1CEA-DAM Ile-de-France High-Gain Direct-Drive Shock Ignition for the Laser Megajoule:prospects and first results. B. Canaud CEA, DAM, DIF France 7th Workshop.

1CEA-DAM Ile-de-France

High-Gain Direct-Drive Shock Ignition for the Laser Megajoule:prospects and first results.

B. CanaudCEA, DAM, DIFFrance

7th WorkshopDirect Drive

and Fast IgnitionMay, 3-6, 2009

Prague,

FCI2Direct Drive @ 2 rings

Density at stagnation

50 100Radius (µm)

50

100


Collaborators

X. Ribeyre, M. Lafon, J.L. Feugeas, J. Breil, G. SchurtzCELIA, Bordeaux

M. Temporal, R. Ramis ETSIA, Madrid, Spain


Standard LMJ direct drive illumination differs from indirect one by a more isotropic beam layout on the target chamber.

a) Baseline LMJ Direct Drive b) LMJ Indirect Drive

33.2° (10 beams)

49° (10 beams)

59.5° (10 beams)

Z

DT

33.2° (10 beams)

78° (10 beams)

59.5° (10 beams)

Z

DT

ID

DD

33.2°

59.5 °49°

78°

102°

131°120.5°

146.8°

Quad

Each LMJ beamlet is limited by its power max: Pmax ≤ 2.5 TW.


A few years ago, we proposed a new direct drive configuration with indirect drive beam layout [*]…

b) LMJ Indirect Drivea) Baseline LMJ Direct Drive

33.2° (10 beams)

78° (10 beams)

59.5° (10 beams)DT

33.2° (10 beams)

49° (10 beams)

59.5° (10 beams)

Z

DT

… but with only 1.2 MJ of laser energy.

(*) Canaud B. et al, Plasmas Phys. Cont. Fusion, 49, B601 (2007).


49° (45%)59.5° (55%)

Zearly time

late time

large spot

narrowspot

Focal spot zooming increases laser-target coupling efficiency[**].

1 beam large, 3 narrows on each quad.

With zooming and 2 rings,Gain=32 with 1 MJ laser.

With zooming and 2 rings,Gain=32 with 1 MJ laser.

A new 2-rings baseline(*) high-gain Direct-Drive design has been proposed with focal spot zooming.

(*) Canaud B. et al, Nucl. Fus., 47, 1642 (2007)

1 µm CH

DTgas

DT iceWetted foam

165 µm134 µm

1341 µm

Adiabat = 3.5 V=4.105 m/s

FCI2Direct Drive @ 2 rings

Density at stagnation

50 100Radius (µm)

50

100

(**) Canaud B. et al, Nucl. Fus., 45, L43 (2005)


Laser energy (MJ)with 3D ray-tracing

The

rmon

ucle

ar g

ain

Adiabat = 3.5 V=4.105 m/s

1 µm CH1642 µmDT gasDT iceCH(DT)n203 µm164 µm

0.1

1

10

100

0.4 10.6 3

w/o Zoomingw/ Zooming

LMJ design with zooming

Without zooming, the target is marginally igniting.

LMJ design without zooming

: adiabatv : implosion velocity

E, M f 3

R,t f

P f 2

Homothetic target family curve


• Isobaric ignition concerns standard direct drive ignition.

Alternative exists to displace the energy threshold towards lower energies, keeping constant the implosion target parameters (,v).

Hot-spot DTfuel

radius

T

PisoIsobaric Ignition threshold

Ethresholdisobaric

3

v 7

: adiabatic parameterv : implosion velocity

10-1

100

101

102

0,01 0,1

ET

h(MJ)

Ec (MJ)

Burn of

Hot spot

Burn of

DT fuel

E,M f 3

R,t f

P f 2

(*) Betti R. et al, Phys.Rev. Lett., 98, 155001 (2007)

• Non-isobaric ignition reduces the energy threshold for ignition.

E thresholdnon isobaric

E thresholdisobaric

Hotspot

DTfuel

radius

T

Pnon iso

where

P non isobaric

P isobaric

3

Piso


• A low-isentrope compression is obtained by a usual pulse shape.

Non isobaric conditions can be achieved by launching a strong shock at the end of the implosion.

• An additional spike launches a strong shock in the target.

tspike

Pspike


Shock can be created by the 33°-ring of the LMJ(*).

33.2° (10 beams)

49° (10 beams)

59.5° (10 beams)

Z

DT }

(*) Ribeyre X. et al, Plasmas Phys. Cont. Fusion, 51, 015013 (2009).

2D CHIC simulations of bipolar shock ignition show a good sphericity of the ignitor shock.


0,001

0,01

0,1

1

10

100

1000

0,01 0,1

Et(

MJ)

Ec(MJ)

• The target is far below the ignition threshold.

Fast-ignitor (*) targets can be considered for Shock Ignition (+).

(*) Ribeyre X. et al, Plasmas Phys. Cont. Fusion, 50, 025007 (2008).

