Innovative targets for laser-driven thermonuclear fusion energy: models, simulation, scaled-down experiments

Inertial Confinement Fusion (ICF) offers a promising pathway to clean energy production. A pellet, containing Deuterium and Tritium (DT), is rapidly compressed by irradiation with high power lasers. Following compression, the DT fuel capsule reaches high temperatures and pressures capable of triggering fusion reactions and emitting enough energy before expanding again. Conventional targets for direct-drive laser fusion consist of a spherical plastic shell containing a thin inner layer of frozen deuterium-tritium fuel. Such targets are very expensive to produce and are susceptible to instabilities. In 2020 a new concept has been proposed [V. Goncharov et al., Phys. Rev. Lett. 125, 065001 (2020)] using much simpler homogeneous low density foam balls. In this case, the imploding shell is formed dynamically. A first laser pulse produces an imploding shock wave, which after bouncing from the center turns into a blast wave. Interaction of this blast wave with imploding waves driven by subsequent laser pulses eventually generate the shell, ready to be imploded as in the conventional approach. The work presented in this PhD thesis regards an experimental and computational study of this new concept including a proof-of- principle experiment conducted in 2022 at the OMEGA laser facility (NY,USA). The first part of the thesis is devoted to the study of this new concept through 1D simulations with the hydrodynamic code DUED. The second part presents the work done for the proof-of-principle experiment (both before and after the experiment) based on 1D and 2D hydrodynamic simulations and diagnostic post-processors. Two more technical chapters are also present. The first one concerning a new ray-tracing GPU module for the DUED code, which is needed for the experimental data analysis. The second one is about the tracking of the implosion of plastic capsules using emission X-Ray diagnostics to outline the asymmetries (instabilities) that can arise during dynamical shell formation experiments.