Ion driven Fast Ignition
description
Transcript of Ion driven Fast Ignition
U N C L A S S I F I E DLA-UR- 06-4281
Ion driven Fast Ignition
Transport, stopping and energy loss of MeV/amu ions in WDM
B. Manuel Hegelich
LULIJuly 2006
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Experimental Team
Experiment:B. Manuel Hegelich, PI, P-24Kirk A. Flippo , P-24Cort Gautier, P-24Juan C. Fernandez, P-24
Theory:Mark Schmitt, X-1Brian Albright, X-1Lin Yin, X-1D. Gericke, Univ. Warwick
Collaborators:LULI: J. Fuchs, P. Antici, P. AudebertSNL: E. Brambrink, M. GeisselGSI: M. Schollmeier, Knut, F. Nürnberger, M. RothLMU Munich/MPQ: J. Schreiber, A. Henig
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Outline
• Ion-driven fast ignition: Concept, parameters, & challenges
• Laser-driven stopping power experiment
• Preliminary results
• Summary
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There are 3 different envisioned FI scenarios: electrons, protons and light ions. Each has different challenges
Detailed study on proton fast ignition:
Temporal et al., Phys. Plas. 9 (2002) 3098
1.fuel density 300 – 500 g/cm3
2.Alpha-particle range sets the minimum hot-spot size (r 10 m)
– realistically 25 m ion-beam diameter
3.Hot-spot disassembly (cS ~ r, 20 ps)
– sets required power – Constrains combinations of
ion-energy spread & distance between ion source & fuel
Smaller ion energy spread → larger tolerable separation, less energy in ion beam required
0 5 10 15 20 251E12
1E13
1E14
1E15
N
Energy [MeV]
N
N~7x1015
E~11 kJ
N~4x1016
E~26 kJ
Protons
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FI conditions:
Hotspot size is ~(25 m)3
ne ~ 1026 cm-3,
Te,start ~ 1 keV,
Te,end ~ 10 keV.
Modeling* of C6+ stopping in fuel yields:,
40 MeV/u initially required,
9 MeV/u after fuel started to heat,
33 MeV/u to account for losses in preplasma.
0 10 20 30 400
10
20
30
40
Projectile: C6+, Target: ne = 1x1026
Ep = 40 MeV/u, T
e = 1 KeV
Ep = 33 MeV/u, T
e = 3 KeV
Ep = 23 MeV/u, T
e = 5 KeV
Ep = 9 MeV/u, T
e = 10 KeV
dE
/dx
[MeV
/m]
Range [m]
FI carbon ions are ~100x as energetic as FI protons 100x fewer particles are needed, i.e. NC~2 x 1014
* ISAAC code (Ion Stopping At Arbitrary Coupling) Gericke et al., LPB 20, (2002)
-100 -50 0 50 100 150
0
2x1025
4x1025
6x1025
8x1025
1x1026
ne [c
m-3]
r [m]
ne
0 50 100 150 200 250
0
50
100
150
200
250
300
350
400
Range [m]
Energ
y [M
eV
]
Projectile: C6+, Target: ne = 2x1026
Ep = 384 MeV (33 MeV/u), T
e = 10 KeV
Demonstration of monoenergetic ion acceleration makes carbon an interesting candidate for Fast Ignition. 30-40 MeV/u is needed due to its stopping in the hot, dense fuel plasma.
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Challenges for light ion based Fast Ignition:
• Requires a tailored spectrum (quasi mono-energetic ions)– Demonstrated: Hegelich et al., Nature 439, 441
(2006)
• Higher ion energies (30-40 MeV/amu), conversion efficiency– Empirical scaling laws: ~2 kJ laser energy– Novel target designs– New acceleration mechanism (Yin, Hegelich et
al., LPB 24, 291 (2006))– K. Flippo (talk, Friday), B. Albright (talk, Sunday)
• Particle transport and stopping in WDM – Strong theory effort: Model by Gericke, Murillo
et al.– Ongoing experiments (LULI, Trident)
1 10104
105
106
107
Ion
s [M
eV-1 m
srd
-1]
Energy [MeV]
Cleaned Pd-target
Laser pulse
preplasma
MonoenergeticCarbonCo-moving e-
Multitude of Pd substrateCharge stages
10Å graphitized source layer
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Ion transport and stopping in WDM
Goal: investigate the stopping of MeV/nucleon ions in warm dense matter.
