Three-dimensional (3D) X-ray topography was used to characterize diamond anvil crystals before and after application of ultra-high pressure at 50, 70 and 99.4 GPa. The diffraction planes examined and the wavelength of the monochromatic X-rays were (004), (333), {224}, {440} and 0.0521 nm, respectively. Images of lattice defects in the diamond crystals were reconstructed by stacking approximately 500 X-ray limited projection topographs using the image processing software Image J. The 3D structures and nature of the lattice defects were identified from the reconstructed topographs. A pyramidal shape of four parts of stacking faults was identified using the visibility or invisibility of defect images with each diffraction plane. No significant changes of the lattice defects in the diamond crystals were observed under pressurization at 70 GPa. However, one of the anvil crystals shaped from the same rough crystal was broken into pieces at 99.4 GPa. The fracture stress is very low value rather than the calculated one based on (111) [110] slip system mechanism. In the broken crystal, the center line of plurality of the pyramidal shape of stacking faults differed in the location from the culet area. The breaking of diamond crystal was dependent on the distribution of plane defects in the crystal.

Synthesized diamond crystals grown at high temperatures and high pressures were characterized by three-dimensional X-ray topography. The diffraction planes and wavelength of the monochromatic X-rays used were (004), {111}, and {12,12,8}, and 0.0521 nm, respectively. Images of lattice defects in diamond crystals were reconstructed from a stack of about 300 X-ray limited projection topographs using the image processing software Image-J. The three-dimensional structures and nature of lattice defects were identified on the basis of the reconstructed topographs. The pyramidal shape of the four-part stacking fault generated from the seed crystal was identified using the dependence of visible or invisible defect images with diffraction planes. The sector boundary between the [001] and (111] growth directions was also first observed by three-dimensional topography. The image of the sector boundary did not show any dependence on diffraction planes. (C) 2018 The Japan Society of Applied Physics

In this study, a standard test piece (termed a phantom) was designed to determine the minimum detectable refraction angle in X-ray diffraction-enhanced imaging (DEI). The phantom had an acrylic exterior and a pentagonal prism shape with a continuously variable angle alpha that corresponded to the supplementary angle of two X-ray irradiated planes. The refraction angle was affected by the inclination angle of the two irradiation planes when the X-rays were normally incident to the surface. Thus, the minimum detectable refraction angle was determined from the observed contrast. The boundary of the phantom between the slant face area and the flat plane area was clearly recognized for a large angle a. However, the boundary image was not observed for extremely small a values. In the latter case, the refraction angle for the X-ray beam was less than the angular resolution of the DEI equipment used. In the present study, the minimum detectable refraction angle for the DEI apparatus in the optical system constructed in a vertical-wiggler beamline (the BL-14B beamline) at the Japanese KEK-PF synchrotron facility was determined. The results indicated that the minimum detectable refraction angle was 3.8 x 10(-6) rad for a 30 keV X-ray beam, as determined using an asymmetric 440 reflection collimator with a 10 degrees off-angle and a symmetric 440 reflection analyzer. (C) 2017 The Japan Society of Applied Physics

Large vacancy clusters in aluminum single crystals with low dislocation density, which show up as black dots in X-ray topographs, generate new dislocations and stacking faults during heat treatments. In order to obtain dislocation-free or low-dislocation-density metal single crystals, it is necessary to suppress the formation of large vacancy clusters. To this end, our starting material was either (1) ultrahigh-purity aluminum, intended to minimize the number of nucleation sites for large vacancy clusters, or (2) a dilute alloy of Zn in Al, intended to block the migration of excess vacancies by binding them with zinc atoms during slow cooling. Single crystals of the Al-Zn dilute alloy failed to improve the perfection unless a large vacancy cluster was formed. Upon cyclic annealing, however, the number density of black dots in X-ray topographs of ultrahigh-purity aluminum crystals decreased rapidly and significantly. It was thus confirmed that using a high-purity starting material was effective in suppressing the formation of large vacancy clusters.

