LNLS, Campinas, Brazil
The High-Dynamic Double-Crystal Monochromator (HD-DCM)*,** is an opto-mechatronic system with unique architecture, and deep paradigm changes as compared to traditional beamline monochromators. Aiming at unmatching scanning possibilities and positioning stability in vertical-bounce DCMs, it has been developed since 2015 for hard X-ray beamlines at Sirius Light Source at the Brazilian Synchrotron Light Laboratory (LNLS). Two units are currently operational at the MANACA (macromolecular crystallography) and the EMA (extreme conditions) undulator beamlines, whereas a model for extended scanning capabilities in the energy range between 3.1 to 43 keV, the so-called HD-DCM-Lite, is in advanced development stage for two new beamlines, namely: QUATI (quick absorption spectroscopy), with a bending-magnet source; and SAPUCAIA (small-angle scattering), with an undulator source. In this work, online commissioning and operating results of the HD-DCMs are presented with emphasis on: the 10 nrad RMS (1 Hz - 2.5 kHz) pitch-parallelism performance; energy calibration; energy-dependent beam motion at sample; and flyscan with monochromator-undulator synchronization, which is a well-known control challenge at beamlines. To conclude, the Sirius HD-DCM family prospects, including the HD-DCM-Lite, are discussed.
*Geraldes, R. R., et al. "The New High-dynamics DCM for Sirius." Proc. of MEDSI 2016.
**Geraldes, R. R., et al. "The Status of the New High-Dynamic DCM for Sirius." Proc. of MEDSI 2018.
LNLS, Campinas, Brazil
One of the challenges of fourth-generation synchrotron light sources as Sirius at the Brazilian Synchrotron Light Laboratory (LNLS) is the high power density that may affect the beamline optical elements by causing figure deformations that deteriorate the quality of the beam. Indeed, surface specifications for height errors of X-ray mirrors are often within a few nanometers. To deal with these thermal management challenges, thermo-mechanical designs based on cryogenic silicon have been developed, taking advantage of its high thermal conductance and low thermal expansion in temperatures of about 125 K. A liquid nitrogen (LN2) cryostat connected to the optics by copper braids has been used to handle moderate power loads, reducing costs when compared to closed-circuit LN2 cryocoolers and mechanically decoupling flow-induced vibrations from the optics. To guarantee the functionality of such systems, lumped mass thermal models were implemented together with auxiliary finite elements analyses. With the first systems in operation, it has been possible to compare and validate the developed models, and to carry out optimizations to improve them for future projects, by adjusting parameters such as emissivity, thermal contact resistance, and copper braid conductance. This work presents the updated models for CARNAÚBA and CATERETÊ beamlines as reference cases.