Y. Aglitskiy

Leidos, Inc., Reston, Virginia, United States

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Publications (122)137.25 Total impact

  • Max Karasik · J L Weaver · Y Aglitskiy · J Oh · S P Obenschain
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    ABSTRACT: Imprinting of laser nonuniformity is a limiting factor in direct-drive inertial confinement fusion experiments, particularly when available laser smoothing is limited. A thin (∼400 Å) high-Z metal coating is found to substantially suppress laser imprint for planar targets driven by pulse shapes and intensities relevant to implosions on the National Ignition Facility while retaining low adiabat target acceleration. A hybrid of indirect and direct drive, this configuration results in initial ablation by x rays from the heated high-Z layer, creating a large standoff for perturbation smoothing.
    Physical Review Letters 02/2015; 114(8):085001. DOI:10.1103/PhysRevLett.114.085001 · 7.51 Impact Factor
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    ABSTRACT: We will present results from follow-on experiments to the record-high velocities achieved using the ultra-uniform deep-uv drive of the Nike KrF laser [Karasik et al, Phys. Plasmas 17, 056317 (2010)], in which highly accelerated planar foils of deuterated polystyrene were made to collide with a witness foil to produce ˜1 Gbar shock pressures and result in heating of matter to thermonuclear temperatures. Such velocities may indicate a path to lower minimum energy required for central ignition. Still higher velocities and higher target densities are required for impact fast ignition. New results give velocity of >1,100 km/s achieved through improvements in pulseshaping. Variation of second foil parameters results in significant change in fusion neutron production on impact. In-flight target density is inferred from target heating upon collision via DD neutron time-of-flight ion temperature measurement. Availability of pressures generated by collisions of such highly accelerated flyers may provide an experimental platform for study of matter at extreme conditions. Work is supported by US DOE (NNSA).
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    ABSTRACT: An experimental study of hydrodynamic perturbation evolution in a strong unsupported shock wave, which is immediately followed by an expansion wave, is reported. A planar solid plastic target rippled on the front side is irradiated with a 350–450 ps long laser pulse. The perturbation evolution in the target is observed using face-on monochromatic x-ray radiography during and for up to 4 ns after the laser pulse. The theoretically predicted large oscillations of the areal mass in the target are observed for the first time. Multiple phase reversals of the areal mass modulation are detected.
    Physical Review Letters 08/2012; 109(8). DOI:10.1103/PhysRevLett.109.085001 · 7.51 Impact Factor
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    ABSTRACT: Experimental study of hydrodynamic perturbation evolution triggered by a laser-driven shock wave breakout at the free rippled rear surface of a plastic target is reported. At sub-megabar shock pressure, planar jets manifesting the development of the Richtmyer-Meshkov-type instability in a non-accelerated target are observed. As the shock pressure exceeds 1 Mbar, an oscillatory rippled expansion wave is observed, followed by the "feedout" of the rear-surface perturbations to the ablation front and the development of the Rayleigh-Taylor instability, which breaks up the accelerated target.
    Physics of Plasmas 07/2012; 19(10). DOI:10.1063/1.4764287 · 2.25 Impact Factor
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    ABSTRACT: We will present results from follow-on experiments to the record-high velocities of 1000 km/s achieved on Nike [Karasik et al, Phys. Plasmas 17, 056317(2010)], in which highly accelerated planar foils of deuterated polystyrene were made to collide with a witness foil to produce ˜1 Gbar shock pressures and result in heating of matter to thermonuclear temperatures. Still higher velocities and higher target densities are required for impact fast ignition. The aim of these experiments is using the focal zoom capability of Nike and shaping the driving pulse to minimize shock heating of the accelerated target to achieve higher densities and velocities. In-flight target density is inferred from target heating upon collision via DD neutron time-of-flight ion temperature measurement. Work is supported by US DOE (NNSA) and Office of Naval Research.
