For the design of any optical system, it is essential that the source of the radiation be well characterized. One of the primary advantages of synchrotron radiation is its inherent brilliance. These results from the large flux of photons produced in a small solid angle by a source of small lateral size, the electron beam. The beta functions and dispersion, ηx, for a proposed triple bend acromat (TBA) lattice for a storage ring of the third generation. The source dimensions in a dipole magnet consist of the electron beam dimensions and the angle of emission of the radiation, the opening angle, both horizontally and vertically. The polarization is an important characteristic of the radiation and can be exploited with the help of moveable apertures which enable one to select the solid angle from which the radiation is taken. In regard to radiation, the coherence of a source is measured by the interference of wavetrains from that source with each other.