(+) Ribeyre X. et al, Plasmas Phys. Cont. Fusion, 51, 015013 (2009)

tspikeP sp

ike

(TW

)

100

200

50

10

20

30

40

10

P (TW)

t (ns)tspike

Pspike

200 ps

300 ps

200 ps

109.5 10.4

DTgas

DT ice@ 250 kg/m3210 µm 1040 µm

HiPER(*) baseline target

1D implosion data Absorbed energy 110 kJ Adiabat 1 Implosion velocity 290 km/s Density Max 600 g/cm3

Areal density max 1.5 g/cm2

0,001

0,01

0,1

1

10

100

1000

0,01 0,1

Et(

MJ)

Ec(MJ)

P=180 TWETh=20 MJ


With the spike and 2 rings, G1D=50 with 0.2

MJ absorbed laser.

With the spike and 2 rings, G1D=50 with 0.2

MJ absorbed laser.

Marginally igniting standard direct drive target can be triggered by shock ignition (SI).

1 µm CH

DTgas

DT iceWetted foam

120 µm100 µm

960 µm

BaselineDirect Drive

= 3.5 V=400 km/s

50

100

150

7

P (TW)

t (ns)tspike

Pspike

200 ps

300 ps

200 ps

1D implosion data Absorbed energy 200 kJ Density Max 500 g/cm3

Areal density max 1. g/cm2 With SI (@max) Pspike 190 TW Density Max 1700 g/cm3

Areal density max 1.27 g/cm2

Eth 11 MJ

0,01

0,1

1

10

100

0,01 0,1

Eth

erm

onuc

lear

(MJ)

E kinetic

(MJ)

With Shock ignition


Different targets from the FI-family should be considered for LMJ.100 KJ-absorbed 500 KJ-absorbed

=1v = 290 km/smax= 600 g/cm3

1D implosion data Absorbed energy 500 kJ r 2 g/cm2

Spike Laser Power max 110 TW Abs Intensity 2e15 W/cm2

Thermonuclear rho r 2.2 g/cm2

Energy Th. 133 MJ

850 KJ-absorbed

1D implosion data Absorbed energy 850 kJ r 2.24 g/cm2

Spike Laser Power 100 TW Abs Intensity 1e15 W/cm2


Energy Th. 260 MJ

2090 µm

DTgas

DT ice420 µm

1750 µm

DTgas

DT ice350 µm



Thermonuclear rho r 2 g/cm2

Energy Th. 44 MJ




Energy Th. 18 MJ

1040 µm

DTgas

DT ice210 µm

200 KJ-absorbed

1240 µm

DTgas

DT ice250 µm


The power in the spike is a key parameter for SI.

100 KJ-absorbed

=1v = 290 km/smax= 600 g/cm3

1040 µm

DTgas

DT ice210 µm

200 KJ-absorbed

1240 µm

DTgas

DT ice250 µm

Need between 200 and 300 TWfor ignitor pulses :The 33° rings will produce only 200 TW

We need to redefine a target design and to improve the laser-target coupling efficiency for the ignitor pulses.



Thermonuclear r 2 g/cm2

Energy Th. 44 MJ



Thermonuclear r 1.7 g/cm2

Energy Th. 18 MJ


Low energy for fuel assembly should allow to use only the 49° ring.

100 KJ-absorbed

=1v = 290 km/smax= 600 g/cm3



Thermonuclear r 2 g/cm2

Energy Th. 44 MJ



Thermonuclear r 1.7 g/cm2

Energy Th. 18 MJ

1040 µm

DTgas

DT ice210 µm

200 KJ-absorbed

1240 µm

DTgas

DT ice250 µm

b) LMJ Indirect Drive

33.2°

49°59.5°

Z

DT

We need more than 200 kJ to assemble the target: the 49° rings should be a good candidate.

We need to improve the irradiation uniformity.


High gain direct drive Shock ignition on LMJ requires to address several physical key issues.

Summary

• Standard direct drive fuel assembly is achievable with a part of X drive beams (rings @ 49° et 59°5).• Using the ring @ 49° needs well characterize and to improve (if necessary) the irradiation uniformity (PDD, Green House Target, …)• Shock ignition with the last beams (rings @ 33°) should be possible but we may need to redefine a target with lower power ignitor.• Extremely high gains could be achieved on LMJ :

E1D absorbed~ 0.2 MJ, Eth ~ 40 MJ

Restrictions• Parametric instabilities driven by the shock ignitor could be problematic.• Hydrodynamic stability of the capsule must be addressed• Unknown Physics (eos, heat conductivity, kinetic effects,…) could be limiting.• …

• 1D design must be revisited (wetted foam, reduced IFAR, …).• Fully 2D calculations (with ray-tracing 3D) have to be done for LMJ.

In addition, to be done …

1CEA-DAM Ile-de-France High-Gain Direct-Drive Shock Ignition for the Laser Megajoule:prospects and first results. B. Canaud CEA, DAM, DIF France 7th Workshop.

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