• K.E. Hacker
  DESY, Hamburg

By using magnetic chicane bunch compressors, high-gain free-electron lasers are capable of generating femtosecond electron bunches with peak currents in the kilo-ampere range. For accurate control of the longitudinal dynamics during this compression process, high-precision beam energy and arrival-time monitors are required. Here we present an electro-optical detection scheme that uses the signal of a beam pickup to modulate the intensity of a femtosecond laser pulse train. By detecting the energies of the laser pulses, the arrival-time of the pickup signal can be deduced. Depending on the choice of the beam pickup, this technique allows for high-resolution beam position measurements inside of magnetic chicanes and/or for femtosecond-resolution bunch arrival-time measurements. In first prototypes we realized a beam position monitor with a resolution of 3 μm (rms) over a many-centimeter dynamic range and a bunch arrival-time monitor with a resolution of 6 fs (rms) relative to a pulsed optical reference signal.