Results 1 - 10 of 57
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[en] Neutron resonance spin echo (NRSE) enables us to measure neutron quasielastic scattering with high energy resolution. Its energy resolution is limited by neutron beam divergence. This divergent effect can be corrected by installing guide field between pair of resonance spin flippers. In this paper, we propose a beam divergence correction coil for NRSE spectrometer and evaluate its efficiency by numerical simulations
[en] A multilayer spin splitter (MSS) is a device which gives the same effect as a magnetic field to the Larmor-precessing neutron. Since MSS is a single mirror, a neutron spin echo (NSE) can be much smaller (less than 1 m along the neutron beam) when MSSs successfully replace the Larmor precession magnetic field. The aim of our research is to replace the precession magnetic fields in NSE spectrometer by a set of MSSs and realize a very compact neutron spin echo spectrometer. In the present report, we will present the results of the preliminary experiment of the compact NSE spectrometer, and discuss its applicability to the pulsed neutron sources
[en] We have developed a resonance neutron-spin flipper (RSF) with high frequency applicable to pulsed sources. This flipper is necessary for new neutron resonance spin echo spectrometers installed at pulsed neutron sources. The RSF works only for monochromatic neutron beams because of the dependence of its spin-flip probability on neutron velocity. The RSF can, however, be applied to pulsed neutron beam with wide band wavelength by varying the amplitude of the applied oscillating magnetic field since the pulsed neutrons are resolved into monochromatic components according to their velocity. In this paper, we describe the RSF system applicable to pulsed neutron sources, measure the flipping efficiency and discuss the experimental results
[en] Neutron resonance spin echo (NRSE) spectroscopy enables us to measure neutron quasielastic scattering with high-energy resolution. It is desirable to apply NRSE spectroscopy to pulsed neutron sources because this application allows a very wide range of the spin echo time. We have already developed the neutron resonance spin flipper applicable to a polychromatic pulsed neutron beam, which is necessary for the TOF-NRSE method. Using this flipper, we have succeeded in observing spin echo signals with visibility higher than 0.65 for the pulsed neutron beam with wavelength from 0.3 to 0.9 nm. We discuss the prospect of the NRSE spectrometer with high-energy resolution on the basis of the present result
[en] We have developed a 1-dimensional elliptic mirror combining a supermirror coated with ion-beam sputtering and precise elliptic surface figured with the numerically-controlled local wet etching process. In this study, NiC/Ti supermirror (m = 4) was deposited on a precisely figured surface of synthesized quartz glass over 90 mm x 40 mm. Wideband neutrons of λ > 3.64A were focused with focal spot size down to 0.25 mm, peak intensity gain up to 6 without significant diffuse scattering. Time-of-flight measurements suggest that wideband neutrons are effectively focused to the focal point.
[en] We have succeeded in fabricating m=4.8 Ni/Ti and m=5.1 NiC/Ti supermirrors with high reflectivity and small d-spacing multilayer monochromator using ion beam sputtering instrument installed at KURRI. Here the number of m is a measure of critical angle in unit of critical angle of nickel. The reflectivity is above 0.6 for the m=5.1 NiC/Ti supermirror in which number of layer is 3000. The reflectivity is 0.065 at Bragg condition for the Ni/Ti monochromator (d=2.68 nm) in which number of layer is 10 000
[en] High-performance optical devices with a figure accuracy of sub-micrometer level and a surface roughness of atomic level are required to collect and/or to focus a neutron on a sample without scattering loss. To fabricate a high-performance neutron focusing supermirror, a two-stage numerically controlled local wet etching technique combined ion beam sputter deposition was developed. By applying this technique, a plano-elliptical substrate made of synthesized quartz glass with a figure accuracy of less than 0.5 μm was fabricated, and its surface was deposited with NiC/Ti multilayers by ion beam sputtering to produce an m=4 supermirror. The focusing performance of the supermirror was evaluated at the SUIREN of JRR-3M, and a focusing gain of 6 in peak intensity was achieved compared with a nonfocused direct beam.
[en] We have succeeded in fabricating high-reflectivity and small d-spacing which are 5.7 and 7.0 nm NiC/Ti multilayer neutron monochromators using ion beam sputtering technique. The reflectivities of these monochromators with d=5.7 and 7.0 nm are 0.81 and 0.91, respectively
[en] We have developed neutron spin flip choppers with high S/N ratio and high intensity for pulsed sources using multi-stage spin flip choppers. It is not easy for us to obtain a very short neutron pulse less than 10 μs using a spin flip chopper, due to the time constant L/R in the normal LR circuit. We will discuss a method obtaining a very short neutron pulse applying the modified push-pull circuit proposed by Ito and Takahashi  to the double spin flip chopper with polarizing guides
[en] The results of neutron reflectometry on measuring hydrogen content in a Pd thin film are presented and a new method of detecting hydrogen content in a thin film of hydrogen absorbing material is proposed. By neutron reflectometry, hydrogen content H/Pd in a 40 nm-thick Pd film is obtained as 0.42 at the surface and as 0.69 at the substrate under 0.02 MPa hydrogen pressure. In addition to the above results, we propose a new method for measuring hydrogen content in a thin film using multilayer spin splitters, which enables us to apply neutron phase-spin echo technique. In the new method, precision of hydrogen content can be improved