1. Chinese Academy of Sciences, Institute of Plasma Physics P.O. Box 1126, Hefei, Anhui, 230031, China
2. Xi’an Jiaotong University, Nuclear Reactor Division Energy & Power Engineering Department Xi’an, Sha’anxi, 710049, China
3. Forschungszentrum Karlsruhe, Institute of Neutron Physics and Reactor Technology P.O. 3640, D-76021, Karlsruhe, Germany