Use of simultaneous reflections for precise absolute energy calibration of x rays

An experimental study of intensity variations in a synchrotron x‐ray beam caused by the presence of simultaneous reflections in the silicon monochromator crystals has been compared with calculations based on dynamical diffraction theory in an effort to determine the practical limits to the use of such intensity variations for energy calibration. It has been found that relative misalignments of the monochromator crystals can lead to errors of approximately 0.01% (1 eV at 10 keV), but that with some care energy calibration to within 0.002% (0.2 eV at 10 keV) can be achieved in a short measurement.