Production of MonochromaticγRays by Collimation of Coherent Bremsstrahlung

The coherent bremsstrahlung from a 50-{μ}m-thick crystal of silicon was collimated to 0.234(mₑc²E₁) rad with the incident energy of the electrons E₁=1 GeV. The energy spectrum shows a sharp spike with the signal-to-background ratio greater than 10 and the half-width Δk=15 MeV at a photon energy $k=185$ MeV. The spectrum is in good agreement with theory based on \"Uberall's treatment. A maximum intensity of 2×{}10⁴ photons/MeV sec has been obtained at the spike.