Neutron production and thermal moderation at the PSI UCN source

Becker, Henrik; Bison, G.; Blau, B.; Chowdhuri, Z.; Eikenberg, J.; Fertl, M.; Kirch, K.; Lauss, B.; Perret, G.; Reggiani, D.; Ries, D.; Schmidt-Wellenburg, P.; Talanov, V.; Wohlmuther, M.; Zsigmond, G.

doi:10.1016/j.nima.2014.12.091

Cited by 16 publications

(13 citation statements)

References 14 publications

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“…At PSI (Anghel et al, 2009), the cyclotron provides a 2.2 mA, 590 MeV proton beam incident on a heavy metal spallation target for 4 s with a duty cycle of 1%. Measurements with a "standard" storage bottle showed 22 UCN/cm 3 of unpolarized UCN (Becker et al, 2015). Another pulsed sD 2 source is installed at the pulsed TRIGA reactor in Mainz, where a 200 MW-20 ms neutron pulse produces UCN, which leave the source quickly and canwith proper timing -be captured in an experiment using mechanical shutters.…”

Section: Ultra-cold Neutron Sourcesmentioning

confidence: 99%

Electric dipole moments of atoms, molecules, nuclei, and particles

et al. 2019

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A permanent electric dipole moment (EDM) of a particle or system is a separation of charge along its angular-momentum axis and is a direct signal of T-violation and, assuming CPT symmetry, CP violation. For over sixty years EDMs have been studied, first as a signal of a parity-symmetry violation and then as a signal of CP violation that would clarify its role in nature and in theory. Contemporary motivations include the role that CP violation plays in explaining the cosmological matter-antimatter asymmetry and the search for new physics. Experiments on a variety of systems have become ever-more sensitive, but provide only upper limits on EDMs, and theory at several scales is crucial to interpret these limits. Nuclear theory provides connections from Standard-Model and Beyond-Standard-Model physics to the observable EDMs, and atomic and molecular theory reveal how CP-violation is manifest in these systems. EDM results in hadronic systems require that the Standard Model QCD parameter ofθ must be exceptionally small, which could be explained by the existence of axions -also a candidate darkmatter particle. Theoretical results on electroweak baryogenesis show that new physics is needed to explain the dominance of matter in the universe. Experimental and theoretical efforts continue to expand with new ideas and new questions, and this review provides a broad overview of theoretical motivations and interpretations as well as details about experimental techniques, experiments, and prospects. The intent is to provide specifics and context as this exciting field moves forward.

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Section: Ultra-cold Neutron Sourcesmentioning

confidence: 99%

Electric dipole moments of atoms, molecules, nuclei, and particles

et al. 2019

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“…Neutron production and thermalization were checked using neutron activation measurements on gold. The observed activation was well reproduced in detailed neutron transport simulations using MCNP [18]. Neutron moderation was studied using tritium production in the solid D 2 moderator [24].…”

Section: Ucn Source Performancementioning

confidence: 85%

“…The PSI UCN source operates in the following way: The 590 MeV, 2.4 mA proton beam is deflected by a kicker magnet [16] for up to 8 s onto the lead spallation target (label 2) in Figure 4.1) [17]. In a spallation reaction between a lead nucleus and a 590 MeV proton, an average of 8 free neutrons is produced [18]. The neutrons are thermalized in the surrounding heavy water (label 4).…”

Section: Introductionmentioning

confidence: 99%

UCN, the ultracold neutron source -- neutrons for particle physics

Lauss

Blau

2021

SciPost Phys. Proc.

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Ultracold neutrons provide a unique tool for the study of neutron properties. An overview is given of the ultracold neutron (UCN) source at PSI, which produces the highest UCN intensities to fundamental physics experiments by exploiting the high intensity proton beam in combination with the high UCN yield in solid deuterium at a temperature of 5 K. We briefly list important fundamental physics results based on measurements with neutrons at PSI.

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“…The UCN source at PSI is based on spallation of lead using the full 1.3 MW, 590 MeV proton beam [38] directed onto the UCN spallation target [39] for up to 8 s. Spallation neutrons are subsequently thermalized in heavy water, a process that is well understood and modeled in a full MCNP-X simulation [30] containing all important geometry details of the target and moderator area of the UCN source. Thermal neutrons can then enter the moderator vessel cooled to 5 K containing about 30 dm 3 of solid ortho-deuterium, where they are moderated to cold neutrons.…”

Section: Measurements At the Psi Facilitymentioning

confidence: 99%

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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Neutron production and thermal moderation at the PSI UCN source

Cited by 16 publications

References 14 publications

Electric dipole moments of atoms, molecules, nuclei, and particles

Electric dipole moments of atoms, molecules, nuclei, and particles

UCN, the ultracold neutron source -- neutrons for particle physics

Solid deuterium surface degradation at ultracold neutron sources

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