Key Performance

Overview

After the beam is exit from the sawtooth wall, a white light slit is set to limit the divergence angle of the beam incident on the monochromator. It is then collimated by a front-end mirror, with a source divergence angle of 30-40 μrad. A liquid-nitrogen-cooled double-crystal monochromator is placed 43 m away from the source point, where the full width at half maximum (FWHM) beam size at the monochromator position is approximately 1.5 mm. The double-crystal monochromator uses Si(111) crystals to meet the requirements for the energy range and energy resolution. To cover the K-absorption edge of phosphorus, the energy range is selected from 2.1 to 10.0 keV. An offset of 20 mm is chosen. Finally, two vertically and horizontally arranged cylindrical mirrors focus the beam at the exit slit2 to generate a secondary source point. The focused beam exhibits nearly equal divergence in the horizontal and vertical directions, forming a defined illumination spot at the entrance of the optical components in the experimental endstation.