Energy calibration of the NewSUBARU storage ring by laser compton-scattering gamma rays and its applications

Using γ -ray beams produced in the inverse Compton scattering between CO₂ 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) γ-ray beams were produced at energies from 561 keV 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 γ -ray beams by Monte Carlo simulations. The precision of the calibration is (4 - 7) × 10^-5. The reproducibility of the electron beam energy is excellent in an independent injection and deceleration. As applications of the absolute energy calibration of the electron beam, we investigated the linearity of a 3.5" × 4.0" LaBr₃(Ce) detector in the response to γ rays at energies up to 10 MeV and the energy profile of LCS γ-ray beams.