Elliptic neutron-focusing supermirror for illuminating small samples in neutron reflectometry

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.

Application of precise neutron focusing mirrors for neutron reflectometry: latest results and future prospects

A large-area focusing supermirror manufactured with ultra-precision machining has been employed at the SOFIA reflectometer at the J-PARC Materials and Life Science Experimental Facility, and a gain of approximately 100% in the neutron flux was achieved. For future upgrade, optics using the focusing mirror for multi-incident-angle neutron reflectometry are proposed, in order to reveal evolutions of interfacial structures for operando measurements with a wide reciprocal space.

Neutron reflectometry (NR) is a powerful tool for providing insight into the evolution of interfacial structures, for example via operando measurements for electrode–electrolyte interfaces, with a spatial resolution of nanometres. The time resolution of NR, which ranges from seconds to minutes depending on the reflection intensity, unfortunately remains low, particularly for small samples made of state-of-the-art materials even with the latest neutron reflectometers. To overcome this problem, a large-area focusing supermirror manufactured with ultra-precision machining has been employed to enhance the neutron flux at the sample, and a gain of approximately 100% in the neutron flux was achieved. Using this mirror, a reflectivity measurement was performed on a thin cathode film on an SrTiO₃ substrate in contact with an electrolyte with a small area of 15 × 15 mm. The reflectivity data obtained with the focusing mirror were consistent with those without the mirror, but the acquisition time was shortened to half that of the original, which is an important milestone for rapid measurements with a limited reciprocal space. Furthermore, a method for further upgrades that will reveal the structural evolution with a wide reciprocal space is proposed, by applying this mirror for multi-incident-angle neutron reflectometry.

Focusing and imaging of cold neutrons with a permanent magnetic lens

This paper reports imaging of objects with slow neutrons, specifically very cold neutrons and cold neutrons, at Institut Laue Langevin, using novel, permanent magnet (Nd₂Fe₁₄B) compound refractive lenses (MCRL) with a large 2.5 cm bore diameter. The MCRL focuses and images spin-up neutrons and defocuses spin-down neutrons via a large, radial magnetic field gradient. A single lens neutron microscope, composed of an MCRL objective lens with 2-fold magnification, was tested using very cold (slow) neutrons at 45 Å wavelength. One-to-one imaging was obtained using 16.7 Å polarized neutrons. The magnetic field gradient of the MCRL was measured by raster-scanned pencil beams on D33. Finally, a compound neutron microscope was realized using an MCRL condenser lens, which provided increased illumination of objects, and an MCRL as objective lens to produce 3.5-fold magnification.