Characterization of polycapillary lenses to depth profiling analysis by confocal XRF

ROBERTO PÉREZ; V. SBARATO; HECTOR JORGE SANCHEZ; M. RUBIO; C. A. PÉREZ

Activity Report LNLS

LNLS, Brasil

Año: 2009 p. 1 - 2

1518-0204

Polycapillary optics has emerged in the last twenty yearsas a powerful tool for collimating and focusing x-rays [1]. Itcan provide an intense x-ray beam, which is highly collimatedwith a minimum of divergence. It can also produce small focusedx-ray spots of high intensity. Capillary optics is basedon transport of x-rays through glass capillaries by external totalreflection (TR) at the glass surfaces. Multiple reflectionsin the TR regime lead x-rays over large angles in the capillaries.In this way, intensity losses in the incident x-ray beamcan be kept small, even if the capillary is being bent over severaldegrees. Polycapillary optics consists of an array of largenumbers of curved glass capillaries to collect and steer x-rays.At the entrance of the device, the capillaries are oriented tocollect x-rays from a large area of the incident x-ray beam,while at the output the capillaries are oriented so as to producea high intensity x-ray beam. For focusing synchrotronradiation photons, capillaries are all parallel at the entranceand directed toward a common focal spot at the output. In thepresent work, the characterizations of two similar monolithicpolycapillaries were done. They were used to carry out confocalx-ray fluorescence microanalysis. In general, the confocalsetup is developed to analyze a small volume of sample.The probing volume is defined by the overlapping of the fociof two lenses, one in the excitation channel and the other inthe detection channel. The scanning of the probing volumeinside the sample allows the three dimensional analysis [2].In our confocal μXRF the incident x-ray beam pass througha polycapillary which focused it into a small volume sampleproducing x-ray fluorescence emission. A second polycapillaryguide the x-ray fluorescence emitted from the probingvolume to the detector. As an example, one dimensional scanningover several TEOM environmental filters was done todetermine the depth profiling of particulate matter. It is usefulto improve the precision of quantitative analysis of environmentalfilters by conventional XRF.