1. 1. Fast ignition by hydrodynamic flow
S.Yu.Gus’kov. LPI RAS
Fast Ignition by Detonating Hydrodynamic Flow S.Yu. Gus’kov*, M. Murakami** *P.N. Lebedev Physical Institute of Russian Academy of Sciences, Moscow, Russia **Institute of Laser Engineering. Osaka University. Japan 7-th Direct Drive and Fast Ignition Workshop. May 3-6, Prague
Contents:
1. Fast ignition by hydrodynamic flow
2. Fast ignition by detonating hydrodynamic flow - “target from target” ignition
3. Conclusion: Practicability of fast ignition at the impactor velocity of
km/s

2. Fast ignition by hydrodynamic flow
S.Yu.Gus’kov. LPI RAS
Fast ignition by hydrodynamic flow

3. Fast Ignition Drivers Compression Ignition Igniting Drivers:
S.Yu.Gus’kov. LPI RAS
Fast Ignition Drivers
Compression
 =( ) g/cm3
R = (3 - 4) g/cm2
Ignition
T=10 keV
Rign = 0. 4 g/cm2
Igniting Drivers:
Fast particles from laser-produced plasma
electrons (Ee ~ MeV)
light ions (Ei ~ MeV/nuclon)
Laser : IL > 1019 W/cm2, L< ps.
Experiments: CD-target + cone
RAL (UK), ILE (Japan)
Neutron yield: 105  106
Hydrodynamic pulse
I u3 , u ~ 1000 km/s
Laser: IL  1015 W/cm2, L  1 ns
ILE (Japan)
Igniting Driver
Energy: Eign = (10-15)/1002 kJ Eign = (10-30) kJ
Beam radius: Rign= Rign /   Rign  10-30m Pulse duration: ign = Rign/108  ign  10 ps
Intensity: Iign  ( ) W/cm2

4. General Requirements for Impact Ignition
S.Yu.Gus’kov. LPI RAS
General Requirements for Impact Ignition
t= g/cm3 ! Tign=10keV. I  imu3
Iign  t (CDTTign)3/2, ign  0.5(im /t)1/2
= g/cm3
R=3-4 g/cm2
u  1.5(t /im)1/2 (CDTTign)1/2
t = im  u = 1500 km/s,
t = 10im  u > 4000 km/s,
Ignition of the Target
R=3-4 g/cm2 =
g/cm3
I im (CDTTign)3/2
u  (CDTTign)1/2
u ~1000 km/s
Ignition of the Impactor
Theoretical limit of low-entropy laser-driven acceleration of a foil: 1700 km/s

5. Hydrodynamic fast ignition
S.Yu.Gus’kov. LPI RAS
Hydrodynamic fast ignition
Impact along a cone
 ~ 1 g/cm3  V ~ 1000 km/s,
M.Murakami, H. Nagatomo
Nucl. Inst. & Meth. Phys. Res. A544, 67, 2005
Compression in a conical target.
Detonating flow.
 ~ ( ) g/cm3  V ~ ( ) km/s,
S. Gus’kov, M.Murakami XXX ECLIM, 2008
Profiling
laser pulse
Simple
1000 km/s 300 km/
ILE (Osaka University, Japan) experiments on impact ignition, EL~ (1-3) kJ, 3:
Acceleration of the foil up to record velocity: 600–700 km/s.
Impact neutron generation: (1 -2) 106 DD-neutrons/shot.

6.  >> ILE planar impact ignition experiments N: 106 N: 8.3105
S.Yu.Gus’kov. LPI RAS
ILE planar impact ignition experiments
Watari T, Sakaiya T, Azachi H et al Neutron generation from impact fast ignition
Proc. 5-th IFSA conference (Kobe, Japan, September 2007)
1. CD-foil - CD-target
impact
3. CD-foil - CH-target
impact
2. CD-foil - CD-target
impact
impactor
Main fuel
laser
600 mm
Be plane
(weight)
Be frame
CD foils 20 mmt
Laser energy :1.9 kJ
Spot size : 300 mm f
laser
600 mm
CH plane
300 mmt
Be frame
CD foils 20 mmt
Laser energy :1.3 kJ
Spot size : 300 mm f
laser
Be frame
CD foil 20 mmt
Laser energy :1.9 kJ
Spot size : 300 mm f
N: 106 
N: 8.3105
>>
N: 1.3105
1) impact nature of neutron generation and
2) neutron generation in impact-produced plasma of impactor

