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Kozawa, Tatsuya*; Fujihara, Masayoshi; Uchihara, Takeru*; Mitsuda, Setsuo*; Yano, Shinichiro*; Tamatsukuri, Hiromu; Munakata, Koji*; Nakao, Akiko*
Scientific Reports (Internet), 13, p.13750_1 - 13750_8, 2023/08
Times Cited Count：0 Percentile：0(Multidisciplinary Sciences)In condensed matter physics, pressure is frequently used to modify the stability of both electronic states and atomic arrangements. Under isotropic pressure, the intermetallic compound MnP has recently attracted attention for the interplay between pressure-induced superconductivity and complicated magnetic order in the vicinity. By contrast, we use uniaxial stress, a directional type of pressure, to investigate the effect on the magnetism and crystal structure of this compound. An irreversible magnetisation response induced by uniaxial stress is discovered in MnP at uniaxial stress as low as 0.04 GPa. Neutron diffraction experiments reveal that uniaxial stress forms crystal domains that satisfy pseudo-rotational symmetry unique to the MnP-type structure. The structure of the coexisting domains accounts for the stress-induced magnetism. We term this first discovered phenomenon atomic reconstruction (AR) induced by uniaxial stress. Furthermore, our calculation results provide guidelines on the search for AR candidates. AR allows crystal domain engineering to control anisotropic properties of materials, including dielectricity, elasticity, electrical conduction, magnetism and superconductivity. A wide-ranging exploration of potential AR candidates would ensure that crystal domain engineering yields unconventional methods to design functional multi-domain materials for a wide variety of purposes.
Takai, Shizuka; Namekawa, Masakazu*; Shimada, Taro; Takeda, Seiji
IEEE Transactions on Nuclear Science, 69(7), p.1789 - 1798, 2022/07
Times Cited Count：0 Percentile：0.01(Engineering, Electrical & Electronic)To reduce a large amount of contaminated concrete rubble stored in the Fukushima Daiichi Nuclear Power Station site, recycling low-radioactivity rubble within the site is a possible remedy. To promote recycling while ensuring safety, not only the average radioactivity but also the radioactivity distribution of concrete rubble should be efficiently evaluated because the details of rubble contamination caused by the accident remain unclear and likely include hotspots. However, evaluating inhomogeneous contamination of thick and/or dense materials is difficult using previous measurement systems, such as clearance monitors. This study experimentally confirmed the potential applicability of image reconstruction algorithms for radioactivity distribution evaluation in concrete rubble filled in a chamber. Radiation was measured using plastic scintillation fiber around the chamber (50 
50 40 cm
). Localized hotspots were simulated using standard sources of 
Cs, which is one of the main nuclides of contaminated rubble. The radioactivity distribution was calculated for 100 or 50 voxels (voxel size: (10 cm) or 10 10 20 cm) constituting the chamber. For 100 voxels, inner hotspots were undetected, whereas, for 50 voxels, both inner and surface hotspots were reconstructible. The distribution evaluated using the maximum likelihood expectation maximization algorithm was the most accurate; the average radioactivity was estimated within 70% accuracy in all seven cases.
(Al,Ga)
O
scintillator Compton camera mounted on an unmanned helicopterShikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.
Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12
Times Cited Count：37 Percentile：96.39(Nuclear Science & Technology)The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 44 to 88 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m 60 m and 65 m 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the 
-ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10
).
4 surfaceTakahashi, Masamitsu; Yoneda, Yasuhiro; Yamamoto, Naomasa*; Mizuki, Junichiro
Physical Review B, 68(8), p.085321_1 - 085321_5, 2003/08
Times Cited Count：17 Percentile：62.72(Materials Science, Multidisciplinary)The 
, 
and phases of the GaAs(001)-24 surface have been investigated by 
surface X-ray diffraction in an As flux and at temperatures ranging from 480
C to 610C. It has been found that the fractional-order peaks originating from the fourfold symmetry show shift in the [110] direction as well as significant broadening of the peaks in the and phases. The direction of the peak shift is characteristic in each phase. This behavior is explained by the formation of the antiphase domain boundaries. The atomic structure of the domain boundaries is discussed.
