Combination of crystal growth with optical floating zone and evaluation of Nd3+:LaAlO3 crystals with the dynamic nuclear polarization of 139La and 27Al.

Producing a polarized lanthanum (La) target with high polarization and long relaxation time is crucial for realizing time-reversal violation experiments using polarized neutron beams. We use a LaAlO3 crystal doped with a small amount of Nd3+ ions for the polarized lanthanum target. Optimizing the amount of Nd3+ ions is considerably important because the achievable polarization and relaxation time strongly depend on this amount. We established a fundamental method to grow single crystals of Nd3+:LaAlO3 using an optical floating zone method that employs halogen lamps and evaluated the crystals with the dynamic nuclear polarization (DNP) method for polarizing nuclear spins. Two crystal samples were grown by ourselves and evaluated with the DNP at 1.3 K and 2.3 T for the first time, except for the target materials of protons. The enhancement of nuclear magnetic resonance signals for 139La and 27Al was successfully observed, and the enhancement factors were eventually 3.5 ± 0.3 and 13 ± 3 for the samples with Nd3+ ions of 0.05 and 0.01 mol. %, respectively. These enhancement factors correspond to absolute vector polarizations of 0.27% ± 0.02% (Nd3+ 0.05 mol. %) and 1.4% ± 0.3% (Nd3+ 0.01 mol. %). Although the obtained polarizations are still low, they are acceptable as a first step. The combination scheme of the crystal growth and the evaluation of the crystals is found to be effectively applicable for optimizing the amount of Nd3+ ions for improving the performance of the polarized target.

Development of Neutron Interferometer Using Multilayer Mirrors and Measurements of Neutron-Nuclear Scattering Length with Pulsed Neutron Source.

This study entailed the successful deployment of a novel neutron interferometer that utilizes multilayer mirrors. The apparatus facilitates a precise evaluation of the wavelength dependence of interference fringes utilizing a pulsed neutron source. Our interferometer achieved an impressive precision of 0.02 rad within a 20-min recording time. Compared to systems using silicon crystals, the measurement sensitivity was maintained even when using a simplified disturbance suppressor. By segregating beam paths entirely, we achieved successful measurements of neutron-nuclear scattering lengths across various samples. The values measured for Si, Al, and Ti were in agreement with those found in the literature, while V showed a disparity of 45%. This discrepancy may be attributable to impurities encountered in previous investigations. The accuracy of measurements can be enhanced further by mitigating systematic uncertainties that are associated with neutron wavelength, sample impurity, and thickness. This novel neutron interferometer enables us to measure fundamental parameters, such as the neutron-nuclear scattering length of materials, with a precision that surpasses that of conventional interferometers.

Neutron Imaging Using a Fine-Grained Nuclear Emulsion.

A neutron detector using a fine-grained nuclear emulsion has a sub-micron spatial resolution and thus has potential to be applied as high-resolution neutron imaging. In this paper, we present two approaches to applying the emulsion detectors for neutron imaging. One is using a track analysis to derive the reaction points for high resolution. From an image obtained with a 9 µm pitch Gd grating with cold neutrons, periodic peak with a standard deviation of 1.3 µm was observed. The other is an approach without a track analysis for high-density irradiation. An internal structure of a crystal oscillator chip, with a scale of approximately 30 µm, was able to be observed after an image analysis.

Characterization of multimetric variants of ubiquitin carboxyl-terminal hydrolase L1 in water by small-angle neutron scattering.

Here, we illustrated that the morphological structures of ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) variants and Parkinson's disease (PD) exhibit good pathological correlation by a small-angle neutron scattering (SANS). UCH-L1 is a neuro-specific multiple functional enzyme, deubiquitinating, ubiquityl ligase, and also involved in stabilization of mono-ubiquitin. To examine the relationship between multiple functions of UCH-L1 and the configuration of its variants [wild-type, I93M (linked to familial Parkinson's disease), and S18Y (linked to reduced risk of Parkinson's disease)], in this report, we proposed that these were all self-assembled dimers by an application of a rotating ellipsoidal model; the configurations of these dimers were quite different. The wild-type was a rotating ellipsoidal. The globular form of the monomeric component deformed by the I93M mutation. Conversely, the S18Y polymorphism promoted the globularity. Thus, the multiple functional balance is closely linked to the intermolecular interactions between the UCH-L1 monomer and the final dimeric configuration.

Development of a neutron detector based on a position-sensitive photomultiplier.

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.