Experimentally Inferred Dependencies of the Ion Temperature, Areal Density, and Fusion Yield in OMEGA Direct-Drive Implosions

Statistical modeling [1] of OMEGA direct-drive implosions has provided an accurate predictive capability for designing high-performance implosions achieving record neutron yields up to 3.1 x 10¹⁴. Other relevant implosion performance parameters are the ion temperature and the areal density. A physics-based statistical model [2] of the fusion yield has revealed the different dependencies of the measured neutron yield. The relevant dependencies include the age of the DT fill (a proxy for the He³ accumulation), the apparent ion-temperature asymmetries (a proxy for the L = 1 mode from target offset and laser mispointing), the ratio of the laser-beam radius to the target radius (a proxy for mid-modes from the laser illumination pattern), and hydro-stability parameters such as adiabat and in-flight aspect ratio, which govern the stability to short wavelength modes from laser imprinting and surface roughness. A similar statistical analysis has been carried out for the ion temperature and areal density. It is shown that all the measured stagnation properties exhibit dependencies on parameters similar to those used to predict the fusion yield. Having different measured properties leading to similar dependencies further validates the statistical analysis and provides a more-accurate tool for designing higher-performance implosions.

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

[2] A. Lees et al., Phys. Rev. Lett. 127, 105001 (2021).