Statistical optics for synchrotron emission: numerical calculation of coherent modes

In view of the recent raising interest in partially coherent X-ray radiation produced by ultra low emittance storage rings I present a numerical algorithm for the coherent mode decomposition of undulator emission in storage rings. A numerical description of the undulator cross spectral density in terms of its coherent modes opens a new door for theoretical investigations of coherence properties and for beamline design. The description in coherent modes is much more memory efficient than the naive storage of the cross spectral density. Some applications the algorithm will be presented as well.