S. P. ReganUniversity of RochesterLaboratory for Laser Energetics

The National Direct-Drive Program: OMEGA to the National Ignition Facility

1

22nd Target Fabrication MeetingLas Vegas, NV

12–16 March 2017

00

100

200

300

400

500

20 40

Pth

(G

bar

)

60

Hot-spot energy Ehs (kJ)

80 100

100 GbarMitigated CBET

Current high-foot indirect drive*

Required: Phs = 350 to 400 GbarAchieved: Phs = 226!37 Gbar**

Energy-scaled OMEGA (Ehs = 0.44 kJ)†

Required: Phs = 140 GbarAchieved: Phs = 56!7 Gbar†

kJP Gbar E250 10hshs =

*O. A. Hurricane et al., Nature 506, 343 (2014).**T. Döppner et al., Phys. Rev. Lett. 115, 055001 (2015).

†S. P. Regan et al., Phys. Rev. Lett. 117, 025001 (2016).

Pressure threshold for ignition:

The goal of the National Direct-Drive Program is to demonstrate and understand the physics of laser direct drive (LDD)

Summary

E26038

• The 100-Gbar Campaign on OMEGA explores the formation of hot-spot conditions relevant for ignition at the 1-MJ scale

– improvements in OMEGA

– improvements in targets

– enhancements in diagnostics

– new modeling and simulation capabilities

• The Megajoule Direct Drive (MJDD) Campaign at the National Ignition Facility (NIF) investigates direct-drive physics at long-scale lengths

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The 100-Gbar Campaign requires a DT cryogenic fill-tube target.

Collaborators

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V. N. Goncharov, T. C. Sangster, E. M. Campbell, R. Betti,* A. Bose, T. R. Boehly, M. J. Bonino, D. Cao, R. Chapman, T. J. B. Collins, R. S. Craxton, A. K. Davis, J. A. Delettrez, D. H. Edgell, R. Epstein,

C. J. Forrest, D. H. Froula, V. Yu. Glebov, D. R. Harding, S. X. Hu, I. V. Igumenshchev, D. W. Jacobs-Perkins, R. T. Janezic, R. L. Keck, J. H. Kelly, T. J. Kessler, J. P. Knauer, T. Z. Kosc, S. J. Loucks, J. A. Marozas,

F. J. Marshall, R. L. McCrory,* P. W. McKenty, D. T. Michel, J. F. Myatt, P. B. Radha, M. J. Rosenberg, W. Seka, W. T. Shmayda, M. J. Shoup III, A. Shvydky, A. A. Solodov, C. Stoeckl, C. Taylor, R. Taylor, W. Theobald,

J. Ulreich, M. D. Wittman, K. M. Woo, J. D. Zuegel

University of Rochester*Also Departments of Mechanical Engineering and Physics & Astronomy

Laboratory for Laser Energetics

T. Bernat, J. Hund, and N. Petta

Schafer Corporation

M. Farrell, C. Gibson, A. Greenwood, H. Huang, M. Schoff, and W. Sweet

General Atomics

J. A. Frenje, M. Gatu Johnson, and R. D. Petrasso

Massachusetts Institute of Technology, Plasma Science and Fusion Center

M. Hohenberger

Lawrence Liversmore National Laboratory

M. Karasik, S. P. Obenschain, and A. J. Schmitt

Naval Research Laboratory

D. D. Meyerhofer and M. J. Schmitt

Los Alamos National Laboratory

The 100-Gbar Campaign on OMEGA and the MJDD Campaign on the NIF are underway to provide a detailed understanding of direct-drive physics

I2284a

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Spherical direct drive (SDD) on the NIF is the ultimate goal; polar direct drive (PDD) is secondary.

FY17 FY20 NIF SDD

Complete NIF SDDreconfiguration study

Perform first fill-tubeDT cryogenic

implosion on OMEGA

Demonstrate that direct-driveignition-scale coronal plasmas meet

laser–plasma interactions (LPI),energy coupling, and laser imprint

requirements on the NIF

Demonstration of 100 Gbar on OMEGA

OMEGA DT cryogenic implosions are hydrodynamically scaled from NIF ignition designs

TC12314h

5

0

1

0

2

3

2 4 6 8

Time (ns)

Po

wer

(×

102

TW

)

10 12

1.5-MJ, spherically symmetricdirect-drive design 26- to 29-kJ OMEGA cryogenic design

5

10

15

20

25

01 2

Adiabat and IFAR are controlledby pulse shaping

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Loweradiabat

Higheradiabat

40P

ow

er (

TW

)

Time (ns)

