A pushered capsule implosion as an alternate approach to the ignition regime for inertial confinement fusion

In inertial confinement fusion, the threshold for ignition is a highly dynamic quantity as the sources and sinks of power in the hot spot can vary rapidly. In this article, we consider the ignition condition as a race between heating and disassembly rates and make use of a prior solution to the fusion hot-spot thermodynamics to develop a Lawson-like ignition criteria for pressure x confinement time (p-tau) vs temperature. Low-Z capsule designs reach the temperature for this threshold using as much of the shell as feasible as ablator but then are limited in tau by low stagnated mass. An alternate approach, the pushered single shell (PSS) design [D. D.-M. Ho, S. MacLaren, and Y. Wang, High-yield implosions via radiation trapping and high rho-R, paper presented at the 60th Annual Meeting of the APS Division of Plasma Physics, 2018], introduces a dense inner layer of Mo-Be alloy that is smoothly graded outward to pure Be, increasing the confinement time at stagnation and lowering the temperature requirement at the ignition threshold. Here, we describe a PSS ignition design for the National Ignition Facility and use the theory as well as simulations to compare it with the low-Z capsule approach. Additionally, we show how an adjustment to the design is used to anticipate the effects of mixing at the fuel-ablator interface.

Automated summary

In this article, the competition between heating and disassembly rates in inertial confinement fusion is considered, and a Lawson-like ignition criterion for pressure x confinement time (p-tau) vs temperature is developed based on prior solutions to fusion hot-spot thermodynamics. A new pushered single shell (PSS) ignition design is described, utilizing a dense inner layer of Mo-Be alloy to increase confinement time at stagnation and lower the temperature requirement at ignition threshold. The design adjustment to anticipate mixing effects at the fuel-ablator interface is also discussed.