The importance of $^{22}$Ne($\alpha$, n)$^{25}$Mg as s-process neutron source and the s-process thermometer $^{151}$Sm

Neutron capture nucleosynthesis provides a sensitive tool for testing He burning scenarios in massive stars as well as in low mass AGB stars. During this phase of stellar evolution nuclei in the mass region between Fe and Bi are producted by the slow neutron capture process ($\emph{s}$-process). Because of the relatively low neutron densities, neutron capture times are long compared to typical $\beta$-half-lives. This implies that the reaction path follows the stability valley and that the resulting abundances are essentially determined by the respective neutron capture cross sections. Hence, these data represent the most important nuclear physics input for $\emph{s}$-process studies. In general, laboratory measurements are required in the energy range 0.1 < E$_{n}$ < 300 keV in order to obtain reliable averages over the stellar Maxwell-Boltzmann distribution for thermal energies between kT=5 keV and 30 keV. The extremely high neutron flux, the energy resolution and the excellent duty factor make the nTOF facility at CERN a unique place for such measurements. This holds in particular if one deals with radioactive samples or with resonance-dominated cross sections. We plan to start our Nuclear Astrophysics programme with two experiments taking advantage of these specific features.