Final Report Summary - PARIS (PARticle accelerators with Intense lasers for Science (PARIS)) Research activities on developing laser plasma accelerators have an unprecedented dynamism. The PARIS ERC AdG project has allowed to literally boost this research field by producing from compact laser system an high quality and tuneable electrons beams. It has been shown that it is possible today to “manipulate collectively” in a robust and reproducible way electrons in a plasma medium to creating an efficient plasma accelerating structure with gigantesque electric fields in the hundred of GV/m. The control in such small time and space scales of electrons in this accelerating structure, by combining cleverly laser beams and/or plasma medium, is the major revolution in accelerator and in plasma domains. This control allow to produce, with a compact 30 TW laser system, an electron beam with relative energy spread of 1%, a duration of less than 2fs [3], a tuneable electron energy from 50 to a few of hundred MeV, and a tuneable charge from the 10-100 pC, to which corresponds a peak current of a few kA. The extreme electric fields produced in the laser plasma accelerators have been used not only to accelerate efficiently electrons, but by taking benefit of their radial component, they have been utilized to make them radiate in the tens to hundreds of keV range. The analysis of this radiation has revealed very interesting features of injection and acceleration mechanisms that were missing to understand deeply the dynamics of beams (laser and electrons) in plasmas. Importantly, these X-ray beams are ultra short and bright enough to envisage pump probe experiments of interest for the study of ultra fast phenomena. In addition to the studies of different injection schemes, new areas of research have been explored regarding the electrons dynamics in relativistic plasma waves, the long time evolution of plasma for ion acceleration, the soliton and the filaments formation that evolve later on after the laser pulse has gone the plasma. A full optical Compton source using a new and elegant scheme has been demonstrated to produce more energetic X ray beam in the hundreds of keV with extreme peak brightness. Theoretical and simulation studies that accompanied the experimental results have allowed to made significant progress in the understanding of the laser plasma interaction in the relativistic regime. In parallel, some unexpected experimental results have also allowed to bring new ideas and to develop new models to explain them. It has also been demonstrated that the electron beam parameters satisfy all the requirements for applications in medicine (radiotherapy), in biology (relevant experiments have shown how cells irradiated recovered after being irradiated by an electron beam delivering an extremely high dose rate), in chemistry (radiolysis), in physics for materials science (gamma radiography), and of course it opens new hope for high energy physics at long term, and at mid term development of compact free electron laser. Regarding midterm perspective the development of compact gamma ray sources for non destructive material inspection with the development of innovative targets have been identified as a clear objective for setting up industrial investigations that have be pursued within the project VERSATILE that has been approved by the ERC in the first Proof of Concept call. This applied research activity is now under the scope of the SourceLab, a Spin-off that has been initiated thanks also to ERC grants.In conclusion, all the aspects of these developments, from the fundamental to their societal applications, have been addressed successfully within the PARIS ERC contract.
