Electro-0ptical Bunch Profile Measurement at CTF3

A new electro-optic bunch profile monitor has recently been installed in CLIC Test Facility 3 at CERN. The monitor is based on an electro-optic spectral decoding scheme which reconstructs the longitudinal profile of the electron bunch by measuring its Coulomb field. The system uses a 780 nm fibre laser system, transported over a 20m long distance to the interaction chamber, where a ZnTe crystal is positioned close to the beam. The assembly also contains a traditional OTR screen, which is coupled to a second optical line and used to adjust the temporal overlap between the laser and the electron pulse. This paper presents the detection system in detail, as well as reporting on the first measurements performed with beam.