Supersource of Ultracold Neutrons at WWR-M Reactor in Pnpi and the Research Program on Fundamental Physics

Serebrov, A. P.; Boldarev, S. T.; Erykalov, A. N.; Ежов, В. Ф.; Федоров, В. В.; Fomin, A. K.; Ilatovskiy, V. A.; Keshyshev, K.O.; Konoplev, K. A.; Krivshitch, A.G.; Марченко, В. И.; Mityuklyaev, V.A.; Onegin, M. S.; Orlov, S. P.; Samsonov, V.; Захаров, А. А.

doi:10.1016/j.phpro.2011.06.044

Cited by 13 publications

(9 citation statements)

References 9 publications

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“…Optimizing a UCN source design to allow sufficient heat removal from the UCN converter, or to allow optical or pumping access, while maintaining low UCN transport loss is a common problem, in particular for He-II based sources under high heat loads. 28,29,31,32 The heat exchanger (also due to materials typically used) will need to be in a low radiation area so unwanted heating due to activation is reduced. Sufficient space between the heat exchanger and the tungsten target will be required for shielding.…”

Section: A Heat Removal With Ucn Extraction Guidementioning

confidence: 99%

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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Section: A Heat Removal With Ucn Extraction Guidementioning

confidence: 99%

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 next generation of neutron electric dipole moment (nEDM) experiments aim to measure the nEDM d n with proposed precision δd n 10 −27 e·cm [1,2,3,4,5,6,7,8]. In the previous best experiment [9,10] which discovered d n < 3.0 × 10 −26 e·cm (90% C.L), effects related to magnetic field homogeneity and instability were found to dominate the systematic error.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of fields generated within magnetically shielded volumes to changes in magnetic permeability

Andalib

Martin

Bidinosti

et al. 2017

Nuclear Instruments and Methods in Physics Research Section A:

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Future experiments seeking to measure the neutron electric dipole moment (nEDM) require stable and homogeneous magnetic fields. Normally these experiments use a coil internal to a passively magnetically shielded volume to generate the magnetic field. The stability of the magnetic field generated by the coil within the magnetically shielded volume may be influenced by a number of factors. The factor studied here is the dependence of the internally generated field on the magnetic permeability µ of the shield material. We provide measurements of the temperature-dependence of the permeability of the material used in a set of prototype magnetic shields, using experimental parameters nearer to those of nEDM experiments than previously reported in the literature. Our measurements imply a range of 1 µ dµ dT from 0-2.7%/K. Assuming typical nEDM experiment coil and shield parameters gives µ B0 dB0 dµ = 0.01, resulting in a temperature dependence of the magnetic field in a typical nEDM experiment of dB0 dT = 0 − 270 pT/K for B 0 = 1 µT. The results are useful for estimating the necessary level of temperature control in nEDM experiments.

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“…Ultra-Cold Neutrons (UCN) provide a good means to search for a nEDM. As a result, there are various nEDM experiments around the world utilizing UCN that are either running or being planned [2][3][4][5][6][7][8][9][10][11]. Measurements are limited mainly by UCN statistics.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a scintillating lithium glass ultra-cold neutron detector

et al. 2017

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A6 Li glass based scintillation detector developed for the TRIUMF neutron electric dipole moment experiment was characterized using the ultra-cold neutron source at the Paul Scherrer Institute (PSI). The data acquisition system for this detector was demonstrated to perform well at rejecting backgrounds. An estimate of the absolute efficiency of background rejection of 99.7 ± 0.1% is made. For variable ultra-cold neutron rate (varying from < 1 kHz to approx. 100 kHz per channel) and background rate seen at the Paul Scherrer Institute, we estimate that the absolute detector efficiency is 89.7 +1.3 −1.9 %. Finally a comparison with a commercial Cascade detector was performed for a specific setup at the West-2 beamline of the ultra-cold neutron source at PSI.

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Supersource of Ultracold Neutrons at WWR-M Reactor in Pnpi and the Research Program on Fundamental Physics

Cited by 13 publications

References 9 publications

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

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

Sensitivity of fields generated within magnetically shielded volumes to changes in magnetic permeability

Characterization of a scintillating lithium glass ultra-cold neutron detector

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