Femtosecond Laser-Electron Interaction in a Storage Ring Studied by Terahertz Radiation

The laser-induced energy modulation of relativistic electrons in the BESSY II storage ring was studied by temporal and spectral characterization of femtosecond far-infrared (THz) pulses being emitted after the electons have passed dispersive elements. The length of the femtosecond density modulation and its temporal decay have been measured as well as bunch shapes down to a length of 3 ps (rms). The THz diagnostics is crucial for the operation of the recently commissioned” femtoslicing” source at BESSY.