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

U N C L A S S I F I E D LA-UR- 06-4281

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


Outline

• Ion-driven fast ignition: Concept, parameters, & challenges

• Laser-driven stopping power experiment

• Preliminary results

• Summary


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


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.


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


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


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:


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


Target heated by 10W cw laser (532 nm)

92Pd-CVD900 °C

93Pd-Al902 °C


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


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

U N C L A S S I F I E DLA-UR- 06-4281

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


Target expansion velocities measured by shortpulse shadowgraphy


Shot 88: Pd-primary (900 °C), C-secondaryCR-39 #: 85+86; Ii = 6.85e19; Ih = 2.23e17

Passed through cold matterFree streaming


Shot 88: Pd-primary (900 °C), C-secondaryCR-39 #: 85+86; Ii = 6.85e19; Ih = 2.23e17

Passed through plasmaFree streaming


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


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



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


Shot 68: Pd-primary (1170 °C), C-secondary, not heated CR-39 #: 47; Ii = 4.5e19 W/cm2; Ih = 0, free streaming


Shot 68: Pd-primary (1170 °C), C-secondary, not heated, CR-39 #: 46; Ii = 4.5e19 W/cm2; Ih = 0, blocked by secondary


Shot 88: Pd-primary (900 °C), C-secondaryCR-39 #: 86; Ii = 6.85e19; Ih = 2.23e17, free streaming


Shot 88: Pd-primary (900 °C), C-secondaryCR-39 #: 85; Ii = 6.9e19; Ih = 2.2e17, blocked by secondary


Knut 76


Knut 77

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Ion driven Fast Ignition