Ultracold neutrons extracted from a superfluid-helium converter coated with fluorinated grease O. Zimmer, P. Schmidt-Wellenburg, M. Fertl, H.-F. Wirth, M. Assmann, J. Klenke and B. van den Brandt Eur. Phys. J. C, 67 3-4 (2010) 589-599 Published online: 27 April 2010 DOI: 10.1140/epjc/s10052-010-1327-1