Direct-drive target designs as energetic particle sources for the Laser MégaJoule facility

This work aims to analyse the possibility of directly driven imploding spherical targets in order to create a source of energetic particles (neutrons, protons, alphas, tritium and ³He ions) for the Laser MégaJoule facility. D³He gas-filled spherical SiO₂ glass pellets, irradiated by an absorbed laser intensity of 10¹⁴ W cm⁻² or 10¹⁵ W cm⁻² have been considered. Depending on the absorbed laser intensity and the amount of the ablated glass layer two distinct regimes have been identified: a massive pusher and an exploding pusher. Both regimes are analysed in terms of hydrodynamics and fast particle spectra. Energetic particle time-resolved spectra are calculated and used to infer ionic temperatures and total areal densities. A parametric study has been performed by varying the shell thickness and target inner radius for both laser absorbed intensities.