430

to 5

00 n

m

DT iceAblatorAblator

160 nm DT 160 nm DT

37 nm CH

DT gas

1700

nm

• Vimp and IFAR are controlled by varying the ablator (7.5 to 12 nm) and fuel thickness (40 to 66 nm)

• Vimp = 3.8 to 4 × 107 cm/s Adiabat a = 1.6 to 3 IFAR2/3 = 20 to 25 Convergence ratio (CR) = 20 to 23

Adiabata = P/PFermiIn-flight aspect ratio (IFAR) = shell radius/ shell thickness

The hot-spot pressure is invariant (100 Gbar on OMEGA = 100 Gbar on the NIF)

*I. V. Igumenshchev et al., Phys. Plasmas 23, 052702 (2016); S. P. Regan et al., Phys. Rev. Lett. 117, 025001 (2016).

100-Gbar Team Leaders Objective

Laser power balance J. Kelly Minimize laser-drive nonuniformity

Fill-tube target D. Harding and J. UlreichImprove target quality (fill-tube target with polystyrene shellsand multilayer ablators)

Laser upgrades for CBET mitigation T. Kessler and D. Froula

Understand and minimize coupling losses caused by CBET (wavelength detuning, R75)

Implosion modeling/simulation P. B. Radha 2-D and 3-D simulations including CBET and hot-electron production

1-D implosion physicsand experiments R. Betti Continue to improve understanding

of direct-drive physics

Laser–plasma interactions J. Myatt and D. FroulaFundamental understanding of laser–plasma interaction (TOP9 beam on OMEGA)

Shock timing T. Boehly Measurement/modelingof shock timing

Diagnostics W. Theobald and C. SorceDevelop diagnostics to meet 100-Gbar Campaign requirements [3-D optical Thomson scattering (OTS)]

Laser imprint S. Hu Understand and minimize effectsof laser imprint

The 100-Gbar Experimental Campaign has nine areas of research

E26039

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Improvements to the OMEGA laser are required and ongoing research will refine these needs

E26040

80 Gbar (CH ablators)

1. On-target, overlapped laser intensity uniformity over 100 ps of 3% root mean square (rms)

100 Gbar (CH/Si/CH ablators)

1. On-target, overlapped laser intensity uniformity over 100 ps of 1% rms

2. Implementation CBET mitigation technique (spatial, spectral, or temporal)

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The on-target, overlapped laser-intensity uniformity depends on the laser power balance and the far-field intensity distribution of each beam on target.

Improvements in targets—development of a fill-tube target—are required and ongoing research will refine these needs

E26041

80 Gbar (CH ablators)

1. Target positioned at chamber center to <10 nm

2. Target quality

a) At shot time, fewer than ten particles in the range of 0.5 to 1.0 nm on the capsule surface and none > 1 nm with heights >0.05 nm

b) Inner surface roughness of ablator not to exceed vrms = 0.5 nm in modes , < 5 and vrms = 0.1 nm in modes , ≥ 5

c) At cryogenic temperature, determination of the target outer diameter to <2 nm

d) At cryogenic temperature, determination of target outer surface long wavelength (, < 10)

nonuniformity to < 0.1 nm

e) DT ice-layer thickness known to 0.5 nm

f) DT ice-layer density known to <5%

g) Determination of the ablator atomic composition and density (C:H:O:D:T) to <10%

h) Sphericity TBD

100 Gbar (CH/Si/CH ablators)

1. Target positioned at chamber center to <5 nm

2. Target quality

a) At shot time, fewer than ten particles in the range of 0.1 to 0.5 nm on the capsule surface and none > 0.5 nm with heights

> 0.05 nm

b) Inner-surface roughness of ablator as 80 Gbar

c) Target outer diameter as 80 Gbar

d) Target low-mode nonuniformity as 80 Gbar

e) DT ice-layer thickness as 80 Gbar

f) DT ice-layer density as 80 Gbar

g) Determination of the ablator atomic composition and density (C:H:Si:O:D:T) to <10%; [Si layer added for two-plasmon decay (TPD) mitigation]

h) Fill tube capability with glue spot <30 nm to fuel CH/Si/CH shells

• CDR for fill-tube target has been completed

• Target metrology workshop defined technique to characterize surface debris

• Delivery date of fill-tube target on OMEGA is Q1 FY20

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The DT cryogenic fill-tube target requirement for the 100-Gbar Campaign is based on three factors

E26042

1) Nonpermeable ablator materials are required to mitigate laser–plasma interactions

2) Minimizing target debris and defects

3) Minimizing radiation damage to the ablator

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Target debris is considered the main seed of short-scale mix

300

R =

80 n

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100

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40

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10

0

1.4

1.3

1.2

1.1

1.0

t(g/cm3) t(g/cm3) Zavg

Returnshock

Symmetric implosion Perturbed implosion

Neutron yield

Shot 66613

Neu

tro

n-a

vera

ged

tR

(m

g/c

m2 )

1012

102

103

1013 1014

4 ng2 ng

1 ng 0.5 ng 1-D

Mass injected into hot spotby mix

tR ~ Y1/4

TC10600

• Simulations include ~100 surface features, size: 1 to 20 nm in diameter, 0.5 to 1.0 nm in depth

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Characterizing cryogenic targets at the shot time is crucial for understanding target failure mechanisms.

