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52
result(s) for
"Ultracold neutrons."
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Light-powered end-to-end neutron detection and imaging with an edge-deployed optical AI chip
Neutron detection is widely used in many applications including nuclear physics, nuclear energy, nuclear technologies and nuclear safeguards. Developing an end-to-end neutron detection and imaging workflow paves way towards fully automated processes for many applications. We implemented an automated workflow for neutron detection experiments which use a solid state image sensor to capture neutron hits as a digital image. We deploy the workflow to an edge-based optical neural network (ONN) to increase the radiation-hardness and lifetime of neutron detection instruments. We present a two-stage neural network framework for detection of neutrons at sub-pixel resolution. The first stage uses a region proposal network to efficiently detect and extract neutron hits from the input camera image. The second stage feeds the extracted hits into a fully connected neural network to predict the sub-pixel hit position. The performance of the two-stage framework is evaluated using the edge-based ONN. The results show that we can achieve above 96% neutron detection accuracy as well as sub-pixel and sub-micron position resolution, while enjoying the advantages of the ONN hardware including radiation-hardness, low energy consumption and high computing speed for integrated edge camera and hardware deployment, when compared with electronic counterparts.
Journal Article
Improved Search for Neutron to Mirror-Neutron Oscillations in the Presence of Mirror Magnetic Fields with a Dedicated Apparatus at the PSI UCN Source
While the international nEDM collaboration at the Paul Scherrer Institut (PSI) took data in 2017 that covered a considerable fraction of the parameter space of claimed potential signals of hypothetical neutron (n) to mirror-neutron (n′) transitions, it could not test all claimed signal regions at various mirror magnetic fields. Therefore, a new study of n−n′ oscillations using stored ultracold neutrons (UCNs) is underway at PSI, considerably expanding the reach in parameter space of mirror magnetic fields (B′) and oscillation time constants (τnn′). The new apparatus is designed to test for the anomalous loss of stored ultracold neutrons as a function of an applied magnetic field. The experiment is distinguished from its predecessors by its very large storage vessel (1.47 m3), enhancing its statistical sensitivity. In a test experiment in 2020 we have demonstrated the capabilities of our apparatus. However, the full analysis of our recent data is still pending. Based on already demonstrated performance, we will reach sensitivity to oscillation times τnn′/cos(β) well above a hundred seconds, with β being the angle between B′ and the applied magnetic field B. The scan of B will allow the finding or the comprehensive exclusion of potential signals reported in the analysis of previous experiments and suggested to be consistent with neutron to mirror-neutron oscillations.
Journal Article
Rotating Magnetic Gravitational Trap for Storing Ultracold Neutrons
The paper proposes an experiment to measure the neutron lifetime by storing ultracold neutrons in a rotating magnetic trap. The magnetic trap is a set of NdFeB permanent magnets. By rotating the trap around a horizontal axis, it is possible to carry out the gravitational capture of ultracold neutrons and their holding. A design option is presented when two traps are located in one installation on the same axis: material and magnetic. The sensitivity of the magnetic trap is assessed in comparison with the material one under equal measurement conditions. One of the factors influencing the systematic error of the experiment will be the process of neutron depolarization in a magnetic field. Therefore, the paper considers the issue of developing a magnetic system that minimizes the probability of neutron depolarization. The so-called turbine effect is also considered, which can manifest itself in a change in the energy of ultracold neutrons during rotation due to interaction with the flat faces of the trap. The proposed gravitational capture of ultracold neutrons in a magnetic trap is a fundamentally new approach that has never been implemented before. The experiment can be carried out on the ultracold neutron source under construction at the PIK reactor.
Journal Article
Concept of UCN Source at WWR-K Reactor (AlSUN)
We present the concept of an ultracold neutron (UCN) source with a superfluid He-4 (SF 4He) converter located in the thermal column of the WWR-K research reactor at the Institute of Nuclear Physics (INP) in Almaty, Kazakhstan. The conceptual design is based on the proposal of accumulating UCNs in the source and effectively transporting them to experimental setups. We propose to improve the UCN density in the source by separating the heat and UCN transport from the production volume and decreasing the temperature of the SF 4He converter to below about 1 K. To obtain operation temperatures below 1 K, we plan to use a He-3 pumping cryogenic system and minimize the thermal load on the UCN accumulation trap walls. Additional gain in the total number of accumulated UCNs can be achieved through the use of a material with a high critical velocity for the walls of the accumulation trap. The implementation of such a design critically depends on the availability of materials with specific UCN and cryogenic properties. This paper describes the conceptual design of the source, discusses its implementation methods and material requirements, and plans for material testing studies.
