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Nucleosynthesis of the chemical elements during the evolution of stars is the basis for understanding the chemical history of the Universe. All the elements heavier than iron are produced by neutron capture reactions. The neutron capture cross sections for certain isotopes constrain stellar parameters on the one hand, and also lead to strong constraints on the age of the Universe. nucleosynthesis

Figure 1: The path of the s process between Iron and Zirkonium.

NAUTILUS will focus on investigating a particularly interesting region in the chart of nuclides. Accurate measurements of the key nuclear reactions in the region around 85Kr will lead to the necessary improvements for characterizing the production processes of the elements in stars to the point where the respective abundance patterns can be interpreted as diagnostic tools for the deep stellar interior and the history of the universe. cosmology

Figure 2: Determination of the age of the universe.


The neutron capture cross section of radioactive isotopes for neutron energies in the keV region will be measured by a time-of-flight (TOF) experiment. NAUTILUS will provide a unique facility realizing the TOF technique with an ultra-short flight path at the FRANZ setup at Goethe-University Frankfurt am Main, Germany. A highly optimized spherical photon calorimeter will be build and installed at an ultra-short flight path. schematic setup

Figure 3: Schematics of the experimental setup.


This new method allows the measurement of neutron capture cross sections on extremely small sample as needed in the case of 85Kr, which will be produced as an isotopically pure radioactive sample. The successful accomplishment of NAUTILUS will provide insights into the dynamics of the late stages of stars, an important independent check of the evolution of the Universe and the proof of principle of a new method determining neutron capture cross section on extremely small samples. 85Kr production

Figure 4: Production of 85Kr via α-irradiation of 82Se.