56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014;
New Orleans, Louisiana
Session AR1: Review: Ignition at NIF: Where We Have Been, and Where We Are Going
8:00 AM–9:00 AM,
Monday, October 27, 2014
Room: Acadia/Bissonet
Chair: David Meyerhofer, University of Rochester
Abstract ID: BAPS.2014.DPP.AR1.1
Abstract: AR1.00001 : Ignition at NIF: Where we have been, and where we are going*
8:00 AM–9:00 AM
Preview Abstract
Author:
Mordecai Rosen
(Lawrence Livermore National Laboratory)
This talk reviews results from the past several years in the pursuit of
indirect-drive ignition on the National Ignition Facility (NIF), and
summarizes ideas and plans for moving forward.
We describe the challenging issues encountered by the low-adiabat (``low
foot''), ``ignition point design'' approach, such as: hydrodynamic
instability growth and ensuing mix of the CH ablator into the DT hot spot;
very high convergence implosions with resultant imperfect symmetry; possible
other issues such as hot electron preheat. The complex interplay among these
issues is a key theme. We describe the progress that has been made in the
understanding and diagnosis of these issues.
We present the results from the high-adiabat (``high foot'') approach, with
its property of relative hydrodynamic stability when compared to the low
foot approach, its somewhat reduced convergence ratio, and its achievement
of entering the alpha heating regime, an important milestone on the road to
ignition.
Paths forward towards ignition include excursions from the present
approaches in pulse shape, hohlraum, and choice of ablator. Further pulse
shaping can lower the adiabat of the high foot approach and lead to higher
performance if it continues to retain its hydrodynamic stability properties.
Conversely, pulse shaping can provide for ``adiabat-shaping'' for the low
foot approach for it to try to attain better stability. A plethora of
hohlraum approaches (size, shape, materials, gas fills) can improve the
zero-order drive, as well as the low-mode shape of the implosion.
Diagnosing, and then correcting, the time dependence of the symmetry is also
a key issue. A variety of ablator materials, along with carefully
engineering the drive spectrum, can increase implosion velocity. The
high-density carbon ablator has shown promising results in this regard. Some
combinations of these developments may allow for an operating space that has
a relatively short pulse, in a near vacuum hohlraum. That combination has
shown, to date, much better coupling efficiency, and a much lower level of
laser plasma instabilities (thus, less electron preheat), than the longer
pulse, full gas-fill, ignition hohlraums.
Advances in modeling, experimental platforms, and diagnostic techniques
developed over the past several years have been key enabling technologies in
moving towards ignition, and we anticipate further advances as well. We
gratefully acknowledge the dedicated efforts of many hundreds of personnel
across the globe who have participated in the laser construction, operation,
target fabrication, and all aspects of the target physics program, that have
taken us this far towards ignition.
*This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.DPP.AR1.1