Speaker
Description
Stopping Power (SP) refers to the dissipative force acting on a charged particle while it moves through a medium, resulting in a deposition of kinetic energy by the incident ion because of the interaction with the surrounding material. Numerous processes simultaneously produce such an energy loss, whose relative incidence depends on the nature and properties of both projectile and target. While the phenomena contributing to the SP in ordinary matter are now sufficiently known to the scientific community, our current understanding of the global dynamics generating the SP in ionized matter is still far from being complete. Therefore, further investigation about this topic becomes of paramount importance in different contexts, like power generation [1] and nuclear astrophysics [2].
Due to its quasi-neutrality condition, in a plasma not only binary (short-range) collisions but also collective (long-range) dynamics must be inevitably considered in the characterization of the interaction with the beam. This latter consists of interrelated electromagnetic phenomena, arising from an effective potential acting between both projectile and target moving charged particles, and representing their mutual influence. In such a frame, not just SP, but a number of strictly correlated effects take place throughout the passage of the beam inside the plasma, like Coulomb Screening (CS), charge stripping and electromagnetic cascades, which all go under the name of “ion damping”. Various approaches were proposed in the last decades [3], but a complete description, able to cover the whole space of plasma parameters, still lacks.
For the validation of the results obtained from numerical simulations (whatever the adopted theoretical model is), SP and, more in general, ion damping measures of ion beams in plasmas are obviously required. An ideal environment where executing such a kind of experimental measurements will be the Laser-Produced Plasmas (LPPs). A LPP is a quasi-neutral state of matter generated from the interaction of a high-intensity laser beam with a target material: from the adsorption of a large fraction of the energy focused on a small area by the high-power and short-duration laser pulse, the evaporation and ionization of the ablated portion of the irradiated matrix are triggered and a high-density, high-temperature and rapidly expanding plasma plume is formed. This strongly concentrated and non-stationary plasma plume can recreate in laboratory the difficult-to-access plasma conditions of both stellar and reactor environments, by employing a relatively simple setup.
In this contribution, we will discuss the possibility to carry out totally innovative energy loss measures of ion beams in strongly transient plasmas, by coupling the THALES femtosecond-scale laser with the INFN-LNS Tandem particle accelerator in the second Interaction Chamber (IC2) of the INFN - Laser indUCEd radiation production (I-LUCE) facility. The availability of the Tandem particle accelerator will ensure the generation of particle bunches with an extremely low initial emittance (or rather, energy spread) if compared to that of laser-produced ion beams. Its proper synchronization with the laser facility will allow to collect data at different stages of the dynamical evolution of the plasma plume, so it will offer the opportunity to explore a wide range of projectile-target interaction regimes. In this way, it may be possible to appreciate and examine the discrepancies between theoretical predictions and experimental evidence at diverse beam-plasma responses.
References
[1] Zhang Y., Ion beam stopping power effects on nuclear fusion reactions, Physics of Plasmas, 2022, DOI 10.1063/5.0103340.
[2] Bertulani C. A., Electronic stopping in astrophysical fusion reactions, Physics Letters B, 2018.
[3] Cayzac W., Ion energy loss at maximum stopping power in a laser-generated plasma, PhD thesis, Université Bordeaux I; Technische Universität Darmstadt, 2013.