Search

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.

A spin-contrast-variation neutron powder diffractometry technique that extracts the structure factor of hydrogen atoms, i.e. the contribution of hydrogen atoms to a crystal's structure factor, has been developed. Crystals of L-glutamic acid were dispersed in a D-polystyrene matrix containing 4-methacryloyloxy-2,2,6,6,-tetramethyl-1-piperidinyloxy to polarize their proton spins dynamically. The intensities of the diffraction peaks of the sample changed according to the proton polarization, and the structure factor of the hydrogen atoms was extracted from the proton-polarization-dependent intensities. This technique is expected to enable analyses of the structures of hydrogen-containing materials that are difficult to determine with conventional powder diffractometry.

To achieve high-performance proton-exchange membranes (PEMs), understanding of the polymer structure/property relationship is crucial. In particular, the structure of water clusters (number, size, ...

A 3He spin filter is a useful device for polarizing a neutron beam. We are developing the 3He spin filters for users of the material and life science facility of the Japan Proton Accelerator Research Complex (J‑PARC). An in situ SEOP system with a 3He polarization evaluation system using nuclear magnetic resonance (NMR) method of adiabatic fast passage and electron paramagnetic resonance (EPR) was developed. We conducted an experiment on the neutron beam line BL10 (NOBORU) of J-PARC to confirm the consistency of 3He polarization, estimated using the neutron transmission, NMR and EPR. The polarization of 3He, evaluated using the different methods, was consistent and the evaluation system operated normally for about 6 h.

Hard carbon is the most common anode material for Na-ion battery. The structure of the hard carbon and the dynamics of Na-ion in hard carbon were studied with small- and wide-angle neutron scattering and muon spin relaxation technique. The neutron scattering revealed the increase of interlayer distance between graphenes and decrease of the size of nanopores with increasing sodium intercalation in hard carbon. The muon spin relaxation revealed that a systematic increase in the field fluctuation rate with increasing temperature evidenced a thermally activated sodium diffusion. Assuming the two-dimensional diffusion of Na-ion in the graphene layers, the self-diffusion coefficient of Na-ion was estimated to be 2.6 × 10−11 cm2/s at 310 K, with a thermal activation energy of 39(7) meV.

In order to improve the reaction efficiency of fuel cells, the structure of carbon and ionomer affecting electronic and proton conduction and the distribution of voids affecting oxygen diffusion and drainage have been studied to find the guideline for the optimum structure of the catalyst layer. In this study we are developing a method to evaluate the dispersed structure of carbon and ionomer and the thickness of the ionomer layer by using the small and wide angle neutron scattering instrument, TAIKAN at the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). The dependence of ionomer-to-carbon weight ratio of small-angle neutron scattering (SANS) cross section of the solid carbon catalyst layer and the hollow carbon catalyst layer was evaluated comparatively. Furthermore, the relative humidity dependence of SANS cross section of the solid carbon catalyst layer and the hollow carbon catalyst layer was also evaluated by using the contrast variation method. This presentation is based on results obtained from a project, JPNP20003, subsidized by a New Energy and Industrial Technology Development Organization (NEDO).

We are developing a neutron polarizer with polarized $^3$He gas, referred to as a $^3$He spin filter, based on the Spin Exchange Optical Pumping (SEOP) for polarized neutron scattering experiments at Materials and Life Science Experimental Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC). A $^3$He gas-filling station was constructed at J-PARC, and several $^3$He cells with long spin relaxation times have been fabricated using the gas-filling station. A laboratory has been prepared in the MLF beam hall for polarizing $^3$He cells, and compact pumping systems with laser powers of 30~W and 110~W, which can be installed onto a neutron beamline, have been developed. A $^3$He polarization of 85% was achieved at a neutron beamline by using the pumping system with the 110~W laser. Recently, the first user experiment utilizing the $^3$He spin filter was conducted, and there have been several more since then. The development and utilization of $^3$He spin filters at MLF of J-PARC are reported., Comment: 9 pages, 15 figures

Residual strains in a punched electrical steel sheet increase the iron loss in the steel sheet. To accurately estimate the effect of residual strain on iron loss, the residual strain distribution in a punched electrical steel sheet should be evaluated. In this study, we demonstrated the two-dimensional imaging of the residual strain distribution in a punched electrical steel sheet using the neutron Bragg-edge transmission imaging method. To improve the accuracy of strain measurement with minimal deterioration of spatial resolution, we applied a process of superposing many specimen images. The tensile strain near the punched edge and the compressive strain inside the core were experimentally confirmed using this method. Finally, the neutron Bragg-edge imaging results and those obtained from kernel average misorientation map using electron backscattered diffraction were compared to verify the validity of the proposed method.

