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Super-penetration Experiment using Ultra-intense Lasers

Super-penetration Experiment using Ultra-intense Lasers. K. A. Tanaka 1,2 , H. Habara, T. Matsuoka 1,* A. Lei 1** , Y. Sentoku 2 , T. Tanimoto 1,2 , T. Yabuuchi 1 , J. Zheng 1,*** , R. Kodama 1 , N. Miyanaga 1 , T. Norimatsu 1 , K. Nagai 1 , K. Mima.

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Super-penetration Experiment using Ultra-intense Lasers

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  1. Super-penetration Experiment using Ultra-intense Lasers K. A. Tanaka1,2, H. Habara, T. Matsuoka1,* A. Lei1**, Y. Sentoku2, T. Tanimoto1,2, T. Yabuuchi1, J. Zheng1,***, R. Kodama1, N. Miyanaga1, T. Norimatsu1, K. Nagai1, K. Mima 1:Institute of Laser, Engineering, Osaka U. 2-6 565-0871, Japan 2:Department of Electronic, Information Systems and Energy Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan 3: University of Nevada, Reno, Department of Physics, NTF-MS372, 5625 Fox Ave., Reno, NV 89506, USA • Present address : Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109-2099 • ** Institute of Optics and Fine Mechanics, Shanghai PRC • ** Present address : Department of Modern Physics,University of Science and Technology of China, Hefei, Anhui 230037, P. R. China. Fast Ignition Workshop June 16, 2008 Crete Greece

  2. For efficient heating of dense core, heating beam is required to reach core as close as possible. Symmetrical illumination ns time scale Compressed plasma Plastic shell Dense plasma core laser Heating ps time scale Hot spark Large scale plasma Concept of fast ignitor in inertial fusion energy

  3. Contents • Physical background of super penetration • Experiments of 20 TW laser • Experiments of PW laser • 3D-PIC simulation of super-penetration • Summary

  4. Higher intensity allows propagation into denser plasma. Relativistic induced transparency (RIT) Electron density [/cm3] Critical density

  5. What is “Super-penetration”? Focus position RIT&RSF Laser Overdense plasma d : Self-focusing distance Relativistic self-focusing + Relativistic induced transparency (RSF) (RIT) Super-penetration

  6. Experiments of 20 TW laser. GEKKO Module 2 (GMII) Glass Laser System. 20 TW laser Wavelength : 1.053 mm Energy : 6.9 ~ 9.6 J Pulse duration : 600 fs Focused intensity: 2.0 ~ 2.8 X 1018 W/cm2 Long pulse laser Wavelength : 1.053 mm Energy : ~20 J Pulse duration : 400 ps

  7. GEKKO Module II (GMII) laser system was used for experiment. Target CD foil : 0.25, 0.6, 1 mm with coating of Al 0.1 mm t 20 TW laser l = 1.053 mm E = 6.9 ~ 9.6 J t = 600 fs Incidence angle : 20° I = 2.0 ~ 2.8 X 1018 W/cm2

  8. Preformed plasma is formed by long pulse laser before incidence of UIL. Density obtained by Hydrodynamics Simulation (ILESTA-1D)

  9. Plasma channels move back and forth by changing focus position of laser. UIL d=196 mm d=106 mm d=289 mm

  10. Laser Laser Self focused channel is observed at d = 289 mm. d=106 mm d=196 mm d=289 mm Observation point Observation point

  11. Transmittance sensitively depends on focus point and maximum electron density. Super-penetration Thickness 0.6 mm d = 200 mm

  12. Experiments of PW laser. GEKKO XII laser Wavelength : 0.527 mm Energy : ~6 k J/12 beams Pulse duration : 1 ns PW Laser Wavelength : 1.053 mm Energy : 150~250 J Pulse duration : 600 fs

  13. Super-penetration of PW laser into thick overdense pre-plasma Target : CD foil 1 mmt with coating of Al 0.1 mm t 40~48 J

  14. X-ray image shows a plasma channel formation. PW+GXII GXII Laser PW E=150 J I=5x1018 W/cm2 d = 20 mm GXII E=44 J I=1.7x1013 W/cm2

  15. X-ray image indicates 0.25PW laser penetration into thick over- dense preplasma due to self focusing. PW: E=150 J I=5x1018 W/cm2 Preplasma: peak density=10Nc thickness= 80mm

  16. Optical image shows close correlation of PW laser energy transmittance values to the PW laser focus positions 3.8% transmittance for d = 20 mm density of 0.86Nc 6*10-5 transmittance for d = ? mm density of 0.6Nc Density will be deleted, when d is written!

  17. 3D-PIC simulation of super-penetration Input laser Peak power : 20 TW Peak intensity : 6.3X1020 W/cm2 Initial beam dia. 2 mm (FWHM) Rayleigh length (pr2/l ~ 3.14 mm)

  18. Two penetration phases are observed in 3D-PIC.

  19. Hole boring is dominant in high density region. Eq. (1) : Relativistic effect with damping of the laser

  20. Summary • Transmittance of the laser is sensitive to focus position of the laser due to self-focusing (Super-penetration). • Simple model based on mode dispersion gives upper limit density for RIT at around 20-30 Nc. • The upper limit for transmission is given by relativistic critical density. • PW laser super-penetration showed 150 J is used within 0.6 • psec. to penetrate through 5 Nc (average) plasma densityfor ~100 mm. • Simple estimate is that 1. 5 kJ ~ 3 kJ is needed for 1 mm scale plasma up to 10 Nc. to create a relativistic self-focusing channel. • For example, LFEX delivers 10 kJ and 10 – 3= 7 kJ can be used for heating.s

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