High-Intensity Shock-Ignition Experiments in Planar Geometry

Transcription

1 High-Intensity Shock-Ignition Experiments in Planar Geometry Low intensity High intensity 4 nm CH 3 nm Mo 138 nm quartz VISAR SOP Simulated peak pressure (Mbar) 1 5 Laser backscatter 17.5 kev Mo K a Hard x rays Spike intensity ( 1 15 W/cm 2 ) W. Theobald University of Rochester Laboratory for Laser Energetics 53rd Annual Meeting of the American Physical Society Division of Plasma Physics Salt Lake City, UT November 211

2 Summary 1-Mbar shocks are generated by an ~ W/cm 2 spike pulse in a long-scale-length plasma Shock ignition requires ~1 s of Mbar of pressure and hot-electron temperature K15 kev Hot-electron temperatures up to 7 kev were measured at W/cm 2 ~2% of the spike beam energy is converted into hot electrons and up to ~7% of the laser energy is backscattered 2-D DRACO simulations reproduce the shock dynamics well over a range of spike intensities First demonstration of a 1-Mbar laser-driven shock at shock-ignition relevant conditions. E2448

3 Collaborators M. Hohenberger 1, S. X. Hu 1, K. S. Anderson 1, R. Betti 1,2, T. R. Boehly 1, A. Casner 3, D. H. Edgell 1, D. E. Fratanduono 4, M. Lafon 5, D. D. Meyerhofer 1,2, R. Nora 1,2, X. Ribeyre 5, T. C. Sangster 1, G. Schurtz 5, W. Seka 1, C. Stoeckl 1, and B. Yaakobi 1 1 Laboratory for Laser Energetics and Fusion Science Center, Rochester NY 2 Depts. of Mech. Eng. and Physics at the University of Rochester, Rochester NY 3 CEA, DAM, DIF, Arpajon, France 4 Lawrence Livermore National Laboratory, Livermore, CA 5 Centre Lasers Intenses et Applications, University of Bordeaux Bordeaux, France

4 Shock ignition uses a non-isobaric fuel assembly and promises lower laser energy for achieving ignition* 4 Ignitor spike ~ W/cm 2 Return shock Power (TW) Standard pulse Assembly 5 1 Spike shock wave Critical issues for shock ignition demonstrate hot-electron temperatures of 15 kev generated by spike demonstrate ~3- to 4-Mbar spike-generated pressure TC8918b R. Betti et al., Phys. Rev. Lett. 98, 1551 (27).

5 A laser plasma interaction experiment was performed in planar geometry with overlapping beams Low intensity High intensity Laser backscatter 4 nm CH 17.5 kev Mo K a 3 nm Mo Hard x rays 138 nm quartz VISAR SOP Peak intensity ( 1 14 ) W/cm Cone 1 Cone 2 Cone Phase plates and DPR s with ~9 nm focal spots were used in plasma-generating beams (cone 2 and cone 3) Phase plates with an ~6-nm focal spot were used in six high-intensity beams (cone 1) E2455

6 The number of hot electrons and T hot increase with spike laser intensity Conversion efficiency (%) E hot from measured Mo K a yield and Monte Carlo simulations of electron stopping 1 T hot from measurement with time-resolved four-channel hard x-ray detector Hot-electron energy (J) Spike intensity ( 1 15 W/cm 2 ) Spike intensity ( 1 15 W/cm 2 ) T hot (kev) E B. Yaakobi et al., Phys. Plasmas 16, 1273 (29). 2 C. Stoeckl et al., Rev. Sci. Instrum. 72, 1197 (21).

7 The backscattered laser energy increases with spike laser intensity 1 Backscatter (%) Spike intensity ( 1 15 W/cm 2 ) Only the backscattered energy (SRS + SBS) in the lens was quantified E245 Sidescattering was observed, but not quantified

8 The shock propagation in quartz was observed with streaked optical pyrometry and VISAR* Intensity ( 1 14 W/cm 2 ) y (nm) y (nm) E SOP Laser VISAR Shock velocity (nm/ns) Temperature (ev) *J. E. Miller et al., Rev. Sci. Instrum. 78, 3493 (27). P. M. Celliers et al., Rev. Sci. Instrum. 75, 4916 (24).

9 2-D DRACO simulations show a spherical, decaying shock generated by the high-intensity spike Quartz Mo CH Laser ns Pressure (Mbar) Breakout into quartz and catch up of spike shock y (nm) y (nm) 2 VISAR x (nm) E2452

10 Both the shock breakout into the quartz layer and the rear are reproduced well in the simulations Quartz Mo CH Laser ns Pressure (Mbar) Breakout at rear y (nm) y (nm) 2 VISAR x (nm) E2452a

11 2-D DRACO simulations reproduce well the shock dynamics over a range of spike intensities 9 Experiment DRACO simulations Breakout (ns) Spike intensity ( 1 15 W/cm 2 ) The agreement of measured and simulated shock-breakout times is better than 6%. E2453

12 The excellent agreement between experiment and simulations gives confidence in the simulated peak pressure Shock position in quartz (nm) Simulation Experiment Simulated peak pressure (Mbar) Spike intensity ( 1 15 W/cm 2 ) E251

13 2-D hydrodynamic DRACO simulations predict an initial plasma pressure of 1 Mbar for ~ W/cm 2 Position (nm) CH Mo SiO Breakout into SiO 2 Electron temperature T e (ev) 5 1 Breakout rear Pressure P (Mbar) Spike E2454

14 Summary/Conclusions 1-Mbar shocks are generated by an ~ W/cm 2 spike pulse in a long-scale-length plasma Shock ignition requires ~1 s of Mbar of pressure and hot-electron temperature K15 kev Hot-electron temperatures up to 7 kev were measured at W/cm 2 ~2% of the spike beam energy is converted into hot electrons and up to ~7% of the laser energy is backscattered 2-D DRACO simulations reproduce the shock dynamics well over a range of spike intensities First demonstration of a 1-Mbar laser-driven shock at shock-ignition relevant conditions. E2448