Using laser entrance hole shields to increase coupling efficiency in indirect drive ignition targets for the National Ignition Facility

2006 ◽  
Vol 13 (5) ◽  
pp. 056307 ◽  
Author(s):  
D. A. Callahan ◽  
P. A. Amendt ◽  
E. L. Dewald ◽  
S. W. Haan ◽  
D. E. Hinkel ◽  
...  
Keyword(s):  
Coupling Efficiency ◽  
National Ignition Facility ◽  
Indirect Drive ◽  
Entrance Hole

Three dimensional low-mode areal-density non-uniformities in indirect-drive implosions at the National Ignition Facility

2021 ◽  
Vol 28 (4) ◽  
pp. 042708
Author(s):  
D. T. Casey ◽  
O. L. Landen ◽  
E. Hartouni ◽  
R. M. Bionta ◽  
K. D. Hahn ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Areal Density ◽  
National Ignition Facility ◽  
Indirect Drive

scholarly journals Capsule design for the National Ignition Facility

1999 ◽  
Vol 17 (2) ◽  
pp. 217-224 ◽  
Author(s):  
T.R. DITTRICH ◽  
S.W. HAAN ◽  
M.M. MARINAK ◽  
D.E. HINKEL ◽  
S.M. POLLAINE ◽  
...  
Keyword(s):  
Dopant Concentration ◽  
Three Dimensions ◽  
Initial Surface ◽  
National Ignition Facility ◽  
X Ray ◽  
Ongoing Effort ◽  
Surface Finishes ◽  
Material Homogeneity ◽  
Indirect Drive ◽  
Reduced Scale

Several choices exist in the design and production of capsules intended to ignite and propagate fusion burn of the deuterium–tritium (D–T) fuel when imploded by indirect drive at the National Ignition Facility (NIF). These choices include ablator material, ablator dopant concentration and distribution, capsule dimensions, and X-ray drive profile (shock timings and strengths). The choice of ablator material must also include fabrication and material characteristics, such as attainable surface finishes, permeability, strength, transparency to radio frequency and infrared radiation, thermal conductivity, and material homogeneity. Understanding the advantages and/or limitations of these choices is an ongoing effort for LLNL and LANL designers. At this time, simulations in one-, two-, and three-dimensions show that capsules with either a copper-doped beryllium or a polyimide (C22H10N2O4) ablator material have both the least sensitivity to initial surface roughnesses and favorable fabrication qualities. Simulations also indicate the existence of capsule designs based on these ablator materials which ignite and burn when imploded by less than nominal laser performance (900-kJ energy, 250-TW power, producing 250-eV peak radiation temperature). We will describe and compare these reduced-scale capsules, in addition to several designs which use the expected 300-eV peak X-ray drive obtained from operating the NIF laser at 1.3 MJ and 500 TW.

scholarly journals Progress in direct-drive fusion studies for the Laser Mégajoule

2004 ◽  
Vol 22 (2) ◽  
pp. 109-114 ◽  
Author(s):  
B. CANAUD ◽  
X. FORTIN ◽  
F. GARAUDE ◽  
C. MEYER ◽  
F. PHILIPPE
Keyword(s):  
Recent Progress ◽  
Coupling Efficiency ◽  
Direct Drive ◽  
Time Analysis ◽  
Laser Target ◽  
Long Wavelength ◽  
Laser Driver ◽  
Indirect Drive ◽  
Ice Shell ◽  
Target Design

In the context of the French Laser Mégajoule (LMJ) fusion research program, direct drive is an alternate to indirect drive to reach ignition and thermonuclear burn. We present recent progress in the direct-drive fusion studies for LMJ. Calculations have shown that the LMJ irradiation uniformity is characterized by long wavelength asymmetries compatible with direct drive requirements. Calculations of the irradiation uniformity in the context of indirect drive beam positioning have been done. We show that non-uniformity can be minimized by repointing the beams. Unfortunately, a time analysis shows that this nonuniformity increases strongly in time above levels usually considered inconsistent for direct drive. Finally, a recent baseline target design is presented and consists of a DT ice shell surrounded by a low-density CH foam wicked with cryogenic DT. This design can potentially reach a gain of 90 with a 1-MJ on-target laser driver. Hydrodynamic stability is increased at the ablation front and the laser–target coupling efficiency achieves 85%.

scholarly journals Study on size of laser entrance hole shield for ignition octahedral spherical hohlraums

2015 ◽  
Vol 33 (4) ◽  
pp. 731-739 ◽  
Author(s):  
Shu Li ◽  
Ke Lan ◽  
Jie Liu
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Analytical Model ◽  
Critical Radius ◽  
Coupling Efficiency ◽  
Three Dimensional ◽  
Main Pulse ◽  
Laser Spot ◽  
Entrance Hole ◽  
Target Design

