Eur. Phys. J. B 28, 299-304 (2002)
https://doi.org/10.1140/epjb/e2002-00233-7

Experimental study of quasi-elastic scattering of ultracold neutrons

¹ Department of Physics, University of Rhode Island, Kingston, RI 02881, USA
² Department of Physics, Harvard University, Cambridge, MA 02138, USA
³ Department of Neutron Research, Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia
⁴ Institut Laue-Langevin, 38042 Grenoble, France
⁵ Department of Physics, Graduate School of Science, Kyushu University, Fukuoka 812-8581, Japan
⁶ Laboratory of Neutron Physics, Joint Institut for Nuclear Research, 141980 Dubna, Russia

Corresponding author: ^a a_steyerl@uri.edu

Received: 13 March 2002
Published online: 31 July 2002

Abstract

Ultracold neutrons (UCN) are lost from traps if they are quasi-elastically scattered from the wall with an energy gain sufficient to exceed the Fermi potential for the wall. Possible mechanisms of a quasi-elastic energy transfer are, for instance, scattering from hydrogen diffusing in an impurity surface layer or on surface waves at a liquid wall. Using two different experimental methods at the UCN source of the Institut Laue-Langevin we have investigated both the energy-gain and the energy-loss side of quasi-elastic UCN scattering on Fomblin grease coated walls. For Fomblin oil and similar new types of oil we report up-scattering data as a function of temperature and energy transfer. These low-temperature oils may be used in an improved measurement of the neutron lifetime, which requires extremely low wall reflection losses.