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    ABSTRACT: The first experimental study of hydrodynamic perturbation evolution in a strong unsupported shock wave, which is immediately followed by a rarefaction wave, is reported. Our planar solid polystyrene laser-machined targets, 50 to 100 μm thick, rippled from the front side with a single-mode wavelength 30 or 45 μm and peak-to-valley amplitude 4 to 6 μm, were irradiated with a 350 ps long Nike KrF laser pulse at peak intensity of up to 330 TW/cm^2. The perturbation evolution in the target was observed using face-on monochromatic x-ray radiography while the pulse lasted and for 3 to 4 ns after it ended. While the driving pulse was on, the areal mass modulation amplitude in the target was observed to grow by a factor of up to ˜4 due to the ablative Richtmyer-Meshkov instability. After the end of the pulse, while the strong unsupported shock wave propagated through the unperturbed target, the theoretically predicted large oscillations of the areal mass [A. L. Velikovich et al., Phys. Plasmas 10, 3270 (2003)] were observed. Multiple phase reversals of the areal mass modulation have been detected.
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    ABSTRACT: Recent progress of impact ignition is reported: First, a maximum velocity ∼ 1000 km/s has been achieved under the operation of NIKE KrF laser at Naval Research Laboratory (laser wavelength = 0.25µm) in the use of a planar target made of plastic. Two-dimensional simulation have been performed for burn and ignition to show the feasibility of the impact ignition. Optimized direct illumination scheme is also addressed.
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    ABSTRACT: When a multi-Mbar shock wave propagates into a laser target from a rough or non-uniformly irradiated surface, the shock front after a few rapidly decaying oscillations becomes planar. Much stronger oscillations of the shock front and the shocked mass have been theoretically predicted for the case when the shock front is unsupported. For example, after a short (sub-ns) laser pulse deposits finite energy in a target, the shock wave launched into it is immediately followed by a rarefaction wave. If the irradiated surface is rippled, theory and simulations predict strong oscillations of the areal mass perturbation amplitude in the target. We report the first experiments designed to observe this effect. They have become possible by adding short-driving-pulse capability to the Nike laser. The laser operated at peak intensity of 1014 W/cm2, with Gaussian pulse FWHM 0.35 ns and focal spot flat top diameter 400 μm. The targets were planar plastic foils, 53 to 100 μm thick, rippled from the irradiated side at the wavelength 30 and 45 μm and peak-to-valley amplitude 4 to 6 μm. We have observed the predicted strong oscillations with the monochromatic x-ray imaging diagnostics fielded on Nike. The distribution of mass in the target is recorded by an x-ray camera providing spatial resolution in one dimension, perpendicular to the initial ripples, and continuously covering the whole time interval of shock propagation through the target. While the driving pulse is on, the areal mass perturbation amplitude grows by a factor ~2 due to the ablative Richtmyer-Meshkov instability. It then decreases, reverses phase, and reaches another maximum, noticeably larger than its initial value, before the shock breakout at the rear target surface.
    IEEE International Conference on Plasma Science 01/2011; DOI:10.1109/PLASMA.2011.5992991
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    ABSTRACT: When a short (sub-ns) laser pulse deposits finite energy in a target, the shock wave launched into it is immediately followed by a rarefaction wave. If the irradiated surface is rippled, theory and simulations predict strong oscillations of the areal mass perturbation amplitude in the target [A. L. Velikovich et al., Phys. Plasmas 10, 3270 (2003).] The first experiment designed to observe this effect has become possible by adding short-driving-pulse capability to the Nike laser, and has been scheduled for the fall of 2010. Simulations show that while the driving pulse of 0.3 ns is on, the areal mass perturbation amplitude grows by a factor ˜2 due to ablative Richtmyer-Meshkov instability. It then decreases, reverses phase, and reaches another maximum, also about twice its initial value, shortly after the shock breakout at the rear target surface. This signature behavior is observable with the monochromatic x-ray imaging diagnostics fielded on Nike.
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    ABSTRACT: We will present results from follow-on experiments to the record-high velocities of 1000 km/s achieved on Nike [Karasik et al., Phys. Plasmas 17, 056317 (2010) ], in which highly accelerated planar foils of deuterated polystyrene were made to collide with a witness foil to produce extreme shock pressures and result in heating of matter to thermonuclear temperatures. Still higher velocities and higher target densities are required for impact fast ignition. The aim of these experiments is shaping the driving pulse to minimize shock heating of the accelerated target and using the focal zoom capability of Nike to achieve higher densities and velocities. Spectroscopic measurements of electron temperature achieved upon impact will complement the neutron time-of-flight ion temperature measurement. Work is supported by US DOE and Office of Naval Research.