AbstractIn this paper, the influences of laser entrance hole shields on capsule symmetry and coupling efficiency of an ignition octahedral spherical hohlraum are studied using analytical model and three-dimensional Monte-Carlo simulations. As a result, there are two critical shield radii at which the capsule asymmetry tends to minimum, and the coupling efficiency from hohlraum to capsule reaches its maximum when the shield size is taken around the second critical radius. For the ignition octahedral hohlraums used in our study, the first critical radius is 0.625 mm with a capsule asymmetry of 0.24%, and the second is 0.86 mm with 0.26%, and the asymmetry is smaller than 0.58% for shields’ radius in the range of 0.44 and 0.88 mm, which therefore leaves much flexibility in the shield radius design even the shields have an expansion under radiation ablation. The initial shield radius can be taken around the first critical radius in the ignition target design, not only to have a minimum initial capsule radiation asymmetry, but also to get a minimum asymmetry and highest coupling efficiency during the main pulse of drive. Finally, the relative flux of laser spot, wall and shields is 2.2:1:0.6 for our ignition octahedral spherical hohlraum model from the Monte-Carlo simulations.

scholarly journals High-Performance Indirect-Drive Cryogenic Implosions at High Adiabat on the National Ignition Facility

2018 ◽  
Vol 121 (13) ◽  
Author(s):  
K. L. Baker ◽  
C. A. Thomas ◽  
D. T. Casey ◽  
S. Khan ◽  
B. K. Spears ◽  
...  
Keyword(s):  
High Performance ◽  
National Ignition Facility ◽  
Indirect Drive

scholarly journals Direct drive double shell target implosion hydrodynamics on OMEGA

2005 ◽  
Vol 23 (2) ◽  
pp. 187-192 ◽  
Author(s):  
GEORGE A. KYRALA ◽  
NORMAN DELAMATER ◽  
DOUGLAS WILSON ◽  
JOYCE GUZIK ◽  
DON HAYNES ◽  
...  
Keyword(s):  
Time History ◽  
Direct Drive ◽  
National Ignition Facility ◽  
Initial Stage ◽  
Heat Effects ◽  
Measured Time ◽  
History Of ◽  
Indirect Drive ◽  
Omega Laser ◽  
And Performance

Imploding indirect-drive double shell targets may provide an alternative, non-cryogenic path to ignition at the National Ignition Facility (NIF). Experiments are being pursued at OMEGA to understand the hydrodynamics of these implosions and the possibility of scaling it to the NIF design. We have used 40 beams from the OMEGA laser to directly drive the capsules, and we have used the remaining 20 beams to backlight the imploding shells from two different directions at multiple times. We will review the recent experiments to measure the hydrodynamics of the targets using two-view X-ray radiography of the capsules. We will present data on measured yields from the targets. We will present a measured time history of the hydrodynamics of the implosion. Experiments were pursued using direct drive in which the M-band effect (experienced in the indirect drive experiments) could be eliminated or controlled. It was learned in the direct drive experiments that the best performing capsules were those that had a thin outer layer of gold. This effectively causes M-band pre-heat effects giving implosion hydrodynamics and performance closer to the indirect drive case. We will review the methods used to radiograph the targets and the techniques used to extract useful information to compare with calculations. The effect of imperfections in the target construction will be shown to be minimal during the initial stage of implosion. The yields from the targets were observed to be uniformly low compared to indirect-drive.

scholarly journals Self-Generated Magnetic Fields in the Stagnation Phase of Indirect-Drive Implosions on the National Ignition Facility

2017 ◽  
Vol 118 (15) ◽  
Author(s):  
C. A. Walsh ◽  
J. P. Chittenden ◽  
K. McGlinchey ◽  
N. P. L. Niasse ◽  
B. D. Appelbe
Keyword(s):  
Magnetic Fields ◽  
National Ignition Facility ◽  
Indirect Drive

scholarly journals Three-Dimensional Design Simulations of a High-Energy Density Reshock Experiment at the National Ignition Facility

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Ping Wang ◽  
Kumar S. Raman ◽  
Stephan A. MacLaren ◽  
Channing M. Huntington ◽  
Sabrina R. Nagel ◽  
...  
Keyword(s):  
Energy Density ◽  
Hydrodynamic Instability ◽  
Three Dimensional ◽  
High Energy ◽  
High Energy Density ◽  
Fluid Interface ◽  
National Ignition Facility ◽  
X Ray Imaging ◽  
Indirect Drive ◽  
Instability Growth

We present simulations of a new experimental platform at the National Ignition Facility (NIF) for studying the hydrodynamic instability growth of a high-energy density (HED) fluid interface that undergoes multiple shocks, i.e., is “reshocked.” In these experiments, indirect-drive laser cavities drive strong shocks through an initially solid, planar interface between a high-density plastic and low-density foam, in either one or both directions. The first shock turns the system into an unstable fluid interface with the premachined initial condition that then grows via the Richtmyer–Meshkov and Rayleigh–Taylor instabilities. Backlit X-ray imaging is used to visualize the instability growth at different times. Our main result is that this new HED reshock platform is established and that the initial data confirm the experiment operates in a hydrodynamic regime similar to what simulations predict. The simulations also reveal new types of edge effects that can disturb the experiment at late times and suggest ways to mitigate them.

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