Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

Journal Article · Sat Jan 01 00:00:00 EST 2000 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.873802· OSTI ID:20217793

Knauer, J P ^[1]; Betti, R ^[1]; Bradley, D K ^[1]; Boehly, T R ^[1]; Collins, T J. B. ^[1]; Goncharov, V N ^[1]; McKenty, P W ^[1]; Meyerhofer, D D ^[1]; Smalyuk, V A ^[1]; Verdon, C P ^[2]

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1. Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)
2. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5x10{sup 14} W/cm{sup 2}. Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 {mu}m diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 {mu}m wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile. (c) 2000 American Institute of Physics.

• OSTI ID: 20217793
• Journal Information: Physics of Plasmas, Vol. 7, Issue 1; Other Information: PBD: Jan 2000; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
RAYLEIGH-TAYLOR INSTABILITY
OMEGA FACILITY
PLASMA DIAGNOSTICS
TWO-DIMENSIONAL CALCULATIONS
PLASMA SIMULATION
LASER TARGETS
LASER-PRODUCED PLASMA
THEORETICAL DATA