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Driving Gigabar Shocks With High-Power Lasers and Their Applications to Shock Ignition
W. TheobaldUniversity of RochesterLaboratory for Laser Energetics
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200
400
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1000
400
Distance (nm)
Pre
ssu
re (
Mb
)
500 600
Backsideof CH foil
Hot-electronshock
Hydrodynamicshock
Laser
Workshop on Scientific Opportunities in High-Energy-Density Plasma Physics
Washington DC25–27 August, 2008
FSCCollaborators
R. Betti,* C. Stoeckl*, K. S. Anderson,* T. R. Boehly, J. A. Delettrez, V. N. Goncharov, V. Yu. Glebov, R. L. McCrory, D. D. Meyerhofer,*
P. B. Radha, T. C. Sangster, W. Seka, A. A. Solodov*, B. Yaakobi, and C. D. Zhou*
Laboratory for Laser EnergeticsUniversity of Rochester
*also Fusion Science CenterUniversity of Rochester
J. A. Frenje, C. K. Li, and R. D. PetrassoMassachusetts Institute of Technology
Cambridge MA
L. J. PerkinsLawrence Livermore National Laboratory
Livermore, CA
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High-power laser facilities such as OMEGA EP and the NIF are ideal for the generation of gigabar shock waves
E17112
Summary
• Gbarshockwaveshaveimportantapplicationsforinertialconfinement fusion and for studying matter under extreme conditions.
• Shockignitionusesastrong,lateshockwavetoaugmentthecompression and bring the hot spot over the ignition threshold.
• OMEGAEPwillbeusedtostudyultrastrongshocksgeneratedby short-pulse, IR-beam-produced hot electrons.
• OMEGAEPwillgeneratestronghydrodynamicshockswithhigh-intensity UV laser beams.
• Integratedshock-ignitionexperimentsareplannedonOMEGAusing 40 + 20 beams.
Shock ignition uses a late shock to augment the compression of the central hot spot above the ignition threshold
E16323a
The ignitor shock wave significantly increases its strength as it propagates through the converging shell.
Time
Powerspike
Las
er p
ow
er
Spike shock wave
Returnshock
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20
15
10
Po
wer
(T
W)
5
0–1 0 1
Time (ns)
Laser pulse shape
2 3 4
0.25
0.20E
xper
imen
tal
GtR
H(g
/cm
2 )
Calculated GtRHn (g/cm2)
0.10
0.15
0.10 0.15 0.20 0.25
0.20Secondary D3He proton spectrum
0.15
0.10
0.05
0.00
No
rmal
yie
ld (
MeV
)
Energy (MeV)0 5 10 15 20
Yn = 2±0.2 × 109
Yn = 8±0.8 × 109
Detectorcutoff
1-Dsimulation
GtRH = 220±20 mg/cm2
CH
390 nm
40 nm8 – 25 atm
D2 gas
Low-implosion-velocity CH targets filled with D2 have produced total areal densities of ~200 mg/cm2
E16830a
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Hot electrons of moderate energies produced duringtheshockspikecanbebeneficialtoshockignition
TC7870
Hot e–withMaxwellianThot = 150 keV, Ehot = 25% of spike energy, treated using a multigroup diffusion model*
10.00
2
3
1
4
5
0
40
60
20
80
100
10.5 11.0
Time (ns)
Inte
nsi
ty (
1015
W/c
m2 )
tR
(m
g/c
m2 )
10.20
10
40
30
20
50
60
10.4 10.6
Shock-launching time (ns)
Gai
n
Without hot e– With hot e–
tR
tR range of 100 KeV e–
ILaser
Shock-ignition targetwith 350-kJ total energy
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*J. Detettrez and E. B. Goldman, LLE, Univ. of Rochester, Rochester, NY, LLE Report No. 36 (1976).
