P (TW)
1
P (TW) t (ns) ICF Context Inertial Confinement Fusion Classical schemes Direct- Drive Fusion Indirect- Drive Fusion Central hot spot ignition Alternative schemes Fast Ignitio n Shock Ignition Hole boring, impact ignition Ignition by relativistic electron beams Ignition by a strong convergent shock How does it work ? Homothetic targets performance study arg t et réf r h r 3 arg t et réf M hM arg t et ref t ht arg t et réf R hR arg t et ref G hG 2 arg Lt et L réf P hP 3 arg Lt et L réf E hE I V = 290 km/s =1,9.10 14 W/cm² L I m ax = 650g/cc =1,2 The intensity threshold required for ignition is not homothetic : P shock is not varying by h² Shock ignition principle Non-isobaric configuration • A strong convergent shock is produced by ignition pulse • The ignitor shock catches up the compression shock reflected at the center of the target near the inner interface of the shell • The resulting assembly shows that the hot spot pressure is greater than the surrounding fuel pressure that leads to ignition In the shock ignition scheme, the high nonisobaric nature of the final fuel leads to achieve the ignition conditions SH HS P P Fuel non-isobaric parameter Convergent shock Ignitor shock Return shock Pressure amplification 0,7 Gbars 300 Gbars Optimal shocks collision : Amplification by a factor 6 CHIC shock pressure Guderley solution 5 3 Guderley self-similar solution in spherical symmetry for an ideal gas ( ) : 0,69 shock r t 0,9 shock shock P r The shock ignition pressure amplification and the spherical effect are well- described by the Guderley model Von Guderley.G, Luftfahrt-Forsch, 9, 302, (1942) Centre Lasers Intenses et Applications, Université Bordeaux 1- CNRS - CEA Shock ignition : modelling elements and target robustness M. Lafon, X. Ribeyre and G. Schurtz FWHM (ps) ΔT (ps) E abs (kJ) E TN (MJ) 500 300 40 19 400 200 32 18 300 100 24 17 250 50 20 16 If spike duration decreases about 50%, thermonuclear energy only decreases about 15% Ignition pulse robustness Standart impulsion duration Spike power time shape t Ps Ps/2 T TR TF Laser time rise : TR =TF = 200 ps Pulse duration at FWHM : TM+ΔT+TD The spike power remains constant : P S =cte The ignition mainly depends on the spike power and not on the spike energy Compression laser energy (kJ) 25 85 180 312 600 Parameter h 0.5 0.8 1 1.2 1.5 Target Mass (mg) 0.07 0.28 0.59 1.0 2.0 Threshold absorbed spike power (TW) 67 76 86 97 118 Absorbed spike intensity (10 15 W/cm²) 16 5.6 4 2.8 2 Compression areal density (g/cm²) 0.8 1.18 1.34 1.6 1.9 Thermonuclear energy (MJ) 1 8 17 38 80 Shock ignition performance domain The required spike power strongly increases when the implosion velocity decreases (< 240 km/s) Beyond 350 km/s, the HIPER target self-ignites There is to reach a compromise between the target intensity and the implosion velocity In the shock ignition scheme, the implosion velocity field is optimal for the range 240 < V imp (km/s) < 290 Conclusions and prospects • Runs of simulations 1D shows the robustness of the shock ignition scheme •The spike impulsion leading to ignition mainly depends on spike power and not on spike energy • The Rosen model study shows the influence of the non-isobaric parameter : at constant mass, the laser energy required for ignition is lower for the shock ignition scheme than for the classical isobaric configuration scheme • The shock ignition pressure evolution is well-described by the Guderley model during convergence • The required spike laser power family is not homothetic with the target size for a family of homothetic targets: the power threshold does not increase as much as the homothetic factor of the target size • An optimal domain of use might be defined by making a compromise between the intensity on target and the implosion velocity • A study on 2D effetcs will be performed • The analytical model has to be detailed and improved using the Guderley model in order to best describe the shock dynamics • Hydrodynamic instabilities have to be evaluated according to the target irradiation symmetry HIPER target shock ignition robustness Run series of CHIC 1D using radial rays and total energy absorption at critical Ribeyre, X et al., Plasma Phys. Cont. Fusion, 51, 