NU-RING · NUclear reactions at RINGs

Neutron-induced cross sections of short lived nuclei are key quantities in many domains, such as fundamental nuclear physics, astrophysics and applications in nuclear technology. However, the difficulties to produce and manipulate the necessary amounts of radioactive nuclei make the measurement of such cross sections with current techniques extremely difficult or even impossible. Surrogate reactions in inverse kinematics represent the most promising indirect approach to determine these cross sections: The excited nucleus of interest is produced by a different reaction than the neutron-induced reaction. The measured decay probabilities strongly constrain model parameters enabling accurate predictions of the desired neutron cross section. We propose to combine surrogate reactions with the unique possibilities at ion storage rings, which are high-precision tools to study nuclear reactions in inverse kinematics with radioactive ion beams. The advantages range from greatly improved beam properties over the absence of target contaminants and backings, and a strong reduction of the straggling, thanks to the use of pure, windowless and ultra-thin targets. However, the demanding vacuum conditions of storage rings put severe constraints on the detection setup. In addition, it is necessary to validate this completely new methodology by comparing first results with good-quality data measured in direct kinematics. Still, there is a lack of direct-kinematics data that can be used as benchmark.We propose to perform simulations to define the set-up for the first surrogate-reaction measurements at the storage rings of the GSI facility. We will also investigate innovative solutions to overcome the vacuum issues like the use of solar cells. Finally, we will measure the 208Pb(d,d’) reaction in direct kinematics, which is one of the best suited cases to be used as benchmark.With Nu-Ring we will set the basis to establish a cutting-edge technology for the study of surrogate reactions.