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Altarev, I.; Atchison, F.; Daum, M.; Frei, A.; Gutsmiedl, E.; Hampel, G.; Hartmann, F. J.; Heil, W.; Knecht, A.; Kratz, J. V.; Lauer, T.; Meier, Matthias M.; Paul, S.; Sobolev, Yu.; Wiehl, N.

doi:10.1103/physrevlett.100.014801

Cited by 17 publications

(11 citation statements)

References 20 publications

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“…This source is based on a very cold moderator-converter using solid deuterium (sD 2 ) [20][21][22][23][24][25][26][27][28][29][30][31][32][33] at a temperature around 5 K. (4) The initial polarization of the neutrons, which is increased to ∼100% by means of a superconductive solenoid with a field of 5 T [34]. (5) The simultaneous measurement of both spin states [35,36].…”

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Losses and depolarization of ultracold neutrons on neutron guide and storage materials

et al. 2017

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At Institut Laue-Langevin (ILL) and Paul Scherrer Institute (PSI), we have measured the losses and depolarization probabilities of ultracold neutrons on various materials: (i) nickel-molybdenum alloys with weight percentages of 82/18, 85/15, 88/12, 91/9, and 94/6 and natural nickel Ni100, (ii) nickel-vanadium NiV93/7, (iii) copper, and (iv) deuterated polystyrene (dPS). For the different samples, storage-time constants up to ∼460 s were obtained at room temperature. The corresponding loss parameters for ultracold neutrons, η, varied between 1.0 × 10 −4 and 2.2 × 10 −4 . All η values are in agreement with theory except for dPS, where anomalous losses at room temperature were established with four standard deviations. The depolarization probabilities per wall collision β measured with unprecedented sensitivity varied between 0.7 × 10 −6 and 9.0 × 10 −6 . Our depolarization result for copper differs from other experiments by 4.4 and 15.8 standard deviations. The β values of the paramagnetic NiMo alloys over molybdenum content show an increase of β with increasing Mo content. This is in disagreement with expectations from literature. Finally, ferromagnetic behavior of NiMo alloys at room temperature was found for molybdenum contents of 6.5 at.% or less and paramagnetic behavior for more than 8.7 at.%. This may contribute to solving an ambiguity in literature.

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Losses and depolarization of ultracold neutrons on neutron guide and storage materials

et al. 2017

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“…We remind the reader that UCN gain about 100 neV in kinetic energy when exiting from the sD 2 due to its neutron optical potential [45]. Therefore, the UCN energies at the lid position starts at 100 neV.…”

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confidence: 98%

Neutron optics of the PSI ultracold-neutron source: characterization and simulation

et al. 2020

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The ultracold neutron (UCN) source at the Paul Scherrer Institute serves mainly experiments in fundamental physics. High UCN intensities are the key for progress and success in such experiments.A detailed understanding of all source parameters is required for future improvements. Here we present the UCN source components, elements of the neutron optics, the characterization of important related parameters like emptying times, storage times or transmission probabilities of UCN which are ultimately defining the UCN intensity delivered at the beamports. We also introduce a detailed simulation model of the PSI UCN source, used to analyze the measurements and to extract surface parameters.

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“…This results in a relative shift of the UCN energy spectra at the two beamports. UCN which can reach the higher beamport have a minimum energy of 320 neV outside the sD 2 surface, while UCN at West-1 have a minimum energy of 113 neV, similar to the kinetic energy boost by the sD 2 potential [45,46]. Both beamlines are equipped with identically produced UCN guides made from glass tubes with inside coating of nickel-molybdenum [47].…”

Section: Measurements At the Psi Facilitymentioning

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Solid deuterium surface degradation at ultracold neutron sources

et al. 2018

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Solid deuterium (sD2) is used as an efficient converter to produce ultracold neutrons (UCN). It is known that the sD2 must be sufficiently cold, of high purity and mostly in its ortho-state in order to guarantee long lifetimes of UCN in the solid from which they are extracted into vacuum. Also the UCN transparency of the bulk sD2 material must be high because crystal inhomogeneities limit the mean free path for elastic scattering and reduce the extraction efficiency. Observations at the UCN sources at Paul Scherrer Institute and at Los Alamos National Laboratory consistently show a decrease of the UCN yield with time of operation after initial preparation or later treatment ("conditioning") of the sD2. We show that, in addition to the quality of the bulk sD2, the quality of its surface is essential. Our observations and simulations support the view that the surface is deteriorating due to a build-up of D2 frost-layers under pulsed operation which leads to strong albedo reflections of UCN and subsequent loss. We report results of UCN yield measurements, temperature and pressure behavior of deuterium during source operation and conditioning, and UCN transport simulations. This, together with optical observations of sD2 frost formation on initially transparent sD2 in offline studies with pulsed heat input at the North Carolina State University UCN source results in a consistent description of the UCN yield decrease.

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Direct Experimental Verification of Neutron Acceleration by the Material Optical Potential of SolidH22

Cited by 17 publications

References 20 publications

Losses and depolarization of ultracold neutrons on neutron guide and storage materials

Losses and depolarization of ultracold neutrons on neutron guide and storage materials

Neutron optics of the PSI ultracold-neutron source: characterization and simulation

Solid deuterium surface degradation at ultracold neutron sources

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