Better Bundled: New Principle For Generating X-Rays

Physicists from Göttingen are developing a method in which rays are generated and guided simultaneously through a "sandwich structure"

X-rays are mostly omnidirectional and difficult to guide. X-ray physicists at the University of Göttingen have developed a new method with which the X-rays can be emitted more precisely in one direction. To do this, the scientists use a structure of thin layers of materials with different electron densities in order to deflect and bundle the generated beams at the same time. The results of the study were published in the journal Science Advances .

For the generation of X-rays in ordinary X-ray tubes, electrons that have been accelerated by high voltage patter onto a metal anode. The atoms in the metal divert and slow down the electrons in their "orbits", or the electrons stimulate the metal atoms to emit radiation through collisions. Both the braking of the electrons and the excitation of the metal atoms result in X-rays being emitted. Unfortunately, the radiation is emitted equally in all directions and is then difficult to bundle again into a directed beam. In addition, the wave trains of the X-rays are completely random and disordered.

Physicists at the Institute for X-ray Physics at the University of Göttingen have now observed a novel effect when the anode is replaced by a suitable structure of thin layers made of materials with different electron densities. The layer thickness of the "sandwich structure" must be a few millionths of a millimeter. If a special sequence of layers is chosen, the X-rays can be guided. "If the accelerated electrons patter on this sandwich structure, the angular spectrum of the generated X-rays changes," says Malte Vassholz, first author of the work, "the generated X-rays are simultaneously directed in a certain direction".

With detailed numerical calculations, the results can be reproduced in the model and calculated for a given choice of structure. "According to our calculations, the effect could be further increased by optimizing the structure and used to generate X-rays with greater brilliance", adds Prof. Dr. Tim Salditt. It is hoped that X-ray measurements, which were previously only possible with large accelerators such as the electron synchrotron in Hamburg, can also be brought "into the laboratory" in some cases. "X-ray imaging applications of microscopic and low-contrast objects, such as soft biological tissue, are particularly interesting," says Salditt.