80 years of experimental photo-fission research

High energy photons, or γ -rays, were among the very first probes used to induce fission. Their significant impact in this field is due to particular properties of the γ -rays, such as the lack of a Coulomb barrier and the low, well-defined angular momentum transfer, but also to the variety of γ -ray sources developed over the years. This variety, going from simple but intense bremsstrahlung beams, through complex virtual photon excitations, to high resolution monochromatic sources of several types, gave rise to extensive photo-fission research programs. The review presents the evolution over more than 80 years of the methodology and instrumentation used in photo-fission experiments. The most important developments in fundamental and applied science are summarized and discussed. The main improvements necessary for the progression of this field into the age of nuclear photonics are outlined.