Compton scattering from nuclear targets at HI$\vec{\gamma}$S

A Compton scattering program is presently being developed at HI$\vec{\gamma}$S utilizing the nearly-monoenergetic beams of 100\% polarized $\gamma$-rays produced by intra-cavity Compton backscattering of FEL photons. Polarization asymmetries of Compton scattering on $^{16}$O have been measured between 25-40 MeV to search for a narrow iso-vector giant quadrupole resonance (IVGQR). A beam with $\Delta$E/E$\sim$10\% was incident on a H$_2$O target. The scattered $\gamma$-rays were detected by four 10''$\times$10'' NaI detectors located between $\theta$=90-150$^\circ$ and $\phi$=0, 90, 180, and 270$^\circ$. The data indicate that significant, narrow concentrations of E2 strength are not present below 40 MeV. Another measurement of the Compton scattering cross section of $^3$He between E$_\gamma$=3-11 MeV is proposed to extract the electric polarizability, $\alpha_E$, of the $^3$He nucleus. A preliminary run has been performed to study the backgrounds, and a high pressure gas target system has been tested.