Challenge: – Creating solid density warm dense matter (~50 eV)– WDM disassembles on ns timescales– Accelerator ion pulses have ~100ns pulse duration
Solution: – Shortpulse laser isochorically heats target plasma– Shortpulse laser creates ps ion beam
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0 10 20 300.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
dE
/dx
[MeV
/mu]
Range [mu]
12 MeV C in 66eV, 2.41e23 Al-Plasma, (Gericke) 12 MeV C in solid, cold Al (Srim)
- 6° TP2
+ 6° TP1
AcceleratingLaser Pulse
Plasma Creation
Short-Pulse
Ion GenerationTarget
DensePlasmaTarget
ElectronSheath
Ion Beam
Plasma
Probe Beam
Refluxing hot electrons
0 4 8 12 16 20 24 28105
106
107
108
109
Typical C-spectra from heated target
C1+ C2+ C3+ C4+ C5+
Ion
s [
Me
V-1 m
srd
-1]
Energy [MeV]
105
106
107
108
109
Al-plasma, 10m, T=66eV, ne=2.41x1023
Al-foil, cold, 10m
105
106
107
108
109
no interaction target
Proposed Beam Time LULI 2006: Ion Transport through dense plasmas by comparison of charge state and energy distributions.Estimated spectra:
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Ion transport in WDM, LANL-LULI Experiment @ the LULI 100TW Laser: Setup and diagnostics
Ion acceleration shortpulse0.35 ps, 20 J, 4x1019 W/cm2
Cw-cleaning laser~10 W (LANL)
Target
Pre-shot Target diagnostics (Pyrometer, RGA)
2w probe pulse0.35 ps, ~20mJ
Accelerated ions
Thomsonparabolas
Isochoric heating shortpulse0.45 ps, 8 J, 1x1017 W/cm2
+5°
-5°
0 4 8 12 16 20 24 28105
106
107
108
109
Typical C-spectra from heated target
C1+ C2+ C3+ C4+ C5+
Ion
s [M
eV-1 m
srd
-1]
Energy [MeV]
105
106
107
108
109
Al-plasma, 10m, T=66eV, ne=2.41x1023
Al-foil, cold, 10m
105
106
107
108
109
no interaction target
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Target heated by 10W cw laser (532 nm)
92Pd-CVD900 °C
93Pd-Al902 °C
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Carbon Burns Through Faster Than Gold
z(cm)
r(cm
)
Carbon Electron Density
z (cm)
r (c
m)
Gold Electron Density
• Snapshots at 50 ps after 400 fs laser pulse illumination
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X [cm]
Te
[keV
]
1: t = 1 ps2: t = 10 ps3: t = 50 ps4: t = 100 ps5: t = 0 ps
Electron temperatures of 40-70 keV predicted by LASNEX
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Velocity of Critical Surface Simulated with Lasnex
• 12m Thick Carbon and Gold Targets• Intensity of 2x1017 W/cm2 during 400 fs pulse with 100 m Ø spot size
• Lower density Carbon produces higher critical surface velocity
Gold
Carbon
Time (ps)
Vel
oci
ty (
km/s
)
luli33luli34
10-5 10-4 .001 .01 0.1 1 10 100 1000
1300
1000
500
0
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Target expansion velocities measured by shortpulse shadowgraphy
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Shot 88: Pd-primary (900 °C), C-secondaryCR-39 #: 85+86; Ii = 6.85e19; Ih = 2.23e17
Passed through cold matterFree streaming
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Shot 88: Pd-primary (900 °C), C-secondaryCR-39 #: 85+86; Ii = 6.85e19; Ih = 2.23e17
Passed through plasmaFree streaming
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Shot 68; 88: Pd-primary (1170; 900 °C), C-secondaryCR-39 #: 46, 47; 85,86; Ii = 4.5e19 6.9e19; Ih = 0; 2.2e17
Passed through plasma
Free streaming Passed through cold matter
47
47 + 86
8646
85
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Preliminary Summary
• Experiment was designed to be a proof-of-principle for ion stopping in WDM with laser-driven ions
• TP + target alignment tricky but possible
• New pyrometer works reliably
• Reproducable free streaming ion distribution
• Clear difference between stopping in cold target and plasma
• Need for better diagnostic for target plasma
• Preliminary results seem to disagree with model
• Monoenergetic carbon reproduced on different laser system, we know have results from both Trident and LULI 100TW
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denseplasma
• Validate models of atomic-physics evolution of beam ions in dense plasmas (ionization, charge X & recombination).
• Validate models of knock-on cascades (heavy-ion collisions with light ions)
• Validate reduced models of beam-energy deposition (e.g., Gericke et al.*) – Critical for “slow” ions, i.e.,
MeV/nucleon ions near the end of their range.
Theory of ion stopping in plasmas is only poorly understood:
* D. O. Gericke, Laser Part. Beams 20 (2003) 471; Gericke & Schlanges, Phys. Rev. E 67 (2003) 037401.
• Fluid beam-plasma instabilities from interaction of beam & plasma electrons
beam
ionselectrons
collisionswith ions
knocked-onlight ionZeff (x)
ion stoppingenergy deposition
collisionswith e-
collectivee- modes
B fields &collectiveion modes
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Shot 68: Pd-primary (1170 °C), C-secondary, not heated CR-39 #: 47; Ii = 4.5e19 W/cm2; Ih = 0, free streaming
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Shot 68: Pd-primary (1170 °C), C-secondary, not heated, CR-39 #: 46; Ii = 4.5e19 W/cm2; Ih = 0, blocked by secondary
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Shot 88: Pd-primary (900 °C), C-secondaryCR-39 #: 86; Ii = 6.85e19; Ih = 2.23e17, free streaming
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Shot 88: Pd-primary (900 °C), C-secondaryCR-39 #: 85; Ii = 6.9e19; Ih = 2.2e17, blocked by secondary
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Knut 76
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Knut 77