Surrogate Reactions at Heavy-Ion Storage Rings and Solar Cells StudiesONLINE ONLY

Neutron-induced reaction cross sections of unstable nuclei are essential for understanding the synthesis of heavy elements in stars and for applications in nuclear technology. However, their direct measurement is very complicated due to the radioactivity of the targets involved. In the frame of the NECTAR (Nuclear rEaCTions At storage Rings) project, we propose to circumvent this problem by combining the surrogate reaction method in inverse kinematics with the unique possibilities of storage rings. In surrogate reactions in inverse kinematics the compound nucleus formed in the neutron-induced reaction of interest is produced by an alternative or surrogate reaction involving a radioactive heavy-ion beam and a stable light target nucleus. The probabilities as a function of the compound-nucleus excitation energy for gamma-ray emission, neutron emission and fission, which can be measured with the surrogate reaction, are particularly useful to constrain fundamental model parameters that describe the de-excitation of the compound nucleus and significantly improve the predictions of the neutron-induced reaction cross sections of interest.

In this talk, I will present the first successful surrogate reaction experiment performed at the Experimental Storage Ring (ESR). In this experiment we used the inelastic scattering 208Pb(p,p') reaction as a surrogate reaction for the neutron-capture reaction of 207Pb. With our new experimental set-up we were able to simultaneously measure for the first time both the gamma- and neutron-emission decay probabilities of the compound nucleus 208Pb. The obtained results allowed us to validate our new methodology and demonstrate the significant advantages of storage rings, which enable the measurement of the excitation energy with high precision and a dramatic increase of the detection efficiencies for inferring the gamma and neutron emission probabilities. I will also present a comparison between our results for the decay probabilities and calculations performed with the reaction code TALYS.

In the second part of my talk, I will present our recent studies aimed to investigate the use of solar cells as heavy ion detectors at storage rings. I will show the results of an experiment performed at GANIL where we investigated the response of solar cells to a heavy ion beam of different energies and intensities. I will also describe the simulations I performed to understand the charge collection process in solar cells.

These two topics constitute my PhD thesis.