NIF Invited: “What Next: Further Implosion Space Exploration on the Path to NIF Extended Yield Capability”*

Having reached MJ yields [1], the next major challenge of the indirect-drive ICF implosion effort at NIF is improving performance robustness and increasing yield and gain. To accomplish this we have a multi-pronged near-term approach that includes further increasing laser energy and peak power [2], improving hohlraum efficiency [3], and increasing compression [4] for HDC-based (diamond) ablator implosions.  Some key questions to be addressed include: can lower adiabat and higher compression capsules increase gain and efficiency, can we reach a robust performance regime where yield has plateaued and at what burn-up fraction is this plateau, is ablator-fuel mix limiting the latter, and when can we envisage going beyond hydroscaling to increase fuel mass and yield at lower drive temperature?  Answering these questions will include focussed experiments using existing and improved optical, x-ray and nuclear techniques to better understand and characterize hohlraum and capsule dynamics. Over the longer term, we will be extrapolating and testing key physics scaling such as laser-plasma parametric instability levels of current and new designs for optimum use of a  2.6/600 TW or 3 MJ/450 TW NIF Extended Yield Capability planned for the end of this decade.  This talk will present the current plans and simple scalings that motivate and quantify the potential benefits of success in the various experimental efforts.

[1]  H. Abu-Shawareb et. al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022); A. Kritcher et. al., Phys Rev. E 106, 025201 (2022); A. Zylstra et. al., Phys Rev. E 106, 025202 (2022)

[2] J.M. DiNicola et al., Nucl. Fusion 59, 032004 (2019)

[3]  P. Amendt et al., Phys. Plasmas 26, 082707 (2019)

[4]  D. Clark et. al., Phys .Plasmas 29, 052710 (2022)