Improved gas-filled hohlraum performance on Nova with beam smoothing

Kauffman, R. L.; Powers, L. V.; Dixit, S. N.; Glendinning, S. G.; Glenzer, S. H.; Kirkwood, R. K.; Landen, O. L.; MacGowan, B. J.; Moody, J. D.; Orzechowski, T. J.; Pennington, D. M.; Stone, G.; Suter, L. J.; Turner, R. E.; Weiland, Timothy L.; Richard, A.; Blain, M. A.

doi:10.1063/1.872822

Cited by 33 publications

(23 citation statements)

References 23 publications

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“…From the images we infer ≈ 1 mm of axial Au wall motion by the end of the pulse and a characteristic two-lobed emission profile attribuited to the high density Au region near the wall and due to the colliding Au-gas front, in agreement with simulations [38]. These results extend our validation of modeling of the Au wall tamping by a low Z fill to longer pulses, validation begun on Nova gas-filled hohlraums [39,40].…”

Section: Gas-filled Hohlraumssupporting

confidence: 78%

The first experiments on the national ignition facility

Landen¹,

Glenzer²,

Froula³

et al. 2006

J. Phys. IV France

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Section: Gas-filled Hohlraumssupporting

confidence: 78%

The first experiments on the national ignition facility

Landen¹,

Glenzer²,

Froula³

et al. 2006

J. Phys. IV France

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“…SBS occurs when the beam reaches the high-Z Au plasma of the hohlraum wall and is scattered back, but will not retrace the incoming path, resulting in a spatial shift of the SBS signal as observed with the NBI detector. This interpretation is consistent with so-called spot motion experiments 18,33 and with calculations 34 for unsmoothed laser beams. The experiments described by Delamater et al 18 and Kauffman et al 33 show a deflection of laser beams toward the LEHs, which was greatly reduced when beam-smoothing techniques were applied.…”

Section: Hohlraum Energetics With Smooth Laser Beamssupporting

confidence: 76%

“…This interpretation is consistent with so-called spot motion experiments 18,33 and with calculations 34 for unsmoothed laser beams. The experiments described by Delamater et al 18 and Kauffman et al 33 show a deflection of laser beams toward the LEHs, which was greatly reduced when beam-smoothing techniques were applied. The calculations by Hinkel et al 34 show a deflection of unsmoothed laser beams by about 6¡ for parameters similar to those in this study.…”

Section: Hohlraum Energetics With Smooth Laser Beamssupporting

confidence: 76%

ICF quarterly report October-December 1998 volume 8, number 1

Feit¹

1998

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“…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. Moreover, the capability to align the interaction beam along the hohlraum axis allowed us to reach significantly larger scale lengths than previous gas-filled hohlraum experiments [27] with the added benefits of accurate Thomson-scattering characterization and direct transmission measurements. The plasma conditions in the center of the hohlraum have been measured with 4ω Thomson scattering.…”

Section: Introductionmentioning

confidence: 94%

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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Improved gas-filled hohlraum performance on Nova with beam smoothing

Cited by 33 publications

References 23 publications

The first experiments on the national ignition facility

The first experiments on the national ignition facility

ICF quarterly report October-December 1998 volume 8, number 1

0.351 micron Laser Beam propagation in High-temperature Plasmas

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