An improvement of spatial resolution of m-XRF by using a thin metal filter was investigated. The size of the x-ray beam focused by the polycapillary x-ray lens depended on the energy of the characteristic x-rays. Original spot sizes at the focal point were 48 µm for CrKa, 41 µm for NiKa, and 28 µm for MoKa, respectively. To make the x-ray beam size small, Ti-Cu thin foil was placed between the output of the lens and the focal point as a metal filter to reduce the continuous x-rays. Finally, the x-ray microbeam size was improved to 30 µm by applying a filter. Clear 2D mapping images of Cr, Fe, and Ni in 300-mesh stainless steel could be obtained by applying this filter.

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