NSLS-II Seminar

Efficient computation methods and multiple calculation examples dedicated to spontaneous emission and wavefront propagation in the 3rd generation synchrotron radiation sources will be presented. With the approach to be described, the electric field emitted by a relativistic electron is calculated in the frequency domain by accurate expressions derived from Liénard-Wiechert potentials, without the standard separation on the "velocity" and "acceleration" parts. This approach provides an efficient numerical method, which is valid in near- and far-field zones, and is applicable to almost arbitrary magnetic field: e.g. field of an undulator or wiggler, central or edge part of a bending magnet or a short magnet. Once calculated in a transverse plane at some distance from the source, the electric field can be numerically propagated, using the methods of Fourier optics (and, were necessary, asymptotic expansions) through an optical beamline, to an "observation plane" of interest, were intensities at different polarizations can be considered. Effects related to finite electron beam emittance (e.g. partial coherence) can be taken into account by summing-up intensities of radiation from different (macro-) electrons at the end of the propagation. These methods are implemented in the "Synchrotron Radiation Workshop" (SRW) computer code. The results of all calculations to be presented were obtained using this code. Many of these results will illustrate performance of real insertion devices and beamlines on existing 3rd generation sources. Some examples of wavefront propagation calculations for the 4th generation sources will also be given.