H. Seyfarth

ANKE, a new facility for medium energy hadron physics at COSY-Jülich

Abstract ANKE is a new experimental facility for the spectroscopy of products from proton-induced reactions on internal targets. It has recently been implemented in the accelerator ring of the cooler synchrotron COSY of the Forschungszentrum Julich (FZ-Julich), Germany. The device consists of three dipole magnets, various target installations and dedicated detection systems. It will enable a variety of hadron-physics experiments like meson production in elementary proton–nucleon processes and studies of medium modifications in proton–nucleus interactions.

Precision Lamb-shift polarimeter for polarized atomic and ion beams

The Lamb-shift polarimeter described here enables the polarization of a beam of hydrogen (deuterium) atoms, or of a slow proton (deuteron) beam, to be measured with an absolute precision better than 1% within a few seconds. The polarimeter measures the intensity ratios of Lyman-α transitions after Stark quenching of metastable hyperfine substates that were selected in a spin filter. For that purpose the hydrogen (deuterium) atoms are ionized in a Glavish-type ionizer. By charge exchange of the protons (deuterons) in cesium vapor, atoms in the metastable 2S state are produced. For a hydrogen beam of 3×1016 atoms/s, ∼3×106 photons/s are registered in a photomultiplier, i.e., the polarimeter efficiency is about 10−10. The signal-to-background ratio in the Lyman-α spectrum is excellent, thus beam intensities of one to two orders of magnitude less would still be sufficient to carry out a precise measurement. The different components of the polarimeter affect the measured polarization in several ways. It was, t...

Polarizing a Stored Proton Beam by Spin-Flip?

We discuss polarizing a proton beam in a storage ring, either by selective removal or by spin flip of the stored ions. Prompted by recent, conflicting calculations, we have carried out a measurement of the spin-flip cross section in low-energy electron–proton scattering. The experiment uses the cooling electron beam at COSY as an electron target. The measured cross sections are too small for making spin flip a viable tool in polarizing a stored beam. This invalidates a recent proposal to use co-moving polarized positrons to polarize a stored antiproton beam.

The neutron-proton charge-exchange amplitudes measured in the dp → ppn reaction

Abstract.The unpolarised differential cross section and the two deuteron tensor analysing powers Axx and Ayy of the

Determination of deuteron beam polarizations at COSY

\vec dp \to \{ pp\} _s n

Measurement of the analyzing power in p-->d-->(p p)n with a fast forward 1S0 proton pair.

charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27GeV, data were obtained for small momentum transfers to a {pp}s system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters Cx,x and Cy,y that were carried out in the

The polarized H and D atomic beam source for ANKE at COSY-Jülich

\vec d\vec p \to \{ pp\} _s n