One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions

Abstract

Indirect drive inertial confinement fusion experiments with convergence ratios below 17 have been previously shown to be less susceptible to Rayleigh–Taylor hydrodynamic instabilities, making this regime highly interesting for fusion science. Additional limitations imposed on the implosion velocity, in-flight aspect ratio and applied laser power aim to further reduce instability growth, resulting in a new regime where performance can be well represented by one-dimensional (1D) hydrodynamic simulations. A simulation campaign was performed using the 1D radiation-hydrodynamics code HYADES to investigate the performance that could be achieved using direct-drive implosions of liquid layer capsules, over a range of relevant energies. Results include potential gains of 0.19 on LMJ-scale systems and 0.75 on NIF-scale systems, and a reactor-level gain of 54 for an 8.5 MJ implosion. While the use of 1D simulations limits the accuracy of these results, they indicate a sufficiently high level of performance to warrant further investigations and verification of this new low-instability regime. This potentially suggests an attractive new approach to fusion energy. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 2)’.

Central Density and Low-Mode Perturbation Control of Inertial Confinement Fusion Dynamic-Shell Targets

“…This makes the shell susceptible to hydrodynamic instabilities developed during shell acceleration. This is the motivation behind recent work that has attempted to used wetted-foam [14] layers to design ICF targets with low CR [15]. There is however, one more design parameter that controls the shell convergence: initial density of the central (vapor) region.…”

Pathways towards break even for low convergence ratio direct-drive inertial confinement fusion

“…Following these results, a one-dimensional (1-D) simulation campaign was conducted by the authors of this paper (Paddock et al . 2021), which demonstrated that inertial fusion energy (IFE) relevant gains could potentially be achieved using the direct drive approach at low CR. In both that paper and this work gain is used as shorthand for ‘capsule gain’, and is calculated as the produced neutron energy divided by the total input energy (in most cases, the laser energy).…”

“…One aspect of this is the development of new implosions at 100 and 270 kJ of laser input energy, extending the work in Paddock et al . (2021) to lower energies available currently on both Laser Mégajoule (LMJ) and the NIF, and thus more suitable for experiments. In addition, one of the key limitations discussed in Paddock et al .…”

“…In addition, one of the key limitations discussed in Paddock et al . (2021) was that the cryogenic temperatures required by the wetted-foam capsules are not currently compatible with the direct-drive configuration proposed, due to the lack of cryogenic direct-drive platforms at relevant facilities (Hohenberger et al . 2015).…”

Prospects for high gain inertial fusion energy: an introduction to the second edition

“…In the article by Paddock et al ., ‘One-dimensional hydrodynamic simulations of low convergence ratio direct-drive inertial confinement fusion implosions' [20], a computational study of the performance of wetted foam targets that are directly driven is presented. Albeit limited at this stage to one dimension, they indicate that it might be possible to approach energy breakeven on the National Ignition Facility using a novel four-pulse shape design, reinforcing the conclusions of higher adiabat studies of directly driven targets presented earlier by Betti and co-workers [21] who showed 500 kJ of fusion energy for polar direct drive on the National Ignition Facility (corresponding to 74% of the Lawson criterion).…”