Image of the transverse bunch profile via coherent optical transition radiation

The use of optical transition radiation (OTR) monitors is a standard technique to measure transverse beam profiles at many electron accelerators. With modern accelerator technology it is possible to produce and accelerate even ultrashort electron bunches with sub-femtosecond duration. Such bunches interacting with the OTR target generate coherent optical transition radiation (COTR). For the COTR case, a reconstruction of the bunch profile from a recorded image using a conventional optical scheme is a task with inconclusive solution. In this paper an approach is proposed which is based on the strict propagation of COTR fields through a focusing lens. As result a linear dependence of the measured rms image size on the bunch size is obtained.