Neutron capture cross sections are the key nuclear physics input to understand nucleosynthesis of the slow neutron capture process (s process). At the neutron time of flight facility n_TOF at CERN neutron capture cross sections of astrophysical interest are measured over a wide energy range. A measurement campaign to determine the stellar (n, gamma) cross sections of Fe and Ni isotopes is currently being pursued. First results on the stellar cross section of 62Ni(n, gamma) confirm previous experimental results. The cross section of the radioactive s-process branching 63Ni was measured for the first time at stellar energies and is about a factor of 2 higher than theoretical predictions. Future facilities and upgrades will allow to access a number of other radioactive nuclides which are crucial for understanding physical conditions of s-process environments.