Double Crystal Monochromator Control System for Energy Materials In-Situ Laboratory Berlin (EMIL)

A multi modal set-up provides synchrotron radiation with a broad energy range of 80 eV - 10 keV and variable polarization to the EMIL lab at BESSY II. Two canted undulators, five end stations, three monochromators, more than twenty optical elements, sample to source distances of more than 60 m are challenges by its own. The Double Crystal Monochromator (DCM) feeding the U17 hard X-ray beamlines was designed and optimized for stability and resolution. The mechanical concept of the U17/DCM puts high demands on the software. For on-the-fly synchronization of crystal pitch, crystal translation and the cryogenic cooling system rotation, a closed loop feedback is needed to fulfill the control system requirements. Motion programs are used for compensation of the non-linearities of the pitch rotation. Target positions are approached on a well defined path improving reproducibility and positioning time. A non-linear closed loop control provides fine positioning. A setup of the motion controller based on the tpmac module provides the abstraction interface to the complex DCM motion control software. This paper discusses the DCM hardware, the software model and experimental verification.
Proceedings of the 17th International Conference on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2019, New York, NY, USA