High brilliant thermal and cold moderator for the HBS neutron source project Jülich

Cronert, Tobias; Dabruck, Jan Philipp; Doege, Paul; Bessler, Yannick; Klaus, M.; Hofmann, M.; Zakalek, Paul; Rücker, Ulrich; Lange, Carsten; Butzek, Michael; Hansen, W.; Nabbi, Rahim; Brückel, Thomas

doi:10.1088/1742-6596/746/1/012036

Cited by 14 publications

(10 citation statements)

References 3 publications

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“…The design of the cold moderator vessel follows the concept of low-dimensional cold moderators as proposed by Mezei et al [2] and was designed for pure para-H2. The MCNP-based parameter studies required for dimensioning the LH2 (liquid hydrogen) volume in the cold moderator vessel were done at the Chair of Nuclear Engineering and Technology Transfer (NET) at RWTH Aachen in cooperation with JCNS-2 [5,6], whereas the final engineering design was a contribution of ZEA-1 at Forschungszentrum Jülich [7]. The result is a quasi-onedimensional cylindrical moderator vessel that is fed with thermal neutrons from all sides.…”

Section: Cold Moderatormentioning

confidence: 99%

“…The smaller the illuminated area of the cold moderator, the higher the brilliance but the smaller the flux. However, a first approximation is a diameter d corresponding to lthermal and a length l corresponding to lcold, though for reasons of the achievable total neutron flux and manufacturing, the dimensions d = 2.5 cm and l = 10 cm have been chosen [6], resulting in a total liquid hydrogen volume of 200 ml. The operating temperature and absolute pressure are T = 17 to 20 K and p = 1.3 to 1.5 bar.…”

Section: Cold Moderatormentioning

confidence: 99%

“…Currently, the design of cold moderators using hydrogen is subject to uncertainties due to the ambiguity in the required nuclear data [4]. Furthermore, Monte Carlo simulations of moderators using ortho-para mixtures are especially hard to manage and prone to errors [5,6]. To overcome this problem and enable a reliable moderator design, there are endeavors by JCNS to measure the neutron spectra resulting from different ortho-para mixtures (and pure para-H2) experimentally.…”

Section: Introductionmentioning

confidence: 99%

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Cryostat for the provision of liquid hydrogen with a variable ortho-para ratio for a low-dimensional cold neutron moderator

et al. 2020

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A significant contribution to the enhancement of the neutron brilliance achievable with Compact Accelerator-driven Neutron Sources (CANS) can be made by an optimized cold moderator design. When using liquid para-H2 as the moderating medium, the concept of low-dimensional cold moderators can be employed to increase the neutron brightness (as currently foreseen at the European Spallation Source ESS). Para-H2 shows a drop in the scattering cross section by about one order of magnitude around 15 meV, resulting in a large deviation between the mean free paths of thermal and cold neutrons. Taking advantage of this effect, the cold moderator geometry can be optimized to allow the intake of thermal neutrons through a relatively large envelope surface and then extracting them in an efficient way towards the neutron guides. One drawback of this solution is the lack of thermalization of the cold neutrons. In the context of the HBS (High Brilliance Neutron Source) project, efforts are made to overcome this problem by increasing the scattering cross section of the H2 in a defined way. The idea is to admix small amounts of ortho-H2, which maintains its large scattering cross section in the region below 15 meV. Like this, the neutron spectrum can be shifted towards lower energies and adjusted for the needs of the respective instruments. In a cooperation between TU Dresden and FZ Jülich, an experimental setup has been created to prove the feasibility of this concept. The main component of the experimental setup is a LHe-cooled flow cryostat that enables the separate condensation of a para-H2 and a normal-H2 flow and a subsequent mixing of the two in precise proportions. The resulting LH2 mixture at 17 - 20 K is fed into a small cold moderator vessel (approx. 200 ml). In this work, the current status of the setup is presented. The construction and commissioning of the mixing cryostat have been completed and first test runs show that different ortho-para-H2 mixtures can be produced. In the near future, the system will be ready for measurements at a neutron source.

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Section: Cold Moderatormentioning

confidence: 99%

Section: Cold Moderatormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cryostat for the provision of liquid hydrogen with a variable ortho-para ratio for a low-dimensional cold neutron moderator

et al. 2020

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“…Given the fact that new reactor based sources are not presently being built or planned in the Western world, there are initiatives to evaluate and design accelerator based neutron sources with specific performance, e.g. "high brilliance" [9] customized for specific applications. Also in such cases, NI installations are or could be foreseen from the beginning.…”

Section: Figmentioning

confidence: 99%

What Future in Neutron Imaging?

Lehmann

2020

Neutron Radiography - WCNR-11

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“…A polyethylene (PE) moderator with a radius of 8 cm surrounding the beryllium target moderates the neutrons to thermal energies and a Pb reflector with a thickness of 20 cm increases the thermal neutron density inside the PE moderator. Low dimensional extraction channels [7,8] inside the moderator / reflector assembly direct the thermalized neutrons to the instruments. They have an inclination of ±15 • with respect to the proton beam.…”

Section: Acceleratormentioning

confidence: 99%

Workhorse Scattering Instruments for Low Power Compact Accelerator Driven Neutron Sources

Zakalek

Cronert

Doege

et al. 2018

Proceedings of the International Conference on Neutron Optics (NOP2017)

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We investigate the potential of neutron scattering instrumentation fed by a compact accelerator driven neutron source. Such a source can be built and operated easily at any large university. Reference designs of typical workhorse scattering instruments for small-angle neutron scattering, powder diffractometry and reflectometry are presented. The neutron flux at sample position and the instrument resolution have been calculated from the parameter design of a pulsed neutron source with 400 W average accelerator power. Instrument performances allow for reasonable scientific use even at this low power level.

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High brilliant thermal and cold moderator for the HBS neutron source project Jülich

Cited by 14 publications

References 3 publications

Cryostat for the provision of liquid hydrogen with a variable ortho-para ratio for a low-dimensional cold neutron moderator

Cryostat for the provision of liquid hydrogen with a variable ortho-para ratio for a low-dimensional cold neutron moderator

What Future in Neutron Imaging?

Workhorse Scattering Instruments for Low Power Compact Accelerator Driven Neutron Sources

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