LLNL-PRES-725630

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC

Alternate Capsule Support for Inertial Confinement Fusion TargetsTarget Fabrication Meeting 2017

Las Vegas

Michael Stadermann

March 15th, 2017

LLNL-PRES-xxxxxx

2

Team

Target Fab:Ethan Alger

Chantel Aracne-Ruddle

Suhas Bhandarkar

John Bigelow

Tom Bunn

Chris Choate

Sean Felker

Joe Florio

Chuck Heinbockel

Steve Johnson

Jeremy Kroll

Xavier Lepro

Abbas Nikroo

Physics:

Louisa Pickworth

Harry Robey

Vladimir Smalyuk

Chris Weber

General Atomics:

Jay Crippen

Martin Havre

Javier Jaquez

Neal Rice

Capsule support presentations:Aracne-Ruddle, Tu Poster

Bigelow, Tu Poster

Weber, Wed 10:40

Felker, Wed 11:00

Crippen, Wed 11:20

Alfonso, Wed 11:40

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Tents can cause perturbations that affect the implosion

300 mm

Pressure

exploding tent pressure wave

capsuleablation

As the tent explodes and capsule ablates, they create misaligned pressure and density gradients, which produce a local vorticity perturbation

Weber, Wed 10:40

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There are three principal categories of capsule support

Ranking and down selecting based on feasibility and physic value (both near and long term) is key to making progress and assessing resource needs

No capsule or fill tube contact

wires parallel

to page

wires page^

Fill tube contact but No capsule contact

wire page^

Fill tube only Supported capsuleSupported fill tube

• 10 µm tube desired

• Vibration and sag are

issues

• Many support variations

• Potentially can use 10 µm

tube

• Extra mass in hohlraum

• Vibration and sag needs study

• Assembly development

• Many support variations

• Potentially can use 10 µm tube

• Capsule contact needs to be

minimal

• Foam

• Stalk

• Membrane

• Sleeve

• Wire cage

• Foam

• Tent (modified angle)

• Stalks

• Different tube

material

Capsule and fill tube contact

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There has been no shortage of ideas on possible alternate solutions

Larger diameter fill-tubeReduced tent angle

requires 4-part

hohlraum

Polar contact with disk

thin HDC

disk

to ensure

tangential

contact

Minimal wire support

wires parallel

to page

wires page^

Gravity support

standard

fill-tubetent or

wire to

support

FT near

capsulelower support

for symmetry

Annular tent support

thicker tent

with hole in

center

supports FT,

does not touch

capsule

Gravity support + LEH

shields

LEH shield

Cantilevered fill-tube

wire page^

HDC tube

extension

for support

HDC tube support

Fill tube only Supported capsule TentsSupported/clamped fill tube

low-density

(3 mg/cc)

foam

Block foam support

Only a partial list of solutions is shown.

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Each concept undergoes a series of evaluations

Aracne-Ruddle, Tu Poster

Felker, Wed 11:00

Felker, Wed 11:00

Weber, Crippen, Alfonso Wed 10:40-12:00

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Simulation gives us a prediction of performance

Replacing the tent is predicted to improve yield by up to 5x.

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Supporting the capsule by only the fill-tube provides the smallest perturbation, but presents some serious issues

Note that these movies are for a 30 µm diameter fill-tube vs. the standard 10 µm

30 µm FT @ 40 Hz

30 µm FT @ 65 Hz

0

0.002

0.004

0.006

0.008

0.01

0.012

0 50 100 150 200

grm

s

Freq (Hz)

Z direction on

off

Accelerometer measurement on TARPOS

from GA

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The first alternative support method built into a target was a free-standing 30 µm fill tube

Regular 10 µm fill tube Free standing 30 µm fill tube

The 30 µm fill tube required substantially more glue at the capsule joint, as well as a fill tube refit.

No large performance increase was expected, but the implosion shape should be affected.

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“Polar contact” design uses stiff polyimide films with carbon that have a very small contact to the capsule

Final assembly of ‘crowned’ halfraums

Several 4-part hohlraum targets have been shot on NIF.

