A Newmethod to Generate Ultrashort and Coherent Pulses of Short-wavelength Synchrotron Radiation

A laser-based method to generate ultrashort pulses of synchrotron radiation in electron storage rings is coherent harmonic generation (CHG) using two undulators to produce coherent radiation at harmonics of the initial laser wavelength by microbunching. The bunching factor and thus the pulse intensity, however, decreases exponentially with increasing harmonic order. Echo-enabled harmonic generation (EEHG), proposed in 2009 as FEL seeding scheme, can be used to produce short synchrotron radiation pulses at higher harmonics, but requires three undulators in a straight section. In this paper, a less space-consuming method based on seeding with intensity-modulated laser pulses is introduced, which also has the potential of significant bunching factors at high harmonics.