Nuclear Diagnostic & Physics at NIF

Notre Dame University, Notre Dame, IN10/27/2010

GSI-Helmholtzzentrum Seminar, Darmstad, Germany11/9/2010

D. Schneider / L. BernsteinLLNL

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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NIF-National Ignition FacilityDiagnostics (≈$90 M in FY11)

•X-ray diagnostics: ≈20 spectral, imaging and time-resolved diagnostics are planned/operational (developed over 25 years at NOVA, Omega etc.)

Very mature field

•Nuclear Diagnostics: needed for yields >1015-17 neutrons

• nToF, Neutron imaging, Activation, Charged-par ticle spectrometry, Radchem, Gamma Reaction History

First science proposals approved

(“Ride along” exper iments often allowed)

NIF Laser System: 192 laser beams produce 1.8 MJ, IR-UV 3ω=352nm, 2+ ns, 5x1014 Watt in 1mm2 spot)

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3

Cryogenic Layering Prototype Target

UNCLASSIFIED

UNCLASSIFIED

30μmwall

4

NIF Indirect Drive target schematic for NIC((NIC) National Ignition Campaign)

Typical Pulse Shape

Ablator (CH or Be)

DT Ice 0.255g/cc50/50 (0.01 3He)

DT gas fill (~1 3He)

(0.3mg/cm3@18K)Hohlraum Wall: – Au or High-Z

mixture (cocktail) Capsule (Be or Plastic, solid DT fuel)

Laser Beams in 2 Rings (24 Quads illuminate two Rings on HR wall)

Laser Entrance Hole with window

Thermal AlShield

He gas fill (1.3 mg/cc or He/H)

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Ignition REQUIRES that most of the α’s from D(T,n)αreaction are stopped in the nar row shell (≈20 µm) of high

areal density “cold” fuel

DTGas

areal density (“rho-R”)≡ ∫ρ(R)dR

α3.54

DT “Ice”

α0

60 µ

m

20 µ

m

This requires Elaser > 1 MJNIF is the first time that this is a possibility

Ignition means run-away thermonuclear burn

dnT

dt= −nT nD σ v & nT = nD =

n2

⇒ dndt

=−n2

2σ v

f ≈τconf

τburn=

n σ v R2 • 4cs

we find for Ti = 20keV DT a ρR ≥ 3 g/cm2 is required for f ≥ 1/3

τc ≅R

4cs

f ~ 1/3 ⇒ ρ R ≅ 3 g/cm2 ⇒ M =4 π3

ρ R3 =4 π3

ρ R( )ρ2

3

3

final

initial

initial

final3final final

3initial initial

3

43

4

=⇒==

RRRRM

ρρρπρπ

rarefaction propagates into and decompresses the assembled mass at the sound speed cs

ρR

The burn fraction f is determined by the “areal density” ρR

For laboratory exper iments and a reasonable fuel mass a high fuel compression (~ factor of 1000) is required

Lawson Cr iter ion Efusion= n2/4 <vσ> WDTτ =3nkT = Ethermal nτc > 12kT/(<vσ> WDT) > 1014s/cm3

at NIF nτc ITF ≈ dsf2 Y ≈ ρR3 nτc = ρR/4csmi with ρR = 3g/cm2 nτ=2 1015s/cm3

integration from t=0 to t=τc , 1/n-1/n0= ½ <vσ>τc

Density determines total energy in fuel, for ρ = 0.21g/cm3, M =2.6 103 g Yield=2.8 1014 J

ρ = 400g/cm3, M =7 10-4 g Yield=40.7 108 J

Spher ical compression (R3):

7

Ignition and Nuclear Science Experiments BOTH require excellent diagnostics (Laser, Hohlraum and Capsule Implosion)

Full ApertureBackscatter (FABS) HR energetics

(DIM)

Diagnostic Instrument Manipulator (DIM)

X-ray imager Streaked detector (HSXD) synchronization + 20ps

Shock velocity measurements

(VISAR) Static x-rayImager(SXI) pointing

Hard x-ray spectrometer

(FFLEX) Bremstrahlung/Preheat

Near Backscatter Imager (NBI) SBS/SRS

Soft x-ray temperature

(DANTE)

