Experimental study of radiation losses by relativistic electrons in thick crystals

It is shown that under certain accelerated electron energy in case of axial orientation it is possible to find such an optimal crystal thickness when radiation losses into the collimator reach the maximum value. Formula of dependences of maximum radiation losses into the collimator on the crystal lattice parameters are derived for optimal thickness crystals. To check the formula, allowing one to purposefully conduct a search for crystals with the required radiation loss parameters, an experiment at a synchrotron with the accelerated electron energy E=900 MeV is carried out. Crystals of diamond (with thickness t=0.078 radiation length (r.l.), axis <100>), silicon (t=0.22 r.l., axis <111>) and tungsten (t=0.183 r.l., axis <111>) having thickness close to the optimal one were used as targets. Experimental values of the electron radiation losses into the collimator Θc=0.6 mrad made up respectively 4.6; 2.8; 2.0 MeV/e- for diamond, silicon, tungsten crystals, which is well described by the formula presented