Experimentally Inferred Fusion Yield Dependencies of OMEGA Inertial Confinement Fusion Implosions

Statistical modeling of experimental and simulation databases has enabled the development of an accurate predictive capability for deuterium-tritium layered cryogenic implosions at the OMEGA laser [V. Gopalaswamy et al.,Nature 565, 581 (2019)]. In this letter, a physics-based statistical mapping framework is described and used to uncover the dependencies of the fusion yield. This model is used to identify and quantify the degradation mechanisms of the fusion yield in direct-drive implosions on OMEGA. The yield is found to be reduced by the ratio of laser beam to target radius, the asymmetry in inferred ion temperatures from the $\ell =1$ mode, the time span over which tritium fuel has decayed, and parameters related to the implosion hydrodynamic stability. When adjusted for tritium decay and $\ell =1$ mode, the highest yield in OMEGA cryogenic implosions is predicted to exceed $2\times {10}^{14}$ fusion reactions.

Figure 1

Measured YOC versus that predicted by the mapping model [Eq. (7)] with the power indices given in Table 1. The horizontal error bars represent the uncertainty in measured $T_i$ asymmetry and fuel composition.

Figure 2

The individual degradations due to (a) $\ell =1$ mode, (b) ${}^3\mathrm{He}$ accumulation in the vapor, (c) finite beam size, and (d) hydrodynamic instabilities extracted from the OMEGA database according to Eq. (8). The dashed lines indicate the power laws from the model; the power indices are given in Table 1.

Figure 3

Measured neutron yield corrected for $T_i$ asymmetry and ${}^3\mathrm{He}$ accumulation versus yield predicted by calculating the degradation given by Eq. (7) with ${\xi }_{\mathrm{He}}={\widehat{R}}_T=1$.