tsinghua University, Beijing 100084, China
2. School of Physics Science and Engineering & School of Mechanical Engineering, Tongji University, Shanghai 200092, China
3. Dongguan Neutron Science Center, Dongguan 523803 and Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China