EMISSION OF SINGLE GAMMA-RAYS BY ELECTRONS WITH ENERGIES OF HUNDREDS OF GEV IN ORIENTED CRYSTALS

Cross sections are calculated for the emission of single hard photons by electrons with energies of 150-1000 GeV as they pass through orient ed crystals at small angles to the crystallographic axes. The contribu tion of incoherent emission at isolated atoms of the crystal is taken into account in the calculations, along with the emission in the conti nuum potential. The calculations are compared with the customary Bethe -Heitler spectrum for a, thick amorphous target with allowance for pho ton absorption due to electron-positron pair production. It is shown t hat, in this range of energies, an oriented crystal can tie more effic ient than a thick amorphous target for creating a larger number of har d gamma rays with energies comparable to the energies of the emitting electrons. (C) 1998 American Institute of Physics. [S1063-7842(98)0080 9-5].