Abstract
On 23rd August 2018, the China Spallation Neutron Source (CSNS) located in Dongguan operated 4 neutron instruments. In the future, twenty neutron spectrometers will be built to provide ...multidisciplinary platforms for scientific research by national institutions, universities, and industries. Engineering Material Diffractometer (EMD), which will be used for strain measurements in engineering materials and components, will be constructed at the Beamline 8 in 2022. A novel thermal neutron detector, which will comply with the requirements of EMD application, is being developed. This detector will consist of
6
LiF/ZnS(Ag) scintillation screens, wavelength shifting fiber (WLSF) arrays, a silicon photomultiplier (SiPM) and Application Specific Integrated Circuit (ASIC) read-out electronics. Each scintillation screen will be inclined with respect to the incident neutron beam at a grazing angle θ = 17°. Such geometry will not only improve the spatial resolution of detectors but also the neutron detection efficiency. The prototype of detector module has been tested at the neutron Beamline 20 at the CSNS. The experimental results obtained for this prototype illustrate that the pixel size of detector module is 3 mm and the detection efficiency exceeds 40% at the neutron wavelength of 1 Å. Based on these results, we design and manufacture the final version of the detector for the EMD application, which is characterized by low power consumption, highly integrated and easy to install. 70 such detectors will be installed till the end of 2021.
The Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC) is a landmark large user-facility producing neutron and muon beams. Those beams ...feed over 20 beamlines hosting world-class instruments for the investigation of matter across the disciplines of materials science, solid state physics and chemistry, biological and life sciences, geology, engineering, and their wider applications. Neutron and muons can probe matter in very peculiar ways. They are sensitive to magnetism and hydrogen atoms, can penetrate materials deeply or probe surfaces, and allow one to investigate the fundamental dynamics of the materials. In the past three to four decades, neutron scattering has largely contributed to the development of modern technology, such as computers, mobile phone technology, electo-chemistry, the transportation industry, and the pharmaceutic industry. MLF is a world leader in such characterization technology and serves yearly to about 700 research experiments conducted from users of 34 countries around the world. The present book describes technical details of the proton accelerator, the neutron spallation source, the muon facility, and all the beamlines with engineering realization, specifications, and relevant examples.
MARIA (magnetism reflectometer with high incident angle) is a world class vertical sample reflectometer dedicated to the investigation of thin films in the fields of magnetism, soft matter and ...biology. The elliptical vertically focusing guide allows one to measure small samples with a typical size of 1 × 1 cm very efficiently. The double‐bounce polarizer and the in situ pumped 3He SEOP (spin‐exchange optical pumping) neutron spin filter cell for analysing the polarization of the reflected neutron beam can be moved into the beam in seconds. The polarized flux of MARIA amounts to 5 × 107 n (s cm2)−1 at the sample position with a horizontally collimated beam of 3 mrad, a wavelength of λ = 4.5 Å and a wavelength resolution of Δλ/λ = 10%. In the non‐polarized mode a flux of 1.2 × 108 n (s cm2)−1 is achieved in this configuration. MARIA is also capable of grazing‐incidence small‐angle neutron scattering measurements, using a pinhole collimation with two four‐segment slits and an absorber that prevents the focusing of the elliptical guide in the vertical direction.