The vacancy generation process in ultrahigh-purity aluminum single crystals with a low dislocation density was investigated by synchrotron radiation topography using a white X-ray beam. Some straight lines were observed in the topographs taken after temperature rose to 300℃ from room temperature, and they were confirmed to be rows of successive small interstitial-type dislocation loops grown as vacancy sources. It was concluded that the thermal generation mechanism of vacancies in ultrahigh-purity aluminum single crystals with a low dislocation density consists of the following two steps. First, small interstitial loops are heterogeneously formed in the crystal lattice; second, these convert to lengthened loops with the development of screw components and finally grow into rows of dislocation loops emitting vacancies into the lattice. However, contribution of new vacancy generation mechanism, growth of row of interstitial type dislocation loop for thermal equilibrium vacancy concentration is less than several percent. Therefore, major vacancy source is small vacancy cluster or vacancy type dislocation loops grown after slow cooling during crystal growth.

Crystalline perfection in organic charge-transfer complex single crystals, κ-(BEDT-TTF)2Cu[N(CN)2]Br, was characterized by means of synchrotron X-ray topography. Single crystals of κ-(BEDT-TTF)2Cu[N(CN)2]Br were grown electrochemically using a relatively large glass cell in order to scale up the synthesis. The quality of the crystals was examined using white and monochromatic X-ray topography. There was no asterism of each spot in the Laue photographs, though the defect image in the spot was not resolved because of low-resolution power of the white beam topography. We also obtained monochromatic X-ray topographs with 1.0 Å X-rays and were able to observe line images of dislocations. Dislocation density of the specimen was approximately 7 x 103 cm-2 on an average in the whole area of crystal. However, dislocation lines were annihilated in the topograph taken after annealing at room temperature for 5 months. Furthermore, new lattice defects were generated in the crystal after similar room temperature annealing for 15 months. The change of defect structure was caused by X-ray irradiation because dislocations in the un-irradiated crystal were observed by the monochromatic X-ray topography even after 2 years annealing at room temperature. Point defects formed by the X-ray irradiation probably interacted with grown-in dislocations and secondary defects were formed in the specimen crystal, though a long time was needed for this reaction at room temperature.

The attenuation of 10 MHz ultrasound in aluminum has been measured by the pulse reflection method at temperatures between 0.4 and 1.2 K. Three cylindrical single-crystal specimens of high purity and perfection, having 99.9999% of purity and low density of dislocations, were used and their crystallographic orientations were [100], [110] and [111]. The temperature dependence of attenuation in the superconducting state was analyzed on the basis of the BCS theory, and the apparent superconducting energy gap was determined for the above three sound propagation directions. By using these results, the energy gap anisotropy in the electronic k -space was derived. The gap value ranged between 3.56 and 3.14 in units of (1/2) k B T c . The gap was largest for the [100] direction, somewhat smaller for the [110] direction, and especially small for the [111] direction. These conclusions were in agreement with existing experimental and theoretical results.

The X-ray refraction imaging technique was applied to the quantitative study of hydrogen diffusion in titanium-hydride. Hydrogen diffusivity in titanium-hydride was determined by direct observation of the hydride. The hydride was formed on the surface of titanium by electrolytic-charging at 63°C. The specimens were cut into 1-mm thick slices for cross-sectional observations. The hydride layer was observed using the diffraction-enhanced X-ray imaging (DEI) method with asymmetric analyzer. Boundaries between titanium and the hydride were observed as thick black or white lines parallel to the specimen surface in the DEI images similar to previously reported results. Hydride distribution caused by hydrogen diffusion from the surface was converted to the intensity profiles of refraction images of the hydride using the measured rocking curve from an analyzer. The hydrogen diffusivity was calculated from the intensity profiles using the solution of the appropriate diffusion equation. The obtained hydrogen diffusivity in titanium-hydride depended upon the hydrogen concentration. The diffusivity showed good agreement with the widely accepted values in the low hydride concentration region.

X-ray topographic studies on characterization of semiconductor thin layer were reviewed. Reflection topographs of thin layer were taken by synchrotron radiation X-ray from a storage ring. In these papers, relaxation mechanisms of mismatch in lattice constant between thin layer and substrate were clarified and critical thickness for formation of misfit dislocations was determined for various hetero-epitaxial grown semiconductor thin film. Investigations using grazing incident X-ray topography on semiconductor thin film were also surveyed.

