A study of the deuteron breakup reaction pd → (pp)n with forward emission of a fast proton pair with small excitation energy E pp < 3 MeV has been performed using the ANKE spectrometer at COSY-Jülich. An exclusive measurement was carried out at six proton-beam energies T p = 0.6, 0.7, 0.8, 0.95, 1.35, and 1.9 GeV by reconstructing the momenta of the two protons. The differential cross section of the breakup reaction, averaged up to 8 • over the cm polar angle of the total momentum of the pp pairs, has been obtained. Since the kinematics of this process is quite similar to that of backward elastic pd → dp scattering, the results are compared to calculations based on a theoretical model previously applied to the pd → dp process.
The Lamb-shift polarimeter described here enables the polarization of a beam of hydrogen ͑deuterium͒ atoms, or of a slow proton ͑deuteron͒ beam, to be measured with an absolute precision better than 1% within a few seconds. The polarimeter measures the intensity ratios of Lyman-␣ transitions after Stark quenching of metastable hyperfine substates that were selected in a spin filter. For that purpose the hydrogen ͑deuterium͒ atoms are ionized in a Glavish-type ionizer. By charge exchange of the protons ͑deuterons͒ in cesium vapor, atoms in the metastable 2S state are produced. For a hydrogen beam of 3ϫ10 16 atoms/s, ϳ3ϫ10 6 photons/s are registered in a photomultiplier, i.e., the polarimeter efficiency is about 10
Ϫ10. The signal-to-background ratio in the Lyman-␣ 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, therefore, crucial to determine precisely the associated correction factors in order to derive the nuclear polarization from the measured Lyman-␣ spectra.
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