[PPT] - Diagnosing Implosion Performance at the NIF by Means of PowerPoint Presentation

SLIDE 1

Diagnosing Implosion Performance at the NIF by Means of Neutron-Spectrometry and Neutron-Imaging Techniques

Presentation to 24th IAEA Fusion Energy Conference San Diego, CA, USA October 8-13, 2012 Johan Frenje on behalf of the NIF team Massachusetts Institute of Technology

SLIDE 2

Collaborators

UR

J. Knauer
V. Glebov
T. Sangster
C. Abbott
R. Betti
M. Burke
T. Clark
N. Fillion
V. Glebov
T. Lewis
O. Lopez-Raffo
J. Magoon
P. McKenty
D. Meyerhofer
B. Rice
P. Radha
M. Romanovsky
J. Szcepanski
M. Shoup
R. Till

MIT

D. Casey
M. Gatu Johnson
C. Li
M. Manuel
H. Rinderknecht
M. Rosenberg
F. Séguin
N. Sinenian
A. Zylstra
R. Petrasso

GA

J. Kilkenny
A. Nikroo
L. Reny
M. Farrel
D. Jasion

SNL

R. Leeper

LANL

G. Grim
N. Guler
J. Kline
G. Morgan
T. Murphy
D. Wilson

LLNL

R. Ashabranner
R. Bionta
E. Bond
J. Caggiano
M. Eckart
D. Fittinghoff
E. Hartouni
J. McNaney
M. Moran
D. Munro
S. Sepke
P. Springer
D. Bleuel
A. Carpenter
C. Cerjan
J. Edwards
B. Felker
S. Glenzer

Imperial College

J. Chittenden
B. Appelbe
S. Hatchett
R. Hollaway
O. Jones
R. Kauffmann
D. Koen
O. Landen
J. Lindl
D. Larson
S. Le Pape
M. Mckernan
A. Mackinnon
E. Moses
H. Park
P. Patel
R. Prasad
B. Remmington
R. Rygg
V. Smalyuk
P. Springer
R. Zacharias
M. Yeoman

2 Johan Frenje – IAEA 2012

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

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Summary

The neutron data have been essential to the progress of the experiments on the NIF

The neutron-spectrometry data indicate that the tuning campaigns have improved

the implosion performance by ~50× since the 1st shot in Sept 2010.

We have achieved a radial convergence of ~35, fuel ρR values up to ~1.3 g/cm2,

and inferred hot-spot pressures up to ~150 Gbar.

The maximum pressure is ~2× lower than point design, and the observed neutron

yields are 3-10× lower than expected.

The pressure and yield deficits are most likely explained by higher than predicted

fuel-ablator mix and ρR asymmetries often observed in the implosions.

A path forward to address these issues has been defined.

3

SLIDE 4

4

Primary neutrons (n):

Yn
Ti
Residual kinetic effects

Scattered neutrons (n’):

rR

rR (g/cm2)  21dsr10-12 MeV

1)

dsr Y Y R

n n 



'

r

2 D i

E T  

Johan Frenje – IAEA 2012

The neutron spectrum is used to diagnose neutron yield (Yn), ion temperature (Ti) and areal density (ρR)

1014 1015 1016 1017 1018 1019 5 10 15 20 Yield / MeV MeV

D

E  Ignition Measurement of the detailed shape of the low-energy part of neutron spectrum provides 3D information about implosion

1) J.A. Frenje et al., these proceedings; to be submitted to Nucl. Fusion.

Neutron spectrum

n n’

SLIDE 5

Primary and scattered neutrons are imaged to diagnose neutron- source size (R) and thickness of high-density shell (R), resp.

Neutron images

5 Johan Frenje – IAEA 2012

Primary neutrons (n):

R of neutron source

Scattered neutrons (n’):

R of high-density shell

Hot DT core High-density Shell (R) Neutron source (R) n' n' n High-density shell Neutron source

50

50

μm

Images of neutron source and high-density shell

G. Grim et al., APS invited (2012).

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Several neutron spectrometers and an imaging system have been fielded at various locations on the NIF

MRS (77-324) NITOF/NIS (90-315) Spec-E (90-174) Spec-A (116-316) nTOF4.5m (64-330) nTOF3.9m (64-275)

M. Gatu Johnson et al., RSI (2012).

F.E Merrill et al., RSI (2012).

