Monochromatic 8.05-keV Flash Radiography of Imploded Cone-in-Shell Targets

Transcription

1 Monochromatic 8.5-keV Flash Radiography of Imploded Cone-in-Shell Targets y position (nm) y position (nm) undriven 66393, 3.75 ns 66383, 3.82 ns Au Al 66391, 3.93 ns 66386, 4.5 ns 66389, 4.15 ns Optical density x position (nm) x position (nm) x position (nm) W. Theobald University of Rochester Laboratory for Laser Energetics 54th Annual Meeting of the American Physical Society Division of Plasma Physics Providence, RI 29 October 2 November 212

2 Summary High-quality radiographic images of imploding cone-inshell targets were taken close to peak compression Cu K a backlighting with OMEGA EP and monochromatic imaging provides high spatial resolution (~1 nm) and high time resolution (~12 ps) The time of the peak areal density was measured and is in good agreement with 2-D DRACO simulations The optical density of the compressed CH was measured at 8.5 kev for various times during the implosion A peak areal density of >3 mg/cm 2 is inferred from the measurement E2165

3 Collaborators A. A. Solodov, C. Stoeckl, R. Epstein, V. Yu. Glebov, G. Fiksel, S. Ivancic, F. J. Marshall, G. McKiernan, C. Mileham, P. M. Nilson, and T. C. Sangster University of Rochester Laboratory for Laser Energetics and Fusion Science Center L. C. Jarrott and F. N. Beg University of California, San Diego E. Giraldez, R. B. Stephens, and M. S. Wei General Atomics H. McLean Lawrence Livermore National Laboratory H. Sawada University of Nevada, Reno J. Santos Centre Lasers Intenses et Applications University of Bordeaux, France

4 Motivation OMEGA fast-ignition experiments with Au cone-in-shell targets measured 3.5% coupling efficiency 1 Neutron yield ( 1 7 ) nm tip 4-nm tip OMEGA EP arrival time (ns) 1-ps, 1-kJ short pulses E2166 Integrated DRACO 2 LSP 3 simulations show that most of the fast electrons are lost in the gold cone A lower-z material promises better fast-electron transport and enhanced coupling 1 W. Theobald et al., Phys. Plasmas 18, 5635 (211). 2 P. B. Radha et al., Phys. Plasmas 12, 5637 (25). 3 D. R. Welch et al., Phys. Plasmas 13, 6315 (26).

5 Hydrodynamic simulations of an aluminum tip cone-inshell target were performed with DRACO* r (nm) 5 Shock breakout at At 3.25 ns, before 3.87 ns, ~.19 ns before Detail of cone tip peak compression peak compression t(g/cm 3 ) 3 t(g/cm 3 ) t(g/cm 3 ) Au Al z (nm) z (nm) z (nm) The target design promises a better shock resilience (~8-ps later breakout) than the previous Au tip target E2168 * P. B. Radha et al., Phys. Plasmas 12, 5637 (25); A. A. Solodov, BO4.15, this conference.

6 Flash radiography combined with monochromatic imaging was used to image the fuel assembly OMEGA EP 1 ps 1.4 kj Cu foil 1 1 mm 25 nm 2 mm Al foil mm 5 nm 1 mm 54 OMEGA beams, 18 kj, 2.7 ns Crystal imager E2169

7 A high-quality spherical crystal x-ray imager for OMEGA* provides high resolution images for various experiments High-intensity laser pulse Backlighter Top view not to scale Object Bragg angle (i B ) Spherically bent crystal Detector Rowland circle Cu K a1 line emission: 8.48 kev (1.541 Å) Monochromatic imaging (DE ~ 6 ev, at 8.5 kev) High spatial resolution: ~1 nm Large light-collection area ~f/1 E18857c *C. Stoeckl et al., Rev. Sci. Instrum. 83, 1E51 (212).

8 The K a flash lasts for 12 ps 1. Measured.8 Signal ps Fit Time (ps) 8 12 Time-resolved K a x-ray emission from a Cu foil target irradiated with a ~1 kj, 1-ps pulse.* E2161 * P. M. Nilson et al., Phys. Rev. Lett. 18, 852 (212). P. M. Nilson, JO5.1, this conference.

9 Radiographic images of imploding cone-in-shell targets were taken at various times around peak compression y position (nm) y position (nm) undriven 66393, 3.75 ns 66383, 3.82 ns Au Al 66391, 3.93 ns 66386, 4.5 ns 66389, 4.15 ns Optical density x position (nm) x position (nm) x position (nm) E21611 The predicted time of peak compression from 2-D DRACO simulations is at 4.1 ns

10 The areal density of the compressed core can be extracted from the measured optical densities y position (nm) ns Optical density Optical density nm x position (nm) y position (nm) Average mass absorption coefficient (n) of CD plasma from PrismSPECT* n = # n^rht^rhdr # t^rhdr tr. ln^ I / Ih _ 2 / n i E21612 *J. J. MacFarlane, Prism Computational Sciences, Inc., Madison, WI

11 The measured peak areal density exceeds 3 mg/cm 2 tr (mg/cm 2 ) D DRACO simulations* Experiments Time (ns) 4.2 E21613 * A. A. Solodov, BO4.15, this conference.

12 Summary/Conclusions High-quality radiographic images of imploding cone-inshell targets were taken close to peak compression Cu K a backlighting with OMEGA EP and monochromatic imaging provides high spatial resolution (~1 nm) and high time resolution (~12 ps) The time of the peak areal density was measured and is in good agreement with 2-D DRACO simulations The optical density of the compressed CH was measured at 8.5 kev for various times during the implosion A peak areal density of >3 mg/cm 2 is inferred from the measurement E2165