Introduction X-ray diffraction-enhanced imaging (DEI) method is a powerful method for observation of light materials [1]. The method has been successfully used, and is seeing excellent and rapid progress as a diagnostic tool in medicine and materials science [2]. However, almost all investigations thus far have been limited to qualitative observations. A few quantitative studies, such as the determination of activation energies of physical phenomena, have been reported [3]. In particular, there have been no previous reports about the ability to resolve differences in the refraction index, i.e., density differences. We have therefore designed and fabricated a standard test piece (phantom) for determining the density-change resolution of the DEI method, and used it to evaluate the density-change resolution of a DEI apparatus constructed in a precise X-ray diffraction station in KEK-PF.

The X-ray refraction imaging technique, diffraction-enhanced X-ray imaging (DEI) method with an asymmetric reflection analyzer was applied to determine the distribution profile of hydride in titanium. Horizontal magnification of the image by the asymmetric reflection was 9 times. Hydride was formed on titanium surface by electrolytic-charging at room temperature for 10, 25.5, 48 and 150 h. The specimen was cut into a 1-mm thick slice for cross-sectional observation. Hydride layer was observed by DEI method as a thick black or white line parallel to the surface. X-ray intensity profile of hydride was measured from the DEI image and converted to the deviation angle of X-ray by refraction using the observed rocking curve. The distribution of refraction index was calculated from the deviation angle of X-ray using Snell’s low. Finally distribution of ratio of hydride and titanium, the concentration profile of hydride, was obtained from that of the refraction index. The distribution profile of hydride in titanium was determined to accuracy of the order of micrometer by means of the DEI method with asymmetric reflection analyzer.

The X-ray refraction imaging technique, diffraction-enhanced X-ray imaging (DEI) method was applied to determine the .hydrogendiffusivity in titanium-hydride.Hydride was formed on titanium surface by electrolytic-charging at room temperature for 6, 12, 18, 24 and 48 h.The specimen was cut into a 1-mm thick slice for cross-sectional observation.Hydride layer was observed by DEI method as a thick black or white line parallel to the surface.Hydride distribution caused by hydrogen diffusion from the surface was calculated using assumed hydrogen diffusivity and a solution of diffusion equation.And the results were converted to the intensity profile of refraction images of the hydride using the measured rocking curve from an analyzer.The intensity profile was compared with that obtained from the photographs and fitted diffusivity was decided by trial and error.The obtained diffusion coefficient of hydrogen in titanium-hydride, 3.6 x 1 0' 15 m' 2 /s, was slightly larger than the value obtained by internal friction at room temperature.

In order to find the possible role of intracellular contents in facilitating the supercooling capability of xylem parenchyma cells, changes in the temperature of supercooling levels were compared before and after the release of intracellular substances from beech xylem parenchyma cells by DTA. Various methods were employed to release intracellular substances from xylem parenchyma cells and all resulted in a reduction of supercooling ability. It was concluded that the reduction of supercooling ability primarily resulted from changes of intracellular conditions, including the release of intracellular contents or their mixing with extracellular solutions, rather than due to changes of cell wall structures. It is therefore suggested that any unidentified intracellular contents may function to facilitate supercooling capability in xylem parenchyma cells.

Boreal hardwood species, including Japanese white birch (Betula platyphylla Sukat. var. japonica Hara), Japanese chestnut (Castanea crenata Sieb. et Zucc.), katsura tree (Cercidiphyllum japonicum Sieb. et Zucc.), Siebold’s beech (Fagus crenata Blume), mulberry (Morus bombycis Koidz.), and Japanese rowan (Sorbus commixta Hedl.), had xylem parenchyma cells (XPCs) that adapt to subfreezing temperatures by deep supercooling. Crude extracts from xylem in all these trees were found to have anti-ice nucleation activity that promoted supercooling capability of water as measured by a droplet freezing assay. The magnitude of increase in supercooling capability of water droplets in the presence of ice-nucleation bacteria, Erwinia ananas, was higher in the ranges from 0.1 to 1.7°C on addition of crude xylem extracts than freezing temperature of water droplets on addition of glucose in the same concentration (100mosmol/kg). Crude xylem extracts from C. japonicum provided the highest supercooling capability of water droplets. Our additional examination showed that crude xylem extracts from C. japonicum exhibited anti-ice nucleation activity toward water droplets containing a variety of heterogeneous ice nucleators, including ice-nucleation bacteria, not only E. ananas but also Pseudomonas syringae (NBRC3310) or Xanthomonas campestris, silver iodide or airborne impurities. However, crude xylem extracts from C. japonicum did not affect homogeneous ice nucleation temperature as analyzed by emulsified micro-water droplets. The possible role of such anti-ice nucleation activity in crude xylem extracts in deep supercooling of XPCs is discussed.

