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Abstract We have studied the effect of beam collimation on the quality of images obtained with Talbot-Lau interferometry at the RADEN beam line in the J-PARC Materials and Life Science Experimental Facility. By using four typical beam collimations of RADEN, which were determined at a position relatively far from the interferometer, the blurring of images and the average intensity and visibility of interference patterns were observed. From these data, spatial resolutions and measurement precisions of images were experimentally evaluated. The obtained characteristics on each collimation condition are useful to design and optimize a new interferometer, and perform experiments at this beam line. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a multichannel parabolic guide for thermal neutron beam focusing. The guide was designed with multichannel structure, seven channels in the present case, to focus a neutron beam with wide cross section effectively. The multichannel structure is made with parabolically bent NiC/Ti supermirrors with critical reflection angles and 3.6 times as much as that of nickel and thickness of 0.55mm. The guide consists of two focusing devices with each length of 900mm, which are separated by a gap of 150mm for neutron beta decay experiments. The focal length of the guide is 995mm away from the exit of the guide. The cross section of the guide is at the entrance and at the exit. The guide was installed at a thermal neutron beam line for neutron-induced prompt gamma-ray analysis (PGA) of JRR-3M in JAEA with straight supermirror guides with . Focusing properties of the parabolic guide were measured at the focal point with a CCD imaging system and we obtained a gain of 9.6 and 4.1 in peak flux compared with those in cases of using the vacuum tube and the straight guide, respectively. The parabolic guide has been successfully used to enhance the efficacy of PGA and have also applied to neutron beta decay experiments. [Copyright &y& Elsevier]

Abstract: Neutron refractive optics is a powerful tool for beam focusing due to its large effective aperture compared to reflective optics. Because neutron refraction angle decreases with shorter wavelengths, the application of refractive optics has been restricted to the cold neutron range. To expand the applicable wavelength range, we have developed a new refractive optics using an amorphous perfluoropolymer. This refractive optics is composed of several hundred thin sheets, each of which has a large number of grooves on the top surface. The refraction experiment was performed at the H-8 beam port of KENS, and it was confirmed that the thermal neutron beam can be refracted using this material prism. [Copyright &y& Elsevier]

Abstract: Small-angle neutron scattering technique using polarized neutrons is powerful for studying structures in the range between nm and μm of magnetic materials. In addition, they have been used for the incident beam of focusing-geometry SANS instruments using a magnetic neutron lens, where a high polarization degree of about 99.9% is necessary because the imperfectness of the neutron polarization increases the background level. We are going to install such a magnetic focusing system on the new time-of-flight SANS (TOF-SANS) instrument at the J-PARC so as to make qmin smaller than 10−3 Å−1 and improve the resolution of the conventional TOF-SANS at low q. As a polarizing device of the instrument, two V-shaped polarizing super mirrors arranged in crossed geometry to enhance the polarization degree has been considered. In this paper, we present the concept and the detailed design of this device and its performance estimated by Monte Carlo simulations. [Copyright &y& Elsevier]

Abstract: We performed a cold neutron polarization experiment using a polarization device based on a quadrupole magnet. By passing through the aperture of the quadrupole magnet, positive and negative polarity neutrons are accelerated in opposite directions and spatially separated due to the magnetic field gradient. Then, we extracted the one-spin component and analyzed the polarization degree by using a sextupole magnet and position-sensitive detector. As a result, very high neutron polarization degree P=0.9993±0.0025 was obtained. Advantages of the quadrupole magnet as the neutron polarization device and its application to neutron scattering experiments are discussed. [Copyright &y& Elsevier]

Abstract: We have performed small-angle polarized neutron scattering experiments of spherical Fe16N2 nano-particles, which are potential candidate materials for high density magnetic recording tape. The results were analyzed based on a core-shell model, and we evaluated the magnetic structure of the particles. The correlation between the magnetic structure and magnetic stability of the particles were discussed in terms of high density recordings. [Copyright &y& Elsevier]

Abstract 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. [ABSTRACT FROM AUTHOR]

Abstract: Modulating permanent magnet sextupole lens (PMSx) for focusing pulsed cold neutrons is under development. The synchronized modulation of its field gradient suppresses the chromatic aberration which arises from the Time Of Flight method. The strength of the magnetic field, the torque, and the rise of temperature during its operation are studied on a fabricated prototype. Experiments on focusing pulsed very cold neutrons (VCN) at ILL (Institute of Laue Langevin, France) were carried out and VCN with around λ=40Å were focused by the PMSx at a focal length of about 0.5m. The experimental results are presented in conjunction with the principle of the neutron focusing and the modulating method of the focal strength of permanent magnet lens with the double ring structure. [Copyright &y& Elsevier]

Abstract: We have developed a magnetic neutron lens (MNL) based on an extended Halbach-type permanent sextupole magnet. The effective aperture size is 30mm in diameter and the length is 2400mm. The sextupole magnetic field distribution | B |=(G/2) r 2 with the gradient coefficient G=10,660±530T/m2 are generated inside the magnet, where r is the distance from the magnet center axis. The neutron-focusing property is investigated by using pulsed polarized neutrons. The obtained results are discussed in comparison with numerical simulation results. The application to the focusing-geometry small-angle neutron scattering experiments is discussed. [Copyright &y& Elsevier]

Abstract: We obtained highly polarized very cold neutrons through a quadrupole magnet with a large aperture. When neutrons go through a quadrupole magnet, parallel-spin neutrons are attracted to the magnet axis and anti-parallel-spin neutrons are repelled off the axis. Therefore, the neutrons through a sufficiently long quadrupole magnet have completely parallel-spin. At the downstream of the quadrupole magnet, we placed another quadrupole magnet to divide neutrons into two regions depending on their spin directions. We obtained the neutron polarization from the integrated count of the two regions and found it was 99.88±0.09 (stat.)±0.05 (syst.)%. [Copyright &y& Elsevier]

Abstract: We have designed and demonstrated a prototype on-beam spin-exchange optical pumping (SEOP) 3He neutron spin filter (NSF). It is designed as the incident neutron polarizer for spallation neutron sources, where the installation space is limited due to thick radiation shielding. The size of the NSF is roughly 50cm×50cm×25cm including the diode-laser optics with a frequency narrowing external cavity, and a cylindrical 3He cell as large as a diameter of 5cm and a length of 10cm can fit. A neutron beam test was performed at the NOP beamline of JRR-3 to see the performance of the NSF. [Copyright &y& Elsevier]

Abstract: A neutron scintillating detector and its data taking system have been developed for neutron scattering measurement. A 64-channel flatpanel photomultiplier is used for the Anger-camera method. The detection efficiency of γ-ray background is very low in the use of the ZnS/6LiF scintillator. The spatial resolution is less than 1mm. The effective area of this detector is around 25cm2, and it is easy to expand it to a larger area with small dead space using the multi-photomultiplier tubes system. The fast DAQ system has 10-bit 100MHz flash ADCs, FPGA chips and USB2.0 device. [Copyright &y& Elsevier]

Abstract: Precise measurement of neutron β decay allows determining the coupling constant of weak interaction independent of any nuclear structure. We have developed measurement system of neutron β decay at a thermal neutron beamline in JRR-3, JAEA. By using coincidence technique of two kinds of detectors, we have succeeded in detecting the signal of neutron β decay with S/N of 0.63 and count rate of 0.40cps. [Copyright &y& Elsevier]