High-intensity γ-ray source

A mono-energetic tunable source of 100% linearly polarized γ rays has been developed at the Duke Free-Electron Laser Laboratory in conjunction with Triangle Universities Nuclear Laboratory. The OK-4 FEL is coupled to a 1-GeV electron storage ring and generates intense beams of visible or UV photons. In γ-ray production mode, the OK-4 photons Compton scatter from high-energy electrons inside the optical cavity leading to backscattered γ rays. The strong correlation between scattering angle and γ-ray energy permits a selection of the energy spread of the γ-ray beam that depends on a simple geometrical aperture located along the optical axis. Results obtained/(design parameters) indicate γ-ray beams with energies of 2.2-58/(2.0-175) MeV, ΔE/E<1.0% and total fluxes greater than 107/(1010)γ rays/s