HR temperature

Diagnostic Alignment System

nTOF(3.9m, 4.5m,

20m)

MRS

NAD

RAGS

GRHNI

WRF

I will present a brief description of most of these detectors

Hot Spot

“Cold” Shell

Yn,

‹ρRHS›, ‹ρRTot›,

Ti

tBurn,

mix

8

Radiochemistry: Looking for reaction products on nuclides loaded pre-shot to get information about the capsule at maximum compression

124Xe (ρR) 127I (mix)

Step 1: Isotopes loaded in ablator

• Neutron flux detection Longest range – probes remaining shell.mA + n → m-1A + 2n (124Xe + n → 123Xe + 2n)

Eth = 8.7 MeV 1.4 barn (14.5 MeV)mA + n → m+1A + γ (124Xe + n → 125Xe + γ )

low Eth 0.01 barn (1 MeV) 0.002 barn (5 MeV)

• Deuteron flux detection Intermediate range – probes inner shell.mA + d → mB + 2n (127I + d → 127Xe + 2n), 79Br(d,2n)79Kr

Eth = 4.2 MeV 0.4 barn (10 MeV)

• α-particle flux detection Shortest range – probes hot spot region.mA + α → m+3B + n (18O + α → 21Ne + n)

Eth = 1.8 MeV 0.2 barn (3.5 MeV)

Step 2: Reaction products made in Shot

Step 3: Reaction Products collected and counted

Ablator (Be or CH)

(n,x) reactions tell about areal densityCharged-par ticle reactions tell about energy loss and ablator-fuel mix

9

0.01

0.10

1.00

10.00

0.50 5.50 10.50 15.50 20.50

124Xe Cross Sections

124Xe+n 125Xe + g

124Xe+n 123Xe + 2n

Energy Dependence of (n,x) cross Sections provides neutron downscattered fraction

0.006

0.007

0.008

0.009

0.010

0.011

0.012

0.013

0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.400.00

0.20

0.40

0.60

0.80

1.00

1.20

0 50 100 150 200 250 300

Cro

ss S

ectio

n (b

arns

)

Energy (MeV)

Fuel ρr (gm/cm2)

125/

123

Rat

io

125Xe/123Xe Product RatioCorrelates with Fuel ρr

Hot Spot Mix (ng)

Nor

mal

ized

Abu

ndan

ce

Hot Spot Xe 127 MixSignature-Fill Tube

Production of Xe127 from (d,I127) isdirectly cor related with the amountof mater ial in the capsule hot spot.

Downscattered neutrons “Prim

ary”

neu

trons

D(3He,α)p

H.S.

127I mixed in here give biggest signal

127I(p,n)127Xe

Radiochemical Analysis of Gaseous Samples (RAGS)

Each noble gas would be collected in a separate cryogenic station

T

T

T

NIFchamber(600m3)

Turbos

HeliumGas Puff System

Xenon Cryogenic Fractionation & Detector System

Gas Pre-cleaner System

RGA

CryoCollector

Germanium detectorCryo Trap

MassSpectrometer

He flush

N flush RGA

NIF Target

Chamber

RGA

CryoPre-filter

Getter

Getter

Getter

TPS

Removable Trap

• System cryos are closed before shot

• Gas is removed after shot through system turbos

• Rise of chamber pressure from cryo has been measured (evaluation needed)

• Vibration from cryo closure has been measured (non-issue)

Removes everything but noble gases (nitrogen, oxygen, water, etc.)

Dawn Shaughnessy

4 Cryo-Pumps

RAGS prototype calibration at LBNL

NIF-0610-19423s2.ppt 11Fortner—Presentation to Dr. Steven Koonin, July 7th, 2010

1000000

10000000

1E+08

1E+09

1E+10

1E+11

1E+12

1E+13

1E+14

1E+15

1E+16

1E+17

1E+18

0.00 5.00 10.00 15.00 20.00 25.00 30.00

Neutron Energy (MeV)

C1 (HTD)C2 (HTD)C3 (DT)C4 (HTD)C5 (HT)

