I will discuss two nuclear processes having great astrophysical
interest focusing the attention both on experimental technique
and on the astrophysical consequences. The first nuclear reaction
is the 14N(p,g)15O,
which is of great interest because this reaction represents the
bottleneck of the CNO cycle, which in turn has a large influence
on the determination of the age of globular clusters and also
plays a role in the estimate of the Solar neutrino fluxes. I will
report on the measurements performed at the LUNA underground facility
accelerator.
The second process is the 12C(a,g)16O,
which is, together with the triple-a process, the main process
of the helium burning. This capture cross-section at the relevant
Gamow energy determines - together with the convection mechanism
at the edge of the stellar core - the abundances of carbon and
oxygen at the end of helium burning. This, in turn, strongly influences
the nucleosynthesis of elements up to the iron region for massive
stars and the composition of CO white dwarfs, whose progenitors
are intermediate and low-mass stars. I will report on the measurement
perfomed in the framework of ERNA experiment, using the recoil
mass separator technique. Finally, I will give some outlooks for
future experiments.