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Gadolinium absorption gratings are critically important devices for grating-based neutron dark-field and phase-contrast imaging. The evaporation process is an excellent candidate for preparing Gd gratings large enough for imaging applications. However, there is some concern about the lower average density of obliquely evaporated Gd, which sometimes grows with many voids that are caused by shadowing effects. We have fabricated Gd gratings with 9-µm and 4-µm pitches as part of our design and measured the density distributions of the resulting Gd deposits by three-dimensional X-ray microtomography. The obtained tomographic image data is helpful not only for fabrication process design but also estimating device performance without performing neutron irradiation experiments.

In order to evaluate residual the stress distribution in oxides formed on zirconium alloys, synchrotron X-ray diffraction (XRD) was performed on the oxides formed on Zircaloy-2 after autoclave treatment at a temperature of 360° C in pure water. The use of a micro-beam XRD and a micro-sized cross-sectional sample achieved the detailed local characterization of the oxides. The oxide microstructure was observed by TEM following the micro-beam XRD measurements. The residual compressive stress increased in the vicinity of the oxide/metal interface of the pre-transition oxide. Highly oriented columnar grains of a monoclinic phase were observed in that region. Furthermore, at the interface of the post-first transition oxide, there was only a small increase in the residual compressive stress and the columnar grains had a more random orientation. The volume fraction of the tetragonal phase increased with the residual compressive stress. The results are discussed in terms of the formation and transition of the protective oxide.

Tomographic quantitative phase measurement has been carried out by using a hard X-ray micro-interferometer in Hyogo-ID at SPring-8. The micro-interferometer combines an imaging microscope and a wavefront-division-type interferometer by using a novel optical element called a “twin zone plate.” A three-dimensional quantitative phase distribution of a glass capillary with an outer diameter of 6 μm was successfully obtained with the tomographic technique. The measured refractive index corresponded to the ideal value. The spatial resolution of the tomographic image was estimated to be 250 nm and the density resolution was estimated to be 0.6 g/cm 3 .

A multilayer (sputtered-sliced) Fresnel zone plate (FZP) is one of the promising focusing optics with high spatial resolution for the high-energy X-ray region. This is because a large “aspect ratio” can be realized easily. In addition, it is important that the kinoform FZP (theoretical diffraction efficiency=100%) can be fabricated by the sputtered-sliced method. This paper presents the experimental results of two new approaches for fabrication of a multilayer FZP for X-rays. (1) To achieve higher diffraction efficiency, a multilevel-type (4-step: quasi-kinoform type) FZP was fabricated. This FZP was composed of concentric multilayers of alternating high-Z, low-Z, and composite materials. The composite material layer was deposited by co-sputtering of high-Z and low-Z materials. (2) To achieve smoother zones (multilayer interfaces) at the conventional-type FZP, each target of a sputtering apparatus with two DC-sputtering guns was surrounded by a cover with an aperture, and Ar gas was supplied inside the cover, which led to the deposition at lower Ar gas pressure. As a result, for the former, the efficiency was improved markedly as compared with conventional FZP, and for the latter, the zone roughness was reduced, which has resulted in the improvement of the spatial resolution of the FZP.

Three new types of optical elements for the synchrotron radiation (SR) high-brilliance X-ray beamlines have been developed: (1) a spatial resolution test pattern for X-ray computed tomography (CT), (2) a spatial resolution test pattern for X-ray scanning microscopy, and (3) a condenser device for X-ray imaging microscopy. These optical elements are composed of concentric multilayers of alternating high-Z and low-Z material deposited on a wire substrate. The characteristics of these elements have been tested at the SR facilities of Super Photon ring-8 GeV.Optical element (1) yielded a pattern of alternating opaque and transparent concentric rings with a film thickness of 1 μm. For (2), the test pattern was shown to work well in the high-energy X-ray region at 28 keV.Use of the condenser device with optical element (3) produced an absorption contrast image of a test pattern without modulation by the coherence of the source. These optical elements may play important roles in the future development of various analytical areas with high spatial resolution in the high-energy X-ray region at the SR high-brilliance X-ray beamlines.

A hard X-ray microbeam is a key technology for third-generation high-brilliance synchrotron radiation sources such as SPring-8. A Fresnel zone plate (FZP) is one of the promising focusing elements for X-rays. A multilayer (sputtered–sliced) FZP is suitable for use in hard X-ray region, because large thickness can be available. Zone (multilayer interface) roughness is inevitable to the multilayer FZP, which results in the inferior-focusing characteristic. Some Cu/Al concentric multilayers were fabricated by DC sputtering deposition. In order to reduce the oblique incidence of sputtered atoms on the wire substrate, a cylindrical slit was placed between the target and the wire substrate. As a result, the interface roughness was improved with very good repeatability.

An X-ray fluorescence imaging microscope with a Wolter-type grazing-incidence mirror objective was constructed at beamline 39XU of SPring-8. Monochromatic X-rays in the energy range 6–10 keV were used for X-ray fluorescence excitation of the specimens. Recording X-ray fluorescence images of a test specimen (Cu, Ni and Fe wires) from 50 different angles of view, three-dimensional tomographic reconstructions were obtained. These wires could be reconstructed selectively by changing the energy of the excitation X-rays. A synthetic diamond could also be imaged three-dimensionally.

