(Gamma,n) Polarization Asymmetry Ratios of 209-Bismuth

There has been an ongoing research program measuring the polarization asymmetries from the $(\gamma,n)$ reaction on various nuclei using linearly and circularly polarized gamma-ray beams from the High Intensity Gamma Ray Source (HI$\gamma$S) at Duke University. Experimental results will be shown for $(\gamma,n)$ polarization asymmetry ratios on $^{209}Bi$ for neutron energies from $2-7$ MeV, and for angles $55^{\circ},90^{\circ},125^{\circ},72^{\circ},$ and $107^{\circ}$. Measurements were taken using linearly polarized gamma ray beam energies from $11-15.5$ MeV and circularly polarized at $15.5$ MeV, and 16 liquid scintillator detectors, half in the plane of polarization, and half perpendicular. Results demonstrate that Giant Dipole Resonance causes isotropic ratios at lower neutron energies (2-4 MeV), and non-isotropic ratios at higher neutron energies (5-7 MeV). This research introduces the possibility of using $(\gamma,n)$ as a method for identifying materials crossing international borders, by knowing ratios of many different metals.