Hiroo Hashizume

Design of small-angle X-ray diffractometer using synchrotron radiation at the photon factory

Abstract A demagnifying focusing mirror-monochromator optics has been designed and constructed for time-resolved X-ray diffraction studies of biological substances. Focusing in the vertical plane is performed by a sequence of seven 20 cm long bent mirrors. Focusing in the horizontal plane is performed by a bent triangular silicon crystal monochromator which is placed downstream of the mirror. Phase space calculations predict that the optics should produce a focus 1.0 mm (V)×2.6 mm (H) (4σ-value) at the focus point. When the PF storage ring operates at 2.5 GeV and 0.5 A, the intensity is expected to be 10 11 –10 12 photons/s. A small-angle resolution of better than 1000 A should be obtainable at 1.5 A wavelength with an angular resolution of 0.8 mrad and 0.6 mrad in the vertical and horizontal directions, respectively.

X-Ray Diffraction Topography Utilizing Double-Crystal Arrangement of (+, +) or Non-Parallel (+, -) Setting

A potential utility of the double-crystal arrangement of (+, +) or non-parallel (+, -) setting for obtaining a diffraction topograph is studied. The method is simple in mechanism and enables us to obtain well-defined images of imperfections from a large area of a specimen without any scanning mechanism in a rather short exposure time. Differing from the double-crystal arrangement of the parallel setting usually used, the present method allows us to obtain topographs for any reflection of any kinds of crystals irrespectively of the first crystal. For the first crystal is employed the asymmetric 111 reflection of a nearly perfect Ge crystal to take photographs from a large area in a rather short exposure time by using a usual sealed-off X-ray tube. As examples are shown some transmission topographs taken with Cubα1 from a LiF crystal, and Si web crystals as grown and after heat-treated.

Backreflection x‐ray standing waves and crystal truncation rods as structure probe for epilayer–substrate systems

Backreflection x‐ray standing waves (BRXSW) and crystal truncation rod (CTR) scatterings have been used to probe the structure of heteroepitaxial CaSrF2 crystals on GaAs(111)B substrate. Coupled with the film‐thickness information obtained from x‐ray Fresnel reflectivity data, the combined x‐ray standing wave and BRXSW data suggest one or both of the F and As layers missing from the heteroepitaxial interface. The CTR data support a missing F layer and interface (Ca, Sr) atoms occupying the T sites on GaAs(111) surface.

Surface and interface structures of S‐passivated GaAs(111) studied by soft x‐ray standing waves

Surface and interface structures of S‐passivated GaAs(111)A and (111)B with and without CaF2 overlayers have been investigated using the soft x‐ray standing‐wave technique. On the GaAs(111)A surface S atoms are located on top of the first layer Ga atoms, while on the GaAs(111)B surface S atoms replace the first layer As atoms. This is in agreement with the photoemission results. It is found that CaF2 deposition and post‐annealing does not change the position of S atoms. A well‐ordered S structure for S/GaAs(111)B is maintained, indicating a high stability of S—Ga bonds. This is in contrast to the low coherent fraction for the S interlayer atoms observed from the CaF2/S/GaAs(111)A system.

A high-speed X-ray topography camera for use with synchrotron radiation at the photon factory

Abstract A detailed description of the high-speed X-ray topography camera designed for the vertical wiggler beam line at the Photon Factory is presented. The camera has been successfully operated with a white beam from a normal dipole magnet beam line since June 1982. The flexibility of the camera is sufficiently large to meet various user requirements. Some of its characteristic features are as follows: it has two TV detector arms providing a view coverage of 50° upwards and 30° downwards from the horizontal plane. The goniometer can support a load of 30 kg, to mount specimen environmental conditioners such as magnets and cryostats, while it can rotate with a precision of 2″ of arc over a full circle. The entire camera is placed on a special movable carriage to enable a simple and rapid interchange between a white beam outlet and a monochromatic one. Some 20 different samples and more than 20 people were involved both in commissioning the instrument and in the preliminary experiments, using about 900 h of machine time.

