External scanning micro-PIXE for the characterization of a polycapillary lens: Measurement of the collected X-ray intensity distribution

This work reports the results of the lens characterization in terms of X-ray collection spot, i.e. the area of the sample actually “seen” by the lens, and its dependence on the X-ray energy. The lens properties have been measured using the external scanning microbeam facility of the Tandetron accelerator at LABEC-INFN in Florence. The detection system was used to detect X-rays from a set of pure elemental standards with an incident 3 MeV proton beam focused to a size of about 30 μm scanning an area of 1.9 × 1.6 mm2. By measuring the spatial distribution of characteristic X-rays from each given material, the collection profile of the lens at the corresponding X-ray energy was obtained. Using several standards, the behaviour throughout the range 1-10 keV was examined. The sensitivity of the lens collection profile on the lens-sample out-of-focus distance was also investigated.