Note: Obtaining reliable cross sections for neutron-induced reactions on unstable nuclei is a highly important task and a major challenge. These data are essential for nuclear astrophysics -since most of the heavy elements in the Universe are produced by neutron-induced reactions in stars- and for applications in nuclear technology. However, their measurement is very complicated as both projectile and target are radioactive. The most promising way to infer these cross sections is to use surrogate reactions in inverse kinematics, where the nucleus formed in the neutron-induced reaction of interest is produced by a reaction involving a radioactive heavy-ion beam and a stable, light target nucleus. The decay probabilities (for fission, neutron and gamma-ray emission) of the nucleus produced by the surrogate reaction provide precious information to constrain models and enable much more accurate predictions of the desired neutron cross sections.
Yet, the use of surrogate reactions is hampered by the numerous long-standing target issues. I propose to solve them by combining surrogate reactions with the unique possibilities at ion storage rings. In a storage ring heavy radioactive ions revolve at high frequency passing repeatedly through an electron cooler, which will greatly improve the beam quality and restore it after each passage of the beam through the internal gas-jet serving as ultra-thin, windowless target. This way, decay probabilities can be measured with unrivaled accuracy.
NECTAR aims to develop a detection system based on cutting-edge technology and a new method to measure accurate decay probabilities of radioactive nuclei at the CRYRING storage ring of the GSI/FAIR facility. The extreme vacuum conditions of the ring put severe constraints on the detection setup. I propose original, even revolutionary options to overcome these issues like the use of solar cells. Thus, NECTAR will be the seed of a new generation of nuclear-reaction experiments with unstable beams.
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