Optimization of moderators and beam extraction at the ESS

A global approach coupling the moderator to the beam extraction system has been applied for the design optimization of the thermal and cold moderators of the European Spallation Source (ESS), which will be the brightest neutron source in the world for condensed-matter studies. The design is based on the recently developed high-brightness low-dimensional moderator concepts.Para-hydrogen is used for the cold neutron source, while thermal neutrons are provided by moderation in water. The overall moderation configuration was chosen in order to satisfy a range of requirements on bispectral extraction, beamport configuration and instrument performance. All instruments are served by a single moderator assembly above the target, arranged in a `butterfly' geometry with a height of 3 cm. This was determined to be the optimal height for trade-off between high brightness and efficient guide illumination, by analysis of the performance of 23 instruments, based on the reference suite of the ESS Technical Design Report. The concept of `brilliance transfer' is introduced to quantify the performance of the neutron optical system from the source to the sample. The target monolith incorporates a grid of 42 neutron beamports with an average separation of 6°, allowing a free choice between cold and thermal neutron sources at all instrument positions. With the large number of beamports and the space below the target available for future moderators, ample opportunities are available for future upgrades.

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Proof-of-principle experiment for laser-driven cold neutron source

Scientific Reports ◽

10.1038/s41598-020-77086-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

S. R. Mirfayzi ◽

A. Yogo ◽

Z. Lan ◽

T. Ishimoto ◽

A. Iwamoto ◽

...

Keyword(s):

Neutron Source ◽

Cold Neutron ◽

High Repetition Rate ◽

Pure Hydrogen ◽

High Brightness ◽

Monte Carlo Techniques ◽

Exit Surface ◽

Wide Range ◽

Cold Neutron Source ◽

Technical Advances

AbstractThe scientific and technical advances continue to support novel discoveries by allowing scientists to acquire new insights into the structure and properties of matter using new tools and sources. Notably, neutrons are among the most valuable sources in providing such a capability. At the Institute of Laser Engineering, Osaka, the first steps are taken towards the development of a table-top laser-driven neutron source, capable of producing a wide range of energies with high brightness and temporal resolution. By employing a pure hydrogen moderator, maintained at cryogenic temperature, a cold neutron ($$\le 25\hbox { meV}$$ ≤ 25 meV ) flux of $$\sim 2\times 10^3\hbox { n/cm}^2$$ ∼ 2 × 10 3 n/cm 2 /pulse was measured at the proximity of the moderator exit surface. The beam duration of hundreds of ns to tens of $$\upmu \hbox {s}$$ μ s is evaluated for neutron energies ranging from 100s keV down to meV via Monte-Carlo techniques. Presently, with the upcoming J-EPoCH high repetition rate laser at Osaka University, a cold neutron flux in orders of $$\sim 1\times 10^{9}\hbox { n/cm}^2/\hbox {s}$$ ∼ 1 × 10 9 n/cm 2 / s is expected to be delivered at the moderator in a compact beamline.

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Confirmation of Nuclear Heating Rate for Installation of Cold Neutron Source at HANARO

EPJ Web of Conferences ◽

10.1051/epjconf/202022504004 ◽

2020 ◽

Vol 225 ◽

pp. 04004

Author(s):

Kim Myong-Seop ◽

Park Byung-Gun

Keyword(s):