6 Johan Frenje – IAEA 2012

Neutron spectrometry and neutron imaging

This provides good implosion coverage for reliable measurements of Yn, Ti, rR, and rR asymmetries

SLIDE 7

10

12

10

13

10

14

10

15

5 10 15 Neutron energy [MeV] Yield / 100 keV 10

2

10

3

10

4

5 10 15 Counts / MeV Deuteron energy [MeV]

Single-scattering Primary peak (unscattered) Neutron spectrum Single-scattering Primary peak MRS spectrum1) Rn = 28 ± 3 μm

n n’

Rn’ = 44 ± 5 μm

Shot N120205 Yn = (5.6 ± 0.2)×1014 ρR = 900 ± 40 mg/cm2 Ti = (3.4 ± 0.1) keV

Johan Frenje – IAEA 2012

Spectra and images are now measured routinely

n the NIF (Example: DT shot N120205)

Data

7

1) J.A. Frenje et al., PoP (2010). 2) G. Grim APS invited, PoP (2012).

Neutron images2)

SLIDE 8

1013 1014 1015 1016 0.50 1.0 1.5 Yn rR [g/cm2]

Data

The spectrometry data indicate that the tuning campaigns have improved the implosion performance by ~50× since Sept 2010

3 2

47 1 15 2 3

. n

. R e . Y ITFx              r Lawson-type parameter2):

ITFx E E

losses





1) M .J. Edwards et al., PoP (2011); A.J. Mackinnon et al., PRL (2012). 2) R. Betti et al., OV/5-3

8

Implosion performance1): Sep 2010 Mar 2012 0.1 0.01 0.05 0.02 0.002 ITFx 1.0 0.5 0.2 0.005

Ignition conditions

Hot-spot energy: 3 kJ Alpha heating: 0.5 kJ Neutron heating: 0.3 kJ

Johan Frenje – IAEA 2012

Untuned 09/10 – 02/11 Symmetry 11/11 – 12/11 Shock timing 06/11 Mix/No Coast 03/12 – 07/12 Velocity 08/11 – 09/11

SLIDE 9

0.5 1.0 1.5 500 1000 1500 2000 2500 rR [g/cm2] R2 [m2]

Spectrometry and imaging data self-consistently indicate that the tuning campaigns have improved the convergence by ~2×

Data

9

Untuned 09/10 – 02/11 Shock timing 06/11 Velocity 08/11 – 09/11 Symmetry 11/11 – 12/11 Mix/No Coast 03/12 – 07/12

Sep 2010 Mar 2012

2

2 4         R R m R

fuel

  r

Sept 2010 R2 data inferred from x-ray images.

(fit to all neutron-imaging data)

16 . 49 .    R R

High-density fuel shell Source R ΔR

Johan Frenje – IAEA 2012

SLIDE 10

1012 1013 1014 1015 1016 1017

N110121 N110212 N110608 N110620 N110826 N110908 N111029 N111112 N120114 N120131 N120213 N120311 N120321 N120405 N120417 N120626 N120720 N120808

Yn 100 200 300 0.0 0.50 1.0 1.5 2.0 Hot-spot pressure [Gbar] rR [g/cm2]

Inferred hot-spot pressure is ~2× lower than point design, and yields are ~3-10× lower than predicted

Data

What’s causing this pressure and yield deficit? Point design: ~300 Gbar Untuned 09/10 – 02/11 Symmetry 11/11 – 12/11 Shock timing 06/11 Mix/No Coast 03/12 – 07/12 Velocity 08/11 – 09/11 LASNEX 2D sim. HYDRA 3D sim. DATA Mar 2012 Sep 2010

10 Johan Frenje – IAEA 2012

1) P. Springer et al., IFSA (2011).

SLIDE 11

1014 1015 1 2 3 4 5 Yn Ti [keV]

The pressure and Yn deficits can be explained partly by larger than predicted CH-ablator mixed into the hot spot

11

Untuned 09/10 – 02/11 Shock timing 06/11 Velocity 08/11 – 09/11 Symmetry 11/11 – 12/11 Mix/No Coast 03/12 – 07/12

7 . 4 i n

T Y 

Fuel-ablator mix very significant The higher-convergence implosions display more mix, which reduces Ti and Yn. Other data indicate that the “mix-performance cliff” occurs at a remaining shell mass that is ~30-40% larger than the point design

Johan Frenje – IAEA 2012

Data

SLIDE 12

0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0 MRS rR [g/cm2] Spec-E rR [g/cm2] 0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0 Spec-E rR [g/cm2] Spec-A rR [g/cm2]

