National Ignition Facility Status - Lawrence Livermore ... Ignition on the NIF requires extremes in...

National Ignition Facility Status

Progress towards ignition on the NIF John Edwards February 13, 2013

LLNL-PRES-618914

2

Ignition on the NIF requires extremes in density and temperature

Edwards—APS DPP Oct. 30th , 2012 NIF-0000-00000.ppt

DT hot spot ~ 3.5keV

~ 100 g/cc

~ 100 µm

α

Dense DT shell ~ 1000 g/cc

"PdV " ~ Pv

n2Z 2T1 2n2T ~4

e-

T 5 2∇T

Pressure ~ 350 Gbar Fuel ρR ~ 1.5 g/cm2

3

NIF has made good progress towards achieving the conditions necessary for ignition

Edwards—APS DPP Oct. 30th , 2012 NIF-0000-00000.ppt

DT hot spot ~ 3.5keV

~ 100 g/cc

~ 100 µm

α

Dense DT shell ~ 1000 g/cc

"PdV " ~ Pv

n2Z 2T1 2n2T ~4

e-

T 5 2∇T

Pressure ~ 350 Gbar Fuel ρR ~ 1.5 g/cm2

~ 150 Gbar ~ 1.3 g/cm2

Status

~ 3 keV ~ 50 g/cc

~ 5-800 g/cc

•  Peak neutron yields are ~ 1015

•  ~ 3-10X from alpha dominated regime

Hohlraum Wall: Au / Au-lined U

Laser Beams (24 quads each end, 2 rings on the hohlraum wall)

Hohlraum Fill He at 0.7 mg/cm3

10mm

Capsule fill tube

Solid DT fuel layer

Cryo-coolingRing

The ignition point design has a graded doped CH capsule in a Au/DU hohlraum

CH ~1110 µm

~70 µm

~195 µm

Si-doped layers (2-4% peak)

d

4 Edwards—APS DPP Oct. 30th , 2012 NIF-0000-00000.ppt

The NIF ignition point design was set by codes calibrated against experiments on Nova and Omega

Nova / Omega ~ 20 kJ

NIF ~ 1.8MJ

~ 10 mm ~ 20ns, 4-step pulse

~ 2.5 mm ~ 2ns, 2-step pulse

•  Physics uncertainties remained at NIF scale •  The point design included an experimental campaign and

evolution in the point design was anticipated based on results

Gas filled capsules Convergence ratio ~ 20

Cryo layered capsules Convergence ratio ~ 40

~ 2

C


The point design drove demanding technical requirements

9.4mm

° ° ° °

C

CH

Si-doped layers

Doped plastic cryogenic layered point design


Point design set requirements on implosion properties to achieve the stagnated fuel conditions for ignition

Velocity

Shape

Adiabat

Mix M S

V α

DT Hot spot

DT Ice

Ablator

HS

Hot e- PdV power to heat

hot spot

High compression for ρR – trap alphas, and confinement

Radiative cooling Efficient conversion of implosion KE to hot spot thermal energy

RHS

ΔR


Most of the experimental requirements set by the point design have been ~ met individually

Velocity

Shape

Adiabat

Mix M S

V α

DT Hot spot

DT Ice

Ablator

HS

RHS

ΔR

< 100ng RMS hot spot shape < 10%

α  ~ 1.5 ρR ~ 1.2-1.3 g/cm2

V ~ 350-370 km/s

But variable

CH mix in hot spot < 100ng

α  ~ 1.5 ρRDT ~ 1.45 g/cm2

VDT ~ 370 km/s

RMS hot spot shape < 10%

But variable

TRAD > 300eV


The principal issues and go-forward strategy were summarized in NNSA’s report to Congress

•  Nuclear yields are ~ 3-10X from alpha dominated regime - hotspot densities, pressures are ~ 2-3X lower than predicted/required

•  Performance deficit likely due to combination of low mode X-ray drive asymmetry/cold fuel shape, and higher than simulated hydrodynamic instability

Identifying the reasons for the deficit in pressure/performance and developing mitigation strategies is a key element of the go-forward experimental plan


y y

Hot spot Implosion instability

Evidence - low mode fuel asymmetry Zirconium neutron activation detectors indicate significant fuel ρρR asymmetry ~ 50-100%

1.00 1.05 1.100.90 0.950.80 0.85

+1 g/cm2 +500 mg/cm2 -250 mg/cm20

Y/Ywell

ΔρR

Low signal (high fuel ρR)

High signal (low fuel ρR)

•  Average ρR ~ 1 g/cm2

•  ~ 50% variations

Low order fit to > 13MeV neutrons 90Zr(n,2n) ⇒ 89Zr


l lρρρρρρρρR

Evidence – Mix Implosion performance correlates with mix in layered DT implosions

100 1000 100000.01

0.1

Mix mass (ng)

