Measurements of laser-imprinted perturbations and Rayleigh--Taylor growth with the Nike KrF laser

Journal Article · Thu May 01 04:00:00 EDT 1997 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.872560· OSTI ID:560656

Pawley, C J; Gerber, K; Lehmberg, R H; McLean, E A; Mostovych, A N; Obenschain, S P; Sethian, J D; Serlin, V; Stamper, J A; Sullivan, C A; Bodner, S E; Colombant, D; Dahlburg, J P; Schmitt, A J ^[1]; Gardner, J H ^[2]; Brown, C; Seely, J F ^[3]; Lehecka, T; Aglitskiy, Y; Deniz, A V ; Chan, Y; Metzler, N ^[4]; Klapisch, M ^[5]

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1. Code 6730, Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States)
2. Laboratory for Computational Physics, Naval Research Laboratory, Washington, D.C. 20375 (United States)
3. Space Science Division, Naval Research Laboratory, Washington, D.C. 20375 (United States)
4. Science Applications International Corporation, McLean, Virginia 22310 (United States)
5. Artep Incorporated, Columbia, Maryland 21045 (United States)

Nike is a 56 beam Krypton Fluoride (KrF) laser system using Induced Spatial Incoherence (ISI) beam smoothing with a measured focal nonuniformity {l_angle}{Delta}I/I{r_angle} of 1{percent} rms in a single beam [S. Obenschain {ital et al.}, Phys. Plasmas {bold 3}, 1996 (2098)]. When 37 of these beams are overlapped on the target, we estimate that the beam nonuniformity is reduced by {radical}(37), to ({Delta}I/I){congruent}0.15{percent} (excluding short-wavelength beam-to-beam interference). The extraordinary uniformity of the laser drive, along with a newly developed x-ray framing diagnostic, has provided a unique facility for the accurate measurements of Rayleigh--Taylor amplified laser-imprinted mass perturbations under conditions relevant to direct-drive laser fusion. Data from targets with smooth surfaces as well as those with impressed sine wave perturbations agree with our two-dimensional (2-D) radiation hydrodynamics code that includes the time-dependent ISI beam modulations. A 2-D simulation of a target with a 100 {Angstrom}rms randomly rough surface finish driven by a completely uniform beam gives final perturbation amplitudes similar to the experimental data for the smoothest laser profile. These results are promising for direct-drive laser fusion.

• OSTI ID: 560656
• Report Number(s): CONF-961102--
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 5 Vol. 4; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ABLATION
COMPUTERIZED SIMULATION
DIRECT DRIVE LASER IMPLOSION
HEATING
INSTABILITY GROWTH RATES
KRYPTON COMPOUNDS
KRYPTON FLUORIDE LASERS
LASER TARGETS
LIGHT TRANSMISSION
PLASMA DIAGNOSTICS
PLASMA SIMULATION
RAYLEIGH-TAYLOR INSTABILITY
SPATIAL DISTRIBUTION
THERMONUCLEAR IGNITION