Distillation of Liquid Xenon to Remove Krypton
  A high performance distillation system to remove krypton from xenon was constructed, and a purity level of Kr/Xe = $\sim 3 \times 10^{-12}$ was achieved. This development is crucial in facilitating high sensitivity low background experiments such as the search for dark matter in the universe. 
K. Abe, J. Hosaka, T. Iida, M. Ikeda, K. Kobayashi, Y. Koshio, A.   Minamino, M. Miura, S. Moriyama, M. Nakahata, Y. Nakajim...