Understanding of ultra-cold–neutron production in solid deuterium
Technische Universität München, Physik Department - James-Franck-Str.1 - D-85748 Garching, Germany, EU
2 Institut Laue Langevin - 156X, F-38042 Grenoble Cedex, France, EU
3 Technische Universität München, Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II) - Lichtenbergstr. 1, D-85748 Garching, Germany, EU
Accepted: 3 December 2010
Our recent neutron scattering measurements of phonons and other quasi-particle excitations in solid deuterium (sD2) and the extraction of the density of states for phonons and rotational transitions in sD2 have led us to a new understanding of the production of ultra-cold neutrons (UCN) in sD2. The UCN production rate reaches a maximum at an equivalent neutron temperature of Tn = 40 K for a neutron flux with Maxwellian energy distribution. The cross-section for UCN production in sD2 has been determined by using the density of states G1(E) in combination with the incoherent approximation as well as by a direct calibration of our measured neutron cross-sections with the known cross-section of the J = 1↦0 rotational transition in deuterium. Using this cross-section we deduced the production rate of UCN in sD2 which agrees quite well with direct measurements of this energy averaged UCN production cross-section.
PACS: 28.20.Cz – Neutron scattering / 63.20.kk – Phonon interactions with other quasiparticles
© EPLA, 2010