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Neutron cAptUres consTraIning steLlar nUcleosynthesiS

Final Report Summary - NAUTILUS (Neutron cAptUres consTraIning steLlar nUcleosynthesiS)

The goal of the NAUTILUS project was twofold. The first goal was to proof that it is possible to determine likelihood of a capture reaction of neutron when passing through a known sample using the time-of-flight method in conjunction with a flight path of only a few centimeters. The second goal was to determine this likelihood for the radioactive isotope Kr-85. This reaction is important for our understanding of the nucleosynthesis of the heavier elements in stars. A detailed analysis based on accurate knowledge of the nuclear physics variables allows deep insights into Red-Giant stars and it allows to constrain the age of the universe.

The application of the time-of-flight method requires the detection of the high-energy photons following the neutron captures. The design of a new high-energy photon detector was finalized at the beginning of the project and the construction was finished during the last year of the project. The improvements compared to detectors used so far and the applicability of the proposed technique could be shown in a series of tests.

The fabrication of the radioactive Kr-85 sample was finished the second year. The methods developed during this process were successfully applied to other noble gases too. First time-of-flight measurements were performed on contaminants abundant in the sample. The neutron capture cross section of Kr-85r has been investigated for the first time using the time-of-flight method.

Most of the nuclear physics parameters important for the understanding of the nucleosynthesis in the krypton region are now based on experimental data. A general paper on the abundance of radioactive nuclides in the Universe has just been accepted.