LLNL-PRES-725785

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 and by General Atomics under Contract DE-AC52-06NA27279

Down-Selection Methodology for Alternate Capsule Support

Target Fabrication Meeting 2017

Contributions by E. Alger, C. Aracne-Ruddle, D. Barker, S. Bhandarkar, J. Bigelow, T. Bunn, C. Choate, J. Crippen, J. Florio, M. Havre, C. Heinbockel, J. Jaquez, S. Johnson, J. Kroll, A. Nikroo, N. Rice, H. Robey, V. Smalyuk, M. Stadermann, R. Strauser, X. Lepro Chavez, and others

Presented March 15, 2017

Presented by Sean Felker

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Overview of the candidate solutions

The aggressive one year timeline and limit of personnel required the rapid elimination of time spent on the least feasible designs.

Field a layered cryogenic

target with its capsule

suspended in the hohlraum by

means other than the

traditional tent

A surplus of concepts and a

shortage of resources

The Purpose

The Problem

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An Analogy: Photos Of My Kids At The Beach

http://previews.123rf.com/images/alenkasm/alenkasm1207/alenkasm120700007/14384037-Group-of-kids-playing-at-the-beach-Stock-Photo-

children.jpg

Practical Reality Does Not Always Match Conceptual Ideas

Concept Reality – Felker kids, Dec 2016

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The Gauntlet

A sequence of tests designed to rapidly eliminate impractical designs, and develop/troubleshoot the most promising ones

Sanity

CheckMaterials Feasibility Assembly Stability Layering

Description

Conceptual

assessment

to weed out

impractical Poster by

Aracne-

Ruddle

Proof of

concept with

available

materials

Initial capsule

positioning,

survivability

Mechanical

vibration and

thermal

positioning

DT Ice layer

with control

of quality

and

thickness

ResourcesExperience,

discussions

Scrap parts,

rapid

prototype,

available

tools

Practice

parts, custom

tools

Practice

parts,

refined tools,

Proofing

stations, NIF

Production

parts &

tools,

Proofing

stations, NIF

Increasing difficulty and cost per test cycle

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Feasibility – 4-Part Hohlraum Vacuum Wand

Could a vacuum wand that was small enough

to facilitate assembly also be strong enough to

lift a capsule?

The Concern

The capsule wand needed to

maintain vacuum while this

400um hole was closed around

it. Unlike traditional targets, the

wand could only be retracted

after the assembly was closed.

Using successively smaller hypodermic tips

and a spare capsule, the smallest reliable ID

was ~250 um. One whole hour was invested.

The Conclusion

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Feasibility – 4-Part Hohlraum Wand Threading

Could a 250um ID wand be “threaded”?

The Concern

A production capsule wand with multiple diamond turned surfaces –

lead time approx. 3 months

With minimal time invested, demonstrated that a 4-part hohlraum

assembly could follow standard assembly strategies.

The Conclusion

Found some excess Polymicro® tube which

had a 260um ID. Peeled the polyimide coating

off with a scalpel and ended up with a 320um

OD glass tube.

Glued the glass tube into the end of an

obsolete production capsule wand.

Threading and de-

threading were tested.

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Feasibility – Annular Tent Support

Could a tent hold up a capsule without ripping? How would the geometry impact target design?

The Concern

The tent held up even under vibration, but the fill tube could slide along the edge of the tent and

the droop would require them to be offset from the equator. The design was abandoned.

The Conclusion

S. Bhandarkar & R. Strauser

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Feasibility – TetraCage Fiber Geometry

A simple setup to ensure consistent fiber tension

and to bond them in place.

Even after ALD coating, the spider silk was not stiff enough to suspend a capsule with an

acceptable level of sag. Since these were the only fibers that met the requirements for

diameter, the effort was directed to new fiber development. (Poster – Aracne-Ruddle)

The Conclusion

Could 4 fibers sufficiently constrain/locate a capsule? What length of the fibers would actually

be in contact with the capsule? What was the smallest diameter fiber that could be used?

The Concern

First prototype – 12um PE

fibersSpider Silk Prototype

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Feasibility – Wire Supported Fill Tube Strength

S. Bhandarkar & R. Strauser

Would a capsule and 10um

fill tube assembly survive

when cantilevered under its

own weight? What cantilever

lengths?

The Concern

If the fill tube was rigidly supported 200-

300um from the capsule, it had a correctible

sag and survived basic handling. Further

work was launched to investigate physics

requirements for support size/material.

(Presentations - Weber, Crippen, Alfonso)

The Conclusion

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Feasibility – 3-Part Fill Tube Geometry

~280um

Would the capsule droop necessitate new assembly strategies?

The Concern

Only minor hohlraum updates were required to accommodate the geometry.

The Conclusion

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• Verified successful process & tools

• Met Capsule positioning specs

• Demonstrated robustness of

completed assembly

Assembly – 4-Part Hohlraum Closing

1. Membrane bonded, 2 of the 4 hohlraum components assembled.

2. Threaded capsule and diagnostic band suspended between the two

hohlraum subassemblies.

3. Hohlraum closed around wand. 4. Wand retracted out of hohlraum.

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Assembly – Wire Supported Fill Tube Diagnostic Band

• Verified capsule could be positioned using wire

inside Diagnostic Band (Poster – Bigelow)

• Provided measurements of fill tube geometry

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Assembly – 3-Part Fill Tube Diagnostic Band

SEM by X. Lepro Chavez

• Verified capsule

positioning via

fulcrum

• Reiterated the

common failure mode

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Stability – Wire Supported Fill Tube @ Cryo

@ ~18K

SiC support, Room Temp SiC support, ~18K

Al support, Room Temp Al support, ~18K

• Demonstrated unacceptable sag

for SiC support

• Verified mitigation with Al

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Stability – 4-Part Hohlraum Vibration & Cryo

Capsule was centered when

built, and stable during

handling with 150um indent.

During the cryo proofing cycle, the capsule “danced” away from center as it

was shaken by the pump and the membranes relaxed. Incredibly, the

membranes and fill tube stayed intact.

• Tradeoff between indent level

and contact diameter optimized

at ~200um after 12 builds

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4-Part Hohlraum – Survived the Gauntlet!

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Backup SlideOther examples of practical reality not matching concepts

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Backup SlideOther examples of practical reality not matching concepts

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Backup SlideOther examples of practical reality not matching concepts