Diagnosing Areal Density using the Magnetic Recoil Diagnosing Areal Density using the Magnetic Recoil Spectrometer (MRS) at OMEGA and the NIF Spectrometer (MRS) at OMEGA and the NIF

The MRS on OMEGA

C i DT Y ≈ 5 8×1012

1.E+03

1.E+04

eV

Cryogenic DT Yn ≈ 5.8×1012

136 mg/cm2

1.E+01

1.E+02

Cou

nts

/ M

Fit

1.E+00

1.E 01

5 10 15Deuteron Energy [MeV]

C

MRS Data

Deuteron Energy [MeV]

Omega Laser User Group Workshop

Photo: Eugene Kowaluk

1

Rochester, New YorkApril 29th – May 1st, 2009

AbstractAbstract

A Magnetic Recoil Spectrometer (MRS) has been installed andactivated on OMEGA for measurements of down-scattered andprimary neutrons, from which areal density, ion temperature,

d i ld f i DT i l i b i f d Tand yield of cryogenic DT implosions can be inferred. Tocorrectly interpret these measurements, the MRS responsefunction was characterized using the Monte Carlo codeGEANT4 and diagnostic activation experiments. The results ofth MRS h t i ti ll t f ththe MRS characterization as well as measurements of theabsolute neutron spectrum at OMEGA will be presented.

This work was supported in part by the U.S. Department ofThis work was supported in part by the U.S. Department ofEnergy (Grant No. DE-FG03-03SF22691), LLE (subcontractGrant No. 412160-001G), LLNL (subcontract Grant No.B504974).

2

CollaboratorsCollaborators

J. A. Frenje, F. H. Séguin, C. K. Li, M. Manuel, N. Sinenian, and R. D. PetrassoPlasma Science and Fusion Center Massachusetts Institute of TechnologyPlasma Science and Fusion Center, Massachusetts Institute of Technology

V. Yu. Glebov, D. Meyerhofer, T. C. Sangster, P. B. Radha, S. Roberts, M. Burke, and J Ulreichand J. Ulreich

Laboratory for Laser Energetics, University of Rochester

S. W. Haan, S. P. Hatchett, C. J. Cerjan, and M.J. Moran, , j ,Lawrence Livermore National Laboratory

K. Fletcher, Joseph Katz, and Kevin O’ConnellDepartment of Physics and Astronomy, SUNY Geneseo

3

Motivation for the MRS at OMEGAMotivation for the MRS at OMEGA

• Measure the absolute neutron spectrum of cryogenic DTimplosions

• Infer ρR from the down-scattered neutron spectrum

• Measure absolute neutron yield

• Determine fuel ion temperature from Doppler broadenedprimary neutron spectrum and characterize non-thermalfeatures if present

4

features, if present

The neutron spectrum contains a wealth of information The neutron spectrum contains a wealth of information including the including the ρρR, TR, Tii, T, Tee, and Y, and Ynn

From down-scattered (Yds):

• ρR

Down-scatteredPrimaries

SecondariesTertiaries RYds ρ∝• ρR

From primaries (Y1n):

Y

1019Tertiaries R

Y nρ∝

1

• Y1n

• Ti

F S d i (Y )

1015

d /

MeV

Ignited (NIF)

2i ΔE T ∝

From Secondaries (Y2n):

• Te

1011

Yiel

d

P6-fizzle (NIF)

OMEGA

3

1

2e

n

n TYY

∝

NIFFrom Tertiaries (Y3n):

• ρR

1070 10 20 30

MeV

OMEGA

RYY

n

n ρ∝1

3

NIF

5

Y n1

The principle of the Magnetic Recoil Spectrometer (MRS)The principle of the Magnetic Recoil Spectrometer (MRS)

TargetCH-foil or CD-foil MagnetEntrance

Exit

10 (Ω)

CR 39215 cm (Ω)

10 cm (Ω)26 cm (NIF)

CR-39

Detector housing

( )570 cm (NIF) Magnet housing

6-28 MeV (p)3-14 MeV (d)

6J. A. Frenje et al., Rev. Sci Instrum 79, 10E502 (2008).

MRS detection efficiency and energy resolutionMRS detection efficiency and energy resolution

∫Ω

Ω⋅⋅Ω

="" r

in

MRS ddtn σε

• The detection efficiency is defined as:

∫ ΩΩ

⋅⋅=4 lab

iMRS dd

tnπ

εAbsolute yields are measured

since Ωn, ni, t, , and Ωr are knowndΩdσ

Ωn “Ωr”Ωn “Ωr”Ωn “Ωr”Ωn “Ωr”

• Resolution (ΔEI) is defined as:

222 ΔEΔEΔEΔE

ΔEf = Energy loss in foil ∝ foil thicknessΔE Ki ti b d i f il d t i

2m

2k

2fI ΔEΔEΔEΔE ++≈

7

ΔEk = Kinematic energy broadening ∝ foil and aperture sizesΔEm = Optical energy broadening ∝ magnet performance

