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A neutron scintillation detector based on a position-sensitive photomultiplier has been developed for neutron spin echo and small angle neutron scattering measurements. This photomultiplier has good spatial resolution, less than 1 mm2. The detection efficiency of gamma ray background is very low for using a thin ZnS/6LiF scintillator. The effective area of this detector is around 60 cm2.

Neutron imaging is one of the most powerful tools for nondestructive inspection owing to the unique characteristics of neutron beams, such as high permeability for many heavy metals, high sensitivity for certain light elements, and isotope selectivity owing to a specific nuclear reaction between an isotope and neutrons. In this study, we employed a superconducting detector, current-biased kinetic-inductance detector (CB-KID) for neutron imaging using a pulsed neutron source. We employed the delay-line method, and high spatial resolution imaging with only four reading channels was achieved. We also performed wavelength-resolved neutron imaging by the time-of-flight method for the pulsed neutron source. We obtained the neutron transmission images of a Gd–Al alloy sample, inside which single crystals of GdAl $_3$ were grown, using the delay-line CB-KID. Single crystals were well imaged, in both shapes and distributions, throughout the Al–Gd alloy. We identified Gd nuclei via neutron transmissions that exhibited characteristic suppression above the neutron wavelength of 0.03 nm. In addition, the $^{155}$ Gd resonance dip, a dip structure of the transmission caused by the nuclear reaction between an isotope and neutrons, was observed even when the number of events was summed over a limited area of 15 $\mu$ m × 12 $\mu$ m. Gd selective imaging was performed using the resonance dip of $^{155}$ Gd, and it showed clear Gd distribution even with a limited neutron wavelength range of 1 pm. [ABSTRACT FROM AUTHOR]

We previously proposed a method to detect neutrons by using a current-biased kinetic inductance detector (CB-KID), where neutrons are converted into charged particles using a 10B conversion layer. The charged particles are detected based on local changes in kinetic inductance of X and Y superconducting meanderlines under a modest DC bias current. The system uses a delay-line method to locate the positions of neutron-10B reactions by acquiring the four arrival timestamps of signals that propagate from hot spots created by a passing charged particle to the end electrodes of the meanderlines. Unlike conventional multi-pixel imaging systems, the CB-KID system performs high spatial resolution imaging over a 15 mm × 15 mm sensitive area using only four channel readouts. Given the large sensitive area, it is important to check the spatial homogeneity and linearity of detected neutron positions when imaging with CB-KID. To this end we imaged a pattern of 10B dot absorbers with a precise dot pitch to investigate the spatial homogeneity of the detector. We confirmed the spatial homogeneity of detected dot positions based on the distribution of measured dot pitches across the sensitive area of the detector. We demonstrate potential applications of the system by taking a clear transmission image of tiny metallic screws and nuts and a ladybug. The image was useful for characterizing the ladybug noninvasively. Detection efficiencies were low when the detector was operated at 4 K, so we plan to explore raising the operating temperature towards the critical temperature of the detector as a means to improve counting rates. [ABSTRACT FROM AUTHOR]

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 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: Neutron magnetic optics is a spin-selective optics and suitable for precise focusing since it is free from interactions with materials. We discuss its applications to measure the small angle neutron scattering in low-q regions. [Copyright &y& Elsevier]

We have developed instruments for magnetic neutron holography (MNH) using polarized white neutrons to investigate the local magnetic structures of magnetic alloys. We chose the 3He spin filter method as the neutron polarizer to polarize neutrons over a wide wavelength range of up to a few 100 meV. We developed a magnet device to saturate the magnetizations of ferromagnetic samples, and instruments to transport polarized neutrons from a 3He spin filter to the MNH sample. The neutron polarization, P n , at the beginning of the MNH experiments was confirmed to be 0.46, which is feasible for MNH. Using the developed instruments, we obtained preliminary results for the room-temperature ferromagnetic alloy Fe 0.08 Co 0.92. Technical problems encountered in the experiments and ways to overcome them are discussed. Based on these results, we believe that MNH that use polarized neutrons is promising. [ABSTRACT FROM AUTHOR]

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]

We have preliminarily investigated the performance of the optical capillary gas proportional counter (CGPC) to obtain the absorption point of cold neutron at JRR-3 in JAERI. The CGPC with a gas mixture of 3He+8%CH4+2%TMA at 1.1 atm was operated at the gas gain of up to 10 000. A track image produced from a nuclear reaction between a cold neutron and 3He was a straight line. For the track image, the triton and the proton were identified. The identification indicates that the neutron absorption point can precisely determine from the track image. [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]