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    ABSTRACT: The development of a new experimental system for generating a strong shear flow in a high-energy-density plasma is described in detail. The targets were designed with the goal of producing a diagnosable Kelvin–Helmholtz (KH) instability, which plays an important role in the transition turbulence but remains relatively unexplored in the high-energy-density regime. To generate the shear flow the Nike laser was used to drive a flow of Al plasma over a low-density foam surface with an initial perturbation. The interaction of the Al and foam was captured with a spherical crystal imager using 1.86keV X-rays. The selection of the individual targets components is discussed and results are presented.
    High Energy Density Physics 06/2010; 6(2):179-184. DOI:10.1016/j.hedp.2010.01.013 · 1.52 Impact Factor
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    ABSTRACT: The Nike krypton fluoride laser [ S. P. Obenschain, S. E. Bodner, D. Colombant, et al., Phys. Plasmas 3, 2098 (1996) ] is used to accelerate planar plastic foils to velocities that for the first time reach 1000 km/s. Collision of the highly accelerated deuterated polystyrene foil with a stationary target produces ∼ Gbar shock pressures and results in heating of the foil to thermonuclear temperatures. The impact conditions are diagnosed using DD fusion neutron yield, with ∼ 106 neutrons produced during the collision. Time-of-flight neutron detectors are used to measure the ion temperature upon impact, which reaches 2–3 keV.
    Physics of Plasmas 05/2010; 17(5):056317-056317-7. DOI:10.1063/1.3399786 · 2.25 Impact Factor
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    ABSTRACT: A laser driven millimeter-scale target was used to generate a supersonic shear layer in an attempt to create a Kelvin–Helmholtz (KH) unstable interface in a high-energy-density (HED) plasma. The KH instability is a fundamental fluid instability that remains unexplored in HED plasmas, which are relevant to the inertial confinement fusion and astrophysical environments. In the experiment presented here the Nike laser [ S. P. Obenschain et al., Phys. Plasmas 3, 2098 (1996) ] was used to create and drive Al plasma over a rippled foam surface. In response to the supersonic Al flow (Mach = 2.6±1.1) shocks should form in the Al flow near the perturbations. The experimental data were used to infer the existence and location of these shocks. In addition, the interface perturbations show growth that has possible contributions from both KH and Richtmyer–Meshkov instabilities. Since compressible shear layers exhibit smaller growth, it is important to use the KH growth rate derived from the compressible dispersion relation.
    Physics of Plasmas 04/2010; 17(5):056310-056310-9. DOI:10.1063/1.3314335 · 2.25 Impact Factor
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    ABSTRACT: In inertial confinement fusion (ICF), the possibility of ignition or high energy gain is largely determined by our ability to control the Rayleigh-Taylor (RT) instability growth in the target. The exponentially amplified RT perturbation eigenmodes are formed from all sources of the target and radiation non-uniformity in a process called seeding. This process involves a variety of physical mechanisms that are somewhat similar to the classical Richtmyer-Meshkov (RM) instability (in particular, most of them are active in the absence of acceleration), but differ from it in many ways. In the last decade, radiographic diagnostic techniques have been developed that made direct observations of the RM-type effects in the ICF-relevant conditions possible. New experiments stimulated the advancement of the theory of the RM-type processes. The progress in the experimental and theoretical studies of such phenomena as ablative RM instability, re-shock of the RM-unstable interface, feedout and perturbation development associated with impulsive loading is reviewed.
    Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 04/2010; 368(1916):1739-68. DOI:10.1098/rsta.2009.0131 · 2.86 Impact Factor
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    ABSTRACT: An improved high luminosity, easily spectrally tunable backlighting scheme based on a spherically bent crystal is considered in this paper. Contrary to the traditional backlighting scheme, we used crystal far from normal incidence, and the backlighter source was inside the Rowland circle. With the presented configuration, we obtained a spatial resolution up to 8 µm in the desired direction with an X-ray backlighting energy close to 5 keV. Detailed discussions and ray-tracing calculations show that with this convenient scheme resolution down to 5 µm can be achieved. A dedicated application to high energy density physics is presented: the radiography of shock compressed matter.
