Abstract
BL13-XALOC is currently the only macromolecular crystallography beamline at the 3 GeV ALBA synchrotron near Barcelona, Spain. The optics design is based on an in-vacuum undulator, a Si(111) channel-cut crystal monochromator and a pair of KB mirrors. It allows three main operation modes: a focused configuration, where both mirrors can focus the beam at the sample position to 52 µm × 5.5 µm FWHM (H × V); a defocused configuration that can match the size of the beam to the dimensions of the crystals or to focus the beam at the detector; and an unfocused configuration, where one or both mirrors are removed from the photon beam path. To achieve a uniform defocused beam, the slope errors of the mirrors were reduced down to 55 nrad RMS by employing a novel method that has been developed at the ALBA high-accuracy metrology laboratory. Thorough commissioning with X-ray beam and user operation has demonstrated an excellent energy and spatial stability of the beamline. The end-station includes a high-accuracy single-axis diffractometer, a removable mini-kappa stage, an automated sample-mounting robot and a photon-counting detector that allows shutterless operation. The positioning tables of the diffractometer and the detector are based on a novel and highly stable design. This equipment, together with the operation flexibility of the beamline, allows a large variety of types of crystals to be tackled, from medium-sized crystals with large unit-cell parameters to microcrystals. Several examples of data collections measured during beamline commissioning are described. The beamline started user operation on 18 July 2012.
Highlights
ALBA is a third-generation synchrotron light source built in Barcelona, Spain, with a 268 m storage ring circumference, 3 GeV electron energy and 4.6 nm rad measured emittance, and has been routinely operating since 2011 (Einfeld, 2011)
The portfolio of the seven phase-I beamlines includes beamline BL13, called XALOC, that is dedicated to macromolecular crystallography (MX)
Other metrology tests show that the first resonance of the monochromator mechanics is well above 150 Hz, which is much higher than the frame rate of the main detector of the beamline (12 Hz)
Summary
ALBA is a third-generation synchrotron light source built in Barcelona, Spain, with a 268 m storage ring circumference, 3 GeV electron energy and 4.6 nm rad measured emittance, and has been routinely operating since 2011 (Einfeld, 2011). The combination of the high levels of stability and flexibility allows us to operate effortlessly the beamline in two main modes, letting the user choose either to focus or Undulator maximum magnetic field Undulator period Number of magnetic periods Photon source size Photon source divergence Undulator power at 250 mA in storage ring Monochromator type Energy range (wavelength range) Vertical focusing mirror (VFM). The optics of the beamline includes a single-crystal 200 mm-thick diamond Laue monochromator, which is designed to deliver a 9.041 keV X-ray beam to a future side branch. At this side branch the beam can be focused to 750 mm  550 mm FWHM (H  V) without any additional optics due to the focusing properties of the Laue diffraction (Sanchez del Rıo et al, 1995). Other metrology tests show that the first resonance of the monochromator mechanics is well above 150 Hz, which is much higher than the frame rate of the main detector of the beamline (12 Hz)
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