Example of strain scanning at 1-ID
In the photo below we show the setup used to map strain/stress as a function of depth in peened steel rods. The incident x-ray beam comes from the right in the photo and is ~20x20 square microns, and focused in the vertical direction using refractive lenses. The longitudinal gage length is confined to ~100 microns using a conical slit assembly between the sample and detector, thus creating a probe volume of ~ 20x20x100 cubic microns. X-rays are detected on a large area detector (Mar345 shown) to provide 2-dimensional strain information.
Since the strain state in this case is assumed to be axially symmetric, the rod is rotated about it's axial direction during data collection to improve grain averaging, with limited effect on spatial resolution. The sample is translated vertically, relative to the direct beam, to allow the depth-dependent internal strains to be mapped.
Photo showing setup for 3-d strain scanning of a shot-peened rod, courtesy of Greg Olson and Yana Qian at Northwestern University.