Speaker
Peter Andrew Amendt
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O4.207.pdf
Design Studies of Ultra-High Hohlraum-Capsule Coupling Efficiency
Experiments for the NIF*
P.A. Amendt1, M.A. Belyaev1, C.J. Cerjan1, D.D. Ho1, M.W. Sherlock1 and F. Tsung2
1
Lawrence Livermore National Laboratory, Livermore CA 94551
2
University of California, Los Angeles
In indirect-drive inertial confinement fusion a high-Z cylindrical enclosure (or “hohlraum”)
surrounds a low-Z capsule containing DT fuel. Laser beams irradiate the interior of the
hohlraum through a pair of laser entrance holes, creating an x-ray radiation bath that compresses
the fuel to ignition conditions. The coupling of laser light to the capsule is typically ~10%,
resulting in ~200 kJ absorbed energy for the ~2 MJ-scale laser at the National Ignition Facility
(NIF). A new hohlraum design has been found that can accommodate ~50% larger capsules for
up to 3´ more capsule absorbed energy and ~30% coupling efficiency. This new design uses
two truncated, conically-shaped hohlraum halves that join above the capsule equator to provide
a large volume for fitting a larger (1.5 mm radius) capsule and facilitating laser beam
propagation over the entire laser pulse duration. Integrated hohlraum simulations in 2-D show
good control of x-ray drive asymmetry with peak radiation temperatures reaching 295 eV at 1.8
MJ of laser energy. The potential for nearly tripling the capsule absorbed energy translates into
a similar increase in performance margin, thereby improving the prospects for achieving
ignition on the NIF. Backscatter of the laser light at late time when the laser is at peak intensity
and the hohlraum has filled with plasma is a common risk with indirect drive, but a simulation
post-processor (LIP) used to estimate linear instability growth rates predicts benign levels.
Further analysis of the potential for laser-plasma interactions in the nonlinear regime will be
reported using particle-in-cell simulations with the OSIRIS [1] code, the laser beam propagation
code PF3d [2] and the 2D Vlasov Fokker-Planck code K2 for modelling hot electron transport.
[1] R.A. Fonseca, Plasma Phys. Cont. Fus., 50, 124034 (2008).
[2] R.L. Berger et al., Phys. Rev. Lett. 75 (6), 1078 (1995).
* Work performed under the auspices of U.S. Department of Energy by LLNL under Contract DE-AC52-
07NA27344 and supported by LDRD-17-ERD-119