In this study, monodispersive nanoconfined water (“water pocket”) is organized spontaneously in hydrophilic ionic liquid (IL). The IL is 1-alkyl-3-methylimidazolium nitrate ([Cnmim][NO3] n = 2, 6, and 8). By small-angle neutron scattering (SANS), D2O aggregations in the IL are detected. There are no SANS peaks for [C2mim][NO3]–D2O, but, in [C6mim][NO3]–x mol% D2O, a SANS peak can be observed at 70

For flow visualization study of quantum turbulence in superfluid $$^4$$ He, He $$_2^*$$ excimers are unique tracers which follow only normal-fluid component flow above 1 K. To generate detectable small He $$_2^*$$ clouds (clusters) required for full-space velocity field measurements, we have adopted a new method based on neutron absorption reaction of $$^3$$ He impurities in $$^4$$ He and conducted proof-of-principle experiments. Generation of the He $$_2^*$$ excimers was detected by laser-induced fluorescence using photomultiplier tubes. The fluorescence was observed to increase proportionally to the neutron flux, suggesting that a sufficient amount of He $$_2^*$$ excimers were generated by neutrons. We also estimated the number of He $$_2^*$$ excimers possibly generated by $$\gamma $$ -rays and found that the relevant contribution was less than 40%. Thus, the majority of the He $$_2^*$$ excimers was confirmed to be generated via n- $$^3$$ He absorption reactions.

We are developing practical material observation methods using neutron imaging at J-PARC Materials and Life Science Experimental Facility (MLF). Neutron Bragg-edge transmission (BET) imaging, one of the energy-resolved neutron imaging methods, makes it possible to quantitatively visualize the two-dimensional distribution of physical properties within a sample. Here, we report two application examples. First, feasibility of measuring the temperature distribution of a copper rod through the thermal expansion of the lattice constant using BET spectral analysis was studied. Second, visualization of the texture variation and the strain distribution of a bent steel plate through the 2D-BET imaging method were performed. The obtained results for both experiments were compared with those obtained by the neutron diffraction (ND) method.

Neutron resonance absorption imaging, being used to visualize a spatial distribution of elements and/or temperature within a sample, is one of the important applications of an intense short-pulse neutron source. Two-dimensional time-analyzer neutron detectors are indispensable to perform neutron energy dependent imaging by means of the time-of-flight technique. Some state-of-the-art time-analyzer neutron detectors have been developed for thermal or cold neutrons. However the detection efficiencies of such neutron detectors are not sufficient for neutron resonance absorption imaging which utilizes neutrons in the energy region from eV to keV. The 2012 model lithium-6 time-analyzer neutron detector (LiTA12) system, based on a lithium glass scintillator and multi-anode photomultiplier tube, has the highest neutron efficiency among the detectors for pulsed neutron imaging together with the flexibility to tune the efficiency by changing the thickness of the lithium glass. The authors estimated performances of the detector at resonance neutron energies finding that 0.7 mm width line pairs made by 3 μm thick gold could be resolved at 4.9 eV and the maximum count rate of 8 Mcps was achieved at 1 keV.

The reliability of neutron resonance thermometry was discussed based on measurements of neutrons transmitted through tantalum (0.1 mm thick) and tungsten (1 mm thick) indicators at 26, 96, 189, and 285 degrees Celsius using the energy-resolved neutron imaging system, RADEN, at the Japan Proton Accelerator Complex (J-PARC). The intensity of transmitted neutrons at the sides of resonance dips were found to decrease with increasing temperature. Sensitivity coefficients to convert this decrease to temperature were derived, and two-dimensional distributions of the decreasing rates, being proportional to the temperature distribution, were obtained. The reliability of estimated temperature was calculated as a function of temporal and spatial resolution assuming that the dominant factor of the reliability was the uncertainty in the neutron counts. The authors set a target of neutron resonance thermometry for practical applications, and found a required efficiency of the neutron detector for resonance thermometry.

