Nested mirror optics for neutron extraction, transport, and focusing

Herb, Christoph; Zimmer, O.; Georgii, R.; Böni, P.

doi:10.1016/j.nima.2022.167154

Cited by 10 publications

(14 citation statements)

References 43 publications

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“…Such systems image the beam by two reflections, one for each transverse A first experimental demonstration of a single-planar elliptic NMO and a discussion of further applications of NMO for neutron delivery and beam focusing can be found in Ref. [16]. To be noted is also that the NMO discussed here are conceptually simpler than (and involve only half of the reflections occurring in) Wolter imaging systems.…”

Section: Advanced Neutron Delivery Systems For In-beam Ucn Sourcesmentioning

confidence: 99%

“…There, the "partially integrated brilliance transfer" B (see Ref. [16] for a precise definition) is plotted on the vertical axis as a function of focal length. B gives a quantitative measure of the device's ability to image neutrons from a horizontal slit of height h centered on the focal line M (not a focal point as in the 2-D picture of Fig.…”

Section: Advanced Neutron Delivery Systems For In-beam Ucn Sourcesmentioning

confidence: 99%

“…Partially integrated brilliance transfer B, defined in Ref. [16], for a single-planar elliptic NMO scaled in proportion to the separation 2f , where f is the focal length (see the text). Solid and dashed curves correspond to simulations with and without gravity, respectively.…”

Section: Advanced Neutron Delivery Systems For In-beam Ucn Sourcesmentioning

confidence: 99%

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In-beam superfluid-helium ultracold neutron source for the ESS

Zimmer

Bigault

Degenkolb

et al. 2023

JNR

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This paper discusses design principles and possible performances of an “in-beam” ultracold neutron (UCN) source for the European Spallation Source (ESS). The key components of the proposed neutron delivery system are nested-mirror optics (NMO), which image the bright neutron emission surface of the large liquid-deuterium moderator, studied within the HighNESS project, onto a remotely located superfluid-helium converter. Bandpass supermirrors, with optional polarization capability, enable the selective transport of those neutrons that are most effective for UCN production, exploiting the single-phonon conversion process that is possible for neutrons having wavelengths within a narrow range centered on 8.9 A ˚. NMO are capable of extracting and refocusing neutrons with small transport losses under the large solid angle available at the ESS Large Beam Port (LBP), allowing the converter to be placed far away from the high-radiation area in the ESS shielding bunker, where the source stays accessible for trouble-shooting while facilitating a low-background environment for nearby UCN experiments. Various configurations of the beam and converter are possible, including a large-volume converter – with or without a magnetic reflector – for a large total UCN production rate, or a beam focused onto a small converter for highest possible UCN density. The source performances estimated by first simulations of a baseline version presented in this paper, including a saturated UCN density on the order of 10 5 cm − 3 , motivate further study and the development of NMO beyond the first prototypes that have been recently investigated experimentally.

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Section: Advanced Neutron Delivery Systems For In-beam Ucn Sourcesmentioning

confidence: 99%

Section: Advanced Neutron Delivery Systems For In-beam Ucn Sourcesmentioning

confidence: 99%

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In-beam superfluid-helium ultracold neutron source for the ESS

Zimmer

Bigault

Degenkolb

et al. 2023

JNR

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“…An alternative approach would be to keep the convertor vessel relatively short, while illuminating it with a very intense -albeit diverging -beam. Such a scenario could potentially be implemented with "nested mirror optics" [24,62] at the ESS LBP, and if the required neutron optics can be realized it may in some instances actually surpass the total UCN number for a long multicell stack with a guided or collimated beam (see Table 1 above, and Section 7 below). While in this approach the exiting beam would still contain a significant fraction of usable 8.9 Å neutrons, the overall UCN production rate density could be more favorable.…”

Section: Delivering Cold Neutrons Into An Extended Superfluid 4 He Co...mentioning

confidence: 99%

“…4). The beam divergence angles θ are respectively chosen to match ANNI [46] for (a) and (c), and a nested multimirror extraction [24,62] with m = 5 at the ESS LBP for (b) and (d). The build-up time and duration of a spin-precession cycle are chosen according to the optimization of equation ( 12), i.e., assuming that the same time-constant τ describes both build-up of the initial UCN density and the mean lifetime for UCN storage in each cell.…”

Section: The Neutron Permanent Electric Dipole Moment (Edm)mentioning

confidence: 99%

Approaches to high-density storage experiments with in-situ production and detection of ultracold neutrons

Degenkolb

Fierlinger

Zimmer

2023

JNR

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Low counting statistics is one of the most important challenges in modern experiments with ultracold neutrons (UCN). UCN densities in superthermal sources based on superfluid helium are normally much higher than those after UCN delivery to ex-situ volumes. Therefore, and due to the vanishing neutron absorption of 4He, storage-based experiments performed in-situ promise significant sensitivity gains. Scalable measurements offer a promising path to simultaneously address the inefficient use of cold neutron beams as precursors for UCN production in 4He, by recuperating the unused beam fraction, and confront the practical challenges of large-scale UCN infrastructure. We suggest strategies for the development of modular cryogenic cells, propose a novel approach for in-situ UCN detection, and discuss the ultimate statistical reach of such a multiplexed experiment for measuring the neutron’s permanent electric dipole moment (EDM). While dedicated research and development are needed to evaluate the feasibility for many requirements, a neutron EDM measurement with sensitivity well beyond 10 − 28 e cm seems possible. Such an experiment could be pursued at any compatible cold neutron beamline, e.g., at the Institut Laue–Langevin, or later using the ANNI facility or large beam port (LBP) at the European Spallation Source.

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