0
800
600
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Shockfront
Backsideof CH foil
Pre
ssu
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Mb
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Laser
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Shockfront
Backsideof CH foil
250 500Distance (nm)
Pre
ssu
re (
Mb
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0 200 400Distance (nm)
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Laser
Shock-driving100-ps IR beam
Plasma generatorUV beam
100-nm diam
Plasma generatorUV beam
600 nm
CH
VISARDoppler
interferometer
3000 nm
Divergent e-beam (26°)
OMEGA EP is an ideal facility to study ultrastrong shocks generated by IR-beam-produced hot electrons
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• Long-scale-lengthplasma(mm).
• ModerateIRintensityof3× 1017 W/cm2.
• OMEGAEPbeamwith2.5kJ, 10% CE into hot electrons.
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0
500
400
300
200
100
600 1 × 1016 W/cm2
Shockfront
Backsideof CH foil
Pre
ssu
re (
Mb
)
Laser
0
1200
900
600
300
1500
Shockfront
Backsideof CH foil
Pre
ssu
re (
Mb
)
0 200 400Distance (nm)
600
0 200 400Distance (nm)
600
Laser
600 nm
Three overlappedshock-driving1-ns UV beams
CH
VISARDoppler
interferometer
Plasma generatorUV beam
1 × 1017 W/cm2
3000 nm
Even stronger shocks can be generated hydrodynamically with high-intensity UV laser beams
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• Long-scale-lengthplasma(mm).
• Threebeamsareoverlappedwithspotsizes varying between 100 to 300 nm.
• Beamenergyofupto~2 kJ in 1 ns.
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A hydrodynamic simulation including fast-electron generation shows the formation of two strong shocks
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• Long-scale-lengthplasma(mm).
• ThreeoverlappingUV OMEGA EP beams, E = 7.5 kJ (1 ns), 1017 W/cm2.
• 10%CEintoGEH ~ 150 keV hot electrons.
3000
200
400
600
800
1000
400
Distance (nm)
Pre
ssu
re (
Mb
)
500 600
Backsideof CH foil
Hot-electronshock
Hydrodynamicshock
Laser
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The shock pressures are inferred from shock-velocity measurements with a VISAR system
E17116
23°
48°
Probe laser
1 2
f/3
VISAR’s
Temperature calibrated self-emissioncamera (SOP)
CH/SiO2
0 5
Time (ns) Time (ns)
–400
–200
0
200
Lat
eral
po
siti
on
(n
m)
0 52 4311 2 3 4
CH SiO2SiO2CH
Catch upCatch up
BreakoutBreakout
VISAR Self-emission
~v pstrong
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Integrated shock-ignition experiments will study the effect of fast electrons on the hydrodynamic performance of imploding shell targets
E17117
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Integrated shock-ignition experiments are planned on OMEGA using 40 + 20 beams.
Laser
Criticalsurface 1016 to 17 W/cm2
Laser
Hot e–
Hot e –
Laser
Laser
01012
1013
1014100
Are
al d
ensi
ty
150
200
250
50
0
1015
Drive
~100-keVstopping range
Fast-electrongeneration
1016
1 2Time (ns)
Las
er in
ten
sity
(W
/cm
2 )
3 4 5TargetTargetHot e–
• Sphericallysymmetricillumination.
• Moderate-energyhotelectrons(100 to 300 keV) are generated at the end of the implosion.
• Shellarealdensityishighenoughtostopthehot electrons.
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E17112
Summary/Conclusions
High-power laser facilities such as OMEGA EP and the NIF are ideal for the generation of gigabar shock waves
• Gbarshockwaveshaveimportantapplicationsforinertialconfinement fusion and for studying matter under extreme conditions.
• Shockignitionusesastrong,lateshockwavetoaugmentthecompression and bring the hot spot over the ignition threshold.
• OMEGAEPwillbeusedtostudyultrastrongshocksgeneratedby short-pulse, IR-beam-produced hot electrons.
• OMEGAEPwillgeneratestronghydrodynamicshockswithhigh-intensity UV laser beams.
• Integratedshock-ignitionexperimentsareplannedonOMEGAusing 40 + 20 beams.