The 1The 1stst phase of the MRS installation was completed in phase of the MRS installation was completed in September 2007September 2007

Top view Vie from behind

Magnet

Top view View from behindMagnethousing Magnet

housing

Detector

8

Pictures by Eugene Kowaluk

Detectorhousing

Detectorhousing

During the 2During the 2ndnd installation phase, polyethylene neutron installation phase, polyethylene neutron shielding was installed around the MRS in Spring 2008shielding was installed around the MRS in Spring 2008

~2000 lbs of polyethylene shielding installed around the MRS

2020cm

9

Pictures by Eugene Kowaluk

The Monte Carlo code Geant4 is being used to model The Monte Carlo code Geant4 is being used to model the full MRS detector responsethe full MRS detector response

10-2

100

102

10-10

10-5

/MeV

1/M

eV

Emitted neutron spectrum

Measured deuteron spectrum

0 5 10 1510-4

10

5 10 15

1/

Recoil Deuteron Energy [MeV]Neutron Energy [MeV]

1

MRS response function

Point source Magnetic field

CR-39 detectors6 MeV

14 28

CD Foil

MRS response function

20 0.8B (T)

Magnetic field

CD Foil

0

5

10

15

0.4

0.6

Y (c

m)

10

210 220 230 240 250 260-5

0

0

0.2

Distance from TCC (cm)

Areal density (Areal density (ρρR) can also be inferred from R) can also be inferred from knockknock--on protons (KOon protons (KO--p), and knockp), and knock--on deuterons (KOon deuterons (KO--d)d)

4 (×10-4)

n) CH

n'

10-3

10-1

101

MeV

· n)

n'

n2KO-p

ield

/ (M

eV ·

n'

DTCH

KO-p

10-7

10-5

10

0 10 20

Yiel

d/(M

MeV

0 10 200

MeV

Yi n

KO-dKO-d

1 (×10-4)

· n)

MeVKO-d

1 (×10-4)

· n)

KO-d

0

KO-d

Yiel

d / (

MeV

S ρR x Yn

B Y∝

0

KO-d

Yiel

d / (

MeV

11

0 10 200

MeV

YB Yn∝ 0 10 200

MeV

Y

KO-p and KO-d measurements are made with magnet based charged particle spectrometers like CPS or the MRS without a foil

TargetNo foil MRS without a foilThe MRS on OMEG

CPS2

CPS1 No foil

MRS

CPS1

225 cm

MRS

6-28 MeV (p)3-14 MeV (d)

Target

50 keV

CPS 1 and 2

3 14 MeV (d)50 keV

200 keV2cm

CR-39

12

600 keV

1 MeV 3 MeV

30 MeV

10 MeV

CR 39

The OMEGA MRS obtained KOThe OMEGA MRS obtained KO--d** data on a cryogenic DT d** data on a cryogenic DT implosion after shielding was installedimplosion after shielding was installed

13**J. A. Frenje et al., LLE Progress Report for DOE (Jan 2008).

The Coincidence Counting Technique (CCT) is used to reduce the The Coincidence Counting Technique (CCT) is used to reduce the background for DSbackground for DS--n measurementsn measurements

CR39

Random coincidencesSignal

Incident Neutron

10

15

20

40 Misaligned 200μmAligned

Countμm

]

Front-piece Back-piece

Incident proton/ deuteron Rl1

Rl20

5

-40

-20

0

Rc Rc

ts / Pixel

Δy

[μ

Intrinsic noise

-40 -20 0 20 400

-40 -20 0 20 40Δx = xfront - xback [μm] Δx [μm]

Triple-track coincidence

InterfaceSurface after etching

por double coincidence

14Applying the CCT can enhance the S/B by orders of

magnitude in low yield measurements

TT fusion neutrons overlap the lower part of the downTT fusion neutrons overlap the lower part of the down--scattered neutron spectrumscattered neutron spectrum

1.E+01

V]

Cryo DT Neutron spectrum for ρR~150mg/cm2 Ti~2.5keV

1.E-01

1.E+00

rum

[1/M

eV PrimaryTTFuelTotalShell

Primary TT Neutrons

- T + T → α + n + n

1 E 03

1.E-02

ron

Spec

tr

- T + T → α + 2 n

- T + T → *He5 + n

1.E-04

1.E-03

0 5 10 15

Neu

tr- T + T → He + nTT neutrons

Energy [MeV]

For a ~150mg/cm2 cryogenic DT neutron spectrum the TT

15*This is for a low resolution measurement of the down-scattered neutron spectrum

contribution in the MRS down-scattered measurements is ~12%*

The TT contribution to the neutron spectrum is calculated The TT contribution to the neutron spectrum is calculated using the reactivity ratio for a given Tusing the reactivity ratio for a given Tionion

1.E-14 0.030DTTT

1.E-17

1.E-16

1.E-15m

3 /s 0.020

0.025

50/5

0DT

TT/DT Yield Ratio

1 E 20

1.E-19

1.E-18

< σv>

cm

0 005

0.010

0.015

Y TT/Y

DT

for

1.E-21

1.E-20

0 5 10 15 20

T [KeV]

