Until now, neutron spectra were measured for 17MeV polarized photons on a thick Au target at angles from 30 to 150 degrees [1]. The result shows two components of neutrons, evaporation and direct. The angular distribution of the evaporation shows isotropic and that of the direct shows dependence on angle between photon polarization and neutron emission. These spectra are useful to evaluate models and parameters in theoretical calculation, however, comparison between of experiment and calculation has not been done. For this comparison, double differential cross section (DDX) is more preferable than thick target neutron spectra, because cumulative effect in the target can be eliminated. Therefore, we measured the DDX of the 197Au(g,n) for 17 MeV polarized photons on a thin target and compared the results with that of PHITS calculation. The experimental setup was identical except for target thickness, the reduction of which decreases the attenuation of photon and neutron. The polarization direction of photon was set to horizontal, that was parallel to the floor. The neutron detector, a NE213 organic liquid scintilla tor (12.7 cm  x12.7 cm L), was placed at 90 degrees horizontally with respect to photon beam axis and 60 cm away from the target. PHITS code (version 3.12) has been used to calculate the double differential cross section. The result shows neutron spectrum only from evaporation model although two components were observed in experiment. The quantitative comparison and discussion will be presented at the symposium.

Keywords: differential double cross section photon neutron , 17MeV polarized photon, Au, PHITS calculation.