Sample‐angle feedback for diffraction anomalous fine‐structure spectroscopy

Diffraction anomalous fine‐structure (DAFS) experiments measure Bragg peak intensities as continuous functions of photon energy near a core‐level excitation. Measuring the integrated intensity at each energy makes the experiments prohibitively slow; however, in many cases DAFS can be collected quickly by measuring only the peak intensity at the center of the rocking curve. A piezoelectric‐actuator‐driven stage has been designed and tested as part of a sample‐angle feedback circuit for locking onto the maximum of the rocking curve while the energy is scanned. Although software peak‐tracking requires only a simple calculation of diffractometer angles, it is found that the additional hardware feedback dramatically improves the reproducibility of the data.