Tests of a high density polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ target for electron scattering

We have developed a polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ target for polarized electron scattering measurements. The target has a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ density of 1.1×${10}^{20}$ nuclei ${\mathrm{cm}}^{\mathrm{-}3}$, a total length of 7.5 cm and thin glass windows of 120–180 μm thickness. ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ polarization as large as 40% was produced, limited only by the available laser power. The ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ polarization was maintained during bombardment with up to 22 μA of 578 MeV electrons. A measurement of elastic scattering of polarized electrons from polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ confirmed that the nuclei in the electron beam had the expected polarization. The polarization is produced by spin exchange with laser optically pumped Rb vapor, and the target design incorporates two separated volumes, one for optical pumping and the other for the electron bombardment. Extensions of this design are practical for fixed target electron scattering from polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ planned for SLAC and CEBAF.