Program - Brookhaven National Laboratory

LB 2 4:00 PM
Nuclear Spectroscopic Data for Nuclear Astrophysics
P.J. Woods, G. Lotay, D.T. Doherty, H.M. David
Edinburgh University
D. Seweryniak, M.P. Carpenter, C.J. Chiara, R.V.F. Janssens, S. Zhu
Physics Division, Argonne Nat. Laboratory
The talk will consider spectroscpic measurements at the interface between nuclear astrophysics and nuclear
structure (see [1] for a recent example). In particular the talk will focus on high resolution studies of key
resonances relevant for elemental emissions from novae explosions, and cosmic gamma ray emitters. In
particular there will be an emphasis on work performed using the Gammasphere array at Argonne National
Laboratory and how these studies are complemented and built on by other techniques.
[1] D.T. Doherty et al., Phys. Rev. Lett. 108 262502 (2012)
LB 3 4:20 PM
Neutron Capture Reactions for the Astrophysical s-process in the Fe/Ni Region
Claudia Lederer, Oliver Meusel, Ralf Plag, Rene Reifarth, Kerstin Sonnabend, Goethe University
Frankfurt, Germany. Nicola Colonna, INFN Bari, Italy. Carlos Guerrero, CERN, Switzerland. Frank
Gunsing, CEA Saclay, France. Franz Kaeppeler, Karlsruhe Institute of Technology, Germany. Cristian
Massimi, INFN Bologna, Italy. the n TOF Collaboration, www.cern.ch/ntof.
Nuclear reaction data provide a crucial input to study the generation of elements in the cosmos. Elements
heavier than Fe are mainly synthesized by neutron capture reactions, which can be divided in two processes,
the slow neutron capture process (s-process) and the rapid neutron capture process (r-process). The sprocess
takes place in environments of relatively small neutron densities and the reaction path proceeds
close to the valley of stability. The r-process is attributed to scenarios with very high neutron densities,
driving the reaction path towards the neutron rich side. The s-process abundances are strongly correlated
to their stellar neutron capture cross sections, that is the energy dependent cross section averaged over
the stellar neutron spectrum. Such cross sections can be measured directly via time-of-flight techniques or
activating the material with a quasi-stellar neutron spectrum produced in the laboratory. I will present
recent measurements of (n, γ) reactions in the Fe/Ni mass region studied by the time of flight technique
at the n TOF facility at CERN, including the measurement on the radioactive nucleus 63 Ni. The neutron
time-of-flight facility n TOF is a spallation neutron source, combining a high instantaneous neutron flux
with a high energy resolution due to its neutron flight path of 185 m. Neutrons are produced from thermal
energies to several GeV, covering the entire energy range of astrophysical interest. Neutron captures
reactions are measured via detecting the prompt γ-emission of the compound nucleus. Furthermore, I
will talk about the complementary activation technique and new possibilities for both methods at the
highly intense neutron source FRANZ (Frankfurt Neutron Source of the Stern Gerlach Zentrum), which is
currently under construction at the University of Frankfurt.
LB 4 4:40 PM
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