Affiliation: | [1]China Institute of Atomic Energy, PO Box 275-50, Beijing 102413 [2]Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan [3]Fukui University of Technology, Fukui 910-8505, Japan [4]Department of Physics, College of Humanities and Sciences, Nihon University, Sakurajosui 3-25-40, Setagaya-ku, Tokyo 156, Japan |