Characterization of a polycapillary lens for use in micro-XANES experiments

Polycapillary lenses permit x-rays to be focused down to relatively small (< 50 mum) beam diameters. A polycapillary device, suitable for focusing of synchrotron radiation, was characterized at beam line L of HASYLAB (Hamburg, Germany). Beam parameters such as beam size, transmission efficiency and gain in flux density were determined as a function of the energy-of the primary monochromatic beam entering the polycapillary. At a distance of 4 mm between the lens tip and the sample, the smallest beam diameters were recorded: 30 mum at 7 keV, decreasing to 8 mum at 21 keV. In the energy range from 7 to 15 keV, the transmission efficiency varied between 30 and 45%, while the maximum gain in flux density was calculated to be around 3500. When the energy was changed from 7 to 30 keV, a vertical translation of only 7-8 mum was observed, indicating that this optic is highly suitable for use in mu-XANES investigations. To illustrate this point, the investigation of paper corrosion due to iron gall inks and the speciation of Ni in environmental particles is described. Copyright (C) 2003 John Wiley Sons, Ltd.