Lattice imperfections in (111)-oriented ZnTe wafers were characterized by means of X-ray Laue topography using the tomographic technique. The specimens were grown by the vertical gradient freezing Bridgman (VGFB) method. Specimens were set for Bragg diffraction (transmission case) associated with the reciprocal-lattice vector g and were mounted such that they could be rotated around g by means of a rotation stage (ω). White X-ray topographs of the 20-2 spot were taken at rotation angles of ω=0°, ±10°, ±20°, ±30°. We observed a number of twins in spite of the nearly perfect ZnTe crystal with a low dislocation density. The stacking fault energy of ZnTe was found to be lower than for other compound semiconductors.

Mosses are known to have the ability to develop high degrees of resistance to desiccation and freezing stress at cellular levels. However, underlying cellular mechanisms leading to the development of stress resistance in mosses are not understood. We previously showed that freezing tolerance in protonema cells of the moss Physcomitrella patens was rapidly increased by exogenous application of the stress hormone abscisic acid (ABA) [Minami, A., Nagao, M., Arakawa, K., Fujikawa, S., Takezawa, D., 2003a. Abscisic acid-induced freezing tolerance in the moss Physcomitrella patens is accompanied by increased expression of stress-related genes. J. Plant Physiol. 160, 475–483]. Herein it is shown that protonema cells with acquired freezing tolerance specifically accumulate low-molecular-weight soluble sugars. Analysis of the most abundant trisaccharide revealed that the cells accumulated theanderose (G6-α-glucosyl sucrose) in close association with enhancement of freezing tolerance by ABA treatment. The accumulation of theanderose was inhibited by cycloheximide, an inhibitor of nuclear-encoded protein synthesis, coinciding with a remarkable decrease in freezing tolerance. Furthermore, theanderose accumulation was promoted by cold acclimation and treatment with hyperosmotic solutes, both of which had been shown to enhance cellular freezing tolerance. These results reveal a novel role for theanderose, whose biological function has been obscure, in high freezing tolerance in moss cells.

Refraction-enhanced X-ray imaging method using extremely parallel X-ray beams from a so-called third generation synchrotron radiation source was applied to observe titanium-hydride in titanium polycrystals and titanium-aluminide. Hydride in titanium was formed by an annealing in 1 atm hydrogen gas and electrolytic-charging for cross-sectional observation. Although the hydride in titanium cannot be observed by conventional radiography that utilizes absorption of X-rays, we visualized a high-contrast projection image of hydride using refraction-contrast radiography. This is a promising new technique for non-destructive inspection in bulk material systems with only small differences between refraction indexes such as hydride in titanium.

The vacancy generation mechanism at high temperatures in ultrahigh-purity (7-N) aluminum single crystals with a low dislocation density was investigated by synchrotron radiation topography using a white X-ray beam. The specimens were prepared in vacuum using a strain-annealing method from zone-refined aluminum (1×105 residual resistance ratio). The dislocation density of the specimens was decreased to 1×103cm−2 by cyclic annealing. Straight lines were observed in the topographs taken after a temperature rise from room temperature to 300°C, and were confirmed to be rows of successive small interstitial-type dislocation loops grown as vacancy sources. It was concluded that the thermal generation mechanism of vacancies in ultrahigh-purity aluminum single crystals with a low dislocation density consists of two steps. First, small interstitial loops are heterogeneously formed in the crystal lattice. Second, these convert to lengthened loops with the development of screw components and finally grow into rows of dislocation loops emitting vacancies into the lattice through parallel helical dislocations.