In-situ energy calibration of SSRF macromolecular crystallography beamline using powder diffraction

For X-ray powder diffraction spectra collected by an area detector of MarCCD on macromolecular crystallography beamline of SSRF, an energy calibration method was developed using LaB6(660a) powder diffraction for in-situ rapid energy calibration of the X-rays without changing the experimental conditions. The intensity of each diffraction ring was integrated, and the accurate peak positions were fitted by Pseudo-Voigt function model. The sample's interplanar spacing for XRD analysis and the calibrated energy were obtained by the PCPDFWIN code and by fitting all the energies with the least-square method. The exposure time and the sample-to-detector distance were found no effect on accuracy of the energy calibration, and the in-situ energy calibration could be done with an accuracy of better than 0.4‰ in 7-18 keV. This method is applicable to other X-ray beamlines.