1. Institute of Modern physics, Chinese Academy of Sciences, 509 Nanchang Rd., Lanzhou 730000, China
2. University of Chinese Academy of Sciences, 19A Yuquan Rd., Beijing 100049, China
3. Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA
4. Engineering Research Center of New Energy Technology of Jiangxi Province, East China Institute of Technology, Nanchang 330013, China