Improving Performance and Understanding of Direct-Drive Inertial Fusion Implosions Using Statistical Modeling of Experimental Data

Statistical modeling of experimental and simulation databases [1] has enabled the development of an accurate predictive capability for OMEGA DT layered implosions leading to new target designs and record fusion yields. Neutron yields are currently predicted with 10% accuracy. Improvements to the model formulation [2] have revealed specific dependencies of the yield on adiabat, in-flight aspect ratio, ion-temperature asymmetries, laser beam size, and age of DT fill. This enables corrections of the yield predictions to account for laser mispointing, target offset and age of fill. Statistical modeling has identified that the multiple-pulse driver (MPD) configuration of the OMEGA laser [smoothing by spectral dispersion (SSD)-ON during the initial picket and SSD-OFF during the main drive] results in yield enhancement due to reduction in laser beam size when the driver changes from SSD-ON to SSD-OFF. While the highest yields have been achieved with large size targets, the model indicates that similar yields are possible on smaller targets with appropriate pulse shape modifications. The statistical model has been extended to predictions of areal density but with less accuracy due to large shot to shot variations. Results from statistical analysis and initial MPD campaign are presented. 

[1] V. Gopalaswamy et al., Nature 565, 581 (2019).

[2] A. Lees et al., “Experimentally Inferred Fusion Yield Dependencies in OMEGA Inertial Confinement Fusion Implosions,” submitted to Physical Review Letters.