The Polarized Internal Target at ANKE: First Results

For future few-nucleon interactions studies with polarized beams and targets at COSY-Juelich, a polarized internal storage cell gas target was implemented at the magnetic spectrometer ANKE in summer 2005. First commissioning of the polarized Atomic Beam Source (ABS) at ANKE was carried out and some improvements of the system have been done. At the same time, storage-cell tests to determine the COSY beam dimensions have been performed. In February 2005, a first storage cell prototype was implemented. It was made from an aluminum foil covered by a special PTFE suspension. In November 2005, tests were carried out with a storage cell using a polarized hydrogen beam from the ABS, electron cooling and stacking injection of the COSY beam at different deflection angles of the ANKE spectrometer magnet. An average target polarization of P=0.44{+-}0.03 (November 2005 beamtime) was measured, while we expected about P=0.51-0.55 due to the availability of rf-transition units in the ABS. The jet target thickness was measured as (1.5{+-}0.1){center_dot}1011 atoms/cm2. In March 2006, measurements with unpolarized protons at T=831 MeV and an unpolarized H2 beam injected from a gas feeding system into the aluminum storage cell were carried out. The analysis of the pp {yields} pp{pi}0 and ppmore » {yields} pn{pi}+ reactions showed that events from the extended target can be clearly identified in the ANKE forward detector system.« less