115In(n,n’) ⇒ 115mIn (t1/2=4.5 h) 360keV93Nb(n,2n) ⇒ 92mNb (t1/2=10 d) 511keV90Zr(n,2n) ⇒ 91Zr (t1/2=3.3 d) 900keV12C(n,2n) ⇒ 13C (t1/2=20 m) 511keV63Cu(n,2n) ⇒ 62Cu (t1/2=9.8m) 511keV

1-10 MeV (T-T spectrum)

10-13 MeV (Downscattered)

13-15 MeV (Primaries)

15-30 MeV (Tertiaries)

Darren Bleuel

In-115(n,n')In-115mNb-93(n,2n)Nb-93mZr-90(n,2n)Zr-89C-12(n,2n)C-11

Neutron Activation Diagnostic (NAD) – Gives Yield and ρR anisotropy

NToF OMEGA calibrations corroborated against Indium neutron activation for DD Shots

Preliminary Indium activation yields agree with NToF

13NIF-1209-17998.ppt Kilkenny—NIC Review, December 9–11, 2009

Accuracies ofcross sectionsand calibrationsdetermineneutron yield measurement accuracy to better then 10% 20090905 shot

(rescaled 64,209

(0,0 WRF-mount)

Issues:IsotropyDefinition (En)

0 1 1.5 20.5

2

0

1

1.5

0.5

nTOF D2 Yield (n) x 1010

14

Neutron Time of Flight Diagnostic (nToF) Measures Y, Tion and ρR

Requirements

Jac Caggianno

DT

Downscatter TT

1012

1013

1014

1015

81012

14

dn/d

E

E(MeV)

Neutron spectrum

Goal: ITF ≈ dsf2 Y∆ITF ≈ 20%

Issue: nToF Scintillator must be fast enough to see 10-12 MeV neutrons after a HUGE 14 MeV peak

At NIF we need to measure neutron spectra to an accuracy ~ 10 %

1012

1013

1014

550450400350

dn/d

t

t(ns)

Neutron arrival rate

500

Dynamic Range ≈ 100

1015

Measurements of down-scattered fraction with nTOF requiresa detector which recovers quickly from 14 MeV neutrons - Custom new scintillator fabricated for NIF by LLNS -

Fortner—Presentation to Dr. Steven Koonin, July 7th, 2010 15NIF-0610-19423s2.ppt

New scintillators for dsf neutron imaging is in progressSimilar scintillators are tested (calibrated) with neutron beams and

sources (e. g. AmBe)

Fabricated sample

3”

≈ 3 orders of magnitude in 30ns

~3.75"

~2"

The wedged range filter is a small assembly that is to be piggy-backed onto another diagnostic cart in a DIM

Wedge Range Filter (WRF) and Magnetic Recoil Spectrometer (MRS)

ρRMeasurementFrom Proton spectrum (WRF)AndNeutron spectrum (MRS)(down scattered)

Johann Frenje (MIT)

WRF sees protonsFrom target and

in situ foil

MRS sees p or dfrom external foil

Goal: An active readout system

Target

TargetAperture

Imageprocessing

NIFInterface

DAQ

Alignmentsystem

Partial tonon-reflective coating

CCDImager

CCDImager

Opticalgate/intensifiers

Aperture; 3 alignment/mini-penumbra, 18 triangular, 18 um res. pinholes 4 alignment pinholes.

13nsPulser

Pulser

2:1reducer

75 mm MCPII

40 to 75 mm MCPII

Custom lens

Scintillator BCF-99-55160 mm square250 um fibers, 5cm thk.

CCD cameras36.8 mm x 36.8 mm. 9 um pixel size4k by 4k

Coherent fiber bundle36.8 mm x 36.8 mm.10 um fibers

Neutron ImagingDavid Fittinghoff

Neutron imaging on NIF will measure hot spot size and ρRshell from down-scatter imaging

• Two gated neutron images at distance detects primary neutrons from hot spot and down-scatter neutrons from cold shell

• Shape accuracy ~ 2%

nDT

nds

nds

n imaging on NIF is being implemented to work for igniting plasmas

• Use the primary image as a source and match down-scattered image to derive density distribution in the dense fuel shell. (Algorithm under development)

