Considerations on the diffraction limitations to the spatial resolution ofoptical transition radiation

The interest in using optical transition radiation (OTR) in high energy (mu ltiGeV) electron beam diagnostics has motivated theoretical and experimenta l investigations on the limitations brought by diffraction on the attainabl e resolution. This paper presents calculations of the diffraction effects i n an optical set-up using OTR. The OTR diffraction pattern in a telescopic system is calculated taking into account the radial polarization of OTR. Th e obtained diffraction pattern is compared to the patterns obtained by othe r authors and the effects of different parameters on the shape and on the s ize of the OTR diffraction pattern are studied. The major role played by th e radial polarization on the shape of the diffraction pattern is outlined. An alternative method to calculate the OTR diffraction pattern is also sket ched.