title: Polycapillary-optics-based micro-XANES and micro-EXAFS at a third-generation bending-magnet beamline.
abstract: A focusing system based on a polycapillary half-lens optic has been successfully tested for transmission and fluorescence micro-X-ray absorption spectroscopy at a third-generation bending-magnet beamline equipped with a non-fixed-exit Si(111) monochromator. The vertical positional variations of the X-ray beam owing to the use of a non-fixed-exit monochromator were shown to pose only a limited problem by using the polycapillary optic. The expected height variation for an EXAFS scan around the Fe K-edge is approximately 200 microm on the lens input side and this was reduced to approximately 1 microm for the focused beam. Beam sizes (FWHM) of 12-16 microm, transmission efficiencies of 25-45% and intensity gain factors, compared with the non-focused beam, of about 2000 were obtained in the 7-14 keV energy range for an incoming beam of 0.5 x 2 mm (vertical x horizontal). As a practical application, an As K-edge micro-XANES study of cucumber root and hypocotyl was performed to determine the As oxidation state in the different plant parts and to identify a possible metabolic conversion by the plant.
authors.affiliation: X-ray Microspectroscopy and Imaging Research Group (XMI), Department of Analytical Chemistry, Ghent University, Krijgslaan 281 S12, B-9000 Gent, Belgium. geert.silversmit@ugent.be
authors.forename: Geert
authors.initials: G
authors.lastname: Silversmit
authors.forename: Bart
authors.initials: B
authors.lastname: Vekemans
authors.forename: Sergey
authors.initials: S
authors.lastname: Nikitenko
authors.forename: Wim
authors.initials: W
authors.lastname: Bras
authors.forename: Viktoria
authors.initials: V
authors.lastname: Czhech
authors.forename: Gyula
authors.initials: G
authors.lastname: Zaray
authors.forename: Imre
authors.initials: I
authors.lastname: Szaloki
authors.forename: Laszlo
authors.initials: L
authors.lastname: Vincze
mesh_terms: D002197:Capillary Action; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses; D008280:Magnetics / Q000295:instrumentation*; D008904:Miniaturization; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013052:Spectrometry, X-Ray Emission / Q000295:instrumentation*; D017356:Synchrotrons / Q000295:instrumentation*