Speaker
Description
Defined as a quasi-neutral ionized gas, plasma is a state of aggregation exhibiting emergent collective behavior. Although it is often treated as a whole component of ordinary matter, of which it represents more than 99% [1], a large variety of plasma exists, distinguished through density, temperature, species concentrations (or charge state), and dimensions.
Moreover, plasmas behave as complex systems showing a high correlation index and most of them undergo strong dynamic evolutions in time and space. Hence, while their description is normally confined within the assumptions of local thermodynamic equilibrium (LTE), it must account for mutual interactions among the particles.
Despite critical complexities, modeling transient plasmas is a challenge to be faced in the near future, being a forced step in many areas of physics, such as magnetohydrodynamics (in magnetic reconnections), nuclear astrophysics (in stellar evolution), nuclear fusion (both in reaction ignition and plasma-facing interactions [2]) and device development (for instance in laser etching and ablation). Moreover, the remarkable features of far-from-equilibrium plasmas may be applied to the problem of lithium production during Big Bang nucleosynthesis [3].
Measuring the stopping power (SP) exerted on a charged particle beam while it passes through a transient plasma, it is possible to probe the complex interactions within its constituents. In fact, due to the great availability of states and phenomena that occur in plasma, SP behaves differently than in solid matter.
To evaluate the quantitative deviations from previous models in stationary conditions, our work focuses on modelling SP in strongly transient plasmas, starting from the high-precision description of laboratory-produced plasmas dynamics to account for the non-linear contribution of self-interaction phenomena.
First, the time evolution of a plasma plume produced by laser ablation (Laser Produced Plasma, LPP) will be presented in comparison with experimental measurements performed at INFN-LNS, Catania. This differs significantly from previous expectations, such as the Anisimov model [4], because, in addition to thermodynamics, it considers the overall electromagnetic corrections [5]. Then, we will discuss how to resolve the motion of charged particles affected by SP within LPPs, whose charge state is defined through 0D volume-average model [2], by solving partial differential equations on a dynamical boundary; a comparison with experimental data is already planned at LENS experimental equipment by LNS.
In conclusion, we expect cross-cutting implications in many areas of physics involving precision calculations on far-from-equilibrium plasma; moreover, the know-how acquired in these activities will contribute to the research activities carried out at the future I-LUCE [6] facility of INFN-LNS.