Energy Calibration of the NewSUBARU Storage Ring for Laser Compton-Scattering Gamma Rays and Applications

Using $\gamma $ -ray beams produced in the inverse Compton scattering between ${\hbox{CO}}_2$ laser photons and relativistic electrons, we have calibrated electron beam energies in the nominal energy range 550–974 MeV at the synchrotron radiation facility NewSUBARU. The laser Compton-scattering (LCS) $\gamma $ -ray beams were produced at energies from 561 to 1728 keV and detected with a high-purity germanium detector. The electron beam energies were determined by reproducing the full energy peaks of the $\gamma $ -ray beams by Monte Carlo simulations. The accuracy of the calibration is $(5.5 - 9.4) \times {10^{ - 5}}$ . The reproducibility of the electron beam energy is excellent in an independent injection and deceleration. The present energy calibration of the electron beams offers a standard for the energy calibration of high-energy LCS $\gamma $ -ray beams produced with a ${\hbox{Nd:YVO}}_4$ laser. As applications of the energy calibration, we investigated the energy linearity of a $3.5^{\prime\prime} \times 4.0^{\prime\prime}$ ${\hbox{LaBr}}_3({\hbox{Ce}})$ detector in the response to $\gamma $ -rays at energies up to 10 MeV and the energy profile of the high-energy LCS $\gamma $ -ray beams.