    Laser and Particle Beams 11/2009; 27(04):601 - 609. DOI:10.1017/S0263034609990322 · 1.70 Impact Factor
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    ABSTRACT: Accurate shock timing is a key issue of both indirect- and direct-drive laser fusions. The experiments on the Nike laser at NRL presented here were made possible by improvements in the imaging capability of our monochromatic x-ray diagnostics based on Bragg reflection from spherically curved crystals. Side-on imaging implemented on Nike makes it possible to observe dynamics of the shock wave and ablation front in laser-driven solid targets. We can choose to observe a sequence of 2D images or a continuous time evolution of an image resolved in one spatial dimension. A sequence of 300 ps snapshots taken using vanadium backlighter at 5.2 keV reveals propagation of a shock wave in a solid plastic target. The shape of the shock wave reflects the intensity distribution in the Nike beam. The streak records with continuous time resolution show the x-t trajectory of a laser-driven shock wave in a 10% solid density DVB foam.
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    ABSTRACT: Experimental study of a shock-decelerated ablation front is reported. A planar solid plastic target is accelerated by a laser across a vacuum gap and collides with a lower-density plastic foam layer. While the target is accelerated, a fast Rayleigh-Taylor (RT) growth of the seeded single-mode perturbation at the ablation front is observed. After the collision, the velocity of the ablation front is seen to remain constant. The reshock quenches the RT growth but does not trigger any Richtmyer-Meshkov growth at the ablation front, which is shown to be consistent with both theory and simulations.
    Physical Review Letters 08/2009; 103(8):085002. DOI:10.1103/PHYSREVLETT.103.085002 · 7.51 Impact Factor
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    ABSTRACT: We performed integrated experiments on impact ignition, in which a portion of a deuterated polystyrene (CD) shell was accelerated to about 600 km/s and was collided with precompressed CD fuel. The kinetic energy of the impactor was efficiently converted into thermal energy generating a temperature of about 1.6 keV. We achieved a two-order-of-magnitude increase in the neutron yield by optimizing the timing of the impact collision, demonstrating the high potential of impact ignition for fusion energy production.
    Physical Review Letters 07/2009; 102(23):235002. DOI:10.1103/PHYSREVLETT.102.235002 · 7.51 Impact Factor
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    ABSTRACT: form only given. Shear flows arise in many high-energy-density (HED) and astrophysical systems, yet few laboratory experiments have been carried out to study their evolution in these extreme environments. Fundamentally, shear flows can initiate mixing via the Kelvin-Helmholtz (KH) instability and may eventually drive a transition to turbulence. We present two dedicated shear flow experiments that created subsonic and supersonic shear layers in HED plasmas. In the subsonic case the Omega laser was used to drive a shock wave along a rippled plastic interface, which subsequently rolled-upped into large KH vortices. In the supersonic shear experiment the Nike laser was used to drive Al plasma across a low- density foam surface also seeded with a ripple. Unlike the subsonic case, detached shocks developed around the ripples in response to the supersonic Al flow.
    Plasma Science - Abstracts, 2009. ICOPS 2009. IEEE International Conference on; 01/2009
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    ABSTRACT: The knowledge of Warm Dense Matter is important in different domains such as inertial confinement fusion, astrophysics and geophysics. The development of techniques for direct probing of this type of matter is of great interest. X-ray radiography is one of the most promising diagnostic to measure density directly. Here we present some results of low-Z material radiography and an experiment devoted to characterize a short pulse laser driven hard x-ray source for the radiography of medium and high Z matter. Experiments have been performed on LULI2000 and TW facilities at the Ecole Polytechnique.

Publication Stats

1k Citations
137.25 Total Impact Points

Institutions

  • 2015
    • Leidos, Inc.
      Reston, Virginia, United States
  • 2000–2010
    • SAIC
      McLean, Virginia, United States
  • 2006–2007
    • National Institute of Standards and Technology
      Maryland, United States