Tailored Drive Asymmetry in ICF Implosions for Reduced In-flight Shell Swing and Improved ρR Uniformity

Symmetry control remains a persistent challenge in inertial confinement fusion (ICF) implosions at the National Ignition Facility (NIF), which has only been exacerbated by recent design changes [1] that have led to improved energy coupling and fusion performance. The main technique for adjusting implosion symmetry, cross-beam energy transfer driven by wavelength separation (Δλ) between the outer and inner beams, can be leveraged, up to a point, to maintain a round hotspot at stagnation. However, increasing Δλ comes at the cost of worsening “swings,” or time-dependent asymmetries, in the x-ray drive that can induce non-radial flows in the imploding shell, leading to thin spots of low ρR that reduce confinement of the hot fusion plasma and “residual” kinetic energy in the shell that remains unconverted to hotspot internal energy. This work discusses how tailored drive asymmetry [2, 3] in the early phases of the implosion can counteract the unavoidable asymmetry later, producing a more uniform imploding shell that leads to improved fusion performance in radiation-hydrodynamic simulations. This tactic is in progress of being tested in two campaigns on NIF using 2.05 MJ and 2.2 MJ of laser drive energy, with the potential to improve fusion performance over current records by increasing confinement and burnup fraction of the deuterium-tritium fuel.



[1] A. L. Kritcher et al., Phys. Rev. E 109, 025204 (2024)

[2] J. Gu et al., Phys. Plasmas 22, 122704 (2015)

[3] L. Masse et al., Phys Plasmas 26, 062703 (2019)