Tatsuro Oda

New fabrication method for an ellipsoidal neutron focusing mirror with a metal substrate

We propose an ellipsoidal neutron focusing mirror using a metal substrate made with electroless nickel-phosphorus (NiP) plated material for the first time. Electroless NiP has great advantages for realizing an ellipsoidal neutron mirror because of its amorphous structure, good machinability and relatively large critical angle of total reflection for neutrons. We manufactured the mirror by combining ultrahigh precision cutting and fine polishing to generate high form accuracy and low surface roughness. The form accuracy of the mirror was estimated to be 5.3 μm P-V and 0.8 μm P-V for the minor-axis and major-axis direction respectively, while the surface roughness was reduced to 0.2 nm rms. The effect of form error on focusing spot size was evaluated by using a laser beam and the focusing performance of the mirror was verified by neutron experiments.

Development of highly-mechanically polished metal-substrate for neutron supermirrors

A small-angle neutron scattering instrument using an ellipsoidal focusing mirror has been developed at Hokkaido University and a prototype machine (mfSANS) has been installed at the JRR-3 research reactor at Japan Atomic Energy Agency (JAEA). They are based on an ellipsoidal focusing mirror on a borosilicate glass substrate. It turned out that borosilicate glass was very brittle and difficult to machine or polish it to the required surface-finishing process. In order to improve this situation, we decided to develop a method to create a metal substrate based ellipsoidal focusing mirror. As the first step, test pieces of flat and ellipsoidal surface neutron supermirrors using metal substrates were fabricated. They were first roughly shaped by a conventional numerically controlled (NC) cutting machine and amorphous NiP was plated. They were then machined using an ultrahigh precision cutting (UPC) method and finished by NC polishing techniques. Surface roughness of Ra ≈ 0.78 nm and surface figure error of submicrometer were realized so far.

Pulsed neutron time-dependent intensity modulation for quasi-elastic neutron scattering spectroscopy

We propose a basic formula and demonstration for a high-resolution quasi-elastic neutron scattering (QENS) by combining the time-of-flight (TOF) method with Modulation of Intensity by Zero Effort (MIEZE) type neutron spin echo spectroscopy. The MIEZE technique has the potential to develop a unique approach to study on slow dynamics of condensed matter; however, the energy resolution is limited owing to the hypersensitivity of the MIEZE signal contrast to the echo condition, which is strongly affected by the alignment of the instruments and the sample. The narrow allowance of the optimal alignment is a major obstacle to the wide use of this technique. Combining the TOF method with MIEZE (TOF-MIEZE), the hypersensitivity of MIEZE signals is significantly alleviated with a short pulsed beam. This robustness is very useful to optimize experimental alignments and enables accurate measurements of QENS. The experimental results demonstrate the characteristic of the TOF-MIEZE technique and are well described by the formula presented in this study.

Pulsed ultra-cold neutron production using a Doppler shifter at J-PARC

We have constructed a Doppler-shifter-type pulsed ultra-cold neutron (UCN) source at the Materials and Life Science Experiment Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). Very-cold neutrons (VCNs) with 136-

Development of a large plano-elliptical neutron-focusing supermirror with metallic substrates.

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Production of ultra cold neutrons by a doppler shifter with pulsed neutrons at J-PARC

velocity in a neutron beam supplied by a pulsed neutron source are decelerated by reflection on a m=10 wide-band multilayer mirror, yielding pulsed UCN. The mirror is fixed to the tip of a 2,000-rpm rotating arm moving with 68-

Supermirror neutron guide system for neutron resonance spin echo spectrometers at a pulsed neutron source

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Design and performance of horizontal-type neutron reflectometer SOFIA at J-PARC/MLF

velocity in the same direction as the VCN. The repetition frequency of the pulsed UCN is

Novel neutron reflectometer SOFIA at J-PARC/MLF for in-situ soft-interface characterization

8.33~\mathrm{Hz}

The ion beam sputtering facility at KURRI: Coatings for advanced neutron optical devices

and the time width of the pulse at production is