Initial surface features are amplified during shock transit and shell acceleration

TC10595

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DTvapor

Time (ns)

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(T

W)

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1 2 3xlxl

Shellacceleration

Mass-density contoursShot 55722 glue spotShot 55722 glue spot

Local featureyl

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11 nm CD47 nmDT ice

R =

435

nm

360 440

ShocksShocks are launchedinto the shell

Hei

gh

t (h

)

Diameter (d)

Debrisparticle

.dh 0 1< is ablatively stabilized;

.dh 0 1> is unstable

Each feature produces a hole in the shell, injecting ablator and cold DT into the vapor region

E26045

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xlxl

Shot 55722 glue spotShot 55722 glue spot

yl

360

20

0

40

60

80

400 400440 360 440

t = 2.250 ns t = 2.500 ns

Injected mass as a result of instability growth should not significantly exceed the original vapor mass (0.14 ng in OMEGA targets)

E26046

• Injected mass from a single feature is ~4× m0 ~ 10–3 ng for an outer diam (OD) = 5 nm feature

• ~150 to 200 features are sufficient to inject 0.14 ng of cold material into the hot spot

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DTm0

Detailed metrology analysis shows hundreds of micron-scale features on glow discharge polymer (GDP) shells

E26047

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Polystyrene ablators are being explored in current experiments.

4-nm defect

Bright-field microscopy

Surface features in GDP, ~300 defects Polystyrene shells are much smoother(atomic force microscope)

0 0 1 2 3 4 5 6 7 8 90

–2

–4

–6

–8

100200

nm

nm x = 10 nmy = 10 nmz = 229 nm

A Ge tracer is used to track hydrodynamic mixing of the ablator into the hot spot

E25556a

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Time-integrated, spatially resolved Ge Hea + satellite emission from hot spot(dx = 150 nm*, de = 5 eV)

Sp

ace

Photon energy 100 n

m

83313: XRS1

Coronal plasma

Compressed shell

Hot spot

Mix at stagnation

DT ice(50 nm)

DTvapor

Layered DT cryogenic target

Ge-doped CH(8 nm, 0.7% atomic)

If Ge reaches the hot spot, it will emit K-shell emission.

* Similar spectrum recorded on same shot with dx = 40 nm and de = 5 eV XRS: x-ray spectrometer

0.0

9.8 10.0 10.2

Photon energy (keV)

Inte

nsi

ty (

J/ke

V/s

ter)

10.4 10.6 10.8

0.2

0.4

0.6Shot 83313 XRS1 calibrated

ExperimentBest fit1v fit

0.10

1

2

a = 2.5

3

1.0 10

Inferred mix mass (ng)

Pri

mar

y n

eutr

on

yie

ld (

×10

13)

100

The hot-spot mix mass inferred from the Ge Hea + satellite emission* will be used to constrain the simulations and refine the target requirements

E26048

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Inferred mix-massquantitiesTe: 2.5 to 3.9 keV (comparable to Ti)ne: 2 to 6 × 1024 cm–3

tRGe: 0.08 mg/cm2

Mix mass: 1 to 5 ng

Technique is sensitive to mass from Ge-doped ablator only.

*Similar to NIF hot-spot mix: B. A. Hammel et al., Phys. Plasmas 18, 056310 (2011).S. P. Regan et al., Phys. Plasmas 19, 056307 (2012).S. P. Regan et al., Phys. Rev. Lett. 111, 045001 (2013).

Target performance with the fill tube will be examined in FY17

E26049

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Fill tube with OD = 10 nm(Fill capillary with glue, exceptfor inner 0.1 mm)

Fill tube extends a maximumof 10 to 15 nm inside of theinner plastic ablator wall

Standard stalk-mountedDT cryo target

DT [50 nm] CH [8.0 nm]with standard OD

Fill-tu

be len

gth =

1.0 m

m

45º

E26038

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Summary/Conclusions

The goal of the National Direct-Drive Program is to demonstrate and understand the physics of laser direct drive (LDD)

• The 100-Gbar Campaign on OMEGA explores the formation of hot-spot conditions relevant for ignition at the 1-MJ scale

– improvements in OMEGA

– improvements in targets

– enhancements in diagnostics

– new modeling and simulation capabilities

• The Megajoule Direct Drive (MJDD) Campaign at the National Ignition Facility (NIF) investigates direct-drive physics at long-scale lengths

The 100-Gbar Campaign requires a DT cryogenic fill-tube target.

