Harmonic Content of the BESSY FEL Radiation

The BESSY soft X-ray FEL is planned as a High-Gain Harmonic-Generation (HGHG) FEL facility. The associated tunable seed lasers will cover the spectral range of 230 nm to 460 nm. Cascaded HGHG stages will be used to reduce the seed wavelength to the desired wavelength range of 1.24 nm ≤ λ ≤ 51 nm. Using the harmonic con tent of the high-intensity radiator output the number of necessary HGHG stages can be reduced. Moreover the higher harmonic content of the final amplifier extends the spectral range and thus is of high interest to the user community. In this paper, the higher harmonic content of the final output as well as of the radiator ouputs are investigated. The main parameters such as output power, pulse duration and band-width as well as their suitability for seeding are discussed.