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PERSISTENT SURVEILLANCE FOR

PIPELINE PROTECTION AND THREAT INTERDICTION

Depleted Uranium Hohlraum Process

Improvements

Javier Jaquez1, Martin Havre1, Tim Fuller1, Jason Wall1, Jorge Robles1,

Karina Kangas1, Abbas Nikroo2, Suhas Bhandarkar2

1General Atomics, P.O. Box 85608, San Diego, California 92186-56082Lawrence Livermore National Laboratories, P.O. Box 808,

Livermore, California 94550

22nd Target Fabrication MeetingLas Vegas, Nevada

March 12-16, 2017

This work performed under the auspices of the U.S. Department of Energy by General Atomics under Contract

DE-NA0001808 and by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and

General Atomics IR&D Funds

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General Atomics has dedicated equipment for

to process DU in support of the ICF program

U3 PVD system U2 PVD systemLathe

4mm 1mm 1mm 1mm

• DU is processed in a safe manner in compliance with state and federal

regulations

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Depleted Uranium (DU) lined hohlraums have

advantages over Gold Hohlraums

• 30% less M-band radiation compared to Au allows for less

capsule pre-heat1

• Compared to Au hohlraums DU is more efficient in terms of

coupling incident laser energy into the capsule.– DU has a higher X-ray conversion compared to Au

– Less heat is absorbed into the wall with higher Z materials.

• ZAu=79, ZU=92

– Using less laser helps preserve the NIF optics

Hohlraum canIncident laser energy

1. N. B. Meezan, E. L. Dewald et al.,” http://meetings.aps.org/link/BAPS.2015.DPP.UO7.12

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DU Hohlruam specifications are fairly stringent

~5 mm

Au Hohlraum

wall TorusFlange

575 scalePhysics

requirements Assembly

requirements

DU layer

5.75mm

DU linerAu liner, (varies)

Length Diameter DU liner Au liner* Au wall O at%

9.43-

11.24mm

5.75-

6.72mm

>7µm 0.7µm 23µm <5at%

*optional

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The overall manufacturing process involves

many fabrication steps

E-Plate AuPVD Cu

Back-Machining Milling Leach CuLeach Al

Dimensional

Compositional

PVD DU/Au

Unlined hohlraums - Oxygen levels

NaOH NH4OH

Lined hohlraums - Au liner thickness

Auger Electron Spectroscopy

X-Ray Fluorescence

Defects

Nikon MM-400 (measured pre-leach)

Visual inspection

Turn Al mandrel

M1 coater U3 coater

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Oxy

ge

n a

t% in

DU

Lin

er

Until recently the oxygen levels in many DU lined

hohlraums have been higher than NIF spec

– Oxygen levels within the the DU liner were found to be trending upwards

with the previous process

– The most recent process modification involves a change at the Cu liner

Low yield

process:

25%

Overall Yield: ~65%

Overall Yield: ~52%

NIF Spec

5 at%

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The key process change was at the Cu liner

step

E-Plate AuPVD Cu

Back-Machining Milling Leach CuLeach Al

Dimensional

Compositional

PVD DU/Au

Unlined hohlraums - Oxygen levels

NaOH NH4OH

Lined hohlraums - Au liner thickness

Auger Electron Spectroscopy

X-Ray Fluorescence

Defects

Nikon MM-400

Visual inspection

Turn mandrel

M1 coater U3 coater

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Changes to our production process have reduced

oxygen levels within the DU for unlined hohlraums

• In-situ etch functionality was added to our DU coating

system

– Previously this was performed in-situ with Cu deposition

0.0%

10.0%

20.0%

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90.0%

0 500 1000 1500 2000 2500

Ox

yg

en

ato

mic

pe

rce

nt

nanometers

U3 In-situ old process

0.8at%4at%

300nm

• Active depth: 7um

• Important O remain low below 2um

depth (Active depth for foot)

• If high O level beyond 2um

the peak drive will be

affected

2000nm

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The ion etch process is not the same between

systems

• Parts farther from ion source in the U3 system

– 6cm vs. 3.5cm

• Ion etch rate in M1 system ~3x higher

– About ~200nm removed in U3, 30min

– About ~600nm removed in M1, 30min

0

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18-A

ug

7-S

ep

27-S

ep

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ct

6-N

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ov

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ec

5-J

an

25-J

an

etc

h r

ate

, n

m/m

in

M1 etch rate (Cu)

U3 etch rate (Cu)

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Cu liner deposition step was found to be key to

oxygen variability within DU

• In-situ ion source etching is

key to good adhesion…too

much etching can damage

the Cu liner

• Data shows correlation

between etch time and

oxygen level

• Can infer the state of the Cu

layer before the etchant

steps leads to variability

(pinholes, etc.)