0.000

0.005

Tion [KeV]

TTTDTTT

vnYY ><≈

σ21/

16

DTDDTTT vn ><σ2

This assumes approximately equal DT and TT spatial and temporal burn profiles

The first DSThe first DS--n measurements were performed using warm CH n measurements were performed using warm CH DT implosion in April and May 2008DT implosion in April and May 2008

1.E+00

1.E+01

MeV

] PrimaryTTFuel1.E+05

1.E+06

V Fit

Shots 51294-51298 – ρRshell=45mg/cm2 ± 20 mg/cm2

Best fit neutron spectrum

1.E-03

1.E-02

1.E-01

n Sp

ectr

um [1

/M

FuelShellTotal

1.E+02

1.E+03

1.E+04

Cou

nts

/ MeV MRS Data

1.E-05

1.E-04

0 5 10 15

Energy [MeV]

Neu

tron

1.E+01

1.E 02

5 7 9 11 13 15Deuteron Energy [MeV]

1.E+00

1.E+01

1/M

eV] Primary

TTFuelShell

Energy [MeV]

1.E+05

1.E+06

eV

FitMRS Data

Shots 51316-51320 – ρRshell=65 ± 23 mg/cm2

Best fit neutron spectrum

1.E-03

1.E-02

1.E-01

ron

Spec

trum

[1

ShellTotal

1.E+02

1.E+03

1.E+04

Cou

nts

/ Me

171.E-05

1.E-04

0 5 10 15

Energy [MeV]

Neu

tr

1.E+015 7 9 11 13 15

Deuteron Energy [MeV]

An areal density of 136 An areal density of 136 ±± 23 mg/cm23 mg/cm2 2 was inferred from the first was inferred from the first downdown--scattered neutron measurement of a cryogenic DT implosionscattered neutron measurement of a cryogenic DT implosion

1.E+01

V]

PrimaryTT

53066: CryoDT(68)CD[10], Yn ≈ 5.8×1012Best fit neutron spectrum

1.E+04

1.E-01

1.E+00

ctru

m [1

/MeV

TTFuelTotalShell

1.E+02

1.E+03

ts /

MeV 136 mg/cm2

1.E-03

1.E-02

eutr

on S

pec

1 E+00

1.E+01Cou

nt

FitMRS Data

1.E-040 5 10 15

Energy [MeV]

Ne1.E+00

5 10 15Deuteron Energy [MeV]

18

The first MRS measurements at OMEGA show the The first MRS measurements at OMEGA show the diagnostic is performing welldiagnostic is performing well

Summary

The MRS was installed on OMEGA in summer 2007 and the neutron shielding installed in spring 2008g p g

The MRS response function is being characterized using Geant4 and implosions producing DHe3 protons and primary DT neutronsneutrons

The CCT was developed to dramatically reduce the background (~10-100 times) for down-scattered neutron measurements for ( )the OMEGA MRS

The first down-scattered neutron measurements of non-cryogenic and cryogenic DT implosions have been successfullycryogenic and cryogenic DT implosions have been successfully performed

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Some Important ReferencesSome Important References

S. Agostinelli, et al., “Geant4 – A Simulation Toolkit.” Nucl. Instrum. Meth. Phys. Res. A 506, 250 (2003).

H. Brysk, “Fusion Neutron Energies and Spectra.” Plasma Physics. 15, 611 (1973).

J. A. Frenje, et al., "First measurements of the absolute neutron spectrum using the Magnetic Recoil Spectrometer (MRS) at OMEGA (invited)." Rev. Sci Instrum 79, 10E502 (2008).

J. A. Frenje, et al., NIF Diagnostic White Paper (2009).

V. Yu. Glebov, et al., “Development of nuclear diagnostics for the National Ignition Facility (invited).” Rev. Sci Instrum. 77, 10E715 (2006).

V. Yu. Glebov., “T–T Fusion Neutron Spectrum Measured in Inertial Confinement Fusion Experiment.” Bul. American Physical Society (2006).

J. Källne, et al., “Observation of the Alpha Particle “Knock-on” Neutron Emission from Magnetically Confined DT Fusion Plasmas.” Phys. Rev. Let. 85, 1246 (2000).

T. C. Sangster, et al., “Cryogenic DT and D2 Targets for Inertial Confinement Fusion.” Phys. Plasmas 14, 058101 (2007)058101 (2007).

F. H. Seguin, et al., “Spectrometry of Charged Particles form Inertial Confinement Fusion Plasmas.” Rev. Sci Instrum. 74, 975 (2003).

S Skupsky et al “Measuring Fuel ρR for Inertial Fusion Experiments Using Neutron Elastic Scattering

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S. Skupsky, et al., Measuring Fuel ρR for Inertial Fusion Experiments Using Neutron Elastic Scattering Reactions.” J. Appl. Phys. 52, 4 (1981).