  The Gamma Factory initiative proposes to develop novel research tools at CERN
by producing, accelerating and storing highly relativistic, partially stripped
ion beams in the SPS and LHC storage rings. By exciting the electronic degrees
of freedom of the stored ions with lasers, high-energy narrow-band photon beams
will be produced by properly collimating the secondary radiation that is peaked
in the direction of ions' propagation. Their intensities, up to $10^{17}$
photons per second, will be several orders of magnitude higher than those of
the presently operating light sources in the particularly interesting
$\gamma$--ray energy domain reaching up to 400 MeV. This article reviews
opportunities that may be afforded by utilizing the primary beams for
spectroscopy of partially stripped ions circulating in the storage ring, as
well as the atomic-physics opportunities afforded by the use of the secondary
high-energy photon beams. The Gamma Factory will enable ground breaking
experiments in spectroscopy and novel ways of testing fundamental symmetries of
nature.
