Frequency Doubling Mode of Operation of Free Electron Laser FLASH2

Kuhlmann, Marion; Schneidmiller, Evgeny; Yurkov, Mikhail

doi:10.18429/JACoW-FEL2017-MOP036

Frequency Doubling Mode of Operation of Free Electron Laser FLASH2

Feb, 2018

4 pages

Part of Proceedings, 38th International Free Electron Laser Conference, FEL2017

Contribution to:

- FEL 2017

Published: Feb, 2018

DOI:

10.18429/JACoW-FEL2017-MOP036

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Abstract: (JACoW)

We report on the results of the first operation of a frequency doubler at free electron laser FLASH2. The scheme uses the feature of the variable-gap undulator. The undulator is divided into two parts. The second part of the undulator is tuned to the double frequency of the first part. The amplification process in the first undulator part is stopped at the onset of the nonlinear regime, such that nonlinear higher-harmonic bunching in the electron beam density becomes pronouncing, but the radiation level is still small to disturb the electron beam significantly. The modulated electron beam enters the second part of the undulator and generates radiation at the second harmonic. A frequency doubler allows operation in a two-color mode and operation at shorter wavelengths with respect to standard SASE scheme. Tuning of the electron beam trajectory, phase shifters and compression allows tuning of intensities of the first and the second harmonic. The shortest wavelength of 3.1 nm (photon energy 400 eV) has been achieved with a frequency doubler scheme, which is significantly below the design value for the standard SASE option.