Real-time, single-shot temporal measurements of short electron bunches, tera-hertz CSR and FEL radiation

Electro-optic detection of the Coulomb field of electron bunches is a promising technique for single-shot measurements of the bunch length and shape in the sub-picosecond time domain. This technique has been applied to the measurement of 50 MeV electron bunches in the FELIX free electron laser, showing the longitudinal profile of single bunches of around 650 fs FWHM. The method is non-destructive and real-time, and therefore ideal for online monitoring of the longitudinal shape of single electron bunches. At FELIX we have used it for real-time optimization of sub-picosecond electron bunches. Electro-optic detection has also been used to measure the electric field profiles of far-infrared (or tera-hertz) radiation generated by the relativistic electrons. We have characterized the far-infrared output of the free electron laser, and more recently, we have measured the temporal profile of tera-hertz coherent synchrotron radiation (CSR) generated at one of the bending magnets. (authors)