A new operating mode in experiments searching for free neutron-antineutron oscillations based on coherent neutron and antineutron mirror reflections

An observation of neutron-antineutron oscillations (n - n¯), which violate both B and B - L by 2 units, would constitute a fundamental discovery and contribute to our understanding of the baryon asymmetry of the universe. A sufficiently stringent upper constraint on this process would also make a major contribution by ruling out the possibility of post-sphaleron baryogenesis (PSB) involving first-generation quarks, which would mean that sphaleron transitions at the electroweak scale are essential for baryogenesis within the Sakharov paradigm. We show that one can design an experiment with free n using existing or projected neutron sources that can reach the sensitivity needed to rule out PSB if one allows the n and n¯, with sufficiently small tangential velocity, to coherently reflect from n/n¯ mirrors composed of certain nuclei. We show that the sensitivity of a future experiment can be greatly improved, and a more compact and less expensive apparatus can be realized. A sensitivity gain of ~ 104 in the oscillation probability relative to the existing free-n limit can be reached if one is willing to adopt a long flight path with a horizontal guide viewing a cold neutron source, or a significantly shorter flight path with a vertical guide viewing a very cold neutron source.

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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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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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