An Apparatus to Control and Monitor the Para-D2 Concentration in a Solid Deuterium, Superthermal Source of Ultra-cold Neutrons

Abstract

Controlling and measuring the concentration of para-D2 is an essential step toward realizing solid deuterium as an intense ultra-cold neutron (UCN) source. To this end, we implemented an experimental technique to convert para- to ortho-deuterium molecules by flowing D2 gas through a cryogenic cell filled with paramagnetic hydrous ferric oxide granules. This process efficiently reduced the para-D2 concentration from 33.3% to 1.5%. Rotational Raman spectroscopy was applied to measure the residual para-D2 contamination to better than 2 parts in 10^3, and the hydrogen contamination to 1 part in 10^3. We also contrast our optical technique to conventional thermal conductivity measurements of the para-D2 concentration, reporting some of the relevant strengths and weaknesses of our implementation of each technique.

accepted for publication in NIMA

References in corpus (1)

• Measurements of ultracold neutron lifetimes in solid deuterium

Cited by in corpus (6)

• Electric Dipole Moments of the Atoms, Molecules, Nuclei and Particles
• Demonstration of a solid deuterium source of ultra-cold neutrons
• Measurement of the neutron $\beta$-asymmetry parameter $A_0$ with ultracold neutrons
• Ultracold Neutron Production in a Pulsed Neutron Beam Line
• UCN transport simulation in solid deuterium crystals
• Investigating solid $\alpha {-}^{15}$N${}_2$ as a new source of ultra-cold neutrons