14 MeV Down-scattered Cold shell

T or D

18NIF-1209-17998.ppt Kilkenny—NIC Review, December 9–11, 2009

Mach Zehnder enclosure

The GCD will enable yield measurement complementary to nTOF and NAD

GRH BT, Yield γBang-time (BT) +10%γ energy/intensityYield

1 of 4 “Quad” Channels

γ converted into Cherenkov photons detected in PMT At n-yield of 1013 we detect ≈ 100 γch

[(γCompton 1(MeV)e/γ (1e-3; Al)170γch/(MeV)e 25(PMT)e(gain 10e6)]1e17x50Ω V]

(LANL led collaboration: Hans Hermann, Wolfgang Stoeffl)

AU-Ringn

Gamma Reaction History (GRH) diagnostic based on conversion of fusion γ-ray to Cherenkov photons – Measure “Bang time”, Y, Burn ∆τburn , ρR

GRH will use high band width optical readouts

First NIF GRH data from exploding pusher (low ρR)

20

DT-Fusion γ-ray

∆tGRH≈300 ps due to cable(not Mach-Zehnders)Goal: ∆tGRH<100 ps

Fortner—Presentation to Dr. Steven Koonin, July 7th, 2010 21NIF-0610-19423s2.ppt

TCC

TopShieldedStreak

Cameras

ScopesW

shields

Late 2011: GRH-15m(Streak & PMT)

Now: GRH-6m(PMT)

13°26°

NIF ChamberTwo-stage GRH implementation for improved dynamic range and temporal resolution

Absolute calibrations performed at the High Intensity Gamma Ray Source (HIGS)

12C <ρR> (indicative of ablator mass remaining) can be inferred from 4.44 MeV

γ-ray measurement

Calculated γ-ray Spectrum

γ-ray energy (MeV)

4.4 MeV 12C(n,n’) from capsule

Or 9Be (α, η)

16.7 MeV from D+T(BR≈1e-4)

19.8 MeV from H+T

1e5

1e6

1e7

1e8

1e40 5 10 15 20

γ-ra

y flu

ence

(p

artic

les/

keV

)

TransitionRadiation

GRH Response

(Assumes 0.15 g Au ring)

≈5

Calculated γ-ray yield from neutron capture on the Au in the hohlraum as a function of time. The lower g-yield is due in large part to the lower (total 146J) yield. The t-error bar arises from the convolution of the burn time and the GRH detector temporal response.

GRH might also allow measurement of ρRcold fuel from capture of En< 1 MeV on Au hohlraum

This might also be used to obtain neutron flux for astrophysical

capture cross section measurements

From C. Cerjan

Neutron spectrum from a 251 J rRmac=1.2 g/cm2 HT(+0.5%D) capsule with inelastic scattering on hydrogen isotopes turned off (green) and on (red).

nToF

with D(n,n’)D, T(n,n’)Tw/o D(n,n’)D, T(n,n’)T

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High Neutron Flux≈1031-35 cm-2 s-1

(fluence=1021-24cm-2)

Hot/DensekbT=1-20 keV ρ≈10-1000 g/cm3

(Natom=1023-26cm-3)High γ-Fluxϕγ=1031-35 cm-2s-1

High e- Flux1036 e/cm2•s-1

(fluence=1025 cm-2 )

From a Nuclear Physics perspective the huge photon, electron and neutron fluxes at NIF make it unique

(n,x) onExcited Nuclear

States

(n,x) cross sections

Charged-particleCross sections

( γ fluence=1020-24cm-2)

Flux (n cm-2 s-1): LANSCE/WNR (≈1010); Reactor (1≈018); SNS (≈1015)

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Different fuel creates different neutron spectra, including astrophysical (kT≈10 keV)

(Modeling cour tesy of C. Cer jan)

DD - 146 J

Neutron Energy (keV)

NIF (or stellar)

thermal

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The NIF environment is very similar to that found in star s where (n,γ) forms heavy elements (s-process)

The huge neutron flux in a NIF capsule enables

measurements of (n,γ) cross sections on radioactive nuclei

Zs-process

s-process path near Tm

169Tm 170Tm 172Tm

171Yb 172Yb 173Yb170Yb

171Tm

5.025 keV4.8 ns 3/2+

1/2+

171Tm

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Electron-mediates atomic-nuclear interactions in a NIF capsule cause thermal population of low-lying nuclear states

