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Crossed-beam energy transfer in direct-drive implosions

Description: Direct-drive-implosion experiments on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have showed discrepancies between simulations of the scattered (non-absorbed) light levels and measured ones that indicate the presence of a mechanism that reduces laser coupling efficiency by 10%-20%. This appears to be due to crossed-beam energy transfer (CBET) that involves electromagnetic-seeded, low-gain stimulated Brillouin scattering. CBET scatters energy from the central portion of … more
Date: May 22, 2012
Creator: Seka, W.; Edgell, D. H.; Michel, D. T.; Froula, D. H.; Goncharov, V. N.; Craxton, R. S. et al.
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Partner: UNT Libraries Government Documents Department
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Comparison of Raman Scattering Measurements and Modeling in NIF Ignition Experiments

Description: Recent NIF indirect-drive experiments have shown significant Raman scattering from the inner beams. NIF data has motivated improvements to rad-hydro modeling, leading to the 'high flux model' [M. D. Rosen et al., HEDP 7, 180 (2011)]. Cross-beam energy transfer [P. A. Michel et al., Phys. Plasmas 17, 056305 (2010] in the laser entrance hole is an important tool for achieving round implosions, and is uniformly distributed across the laser spot in rad-hydro simulations (but not necessarily in expe… more
Date: November 4, 2011
Creator: Strozzi, D. J.; Hinkel, D. E.; Williams, E. A.; Town, R. J.; Michel, P. A.; Divol, L. et al.
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Partner: UNT Libraries Government Documents Department
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Hohlraum Designs for High Velocity Implosions on NIF

Description: In this paper, we compare experimental shock and capsule trajectories to design calculations using the radiation-hydrodynamics code HYDRA. The measured trajectories from surrogate ignition targets are consistent with reducing the x-ray flux on the capsule by about 85%. A new method of extracting the radiation temperature as seen by the capsule from x-ray intensity and image data shows that about half of the apparent 15% flux deficit in the data with respect to the simulations can be explained b… more
Date: October 19, 2011
Creator: Meezan, N. B.; Hicks, D. G.; Callahan, D. A.; Olson, R. E.; Schneider, M. S.; Thomas, C. A. et al.
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Partner: UNT Libraries Government Documents Department
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A three wavelength scheme to optimize hohlraum coupling on the National Ignition Facility

Description: By using three tunable wavelengths on different cones of laser beams on the National Ignition Facility, numerical simulations show that the energy transfer between beams can be tuned to redistribute the energy within the cones of beams most prone to backscatter instabilities. These radiative hydrodynamics and laser-plasma interaction simulations have been tested against large scale hohlraum experiments with two tunable wavelengths, and reproduce the hohlraum energetics and symmetry. Using a thi… more
Date: December 16, 2010
Creator: Michel, P; Divol, L; Town, R & Rosen, M
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Partner: UNT Libraries Government Documents Department
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Analysis of the National Ignition Facility Ignition Hohlraum Energetics Experiments

Description: A series of forty experiments on the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] to study energy balance and implosion symmetry in reduced- and full-scale ignition hohlraums was shot at energies up to 1.3 MJ. This paper reports the findings of the analysis of the ensemble of experimental data obtained that has produced an improved model for simulating ignition hohlraums. Last year the first observation in a NIF hohlraum of energy transfer between cones… more
Date: November 22, 2010
Creator: Town, R. J.; Rosen, M. D.; Michel, P. A.; Divol, L.; Moody, J. D.; Kyrala, G. A. et al.
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Partner: UNT Libraries Government Documents Department
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Images of the Laser Entrance Hole from the Static X-ray Imager at NIF

Description: The Static X-ray Imager (SXI) at the National Ignition Facility (NIF) is a pinhole camera using a CCD detector to obtain images of hohlraum wall x-ray drive illumination patterns seen through the laser entrance hole (LEH). Carefully chosen filters combined with the CCD response allows recording images in the x-ray range of 3 to 5 keV with 60 {micro}m spatial resolution. The routines used to obtain the apparent size of the backlit LEH, and the location and intensity of beam spots are discussed a… more
Date: May 4, 2010
Creator: Schneider, M; Jones, O; Meezan, N; Milovich, J; Town, R; Alvarez, S et al.
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Partner: UNT Libraries Government Documents Department
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National Ignition Campaign Hohlraum Energetics

Description: The first series of experiments on the National Ignition Facility (NIF) [E. I. Moses, R. N. Boyd, B. A. Remington, C. J. Keane, and R. Al-Ayat, 'The National Ignition Facility: ushering in a new age for high energy density science,' Phys. Plasmas 16, 041006 (2009)] tested ignition hohlraum 'energetics,' a term described by four broad goals: (1) Measurement of laser absorption by the hohlraum; (2) Measurement of the x-ray radiation flux (T{sub RAD}{sup 4}) on the surrogate ignition capsule; (3) … more
Date: November 16, 2009
Creator: Meezan, N B; Atherton, L J; Callahan, D A; Dewald, E L; Dixit, S N; Dzenitis, E G et al.
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Partner: UNT Libraries Government Documents Department
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PREPARATIONS FOR ASSEMBLY OF THE INTERNATIONAL ERL CRYOMODULE AT DARESBURY LABORATORY

Description: The collaborative development of an optimised cavity/cryomodule solution for application on ERL facilities has now progressed to final assembly and testing of the cavity string components and their subsequent cryomodule integration. This paper outlines the verification of the various cryomodule sub-components and details the processes utilised forfinal cavity string integration. The paper also describes the modifications needed to facilitate this new cryomodule installation and ultimate operati… more
Date: April 29, 2009
Creator: McIntosh, P. A.; Bate, R.; Beard, C. D.; Cordwell, M. A.; Dykes, D. M.; Pattalwar, S. M. et al.
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Partner: UNT Libraries Government Documents Department
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0.351 micron Laser Beam propagation in High-temperature Plasmas

Description: A study of the laser-plasma interaction processes have been performed in plasmas that are created to emulate the plasma conditions in indirect drive inertial confinement fusion targets. The plasma emulator is produced in a gas-filled hohlraum; a blue 351-nm laser beam propagates along the axis of the hohlraum interacting with a high-temperature (T{sub e} = 3.5 keV), dense (n{sub e} = 5 x 10{sup 20}cm{sup -3}), long-scale length (L {approx} 2 mm) plasma. Experiments at these conditions have demo… more
Date: December 10, 2007
Creator: Froula, D.; Divol, L.; Meezan, N.; Ross, J.; Berger, R. L.; Michel, P. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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