2D Y

OC

2D YOC (Hol Sim) vs. Mix mass

0914

1112

1215

01260131

0205

0213

0219

0311

0316

0321

0329

0405

0412

0417

0422

0626

0716

0720

0802

0808

CoastNo Coast

Edwards - Final NIC Status Update Meeting, 11/13/12 12 2012-044166s2.ppt

n

hν

Progress requires experiments for relevant physics > 15 platforms developed and growing

Author—NIC Review, December 2009 13 NIF-0000-00000s2.ppt

Progress requires state of the art diagnostics ~ 60 and growing


1st gen keyhole – shock timing at waist

time

shocks

equator


time time

2nd gen keyhole – dual-axis (P2)

shocks

pole

equator equator


pole

equator

45°

Au shield Al mirror

tor

time

−100

0

100

Position (μm

) 1 2 3 4

Equator

Pole θ=45

time

time


shocks

pole

equator

3rd gen keyhole – tri-axis (P1,2,4,m4)

equator


pole

equator

45°

Au shield Al mirror

tor

time

−100

0

100

Position (μm

) 1 2 3 4

Equator

Pole θ=45

time

time

time


shocks

pole

equator

3rd gen keyhole – tri-axis (P1,2,4,m4)

equator

1st gen layered keyhole (DT release)

Streaked radiography providing greater insights on implosion dynamics

FOV: 1ns x 0.3mm 4 R(t) points

Gated imager 2009

Streaked imager Peak velocity msmnt Early 2012

Long backlighter* Extended implosion msmnt N121008

FOV: 2.8ns x 0.6mm

FOV: 4.6ns x 0.9mm

4.6ns 4

Backlit Shell implosion

X-ray bang time

Explosion

Fidu wire

Acceleration

Peak velocity

2.8 ns 2n

CH (Si2%) capsules in DU hohlraums Laser drive: 330 TW; 1.4 MJ

Implosions were slower than the standard hydra high flux model – drive or ablator efficiency?

Hydra HFM

Hydra HFM X 0.87

Time (ns)

CO

M ra

dius

(μμm

)

Measured trajectory requires predicted hohlraum drive to be reduced to ~ 85%

data

?

Progress in understanding the 1D implosion Viewfactor shows X-ray drive on the capsule is lower than simulated by ~ 85%

With the reduced drive the CH rocket curve ~ agrees with data within errors

Hydra HFM

Hydra HFM X 0.87

Time (ns)

CO

M ra

dius

(μμm

)

Measured trajectory requires predicted hohlraum drive to be reduced to ~ 85%

data

Recent analysis – in-flight thickness becoming consistent with simulations

Data

Simulation

100 % LEH (5.75 mm)

6.7

mm

( )

96 beams

CAP“thin (3 m20 μmCH s

32 beams (only inners)

(

96 bebeaeaeaeams

100 % LEH (5.75 mm)

6.7

mm

CAPC“th

(3 m20 μ

H H

3232323232322232(onlynlynlylylyynlyly

H

2CHCH

3232 32 beamsyy inners)

?

Backlighting evolved to 2D imaging - “2D ConA” is obtaining excellent data

TC(0,0)

+tim

e

Gated images of imploding capsule on 2-strip camera

N121004

The capsule starts at 2mm diameter

~2 mm

215 µm 2µ


~2 mm

1.1 mm

212

1

We are in the process of obtaining 2D images of the complete implosion history – 2DConA

Bang time – 600ps

~2 mm

N121004 215 µm 2µ


~2 mm

We are in the process of obtaining 2D images of the complete implosion history – 2DConA

Bang time – 300ps

~2 mm

N121004 215 µm 2µ

Early hot spot formation


~2 mm

120 µm 120 µm

Despite cold fuel asymmetry the hot spot looks quite round

2 mm

215 µm 2µ


2 mm

Bang time DT shot N120716

Next generation of backlighting experiments will study ablation front instability growth

Sc foil

Pre-imposed ripples on capsule

4.3 keV X-rays 4.3 keV X-rays

Keyhole design for single pass radiography

Time sequence of gated X-ray images of perturbation growth

time

Moses_ John Szymanski & Pat Falcone, Nov. 15, 2011 33 NIF-1111-23687

nn' n'

Neutrons measure temperature and fuel ρρR

33 5/7/2012 MGJ—HTPD 2012

Yn: Y13-15 MeV dsr10-12 MeV = Y10-12 MeV/Y13-15 MeV

High density DT shell DT gas core

TD

n

DD

gasn

'

T

n'

n' n

Neutron mean-free-path ~ 4 cm2/g ρR is~ linearly proportional to DSR

ρR (g/cm2) ≈21×dsr10-12 MeV

Dunne—CLEO 2012, San Jose, May 10, 2012 34 2012-030585.ppt

(nTOF20-SpecA, nTOF20-IgnLo, nTOF20-IgnHi)

(nTOF20-SpecE)

Good design has produced unprecedented data quality

Location of NToFs on the NIF Target Chamber

Tion and ρR also measured by multiple Neutron Time of Flight (NToF) detectors


g

South pole nToF

We continue to improve nuclear measurements- lower background detectors open many exciting possibilities