Journal Article
Ultracold neutron storage simulation using the Kassiopeia software package
The Kassiopeia software package was originally developed to simulate electromagnetic fields and charged particle trajectories for neutrino mass measurement experiments. Recent additions to Kassiopeia also allow it to simulate neutral particle trajectories in magnetic fields based on their magnetic moments. Two different methods were implemented: an exact method that can work for arbitrary fields and an adiabatic method that is limited to slowly-varying fields but is much faster for large precession frequencies. Additional interactions to simulate reflection of ultracold neutrons (UCNs) from material walls and to allow spin–flip pulses were also added. These tools were used to simulate neutron precession in a room temperature neutron electric dipole moment experiment and predict the values of the longitudinal and transverse relaxation times as well as the trapping lifetime. All three parameters are found to closely match the experimentally determined values when simulated with both the exact and adiabatic methods, confirming that Kassiopeia is able to accurately simulate neutral particles. This opens the door for future uses of Kassiopeia to prototype the next generation of atomic traps and UCN experiments.
Journal Article
Superfluid Helium Nased Ultracold Neutron Source for the PIK Reactor
The PIK reactor at NRC “Kurchatov Institute”—PNPI is going to be equipped with a high-flux Ultra Cold Neutron (UCN) source for fundamental physics researches. The UCN source will use superfluid helium, which will make possible to achieve the density of UCN 2.2 × 10
3
cm
–3
, that has not yet been achieved anywhere in the world. The UCN source will be installed on the GEK-4 channel, which will make possible to obtain a low value of heat influx to cryogenic vessels from reactor radiation. The heat removal from the UCN source vessel will be implemented by using a heat exchanger. The calculated UCN density in the EDM spectrometer chamber at the PIK is going to be 200 cm
–3
, which is 20 times higher than the existing UCN densities in the world. For a new UCN source based on superfluid helium, an extensive research program has been developed in field of the physics of fundamental interactions, including the search for a nonzero neutron EDM, precision measurement of the neutron lifetime, and search for mirror dark matter.
Journal Article
Simulation of the Ultracold Neutron Source at the Reactor PIK
The paper presents the simulation of a complex of reserch with ultracold neutrons at the reactor PIK (Gatchina, Russia). The complex is being built on the basis of a high-intensity source of ultracold neutrons at the channel GEK-4. A Monte Carlo model has been developed, which includes a source, a neutron guide system and an experimental setup for search for the electric dipole moment of a neutron, taking into account their real location in the main hall of the reactor. Using the developed computer model the density of ultracold neutrons in the setup was obtained, which is 200 cm
–3
. It is 50 times higher than at the source at the Institut Laue-Langevin (Grenoble, France). This density will allow to achieve a sensitivity of measurements in the experiment of 1 × 10
–27
electrons cm/year.
Journal Article
Ultracold-Neutron Source Based on Superfluid Helium for the PIK Reactor
A high-density ultracold-neutron source based on superfluid helium is being developed at the Petersburg Nuclear Physics Institute (PNPI) of the National Research Center “Kurchatov Institute” for fundamental physics research. This ultracold-neutron source is intended for installation in the largest experimental channel of the PIK reactor complex: the horizontal experimental channel (HEC-4). Calculations indicate that the thermal-neutron flux density at the channel output is 3 × 10
10
cm
–2
s
–1
. The new ultracold-neutron source aims to achieve an ultracold neutron density of 3.5 × 10
3
cm
–3
at the reactor-chamber output and 200 cm
–3
in the spectrometer designated for measuring the neutron electric dipole moment. The neutron-guide system for ultracold neutrons is designed to support five experimental facilities alternately. Initially, the ultracold-neutron source will be equipped with existing experimental setups: a neutron electric-dipole-moment spectrometer and two setups for measuring the neutron lifetime (utilizing gravitational and magnetic traps). For this ultracold-neutron source, a unique technological cryogenic complex has been designed and implemented to work with superfluid helium under reactor-installation conditions. This complex includes equipment capable of achieving temperatures down to 1 K and removing heat from superfluid helium at a rate of up to 60 W.
Journal Article
Few-Neutron Systems with the Long-Range Casimir-Polder Force
In this work, we present results of the long-range electromagnetic Casimir-Polder interactions between two neutrons, a neutron and a conducting wall, and a neutron between two walls. As input, we use the dynamic dipole polarizabilities of the neutron fitted to chiral EFT results up to the pion production threshold and at the onset of the Delta resonance. Our work can be relevant to the physics of confined ultracold neutrons inside bottles.
Journal Article