54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012;
Providence, Rhode Island
Session NI2: ICF Implosions
9:30 AM–12:30 PM,
Wednesday, October 31, 2012
Room: Ballroom DE
Chair: Mordecai Rosen, Lawrence Livermore National Laboratory
Abstract ID: BAPS.2012.DPP.NI2.2
Abstract: NI2.00002 : Improving Cryogenic-DT Implosion Performance on OMEGA
10:00 AM–10:30 AM
Preview Abstract
Abstract
Author:
T.C. Sangster
(Laboratory for Laser Energetics, U. of Rochester)
Although cryogenic-DT implosion performance has improved both in absolute
terms and relative to hydro simulations, a number of long-standing
discrepancies remain unresolved. Absolute yield performance increased with
higher-quality capsule and ice surfaces, routine delivery of low-adiabat
($\alpha$ $\sim $ 2) laser pulses at specification, and more-accurate target
alignment with respect to the beam pointing (typically less than 10-$\mu$m rms
for all 60 beams). Higher implosion velocities using thinner ice and
constant mass ablators have resulted in additional increases in measured
yields and ion temperatures. However, ion temperatures remain systematically
below the hydro predictions suggesting higher-than-predicted imprint levels
(note that $T_{i} \sim T_{e}$ for all implosions except for cases where
fuel motion artificially enhances $T_{i})$. Imprint reduction is being
addressed using dopants (small at.{\%} of silicon) in the outer part of the
ablator. To preserve the ablator mass, doped shells are necessarily thinner
than undoped shells and recent compression results show a clear inverse
relation between the inferred areal density and the measured yields. This
suggests more radiative preheat with the thinner ablators (the areal
densities are about 70{\%} of predictions---below what is expected based on
burn truncation). While improved nonlocal thermal transport and cross-beam
energy transfer models resolved a persistent discrepancy between predicted
and measured bang times, the measured burn width is longer than predicted.
Furthermore, core x-ray emission below 2.5 keV is consistently higher than
predictions. These discrepancies, combined with improved modeling, implicate
shell stability and suggest that thicker ablators and thinner ice (to
preserve the overall payload mass) may lead to improved ignition hydro
equivalency. This talk will show the latest experimental results using
thicker ablators and ablators doped with silicon, and compare these results
with the latest hydro simulations.\\[4pt]
This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative
Agreement No. DE-FC52-08NA28302. In collaboration with V. N. Goncharov, R.
Betti, T. R. Boehly, R. Epstein, C. Forrest, V. Yu. Glebov, S. X. Hu, I. V.
Igumenshchev, D. H. Froula, R. L. McCrory, D. D. Meyerhofer, P. B. Radha, W.
Seka, W. T. Shmayda, S. Skupsky, C. Stoeckl (Laboratory for Laser
Energetics, U. of Rochester), J. A. Frenje, D. T. Casey, and M. Gatu-Johnson
(Plasma Science and Fusion Center, MIT).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.DPP.NI2.2