Direct-Drive Ignition Designs with Gradient-Density Double Shells

Double-shell ignition designs have been studied with the indirect-drive inertial confinement fusion (ICF) in both simulations and experiments [1-3]. Such indirect-drive double-shell designs might provide a viable path to breakeven with a gain of G = 1~3. Since the direct-drive ICF can couple more energy to the in-flight shell, we have performed a study on direct-drive, double-shell ignition designs with our state-of-the-art physics models in DRACO. To mitigate a classical unstable interface, we have proposed using tungsten (W) inner shell with a gradient-density tamper layer of W-doped beryllium (Be) [4]. Due to its high ablation velocity, the Be outer shell is driven symmetrically by a high-adiabat (a = 6-8) laser pulse of 1.8 MJ. Our laser-imprint DRACO simulations indicate that neutron yield energies of 5~10 MJ could be possible with direct-drive, double-shell implosions on NIF-scale facilities. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award No. DE-NA0001944.

[1] P. Amendt et al., Phys. Plasmas 9, 2221 (2002).

[2] J. L. Milovich et al., Phys. Plasmas 11, 1552 (2004).

[3] E. C. Merritt et al., Bull. Am. Phys. Soc. 61, DPP.PO5.3 (2016).

[4] H. Xu et al., Fusion Sci. Tech. 73, 354 (2018).