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Deuterium-Tritium Beta-Layering Within a National Ignition Facility Scale Polymer Target in the LANL Cryogenic Pressure Loader

Peter S. Ebey, James M. Dole, Drew A. Geller, James K. Hoffer, Arthur Nobile, John D. Sheliak

Fusion Science and Technology / Volume 48 / Number 3 / November 2005 / Pages 1292-1298

Technical Paper /

Beta-layering, the process of beta-decay heat-driven mass redistribution, has been demonstrated in a deuterium-tritium (D-T)-filled polymer sphere of the type required for fusion ignition experiments at the National Ignition Facility. This is the first report, to the best of the authors' knowledge, of a D-T layer formed in a permeation-filled sphere. The 2-mm-diam sphere was filled with D-T by permeation; cooled to cryogenic temperatures while in the high-pressure permeation vessel; and, while cold, removed to an optical axis where the D-T was frozen, melted, and beta-layered in a series of experiments over several weeks' time. This work was performed in the Los Alamos National Laboratory cryogenic pressure loader system. The beta-layering time constant was 24.0 ± 2.5 min, less than the theoretical value of 26.8 min, and not showing the significant increase due to build-up of 3He often observed in beta-layered samples. Supercooling of the liquid D-T was observed. Neither the polymer target nor its tenting material showed visual signs of degradation after 5 weeks of exposure to D-T. Small external thermal gradients were used to shift the D-T material back and forth within the sphere.

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