Simulation predicts a smaller perturbation over a smaller angle.

Aracne-Ruddle, Tu Poster

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Support fill tube design use a thicker fill tube or stalk to hold the 10 µm fill tube at a distance from the capsule

Supported fill tube subassembly

Capsule-stalk distance: 200 µm

complete

support rod

fill-tube

Capsule-stalk distance: 200 µm

3-part fill tube subassembly

Layerable test articles are being built.

Bigelow, Tu Poster

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The Tetracage design uses four fibers to support the capsule

5 µm Toray fibers (carbon)

Finding an appropriate fiber material has been the primary development challenge.

Aracne-Ruddle, Tu Poster

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Magnetic levitation is being evaluated in a longer-term project

Steig, McCall, Baker, Bayu-Aji, Bae, Kucheyev

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The first two support options showed the expected shift in x-ray shape

+P4 x-ray shape from tent was removed with alternate mounts

x-ray

image

from tent-

only sim.

Polar

Tent

30m

m

FT

+P4 is assumed to be caused by tents.

P4

/P0

More sensitive implosions and other supports remain to be tested.

30m

m FT

ne

utr

on y

ield

Neutron yield was similar to related experiments

Polar

Tent

15LLNL-PRES-######

Conclusion

We have investigated alternative capsule support strategies to mitigate perturbations caused by the tent.

Three designs have emerged as most promising: 4-part hohlraum, supported fill tube, tetracage. Two designs have been fielded on NIF

Alternate support targets shot show the expected x-ray shape change.

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As BT moves later and yield drops, gain from polar tent is reduced. Only 20-30% improvement

1.75x

improvement

*

N160829N160509

30mm FTPolar

Tent

N140520

w/ polar

tent

N160829

polar

tent sim

1.5x

w/

standard

tent

1.35x

1.2x

Good performance from this high foot platform is needed to observe improvements from tent

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Other platforms are more sensitive to the tent – we would expect a larger improvement

Yield-over-clean (no a-dep.) from a standard tent

0.50.60.70.80.9

1

LowFoot

ASLF ASHF(T-1)

HighFoot

(T-1.5)

HighFoot(T-1)

HighFoot(T0)

• Largest effect at the high convergence

(Low Foot and Adiabat Shaped Low Foot)

• Limited reproducibility

• Reduced tent impact at High Foot

• Established reproducibility for T-1, but

questioned by recent experiments

High foot

a ~ 2.5

Low foot

a ~ 1.5

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0.70

0.75

0.80

0.85

0.90

0.95

1.00

standardtent

40umFT

polartent

foamtent

support100um

support200um

support300um

The supported fill-tube may be the best tent replacement option

YOC=0.17

w/ a-dep.

Yield/clean (no a-dep.) for 175mm thick (T-1)

high foot implosions (N140520)

Minimal degradation with ≥200

mm stand-off distance

Degradations

from foam

modulations?

*Note: other

calculations

do not

include a FT

Need to validate

imprint with HGR

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An alternative capsule mount is being studied to improve the performance of ICF implosions on NIF

New mounting options exist that show promise in removing the tent perturbation

Many unexpected observations from experiments – transforming our understanding of how perturbation develop from engineering features

Simulation capability has been developed to evaluate these effects and understand their on performance

More experiments are needed to expand our understand of these effects and evaluate these support options

in-flight radiograph

showing tent scar

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2-part fill-tube

10 mm diameter

30 mm diameter

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Each concept undergoes a series of evaluations

Materials test

Assembly test

Dynamic test

• Measure material properties

• Determine basic feasibility

• Assemble target surrogate

• Test centering and static stability

• Perform vibration testing

• Perform cryo cycling test

Layering test

HGR shot

• Requires a full test target

• Test layering on ITPS

• Measure perturbation caused by support

• Use data to validate code prediction

• Measure perturbation growth at higher

Ta

rget

Fab

ric

ati

on

Te

sts

NIF

Exp

eri

me

nts