RU

2015: Harmonic emission in undulators for free electron lasers: compensation of the electron beam emittance by constant magnetic field

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Konstantin Zhukovsky (Faculty of Physics, Department of Theoretical Physics, MSU) gave complete analytical description of the harmonic generation in undulators with accurate account for all major losses in real devices and demonstrated how the electron beam emittance can be compensated by properly imposed constant magnetic field.

An analysis of the undulator radiation (UR) with account for major sources of the spectral line broadening is presented. For relativistic electrons we obtain exact analytical expressions for the UR spectrum, the intensity and the emission line shape with explicit account for the finite size of the electron beam, the emittance and the energy spread. They reveal the interplay between the constant magnetic field components in undulators and the emittance of the electron beam. Partial compensation of the divergency by properly imposed weak constant magnetic component is demonstrated in the analytical form. Considering the examples of radiation from single and from double frequency undulators, we study high harmonic generation with account for all homogeneous and inhomogeneous broadening contributions, including the characteristics of the electrons beam. We apply our analysis to free electron laser (FEL) calculations and show how high harmonics can be effectively used in modern and in future X-RAY FEL installations.

These results have been published in the paper: K.V. Zhukovsky Harmonic generation by ultrarelativistic electrons in a planar undulator and the emission-line broadening, Journal of Electromagnetic Waves and Applications 29, 132142 (2015).