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Low-Mode Target Lifetime: Experimental Results

Michel Martin, Cyril Gauvin, Géraldine Moll, Olivier Raphaël, Olivier Legaie, Laurent Jeannot

Fusion Science and Technology / Volume 63 / Number 2 / March/April 2013 / Pages 82-86

Technical Paper / Selected papers from 20th Target Fabrication Meeting, May 20-24, 2012, Santa Fe, NM, Guest Editor: Robert C. Cook /

Smooth and uniform solid D-T layers inside a spherical shell are needed to achieve ignition on the Laser Megajoule (LMJ) facility. The thermal environment around the capsule is the key to reach the low-mode D-T layer requirements. During the nineteenth Target Fabrication Meeting in Orlando, Florida (2010), an analytical model was presented to predict the low-mode time evolution of a D-T layer in a capsule caused by a thermal perturbation. The model showed that the dynamical response is ruled by the redistribution time constant. To check the validity of the model, experiments have been done with deuterium layers inside an integrating sphere. The use of an infrared laser to generate a volumetric heating of the deuterium allowed us to tune the conformation time constant. The experimental setup has also been modified to allow or cancel 300-K infrared radiation entering the integrating sphere, producing a local warming on the capsule. Using shadowgraphy techniques, we have been able to follow the dynamical behavior of the deuterium layer. Analyses conclude that the analytical model is right and can be used with confidence.

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