Backup

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A major advantage of direct drive over indirect drive is the increased coupled energy to the hot spot and relaxed hot-spot requirements

TC12311o

20

00

100

200

300

400

500

20 40

Pth

(G

bar

)

60

Hot-spot energy Ehs (kJ)

80 100

100 GbarMitigated CBET

Current high-foot indirect drive*

Required: Phs = 350 to 400 GbarAchieved: Phs = 226!37 Gbar**

|no a = 0.66***

Energy-scaled OMEGA (Ehs = 0.44 kJ)†

Required: Phs = 140 GbarAchieved: Phs = 56!7 Gbar†

|no a (energy scaled‡) = 0.64†

kJP Gbar E250 10hshs =

• Pressure threshold for ignition†

• Generalized Lawson criterion***

• Energy scaling***,‡

/

. /

P P R

Y M0 12

.

.DTstag

no ign no

no16

0 61

0 34

| x x t= =a a

a^^

hh

E E.

laserNIF

laserOMEGA 0 35a k

* O. A. Hurricane et al., Nature 506, 343 (2014). ** T. Döppner et al., Phys. Rev. Lett. 115, 055001 (2015). *** R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015); A. Bose et al., Phys. Rev. E 94, 011201(R) (2016). † S. P. Regan et al., Phys. Rev. Lett. 117, 025001 (2016). ‡ R. Nora et al., Phys. Plasmas 21, 056316 (2014).

Direct-drive ignition: CR ≥ 22 and Phs > 120 GbarIndirect-drive ignition: CR = 30 to 40 and Phs > 350 Gbar

The 100-Gbar program has 80 Gbar as a first near-term goal

E26051

• System requirements are less demanding for 80 Gbar

– power balance ~3% rms

– target placement <10 nm

– target quality (debris level)

• CBET mitigation and multilayer ablators are not required for 80 Gbar

– CH, CD ablators will be used

– laser upgrades for CBET mitigation should proceed in parallel

– multilayered ablators (Si) for TPD control should proceed in parallel

• “Touchstone” for physics/simulations

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The approach is to fix the laser-drive nonuniformity first, then mitigate CBET.

Shot with inferredPhs > 50 Gbar

3 5

1.4

1.6

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Fuel adiabat

Generalized Lawson criterion**

|sc

aled

2 4 6

Long wavelengths,short wavelength(debris, imprint) Long wavelengths (drive, offset)

1-D simulations

Experiment†

Without cross-beam energy transfer (CBET)

Long wavelength perturbations limit the hot-spot pressure on OMEGA; short wavelength perturbations affect low-adiabat implosions

E25536c

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* 2016 Inertial Confinement Fusion Program Framework, Office of Science and National Nuclear Security Administration, U.S. Department of Energy, Washington, DC, Report DOE/NA-0044 (2016).

** R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015); A. Bose et al., Phys. Rev. Lett. E 94, 011201(R) (2016).† S. P. Regan et al., Phys. Rev. Lett. 117, 025001 (2016).

Fuel adiabat a = P/PFermi

High-adiabat implosions (a ~ 7) are being investigated for the 1-D physics campaign.

/ .P P R Y M E E0 12. . .scaled ign no no

16DTstag

laserNIF

laserOMEGA0 61 0 34 0 35

| x x t= = a a^ a ah k k

A feature with a0 ~ 0.1 nm and d ~ 5 nm becomes nonlinear at the onset of acceleration

TC10597

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0.050.00

Are

al d

ensi

ty (

mg/c

m2 )

0

1

2

3

0.01 0.02

t = 0

t = 1.9 ns

0.03 0.04

i/r

.

.

ablatively stabilized

unstable

da

da

0 1

0 1

1

2

1

Po

wer

sp

ectr

um

(n

m2 )

10–4

10–3

10–2

10–1

100

101

102

103

104

105

10

Lowmodes(2–6)

Midmodes(6–25)

Highmodes

(26–150)

Mode number

Atomic force microscopy power spectra

100 1000

Excellent sphericityof polystyrene shells

NIF outer CH specificationTypical strong CDPolystyrene

General Atomics measures the low-mode surface roughness with the atomic-force microscopy sphere mapper

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The low-mode surface roughness target specification is being generated using multidimensional hydrodynamic simulations.