Investigating solid α-¹⁵N₂ as a new source of ultra-cold neutrons

¹ Physics Department and Center for Exploration of Energy and Matter, Indiana University Bloomington, IN 47405, USA
² Physik-Department, Technische Universität Munchen - James-Franck-Str., D-85747 Garching, Germany, EU
³ Institut Laue Langevin - 6 Rue Jules Horowitz, F-38042 Grenoble CEDEX9, France, EU
⁴ Dipartimento di Fisica, Università di Perugia - I-06123 Perugia, Italy, EU

Received: 15 May 2013
Accepted: 14 June 2013

Abstract

The dynamical structure factor of solid ¹⁵N₂ in the α phase () is measured at the IN4 time-of-flight spectrometer at the Institut Laue Langevin, and the potential performance of this substance as a UCN converter is assessed. The cross-section to down-scatter neutrons to ultra-cold–neutron energies is determined as a function of the incident energy, as well as the up-scattering mean free path. The UCN production cross-section is found to be approximately of that of deuterium. However, UCN with energy 181 neV have an up-scattering mean free path of 46 cm at , which is times larger than deuterium. Therefore, a large volume α-¹⁵N₂ source may produce an improved UCN density if sufficient isotopic purity can be achieved.