RESUMEN
X-ray topography exerting the super-Borrmann effect has been performed using synchrotron radiation to display dislocation images with a high-speed and high-resolution CMOS camera. Forward-transmitted X-rays are positively employed instead of reflected X-rays to reveal dislocations in relatively thick crystals by simultaneously exciting a pair of adjacent {111} planes owing to the super-Borrmann effect. Before the experiment, minimum values of the attenuation coefficients AminP for σ and π polarizations of the incident X-rays in the three-beam case are calculated. Results demonstrate that AminP for both polarizations are almost 20 times larger than those in the two-beam (usual Borrmann effect) case. The transmitted X-rays can be used to confirm the efficacy of taking topographs under the super-Borrmann conditions, as well as under multiple-diffraction conditions. Furthermore, super-Borrmann topographs can be considered for relatively thick crystals, where a conventional Lang X-ray topography technique is difficult to apply.
RESUMEN
X-ray topographs are taken for a sapphire wafer with the [0001] surface normal, as an example, by forward transmitted synchrotron x-ray beams combined with two-dimensional electronic arrays in the x-ray detector having a spatial resolution of 1 µm. They exhibit no shape deformation and no position shift of the dislocation lines on the topographs. Since the topography is performed under multiple-beam diffraction conditions, the topographic images of a single diffraction (two-wave approximation condition) or plural diffractions (six-wave approximation condition) can be recorded without large specimen position changes. As usual Lang topographs, it is possible to determine the Burgers vector of each dislocation line. Because of high parallelism of the incoming x-rays and linear sensitivity of the electronic arrays to the incident x-rays, the present technique can be used to visualize individual dislocations in single crystals of the dislocation density as high as 1 × 10(5) cm(-2).
RESUMEN
For the energy region from tens to hundreds of electron volts, the multilayered mirror (MLM) monochromator has never been realized due to the difficulty of reducing the background noise of the total reflection component, in spite of its usefulness in synchrotron radiation experiments. In this work, a double-crystal-type MLM monochromator equipped with a thin-film filter has been designed on the basis of trial fabrication of the mirror-driving system and of Mo/Si and Mo/C MLMs; its performance has been evaluated by calculating its output photon flux. It is shown that by using the MLMs at low incident angles, combined with an appropriate thin-film filter, it is possible to make a practical monochromator with high output photon flux and low background noise.
RESUMEN
The x-ray properties of multinested thin-foil mirror x-ray telescopes (XRT's) on board ASCA, the Advanced Satellite for Cosmology and Astrophysics, were fully evaluated with an x-ray pencil beam.Scanning over the telescope aperture of 35 cm in diameter with an x-ray pencil beam, we found the effective area of a set of XRT's to be 325, 200, and 113 cm(2) at energies of 1.5, 4.5, and 8.0 keV, respectively. We derive the point-spread functions (PSF's) of the XRT's by measuring the image profile at the focal plane with an x-ray CCD. The PSF is found to exhibit a sharp core concentrated within 30 arcsec and a broad wing extended to 3 arcmin in half-power diameter. We also evaluate the contribution of stray light, which is caused by the single reflection of x rays by primary or secondary mirrors and by the backside reflection of the mirrors. To obtain the characteristics of the XRT in the energy region of 0.5-10.0 keV, incorporated with the measurements at discrete energies, we develop a ray-tracing method with the telescope design parameter, the PSF, and optical constants. In particular, we obtain the optical constants around the gold-atom M shell (Au-M) absorption-edge energies by measuring the reflectivity of our mirror sample, with monochromatized x-rays in the energy range of 2.0-3.5 keV from synchrotron radiation. Taking into account the PSF's and optical constants, we find that our ray-tracing program can reproduce all these XRT performances.