0

0.25

0.5

600 800 1000 1200

Volta

ge (a

rb)

Time (ns)

D2 data for low ρR

Xylene Bibenzel

n

n' n'

High density DT shell

DT gas core

TD

n

DD

gn

T

n'n’'

ity

as cnn

'n’'

n

0.0

0.5

1.0

1.5

600 800 1000 1200

Sign

al (V

)

Time (ns)

DT unscattered

DT single scatter

D2 unscattered

DT back scatter

TD

Static isobaric model can be used to estimate hot spot properties

37

Hotspot

Y ~ Vol x tburn x <σv ~ T4.5> x n2

Measure neutrons γγ-rays X-rays

R p

R Cold shell

Density, ρ ~ nA Mass, MHS ~ ρV Pressure, P ~ nT Energy, E ~ P V

•  More sophisticated 3D model fits to the observables, allows for spatial profiles but gives similar answers

NIF-1011-23499.ppt Edwards - NNSA Ignition Review, Oct. 28, 2011

Vol x tburn x <σvv ~ T4.5>

t

x n2

Derive

BI3.00002: Cerjan

Pressure scales with velocity3 as expected

260 280 300 320 340 360 38030

50

100

200

300

400

500

06030608

0620 0826

0904

09080914

1029

1103

1112

1215

01260131

0205

0213

0219

0802

0808

0920

Velocity (km/s)

Pre

ssu

re (

Gb

ar)

Pressure vs. Velocity

Pres Vel3

Coast Point design


Pressure scales with velocity3 as expected – but are low compared to post shot simulation*

260 280 300 320 340 360 38030

50

100

200

300

400

500

06030608

0620 0826

0904

09080914

1029

1103

1112

1215

01260131

0205

0213

0219

0802

0808

0920

Velocity (km/s)

Pre

ssu

re (

Gb

ar)


Pres Vel3

0126

0131

0205

0213

0219

Coast

1D Hydra 0219219219

ydra

Point design

* Post shot simulations adjusted to match shock timing and implosion velocity Edwards - Final NIC Status Update Meeting, 11/13/12 39 2012-044166s2.ppt

No coast implosions improved pressure but remain below post shot simulation*

260 280 300 320 340 360 38030

50

100

200

300

400

500

0311

0316

0321

0329

04050412

04170422

0626

0716

0720

Velocity (km/s)

Pre

ssu

re (

Gb

ar)


Pres Vel3

CoastNo Coast

1D Hydra dra d

Point design

* Post shot simulations adjusted to match shock timing and implosion velocity Edwards - Final NIC Status Update Meeting, 11/13/12 40 2012-044166s2.ppt

3D sim Exp0

2

4

6

8

10

12

14

1D sim

En

erg

y (k

J)Energy in the hot spot is typically 30% of simulated

½ Mv2

α-heat α-heat

α-heat

DT fuel energy partition at stagnation (N120205)

0 1 2 3 4 5 6 70

1

2

3

4

5

6

7

Sim hot spot energy (kJ)

Exp

ho

t sp

ot

ener

gy

(kJ)

Hot spot energy

50%

25%

0126

0131020502130311

03210405

“ ½ Mv2 ”

Yield

KE Rad loss Cold fuel Hot spot

alphas Hot spot energy

3D sim Exp0

2

4

6

8

10

12

14

1D sim

En

erg

y (k

J)

ααααα tt-heattheatα t -heattheat

αααααα heat-heath t

“ ½ Mv2 ”

Yield

KE Rad loss Cold fuel Hot spot

t tt alphas Hot spot energy aH

(N120205)

New DT implosion - higher adiabat implosion lower convergence

•  Reduced RM/RT predicted

•  Different hohlraum physics

•  Different ablator path (EOS, NLTE physics)

α ~ 2.3 implosion

α ~ 1.5 implosion

Simulated implosions

α~2.3, 380 km/s 14.9 ns

α~1.5, 320 km/s 22.2 ns

CR~27-36

CR~36-47


Hurricane et al

We have made good progress towards achieving ignition conditions on the NIF

•  The NIF laser and targets have met the highly demanding specifications for accuracy and control required by the ignition point design (Rev5)

•  The hohlraum X-ray drive exceeded the ignition goal of 300eV accelerating implosions up to ~ 350 km/s, close to the goal of 370 km/s

•  The highest observed yields and areal densities to date in DT layered implosions are ~2.5kJ (~ 1015 neutrons) and ~1.3 g/cm2 (85% of the goal) respectively

•  Nuclear yields are ~ 3-10X from alpha dominated regime - hotspot densities, pressures are ~ 2-3X lower than predicted/required

•  Performance deficit likely due to combination of low mode X-ray drive asymmetry/cold fuel shape, and higher than simulated hydrodynamic instability

Identifying the reasons for the deficit in pressure/performance and developing mitigation strategies is a key element of the go-forward experimental plan


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