Enhanced energy coupling for indirectly driven inertial confinement fusion

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Abstract

Recent experiments in the study of inertial confinement fusion (ICF) at the National Ignition Facility (NIF) in the United States have reached the so-called alpha-heating regime1,2,3, in which the self-heating by fusion products becomes dominant, with neutron yields now exceeding 1 × 1016 (ref. 4) However, there are still challenges on the path towards ignition, such as minimization of the drive asymmetry, suppression of laser-plasma instabilities, and mitigation of fabrication features5. In addition, in the current cylindrical-hohlraum indirect drive schemes for ICF, a strong limitation is the inefficient (≤10%) absorption of the laser-produced hohlraum X-rays by the capsule as set by relative capsule-to-hohlraum surface areas. Here we report an experiment demonstrating ~30% energy coupling to an aluminium capsule in a rugby-shaped6, gold hohlraum. This high coupling efficiency can substantially increase the tolerance to residual imperfections and improve the prospects for ignition, both in mainline single-shell hot-spot designs and potential double-shell targets.

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Fig. 1: Experimental set-up and measured time history of laser power and radiation temperature.
Fig. 2: Results from 1D X-ray radiography.
Fig. 3
Fig. 4: Results from 2D X-ray radiography.
Fig. 5: Energy coupled to the capsule as a function of time from 0.7× subscale and full-scale simulations.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We thank the NIF team at LLNL for excellent laser operation and technical support. We also would like to thank the target fabrication group for outstanding work on development and delivery of the high-quality Al capsules. This work was performed under the auspices of the US DOE by LLNL under contract number DEAC52-07NA27344. Y.P. acknowledges support from the DOE/ECRP Program. Y.M.W. acknowledges LLNL LDRD (17-ERD-048) support.

Author information

Y.P. and V.A.S. carried out the experimental set-up and execution with help from R.T., E.D., A.G.M. and J.E.R.. P.A. was the target designer and performed the pre- and post-shot simulations. R.T., J.F., S.K., Y.P., V.A.S. and O.L.L. contributed to the data analysis. D.B., S.J., A.N., R.S. and Y.M.W. contributed to fabrication of the high-quality Al capsules, D.S. contributed to backscatter mitigation, F.G., J.P., S.P. and R.E.T. contributed to the planning and simulations. E.L., E.M. and D.M. contributed to the backlighter and radiography development. Y.P. wrote the manuscript and P.A. wrote the simulation and full design sections. Y.P., V.A.S., P.A., R.T., O.L.L., A.G.M. and Y.M.W. contributed to the manuscript improvements.

Correspondence to Y. Ping.

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Ping, Y., Smalyuk, V.A., Amendt, P. et al. Enhanced energy coupling for indirectly driven inertial confinement fusion. Nature Phys 15, 138–141 (2019) doi:10.1038/s41567-018-0331-5

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