Superfluid-helium Ultracold Neutron Sources: Concepts for the European Spallation Source?

Zimmer, O.

doi:10.1016/j.phpro.2013.12.019

Cited by 8 publications

(5 citation statements)

References 25 publications

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“…This strongly contrasts with the dispersive single-phonon emission process in superfluid 4 He, which, for instance for a spectrum up to a cutoff at E c = 250 neV, is kinematically allowed in a wide energy range of 26 µeV about 1 meV [63]. While for the helium case the large mean free path of neutrons with energy 1 meV can in principle be used to enhance the UCN density by a neutron beam resonator [64,65], the paramagnetic moderator with its narrow energy range for neutron conversion is amenable to beam bunching techniques applicable for pulsed neutron sources, as described in ref. [66].…”

Section: Discussionmentioning

confidence: 95%

Cooling neutrons using non-dispersive magnetic excitations

Zimmer

2014

Preprint

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A new method is proposed for cooling neutrons by inelastic magnetic scattering in weakly absorbing, cold paramagnetic systems. Kinetic neutron energy is removed in constant decrements determined by the Zeeman energy of paramagnetic atoms or ions in an external magnetic field, or by zero-field level splittings in magnetic molecules. Analytical solutions of the stationary neutron transport equation are given using inelastic neutron scattering cross sections derived in an appendix. They neglect any inelastic process except the paramagnetic scattering and hence still underestimate very-cold neutron densities. Molecular oxygen with its triplet ground state appears particularly promising, notably as a host in fully deuterated O 2 -clathrate hydrate, or more exotically, in dry O 2 -4 He van der Waals clusters. At a neutron temperature about 6 K, for which neutron conversion to ultra-cold neutrons by single-phonon emission in pure superfluid 4 He works best, conversion rates due to paramagnetic scattering in the clathrate are found to be a factor 9 larger. While in conversion the neutron imparts only a single energy quantum to the medium, the multi-step paramagnetic cooling cascade leads to further strong enhancements of very-cold neutron densities, e.g., by a factor 14 (57) for an initial neutron temperature of 30 K (100 K), for the moderator held at about 1.3 K. Due to a favorable Bragg cutoff of the O 2 -clathrate the cascade-cooling can take effect in a moderator with linear extensions smaller than a meter. The paramagnetic cooling mechanism may offer benefits in novel intense sources of very cold neutrons and for enhancing production of ultra-cold neutrons.

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Section: Discussionmentioning

confidence: 95%

Cooling neutrons using non-dispersive magnetic excitations

Zimmer

2014

Preprint

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“…For SD 2 at 5 K, it is about 40 ms [29,56]. For He-II, assuming UCN accumulation in a converter vessel with material walls, it is given by the expression [229] τ…”

Section: Ucn Productionmentioning

confidence: 99%

“…In general, experiments involving a large vessel, such as some neutron lifetime experiments, often aim at maximizing N UCN,EXP . Certain other experiments relying on extreme suppression of systematic effects, such as nEDM experiments, are preferably done with smaller vessels, in which a high value of ρ UCN,EXP is then crucial [229]. -Total (saturated) number of UCNs in the storage vessel N UCN,EXP .…”

Section: Ucn Productionmentioning

confidence: 99%

HighNESS conceptual design report: Volume I

Santoro,

Abou El Kheir,

Acharya

et al. 2024

JNR

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The European Spallation Source, currently under construction in Lund, Sweden, is a multidisciplinary international laboratory. Once completed to full specifications, it will operate the world’s most powerful pulsed neutron source. Supported by a 3 million Euro Research and Innovation Action within the EU Horizon 2020 program, a design study (HighNESS) has been completed to develop a second neutron source located below the spallation target. Compared to the first source, designed for high cold and thermal brightness, the new source has been optimized to deliver higher intensity, and a shift to longer wavelengths in the spectral regions of cold (CN, 2–20 Å), very cold (VCN, 10–120 Å), and ultracold (UCN, >500 Å) neutrons. The second source comprises a large liquid deuterium moderator designed to produce CN and support secondary VCN and UCN sources. Various options have been explored in the proposed designs, aiming for world-leading performance in neutronics. These designs will enable the development of several new instrument concepts and facilitate the implementation of a high-sensitivity neutron-antineutron oscillation experiment (NNBAR). This document serves as the Conceptual Design Report for the HighNESS project, representing its final deliverable.

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“…Several options for sources of ultra-cold neutrons (UCN) at spallation sources have been discussed at the ESS Science Symposium on Neutron Particle Physics at Long Pulse Spallation Sources, NPPatLPS, held in 2013 at LPSC in Grenoble [7][8][9][10]. They commonly use superfluid helium (He-II) as a medium for conversion of meV cold neutrons to the UCN energy range of typically 100 neV. UCN production in a He-II converter relies on the possibility of nearly entire neutron energy loss in single scattering events, mostly via a one-phonon process induced by neutrons of 8.9 Åwavelength [11] .…”

Section: Source For Ultra-cold Neutronsmentioning

confidence: 99%

Development of High Intensity Neutron Source at the European Spallation Source

Santoro¹,

Andersen²,

DiJulio³

et al. 2020

Preprint

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The European Spallation Source being constructed in Lund, Sweden will provide the user community with a neutron source of unprecedented brightness. By 2025, a suite of 15 instruments will be served by a high-brightness moderator system placed above the spallation target. The ESS infrastructure, consisting of the proton linac, the target station, and the instrument halls, allows for implementation of a second source below the spallation target. We propose to develop a second neutron source with a high-intensity moderator able to (1) deliver a larger total cold neutron flux, (2) provide high intensities at longer wavelengths in the spectral regions of Cold (4-10 Å), Very Cold (10-40 Å), and Ultra Cold (several 100 Å) neutrons, as opposed to Thermal and Cold neutrons delivered by the top moderator. Offering both unprecedented brilliance, flux, and spectral range in a single facility, this upgrade will make ESS the most versatile neutron source in the world and will further strengthen the leadership of Europe in neutron science. The new source will boost several areas of condensed matter research such as imaging and spin-echo, and will provide outstanding opportunities in fundamental physics investigations of the laws of nature at a precision unattainable anywhere else. At the heart of the proposed system is a volumetric liquid deuterium moderator. Based on proven technology, its performance will be optimized in a detailed engineering study. This moderator will be complemented by secondary sources to provide intense beams of Very-and Ultra-Cold Neutrons.

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Superfluid-helium Ultracold Neutron Sources: Concepts for the European Spallation Source?

Cited by 8 publications

References 25 publications

Cooling neutrons using non-dispersive magnetic excitations

Cooling neutrons using non-dispersive magnetic excitations

HighNESS conceptual design report: Volume I

Development of High Intensity Neutron Source at the European Spallation Source

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