Multi-bend Achromat Lattices for Storage Ring Light Sources

One of the most important factors for synchrotron radiation research is the brilliance, typically defined as photon flux emitted into a unit solid angle from a unit source size within a defined relative bandwidth. The product of rms solid angle and source size yields the beam emittance. To reach high brilliance, both the horizontal and vertical beam emittance must be small and the stored beam current high. Even at zero emittance, radiative diffraction effects produce a finite volume of phase space of the radiation [1 H. Onuki and P. Elleaume, Undulators, Wigglers and their Applications, Taylor & Francis, New York (2003).[Crossref] , [Google Scholar]], with the effective photon beam emittance given by: where λ is the X-ray-wavelength and Eγ is the photon beam energy. In recent years, the user community has become increasingly interested in the transverse coherence properties of the X-ray beam. By using the half-Airy disk criterion [2 Z. Huang, Brightness and Coherence of Synchrotron Radiation and FELs, Proc. IPAC 2013, 16 (2013). [Google Scholar]], the coherent fraction of the emitted coherent light is given in Eq. (2), where εitot is the total emittance, including the contribution of the electron beam and the undulator radiation.