Spectroscopic Study of Scattering of UCN by Liquid He4
We report on our first recent measurements of the energy spectrum of upscattered Ultra-Cold-Neutrons in liquid He4 at temperatures around 1 Kelvin. The measurements were made on the Superthermal UCN Source at the ILL . This source produces UCN’s in liquid He4 by down-scattering (phonon-emission) of 10 Å neutrons. The UCN’s produced in this way are stored in the He4 container, since they are totally reflected from the walls. The UCN’s can gain energy through scattering by Phonons  and Rotons , and hence leave the container. We have measured the spectrum of these upscattered neutrons by using a pseudo statistical chopper . The first preliminary measurements show a discrepancy with the spectrum expected on the basis of phonon and roton scattering.
KeywordsScattered Neutron Recent Measurement Preliminary Measurement Hydrodynamic Limit Cold Neutron
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