The influence of driven asymmetry on yield degradation in shaped-pulse indirect-drive implosion experiments at the 100 kJ laser facility

The influence of low-mode-driven asymmetry on yield degradation in shaped-pulse indirect-drive implosions has been investigated at the 100 kJ laser facility. In this work, P2- and P4-driven asymmetries were tuned by varying hohlraum gas-fill density and capsule diameter. The measured neutron yield varied from 2.1 x 10(9) to 7.6 x 10(9) and the yield measured by a 1D simulation (YOC1D) was increased from 3% to 16%. Meanwhile, considering the temporal P2- and P4-driven asymmetries, the yields measured by 2D simulations (YOC2D) were from 26% to 81% (the YOC2D of the majority of the shots was higher than 50%). Furthermore, both the ion temperature and neutron bang-time showed good agreement between the measurements and the 2D simulations. The simulations demonstrated that the temporal P2- and P4-driven asymmetries can decrease the efficiency of PdV work and increase the energy loss due to electron thermal conduction. In addition, the internal energy of the deuterium (DD) fuel clearly decreased and the neutron yield was degraded by low-mode asymmetry. In a future work, we will enlarge the cylindrical hohlraum diameter or use an I-hohlraum to improve the low-mode-driven symmetry, along with measurement of the hot-spot shape.

Automated summary

The study found that tuning P2- and P4-driven asymmetries can improve yield in shaped-pulse indirect-drive implosions. 2D simulations showed that, after considering temporal asymmetries, the neutron yield of the majority of shots was over 50%, in line with measurement results. Additionally, the simulations demonstrated that asymmetries can increase energy loss due to electron thermal conduction.