1. U N C L A S S I F I E D LA-UR- 06-4281 Ion driven Fast Ignition Transport, stopping and energy loss of MeV/amu ions in WDM B. Manuel Hegelich LULI July 2006

2. U N C L A S S I F I E D LA-UR- 06-4281 Experimental Team Experiment: B. Manuel Hegelich, PI, P-24 Kirk A. Flippo, P-24 Cort Gautier, P-24 Juan C. Fernandez, P-24 Theory: Mark Schmitt, X-1 Brian Albright, X-1 Lin Yin, X-1 D. Gericke, Univ. Warwick Collaborators: LULI: J. Fuchs, P. Antici, P. Audebert SNL: E. Brambrink, M. Geissel GSI: M. Schollmeier, Knut, F. Nürnberger, M. Roth LMU Munich/MPQ: J. Schreiber, A. Henig

3. U N C L A S S I F I E D LA-UR- 06-4281 Outline Ion-driven fast ignition: Concept, parameters, & challenges Laser-driven stopping power experiment Preliminary results Summary

4. U N C L A S S I F I E D LA-UR- 06-4281 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/cm 3 2. Alpha-particle range sets the minimum hot-spot size (r  10  m) – realistically  25  m ion- beam diameter 3. Hot-spot disassembly (c S  ~ 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 N~7x10 15 E~11 kJ N~4x10 16 E~26 kJ Protons

5. U N C L A S S I F I E D LA-UR- 06-4281 FI conditions: Hotspot size is ~(25  m) 3 n e ~ 10 26 cm -3, T e,start ~ 1 keV, T e,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. FI carbon ions are ~100x as energetic as FI protons  100x fewer particles are needed, i.e. N C ~2 x 10 14 * ISAAC code (Ion Stopping At Arbitrary Coupling) Gericke et al., LPB 20, (2002) 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.

6. U N C L A S S I F I E D LA-UR- 06-4281 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) Cleaned Pd-target Laser pulse preplasma Monoenergetic Carbon Co-moving e- Multitude of Pd substrate Charge stages 10Å graphitized source layer

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

8. U N C L A S S I F I E D LA-UR- 06-4281 - 6° TP2 + 6° TP1 Accelerating Laser Pulse Plasma Creation Short-Pulse Ion Generation Target Dense Plasma Target Electron Sheath Ion Beam Plasma Probe Beam Refluxing hot electrons Proposed Beam Time LULI 2006: Ion Transport through dense plasmas by comparison of charge state and energy distributions. Estimated spectra:

9. U N C L A S S I F I E D LA-UR- 06-4281 Ion transport in WDM, LANL-LULI Experiment @ the LULI 100TW Laser: Setup and diagnostics Ion acceleration shortpulse 0.35 ps, 20 J, 4x10 19 W/cm 2 Cw-cleaning laser ~10 W (LANL) Target Pre-shot Target diagnostics (Pyrometer, RGA) 2w probe pulse 0.35 ps, ~20mJ Accelerated ions Thomson parabolas Isochoric heating shortpulse 0.45 ps, 8 J, 1x10 17 W/cm 2 +5° -5°

10. U N C L A S S I F I E D LA-UR- 06-4281 Target heated by 10W cw laser (532 nm) 92 Pd-CVD 900 °C 93 Pd-Al 902 °C

11. U N C L A S S I F I E D LA-UR- 06-4281 Time (ps) 0.1.2.3.4.5.6.7.8.9 1.0 Laser Intensity Laser temporal profile Foil Targets Heated with 2  laser in a.5 ps pulse luli12 Example Laser and Target Geometry luli12 Target laser ablation z (cm) r (cm)

12. U N C L A S S I F I E D LA-UR- 06-4281 Carbon Burns Through Faster Than Gold z(cm) r(cm) Carbon Electron Density z (cm) r (cm) Gold Electron Density Snapshots at 50 ps after 400 fs laser pulse illumination

13. U N C L A S S I F I E D LA-UR- 06-4281 X [cm] Te [keV] 1: t = 1 ps 2: t = 10 ps 3: t = 50 ps 4: t = 100 ps 5: t = 0 ps Electron temperatures of 40-70 keV predicted by LASNEX

14. U N C L A S S I F I E D LA-UR- 06-4281 Velocity of Critical Surface Simulated with Lasnex 12  m Thick Carbon and Gold Targets Intensity of 2x10 17 W/cm 2 during 400 fs pulse with 100  m Ø spot size Lower density Carbon produces higher critical surface velocity Gold Carbon Time (ps) Velocity (km/s) luli33 luli34 10 -5 10 -4.001.01 0.1 1 10 100 1000 1300 1000 500 0

15. U N C L A S S I F I E D LA-UR- 06-4281 Target expansion velocities measured by shortpulse shadowgraphy

16. U N C L A S S I F I E D LA-UR- 06-4281 Shot 88: Pd-primary (900 °C), C-secondary CR-39 #: 85+86; I i = 6.85e19; I h = 2.23e17 Passed through cold matterFree streaming

17. U N C L A S S I F I E D LA-UR- 06-4281 Shot 88: Pd-primary (900 °C), C-secondary CR-39 #: 85+86; I i = 6.85e19; I h = 2.23e17 Passed through plasmaFree streaming

18. U N C L A S S I F I E D LA-UR- 06-4281 Shot 68; 88: Pd-primary (1170; 900 °C), C-secondary CR-39 #: 46, 47; 85,86; I i = 4.5e19 6.9e19; I h = 0; 2.2e17 Passed through plasma Free streamingPassed through cold matter 47 47 + 86 86 46 85

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

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

21. dense plasma 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 ions electrons collisions with ions knocked-on light ion Z eff (x) ion stopping energy deposition collisions with e - collective e - modes B fields & collective ion modes

22. U N C L A S S I F I E D LA-UR- 06-4281 Shot 68: Pd-primary (1170 °C), C-secondary, not heated CR-39 #: 47; I i = 4.5e19 W/cm 2 ; I h = 0, free streaming

23. U N C L A S S I F I E D LA-UR- 06-4281 Shot 68: Pd-primary (1170 °C), C-secondary, not heated, CR-39 #: 46; I i = 4.5e19 W/cm 2 ; I h = 0, blocked by secondary

24. U N C L A S S I F I E D LA-UR- 06-4281 Shot 88: Pd-primary (900 °C), C-secondary CR-39 #: 86; I i = 6.85e19; I h = 2.23e17, free streaming

25. U N C L A S S I F I E D LA-UR- 06-4281 Shot 88: Pd-primary (900 °C), C-secondary CR-39 #: 85; I i = 6.9e19; I h = 2.2e17, blocked by secondary

26. U N C L A S S I F I E D LA-UR- 06-4281 Knut 76

27. U N C L A S S I F I E D LA-UR- 06-4281 Knut 77