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Shock Fast-Ignition of Thermonuclear Fuel with High Areal Density

Shock ignitor pulse. Fuel assembly pulse. RX prepulse. FSC. Shock Fast-Ignition of Thermonuclear Fuel with High Areal Density. 3 rd FSC Meeting January 26-27, 2006 Rochester, NY. C. Zhou, R. Betti LLE-University of Rochester J. Perkins, LLNL. FSC. Summary.

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Shock Fast-Ignition of Thermonuclear Fuel with High Areal Density

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  1. Shock ignitor pulse Fuel assembly pulse RX prepulse FSC Shock Fast-Ignition of Thermonuclear Fuel with High Areal Density 3rd FSC Meeting January 26-27, 2006 Rochester, NY C. Zhou, R. Betti LLE-University of Rochester J. Perkins, LLNL

  2. FSC Summary High density/areal density fuel can be ignited with a spherically convergent shock driven by a laser intensity spike • High density/areal density fuel can be assembled through low velocity, low adiabat implosions. • 1-D simulations show that such a fuel assembly can be ignited by a spherically convergent shock. • Two designs are presented with 100kJ and 500kJ fuel assemblies ignited by a 60kJ and 200kJ shock respectively. • 2-D simulations are being performed to evaluate the target robustness to inner surface roughness and laser imprinting.

  3. FSC Low implosion velocity targets have better performance (small RT growth and high gain if ignited). But these targets are difficult to ignite by standard direct drive ICF implosions. • Low velocity = high gain G • Low velocity = low RT growth. Ne = number of RT e-folding. • However, low velocity = large energy for ignition. Eign is the energy required for ignition. R. Betti, GO1.07 M.C.Herrmann et al., Nucl. Fusion 41, 99 (2001)

  4. CH 2μm CH(DT)6 80μm DT ice 147μm DT gas 453μm FSC A 100kJ RX-shaped pulse can assemble fuel with ρR=1.6g/cm2 through a slow (Vi=2.5×107 cm/s), low adiabat implosion (α=0.7) Driver laser intensity 100kJ fuel assembly pulse

  5. FSC The slow implosion velocity leads to small Rayleigh-Taylor growth during the laser flat top Laser shuts off Bubble front thickness / target thickness Results from RT postprocessor based on Haan-Goncharov models and OMEGA laser nonuniformities with 1THz SSD.

  6. FSC A spherically convergent shock driven by a 60kJ spike in the laser intensity can ignite the hot spot of the 100kJ fuel assembly Laser Power and Intensity 60kJ 200ps shock ignitor pulse 100kJ fuel assembly pulse Energy gain = 68 (1-D LILAC simulation)

  7. FSC The laser-driven shock collides with the return shock, generating a high pressure reflected shock propagating to the hot spot Before collision After collision incoming shock high pressure shock continues to the hot spot ρ return shock ρ P P The igniter pulse drives an incoming shock, which collides with the return shock inside the shell. A high-pressure shock resulting from the collision continues to propagate to the central hot spot, leading to ignition.

  8. FSC The high pressure shock heats the hot spot above the ignition threshold Hot spot temperature Hot spot pressure With shock With shock Without shock Without shock

  9. FSC Ignition is sensitive to the launching time of the ignitor shock ~250ps • Total driver energy is kept constant at 160kJ

  10. FSC The ignitor and return shocks must be synchronized to collide in the region of peak density G=0.1 G=62 G=0.06 Implosion without ignitor shock Implosion with ignitor shock

  11. CH 2μm CH(DT)6 153μm DT ice 253μm DT gas 772μm FSC A 500kJ NIF size fuel assembly is ignited by a 200kJ ignitor shock to produce a gain of 116 Laser Power and Intensity 200kJ 690ps shock ignitor pulse

  12. 80 70 60 50 1.5 40 30 20 1 10 Amplitude (m) 0 0.5 1 1.5 2 2.5 3 0.5 FSC Mode number 0 5 10 15 20 Preliminary work on the effect of ice surface roughness shows encouraging results with respect to design robustness Gain RMS Multimode l=2-24, RMS=1-3m

  13. FSC 2-D simulations including laser nonuniformities yield good shell integrity at the end of the acceleration phase Modes l=4-100, DPP+DPR, 1THz SSD

  14. FSC The bubble front penetration is only a small fraction of the shell thickness at the end of the acceleration phase when the ignitor shock is launched. R r 13g/cc 5.5g/cc Z  r- view R-Z view

  15. FSC Summery/Conclusions High density/areal density fuel may be ignited with a spherically convergent shock driven by a laser intensity spike • High density/areal density fuel can be assembled through low velocity, low adiabat implosions. • 1-D simulations show that such a fuel assembly can be ignited by a spherically convergent shock. • Two designs are presented with 100kJ and 500kJ fuel assemblies ignited by a 60kJ and 200kJ shock respectively. • 2-D simulations are being performed to evaluate the target robustness to inner surface roughness and laser imprinting.

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