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. We propose to circumvent this problem by using the surrogate reaction method in inverse kinematics, where 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 the first part of this thesis work, the first proof of principle experiment conducted within the frame of the NECTAR (Nuclear rEaCTions At storage Rings) project is described. In this experiment, a surrogate reaction in inverse kinematics was combined for the first time with the unique possibilities at heavy-ion storage rings. This measurement took place at the Experimental storage ring (ESR) of the GSI/FAIR facility (Germany), where the inelastic scattering 208Pb(p,p’) reaction was used 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 gamma-ray and neutron emission. In addition, the comparison of the measured probabilities with the statistical model implemented in the Talys code has allowed us to gain insight into the de-excitation process of 208Pb*. Storage rings are operated in ultra-high vacuum (UHV) conditions (10-10-10-11 mbar), a pressure level four to five orders of magnitude lower than in standard experiments. This sets severe constrains for in-ring detection systems. For this reason, UHV-compatible silicon detectors have started to be used for in-ring experiments only recently. In this work, we propose a completely new solution based on the use of solar cells, which represent an interesting option for the use in storage rings thanks to their radiation hardness. The second part of this thesis describes the studies we have performed to study the feasibility of using solar cells for the in-ring detection of heavy ions. We performed an experiment at GANIL facility (Caen, France) with a 84Kr beam of energies ranging from 5 to 15 MeV/u to investigate the response of solar cells and their radiation resistance. Our results reflect the good performances of solar cells in terms of energy resolution (about 1 % RMS) and time resolution (about 2.5 ns FWHM) and their larger radiation resistance compared to silicon detectors. In parallel, we studied their UHV compatibility with our test bench TREVO (Test line foR Extreme Vacuum Observations), which has provided very promising results, e.g. a low outgassing rate of 5,2 ∙ 10-13 (mbar∙l)/(s∙cm2) for an individual cell.
