Demonstration of the improved rocket efficiency in direct-drive implosions using different ablator materials.
The success of direct-drive implosions depends critically on the ability to create high ablation pressures (∼100  Mbar) and accelerating the imploding shell to ignition-relevant velocities (>3.7×10(7 ) cm/s) using direct laser illumination. This Letter reports on an experimental study of the conversion of absorbed laser energy into kinetic energy of the shell (rocket efficiency) where different ablators were used to vary the ratio of the atomic number to the atomic mass. The implosion velocity of Be shells is increased by 20% compared to C and CH shells in direct-drive implosions when a constant initial target mass is maintained. These measurements are consistent with the predicted increase in the rocket efficiency of 28% for Be and 5% for C compared to a CH ablator.
Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14636, USA.
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Michel
Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14636, USA.
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Goncharov
Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14636, USA.
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Igumenshchev
Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14636, USA.
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Epstein
Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14636, USA.
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Froula