Fuel gain exceeding unity in an inertially confined fusion implosion

  • A Corrigendum to this article was published on 18 June 2014

Abstract

Ignition is needed to make fusion energy a viable alternative energy source, but has yet to be achieved1. A key step on the way to ignition is to have the energy generated through fusion reactions in an inertially confined fusion plasma exceed the amount of energy deposited into the deuterium–tritium fusion fuel and hotspot during the implosion process, resulting in a fuel gain greater than unity. Here we report the achievement of fusion fuel gains exceeding unity on the US National Ignition Facility using a ‘high-foot’ implosion method2,3, which is a manipulation of the laser pulse shape in a way that reduces instability in the implosion. These experiments show an order-of-magnitude improvement in yield performance over past deuterium–tritium implosion experiments. We also see a significant contribution to the yield from α-particle self-heating and evidence for the ‘bootstrapping’ required to accelerate the deuterium–tritium fusion burn to eventually ‘run away’ and ignite.

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Figure 1: Indirectly driven, inertially confined fusion target for NIF.
Figure 2: X-ray and neutron images of the hotspot at bang-time.
Figure 3: Yield and energetics metrics for shots on the NIF.

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Acknowledgements

We thank P. Albright, J. Atherton, L. R. Benedetti, D. Bradley, J. A. Caggiano, R. Dylla-Spears, M. J. Edwards, W. H. Goldstein, B. Goodwin, S. Haan, A. Hamza, W. Hsing, P. Kervin, J. Kilkenny, B. Kozioziemski, O. Landen, J. Lindl, B. MacGowan, A. Mackinnon, N. Meezan, J. F. Meeker, J. Moody, E. Moses, D. Pilkington, T. Parham, J. Ralph, S. Ross, H. Robey, R. Rygg, B. Spears, R. Town, C. Verdon, A. Wan and B. Van Wonterghem, and the NIF operations, cryogenics and targets teams. We also thank V. Goncharov and J. Knauer for their advice, and R. Betti for bringing our attention to equation (3). Thanks also go to NIF’s external collaborators at GA (targets), LLE (diagnostics), the MIT Plasma Science and Fusion Center (magnetic recoil spectrometer diagnostic), CEA and AWE. This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under contract no. DE-AC52-07NA27344.

Author information

O.A.H. was lead scientist for the high-foot campaign, and performed two-dimensional stability modelling, and one-dimensional pre- and post-shot analysis. D.A.C. was lead scientist on hotspot shape and hohlraum strategies. D.T.C. was part of the D–T shot experiment team. P.M.C. performed VISAR data unfolds. C.C. performed three-dimensional ‘detailed model’ calculations. E.L.D. was lead experimenter for 1DConA (R(t) trajectory) tuning experiments and capsule re-emission (early-time symmetry) tuning experiments. T.R.D. performed initial one-dimensional capsule design, scoping, and one-dimensional pre- and post-shot simulations. T.D. was lead experimentalist on a 2DConA ablator shape experiment and was part of the D–T shot team. D.E.H. was the pulse shape design physicist and performed all two-dimensional integrated hohlraum-capsule simulations. L.F.B.H. was design physicist for keyhole (shock-timing) tuning experiments. J.L.K. was lead experimentalist for symcap (hotspot shape) tuning experiments. S.L. was lead experimentalist for the keyhole (shock-timing) tuning experiments. T.M. was lead experimentalist for several 2DConA ablator shape experiments, was part of the D–T shot team, and was lead experimentalist on shot N131119. A.G.M. was part of the 1DConA and D–T experimental teams. J.L.M. was design physicist for the re-emission experiment. A.P. was part of the D–T shot team. P.K.P. provided a hotspot model analysis and metrics plots. H.-S.P. was lead experimentalist on D–T implosion shots up to and including N130927. B.A.R. was overall lead on experiments. J.D.S. constructed model multifrequency sources normalized to tuning experiments, and performed one- and two-dimensional model scoping. P.T.S. provided a hotspot model analysis. R.T. provided 1DConA analysis and was shot experimentalist.

Correspondence to O. A. Hurricane.

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Hurricane, O., Callahan, D., Casey, D. et al. Fuel gain exceeding unity in an inertially confined fusion implosion. Nature 506, 343–348 (2014) doi:10.1038/nature13008

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