A physics-based statistical mapping approach to understand and improve the performance of inertial confinement fusion implosions on OMEGA

Aarne Lees PhD Defense, Advised by Professor’s Hussein Aluie and Riccardo Betti

Thursday, September 29, 2022
11 a.m.

Improving the performance of inertial confinement fusion implosions requires physics models that can accurately predict the response to changes in the experimental inputs. Good predictive capability has been demonstrated for the fusion yield using a statistical mapping of simulated outcomes to experimental data. [V. Gopalaswamy et al., Nature 565, 581-586 (2019)]. In this thesis, a physics-based statistical mapping approach is used to extract and quantify all the major sources of degradation of fusion yield and areal density in direct-drive implosions on the OMEGA Laser. The fusion yield is found to be dependent on the age of the deuterium tritium fill, the L = 1 asymmetry in the implosion core, the laser beam to target size ratio, and parameters related to the hydrodynamic stability. The inferred dependencies are compared to simulations and, in the case of the fill age dependency, a controlled set of dedicated experiments. Results from experiments designed with the aid of the statistical mapping model to optimize the target size on OMEGA are shown. A mapping of the areal density of OMEGA implosions reveals a strong degradation in highly convergent implosion designs. Dedicated experiments in both planar and spherical geometries were used to measure the kinetic energy of the shock release in order to assess the impact of shock release on the convergence of ICF implosions. No indication was found that the shock release could be responsible for the lack of convergence observed in experiments.