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  • 1
    Electronic Resource
    Electronic Resource
    Erratum: "Resonant diagnostics of laser-produced Ba plasmas'' [Rev. Sci. Instrum. 59, 1497 (1988)] (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 807-807 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141091
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  • 2
    Electronic Resource
    Electronic Resource
    Resonant diagnostics of laser-produced Ba plasmas (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1497-1499 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Resonant laser probing diagnostics are used to observe laser-produced barium plasmas (n≤1015 cm−3, T(approximately-equal-to)1 eV) streaming (v(approximately-equal-to)106 cm/s) across a strong transverse magnetic field (10 kG). The interaction of the plasma with the magnetic field produces structure in the plasma. The observation of this structure requires resonant diagnostics because of the very low plasma density in this experiment. A YAG-pumped dye laser is tuned near the Ba ii 4554-A(ring) transition for resonant absorption, shadowgraphy, and scattering measurements. Resonant absorption and shadowgraphy images reveal that the plasma expands across the field with virtually no inhibition from the field, while narrowing in the plane perpendicular to the field. In the plane of the magnetic field the expansion is highly structured, taking the form of very narrow jets aligned along the field lines. This structure appears to be a manifestation of a beam-plasma-type instability. For a comparison with theoretical predictions the plasma density and scale lengths are measured by resonant scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140175
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements of laser-imprinted perturbations and Rayleigh–Taylor growth with the Nike KrF laser : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1969-1977 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nike is a 56 beam Krypton Fluoride (KrF) laser system using Induced Spatial Incoherence (ISI) beam smoothing with a measured focal nonuniformity 〈ΔI/I〉 of 1% rms in a single beam [S. Obenschain et al., Phys. Plasmas 3, 1996 (2098)]. When 37 of these beams are overlapped on the target, we estimate that the beam nonuniformity is reduced by 37, to (ΔI/I)≅0.15% (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 Å 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872560
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  • 4
    Electronic Resource
    Electronic Resource
    The Nike KrF laser facility: Performance and initial target experiments (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2098-2107 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Krypton-fluoride (KrF) lasers are of interest to laser fusion because they have both the large bandwidth capability ((approximately-greater-than)THz) desired for rapid beam smoothing and the short laser wavelength (1/4 μm) needed for good laser–target coupling. Nike is a recently completed 56-beam KrF laser and target facility at the Naval Research Laboratory. Because of its bandwidth of 1 THz FWHM (full width at half-maximum), Nike produces more uniform focal distributions than any other high-energy ultraviolet laser. Nike was designed to study the hydrodynamic instability of ablatively accelerated planar targets. First results show that Nike has spatially uniform ablation pressures (Δp/p〈2%). Targets have been accelerated for distances sufficient to study hydrodynamic instability while maintaining good planarity. In this review we present the performance of the Nike laser in producing uniform illumination, and its performance in correspondingly uniform acceleration of targets. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871661
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  • 5
    Electronic Resource
    Electronic Resource
    Aneurisms in laser-driven blast waves (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 3353-3361 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: When a short-pulse laser beam is focused onto a solid target in a few torr ambient gas, the expanding target plasma couples to the resulting ambient plasma. Dark-field shadowgrams show that a thin, nearly spherical blast front is produced. These shadowgrams also show that certain regions of the blast front (called aneurisms) may project well ahead of the neighboring, spherical part. Several mechanisms for aneurisms are discussed. One class of aneurisms is consistently produced along the laser axis when the laser energy is greater than about 10 J. Two-dimensional, hydrodynamic computer simulations of these on-axis aneurisms show that they can be accounted for by the laser heating of an on-axis channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866899
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  • 6
    Electronic Resource
    Electronic Resource
    Laser interaction in long-scale-length plasmas (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 1305-1320 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Absorption of a short-pulse, high-intensity Nd-laser beam (vacuum irradiance of 1014 to 1015 W/cm2) by preformed plasmas of different density scale lengths is investigated. Increased effects of plasma instabilities are found at longer scale lengths. The amount of backscattered light increases with plasma scale length and limits the absorption fraction at the longest scale length. The onset of suprathermal electron production, deduced from observations of energetic (20 to 50 keV) x rays, occurs at lower laser irradiance for longer-scale-length plasmas. A correlation between energetic x rays and 3ω0/2 emission suggests that the suprathermal electrons are produced by a plasma instability at quarter-critical density. At higher intensities there is evidence for severe perturbations of the preformed plasma and for self-focusing of the incident beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865880
