An X-ray topographic camera in the high-speed X-ray topographic
station (BL-15B) at the Photon Factory, High Energy Accelerator Research
Organization was improved for continuous observation with nuclear plates.
Using this camera, several topographs were taken during heating process of
nearly-perfect aluminum single crystals. As a result, an obscure topograph,
in which not only defect images but also fringe are unclear, was taken in
spite of very short exposure time (2.0 s) just prior to the appearance of
interstitial-type dislocation loops grown as vacancy sources.
The dislocation loops grown as vacancy source after up-quenching in 99.9999 % aluminum single crystals with a low dislocation density were examined by synchrotron topography in order to determine the Burgers vector and the nature directly. The specimen crystal was heated to 295°C and hold for 15min. at the temperature, then cooled down to room temperature to freeze the loops in the specimen. Topographs were taken on the high-speed X-ray topographic station (BL-15B) at the Photon Factory (KEK-PF). White beam topographs were taken using four of symmetrically equivalent 111 and 220 reflections for the determination of the Burgers vector. Monochromatic section topographs were also taken with 111, 222, 333 and 444 reflections at a wavelength of 0.62Å. The image of the loops was simulated by numerical solution of the Takagi-Taupin equations. Burgers vector of the frozen loops was determined to be a/2<110>. And comparison between the observed loop image and the simulated one showed that the dislocation loop grown as a vacancy source was interstitial-type and the size ranged from 3 µ m to 10 µ m in radius.
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