Work produced in collaboration with

Suhas Bhandarkar @LLNL

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Direct evidence show leaching chemicals

oxidize DU

• AES was carried out on DU in

various states

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ato

mic

pe

rce

nt

nanometers

3 hr exposure 72 hr exposure

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0 1000 2000 3000 4000 5000

ato

mic

pe

rce

nt

nanometers

Oxygen Uranium Copper

Before any type of chemical leach exposure

After exposure to NaOH for 3 and 72 hrs

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0%

20%

40%

60%

80%

100%

0 20 40 60 80 100 120

CU

MU

LTA

TIV

E Y

IELD

part count

Unlined Overall Yield

Lined Overall Yield

With the current process the overall yield is

maintained while reducing the oxygen content

coat E-plate BM Mill Leach Overall

unlined 92% 98% 98% 100% 65% 52%

lined 89% 99% 99% 100% 94% 75%

Unlined

Lined

52%

75%

• Previous process overall yield for unlined

parts was 65% (45%)

**If we take high O

into account

Early issues with new process

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50%

60%

70%

80%

90%

100%

110%

0 20 40 60 80 100 120

CU

MU

LTA

TIV

E Y

IELD

PART COUNT

Unlined Coat Yield

Lined Coat Yield

DU coater yield with U3 in-situ ion etching >90%

• Historically this has been an issue with DU hohlraums

– Cu liner exterior etching introduced in 2015, brought coater

yield up to 96%

– Currently we’re better than the ex-situ Cu etching if initial startup runs are ignored, >95% for linerless designs

Lined

Unlined

Coater issues early on

92%89%

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Primary failure mode at the DU coating step is

mechanically related

Yield out of U3 is >90%6.5% fail due to coater issues (D4)

2% are dinged or scratched (D1)1.5% of parts have delamination (D2)

>1% fail due to embedded debris (D3)

101

13

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Pass Fail

U3#dep.#step#Pass/Fail

2

2

1

8

0 2 4 6 8 10

D1() ding/scratched(

D2() delamination

D3() embedded(debris

D4() coater(failure

Detailed(look(at(coating(failures

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50%

60%

70%

80%

90%

100%

110%

0 20 40 60 80 100 120

CU

MU

LTA

TIV

E Y

IELD

part count

Unlined Leach Yield

Lined Leach Yield

DU flaking away is the primary cause of failure

at the leaching step

Unlined

Lined

8

12

1

4

1

7

6

4

1

0 5 10 15

LC1 - DU flaking off (Large)

LC2 - DU flaking off…

LC3 - majority of DU missing

LC4 - Large area peeling

LC5 - DU cracking

LC6 - interior bubble*

LC7 - edge delamination

LC8 - black matte interior

LC9 - LEH deflection

Unlined Leach FC

65%

94%

Main failure mechanism (unlined)

400um

200um

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Part position within the coater makes a

difference

0 5 10 15 20

Coating

Failure

E-plaitng

Failure

Back-

machine…

Mill Failure

Leach Failure

Failure position by position

Position-5 Position-4 Position-2 Position-1

84%

60%

86%

19%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Position-1 Position-2 Position-4 Position-5

%Yield at leach step

Currently investigating:• Etch rate differences

• Coating flux differences

• Equipment

2

1

4

5

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Blisters are another defect of concern

Cracks (LC-5) Interior bubble (LC-6)

Edge delamination (LC-7)

• 12% of parts have blisters

• Any type of defect that is

perceived as possibly flaking

away is rejected as it could land

on the capsule causing meteors

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The rate of blister occurrence has not changed

with in-situ ion etching

• The addition of the in-situ ion etch has not increased the occurrence

of blister formation

• We are shipping more parts out with blisters now than in 2015

• 3.4x increase in DU demand in 2016 over 2015 levels

0

5

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15

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0 20 40 60 80 100 120

%o

f p

art

s th

at a

re b

list

ere

d

part count

M1 etched (old process)

U3 in-situ etched (new

process)

355

535

391

56

83

248

0

100

200

300

400

500

600

700

CY2014 CY2015 CY2016

ho

hlra

um

s sh

ipp

ed

Au components

DU components

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Conclusions

• Low-Z elements such as oxygen reduce hohlraum

drive

• By introducing in-situ ion etching into our process we

have drastically reduced oxygen levels within the DU

layer

• No difference in bubble occurrences between old

and new process

• Biggest issue we’re currently facing is leach process

failures

– Part position dependency observed

• 3.4 times as many DU hohlraums shipped in 2016

over 2015 levels

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