Production of Ultra-Cold-Neutrons in Solid \alpha-Oxygen

TL;DR

This paper investigates how ultra-cold neutrons are produced in solid alpha-oxygen, revealing phonons as the dominant mechanism and comparing its efficiency to solid deuterium.

Contribution

It provides new insights into the neutron scattering processes in solid alpha-oxygen and clarifies the roles of phonons and magnons in UCN production.

Findings

UCN production is dominated by phonon excitation.

Magnons contribute slightly at higher energies.

Solid alpha-oxygen is less efficient than solid deuterium for UCN production.

Abstract

Our recent neutron scattering measurements of phonons and magnons in solid \alpha-oxygen have led us to a new understanding of the production mechanismen of ultra-cold-neutrons (UCN) in this super-thermal converter. The UCN production in solid \alpha-oxygen is dominated by the excitation of phonons. The contribution of magnons to UCN production becomes only slightly important above E >10 meV and at E >4 meV. Solid \alpha-oxygen is in comparison to solid deuterium less effcient in the down-scattering of thermal or cold neutrons into the UCN energy regime.