We have performed neutron radiography and tomography using a CCD camera-type detector for some test samples at RADEN. The current spatial resolution for neutron radiography is estimated to about 350 μm in the largest field-of-view of 300 × 300 mm2 and 100 μm in the field-of-view of 60 × 60 mm2. It is thought that the latter spatial resolution is strongly affected by the image blur in the scintillator screen. In the case of neutron tomography, the current spatial resolution is estimated to be better than 0.5 mm using an iron and aluminum test sample. Furthermore, we have performed neutron tomography for a cast aluminum product. As a result, small blowholes are found in the center of the product. This demonstrates the importance of non-destructive testing by neutron radiography and tomography for industrial products.

The influences of bending deformation and subsequent subzero treatment on the martensite transformation behaviors in a metastable austenitic alloy Fe−25 wt.% Ni−0.4 wt.% C were investigated by the time-of-flight (TOF) neutron Bragg-edge transmission (BET) imaging method. Two-dimensional (2D) maps of martensite phase volume fractions and texture variations due to residual stress and lowering the temperature of the bent samples before and after subzero treatment were obtained by Bragg-edge spectral analysis. The obtained phase volume fractions were quantitatively compared with those determined by neutron diffraction.

We have been developing a 3He neutron spin filter (NSF) using a spin exchange optical pumping (SEOP) technique. The 3He NSF provides a high-energy polarized neutron beam with large beam size. A high-energy polarized neutron beam, which is more difficult to produce with commonly used magnetic supermirror-based polarizers, is an effective probe for magnetic imaging techniques, particularly in the case of strong magnetic fields. Additionally, an in-situ SEOP system enables us to produce a polarized neutron beam with stable polarization, which is big advantage for experiments with long measurement times. In this study, we installed two in-situ SEOP systems as a neutron spin polarizer and analyzer providing a stable high-energy polarized neutron beam over several days.

Line broadening analysis was performed on the time-of-flight neutron diffraction data for the plastically bent plates of a ferritic steel and a duplex stainless steel. A Rietveld analysis program, Z-Rietveld ver. 1.0 was used to fit the anisotropically broadened patterns where the increase in Lorentzian full width at half maximum (FWHM) and the Gaussian FWHM involves information of the crystallite size and the dislocation density, respectively. The derived results were compared with those obtained by using Bragg-edge transmission spectrum analysis and electron backscatter diffraction (EBSD) observations.

Neutron Bragg-edge transmission imaging makes it possible to quantitatively visualize the two-dimensional distribution of microstructure within a sample. In order to examine its application to engineering products, time-of-flight Bragg-edge transmission imaging experiments using a pulsed neutron source were performed for plastically bent plates composed of a ferritic steel and a duplex stainless steel. The non-homogeneous microstructure distributions, such as texture, crystalline size, phase volume fraction and residual elastic strain, were evaluated for the cross sections of the bent plates. The obtained results were compared with those by neutron diffraction and electron back scatter diffraction, showing that the Bragg-edge transmission imaging is powerful for engineering use.

For the purpose of future visualization of the flow field in superfluid helium-4, clusters of the triplet state excimer 4He2* are generated along the micro-scale recoil tracks of the neutron-absorption reaction n + 3He → 3T + p. This reaction is induced by neutron irradiation of the 3He fraction contained in natural isotopic abundance liquid helium with neutron beams either from the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (JPARC)/Materials and Life Science Experimental Facility or from the Kyoto University Institute for Integrated Radiation and Nuclear Science. These 4He2* clusters are expected to be ideal tracers of the normal-fluid component in superfluid helium with several advantageous properties. Evidence of the excimer generation is inferred by detection of laser induced fluorescence emitted from the 4He2* clusters excited by a purpose-built short pulse gain-switched titanium:sapphire (Ti:sa) laser operating at a wavelength of 905 nm. The setup and performance characteristics of the laser system including the Ti:sa and two continuous wave re-pumping lasers are described. Detection at the fluorescence wavelength of 640 nm is performed by using optical bandpass filtered photomultiplier tubes (PMT). Electrical noise in the PMT acquisition traces could successfully be suppressed by post-processing with a simple algorithm. Despite other laser-related backgrounds, the excimer was clearly identified by its fluorescence decay characteristics. Production of the excimer was found to be proportional to the neutron flux, adjusted via insertion of different collimators into the neutron beam. These observations suggest that the apparatus we constructed does function in the expected manner and, therefore, has the potential for groundbreaking turbulence research with superfluid helium.