7. ILE spherical impact ignition experiments
S.Yu.Gus’kov. LPI RAS
ILE spherical impact ignition experiments
Watari T, Sakaiya T, Azachi H et al. Neutron generation from impact fast ignition.
Proc. 5-th IFSA conference (Kobe, Japan, September 2007
P M T
Plastic scintillator
18 cm f × 2.5 cm
47 cm
311 cm
190 cm
178 cm
Pb 10 cm
25°
80°
52°
168°
10 cm f × 5 cm
target
421 detectors
MANDALA
1344 cm
Target chamber
1. Nmax= 2106
2. Ti=1.59 keV
3. Nmax corresponds to coincidence of the moments
of maximal compression and impact

8. < > u u r r Impactor’s state before collision.
S.Yu.Gus’kov. LPI RAS
Impactor’s state before collision.
Impactor’s density and velocity distributions along the central axis.
L = 600 mm, t = 1.8 ns
L = 1000 mm, t = 2 ns u u r r
<
u  600 km/s
u  800 km/s
>
r  0.2 g / cc
r  0.08 g /cc

9. << > > Impact-produced plasma of impactor and target r r
S.Yu.Gus’kov. LPI RAS
Impact-produced plasma of impactor and target
Density, ion and electron temperature distributions along the central axis
<<
L = 600 mm, t = 1.8 ns
N  106
N 
L = 1000 mm, t = 2 ns
Target
Impactor
Target
Impactor Ti
> Te Ti
> Te r r
Ti=Te
Ti=Te
Impactor
Ti  2.2 keV, Te  1.2 keV r  0.18 g/cc
Impactor
Ti  6.2 keV, Te 1.8 keV
r  0.12 g/cc
Target
Ti  80 eV, r  3.8 g/cc
Target
Ti  60 eV, r  3.8 g/cc

10.  Gekko/HIPER S.Yu.Gus’kov. LPI RAS
Impactor’s density significantly less than target’s density:
imp  0.6 g/cm3 << t  4 g/cm3
Predominant heating of impactor’s ions,Ti>>Te . Equilibrium target’s plasma Ti=Te . Impactor’s temperature significantly larger than target’s temperature:
Timp  (1.5 -3) keV >> Tt  ( ) keV
Neutron yield from impactor significantly larger than neutron yield from the target:
Nm  107 >> Nm  106 
Confirmation of the approach:
initial ignition of impactor and subsequent propagation of detonation wave
from impactor to compressed thermonuclear fuel of ICF-target

11. Fast ignition by detonating hydrodynamic flow
S.Yu.Gus’kov. LPI RAS
Fast ignition by detonating hydrodynamic flow

12. Ignition by Detonating Impactor - “Target From Target” Ignition
S.Yu.Gus’kov. LPI RAS
Detonating impactor
Development of “Cone-Guided Impactor” to “Target inside Target”
Ignition by Detonating Impactor - “Target From Target” Ignition
Two well-known ICF-methods:
1. Profiled Laser Pulse and 2. Initial Density Distribution
Multi-layer cone target
1. Cone target with
homogeneous DT-fuel
and profiled laser pulse
2. Cone target with
spatial distributed
density
Ablator
Pusher
Igniter
Cone
target
Cone
target
Cone
target
ICF-target
ICF-target
ICF-target

13. m t General requirement for ignition by detonating DT-impactor
S.Yu.Gus’kov. LPI RAS
General requirement for ignition by detonating DT-impactor
1. Ignition of the impactor:
2. Detonation wave to DT-fuel:
United requirement :
Minimal ignition energy, m= t :
Factor of exceeding:
m t

14. “Target from Target” Ignition by Three-Layer Cone Target
S.Yu.Gus’kov. LPI RAS
“Target from Target” Ignition by Three-Layer Cone Target

15. Three-layer cone target
S.Yu.Gus’kov. LPI RAS
Three-layer cone target
1. Ablator.
Light-element material: (CH)n-plastics, Be, Al and others.
Function: Acceleration of impactor  laser light absorption, ablation pressure creation.
Totally evaporated at the acceleration stage.
2. Pusher.
Heavy-element material: Cu, Pb, Au and others.
Function: Impact-driven adiabatic compression of the igniter.
3. DT-ice Igniter.
Function: Self-burning and ignition of ICF-target DT fuel by the detonation wave

