From Synchrotrons to FELs: How Photons are Produced; Beamline Optics and Beam Characteristics

Four generations of synchrotrons, and a new one of x-ray free electron lasers (X-FELs), have supported the research of tens of thousands of users worldwide. Although formal theories of such sources can be quite complicated, the underlying physics can be handled using basic notions of special relativity, with no complicated formalism. In order to be used for experiments, the radiation emitted by an undulator, a wiggler or a bending magnet must be optically processed along a beamline and then delivered to an experimental system. Synchrotron radiation has a pulsed time structure: the peak values of brightness and flux still have a wide margin for improvement. The situation is actually similar to that of visible light sources at the time of the first lasers. To understand the FEL mechanism, the chapter illustrates an example of a hypothetic layered electron crystal.