015013 (2009) Compression : 180 kJ into 10 ns (50TW) Ignition : 80 kJ into 500 ps (150TW) + E TN =20 MJ Gain = 80 Iso-thermonuclear energy curves 250ps Ignition pulse Compression puls e For all targets : Lase r Gain model Référence 522µm 814µm 1044µm 1250µm 1570µm 5 mg 1 mg 0,5 mg 0,1 mg 0,01 mg Rosen model CHIC simulations 200 SH P Gbars 3 3 3/5 2/5 2 3/5 8/5 2 3,95 2560 16,9 fuel L SH SH SH M E P P P fuel M HS P The Rosen and Lindl model has been reviewed taking into consideration the influence of the non-isobaric nature of the fuel induced by the ignitor shock: M.D.Rosen and J.D.Lindl (1984) UCRL-50021-83 defining the hot spot at ignition instant: Fuel mass shell adiabat at stagnation coupling efficiency between the laser energy and the internal DT fuel energy shell pressure 2 HS RT At constant mass, Rosen model shows the low threshold and high gain possibility of a non-isobaric configuration. CHIC simulations are well-described by the Rosen model Intensity (10 15 W/cm²) Parametric instabilities H y d r o d y n a m i c i n s t a b i l i t i e s P L =110TW P L =340TW P L =130TW h = 0,5 h = 1 h = 2 Mass=0,59mg Simple, spherical and scalable target The laser type required is the same for both compression and ignition stages • Compression and ignition stages are partially uncoupled • Low isentrope fuel assembly • Classical medium implosion velocity (≈ 290km/s) in opposition to conventional hot spot ignition (≈350-400km/s) Betti.R et al. Phys. Rev. Letters, 98, 155001 (2007) HIPER target ρ sh P hs r HS r SH P sh ρ hs Hot Spot Shell Hot spot ignition condition : cond rad mech W W W W The self-heating condition for non-isobaric case can be written as : ( , ) HS HS HS HS SH R fT The hot spot enters the ignition domain with specific values of and which depends on the fuel non isobaric parameter ε HS HS R HS T When : isobaric configuration SH HS Shock launching time Absorbed spike power
description
Parametric instabilities. Ps. D T. Référence. =1,9.10 14 W/cm². TR. TF. Ps/2. 5 mg. = 290 km/s. Mass=0,59mg. 1 mg. = 650g/cc. Hydrodynamic instabilities. t. =1,2. 0,5 mg. Simple , spherical and scalable target. 1044µm. 522µm. 814µm. 1250µm. 1570µm. Return shock. 0,1 mg. - PowerPoint PPT Presentation
Transcript of P (TW)
P (TW)
t (ns)
ICF Context Inertial Confinement Fusion
Classical schemes
Direct-Drive Fusion
Indirect-Drive Fusion
Central hot spot ignition
Alternative schemes
Fast Ignition
Shock Ignition
Hole boring, impact ignition
Ignition by relativistic
electron beams
Ignition by a strong convergent
shock
How does it work ?
Homothetic targets performance study
argt et
réf
rh
r
3argt et réfM h M
argt et reft htargt et réfR h R
argt et refG hG 2argLt et LréfP h P
3argLt et LréfE h E
IV = 290 km/s
=1,9.1014 W/cm²LI
max = 650g/cc
=1,2
The intensity threshold required for ignition is not homothetic : Pshock is not varying by h²
Shock ignition principleNon-isobaric configuration • A strong convergent shock is produced by ignition pulse
• The ignitor shock catches up the compression shock reflected at the center of the target near the inner interface of the shell
• The resulting assembly shows that the hot spot pressure is greater than the surrounding fuel pressure that leads to ignition
In the shock ignition scheme, the high nonisobaric nature of the final fuel leads to achieve the ignition conditions
SH
HS
PP
Fuel non-isobaric parameter
Convergent shock
Ignitor shock
Return shock
Pressure amplification
0,7 Gbars
300 Gbars
Optimal shocks collision :Amplification by a factor 6
CHIC shock pressure Guderley solution
53
Guderley self-similar solution in spherical symmetry for an ideal gas ( ) :
0,69shockr t
0,9shock shockP r
The shock ignition pressure amplification and the spherical effect are well-described by the Guderley modelVon Guderley.G, Luftfahrt-Forsch, 9, 302, (1942)
Centre Lasers Intenses et Applications, Université Bordeaux 1- CNRS - CEA
Shock ignition : modelling elements and target robustnessM. Lafon, X. Ribeyre and G. Schurtz
FWHM (ps)
ΔT (ps)
Eabs
(kJ)ETN
(MJ)
500 300 40 19400 200 32 18300 100 24 17250 50 20 16
If spike duration decreases about 50%, thermonuclear energy only decreases about 15%
Ignition pulse robustness
Standart impulsion duration