16. Statement of the Problem. Planar Approximation.
S.Yu.Gus’kov. LPI RAS
Statement of the Problem. Planar Approximation.
Pressure in the igniter at a burning stage:
R=0.4 г/см2, T=10 keV, =100 г/см2  P~ Gbar
1. Deceleration of the igniter by first shock wave, Pb0 << Pt
2. Deceleration of the pusher and adiabatic compression of the ignitor, Pb>>Pb0
3. Shock wave in ICF-Target DT-fuel; Effect of DT-fuel compressibility, Pb>Pt

17. Residual kinetic energy of the impactor
S.Yu.Gus’kov. LPI RAS
Compression and heating of the igniter
The moment of maximal compression: deceleration of the impactor down to the velocity of shock wave in ICF-target DT-fuel
Energy of shock wave in
ICF-target DT-fuel
Residual kinetic energy of the impactor
Adiabatic compression at the initial entropy from first shock wave:
1. Residual kinetic energy of the impactor:
2. Energy of shock wave in ICF-target DT-fuel:

18. Uncompressible ICF-target fuel: Compressible ICF-target fuel:
S.Yu.Gus’kov. LPI RAS
Final state of the igniter
Exact solution for m= s= t= :
“Uncompressible” solution
Compressibility factor
Internal energy of igniter
Uncompressible ICF-target fuel:
Pb/Pw  1100,m  75 g/cm3; T=10 keV, at um 365 km/s; energy factor, 0.25
Au-pusher, Ms/Mm=20
Compressible ICF-target fuel:
Pb/Pw  700; m  52 g/cm3; T=10 keV, at um 410 km/s; energy factor, 0.18

19. Final igniter density and velocity of ignition
S.Yu.Gus’kov. LPI RAS
Final igniter density and velocity of ignition
Pusher and igniter mass ratio vs
final igniter density
1, 2, 3, 4 - energy factor, Em / E0 = 0.3
5, 6, 7, 8 - energy factor, Em / E0 = 0.5
Tig=10 keV:
initial impactor velocity vs final igniter density
t=500g/cc
t=300g/cc
t=200g/cc
uncompressible ICF-target fuel
u  330 km/s
Au-pusher: Mpusher/Migniter 38
DT-igniter, ()ig=0.4 g/cm2:
ig  40 m  Migniter  g
Mpusher g
t=300 g/cm3
Eigniter/Eimpactor = 0,56
ig=100 g/cm3
Initial: Eimpactor  70 kJ
Final: Eigniter  40 kJ

20. Conical three - layer igniting target design
S.Yu.Gus’kov. LPI RAS
Conical three - layer igniting target design

21. Igniting target. Requirements to the design
S.Yu.Gus’kov. LPI RAS
Igniting target. Requirements to the design
 2R0 
Cone opening angle
 
(R)ig , ig L
(R)t , t
Ignition of the igniter: (R)ig=0.4 g/cm2
High gain of ICF-target (R)t=3-4 g/cm2
Shell velocity:
Evaporation - 50%, M0 / Mf = 2  Mass of ablator = a half of total mass,
  0.3, u  0.57(I2)1/3
Eimp=70 kJ, u = cm/s, =0.3, =50o,  = 0.35 m
R0 cm, L0. 32 cm,  19.5ns

22. Be-ablator: Mablator=Mpusher Elaser= Eimpactor / Kabs
S.Yu.Gus’kov. LPI RAS
Igniting conical target design
R0 cm
DT-igniter:
Migniter  g
Au-pusher:
Mpusher g
Be-ablator: Mablator=Mpusher
Elaser= Eimpactor / Kabs
Eimpactor  70 kJ
 = 0.3, Kabs= 0.7
Elaser  320 kJ
igniter  21,3 m
pusher  m
ablator  m
 2R0  0.3 cm
  m
  m
L  cm
  21,3 m
=50o

23. Conclusion: Practicability of hydrodynamic ignition at the velocity of 300-500 km/s
1. Fast Ignition by Detonating Hydrodynamical Flow
Approach of “Target from Target” ignition
Conical three-layer igniting target:
Ignition at the initial velocity of hydrodynamical flow 330 km/s
and final density of detonating flow 100 g/cm3
Laser parameters: EL= 320 kJ, L= 19.5 ns
2. Key points:
Hydrodynamic instability
Impactor’s state before impact
EOS of heavy pusher
3. Experiments: collision of multi-layer impactor accelerated along conical or cyllindrical channels with a massive plane target.