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The structure of the interstitially ordered lattice formed in zirconium-oxygen alloys has been studied with use of single-crystal data obtained by X-ray and neutron diffraction methods. The structure belongs to space group P312 and the lattice parameters a and c are related to a₀ and c₀ of the host hexagonal metal lattice by a = 3a₀ and c = c₀. The ordered arrangement of interstitial oxygen atoms is described as a regular stacking of layers parallel to the (00.1) plane with the sequence (AC)B(AC)B which is of the same type as that of nitrogen atoms in -Fe₂N. The occupancy probability of oxygen atoms is high for interstitial sites of the A and B types while it is low for sites of the C type. The host metal lattice is distorted in such a way that spacings of successive (00.2) planes are not the same and a hexagonal network of atoms in these planes is periodically deformed.

A new multipurpose X-ray small-angle scattering camera system consisting of a rotating-anode X-ray generator, a double-focusing collimator and a two-dimensional position-sensitive detector has been developed at the High-Intensity X-ray Laboratory of Kyoto University. The overall camera length is 6 m, and the sample-to-detector distance can be varied in 0.5 m increments up to 3 m to cover scattering angles ranging from 0.001 to 0.18 rad. The collimator consists of a pair of crossed-plane total-reflection mirrors of 40 cm in length. The mirrors, which are mechanically bent to form cylindrical surfaces, provide point collimation free of collimation error. General-purpose sample holders equipped with a programmable temperature controller are provided for both transmission and scattering measurements; the temperature is maintained within ± 0.1 K in the range of 223-573 K. A cryostat for measurements down to 20 K, a dynamic sample deformation apparatus, and a temperature-jump equipment are also available. The multi-wire delay-line position-sensitive proportional counter has an active area of 128 × 128 mm with a spatial resolution of 0.5 × 1.0 mm. The data acquisition is controlled by a real-time front-end processor through a CAMAC interface. The data are recorded in a dual-port histogramming memory of 32 bit × 1 Mwords, which enables direct access to the data from the main computer for real-time monitoring and analysis. The performance of the camera is demonstrated with some selected examples: diffraction patterns from carp lateral line nerve myelin and chicken-tendon collagen fibrils, a Guinier plot of the scattering from polystyrene in dilute solution, and time-resolved measurements of polypropylene during the annealing process.