Feb 12 – 14, 2007
CERN
Europe/Zurich timezone

Exploring the nuclear physics along the rp process path

Feb 13, 2007, 10:00 AM
20m
Council Chamber, 503/1-001 (CERN)

Council Chamber, 503/1-001

CERN

Speaker

Mr Daniel Galaviz Redondo (CSIC)

Description

Type I X-ray bursts, thermonuclear runaways on the surface of an accreting neutron star in a binary system, are one of the known sites for the rapid proton capture process (rp-process)[1,2]. After accumulation of material, mainly hydrogen and helium, on the surface of the neutron star, the triple-alpha reaction triggers a series of fast (a,p) and (p,g) reactions, with subsequent beta decays, that drive the process along the proton-rich side of the valley of stability. The process stops around the Sn-Te region [3], and after ther hydrogen is depleted, the produced nuclei decay B+ and fall onto the surface of the neutron star. Proton capture rates are a key ingredient in the description of the energy release curve associated to X-ray bursts, as well as in the determination of the final isotopic abundance distribution [4]. In order to reduce the uncertainties in the determination of (p,g) reaction rates, several experiments were performed at the National Superconducting Cyclotron Laboratory (NSCL) at the Michigan State University, using radioactive beams, to determine precisely the level structure above the proton threshold of rp process nuclei. This work presents the experimental approach and the set-up at the NSCL, which involves the S800 Spectrograph and the Segmented Germanium Array (SeGA), as well as the first results obtained with this technique. Implications of the new results in the astrophysical rp process are also discussed. [1] R. K. Wallace, and S. E. Woosley, Astrophys. J. (Suppl.) 45, 389 (1981) [2] H. Schatz et al., Phys. Rep. 294, 167 (1998) [3] H. Schatz et al., Phys. Rev. Lett. 86, 3471 (2001) [4] J. L. Fisker et al., Astrophys. J. Lett. 608L, 61 (2004)

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