1. School of Physics East China University of Science and Technology Shanghai 200237 P. R. China
2. State Key Laboratory of Space Power‐Sources Technology Shanghai Institute of Space Power‐Sources Shanghai 200245 P. R. China
3. Lanzhou Institute of Physics Lanzhou 730000 P. R. China
4. School of Mechanical and Power Engineering East China University of Science and Technology Shanghai 200237 P. R. China