A. Dvoredsky

THE HERMES POLARIZED 3HE INTERNAL GAS TARGET

Abstract The HERMES experiment is investigating the spin structure of the proton and neutron via deep-inelastic scattering of polarized positrons from polarized nuclear targets. The polarized positrons are provided by the HERA positron storage ring at DESY, Hamburg, Germany. The targets are pure internal gas targets. Data acquisition began in 1995, utilizing a polarized 3 He internal gas target to study the spin structure of the neutron. The target gas was polarized using the metastability-exchange optical-pumping technique and then injected into a cryogenically cooled target cell. The target was designed to operate with either longitudinal or transverse directions of polarization. Operating conditions included polarizations of up to 54% and target thicknesses of 1×10 15 nucleons/cm 2 . In this paper the HERMES polarized 3 He internal gas target is described in detail.

Temperature dependence of 3He polarization in aluminum storage cells

Abstract The temperature dependence of the polarization of 3 He atoms in an internal target cell has been studied. Metastable optically pumped polarized 3 He atoms with typical polarization values of 40% were injected into a thin-walled aluminum cell of 40 cm length and a 29.0 × 9.8 mm 2 elliptical cross-section. The cell temperature was varied between 5 and 85 K. The polarization inside the target cell was measured via an asymmetry in the 3 He → (d,p) 4 He reaction at a deuteron energy of 4 MeV. An exponential decrease of the polarization was found for temperatures less than 15 K. For a temperature of ∼6 K a polarization consistent with zero was measured.