The Yn and pressure deficits can also be explained partly by the systematic low-mode ρR asymmetries often observed

12

MRS Spec-E Spec-A 10-12 MeV 10-12 MeV Neutron measurements of un- scattered neutrons also indicate similar low-mode ρR asymmetries

Johan Frenje – IAEA 2012

Data

SLIDE 13

0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0 MRS rR [g/cm2] Spec-E rR [g/cm2] 0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0 Spec-E rR [g/cm2] Spec-A rR [g/cm2]

13

MRS Spec-E Spec-A 10-12 MeV 10-12 MeV Neutron measurements of un- scattered neutrons also indicate similar low-mode ρR asymmetries

Johan Frenje – IAEA 2012

Data

When using the 6-10 MeV range, Spec-E and Spec-A nTOFs probe similar portion of the implosion, and provide similar ρR values

6-10 MeV

SLIDE 14

Need to address the observed higher-than-predicted levels

f mix and low-mode ρR asymmetries
Understand the origin and structure of mix and low-mode ρR asymmetries.
Lower CR implosions (more 1D) should be examined and understood to improve the

modeling capabilities before conducting the high CR implosions necessary for ignition.

Engineering solutions and new diagnostic capabilities need to be implemented:

– Implement in-flight 2D x-ray radiography of the ablator. – Implement in-flight Compton radiography of the fuel. – Implement a new nTOF-neutron spectrometer for probing rR on the south pole. – Reduce size and/or patch up diagnostic holes and star burst, and reduce diameter of the fill tube to improve drive symmetry.

14 Johan Frenje – IAEA 2012

Path forward

SLIDE 15

Summary

The neutron data have been essential to the progress of the experiments on the NIF

The neutron-spectrometry data indicate that the tuning campaigns have improved

the implosion performance by ~50× since the 1st shot in Sept 2010.

We have achieved a radial convergence of ~35, fuel ρR values up to ~1.3 g/cm2,

and inferred hot-spot pressures up to ~150 Gbar.

The maximum pressure is ~2× lower than point design, and the observed neutron

yields are 3-10× lower than expected.

The pressure and yield deficits are most likely explained by higher than predicted

fuel-ablator mix and ρR asymmetries often observed in the implosions.

A path forward to address these issues has been defined.

15

SLIDE 16

SLIDE 17

2 4 6 8 2 4 6 8 Spec-E dsr [%] Spec-A dsr [%]

In contrast to the 10-12 MeV dsr data, the 6-10 MeV dsr data show no “rR asymmetries”

6-10 MeV 10-12 MeV

17 Johan Frenje – EPS 2012

Top view n' n' n' n' n' n' n' n'

 

 2 2 1 4 1

'

Cos A A E E

n n          

  

θ

Implosion performance data

SLIDE 18

A single scattering model cannot explain the low-energy neutron spectrum in high-rR implosions

MGJ—HTPD 2012 18 5/7/2012

IRF

rR asymmetries and multiple scattering may be important at energies below 9 MeV, and will be considered

primary single scatter

MRS data for Cryo DT, Nov. 12, 2011

single scatter primary

SLIDE 19

Neutron spectrum simulations indicate that multiple scatter is important in high rR implosions

MGJ—HTPD 2012 19 5/7/2012

More sophisticated analysis of the neutron spectrum is currently being developed rR=2.0 g/cm2 rR=0.2 g/cm2

SLIDE 20

The MRS measures the neutron spectrum, using the recoil technique combined with a magnetic spectrometer

Principle





 f t

x

d r nd n d

dx dx ) E ( dE Cos 1 2 Cos E 9 8 E   3-20 MeV (d)

x0 Neutron (En) r Deuteron (Ed) tf nr

CR-39 (5×7cm2) Implosion 26 cm 570cm CD-foil n 300 m 400 m

45 tracks

J.A. Frenje et al., Phys. Plasmas 17, 056311 (2010)

20 Johan Frenje – IFSA 2011

SLIDE 21

The background in the dsr region is determined from DT exploding pushers, then subtracted to get dsr for DT cryo shots

MGJ—HTPD 2012 21 5/7/2012

10-12 MeV 10-12 MeV

DT Exp Push, Nov. 21, 2011 Cryo DT, Nov. 12, 2011 Spec-A/Spec-E/IgnHi

Time [ns]

dsr = 4.80.4% Ti=3.490.40 keV Ti=5.680.64 keV dsr = 3.90.2% Ti=3.530.38 keV Ti=5.350.59 keV

SLIDE 22