The source for ultra-cold neutrons at the FRM II

Frei, A.

doi:10.3233/jnr-220008

Cited by 3 publications

(3 citation statements)

References 60 publications

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“…Additionally, this solution would have to cope with the challenge of cooling the material to the needed temperature in a region with a high radiation field and high heat loads. While for SD 2 a temperature of 5 K seems optimal [65], the THF-d clathrate hydrate would best be operated below 2 K. At such low temperatures, the local modes are predominantly populated in the ground state, which suppresses up-scattering. From a practical point of view, He-II can be used for effective cooling of the weakly thermal-conducting clathrate hydrate.…”

Section: Dedicated Vcn Moderatormentioning

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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Section: Dedicated Vcn Moderatormentioning

confidence: 99%

HighNESS conceptual design report: Volume I

Santoro,

Abou El Kheir,

Acharya

et al. 2024

JNR

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“…Solid D 2 , prepared in the molecular rotational ground state and kept at temperatures below 10 K, is most effectively used "in-pile", that is, near an intense primary neutron source, where it produces a high rate of UCNs (see Refs. [12,24,26,[28][29][30]32,34,51,53,55] for operating, demonstrated and proposed SD 2 sources). If the UCN source consists of only a small quantity of SD 2 , thus acting purely as a neutron converter, the incident neutrons need to be pre-moderated by an external CN source, typically of LD 2 .…”

Section: Basic Concepts and Possible Locations Of Ucn Sourcesmentioning

confidence: 99%

“…Monte Carlo simulations for a source placed at various distances from the spallation target will be carried out, to determine not only the neutronic performance, but also the heat load on the moderator and hence the cooling requirements. While for SD 2 a temperature of 5 K seems optimal [12], the THF-d clathrate hydrate would best be operated below 2 K. At such low temperatures, the local modes are predominantly populated in the ground state, which suppresses up-scattering. From a practical point of view, He-II can be used for effective cooling of the weakly thermal-conducting clathrate hydrate.…”

Section: Dedicated Vcn Sourcementioning

confidence: 99%

Very cold and ultra cold neutron sources for ESS

Zanini

Dian

DiJulio

et al. 2023

JNR

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The goal of the “Workshop on Very Cold and Ultra Cold Neutron Sources for ESS” was to discuss scientific cases, ideas and possibilities for the implementation of sources of Very Cold and Ultra Cold neutrons at the European Spallation Source. The ESS facility, presently under construction, offers several possibilities for in-pile UCN or VCN sources, in primis thanks to the available space below the spallation target where additional neutron sources can be placed to complement those above the target. Neutron beams can be extracted over a wide angular range with a grid of forty-two beamports with 6° average angular separation, allowing future instruments to be installed which may view either the upper or lower moderator systems. Of greatest interest for fundamental physics is the so-called Large Beamport foreseen for the NNBAR experiment. This beamport is also particularly well suited to feed a UCN source, for which several ideas were presented that employ either superfluid helium or solid deuterium as established neutron converter materials. Concepts for VCN sources make use of novel materials for VCN production and/or advanced reflectors to increase yields in the coldest part of the neutron spectrum from a cryogenic neutron source. In this paper we discuss these ideas and the possible locations of UCN and VCN sources at ESS.

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Time-of-flight spectroscopy of ultracold neutrons at the PSI UCN source

Bison,

Chen,

Chiu

et al. 2023

Eur. Phys. J. A

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The ultracold neutron (UCN) source at the Paul Scherrer Institute (PSI) provides high intensities of storable neutrons for fundamental physics experiments. The neutron velocity spectrum parallel to the beamline axis was determined by time-of-flight spectroscopy using a neutron chopper. In particular, the temporal evolution of the spectrum during neutron production and UCN storage in the source storage volume was investigated and compared to Monte Carlo simulation results. A softening of the measured spectrum from a mean velocity of 7.7(1)–5.1(1) $$\hbox {m s}^{-1}$$ m s - 1 occurred within the first 30 $$\hbox {s}$$ s after the proton beam pulse had impinged on the spallation target. A spectral hardening was observed over longer time scales of one measurement day, consistent with the effect of surface degradation of the solid deuterium moderator.

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The source for ultra-cold neutrons at the FRM II

Cited by 3 publications

References 60 publications

HighNESS conceptual design report: Volume I

HighNESS conceptual design report: Volume I

Very cold and ultra cold neutron sources for ESS

Time-of-flight spectroscopy of ultracold neutrons at the PSI UCN source

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