Electron bunch shape measurements at the TTF-FEL

The TESLA Test Facility linac has been operated in the first half of 2002 with two bunch compressors to drive the TTF-FEL free electron laser. During this running period, SASE radiation with a wavelength around 100 nm has been routinely delivered to experiments. The longitudinal shape of the electron bunches is a crucial property of the electron beam: a peak current in the order of 1 kA is required to drive the SASE process with the given undulator design, transverse emittance, and energy spread. We report on measurements of the bunch length and shape for different operating conditions of the two bunch compressors.