A Cryogenic Target for Compton Scattering Experiments at HI$\gamma$S

We have designed, constructed, and tested a cryogenic target for use at the High Intensity $\gamma$-ray Source (HI$\gamma$S). The target is able to liquefy helium (LHe), hydrogen (LH$_2$), and deuterium (LD$_2$). It precools room-temperature gas in two stages with a Gifford-McMahon cryocooler. The precooled gas condenses onto a series of copper fins and drips down to fill a 0.25~L Kapton target cell. The cryotarget will be used to measure nuclear and nucleon electromagnetic polarizabilities. The electromagnetic polarizabilities of the nucleons, $\alpha$ and $\beta$, will be probed by scattering a $\gamma$-ray beam on unpolarized LD$_2$ and LH$_2$ targets. Scattered photons will be detected by the HI$\gamma$S NaI Detector Array (HINDA). We have tested the target with LHe at 3~K and are preparing for LD$_2$ testing and production running.