During the past decades Synchrotron Radiation facilities have seen an impetuous growth as a fundamental tool for the study of materials in a wide spectrum of sciences, technologies, and applications. The latest generation of light sources, the Free Electron Lasers, capable of delivering high-intensity photon beams of unprecedented brilliance and quality, provide a substantially novel way to probe matter and have very high, largely unexplored, potential for science and innovation. Currently, the FELs operating in EU are three, FERMI, FLASH and FLASH II, operating in the soft X-ray range and two are under commissioning, SwissFEL and EuroXFEL, which will operate in the hard X-ray scale. While most of the worldwide existing FELs use conventional normal conducting 3 GHz S-band linacs, others use newer designs based on 6 GHz C-band technology, increasing the accelerating gradient with an overall reduction of the linac length and cost. With CompactLight we intend to design a hard X-ray FEL facility beyond today’s state of the art, using the latest concepts for bright electron photo injectors, very high-gradient X-band structures at 12 GHz, and innovative compact short-period undulators. If compared to existing facilities, the proposed facility will benefit from a lower electron beam energy, due to the enhanced undulator performance, be significantly more compact, as a consequence both of the lower energy and of the high-gradient X-band structures, have a much lower electrical power demand and a smaller footprint. CompactLight gathers the world-leading experts in these domains, united to achieve two objectives: disseminate X-band technology as a new standard for accelerator-based facilities and advance undulators to the next generation of compact photon sources, with the aim of facilitating the widespread development of X-ray FEL facilities across and beyond Europe by making them more affordable to build and to operate.

Particle accelerators are a key asset of the European Research Area. Their use spans from the large installations devoted to fundamental science to a wealth of facilities providing X-ray or neutron beams to a wide range of scientific disciplines. Beyond scientific laboratories, their use in medicine and industry is rapidly growing. Notwithstanding their high level of maturity, particle accelerators are now facing critical challenges related to the size and performance of the facilities envisaged for the next step of particle physics research, to the increasing demands to accelerators for applied science, and to the specific needs of societal applications. In this crucial moment for accelerator evolution, I.FAST aims at enhancing innovation in and from accelerator-based Research Infrastructures (RI) by developing innovative breakthrough technologies common to multiple accelerator platforms, and by defining strategic roadmaps for future developments. I.FAST will focus the technological R&D on long-term sustainability of accelerator-based research, with the goal of developing more performant and affordable technologies, and of reducing power consumption and impact of accelerator facilities, thus paving the way to a sustainable next-generation of accelerators. By involving industry as a co-innovation partner via the 17 industrial companies in the Consortium, 12 of which SME’s, I.FASTwill generate and maintain an innovation ecosystem around the accelerator-based RIs that will sustain the long-term evolution of accelerator technologies in Europe. To achieve its goals, I.FAST will explore new alternative accelerator concepts and promote advanced prototyping of key technologies. These include, among others, techniques to increase brightness and reduce dimensions of synchrotron light sources, advanced superconducting technologies to produce higher fields with lower consumption, and strategies and technologies to improve energy efficiency.