Speaker
Description
During energy-dispersive X-ray diffraction, the sample is irradiated with a pencil beam generated by a standard polychromatic X-ray tube without any spectral filtering. Two-dimensional polychromatic diffraction images are acquired using a Timepix 3 quad CdTe detector with a central aperture to allow the pencil beam to pass through without parasitic interaction. The detector, equipped with a USB3 interface, has a throughput of up to 47 Mcts/s. For each detected photon, its position is known with an accuracy of 55 µm in the detector plane, and its energy with a resolution of 4 keV at 60 keV. The recorded polychromatic data are then converted into an equivalent monochromatic XRD pattern that would result from the use of a monochromatic X-ray source. For a detailed analysis of the XRD pattern, it was necessary to remove undesirable photons resulting from scattering and, above all, from internal XRF from the sensor material. It will be shown that the resulting XRD patterns reveal a wealth of information.
Thanks to the 160 kV voltage of the X-ray tube, the polychromatic narrow beam was able to pass through a highly attenuating sample of 1.5 mm thick steel sheet. By utilizing the entire X-ray spectrum, the beam has sufficiently high intensity to obtain XRD patterns quickly enough even when investigating relatively fast physical processes. It has been verified that a temporal resolution of 0.01 s can be achieved with this setup. This allows for the analysis of phase transitions in a polycrystalline sample during its heat treatment under standard laboratory conditions, which is otherwise only possible at synchrotron sources [1]. The ability to examine relatively large samples throughout their volume makes it possible to investigate other time-dependent phenomena that do not manifest themselves on the sample’s surface, such as changes in the lattice dimensions of steel due to hydrogen diffusion.
[1] Vavrik, D., Georgiev, V., Jakubek, J. et al. Sci Rep 15, 31752 (2025). https://doi.org/10.1038/s41598-025-16314-9
The institutional support of RVO68378297 is kindly acknowledged.