The BESSY Raytrace Program RAY

Abstract

The raytracing program RAY simulates the imaging properties of an optical system. It randomly creates a set of rays within various types of light sources and traces them according to the laws of geometric optics through optical elements onto image planes. The distribution of the rays at the source, optical elements and image planes can be displayed. A ray is described not only by its coordinates with respect to a suitable coordinate system, but also by its energy and its polarisation determined by the Stokes vector. Different source types are implemented with special emphasis on a realistic simulation of source intensity, volume and emission characteristics, especially for synchrotron radiation including dipole and undulator sources. Optical elements can be reflection mirrors of nearly any figure (plane, cylindrical, spherical, aspherical… ), gratings, zone plates, foils or crystals. The absolute transmission of the optics including the effect of optical (multilayered) coatings is calculated according to the reflection/refraction/transmission process from the optical constants of the materials involved. The influence of misalignment of the source and/or the optical elements, slope errors and thermal deformation of the optics can also be taken into account. A graphical display of spot patterns at any position of the beam, intensity and angular distributions, absolute flux, polarisation, energy resolution is possible.