  Spin waves, or magnons, in the anti-ferromagnetic $\alpha$ phase of solid
oxygen provide a novel mechanism for ultra-cold neutron (UCN) production.
Magnons dominate the energy exchange mechanisms for cold neutrons and UCN in
solid $\alpha$-oxygen, much in the same way as do phonons in solid deuterium
superthermal UCN sources. We present calculations of UCN production and
upscattering rates in S-O$_2$. The results indicate that S-O$_2$ is potentially
a much more efficient UCN source material than solid deuterium.
