THz based femtosecond level arrivaltime monitor for quasi-cw electron accelerators

In this contribution we present an electro-optic arrival time monitor for coherent THz pulses. The monitor operates robustly at high repetitionrates and extremely low THz pulse energies. It thereby has the potential to provide few femtosecond-level synchronization on next generation large scale X-ray photon sources based on high repetition rate electron accelerators such as X-ray FEL´s or energy recovery linacs.