Chirped-laser based electron bunch length monitor

An electron bunch length monitor will be discussed which is based on the birefringence induced by the Coulomb field of the bunch in an electro-optically active crystal that is placed in close proximity of the beam. This birefringence is used to change the polarization of an external laser probe pulse. Measurements, performed at the FELIX facility, both in sampling mode (where the 1 GHz micropulse repetition rate of the accelerator was used) and in single-shot mode, will be described. In the latter case, the laser pulse is stretched and chirped, which allows the longitudinal bunch profile to be encoded on its spectral content. Issues related to the (sub-picosecond) time resolution will be discussed.