Researchers at the European XFEL have developed a new device for X-ray measurements at high photon energies–a so-called Laue spectrometer. It enables X-ray light with photon energies of over 15 kiloelectronvolts to be detected with improved efficiency and highest precision. This is important for researching technically significant materials that, for example, transport electricity without losses or ensure that chemical processes run more efficiently.
To unravel the secrets of the world of atoms, molecules and materials in general, scientists often use special measurement devices known as spectrometers. They work by recording the light that objects emit. From the way in which the objects do that, researchers learn a lot about the physical processes that take place in the materials. Particularly revealing is the research with X-ray light, which penetrates deeply in matter and provides information specific to each atomic species. This light is invisible to our eyes, but can be detected and measured using special spectrometers.
The main components of these devices are usually extremely precisely cut crystals made of silicon or germanium. Traditionally, the X-ray spectrometers work in what is known as Bragg geometry: The X-ray light hits the crystal and is then diffracted by the atomic planes parallel to the surface, similarly as mirrors reflect visible light. From the direction and intensity of the scattered radiation, the researchers can draw conclusions about the electronic properties of the materials they are analysing.
A unique characteristic of European XFEL is the ability to provide X-ray light with very high energy. However, as the energy of the X-rays increases, the interaction with the crystals becomes smaller, making the measurements challenging. In this high photon energy regime, a large proportion of the X-ray light simply passes through the crystal unused, which is why the performance of X-ray spectrometers using these analysers, known as Johann or Von Hamos spectrometers, decreases rapidly with increasing X-ray energy. They usually only work well up to a photon energy of around 15 kiloelectronvolts (keV).
Read more on European XFEL website
Image: Contrary to regular spectrometer the new Laue spectrometer is diffracting the X-ray beams (red arrows) by atomic layers perpendicular to the surface.