1. CAS Key Laboratory of Geospace Environment and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
2. KTX Laboratory and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
3. Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA