From Design to Validation: Performance of Novel Monochromators for the HEPS project

Abstract Monochromators are essential optics crucial to the performance of synchrotron beamlines. In the phase one project at the High Energy Photon Source (HEPS), 17 monochromators of different types will be utilized across 14 beamlines. 11 of them will be built in-house. The versatile and stringent requirements imposed on the monochromators present a formidable challenge and at the same time a demanding unparalleled effort. Our approach includes Finite Element Analysis (FEA) for modal analysis, laser interferometer metrology for stability and motion measurements, hammer test for modal determination and encoders for fast scanning capabilities. These methods combined with tests under varied cooling and environmental conditions allow for a comprehensive validation of their performances. Notably, the Vertical diffracting Double Crystal Monochromator (VDCM) developed for HEPS shows a stability below 10nrad (0.5-500Hz) with a LN2 flow rate of 2L/min. The Horizontal diffracting pseudo Channel-cut Crystal Monochromator (HCCM) shows a stability below 30nrad at LN2 pump speeds below 30Hz. Moreover, a Quick EXAFS Channel-cut Crystal Monochromator (QCCM) designed for fast scanning, shows a scan range of 0.8 degree at 100 spectra/s, which surpasses the requirements of the planned XAFS beamline. Additionally, a High Resolution Monochromator with a specially designed large range flexures, shows a resolution and stability below 10nrad. The test results of those in-house developed monochromators show that they meet the requirements of the HEPS beamlines.