X-rays (excitation radiation) are focused onto a sample through a polycapillary lens (a solid or a half-lens, depending on the X-ray source). The X-rays excite atoms, which then emit radiation characteristic of the element in question. This radiation is then transported to an energy dispersive detector using a second polycapillary (half) lens. The focal points of the two optics in the excitation and detection channels overlap to form the probe volume from which fluorescence and scattered radiation are obtained. By moving the sample into this probe volume, a 3D image of the elemental distribution of the sample can be obtained with a lateral and depth resolution of ~ 30 µm.
The technique is particularly suitable for low-density samples, since the depth of information must be large compared to the size of the probe volume to image 3D objects. The two main application areas to date are archaeometry and biology, both of which additionally benefit from the technique's non-destructive nature.
While the reconstruction of depth profile measurements has already been developed in our group, the current research goal is the quantification of complete 3D maps of heterogeneous material.