The mechatronic architecture and design of the High-Dynamic Double-Crystal Monochromator for Sirius light source

Abstract

The High-Dynamic Double-Crystal Monochromator (HD-DCM) has been in development since 2015 for X-ray beamlines of Sirius, the 4th-generation light source at the Brazilian Synchrotron Light Laboratory (LNLS). Being the first DCM to implement an isolated mechatronic architecture with high closed-loop performance, its development was based on predictive design via the Dynamic Error Budgeting (DEB) workflow to deliver positioning performance improvements by factors of 5 and 100 with respect to state-of-the-art DCMs, in fixed and scanning modes, respectively — which not only increases beam stability in conventional operation, but also enables unprecedented high-stability spectroscopy perspectives. After introducing the role of the instrument within the scope of X-ray beamlines, this paper discusses its innovative architecture through its detailed mechanical design. The achieved inter-crystal parallelism of 10 nrad RMS (1Hz-2.5 kHz) results from a systems approach, following strategic control-oriented design, thermo-mechanical decoupling, the minimization of moving degrees-of-freedom, disturbance management, including flow optimization and the selection of smooth force actuators, and the implementation of embedded short-loop high-accuracy metrology.