First steps towards atomic physics of Fast Ion – Slow Ion Collisions – Fit-FISIC

Knowledge of the fundamental mechanisms at stake in fast ion – slow ion collision in atomic physics can provide a real breakthrough in the understanding of energy transfers in various plasmas such as inertial confinement fusion plasmas or stellar/interstellar plasmas. Indeed, ion-ion collisions are one of the widespread phenomena in the universe but the least studied in laboratory. Crossing two multicharged ion beams, under well controlled conditions, has always been a very challenging task, whatever the domain of physics under consideration, such as in particle physics at CERN. So far, ion-ion collisions for atomic physics have been performed mainly in the context of magnetically confined plasmas using crossed beam device in the low-energy domain where the charge transfer is the dominant process. Measurements and reliable theoretical predictions are completely lacking for fast ion-slow ion collisions, a regime in which ion stopping power is maximum, and all the primary electronic processes (electron capture, loss and excitation) reach their optimum. It corresponds to a real “terra incognita” for atomic physics.
The forthcoming availability of intense and stable beams of high optical quality on French and German Large Scale Facilities opens new challenging opportunities to probe a variety of systems of prime importance for applications. In addition from the stringent tests of theories provided by these fundamental studies, we can anticipate that such kind of experiments will lead to valuable upstream information relevant for societal issues. For instance, the description, at the atomic level, of material modification (including biological material) at the maximum of ion energy deposition– the so-called intermediate regime – is crucial for understanding the physics of radiation damage.
The Fit-FISIC project proposes to overcome a lot of technical barriers which have so far limited the progress in studies of such simple systems. The ultimate goal is to control the experimental conditions and to span from a pure three-body problem (collision between a bare ion and a hydrogenic target) to a collision system between dressed partners (study of the effect of a controlled number of additional electrons, such as electronic correlations). The main aim of this project is to build a unique crossed beam ion – ion experiment to perform absolute cross section measurements. Among the most severe bottlenecks that should be overcome, we can stress the resistance of the target for stripping of the high energy ion beam; the control of the overlap of the crossed beams or the mastership of the overall experimental conditions to optimize the multi-coincidence event detection.
The collaboration built within this project with two French and two German partners is particularly well arrayed to take up this challenge with very specific skills but also a long-standing tradition of collaboration. Led by the INSP laboratory, this consortium joins the effort of different groups well recognized on an international level in different fields of physics from plasma physics to ion – matter interaction.