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
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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).