Gamma factory: the light into the future

The Gamma Factory (GF) is an ambitious CERN proposal for a source of photons with energies up to about 400 MeV and photon uxes up to 10 17 photons per second, exceeding those of the currently available gamma sources by orders of magnitude. The high-energy (secondary) photons are produced via resonant scattering of the primary laser photons by highly relativistic partially-stripped ions circulating in the accelerator. The secondary photons are emitted in a narrow cone and the energy of the beam can be monochromatized, eventually down to the ppm level, via collimation, at the expense of the photon ux. In this contribution honoring Professor Swapan Chattopadhyay, we highlight the concept of the GF and some of the opportunities offered by the GF in fundamental physics across many subfields.