Investigating solid $α-^{15}$N$_{2}$ as a new source of ultra-cold neutrons

Abstract

The dynamical structure factor of solid 15 N 2 in the α phase (T < 35K) is measured at the IN4 timeof-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 incident energy, as well as the up-scattering mean free path. The UCN production cross-section is found to be approximately 20% of that of deuterium. However, UCN with energy 181 neV have an up-scattering mean free path of 46 cm at T = 5.9 K, which is ∼ 20 times larger than deuterium. Therefore, a large volume α− 15 N 2 source may produce an improved UCN density if sufficient isotopic purity can be achieved.