MARIA is a world class vertical sample reflectometer dedicated to the investigation of thin films in the fields of magnetism, soft matter and biology. With the elliptical vertically focusing guide and a wavelength resolution of Δλ/λ = 10%, the non‐polarized flux at the sample position amounts to 1.2 × 108 n (s cm2)−1. Besides the polarized and non‐polarized reflectivity mode for specular and off‐specular reflectivity measurements, MARIA can also be used to carry out grazing‐incidence small‐angle neutron scattering investigations.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
PSR J0740+6620 has a gravitational mass of 2.08 ± 0.07
M
⊙
, which is the highest reliably determined mass of any neutron star. As a result, a measurement of its radius will provide unique ...insight into the properties of neutron star core matter at high densities. Here we report a radius measurement based on fits of rotating hot spot patterns to Neutron Star Interior Composition Explorer (NICER) and X-ray Multi-Mirror (XMM-Newton) X-ray observations. We find that the equatorial circumferential radius of PSR J0740+6620 is
13.7
−
1.5
+
2.6
km (68%). We apply our measurement, combined with the previous NICER mass and radius measurement of PSR J0030+0451, the masses of two other ∼2
M
⊙
pulsars, and the tidal deformability constraints from two gravitational wave events, to three different frameworks for equation-of-state modeling, and find consistent results at ∼1.5–5 times nuclear saturation density. For a given framework, when all measurements are included, the radius of a 1.4
M
⊙
neutron star is known to ±4% (68% credibility) and the radius of a 2.08
M
⊙
neutron star is known to ±5%. The full radius range that spans the ±1
σ
credible intervals of all the radius estimates in the three frameworks is 12.45 ± 0.65 km for a 1.4
M
⊙
neutron star and 12.35 ± 0.75 km for a 2.08
M
⊙
neutron star.
A multi‐slit very small angle neutron scattering (MS‐VSANS) instrument has been finally accepted at the China Spallation Neutron Source (CSNS). It is the first spallation neutron source based VSANS ...instrument. MS‐VSANS has a good signal‐to‐noise ratio and can cover a wide scattering vector magnitude range from 0.00028 to 1.4 Å−1. In its primary flight path, a combined curved multichannel beam bender and sections of rotary exchange drums are installed to minimize the background downstream of the instrument. An exchangeable multi‐slit beam focusing system is integrated into the primary flight path, enabling access to a minimum scattering vector magnitude of 0.00028 Å−1. MS‐VSANS has three modes, namely conventional SANS, polarizing SANS and VSANS modes. In the SANS mode, three motorized high‐efficiency 3He tube detectors inside the detector tank cover scattering angles from 0.12 to 35° simultaneously. In the polarizing SANS mode, a double‐V cavity provides highly polarized neutrons and a high‐efficiency 3He polarization analyser allows full polarization analysis. In the VSANS mode, an innovative high‐resolution gas electron multiplier detector covers scattering angles from 0.016 to 0.447°. The absolute scattering intensities of a selection of standard samples are obtained using the direct‐beam technique; the effectiveness of this method is verified by testing the standard samples and comparing the results with those from a benchmark instrument. The MS‐VSANS instrument is designed to be flexible and versatile and all the design goals have been achieved.
The first spallation neutron source based very small angle neutron scattering instrument has been constructed and accepted at the China Spallation Neutron Source. The instrument finds applications in multidisciplinary fields of soft matter, condensed matter physics, materials science and others.
