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X-Ray Microdiffraction at the Advanced Light Source

Experimental Techniques

When using an x-ray microbeam, rotation of the sample relative to the microbeam is not allowed. There are two critical problems associated with rotations and microbeams:

To avoid rotations, the sample is scanned beneath the incident x-ray microbeam within the focal plane. At each step in the scan, diffraction data can be collected via a CCD detector.

Either white beam or monochromatic beam can be used to perform a microdiffraction scan. White beam is used when the grain size of the material is greater than or about equal to the x-ray beam size. With white beam, data is collected as Laue patterns from any crystallites within the diffracting volume. Monochromatic beam is used when the grain size is much less than beam size. In this case, the sample can be viewed as a powder. Data is collected in the form of diffraction rings.