LNLS, Campinas, Brazil
CARNAÚBA (Coherent X-ray Nanoprobe) and CATERETÊ (Coherent and Time Resolved Scattering) are the longest beamlines in Sirius - the 4th generation light source at the Brazilian Synchrotron Light Laboratory (LNLS). They comprise Four-Bounce Crystal Monochromators (4CM) for energy selection with strict stability and performance requirements. The motion control architecture implemented for this class of instruments was based on Omron Delta Tau Power Brick LV, controller with PWM amplifier. The 4CM was in-house designed and consists of two channel-cut silicon crystals whose angular position is given by two direct-drive actuators. A linear actuator mounted between the crystals moves a diagnostic device and a mask used to obstruct spurious diffractions and reflections. The system is assembled in an ultra-high vacuum (UHV) chamber onto a motorized granite bench that permits the alignment and the operation with pink-beam. This work details the motion control approach for axes coordination and depicts how the implemented methods led to the achievement of the desired stability, considering the impact of current control, in addition to benchmarking with manufacturer solution.
LNLS, Campinas, Brazil
Precision beamline systems, such as monochromators and mirrors, as well as sample stages and sample holders, may require fine thermal management to meet performance targets. Regarding the optical elements, the main aspects of interest include substrate integrity, in case of high power loads and densities; wavefront preservation, due to thermal distortions of the optical surfaces; and beam stability, related to thermal drift. Concerning the sample, nanometer positioning control, for example, may be affected by thermal drifts and the power management of some electrical elements. This work presents the temperature control architecture developed in house for precision elements at the first beamlines of Sirius, the 4th-generation light source at the Brazilian Synchrotron Light Laboratory (LNLS). Taking some optical components as case studies, the predictive thermal-model-based approach, the system identification techniques, the controller design workflow and the implementation in hardware are described, as well as the temperature stability results.
LNLS, Campinas, Brazil
The High-Dynamic Double-Crystal Monochromator (HD-DCM) has been developed since 2015 at Sirius/LNLS with an innovative high-bandwidth mechatronic architecture to reach the unprecedented target of 10 nrad RMS (1 Hz - 2.5 kHz) in crystals parallelism also during energy flyscans. Now, for beamlines requiring a smaller energy range (3.1 to 43 keV, as compared to 2.3 to 72 keV), there is the opportunity to adapt the existing design towards the so-called HD-DCM-Lite. The control architecture of the HD-DCM is kept, reaching a 20 kHz control rate in NI’s CompactRIO (cRIO). Yet, the smaller gap stroke between crystals allows for removing the long-stroke mechanism and reducing the main inertia by a factor 6, not only simplifying the dynamics of the system, but also enabling faster energy scans. With sinusoidal scans of hundreds of eV up to 20 Hz, this creates an unparalleled bridge between slow step-scan DCMs, and channel-cut quick-EXAFS monochromators. This work presents the dynamic error budgeting and scanning perspectives for the HD-DCM-Lite, including feedback controller design options via loop shaping, feedforward considerations, and leader-follower control strategies.