1998年 Challenge on 48Ca Enrichment for CANDLES Double Beta Decay Experiment The International Conference of Vietnam 2006(VIth Rencontres du Vietnam: Nanophysics and Particle astrophysics) R. Hazama, Y. Tatewaki, T. Kishimoto, K. Matsuoka, N. Endo, K. Kume, Y. Shibahara, and M. Tanimizu