Köln 2004 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 48: Nuclear and Particle Astrophysics IV

HK 48.10: Vortrag

Donnerstag, 11. März 2004, 18:45–19:00, F

A neutron source for activation measurements in a stellar spectrum at kT=8 keV — •Michael Heil¹, S. Dababneh¹, F. Käppeler¹, S. O’ Brien², R. Plag¹, and R. Reifarth³ — ¹Forschungszentrum Karlsruhe, Institut für Kernphysik, Postfach 3640, D-76021 Karlsruhe, Germany — ²Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA — ³Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

Since 1980 the ⁷Li(p,n)⁷Be reaction was intensively used for activation measurements. With a proton energy of E_p=1911 keV the resulting neutron spectrum resembles a Maxwell-Boltzmann distribution with a thermal energy of kT=25 keV. Therefore, this neutron source is ideal to determine Maxwellian-averaged neutron capture cross sections (MACS) close to a temperature of 250 million Kelvin (kT=23 keV) which is typical for the s process in red giant stars. Meanwhile, detailed stellar models indicate that the dominant neutron exposure of the main s-process component in low mass AGB stars takes place at a lower temperature of 90 million Kelvin (kT=8 keV). In order to supply the necessary reaction rates for the stellar models the values at 25 keV have to be extrapolated to the lower thermal energy, introducing additional uncertainties. In this contribution we report on a neutron source which allows to produce a Maxwell-Boltzmann spectrum close to the lower thermal energy of kT=8 keV.