Implementation of a high energy 4ω probe beam on the Omega laser

Mackinnon, A. J.; Shiromizu, S. J.; Antonini, Giulio; Auerbach, Jerome M.; Haney, K.; Froula, D. H.; Moody, J. D.; Gregori, G.; Constantin, C.; Sorce, C.; Divol, L.; Griffith, R. L.; Glenzer, S. H.; Satariano, J.; Whitman, P. K.; Locke, Susan N.; Miller, Eric L.; Huff, R.; Thorp, K.; Armstrong, William D.; Bahr, R.; Seka, W.; Pien, G.; Mathers, J. E.; Morse, Samuel Finley Breese; Loucks, S. J.; Stagnitto, S.

doi:10.1063/1.1789247

Cited by 41 publications

(26 citation statements)

References 6 publications

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“…This new target platform together with recently commissioned suite of laser-plasma interaction diagnostics [7,8] allows the access to high temperature, long scale length conditions not previously available using gasbag [9,10], toroidal hohlraum [11,12], or gas-filled hohlraum targets. Laser-plasma interaction thresholds are sensitive to the electron temperature and the length of the density plateau in a plasma; electron temperatures in open geometry gasbag plasmas with roughly the same plasma conditions are significantly lower than the target platform presented while scale lengths were much shorter in previous hohlraum platforms.…”

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Ideal Laser-Beam Propagation through High-Temperature Ignition Hohlraum Plasmas

et al. 2007

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Ideal Laser-Beam Propagation through High-Temperature Ignition Hohlraum Plasmas

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“…The beam configuration in this set of experiments, also shown in Fig. 1 with a schematic of the Thomson scattering setup, [10] was somewhat different ( the SBS spectral shifts listed in Table I and the hydrodynamic simulations indicate that the electron temperature is weakly dependent on the a The 527 nm interaction beam energy was about 1/3 of the other shots.…”

Section: Experiments Descriptionmentioning

confidence: 99%

Laser light backscatter from intermediate and high Z plasmas

et al. 2006

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In experiments at the Omega Laser Facility, stimulated Brillouin backscatter (SBS) from gasbags filled with Krypton and Xenon gases was unexpectedly 10 times lower than from CO 2 -filled gasbags with similar electron densities. The SBS backscatter was a 1-5 % for both 527nm and 351nm interaction beams at an intensity of ∼ 10 15 W/cm 2 . The SRS backscatter was less than 1%. The 351nm interaction beam is below the threshold for filamentation and all the SBS occurs in the density plateau between the blast waves. Inverse bremsstrahlung absorption of the incident and SBS light account for the lower reflectivity from Kr than from CO 2 . The 527nm interaction beam filaments in the blowoff plasma before the beam propagates through the blast wave where it is strongly absorbed. Thus, most of the 527nm SBS occurs in the flowing plasma outside the blast waves. Nonlinear processes that limit the acoustic wave amplitudes to 1% of electron density model the SBS reflectivity well in both CO 2 and Krypton plasmas . * Electronic address: berger5@llnl.gov

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“…This new target platform together with recently commissioned suite of laser-plasma interaction diagnostics [16,17] allows the access to high temperature, long scale length conditions not previously available using gasbag [19,24], toroidal hohlraum [25,26], or gas-filled hohlraum targets. Laser-plasma interaction thresholds are sensitive to the electron temperature and the length of the density plateau in a plasma; electron temperatures in open geometry gasbag plasmas with roughly the same plasma scale-lengths are significantly lower than in the present hohlraum targets because of a factor of 10 larger energy density in hohlraums.…”

Section: Introductionmentioning

confidence: 99%

“…The plasma conditions in the center of the hohlraum have been measured with 4ω Thomson scattering. One of the 3ω beams (beam 25) has been de-tuned to produce 2ω light and directed to a dedicated port (P9) and subsequently doubled to provide a 4ω Thomson-scattering probe laser [14,16,28]. Typical 4ω probe beam energies of E=200 J with a flat 1 ns pulse duration have been employed with a small focal spot of 60 µm at the Thomson-scattering volume.…”

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confidence: 99%

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0.351 micron Laser Beam propagation in High-temperature Plasmas

Froula¹,

Divol²,

Meezan³

et al. 2007

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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 (Te = 3.5 keV), dense (ne = 5 × 10 20 cm −3 ), long-scale length (L ∼ 2 mm) plasma. Experiments at these conditions have demonstrated that the interaction beam produces less than 1% total backscatter resulting in transmission greater than 90% for laser intensities less than I < 2 × 10 15 W-cm −2 . The bulk plasma conditions have been independently characterized using Thomson scattering where the peak electron temperatures are shown to scale with the hohlraum heater beam energy in the range from 2 keV to 3.5 keV. This feature has allowed us to determine the thresholds for both backscattering and filamentation instabilities; the former measured with absolutely calibrated full aperture backscatter and near backscatter diagnostics and the latter with a transmitted beam diagnostics. A plasma length scaling is also investigated extending our measurements to 4-mm long high-temperature plasmas. At intensities I < 5 × 10 14 W-cm −2 , greater than 80% of the energy in the laser is transmitted through a 5-mm long, high-temperature (Te > 2.5 keV) high-density (ne = 5 × 10 20 W-cm −3 ) plasma. Comparing the experimental results with detailed gain calculations for the onset of significant laser scattering processes shows a stimulated Brillouin scattering threshold (R=10%) for a linear gain of 15; these high temperature, low density experiments produce plasma conditions comparable to those along the outer beams in ignition hohlraum designs. By increasing the gas fill density (ne = 10 21 cm −3 ) in these targets, the inner beam ignition hohlraum conditions are accessed. In this case, stimulated Raman scattering dominates the backscattering processes and we show that scattering is small for gains less than 20 which can be achieved through proper choice of the laser beam intensity. The first three-dimensional (3D) simulations of a high power 0.351µm laser beam propagating through a high-temperature hohlraum plasma are also reported. We show that 3D linear kinetic modeling of Stimulated Brillouin scattering reproduces quantitatively the experimental measurements, provided it is coupled to detailed hydrodynamics simulation and a realistic description of the laser beam from its millimeter-size envelop down to the micron scale speckles. These simulations accurately predict the strong reduction of SBS measured when polarization smoothing is used.

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Implementation of a high energy 4ω probe beam on the Omega laser

Cited by 41 publications

References 6 publications

Ideal Laser-Beam Propagation through High-Temperature Ignition Hohlraum Plasmas

Ideal Laser-Beam Propagation through High-Temperature Ignition Hohlraum Plasmas

Laser light backscatter from intermediate and high Z plasmas

0.351 micron Laser Beam propagation in High-temperature Plasmas

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