and Layering Characterization of Cryogenic DT Targets for OMEGA
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D. H. Edgell, R. S. Craxton, L. M. Elasky, D. R. Harding, L. S. Iwan, R. L. Keck, L. D. Lund, S. J. Verbridge, A. Weaver, M. D. Wittman, and W. Seka University of Rochester Laboratory for Laser Energetics
48th Annual Meeting of the American Physical Society Division of Plasma Physics Philadelphia, PA 30 October3 November 2006
Summary
Smooth DT-ice layers (<1-nm rms) are repeatedly produced for OMEGA cryogenic targets
DT targets b layer with rms < 1 nm start from single-seed crystal layer slowly over a temperature range of 45 mK reached the point where a significant portion of the bright-ring rms may be caused by perturbations on the outer surface, not the innerice surface DT layers appear to be unchanged by exposure to the OMEGA chamber prior to implosion layer unchanged for t 10 s during exchange-gas vent no melting is observed in images ~30 ms before shots
E15118
Growing an ice layer from a single-seed crystal is essential to forming a smooth layer
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T2257d
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A protocol for forming a single-seed crystal has produced DT ice layers with roughness values between 0.6- and 1.5-nm rms
T2271a
A protocol for forming a single-seed crystal has produced DT ice layers with roughness values between 0.6- and 1.5-nm rms
T2271a
A protocol for forming a single-seed crystal has produced DT ice layers with roughness values between 0.6- and 1.5-nm rms
T2271a
A protocol for forming a single-seed crystal has produced DT ice layers with roughness values between 0.6- and 1.5-nm rms
T2271a
A protocol for forming a single-seed crystal has produced DT ice layers with roughness values between 0.6- and 1.5-nm rms
T2271a
A protocol for forming a single-seed crystal has produced DT ice layers with values roughness between 0.6- and 1.5-nm rms
Reproducibility of layering protocol is encouraging for layering opaque targets.
T2271a
The presence of He in the gas void had little effect on the layer quality
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D:T:3He 1:1:1/8
T2276a
D:T:3He 1:1:1
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Four DT ice layers with an ice roughness <1-nm rms over the entire surface for all modes have been produced
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Shadowgraph analysis and 3-D reconstruction: D. H. Edgell et al., Fusion Sci. Technol. 49, 616 (2006).
E15119
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The outer-shell roughness may dominate the bright-ring rms in these targets
Ice-surface rms may actually be significantly less than apparent. Ray-trace studies are underway to separate outer- and inner-surface effects on the bright ring.
E15120
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The quality of the ice layer at shot time is determined by the time the target is without sufficient He exchange gas
Before removing the shrouds to expose the target, the He exchange gas is vented from around the target. ~ few seconds to clear He from target chamber This allows the ice to warm at a rate of 1 K/15 s and slump at a rate of...