Assembly of Complex Hydrodynamics Targets for Advanced Radiography Capability (ARC) on The National Ignition Facility

(NIF)

National Ignition Facility • Lawrence Livermore National Laboratory • Operated by the US Department of Energy

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and General Atomics𝟏 under Contract DE-NA0001808.

Advanced Radiographic Capability

• ARC has been integrated onto an existing set of four NIF

beam lines to facilitate reuse of the existing NIF main

amplification system.

ARC on NIF

Configuration of ARC on NIF

Using ARC, NIF researchers will be able to record the

physics of targets at 50 billion frames per second

ARC Imaging

ARC Diagnostic Targets

• There have been two diagnostic targets designed and built to

evaluate the performance of the complex hydro ARC platform.

• The first platform is a high energy backlighter (HEBL) target

that is designed to test the performance of the silver micro

wire and take an image of a calibrated mesh grid to establish

resolution and background

HEBL and PQ Targets

Back lighter standoff of

28mm from Au

mesh grid

10um Ag wire suspended

on .5mm X .5mm

Kapton sheet

37mm square mesh

resolution grid to establish

BL performance

• ARC uses a split-beam configuration, propagating two

short-pulse beams for each NIF aperture. Staggering the

arrival of the eight ARC beamlets onto special back-lighter

targets will enable creation of an x-ray “movie” with tens of

trillionths of a second resolution

• The second experimental platform is hohlraum driven with

a 2.5mm diameter copper foam sphere tented in the center

that represents the image of the sphere

Back lighter standoff of

28mm from center of the

hohlraum with 32mm

resolution grid on the side

2.5mm copper foam

sphere tented with 90nm

formvar in the center

of the hohlraum

10mm Ag wire position

with 50mm of the center

of the hohlraum

ARC Pre-Qualifier (PQ) Target

Platform Evolution

• First shot results showed 3 unwanted sources of x-rays

contaminating the image

Eliminating Extra X-Ray Sources

Kapton substrate source

causing a smeared image

“Blow-by” source caused by

ARC passing the backligher

and interacting with other

target materials

Double image caused by

boron fiber holding the

backlighter

• The smearing caused by the Kapton was reduced be using

the Type 2 backlighter with a smaller area, unfortunately it

also increased the effect of the blowby source.

• The blowby source took more effort to mitigate.

The unconverted light shield went through several redesigns

to try to mitigate the blow by source.

• The boron fiber that supports the backlighter substrate had

a 10um tungsten core that acted like a second backlighter

producing the double image. The boron fiber was replaced with

a silicon carbide stalk of the same size, mitigating this source

Original unconverted

green CH light shield

10um Al coated onto the shield and

backing plate as well as

5mm of parylene

Cone to protect the ARC beams from

interaction with unconverted lightThicker shield

without holes

• The Fineline green additively manufactured plastic was

transparent to 75% of the NIF unconverted light. 10um of

Aluminum was added onto the shield eliminating this source.

An exit cone was added to allow the arc beam

to exit after passing the backlighter without

interacting with the CH shield and to keep the

unconverted light from entering

BL Type 1: .5mm x.5mm x.008mm

Kapton sheet with .010mm x.5mm

Ag wire centered

BL Type 2: .3mm x.250mm x.008mm

Kapton sheet with .010mm x .300mm

aligned to the top edge of the Kapton

Platform Completion

TanDM mounted target with 35mm

backlighter standoff, smaller Type 2 BL

substrate and ARC exit cone

Cryo Tarpos mounted target 28mm backlighterstandoff, larger Type 1 BL and no exit cone

• The first successful shot was fielded in December 2016 with

a longer backlighter standoff. The longer standoff distance

removed the backlighter from the unconverted light created

when the main NIF beams are fired into the hohlraum. This

target used the smaller backlighter and substrate and allowed

ARC beams that missed the backlighter to travel out the exit

cone without interacting with other materials. The 35mm

standoff distance provided a lower resolution image than the

28mm standoff.

Successful ARC Pre Qualifier Targets

• The second successful shot was fielded in January 2017 with

the original 28mm standoff. The exit cone was abandoned and

the larger Type 1 backlighter was employed to absorb all of the

ARC beams, eliminating the possibility of blow by. The Type 1

backlighter creates more image smearing, which is an

acceptable trade off given the higher image resolution

Matthew Arend, Richard Seugling, Danielle Hare, Jonathan Ward, Randy Strauser1, Dawn Lord, Richard Vargas, Donovan Casaray

Complex Hydrodynamics and ARC

• LLNL researchers needed a new imaging capability that

could help them understand how shockwaves and

material features evolve under extreme conditions

important to stockpile stewardship. While the ARC laser

system was commissioned in 2015, developing the

experimental platform capable of acquiring high-quality

data for Complex Hydro took over a year, requiring the

team to resolve numerous design and system

integration problems

HEBL HEBL PQ

First Complex Hydro ARC Radiograph

Now that the capability has been successfully demonstrated,

the team is moving forward with the first programmatic data

shot in March 2017

Successful ARC PQ Radiograph

High Energy Backlighter Target (HEBL)

P2661734

ARC Backlighters