<title>X-ray flux concentrating optics for improving the performance of light element energy dispersive spectroscopy</title>

Abstract

Frequently, EDS (Energy Dispersive Spectrometer) x-ray detectors cannot be placed very close to an x-ray source for microanalysis causing the detector to subtend a small solid angle thus reducing the available count rate. This is exacerbated by low count rates for the light elements and situations where low energy spectral lines are immersed in a background of higher energy x-rays from heavier elements. Larger detectors can be used at the expense of resolution but in many situations there is insufficient room for a large detector so a 10 mm 2 detector is used. Notch filters can sometimes be used to minimize higher energy counts but they do not allow a broad spectrum of low energy x-rays to pass and still allow passage of the highest energy x-rays to the detriment of light element detection. We have developed low energy x-ray optics which increase the solid angle seen by EDS detectors and can also act as low pass filters preferentially allowing passage of low energy x-rays. In a typical situation where 10 mm 2 detectors are used with a 35 mm distance between x-ray source and detector surface, our optics can provide a flux gain of about 22X for B (Boron) x-rays with gain decreasing toward unity at energy above O (Oxygen at 525 eV) with gain remaining at unity for higher energy. In other words, we greatly increase the performance at the lowest energies without affecting the higher energies.