High-energy photon beam production with laser-Compton backscattering

We have produced a beam of high-energy gamma-rays by Compton backscattering of 1064 nm laser photons from 1 GeV electrons circulating in a storage ring. Measuring the energy spectra of the backscattering photons with an HPGe detector, we have found that the maximum energy of 17.6 MeV and the measured energy spectra show agreement with the simulation calculations, while the detected photon yields were measured at about 4×103, 2×103 and 3×102 photons s−1mA−1W−1 for the 20, 10 and 2 mmφ collimators, respectively. The photon energy widths from the collimators correspond to 6.6–17.6 MeV, 12.4–17.6 MeV and 17.3–17.6 MeV, respectively. By using these photons, we measured the total nuclear photoabsorption cross-sections in the E1 giant resonance energy region for 197Au using the attenuation method and we have demonstrated that the photon attenuation method will be a useful tool for studying photonuclear reactions.