Basics of Multilayer Optics

Our X-ray optics consist of multilayer films which reflect X-rays using the Bragg diffraction effect. The single layers, each one only a few nanometers thick, are mostly amorphous. The multilayer may consist of up to several hundred layers. A high reflectivity is obtained when the multilayer materials have a high density difference and simultaneously a low absorption. The two X-ray optical properties of relevance, i.e. the absorption and dispersion, depend on the wave-length of the X-ray. Therefore, each wavelength requires its own particular type of multilayer, in order to achieve the best results. We are able to carry out X-ray optical simulations, placing our focus on the specific application with the aim of optimizing the performance.

Optical simulations

In addition to the choice of the multilayer materials, details of the beam path are important for the application. A parabolic mirror is required for obtaining a parallel beam, whereas elliptical mirrors are necessary for focusing optics. We use ray tracing methods to calculate all beam properties along the beam line. This enables us to study and optimize the beam characteristics according to our customers requirements. Ray tracing is a Monte-Carlo simulation method where statistically generated X-rays are transmitted through the virtual optical system. For a realistic simulation it is necessary to take the exact size of the source into account. The extended source dimensions in particular sometimes lead to results that differ significantly from performance estimations based on point-source assumptions. The plot shows the result of a typical ray tracing calculation.