Spallation-driven Ultracold Neutron Sources: Concepts for a Next Generation Source

Young, A. R.; Huegle, Thomas; Makela, M.; Morris, C. L.; Muhrer, G.; Saunders, Alexander

doi:10.1016/j.phpro.2013.12.021

Cited by 4 publications

(8 citation statements)

References 12 publications

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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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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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“…49 used previously in Ref. 39, which is for He-II at 1.2 K, contains an error in the binning and is thus avoided here. The temperature-dependence and the shape of the differential UCN production function are described in Sec.…”

Section: Optimizing the Inverse Geometry Designmentioning

confidence: 99%

“…For the other materials used, we have restricted ourselves to those with known and vetted characteristics. For further improvements of our source design we are also exploring novel moderators, such as triphenylmethane 39 , and high albedo cold neutron reflectors, such as diamond nanoparticles. 63 Next we describe the parameters of our source that we systematically optimize: the LD 2 moderator thickness, the D 2 O pre-moderator thickness, and the tungsten target location relative to the He-II volume.…”

Section: Optimizing the Inverse Geometry Designmentioning

confidence: 99%

“…The geometry, which was briefly outlined in Ref. 39, is based on using a 40 L cylindrical volume of He-II for UCN production. Our design philosophy is to optimize the UCN production rate with the following constraints: (1) allow up to 1 MW spallation proton beam power with ∼ 800 MeV proton energy, (2) use state-of-the-art sub-cooled He-II systems at the temperature range T ≈ 1 − 2 K, and (3) operate with edge-cooling of a tungsten spallation target with water.…”

Section: Introductionmentioning

confidence: 99%

“…For the 1 MW proton power and 100 W He-II heat load design restrictions, in Ref. 39, P UCN = 7 × 10 8 s −1 was estimated for our initial inverse geometry design. In this paper, we describe optimizations with individual improvements of 10% from this design.…”

Section: Introductionmentioning

confidence: 99%

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A next-generation inverse-geometry spallation-driven ultracold neutron source

Leung

Muhrer

Hügle

et al. 2019

Journal of Applied Physics

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The concept of a next-generation spallation-driven ultracold neutron (UCN) source capable of delivering an integrated flux of ∼ 10 9 UCN s −1 is presented. A novel "inverse geometry" design is used with 40 liters of superfluid 4 He (He-II) as converter cooled with state-of-the-art sub-cooled cryogenic technology to ∼ 1.6 K. Our source design is optimized for a 100 W maximum thermal heat load constraint on the He-II and its vessel. In this paper, we first explore a modified Lujan-Center Mark-3 target for UCN production as a benchmark. We then present the baseline concept of our inverse geometry source design that gives a total UCN production rate in the converter of P UCN = 2.4 × 10 8 s −1 . In our inverse geometry, the spallation target is wrapped symmetrically around the cryogenic UCN converter to permit raster scanning the proton beam over a relatively large volume of tungsten spallation target to reduce the demand on the cooling requirements, which makes it reasonable to assume that water edge-cooling only is sufficient. Our design is refined in several steps to reach P UCN = 2.1 × 10 9 s −1 under our other restriction of 1 MW maximum available proton beam power. We then study effects of the He-II scattering kernel used as well as reductions in P UCN due to pressurization to reach a estimate of P UCN = 1.8 × 10 9 s −1 . Finally, we provide an estimate for the UCN extraction efficiency to show that the total extracted UCN rate out of the converter can be as large as R ex ≈ 6 × 10 8 s −1 for the He-II at 1.6 K out of a 18 cm diameter guide. The UCN extraction loss is dominated by upscattering in the He-II so that if the He-II can be cooled further to 1.4 K, R ex ≈ 8 × 10 8 s −1 can be attained. These extracted UCN rates are around an order of magnitude higher than the strongest proposed sources so far, and is around three orders of magnitude stronger than existing sources.He-II offers much higher thermal conductivities and a UCN upscattering time constant given by τ up ≈ (100 s K 7 )/T 7 (see Sec. VI), resulting in UCN loss times 3 s for a He-II bath at a temperature T = 1.6 K. At these temperatures, the total scattering mean-free-path for 8.9 Å (1 meV) neutrons, the primary UCN producing CN component, is ≈ 18 m. 25 This permits the design of a simple, large volume source where the converter material also serves as the coolant.There are two "in-pile" He-II sources currently under construction. One is at TRIUMF, Canada, where the source is coupled to a 500 MeV proton beam with 20 kW incident beam power. [26][27][28][29] The next generation version of this source will have an expected R ex ∼ 10 6 s −1 and UCN density deliverable to an experimental volume of ∼ 6, 000 cm −3 (both polarized).

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Effect of oxide films and structural inhomogeneities on transmission of ultracold neutrons through foils

Pokotilovski

2016

Eur. Phys. J. Appl. Phys.

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Spallation-driven Ultracold Neutron Sources: Concepts for a Next Generation Source

Cited by 4 publications

References 12 publications

Development of High Intensity Neutron Source at the European Spallation Source

Development of High Intensity Neutron Source at the European Spallation Source

A next-generation inverse-geometry spallation-driven ultracold neutron source

Effect of oxide films and structural inhomogeneities on transmission of ultracold neutrons through foils

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