Time-resolved absorption in cryogenic and room-temperature direct-drive implosionsa)

Time-dependent and time-integrated absorption fractions are inferred from scattered-light measurements in room-temperature and cryogenic direct-drive-implosion experiments on OMEGA. The measurements agree reasonably well with hydrodynamic simulations that include nonlocal electron-heat transport. Discrepancies in the time-resolved scattered-light spectra between simulations and experiments remain for complex laser pulse shapes, indicating beam-to-beam energy transfer and commensurate coupling losses. Time-resolved scattered-light spectra near ω∕2 and 3ω∕2 as well as time-resolved hard-x-ray measurements indicate the presence of a strongly driven two-plasmon-decay (TPD) instability at high intensities that may influence the observed laser light absorption. Experiments indicate that energetic electron production due to the TPD instability can be mitigated with high-Z-doped plastic shells.

[1]  Kunioki Mima,et al.  Random Phasing of High-Power Lasers for Uniform Target Acceleration and Plasma-Instability Suppression , 1984 .

[2]  D. Meyerhofer,et al.  Multibeam stimulated brillouin scattering from hot, solid-target plasmas. , 2002, Physical review letters.

[3]  Ying Lin,et al.  Laser phase conversion using continuous distributed phase plates , 1997, Other Conferences.

[4]  P. B. Radha,et al.  Progress in hydrodynamics theory and experiments for direct-drive and fast ignition inertial confinement fusion , 2006 .

[5]  R. Craxton,et al.  Nonlinear laser–matter interaction processes in long‐scale‐length plasmas , 1992 .

[6]  R. Fabbro,et al.  Experimental results and theoretical analysis of the effect of wavelength on absorption and hot‐electron generation in laser‐plasma interaction , 1985 .

[7]  R. Craxton,et al.  Production and characterization of hot, long‐scale‐length laser plasmas , 1992 .

[8]  P E Young,et al.  Observation of saturation of energy transfer between copropagating beams in a flowing plasma. , 2002, Physical review letters.

[9]  R. Mccrory.  Laboratory for Laser Energetics annual report, 1 October 1991--30 September 1992 , 1993 .

[10]  R. S. Craxton,et al.  Three-Dimensional Characterization of Cryogenic Target Ice Layers Using Multiple Shadowgraph Views , 2006 .

[11]  M. H. Key,et al.  The Physics of Laser Plasma Interactions , 1989 .

[12]  V. Goncharov,et al.  Performance of Direct-Drive Cryogenic Targets on OMEGA , 2007 .

[13]  T. Kessler,et al.  Laser Coherence Control: Technology and Applications , 1993 .

[14]  E. Williams,et al.  Doppler shift of laser light reflected from expanding plasmas , 1981 .

[15]  Ying Lin,et al.  Phase conversion of lasers with low-loss distributed phase plates , 1993, Photonics West - Lasers and Applications in Science and Engineering.

[16]  S. Skupsky,et al.  Modeling hydrodynamic instabilities in inertial confinement fusion targets , 2000 .

[17]  Epstein,et al.  Effect of laser illumination nonuniformity on the analysis of time-resolved x-ray measurements in uv spherical transport experiments. , 1987, Physical review. A, General physics.

[18]  Craxton,et al.  Absorption physics at 351 nm in spherical geometry. , 1985, Physical review letters.

[19]  Robert L. McCrory,et al.  Indications of strongly flux-limited electron thermal conduction in laser- target experiments , 1975 .

[20]  R. Berger,et al.  Emission of light at half‐integer harmonics of the laser frequency , 1985 .

[21]  Joshua E. Rothenberg,et al.  Polarization beam smoothing for inertial confinement fusion , 2000 .

[22]  Heinrich Hora,et al.  Laser Interaction and Related Plasma Phenomena , 2005 .

[23]  S. Skupsky,et al.  Early stage of implosion in inertial confinement fusion: Shock timing and perturbation evolution , 2006 .

[24]  W. Rozmus,et al.  The inverse bremsstrahlung absorption coefficient in collisional plasmas , 1985 .

[25]  Tadashi Sekiguchi,et al.  Plasma Physics and Controlled Nuclear Fusion Research , 1987 .

[26]  T. H. Hinterman,et al.  Forming cryogenic targets for direct-drive experimentsa) , 2006 .

[27]  Robert L. Keck,et al.  Measurements and interpretation of the absorption of 0.35 μm laser radiation on planar targets , 1982 .

[28]  S. Skupsky,et al.  Improved performance of direct-drive inertial confinement fusion target designs with adiabat shaping using an intensity picket , 2003 .

[29]  Albert Simon,et al.  On the inhomogeneous two‐plasmon instability , 1983 .

[30]  K. Rohlena,et al.  ECLIM 2000 : 26th European Conference on Laser Interaction with Matter, 12-16 June, 2000, Prague, Czech Republic , 2001 .

[31]  A. Maximov,et al.  Modeling stimulated Brillouin scattering in the underdense corona of a direct drive inertial confinement fusion target , 2004 .

[32]  Samuel A. Letzring,et al.  Improved laser‐beam uniformity using the angular dispersion of frequency‐modulated light , 1989 .

[33]  R. A. Cairns,et al.  Laser-Plasma Interactions , 2009 .

[34]  L. M. Elasky,et al.  Characterization of cryogenic direct-drive ICF targets during layering studies and just prior to shot time , 2006 .