Increasing the areal density of N210808 implosion with thicker ablators

On August 8, 2021, ignition was finally demonstrated in the laboratory [1-3] on the National Ignition Facility (NIF) in Northern California in the HYBRID-E platform [4-5]. The experiment, N210808, produced a fusion yield of 1.37 MJ from 1.9 MJ of laser energy and has crossed the tipping-point of thermodynamic instability according to several ignition metrics. High areal densities are required to trap the fusion products (alpha particles) for “self” heating of the plasma to reach the conditions for ignition and propagating burn. N210808 burned about 2% of the initial DT fuel and showed variability to unintentional perturbations from changing capsule quality and odd mode asymmetries in follow-on experiments.



This presentation explores designs and preliminary results aimed at increasing the areal density of the hot spot and dense DT fuel piston surrounding the hot spot using thicker diamond ablators. Increasing the areal density is expected to increase the yield amplification and burn-up fraction by trapping more alpha particles and increasing the confinement time. Thicker ablators are also expected to be more robust to unintentional perturbations. We explore 4-8µm thicker HDC ablators (up to 10% thicker than N210808) using laser driver energy of 1.9 to 2.05 MJ. Future designs will also explore using up to 2.2 MJ. A main challenge will be controlling low-mode asymmetries with the thicker targets and longer laser pulses of these designs. Radiation hydrodynamic simulations showing the expected increase in areal density, impact on ignition metrics, and impact on fusion energy production using this configuration will be presented.





[1] to be submitted to Phys. Rev. Lett.

[2] Kritcher et al, to be submitted to Phys. Rev. E

[3] Zylstra et al, to be submitted to Phys. Rev. E

[4] Zylstra et al., Nature 601, 547 (2022)

[5] Kritcher et al., Nature Physics volume 18, 258 (2022)