Determination of structure and formation kinetics of early stage gp zones in an al-1.7 at.% Cu alloy by small-angle X-ray scattering of synchrotron radiation

Abstract The structure and formation kinetics of GP zones in an Al-1.7 at.% Cu alloy during aging at 298 K were investigated by the small-angle X-ray scattering technique of synchrotron radiation. It was found that the zones are formed as platelets even in the quite early stages of aging. Analysis of scattered intensities was made on the basis of a structural model of single-layered disk-shaped GP zones distributed homogeneously on the three equivalent {100} planes of the matrix; this gave the diameter, integrated intensity and interparticle distance of the zones. The fast reaction and subsequent slow reaction processes were clearly observed in the changes of both the diameters and integrated intensities. The aging time ( t A ) dependence of the accompanying kinetics was well described by a common form, [( Kt A ) n + b ] −1 , where n = 1.47 for the diameter change and n = 0.97 for the integrated intensity change. The inter-particle distance increased monotonically from the early stages of aging, suggesting that the density of GP zones decreased from the initial stages by the competitive growth among zones.

X-Ray Diffraction Profiles for Near 180° Scattering from Mosaic Crystals

Reflectivity curves have been calculated for mosaic crystals in the case of normal-incidence Bragg diffraction with soft X-rays. The enormously broadened angular width of a reflection when the angle of incidence to the reflecting Bragg plane approaches 90° allows a single crystal with a mosaic spread as much as a few degrees to give a reflectivity profile very similar to that of a perfect crystal, when the incident photon energy is scanned. The insensitivity of the diffraction process to crystal mosaicity can be exploited in standing-wave experiments aimed at the determination of substrate-overlayer interface structures.

Dynamical structure change during reversion in AlZn binary alloy

Abstract To give information on the dynamical property of reversion phenomena in Al-Zn alloy, time-resolved small-angle X-ray scatterings have been measured using synchroton radiation. The time-dependent dissolution rate of G.P. zones is well described by the Johnson-Mehl-Avrami equation. The experimental time-exponent and temperature-dependent relaxation time deviate largely from expectations, suggesting that the reversion process is not controlled by the diffusion of solute atoms in the matrix. It has been found that Guinier radius increases slightly during reversion.

High-resolution mapping of two-dimensional lattice distortions in ion-implanted crystals from X-ray diffractometry data

The triple-crystal synchrotron X-ray diffractometry data described by Nikulin, Stevenson, Hashizume, Wilkins, Cookson, Foran & Garrett [J. Appl. Cryst. (1995), 28, 57–60] has been analyzed to map out two-dimensional (two-dimensional) lattice distortions in silicon (111) crystals implanted with B+ ions of 100 keV energy through a periodic SiO2 strip pattern. The lateral periodic structure produced a series of satellite reflections associated with the 111 Bragg peak. The 2D reconstruction incorporates the use of the Petrashen–Chukhovskii method, which retrieves the phases of the Bragg waves for these satellite reflections, together with that for the fundamental. The finite Fourier series is then synthesized with the relative phases determined. Localized distortions perpendicular to the surface arising from deposited B+ ions in near-surface layers of the crystal are clearly displayed with spatial resolutions of 0.016 and 0.265 μm in the depth and lateral directions, respectively. For a sample with the oxide layer removed from the surface, two equally plausible strain maps have been obtained by assigning relative phases to 11 satellites using a sequential trial method and a minimum-energy method. Failed map reconstructions for the oxide-covered sample are discussed in terms of the non-unique solutions of the Petrashen–Chukhovskii phase-recovery algorithm and the ambiguous phases determined for the satellites.

High-count rate position-sensitive detectors for synchrotron radiation experiments

Abstract This paper describes several X-ray position-sensitive detectors developed for use in high-count rate experiments at synchrotron radiation sources; (1) a charge-integrating position-sensitive proportional counter, (2) an amorphous silicon photodiode array as an X-ray PSD, (3) a MWPC with a multiple delay-line encoder and (4) a MWPC with carbon-fiber anode wires. The performance of the detectors is demonstrated in two examples of the application: a time-resolved measurement of a kinetic diffraction diagram from contracting muscle and a two-dimensional diffraction measurement of a powder crystal are presented.