Multi-objective data analysis of performance-degradation trends in ICF implosions, and implications for hydro-scaling to ignition conditions*

Multi-objective data analysis is of increasing interest to the ICF community since the multi-faceted causes of implosion-performance degradation are not yet fully identified. This type of technique for analyzing data from cryogenic DT implosions takes simultaneously into account trends in all experimental observables, therefore, providing leads for investigating the cause of the performance degradation and systematic errors in the measurements. This work is based on a concept-driven analysis of degradation trends in the implosion observables, arising from low- (ℓ<6) and mid-mode (6<ℓ<40) asymmetries, and 1-D degradations.  The analysis technique was first applied to an ensemble of cryogenic DT implosions that generated hot-spot pressures of ~50 Gbar. The 1-D physics models had been previously adjusted for these implosions. All experimental observables pertaining to the core could be reconstructed with the same combination of low and mid modes, suggesting a systematic and repeatable mechanism causing the performance degradation. In addition to low modes, which cause degradation of the stagnation pressure, it is found that mid modes are present and that they reduce the size of the neutron and x-ray producing volumes, and augment the measured areal density. The mid modes are most likely introduced by laser drive non-uniformity caused by the superposition of the 60 laser beams on OMEGA. A discrepancy between measured and simulated burn width and bang time was also observed, suggesting a systematic error in the measurements. Correcting for these low- or mid-mode asymmetries would increase the hot-spot pressure from 56 Gbar to ~80 Gbar at OMEGA, and generate a burning plasma when hydro-scaled to 2 MJ direct illumination. Recently, the technique was used to analyze the low converging direct-drive implosions which brought to light general inconstancies in the 1-D physics models.