PERFORMANCE OF A POLARIZED DEUTERIUM INTERNAL TARGET IN A MEDIUM-ENERGY ELECTRON STORAGE-RING

A polarized deuterium target internal to a medium-energy electron stor age ring is described in the context of spin-dependent (e,e'd) and (e, e'p) experiments. Tensor polarized deuterium was produced in an atomic beam source and injected into a storage eel target. A Breit-Rabi pola rimeter was used to monitor the injected atomic beam polarization. An electrostatic ion-extraction system and a Wien filter were utilized to measure on-line the atomic fraction of the target gas (71+/-2%) in th e storage cell. A target thickness t similar or equal to 2x10(13) H-2/ cm(2) was achieved. The target tensor polarization was varied from P-z z(+)=0.49(3) to P-zz(-)=-0.89(6) while keeping the vector polarization P-z at zero. The luminosity was similar to 2x10(31) e(-).H-2 . cm(-2) S(-1) at a beam current of 120 mA. The performance was stable over a f ive-week running period. A large acceptance non-magnetic detector syst em was used for the electron-proton (deuteron) coincidence measurement . It is demonstrated that these techniques result in low backgrounds d ue to scattering from species other than the polarized target gas and anew for fast and flexible orientation of the target spin. Specific is sues such as interfacing the experiment to the storage ring and monito ring the performance of the target system are discussed in detail.