A unique probe for nuclear structure in a future European radioactive ion –electron collider: Contribution to the NuPECC Long Range Plan (LRP) 2024 for Nuclear Physics in Europe

Electron scattering on radioactive nuclei could provide nuclear observables with an unprecedented radial sensitivity for exotic systems. In these nuclei, unique quantum phenomena occur but basic properties such as charge densities are still completely unknown. Precise densities extracted from the scattering data could be confronted to modern structure calculations. Such studies would provide better insight both on the accuracy of the many-body treatment of the new techniques and on the validity of the microscopic characteristics of realistic nuclear interactions used in state-of-the-art nuclear models.Our goal is to build an electron beam accelerator implanted at a facility providing a variety of radioactive ion beams (RIBs), such as GANIL, to perform electron-radioactive ion (e-RI) collisions and measure cross sections and excitation spectra. The measurements of electron scattering can be renewed taking advantage of the combined progress done in the fields of theory, accelerator techniques and experiments.Developments in the accelerator design and electron-ion collision techniques would offer the increased luminosities required for the project from 10$^{26}$ up to 10$^{28-29}$ cm$^{-2}$.s$^{-1}$ for the main physics cases of the first step, expanding to 10$^{29-31}$ cm$^{-2}$.s$^{-1}$ in the long-term range for the inelastic form factors