X-ray imaging microscopy with a sputtered-sliced Fresnel zone plate (SS-FZP) has been developed at an X-ray energy of 25keV. Objects were imaged in transmission with the SS-FZP as an objective with a magnification of 10.2 times, and detected with a X-ray image sensor. The performance of the imaging microscope has been tested with a gold mesh and a resolution test pattern at an undulator beamline 47XU of SPring-8. The resolution test patterns up to 0.5mm line-and-space structures have been resolved. # 2001 Elsevier Science B.V. All rights reserved.

In our previous papers we reported that La 3+ , Gd 3+ , Y 3+ , and Lu 3+ dopings significantly improve the optical and scintillation characteristics, including radiation hardness, of PbWO 4 single crystals. The hypothesis of Pb 2+ deficiency in the grown crystals and its charge compensation by the mentioned trivalent ions occupying the Pb 2+ sites has been proposed to explain the observed improvement. Under such assumption, tetravalent-ion doping may be as efficient as or even more efficient than trivalent-ion doping in improving PbWO 4 scintillator. Recently we extended the dopant ions to stable tetravalent ions (Th 4+ , Zr 4+ ) and some other ions (Ce 3+,4+ , Sb 3+,5+ , Mn 2+ ). We have found that the tetravalent-ion (Th 4+ ) doping gives similar improvement compared with the trivalent-ion doping in consistency with the expectation mentioned above. The ions with two different possible charge states (Ce 3+,4+ , Sb 3+,5+ ) gave finite but much less improvement than the trivalent and tetravalent ions. Ce 3+,4+ doping reduced the light yield significantly. Annealing of undoped PWO in PbO vapour was also studied to examine the possibility of reducing the Pb 2+ deficiency

Doping by different trivalent ions (La3+, Lu3+, Gd3+, Y3+, Sc3+) was systematically studied in PbWO4 crystals in the same way, using raw material from the same source. The result was compared with an undoped sample (actually a Pb-rich one) and samples doped with divalent (Cd2+) and pentavalent (Nb5+) ions. All the trivalent ions but Sc3+ gave a significant improvement in transmittance in the short wavelength region (330–450 nm) and in radiation hardness. Among all the tested dopants, Y3+ and Gd3+ showed the best result; these dopants may be worth further studies, since they have another advantage of the segregation coefficient close to unity.

In this paper we report the crystal growth of lead tungstate crystals by the vertical Bridgman method with a flat-bottom crucible. The crystals were grown with different melt compositions. Other parameters such as effect of crucible thickness and growth orientation were also studied. Measurement of lattice parameters and phase analysis was carried out by X-ray diffraction method at different stages of crystallization and the region of congruent composition is investigated. Electron probe micro analyzer was used to image the eutectic flux mixture at the end of crystallization. It is concluded that the stoichiometric composition of PbWO 4 is congruent.

We have investigated applications of cerium-doped GSO (Gd2SiO5:Ce or GSO:Ce) scintillating crystals to high-precision electromagnetic calorimeters in high-energy physics experiments. Basic properties of GSO:Ce such as the decay time, light yield and radiation hardness were measured using small ( ∼ 4 cm long) sample crystals. The radiation hardness tests include the scintillator stability under 60Co exposure. The characteristics of the observed residual phosphorescence due to radiation were studied in detail. These properties are dependent on the Ce concentration. Between the two concentrations we tested, 0.5 and 1.5 mol%, GSO:Ce scintillator with 1.5 mol% Ce is better in various aspects. Recently, large ingots with 1.5 mol% Ce concentration have been grown successfully. We report optical properties of 2.5 × 2.5 × 26 cm3 crystals. We discuss the feasibility of GSO:Ce scintillator-based calorimeters in operating under high radiation such as at future hadron collider experiments.

A high spatial resolution X-ray microscope was constructed using an X-ray refractive lens as an objective. The spatial resolution was tested using 18 keV X-ray. A 0.4 mm line and 0.4 mm space tantalum test pattern was successfully resolved. Using the similar setup with the addition of a phase plate, a Zernike type phase-contrast microscopy experiment was carried out for the phase retrieval of the samples. Two-dimensional phase-contrast images were successfully taken for the first time in the hard X-ray region. Images of a gold mesh sample were analyzed and the validity of this method was indicated. An improvement of the lens, however, is required for the precise phase retrieval of the samples. # 2001 Elsevier Science B.V. All rights reserved.

A hard X-ray microbeam created from a sputtered-sliced Fresnel zone plate has been tested at SPring-8 undulator beamline. Focusing properties are evaluated in the X-ray wavelength regions of 0.15– 1.5 A . The measured focal beam size is about 0.6 μm at an X-ray wavelength of 1.4 A . In a scanning microscopy experiment, resolution-test-patterns with 0.2 μm structure are resolved at an X-ray wavelength of 0.45 A .