  Intense ultrashort pulse lasers are used for fs resolution pumpprobe
experiments more and more at large scale facilities, such as free electron
lasers (FEL). Measurement of the arrival time of the laser pulses and
stabilization to the machine or other sub-systems on the target, is crucial for
high time-resolution measurements. In this work we report on a single shot,
spectrally resolved, non-collinear cross-correlator with sub-fs resolution.
With a feedback applied we keep the output of the TW class Ti:sapphire
amplifier chain in time with the seed oscillator to ~3 fs RMS level for several
hours. This is well below the typical pulse duration used at FELs and supports
fs resolution pump-probe experiments. Short term jitter and long term timing
drift measurements are presented. Applicability to other wavelengths and
integration into the timing infrastructure of the FEL are also covered to show
the full potential of the device.
