High Power Laser Science and Engineering, (2016), Vol. 4, e44, 7 pages.
© The Author(s) 2016. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/
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doi:10.1017/hpl.2016.43
Developing one-dimensional implosions for inertial
confinement fusion science
J. L. Kline
1
, S. A. Yi
1
, A. N. Simakov
1
, R. E. Olson
1
, D. C. Wilson
1
, G. A. Kyrala
1
, T. S. Perry
1
,
S. H. Batha
1
, E. L. Dewald
2
, J. E. Ralph
2
, D. J. Strozzi
2
, A. G. MacPhee
2
, D. A. Callahan
2
, D. Hinkel
2
,
O. A. Hurricane
2
, R. J. Leeper
1
, A. B. Zylstra
1
, R. R. Peterson
1
, B. M. Haines
1
, L. Yin
1
, P. A. Bradley
1
,
R. C. Shah
1
, T. Braun
2
, J. Biener
2
, B. J. Kozioziemski
2
, J. D. Sater
2
, M. M. Biener
2
, A. V. Hamza
2
,
A. Nikroo
2
, L. F. Berzak Hopkins
2
, D. Ho
2
, S. LePape
2
, N. B. Meezan
2
, D. S. Montgomery
1
,
W. S. Daughton
1
, E. C. Merritt
1
, T. Cardenas
1
, and E. S. Dodd
1
1
Los Alamos National Laboratory, Los Alamos, NM, USA
2
Lawrence Livermore National Laboratory, Livermore, CA, USA
(Received 3 May 2016; revised 29 September 2016; accepted 25 October 2016)
Abstract
Experiments on the National Ignition Facility show that multi-dimensional effects currently dominate the implosion
performance. Low mode implosion symmetry and hydrodynamic instabilities seeded by capsule mounting features
appear to be two key limiting factors for implosion performance. One reason these factors have a large impact on the
performance of inertial confinement fusion implosions is the high convergence required to achieve high fusion gains.
To tackle these problems, a predictable implosion platform is needed meaning experiments must trade-off high gain for
performance. LANL has adopted three main approaches to develop a one-dimensional (1D) implosion platform where
1D means measured yield over the 1D clean calculation. A high adiabat, low convergence platform is being developed
using beryllium capsules enabling larger case-to-capsule ratios to improve symmetry. The second approach is liquid fuel
layers using wetted foam targets. With liquid fuel layers, the implosion convergence can be controlled via the initial vapor
pressure set by the target fielding temperature. The last method is double shell targets. For double shells, the smaller inner
shell houses the DT fuel and the convergence of this cavity is relatively small compared to hot spot ignition. However,
double shell targets have a different set of trade-off versus advantages. Details for each of these approaches are described.
Keywords: beryllium capsules; double shells; inertial confinement fusion; liquid layers
1. Introduction
While progress towards laser-based indirect drive inertial
confinement fusion (ICF) is being made
[1–3]
, experimental
results show challenges remain. Recent modeling of implo-
sion experiments for both low and high adiabat implosions
has identified specific issues that are believed to impact
the performance for each type of implosion
[4]
. For the
high convergence, low adiabat implosions, the dominant
mechanisms believed to degrade performance are hydrody-
namic instabilities seeded by capsule mounting hardware
such as the fill tube, tenting
[5, 6]
used to hold the capsule in
place and capsule surface roughness, as well as low mode
asymmetries. High adiabat implosions, designed to reduce
Correspondence to: J. L. Kline, MS E526, PO Box 1663, Los Alamos,
NM 87545, USA. Email: jkline@lanl.gov
the effect of ablation front hydrodynamic instabilities, as
well as a reduced convergence, are impacted primarily by
low mode implosion shape. In both cases, shape and hy-
drodynamic instability play a key role. While there may be
other degradation mechanisms, they are difficult to assess
without addressing the afore-mentioned issues. Thus, the
near term goal for ICF experiments on the NIF is to mitigate
these known effects by pushing towards round implosions
while addressing high mode perturbations to maximize one-
dimensional (1D) implosion behavior, i.e., high yield over
1D clean (no mix) simulations. The most straight forward
means to do this is to retreat from aggressive ICF designs
by reducing the implosion convergence, defined as the ini-
tial outer radius to the final hot spot x-ray self-emission
radius, and increasing the case-to-capsule ratio, defined as
the hohlraum to capsule outer radius. This should provide
a more predictable platform that can be used to study
1