Photo-absorptionTime Reverse: γ-ray decay

NucleusHEDP

Photons

Electron-mediated interactions are most important at T≈keV

e e

Atomic-nuclear (electron) interactionsNEEC, NEET, IES*

Time Reverse: IC-decay

Atomelectrons electrons

Photons

N N* N N*

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Thermalization time scales for 169Tm R

ate

(s-1

)

109

107

105

103

101

10-1 100 101 102

Temperature (keV)

Compliments of G. Gosselin

5 ns

Photon-absorptiofree-boundbound-boundfree-free

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What γ-ray production rate does GRH see for a D-fuel capsule loaded with a (n,γ) “seed” nucleus

From X-rays: σρR-Tm≈10%

σρR-Au≈5% σAu≈2%

NγTm

NγAu =

εTmγ ρR( )TmσTm En( )φ En( )dEn∫

εAuγ ρR( )Auσ Au En( )φ En( )dEn∫

What we wantFrom hohlraumLate time signal

What we need

169Tm

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The main uncertainty in GRH’s ability to “tag” (n,γ) is the production of statistical γ-rays from the CN

Modeled statistical γ-ray spectrum for 155Gd

We would like to measure Sγ for Eγ≥3 MeV at the 10% level

εstati = εGCD Eγ( )⊗ Si

γ Eγ( )Eth

Q

∫ dEγ

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Thulium in a NIF capsule will exper ience both (n,γ) and (n,2n) on ground and isomer ic states

167Tm 168Tm 169Tm 170Tm1/2+ stable

1- 3 keV

3+ 93 d1/2+ 9.25 d

7/2+ 180 keV

1- stable

7/2- 293 keV

7/2- 316 keV

7/2- 379 keV

171Tm1/2+ 1/9 y

3- 183 keV

7/2- 424 keV

“Normal” Thulium Reaction Network

• Only states with long t1/2 (>10 ns) can be populated by the “low” neutron flux – (n,n’), (n,2n), (n,γ)

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167Tm 168Tm 169Tm 170Tm1/2+ stable

1- 3 keV

3+ 93 d1/2+ 9.25 d

7/2+ 180 keV

1- stable

7/2- 293 keV

7/2- 316 keV

7/2- 379 keV

171Tm1/2+ 1/9 y

3- 183 keV

7/2- 424 keV

“Normal” Thulium Reaction Network

3/2+ 10 keV

? 80 keV4+ 64 keV? 47 keV2- 41 keV

? 17 keV 3/2+ 8.4 keV

11/2 368 keV

9/2- 430 keV

2- 39 keV

2- 220 keV

3/2- 5 keV

HEDP-populated states

• Short-lived states are “targets” in NIF capsule as well due to NEEC, NEET etc.

The case is more complicated when states populated via nuclear -plasma interactions are included

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Collaborators

L.A. Bernstein, C. Cerjan, R. Fortner, D.L. Bleuel, R.D. Hoffman, M.A. Stoyer, K. Moody,

D. Shaughnessy, P. Bedrossia, M. Wiedeking, R. Hatarik, D. H. G. Schneider, Lawrence Livermore National Laboratory, USA

A. Hayes, G. Grim, R. Dunford, Los Alamos National Laboratory

L. W. Phair, Lawrence Berkeley National Laboratory, USA

C. Brune, J. J. Carrol Ohio University, USA

U. Greife, Elliot Grafil, Colorado School of Mines, USA

Chr. Kozhuharov, C. Brandau, Th. Stoehlker, GSI-Helmholtzzentrum Darmstadt, Germany

A. Palffy, H. Keitel, Max Planck Institute of Nuclear Physics, Heidelberg, Germany

D. V. Meot, G. Gosslin, P. Morel, E. Bauge, CEA/DAM, Buyeres-le-Chatel, F rance

P. Walker, University of Sur rey University of Surrey, Guildford, U.K.

Other Institutions: SANDIA; University of Oslo, Norway; iThemba Labs, South Africa

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A collaboration is being established to explorenuclear physics @ NIF & statistical γ-ray spectra

Plus any of you that are interested