Ultracold Neutron Production in a Pulsed Neutron Beam Line

Abstract

We present the results of an Ultracold neutron (UCN) production experiment in a pulsed neutron beam line at the Los Alamos Neutron Scattering Center. The experimental apparatus allows for a comprehensive set of measurements of UCN production as a function of target temperature, incident neutron energy, target volume, and applied magnetic field. However, the low counting statistics of the UCN signal expected can be overwhelmed by the large background associated with the scattering of the primary cold neutron flux that is required for UCN production. We have developed a background subtraction technique that takes advantage of the very different time-of-flight profiles between the UCN and the cold neutrons, in the pulsed beam. Using the unique timing structure, we can reliably extract the UCN signal. Solid ortho-D${}_2$ is used to calibrate UCN transmission through the apparatus, which is designed primarily for studies of UCN production in solid O${}_2$. In addition to setting the overall detection efficiency in the apparatus, UCN production data using solid D${}_2$ suggest that the UCN upscattering cross-section is smaller than previous estimates, indicating the deficiency of the incoherent approximation widely used to estimate inelastic cross-sections in the thermal and cold regimes.

References in corpus (8)

• An Improved Experimental Limit on the Electric Dipole Moment of the Neutron
• Neutron lifetime measurements using gravitationally trapped ultracold neutrons
• Demonstration of a solid deuterium source of ultra-cold neutrons
• Measurements of ultracold neutron lifetimes in solid deuterium
• UCN Upscattering rates in a molecular deuterium crystal
• Measurement of |Vcb| using B0 to D*l nu decays
• First Measurement of the Neutron $\beta$-Asymmetry with Ultracold Neutrons
• An Apparatus to Control and Monitor the Para-D2 Concentration in a Solid Deuterium, Superthermal Source of Ultra-cold Neutrons

Cited by in corpus (7)

• Continuous Centrifuge Decelerator for Polar Molecules
• A hydrogen leak-tight, transparent cryogenic sample container for ultracold-neutron transmission measurements
• Time-of-flight Fourier UCN spectrometer
• UCN transport simulation in solid deuterium crystals
• HighNESS Conceptual Design Report: Volume I
• Scattering of ultracold neutrons from rough surfaces of metal foils
• Coherent Neutron Scattering in Polycrystalline Deuterium and its Implications for Ultracold Neutron Production