Heating Rate ◽

Neutron Source ◽

Cold Neutron ◽

Reactor Core ◽

Reactor Power ◽

Electric Heater ◽

Lead Wire ◽

Heating Rates ◽

Cold Neutron Source ◽

Nuclear Heating

In order to determine the capacity of the cold neutron source refrigerator of HANARO, the nuclear heating rate at CN vertical hole is measured by using the heat-flow calorimetric method and confirmed by the calculation. The heating rate measurement device of HANARO was composed of a calorimeter sensor, an air containing aluminum sleeve for fitting the sensor to the CN hole, aluminum weight and a lead wire assembly. The calorimeter sensor consists of a cylindrical Al sample and container, two thermocouples and the electric heater for the calibration of the calorimeter. The sample is separated by an air gap from the Al container surrounded by an air containing Al sleeve. After installation of the calorimeter at a measurement position of HANARO, the heat transfer inside the calorimeter was simulated by the electric heating for the sample. The nuclear heating rates at the CN hole were determined at three reactor powers of 1, 4 and 8 MW by using the calibration curve and the temperature measurements at each reactor power. The measured nuclear heating rate per unit mass of Al sample at 8 MW reactor power is 0.143 W/g and it is equivalent to the 0.494 W/g at 30 MW. The nuclear heating rate was calculated by using the MCNP code. The calculation model for the whole facility including the reactor core and the reflector tank were established. In the calculation procedure, the heat generations by various radiations were evaluated with considering the prompt, delayed and activation effects. The measured heating rate was reasonably well supported by the calculation using the cold neutron facility design code. It will be very useful for the moderator cell of cold neutron source of HANARO.

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Physics study of liquid hydrogen moderator of CMRR reactor cold neutron source

Progress in Nuclear Energy ◽

10.1016/j.pnucene.2018.09.002 ◽

2019 ◽

Vol 110 ◽

pp. 121-128

Author(s):

Longwei Mei ◽

Cong Liu ◽

Songlin Wang ◽

Fei Shen

Keyword(s):

Neutron Source ◽

Cold Neutron ◽

Liquid Hydrogen ◽

Cold Neutron Source

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CFD Simulations of the Cold Neutron Source at the OPAL Reactor

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4049054 ◽

2020 ◽

Author(s):

James L Spedding ◽

Mark Ho ◽

Weijian Lu

Keyword(s):

Neutron Source ◽

Cold Neutron ◽

Operating Conditions ◽

Convergence Time ◽

Cfd Model ◽

Cfd Simulations ◽

Cold Neutron Source ◽

Order Of Magnitude ◽

Computational Fluid Dynamics Cfd ◽

Polyhedral Mesh

Abstract The Open Pool Australian Light-water (OPAL) reactor Cold Neutron Source (CNS) is a 20 L liquid deuterium thermosiphon system which has performed consistently but will require replacement in the future. The CNS deuterium exploits neutronic heating to passively drive the thermosiphon loop and is cryogenically cooled by forced convective helium flow via a heat exchanger. In this study, a detailed computational fluid dynamics (CFD) model of the complete thermosiphon system was developed for simulation. Unlike previous studies, the simulation employed a novel polyhedral mesh technique. Results demonstrated that the polyhedral technique reduced simulation computational requirements and convergence time by an order of magnitude while predicting thermosiphon performance to within 1% accuracy when compared with prototype experiments. The simulation model was extrapolated to OPAL operating conditions and confirmed the versatility of the CFD model as an engineering design and preventative maintenance tool. Finally, simulations were performed on a proposed second-generation CNS design that increases the CNS moderator deuterium volume by 5 L, and results confirmed that the geometry maintains the thermosiphon deuterium in the liquid state and satisfies the CNS design criteria.

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Low-dimensional moderators at ESS and compact neutron sources

EPJ Web of Conferences ◽

10.1051/epjconf/202023104006 ◽

2020 ◽

Vol 231 ◽

pp. 04006

Author(s):

Luca Zanini ◽

Esben Klinkby ◽

Ferenc Mezei ◽

Alan Takibayev

Keyword(s):

Power Sources ◽

High Brightness ◽

Neutron Sources ◽

Compact Source ◽

Spallation Source ◽

Lower Heat ◽

Low Dimensional ◽

Design Options ◽

Compact Sources ◽

Heat Loads

Low-dimensional moderators were designed for the European Spallation Source (ESS), and the same concepts can be applied to compact sources. At ESS, quasi two-dimensional (2D) high-brightness moderators will serve all the instruments of the initial suite. The design of the moderators is influenced by several factors, such as the layout of the facility, the requirements for beam extraction, and the number of instruments; these constraints led to the choice of the 2D “butterfly” moderator for ESS. In an accelerator-based compact source, such moderators can be designed in an even more efficient way than for high-power sources, taking advantage of the lower heat loads and of the more compact arrangement of the target-moderator system, which gives more freedom in the optimization of the geometrical setup. Some promising design options have been explored.

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