High Energy Photon Production with Laser-Compton Backscattering and Photo Nuclear Reaction

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We have generated photon beam using the Compton backscattering of laser beam on the relativistic electron beam of 1 GeV energy in the storage ring, NewSUBARU. (l) The laser photons of the wave length of 1064nm were injected to the interaction area by using six mirrors and a lens. (2)The fine -tuning of the laser-beam axis and the collimator alignment was accomplished by maximizing the count rate in a detector. (3)The energy spectra of the backscattering photons have been measured with HPGe detector. The maximum photon energy is 17.6 MeV. We have used three kinds of collimators that are 20mmφ, 10mmφand 2mmφ. (4) The obtained energy spectra were compared with the simulated model calculations using the EGS4-code. The simulated energy spectra calculated by assuming an ideal energy spectra at each collision point and by taking account of the geometry including the detector size and of the attenuation by various media such mirror and glass window etc. The calculations show good agreements with the measured energy spectra. (5) From the comparisons, the detected photons are about 4 x 10^3/sec/mA/W, 2 x 10^3/sec/mA/W and 3 x 10^2/sec/mA/W for 20mmφ, 10mmφand 2mmφ collimators, respectively. (6) The measurement of the nuclear photo-absorption cross sections (n, γ ) in the El giant resonance energy region has been carried out using the absorption method. The absorption coefficient for 197Au has been measured using the backscattering photons. We have obtained the peak cross section of 530 mb. Hereafter, we will measure not only the giant resonance but also discrete states using the backscattering photons.