UCN Source at an External Beam of Thermal Neutrons

Лычагин, Е. В.; Muzychka, A. Yu.; Nekhaev, G. V.; Nesvizhevsky, V. V.; Sharapov, É. I.; Strelkov, A. V.

doi:10.1155/2015/547620

Cited by 11 publications

(8 citation statements)

References 22 publications

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“…The next major neutron source will be the European Spallation Source (ESS). The ESS will provide an opportunity for new UCN source possibilities with even greater densities for future experiments, and a number of UCN source concepts have been developed (Klinkby et al, 2014;Lychagin et al, 2015;Nesvizhevsky, 2014;Pendlebury and Greene, 2014;. The goal of these proposals is 10 3 -10 4 UCN/cm 3 .…”

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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“…We showed in ref. [1] that solid methane (CH4) in phase II at the temperature of ~ 4K is among best materials for moderators-reflectors for such UCN sources. [8,9]).…”

Section: Ucn Source With Methane Moderatormentioning

confidence: 99%

“…A new concept of super-thermal liquid-helium ( 4 He) UCN sources is presented in ref. [1]. Such sources can be installed in beams of thermal neutrons; thus at ILL (Grenoble) or PIK (Gatchina) such a source would provide parameters highly exceeding those of existing UCN sources.…”

Section: Introductionmentioning

confidence: 99%

“…The present work develops ref. [1], considers source parameters in more detail, and applies the new concept to the PIK reactor. Note, however, that such a UCN source can be installed at any other thermal neutron source as well.…”

Section: Introductionmentioning

confidence: 99%

“…The new concept [1] consists of installing a 4 He UCN source in a beam of thermal or cold neutrons at the edge of the biological shielding and surrounding the source with a moderatorreflector (see Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

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UCN sources at external beams of thermal neutrons. An example of PIK reactor

Лычагин

Mityukhlyaev

Muzychka

et al. 2016

Nuclear Instruments and Methods in Physics Research Section A:

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. AbstractWe consider ultracold neutron (UCN) sources based on a new method of UCN production in superfluid helium ( 4 He). The PIK reactor is chosen as a perspective example of the application of this idea, which consists of installing a 4 He UCN source in a beam of thermal or cold neutrons and surrounding the source with a moderator-reflector, which plays the role of a source of cold neutrons (CNs) feeding the UCN source. The CN flux in the source can be several times larger than the incident flux, due to multiple neutron reflections from the moderator-reflector. We show that such a source at the PIK reactor would provide an order of magnitude larger density and production rate than an analogous source at the ILL reactor.We estimate parameters of a 4 He source with solid methane (CH4) or/and liquid deuterium (D2) moderator-reflector. We show that such a source with CH4 moderator-reflector at the PIK reactor would provide the UCN density of ~110 5 cm -3 , and the UCN production rate of ~210 7 s -1 . These values are respectively 1000 and 20 times larger than those for the most intense UCN user source. The UCN density in a source with D2 moderator-reflector would reach the value of ~210 5 cm -3 , and the UCN production rate would be equal ~810 7 s -1. Installation of such sources in beams of CNs with equal flux would slightly increase the density and production rate. IntroductionA new concept of super-thermal liquid-helium ( 4 He) UCN sources is presented in ref.[1]. Such sources can be installed in beams of thermal neutrons; thus at ILL (Grenoble) or PIK (Gatchina) such a source would provide parameters highly exceeding those of existing UCN sources. The present work develops ref.[1], considers source parameters in more detail, and applies the new concept to the PIK reactor. Note, however, that such a UCN source can be installed at any other thermal neutron source as well.The idea of 4 He UCN sources was proposed in 1975 in ref.[2]; it is based on neutron scattering in liquid 4 He accompanied with exciting phonons with the energy of 1.02 meV. If the incident neutron energy is slightly higher than 1.02 meV then the cold neutron (CN) is converted into a UCN. As the UCN energy is lower than ~300 neV, only CNs from a very narrow energy range contribute to the UCN production. Cross-sections of simultaneously exciting two or more phonons are lower by a few orders of magnitude. However, the energy of excited phonons is found in a broad range, thus UCNs are produced via multi-phonon processes from a broad spectrum of incident neutrons. Therefore total contributions of one-phonon and multi-phonon process are comparable if the incident neutron spectrum is broad.Work [2] showed also that produced UCNs can live for a long time in superfluid 4 He if its temperature is below 1K. Long lifetimes of UCNs allow accumulating them up to high densities. Neutron storage time changes sharply as a function of helium temperature. It equals to the neutron lifetime ~880 s at the temperature of 0.8 K, it is 10 times longer than that a...

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