Energy-resolved neutron imaging at a pulsed source utilizes the energy-dependent neutron transmission measured via time-of-flight to extract quantitative information about the internal microstructure of an object. At the RADEN instrument at J-PARC in Japan, we use cutting-edge detectors employing micro-pattern detectors or fast Li-glass scintillators and fast, all-digital data acquisition to perform such measurements, while continuing their development toward better utilization of the intense neutron source. In particular, for the Micro-Pixel Chamber based Neutron Imaging Detector ({\mu}NID), a micro-pattern detector with a 400 {\mu}m pitch and employing 3He for neutron conversion, we have successfully improved the spatial resolution from 200 to 100 {\mu}m, increased the detection efficiency from 18 to 26% for thermal neutrons, and increased the maximum count rate from 0.4 to 1 Mcps. We are also testing a new readout element with a 215 {\mu}m pitch for further improved spatial resolution, and a {\mu}NID with boron-based neutron converter for increased rate performance., Comment: 8 pages, 5 figures; accepted to Proceedings of International Conference on Neutron Optics 2017, Nara, Japan (JPS Conference Proceedings)

Neutron diffractometry has been a critical tool for clarifying spin structures. In contrast, little attention has been paid to neutron transmission spectroscopy, even though they are different types of the same phenomenon. Soon, it will be possible to measure the wavelength dependence of transmissions easily using accelerator-driven neutron facilities. Therefore, we have started studying the potential of spectroscopy in magnetism, and in this paper, we report the first observation of a magnetic Bragg dip and Bragg edge in the neutron transmission spectra of a typical spin superstructure; clear antiferromagnetic Bragg dips and Bragg edges are found for a single crystal and powder of nickel oxide, respectively. The obtained results show that transmission spectroscopy is a promising tool for measurements under multi-extreme conditions and for the precise analyses of spin structures, not only in MW-class pulsed spallation source facilities but also in compact neutron source facilities.

Energy-resolved neutron imaging at a pulsed source utilizes the energy-dependent neutron transmission, measured via time-of-flight, to extract quantitative information on the internal microstructure of an object in situ. These techniques, however, are currently limited by the count-rate capability of available imaging detector systems, resulting in long measurement times and reduced spatial resolution. At RADEN, we are building on our previous detector development work to provide nearly three times improvement in rate performance of our micro-pixel chamber based neutron imaging detector $(_{\mu }$ NID) by changing from 3 He to a boron-based neutron converter and optimizing the shape for a much reduced event size and maximized detection efficiency. We are also designing a new micro-pattern readout element with an additional readout axis to facilitate clean event separation under high-rate conditions. Proof-of-principle testing at RADEN of the $_{\mu }$ NID with a flat, $1.2{\mu }m$ thick $^{10}B$ conversion layer confirmed a spatial resolution of 0.45 to 0.5 mm and indicated an improvement in rate capacity up to 22 Mcps or more. Once the boron converter is optimized for detection efficiency, this detector will help to unlock the full potential of these energyresolved neutron imaging techniques at pulsed sources.

Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS) measurements, and scanning and transmission electron microscope (SEM and TEM) of β-lactoglobulin (β-LG) are performed in alkyl (methyl, ethyl, and propyl) ammonium nitrate ionic liquids (RAN-ILs) – water mixtures at 25–100 °C. The addition of these RANs decreased the thermal denaturation temperature of β-LG, and the effect is larger with an increase of the hydrophobic part of the cation of the ILs. In ethyl ammonium nitrate (EAN) and propyl ammonium nitrate (PAN) mixtures, the fractal aggregate structure of β-LG was found after the thermal denaturation occurred. On the other hand, in methyl ammonium nitrate (MAN) mixture, an amorphous aggregate was formed as well as in NaCl and NaNO3 solutions. The difference of the effect between MAN and EAN (and PAN) could arise from the balance of hydrophobic/hydrophilic parts of the cation of RAN. These results are similar to those of alcohol-water mixtures. The nanoheterogeneous structure of the RAN-water mixture which consists of the hydrophobic and hydrophilic parts might affect the aggregation structure of β-LG.