Spike power time shape
t
Ps
Ps/2T
TR TF
Laser time rise : TR =TF = 200 ps
Pulse duration at FWHM : TM+ΔT+TD
The spike power remains constant : PS=cte
The ignition mainly depends on the spike power and not on the spike energy
Compression laser energy (kJ) 25 85 180 312 600
Parameter h 0.5 0.8 1 1.2 1.5
Target Mass (mg) 0.07 0.28 0.59 1.0 2.0
Threshold absorbed spike power (TW) 67 76 86 97 118
Absorbed spike intensity (1015 W/cm²) 16 5.6 4 2.8 2
Compression areal density (g/cm²) 0.8 1.18 1.34 1.6 1.9
Thermonuclear energy (MJ) 1 8 17 38 80
Shock ignition performance domain
The required spike power strongly increases when the implosion velocity decreases (< 240 km/s)
Beyond 350 km/s, the HIPER target self-ignites
There is to reach a compromise between the target intensity and the implosion
velocity
In the shock ignition scheme, the implosion velocity field is optimal for the range
240 < Vimp (km/s) < 290
Conclusions and prospects• Runs of simulations 1D shows the robustness of the shock ignition scheme
•The spike impulsion leading to ignition mainly depends on spike power and not on spike energy
• The Rosen model study shows the influence of the non-isobaric parameter : at constant mass, the laser energy required for ignition is lower for the shock ignition scheme than for the classical isobaric configuration scheme
• The shock ignition pressure evolution is well-described by the Guderley model during convergence
• The required spike laser power family is not homothetic with the target size for a family of homothetic targets: the power threshold does not increase as much as the homothetic factor of the target size
• An optimal domain of use might be defined by making a compromise between the intensity on target and the implosion velocity
• A study on 2D effetcs will be performed
• The analytical model has to be detailed and improved using the Guderley model in order to best describe the shock dynamics
• Hydrodynamic instabilities have to be evaluated according to the target irradiation symmetry
• The limiting factors of laser-plasma interaction must be defined, especially concerning the parametric instabilities
HIPER target shock ignition robustness
Run series of CHIC 1D using radial rays and total energy absorption at critical
Ribeyre, X et al., Plasma Phys. Cont. Fusion, 51, 015013 (2009)Compression : 180 kJ into 10 ns (50TW)
Ignition : 80 kJ into 500 ps (150TW)
+ ETN=20 MJ Gain = 80
Iso-thermonuclear energy curves
250ps
Ignition pulse
Compression pulse
For all targets :
Laser
Gain model
Référence
522µm 814µm 1044µm 1250µm 1570µm
5 mg
1 mg
0,5 mg
0,1 mg
0,01 mgRosen modelCHIC simulations
200SHP Gbars
3 33 / 5 2 / 5 2 3 / 5 8 / 5 23,95 2560 16,9fuel
L SH SH SH
ME P P P
fuelM
HSP
The Rosen and Lindl model has been reviewed taking into consideration the influence of the non-isobaric nature of the fuel induced by the ignitor shock:
M.D.Rosen and J.D.Lindl (1984) UCRL-50021-83
defining the hot spot at ignition instant:
Fuel mass
shell adiabat at stagnation
coupling efficiency between the laser energy and the internal DT fuel energy
shell pressure
2HS
RT
At constant mass, Rosen model shows the low threshold and high gain possibility of a non-isobaric configuration. CHIC simulations are well-described by the Rosen model
Inte
nsity
(1015
W/c
m²) Parametric
instabilities
Hydrodynam
ic instabilities
PL=110TW
PL=340TW
PL=130TW
h = 0,5h = 1h = 2
Mass=0,59mg
Simple, spherical and scalable target
The laser type required is the same for both compression and ignition stages
• Compression and ignition stages are partially uncoupled
• Low isentrope fuel assembly
• Classical medium implosion velocity (≈ 290km/s) in opposition to conventional hot spot ignition (≈350-400km/s)
Betti.R et al. Phys. Rev. Letters, 98, 155001 (2007)
HIPER target
ρsh
Phs
rHS rSH
Psh
ρhs
Hot Spot
Shell
Hot spot ignition condition :
cond rad mechW W W W
The self-heating condition for non-isobaric case can be written as :
( , )HSHS HS HS
SH
R f T
The hot spot enters the ignition domain with specific values of and which depends on the fuel non isobaric parameter ε
HS HSRHST
When : isobaric configurationSH HS
Shock launching time
Absorbed spike power
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