Considerations on implementing EEHG with a strong linear chirp
Due to the stochastic nature of SASE radiation its longitudinal coherence is limited to a small fraction of the electron bunch. By pre-bunching the electrons before entering a radiator, the FEL radiation is ensured to have the same initial phase all through the bunch. Echo enabled harmonic generation (EEHG) is a technique that, by cleverly using two modulators and two dispersive sections, creates