The Energy-Resolved Neutron Imaging System RADEN, located at the J-PARC Materials and Life Science Experimental Facility in Japan, is the world's first dedicated high-intensity, short-pulsed neutron imaging beam line. To carry out energy-resolved neutron imging at RADEN, we use cutting-edge detector systems employing micropattern detectors and data acquisition systems based on Field Programmable Gate Arrays to provide the necessary sub-μs time resolution, high counting rates, and event-by-event background rejection. One such detector, the Micro Pixel Chamber-based Neutron Imaging Detector (μNID), provides a spatial resolution of 120 μm (s), time resolution of 0.6 μs, 18% detection efficiency for thermal neutrons, and effective gamma sensitivity of less than 10−12. We have recently increased the rate capacity of the μNID from 600 kcps to more than 8 Mcps via an upgrade of the readout electronics and the introduction of a new gas mixture optimized for higher count rate, better spatial resolution, and higher detection efficiency. We are also developing new detection elements with strip pitches of 280 μm and 215 μm, down from 400 μm, with a corresponding improvement in the spatial resolution expected. Here, we present the progress of the ongoing development of the μNID, including the results of recent on-beam tests performed at RADEN.

A new experimental technique to measure spatial distribution of small-angle neutron scattering (SANS) is proposed. Since SANS reflects the nanostructures of samples, high-efficiency mapping of the ...

Pulsed-neutron imaging is attractive technique in the research fields of energy-resolved neutron radiography and RANS (RIKEN) and RADEN (J-PARC/JAEA) are small and large accelerator-driven pulsed-neutron facilities for its imaging, respectively. To overcome the insuficient spatial resolution of the conunting type imaging detectors like μ NID, nGEM and pixelated detectors, camera detectors combined with a neutron color image intensifier were investigated. At RANS center-of-gravity technique was applied to spots image obtained by a CCD camera and the technique was confirmed to be effective for improving spatial resolution. At RADEN a high-frame-rate CMOS camera was used and super resolution technique was applied and it was recognized that the spatial resolution was futhermore improved.

The recently commissioned Energy-Resolved Neutron Imaging System, RADEN, located at the J-PARC Materials and Life Science Experimental Facility (MLF), is the world's first dedicated high-intensity, pulsed neutron imaging instrument. In addition to conventional radiography and tomography, the wide bandwidth and accurate measurement of neutron energy by time-of-flight is utilized to perform energy-resolved neutron imaging. Such techniques allow direct imaging of the macroscopic distribution of microscopic properties of materials in situ, including crystallographic structure and internal strain, nuclide-specific density and temperature distributions, and internal/external magnetic fields. To carry out such measurements in the high-rate, high-background environment at RADEN, we use cutting-edge detector systems, recently developed in Japan, employing micro-pattern detectors or fast Li-glass scintillators with high-speed, Field Programmable Gate Array-based data acquisition. These counting-type detectors offer sub-μs time resolution, high neutron count rates, and event-by-event gamma rejection. The available detectors offer a range of spatial resolutions from 0.3 to 3 mm and counting rates from 0.6 to 8 Mcps. In the present paper, we show the performance of these detectors as measured at RADEN. We also consider planned improvements to the detector systems that will allow us to achieve finer spatial resolutions by several factors and order-of-magnitude higher count rates.

Nuclear-polarized 3 He gas has recently been widely used in neutron facilities around the world for polarized neutron scattering. The large neutron absorption cross-section of 3 He depends strongly on the 3 He-spin and the neutron-spin directions, and a polarized neutron beam can be easily obtained by passing the beam through polarized 3 He gas, thus constituting a neutron spin filter (NSF). The relationships between neutron polarization Pn, neutron transmission Tn, and 3 He polarization PHe are

We have developed a polarized 3He neutron spin filter (NSF) for a new polarized neutron spectrometer, POLANO, at the Japan Proton Accelerator Research Complex (J-PARC). POLANO aims to utilize high energy neutrons polarized by a 3He NSF and spin analyzed by an array of magnetic supermirrors for inelastic neutron scattering. The 3He gas is continuously polarized in-situ by spin-exchange optical pumping to provide a highly and stably polarized neutron beam. The POLANO 3He NSF is designed to polarize neutrons with energies as high as 200 meV and fit in a restricted space. It is equipped with adiabatic fast passage NMR that enables one to flip the 3He spins, and consequently, the neutron spins.