The design and operation of a new small-angle X-ray scattering instrument, optimized for high throughput at a synchrotron source, high angular and wavelength resolution, large sample cross-sectional area, accurate energy tuning, excellent signal-to-noise ratio and harmonic rejection are presented. The principles of design and implementation are given, as are the details of primary calibration of absolute intensity and experimental desmearing. The instrument has been tested for application to anomalous-scattering measurements near the chromium K edge. Preliminary results on samples of a heat-treated steel are presented as a demonstration of the capability of this experiment to separate the microstructure evolution as a function of temperature of a chromium-rich precipitate from the thermal behavior of other precipitates in the steel.

Polycrystalline specimens of copper have been fatigued in reverse bending, in a vacuum at 405°C at a maximum strain amplitude of 0.044%. A specimen tested to 0.07% of its expected life gives neutron scattering which is isotropic and identical to that of an unfatigued specimen, and which can be attributed to surface oxides. A specimen fatigued to 25% of its expected life gives a larger scattering, which is anisotropic. This is attributed to faceted pores at grain boundaries resulting from the high-temperature fatigue. The quantitative results indicate the presence of pores smaller than those so far observed in the electron microscope.