Multisectional FELs with dispersion and undulator sections

A free electron laser scheme consisting of a large number of identical parts is considered. Each part consists of an undulator and a dispersion section. The dispersion equation describing the process of radiation is derived in a one dimensional approach. The gain dependence on the dispersion section parameters is investigated. The regime having maximum radiation gain is found. The well known TDA code was modified for 3-D simulation of a multisection FEL. Stanford linac parameters were used in simulation. A total power gain exceeding 4 × 108 can be achieved at a wavelength of 4.2–4.3 nm and a total length of the magnetic system of 20 m. Thus the gain of uniform FELs can be substantially exceeded in multisection FELs.