LNLS, Campinas, Brazil
UNICAMP, Campinas, São Paulo, Brazil
LNLS, Campinas, Brazil
At Sirius, many of the optical elements such as mirror systems, monochromators, sample holders and detectors are attached to the ground with high stiffnesses to reduce disturbances at the beam during experiments. Granite benches were developed to couple the optical device to the floor and allow automatic movements, via com-manded setpoints on EPICS that runs an embedded kinematics, during base installation, alignment, commis-sioning and operation of the beamline. They are com-posed by stages and each application has its own geome-try, a set number of Degrees-of-Freedom (DoF) and mo-tors, all controlled by Omron Delta Tau Power Brick LV. In particular, the mirror system was the precursor motion control system for other benches. Since the me-chanical design aims on stiffness, the axes of mirror are not controlled directly, the actuators are along the granite bench. A geometric model was created to simplify the mirror operation, which turn the actuators motion trans-parent to the user and allow him to directly control the mirror axes.
LNLS, Campinas, Brazil
The Kirkpatrick-Baez (KB) mirror system is composed of a vertical focusing mirror (VFM) and a horizontal fo-cusing mirror. Both concave mirrors focus the X-ray beam by reflecting it at small grazing angles. The relocation of this system from UVX XDS beamline to Sirius EMA beamline facilitated a full revision of the motion control system, whose controller was migrated to Omron Delta Tau Power Brick LV. The beam focus is controlled by bending the mirrors through camshaft mechanisms cou-pled to low current Faulhaber motors. Although the am-plifier is designed for higher currents, controller settings allowed the use of lower currents. Another improvement made is the ability to drive both bender motors in gantry mode and still control the lag between them. Each bender has a capacitive sensor to monitor the position of the center of the mirror, which is read by the analog input of the controller and made available by EPICS [1]. The VFM is supported by a tripod and a new kinematics was devel-oped to reference the center of the mirror as the point of control. This paper presents the implementation of the new motion control KB system and its results at Sirius EMA beamline.
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
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 fly-scans. After the initial work in Speedgoat’s xPC rapid prototyping platform, for beamline operation the instrument controller was deployed to NI’s CompactRIO (cRIO), as a rugged platform combining FPGA and real-time capabilities. Customized libraries needed to be developed in LabVIEW and a heavily FPGA-based control architecture was required to finally reach a 20 kHz control loop rate. This work summarizes the final control architecture of the HD-DCM, highlighting the main hardware and software challenges; describes its integration with the EPICS control system and user interfaces; and discusses its integration with an undulator source.
*Geraldes, R. R., et al. "The status of the new High-Dynamic DCM for Sirius." Proc. MEDSI 2018 (2018).
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
TARUMÃ is the sub-microprobe station of the CARNAÚBA beamline at Sirius/LNLS*. Covering the range from 2.05 to 15keV, the probe consists of a fully-coherent monochromatic beam varying from 550 to 120nm with flux of up to 1e11ph/s/100mA after the achromatic focusing optics. Hence, positioning requirements span from nanometer-level errors for high-resolution experiments to fast continuous trajectories for high throughput, whereas a large flexibility is required for different sample setups and simultaneous multi-technique X-ray analyses, including tomography. To achieve this, the overall architecture of the station relies on a pragmatic sample positioning solution, with a rotation stage with a range of 220°, coarse stages for sub-micrometer resolution in a range of 20mm in XYZ and a fine piezo stage for nanometer resolution in a range of 0.3mm in XYZ. Typical scans consist of continuous raster 2D trajectories perpendicularly to the beam, over ranges that vary from tens to hundreds of micrometers, with acquisition times in range of milliseconds. Positioning is based on 4th order trajectories and feedforward, triggering includes the multiple detectors and data storage is addressed
* Geraldes, R.R., et al. ’Design and Commissioning of the TARUMÃ Station at the CARNAÚBA Beamline at Sirius/LNLS’ Proc. MEDSI20 (2020).
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.
LNLS, Campinas, Brazil
* D. Alnajjar, G. S. Fedel, and J. R. Piton, "Project Nheengatu: EPICS support for CompactRIO FPGA and LabVIEW-RT", ICALEPCS’19, New York, NY, USA, Oct. 2019, paper WEMPL002.