JNC TN9400 2000-021, 104 Pages, 2000/03
JNC-TN9400-2000-021.pdf:5.21MB
ln this report, research works performed in the Structura1 Safety Engineering Group of OEC/JNC are summarized as the final report of the doctoral fellowship. The main objective of this study is for the enhancement of the nondestructive evaluation techniques for structural components of both magnetic and nonmagnetic material. Studies in three topics have been carried out aiming at the quantitative evaluation of crack with the eddy current testing and the validation of a natural magnetic field based NDE method for detecting mechanical damages in a paramagnetic material. ln the first part of the study, an approach to the reconstruction of the natural crack was proposed and implemented with an idealized crack model for its validation. ln the second part, the correlation of the natural magnetization and the mechanical damages in the SUS304 stainless steel was investigated by using an experimental approach. ln part 3, an inverse method of the measured magnetic fields is proposed for the reconstruction of magnetic charges in the inspected material by using an optimization method and wavalet. As the first work, an approach to the reconstruction of an idealized natural crack of non-vanishing conductivity is proposed with use of signals of eddy current testing. Two numerical models are introduced at first for modeling the natural crack in order to represented it with a set of crack parameters. A method for the rapid prediction of the eddy current testing signals coming from these idealized cracks is given then by extending a knowledge based fast forward solver to the case of a non-vanishing conductivity. Based on this fast forward solver, the inverse algorithm of conjugate gradient method is updated to identify the crack parameters. Several examples are presented finally as a validation of the proposed strategy. The results show that both the two numerical models can give reasonable reconstruction results for signal of low noise. The model concerning the touch of ...
; Aoto, Kazumi;
JNC TN9400 99-061, 32 Pages, 1999/07
In this report, reconstruction of magnetic charges induced by mechanical damages in a test piece of SUS304 stainless steel is performed as a part of eforts to establish a passive nondestructive testing method on the basis of the inspection of leakage magnetic field. The approach for solving this typical ill-posed inverse problem is selected as a way in the least square method category. Concerning the ill-poseness of the system of equations, an iteration algorithm is adopted to its solving in which the designations of initial profile, the weight coefficients and the total number of iterations are taken as means of reqularization. From examples using simulated input data, it is verified that the approach gives good reconstruction results in case of signals with a relative high S/N ratio. For improving the robustness of the proposed method, a Galerkin procedure with base functions chosen as the Daubechies' wavelet is also introduced for discretizing the governing equation. By comparing the reconstruction results of the least square method and those using wavelet discretization, it is found that the wavelet used approach is more feasible in the inversion of noise polluted signals. Reconstruction of 1-D and 2-D magnetic charges with the least square strategy and reconstruction of an 1-D problem with the wavelet used method are carried out from both simulated and measured magnetic field signals which are used as the validation of the proposed inversion strategy.
JNC TN9400 99-009, 39 Pages, 1998/12
In this paper, an approach to the reconstruction of an idealized natural crack of non-vanishing conductivity is proposed with use of signals of eddy current testing. Two numerical models are introduced at first for modeling a Stress Corrosion Crack (SCC) in order it possibly to be represented by a set of crack parameters. A method for rapid prediction of the eddy current testing signals arisen from these idealized cracks is given then by extending a knowledge based fast forward solver developed by authors to the case of a non-vanishing conductivity. On the other hand, the inverse algorithm of conjugate gradient method is improved to reconstruct the crack parameters and is implemented with the pick-up signals and gradients calculated by using the rapid forward solver. Several examples are presented finally for validating the proposed strategy. The results verified that both of the models can give reasonable reconstruction results in case of a low noise level. The model concerning the touch of crack surfaces with a conducting band region surrounded by the crack edge, however, is proved more efficient than the model using a conductivity distribution from the point of view of both reconstruction speed and accuracy.
