Some features of diffraction and transition radiation at the distance less than γ²λ

Recently the projects on the creation of the beam diagnostic methods using backward transition radiation (BTR) and noninvasive diagnostic methods using backward diffraction radiation (BDR) of electrons, passing through a conductive slit, are in progress. Most of the BTR and BDR theoretical models assume that the size of the radiation source region is much less than the size of the image in the observation point. For the large electron energy this condition actually may not be satisfied. This problem was considered in [Phys. Lett. A 273 (2000) 135], but this model may be used actually for very simple targets. We suggest a simple model, which allows us to estimate with a good accuracy the radiation properties of transition and diffraction radiation in near field zone from the targets of different geometries. The samples for transition and diffraction radiation from a slit target are presented. Also the transition radiation focusing effect on the parabolic targets is shown.