Lawrence Livermore National Laboratory's activities 
to achieve ignition by X-ray drive on the National Ignition 
Facility

Kilkenny, J. D.; Bernat, T. P.; Hammel, B. A.; Kauffman, R. L.; Landen, O. L.; Lindl, J. D.; MacGowan, B. J.; Paisner, J. A.; Powell, H. T.

doi:10.1017/s0263034699172021

Cited by 12 publications

(5 citation statements)

References 5 publications

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“…1 NIF is designed to drive inertial confinement fusion ͑ICF͒ capsules to ignition using indirect drive, in which the laser energy is converted to thermal x rays inside a cavity ͑hohlraum͒. The x rays then ablate the outer layers of a capsule inside the hohlraum, causing the capsule to implode and achieve ignition.…”

Section: National Ignition Facility Scale Hohlraum Asymmetry Studies mentioning

confidence: 99%

National Ignition Facility scale hohlraum asymmetry studies by thin shell radiography

et al. 2001

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A necessary condition for igniting indirectly driven inertial confinement fusion (ICF) capsules on the National Ignition Facility (NIF) is controlling drive asymmetry to the 1% level [S. W. Haan, S. M. Pollaine, J. D. Lindl et al., Phys. Plasmas 2, 2480 (1995)]. Even flux-asymmetry modes (e.g., Legendre modes P2, P4, P6, and P8) must be reduced by hohlraum design and laser beam pointing. Odd flux-asymmetry modes (e.g., Legendre modes P1, P3, P5, etc.) are theoretically removed by reflection symmetry across the hohlraum midplane [S. M. Pollaine and D. Eimerl, Nucl. Fusion 38, 1523 (1998)], but will be produced by power imbalance, laser beam pointing errors, and target fabrication errors. An experimental campaign is now being conducted on the University of Rochester’s Omega laser to measure higher order (P4 and higher) flux asymmetry modes inside hohlraums that approximate the conditions of a NIF hohlraum during the 90 eV early drive phase [S. W. Haan, S. M. Pollaine, J. D. Lindl et al., Phys. Plasmas 2, 2480 (1995)]. These experiments use a new point-projection backlighting technique [O. L. Landen, D. R. Farley, S. G. Glendinning et al., Rev. Sci. Instrum. 72, 627 (2001)] to cast high quality 4.7 keV radiographs of thin 2 mm diameter Ge-doped CH shells designed to enhance sensitivity to drive asymmetries. Distortions in the position of the limb of the shells resulting primarily from drive asymmetries are measured to an accuracy of 2 μm. The linearity and sensitivity of thin imploding shells to flux asymmetry makes it possible to achieve this degree of accuracy, which is sufficient for NIF ignition symmetry tuning. The promising results to date permit the comparison of measured and predicted distortions and, by inference, drive asymmetries for the first eight asymmetry modes.

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Section: National Ignition Facility Scale Hohlraum Asymmetry Studies mentioning

confidence: 99%

National Ignition Facility scale hohlraum asymmetry studies by thin shell radiography

et al. 2001

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“…Thermonuclear ignition via indirect-drive inertial confinement fusion (ICF) is one of the primary goals of the National Ignition Facility (NIF) [1] in the U.S. and of the Laser Megajoule (LMJ) [2] in France. In the indirectdrive ICF option, the high power input (500 TW) of 0:35 m laser beams will be absorbed in a high-Z enclosure (or ''hohlraum'') that surrounds a low-Z spherical shell (or ''capsule'') containing a layer of solid cryogenic deuterium-tritium (DT) fuel.…”

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confidence: 99%

Preheat Effects on Shock Propagation in Indirect-Drive Inertial Confinement Fusion Ablator Materials

et al. 2003

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The velocities and temperatures of shock waves generated by laser-driven hohlraum radiation fields have been measured for several indirect-drive inertial confinement fusion capsule ablator materials. For the first time, a time-resolved measurement of the preheat temperature ahead of the shock front has been performed and included in the analysis. It is found that preheat ahead of the shock front can cause significant shock propagation variations in the ignition capsule ablator materials being considered for the National Ignition Facility (NIF). If unaccounted for, these preheat effects could potentially preclude ignition at the NIF.

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“…As such, they are only an early step along the path of the indirect-drive ICF ignition program plan outlined in Ref. 1. Within the next few years, some of the measurement and calculational techniques developed in these Omega experiments will be employed in more advanced studies using the longer pulses, higher energies, and larger hohlraums that will soon be available at the NIF.…”

Section: Discussionmentioning

confidence: 99%

Shock propagation, preheat, and x-ray burnthrough in indirect-drive inertial confinement fusion ablator materials

et al. 2004

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The velocities and temperatures of shock waves generated by laser-driven hohlraum radiation fields have been measured in indirect-drive inertial confinement fusion (ICF) capsule ablator materials. Time-resolved measurements of the preheat temperature ahead of the shock front have been performed and included in the analysis. Measurements of the x-ray burnthrough of the ablation front and the ablator x-ray re-emission have also been made in the Cu-doped beryllium, polyimide, and Ge-doped CH ablator samples. The experiments utilize 15 beams of the University of Rochester Omega Laser [Soures et al., Phys. Plasmas 3, 2108 (1996)] to heat hohlraums to radiation temperatures of ∼120–200 eV. In the experiments, planar samples of ablator material are exposed to the hohlraum radiation field, generating shocks in the range of 10–50 Mbars. The experimental results are compared to integrated two-dimensional Lasnex [G. B. Zimmerman and W. L. Kruer, Comments Plasma Phys. Control. Fusion 2, 51 (1975)] calculations, in which the measured laser pulse is used as input and the time-dependent ultraviolet shock breakout and soft x-ray ablator burnthrough are calculated quantities. It is found that proper calculation of the time-dependent hohlraum x-ray flux, including spectral content, and the ablator opacity will be essential for obtaining the level of predictive capabilities required for the thermonuclear ignition of an ICF capsule at the U.S. National Ignition Facility [E. I. Moses, Fusion Technol. 44, 11 (2003)].

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Lawrence Livermore National Laboratory's activities to achieve ignition by X-ray drive on the National Ignition Facility

Cited by 12 publications

References 5 publications

National Ignition Facility scale hohlraum asymmetry studies by thin shell radiography

National Ignition Facility scale hohlraum asymmetry studies by thin shell radiography

Preheat Effects on Shock Propagation in Indirect-Drive Inertial Confinement Fusion Ablator Materials

Shock propagation, preheat, and x-ray burnthrough in indirect-drive inertial confinement fusion ablator materials

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