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The Korea Research Institute of Standards and Science (KRISS) has developed and maintained neutron calibration facilities and neutron measurement systems, providing national standards on neutron dose ...equivalent, neutron fluence, and neutron emission rate for Korea. Neutron calibration facilities at KRISS include neutron irradiation facilities and neutron sources, such as radioactive isotope neutron sources, thermal neutrons, and mono-energetic neutrons. Neutron measurement systems at KRISS include the Bonner sphere spectrometer and a manganese-sulfate bath measurement system. The neutron standard facilities and measurement systems at KRISS have supported the researchers. Here, we introduce the ongoing research and development of neutron measurement systems, such as the mono-energetic neutron field generation system, which is currently under development and will be operational within a few months.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
With the construction of the ESS, the European neutron user community is eagerly awaiting the commissioning of the brightest neutron source worldwide in 2021. Parallel to this, there is however the ...ongoing development of neutron science being undertaken at a dwindling number of neutron facilities worldwide. The Jülich Centre for Neutron Science has started a project to develop and design compact accelerator-driven high brilliance neutron sources as an efficient and cost effective alternative to the current low- and medium-flux reactor and spallation sources with the potential to offer science and industry access to neutrons. The project aims to deliver a high brilliance neutron source (HBS), consisting of a compact neutron production and moderator system which provides thermal and cold neutrons with high brilliance efficiently extracted in an optimized neutron transport system. By shaping the experiment holistically from the source to the detector, neutron experiments could be set-up for specific scientific requirements in a flexible and efficient way for the neutron user.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Laue 3D neutron diffraction tomography (Laue 3DNDT) is a novel tomographic approach that enables non‐destructive resolution of the 3D microstructure of polycrystalline materials, utilizing a ...high‐intensity white beam of neutrons, resulting in high experimental efficiency. This article describes the functionality of the fast‐acquisition Laue camera for neutrons (FALCON), a double‐detector system setup used for Laue 3DNDT experiments at the pulse‐overlap diffractometer (POLDI) at the SINQ neutron source of the Paul Scherrer Institute. The reported commissioning includes standard experimental protocols, strategies for acquiring data and a detailed characterization of the measurement system. Finally, single‐crystal measurements for calibration and a full grain map of a CoNiGa oligocrystalline sample, extracted from a pilot study, are presented. A detailed understanding of the performance of the FALCON instrumentation is vital for the future advancement of the Laue 3DNDT algorithm, including, but not limited to, improved morphology reconstructions and strain mapping.
This article introduces the commissioning of the FALCON double‐detector system used for Laue 3D neutron diffraction tomography experiments at the POLDI instrument of SINQ, Paul Scherrer Institute.
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Neutron polarization analysis (NPA) for small‐angle neutron scattering (SANS) experiments using a pulsed neutron source was successfully achieved by applying a 3He spin filter as a spin analyzer for ...the neutrons scattered from the sample. The cell of the 3He spin filter gives a weak small‐angle scattering intensity (background) and covers a sufficient solid angle for performing SANS experiments. The relaxation time of the 3He polarization is sufficient for continuous use for approximately 2 days, thus reaching the typical duration required for a complete set of SANS experiments. Although accurate evaluation of the incoherent neutron scattering, which is predominantly attributable to the extremely large incoherent scattering cross section of hydrogen atoms in samples, is difficult using calculations based on the sample elemental composition, the developed NPA approach with consideration of the influence of multiple neutron scattering enabled reliable decomposition of the SANS intensity distribution into the coherent and incoherent scattering components. To date, NPA has not been well established as a standard technique for SANS experiments at pulsed neutron sources such as the Japan Proton Accelerator Research Complex (J‐PARC) and the US Spallation Neutron Source. It is anticipated that this work will contribute significantly to the accurate determination of the coherent neutron scattering component for scatterers in various types of organic sample systems in SANS experiments at J‐PARC, particularly for systems involving competition between the coherent and incoherent scattering intensity.
Neutron polarization analysis using a 3He spin filter for mainly soft matter systems is demonstrated for small‐angle neutron scattering with a pulsed neutron source; successful separation of the coherent scattering component from the incoherent scattering component due to hydrogen atoms was achieved.
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Neutron generators (NG) are being increasingly used in various industrial and research areas such as neutron activation analysis, neutron radiography, and neutron capture therapy. In such ...applications of neutron generators, compactness is one of the most important issues. Since a neutron source is generated by deuterium-deuterium (D-D) or deuterium-tritium (D-T) fusion reaction, a relatively thick shield for both fast neutrons and related photons is usually required. In this study, optimization of shielding designs for D-D and D-T neutron generators were investigated by adopting appropriate moderator and shielding materials. Based on the optimized moderator and shield thicknesses, the final dimensions of neutron generators were derived for various source strengths of D-D and D-T neutron conditions. Considering conventional condition of a container, we concluded that a 1010 n/sec D-D source and a 108 n/sec D-T source could be a portable NG.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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