First Experiments with the Polarized Internal Gas Target (PIT) at ANKE/COSY

For future few-nucleon interaction studies with polarized beams and targets at COSY-Juelich, a polarized internal storage-cell gas target was implemented at the magnet spectrometer ANKE. First commissioning of the polarized Atomic Beam Source (ABS) at ANKE was carried out and some improvements of the system have been done. Storage-cell tests to determine the COSY beam dimensions have been performed. Electron cooling combined with stacking and stochastic cooling have been studied. Experiments with N2 gas in the storage cell to simulate the background produced by beam interaction with the aluminum cell walls were performed to investigate the beam heating by the target gas. The analysis of the d-vectorp-vector→dp and d-vectorp-vector→(dpsp)π0 reactions showed that events from different positions of the extended target can be clearly identified in the ANKE detector system. The polarization of the atomic beam of the ABS, positioned close to the strong dipole magnet D2 of ANKE, was tuned with a Lamb-shift polarimeter (LSP) beneath the target chamber. With use of the known analyzing powers of the quasi-free np→dπ0 reaction, the polarization in the storage cell was measured to be Qy = 0.79±0.07 in the vertical stray field of the D2 magnet acting as a holding field. The target thickness achieved was 2x1013 atoms/cm2 for one hyperfine state populated in the ABS beam only. With a COSY beam intensity of 6x109 stored polarized deuterons in the ring, the luminosity for double polarized experiments was 1x1029 cm-2 s-1.