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  • 7
    Electronic Resource
    Electronic Resource
    Evidence in the second-harmonic emission for self-focusing of a laser pulse in a plasma (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2563-2569 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Short-pulse (300 psec), high-intensity (1014−1015 W/cm2) Nd-laser light was propagated into variable scale length plasmas (Ln≡n/∇n=200–400 μm at 0.1 critical density) preformed by long-pulse (4 nsec), low-intensity ((approximately-equal-to)6×1012 W/cm2) irradiation of planar targets. For high short-pulse intensities (≥5×1014 W/cm2), time-integrated images show filament-shaped regions of second-harmonic (2ω0) emission from the low density (0.01≤ne/nc≤0.2) region of the ablation plasma. Two-dimensional computer calculations of the hyrodynamics and laser beam propagation indicate that these filaments are consistent with ponderomotive self-focusing of the short pulse. A theoretical model that explains the 2ω0 generation mechanism within low-density filaments is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865264
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  • 8
    Electronic Resource
    Electronic Resource
    Spectroscopic and interferometric measurements of laser–plasma produced blast waves (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2058-2058 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A laser-produced plasma generates blast waves as it expands supersonically into a stationary photoionized background gas (N2) at a pressure of 1–5 Torr.1 Using a combination of spectroscopic and interferometric measurements, time- and space-resolved values of the temperature and density are obtained. This study was performed on targets in the NRL Pharos III laser facility with laser energies of 20–120 J and pulse durations of ∼5 ns. A 1-m spectrograph equipped with three photomultiplier channels, which are calibrated on an absolute scale, is used for the spectroscopic measurements. The interferometry is done with a folded-wavefront interferometer. It uses an optical probe pulse at 5270 A(ring) that is split off of the main laser pulse, reduced in pulse duration (∼300 ps), and time delayed. Interferometric measurements can be made simultaneously with the spectroscopic measurements. Experimental data and the technique of analysis will be shown. This work was supported by the Defense Nuclear Agency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138735
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  • 9
    Electronic Resource
    Electronic Resource
    Time-resolved, simultaneous density, temperature, and absorption measurements in dense laser-produced plasmas (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3596-3599 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe an optical diagnostic setup which permits simultaneous spatially and temporally resolved measurements of temperature and density from cold, dense laser-produced plasmas. Such information is necessary to investigate the physics of strongly coupled plasmas. The plasma is created in a slab geometry such that the transverse slab dimension is approximately one optical depth of the probing radiation in thickness. To perform the measurements the 2nd harmonic (λ=0.527 μm) of a mode-locked Nd:glass laser (τpulse=300–500 ps) is split into two orthogonally polarized beams. One of the beams measures plasma electron density using polarization wave front interferometry. The other beam uses a set of fast (τ=350 ps) photodiodes to measure single-frequency optical absorption. Plasma electron temperature is determined from time-resolved absolute emission measurements combined with the optical absorption measurements via Kirchoff's law. This technique avoids the difficulties involved in spectroscopic temperature measurements, where the spectral intensities and line profiles are affected by the physics of the cold, dense plasma. A set of timing fiducials allows the entire set of diagnostics to be synchronized in time, while an accurate, self-referenced alignment system assures that all diagnostics sample the same region of plasma volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141577
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  • 10
    Electronic Resource
    Electronic Resource
    Time-resolved, simultaneous density, temperature, and absorption measurements in dense laser-produced plasmas (abstract) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2985-2985 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe an optical diagnostic setup which permits simultaneous spatially and temporally resolved measurements of temperature and density from cold, dense laser-produced plasmas. Such information is necessary to investigate the physics of strongly coupled plasmas. The plasma is created in a slab geometry such that the transverse slab dimension is approximately one optical depth of the probing radiation in thickness. To perform the measurements the 2nd harmonic (λ=0.527 μm) of a mode-locked Nd:glass laser (τpulse=300–500 ps) is split into two orthogonally polarized beams. One of the beams measures plasma electron density using polarization wave front interferometry. The other beam uses a set of fast (τ=350 ps) photodiodes to measure single-frequency optical absorption. Plasma electron temperature is determined from time-resolved absolute emission measurements combined with the optical absorption measurements via Kirchoff's law. This technique avoids the difficulties involved in spectroscopic temperature measurements, where the spectral intensities and line profiles are affected by the physics of the cold, dense plasma. A set of timing fiducials allows the entire set of diagnostics to be synchronized in time, while an accurate, self-referenced alignment system assures that all diagnostics sample the same region of plasma volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141749
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