Kiessling, R., S. Gewinner, A. Paarmann, W. Schöllkopf, M. Wolf:
In: Proc. of 38th International Free-Electron Laser Conference, Santa Fe, NM, USA, August 20-25, 2017,
Paper MOP059; JACoW, Geneva, CH (2018), pp 4;
The combined application of FEL radiation and femtosecond table-top lasers for two-color spectroscopy demands an accurate pulse synchronization. In order to employ the Infared FEL at the Fritz Haber Institute for non-linear and time-resolved experiments, an RF-over-fiber-based timing system has been established. Using a balanced optical cross-correlation scheme, we determined an FEL micro-pulse timing jitter of 100-200 fs (rms). The long-term timing drift was found to be well correlated to the energy fluctuations of the accelerated electron bunches. By means of the jitter-corrected cross-correlation signal, we directly measure the FEL pulse shape at different cavity detunings. For large cavity detuning, narrowband IR radiation (~ 0.3 % FWHM) can be generated and utilized for high-resolution non-linear spectroscopy. On the other hand, sub-picosecond pulses are provided at small detuning, which are well-suited for time-resolved measurements. At intermediate detuning values, we observe the build-up and dynamics of multipulses that result in the well-known limit-cycle power oscillations.
The original publication is available by link DOI: 10.18429/JACoW-FEL2017-MOP059