[en] X radiation of relativistic electrons in crystals can be caused by different radiation mechanisms such as parametric Cherenkov radiation, coherent and non-coherent bremstrahlung, and characteristic radiation. The radiation mechanism can be identified by measuring radiation intensity angular distributions. An experimental facility, consisting of a goniometer with remote control systems for electron beam shaping and parameter control at a monocrystal target, radiation extraction channels, and a matrix detector, consisting in its turn of 4096 thin-wall ionization chambers operating on-line with the Elektronika-60 microcomputer, is designed at the LU-40 40 MeV electron linear accelerator to reach the aim