Kishimoto, Maki; Sakasai, Kaoru; Ara, Katsuyuki; Fujita, Takaaki; *
IEEE Transactions on Plasma Science, 24(2), p.528 - 538, 1996/04
Times Cited Count：1 Percentile：4.38(Physics, Fluids & Plasmas)no abstracts in English
; ; ;
JAERI-M 84-067, 74 Pages, 1984/04
no abstracts in English
7 reconstruction during Ge/Si heteroepitaxial growthUozumi, Yuki; Yamazaki, Tatsuya*; Asaoka, Hidehito
no journal, ,
no abstracts in English
7 reconstruction during atomic hydrogen adsorptionUozumi, Yuki; Asaoka, Hidehito
no journal, ,
We have succeeded in measurements of the surface stress in Si(111) as a function of 77 reconstruction by comparison with the H-terminated Si(111) 11 surface. In order to obtain information on both the surface stress and the surface reconstruction simultaneously, we havecombined the surface-curvature and the reflection-high-electron-energy-diffraction instrumentations in an identical ultrahigh vacuum system. The stress evolution shows a decrease of tensile stresscorresponding to the formation of H-termination at the beginning of the atomic hydrogen exposure of Si(111) 77 surface. After the above treatment, a complete transformation of the surface structure occurs from the reconstructed surface to the 11 one. As a result, we find the Si(111) 11 surface releases 1.7 N/m (=J/m
), or (1.4 eV/(11 unit cell)), of the surface energy from the strong tensile Si(111) 77 reconstruction.
7 and H-Si(111)11Uozumi, Yuki; Asaoka, Hidehito
no journal, ,
no abstracts in English
Suzuki, Shota; Asaoka, Hidehito; Uozumi, Yuki; Kondo, Keietsu; Yamaguchi, Kenji
no journal, ,
no abstracts in English
2 single and double domain structureSuzuki, Shota; Yano, Masahiro; Uozumi, Yuki; Asaoka, Hidehito; Yamaguchi, Kenji*
no journal, ,
no abstracts in English
2 surface by low temperature desorption of oxide layerSuzuki, Shota; Yano, Masahiro; Uozumi, Yuki; Asaoka, Hidehito; Yamaguchi, Kenji*
no journal, ,
no abstracts in English
Yamada, Ippei; Wada, Motoi*; Moriya, Katsuhiro; Kamiya, Junichiro; Kinsho, Michikazu
no journal, ,
no abstracts in English
Yamada, Ippei; Wada, Motoi*; Kamiya, Junichiro; Kinsho, Michikazu
no journal, ,
no abstracts in English
Yamada, Ippei; Wada, Motoi*; Kamiya, Junichiro; Kinsho, Michikazu
no journal, ,
no abstracts in English
Shikaze, Yoshiaki
no journal, ,
no abstracts in English
Terasawa, Tomoo
no journal, ,
Graphene, a two-dimensional material consisting of a honeycomb lattice of C atoms, has attracted much attention from basic physics to applications because of its extremely high carrier mobility and half-integer quantum Hall effect. Since a choice of substrate affects the properties of graphene, the synthesis and properties of graphene on various substrates have been the subject of surface science research. The interface between graphene and Au is expected in the field of spintronics because Au has a large atomic number and a large spin-orbit interaction. On the other hand, the atomic configuration in this interface is often unknown, and therefore, the angle-resolved photoemission spectroscopy (ARPES) experiments and density functional theory (DFT) calculations do not match each other for this interface. Here, we report the band structure of graphene on the Hex-Au(001) reconstructed surface using ARPES and DFT calculations. Since the solubility of C in Au is very low, graphene can be grown on Au surfaces by chemical vapor deposition (CVD). Hex-Au(001) reconstruction was kept even after the CVD growth of graphene. Therefore, the ARPES measurement was carried out for graphene on the well-known atomic configuration of Hex-Au(001). The ARPES intensity map shows the bandgap in the graphene pi band close to the Au 6sp band. The DFT calculated band structure shows the bandgap at the crossing point of the graphene pi and Au 6sp bands. We discuss that the bandgap originates from the hybridization between graphene and Au, similar to the case of graphene and Au interface on the SiC substrate. As the Rashba splitting of 100 meV was observed in the graphene and Au interface on the SiC substrate, we expect that the hybridization between graphene and Au is essential for the future applications of graphene for spintronic devices.
