High-resolution monochromatic x-ray imaging system based on spherically bent crystals

Aglitskiy, Y.; Lehecka, T.; Obenschain, S. P.; Bodner, S. E.; Pawley, C. J.; Gerber, K. A.; Sethian, J. D.; Brown, C. M.; Seely, John F.; Feldman, U.; Holland, Glenn E.

doi:10.1364/ao.37.005253

Cited by 96 publications

(40 citation statements)

References 33 publications

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“…The x-ray side-on radiography 30,31 diagnostic was mainly devoted to the characterization of the plasma parameters (density and temperature) of the 1 g=cm 3 targets at different stages of the compression.…”

Section: B Diagnostics Setupmentioning

confidence: 99%

Laser-driven cylindrical compression of targets for fast electron transport study in warm and dense plasmas

et al. 2011

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Fast ignition requires a precise knowledge of fast electron propagation\ud in a dense hydrogen plasma. In this context, a dedicated HiPER (High\ud Power laser Energy Research) experiment was performed on the VULCAN\ud laser facility where the propagation of relativistic electron beams\ud through cylindrically compressed plastic targets was studied. In this\ud paper, we characterize the plasma parameters such as temperature and\ud density during the compression of cylindrical polyimide shells filled\ud with CH foams at three different initial densities. X-ray and proton\ud radiography were used to measure the cylinder radius at different stages\ud of the compression. By comparing both diagnostics results with 2D\ud hydrodynamic simulations, we could infer densities from 2 to 11 g/cm(3)\ud and temperatures from 30 to 120 eV at maximum compression at the center\ud of targets. According to the initial foam density, kinetic, coupled\ud (sometimes degenerated) plasmas were obtained. The temporal and spatial\ud evolution of the resulting areal densities and electrical conductivities\ud allow for testing electron transport in a wide range of configurations.\ud (C) 2011 American Institute of Physics. {[doi: 10.1063/1.3578346]

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Section: B Diagnostics Setupmentioning

confidence: 99%

Laser-driven cylindrical compression of targets for fast electron transport study in warm and dense plasmas

et al. 2011

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“…X-rays from a laser illuminated Si source transmit through the target and are imaged onto the slit of an x-ray streak camera by means of a spherical quartz crystal. 25 …”

Section: Experimental Arrangement and Conditionsmentioning

confidence: 99%

Effects of thin high-Z layers on the hydrodynamics of laser-accelerated plastic targets

et al. 2002

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We present experimental results and simulations that study the effects of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of laser accelerated plastic targets. These experiments employ a laser pulse with a low-intensity foot that rises into a high-intensity main pulse. This pulse shape simulates the generic Report Documentation PageForm Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. We present experimental results and simulations that study the effects of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of laser accelerated plastic targets. These experiments employ a laser pulse with a low-intensity foot that rises into a high-intensity main pulse. This pulse shape simulates the generic shape needed for high-gain fusion implosions. Imprint of laser nonuniformity during start up of the low intensity foot is a well-known seed for hydrodynamic instability. We observe large reductions in hydrodynamic instability seeded by laser imprint when certain minimum thickness gold or palladium layers are applied to the laser-illuminated surface of the targets. The experiment indicates that the reduction in imprint is at least as large as that obtained by a 6 times improvement in the laser uniformity. We present simulations supported by experiments showing that during the low intensity foot the laser light can be nearly completely absorbed by the high-Z layer. X-rays originating from the high-Z layer heat the underlying lower-Z plastic target material and cause large buffering plasma to form between the layer and the accelerated target. This long-scale plasma apparently isolates the target from laser nonuniformity and accounts for the observed large reduction in laser imprint. With onset of the higher intensity main pulse, the high-Z layer expands and the laser light is transmitted. This technique will be useful in reducing laser imprint in pellet implosions and thereby allow the design of more robust targets for high-gain laser fusion. Prescribed by ANSI Std Z39-18 2 shape needed for high-gain fusion implosions. Imprint of laser nonuniformity during start up of the low intensity foot is a well-known seed for hydrodynamic instability. We observe large reductions in hydrodynamic instability seeded by laser...

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“…1) is a modification of the Nike monochromatic x-ray imaging system based on Bragg reflection from spherically curved crystals [15]. An addition of a streak camera to this system made it possible to analyze continuous time behavior of mass variation, which is necessary to reveal the nonmonotonic evolution of the processes under study.…”

Section: Rmentioning

confidence: 99%

Direct Observation of Mass Oscillations Due to Ablative Richtmyer-Meshkov Instability in Plastic Targets

et al. 2001

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We report the first direct experimental observation of the ablative RichtmyerMeshkov instability. It manifests itself in oscillations of areal mass that occur during the shock transit time, which are caused by the rocket effect or dynamic overpressure characteristic of interaction between the laser absorption zone and the ablation front.With the 4 ns long Nike KrF laser pulse and our novel diagnostic technique (monochromatic x-ray imaging coupled to a streak camera) we were able to register a peak and a valley of the areal mass variation before the observed onset of the RayleighTaylor growth.PACS numbers: 52.57. Fg, 52.70.La, Report Documentation PageForm Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. ABSTRACTWe report the first direct experimental observation of the ablative Richtmyer-Meshkov instability. It manifests itself in oscillations of areal mass that occur during the shock transit time, which are caused by the rocket effect or dynamic overpressure characteristic of interaction between the laser absorption zone and the ablation front. With the 4 ns long Nike KrF laser pulse and our novel diagnostic technique (monochromatic x-ray imaging coupled to a streak camera) we were able to register a peak and a valley of the areal mass variation before the observed onset of the Rayleigh-Taylor growth. Most of our knowledge in this field still comes from simulations and theory. The seed amplitudes are known to form during the early-time period that includes a shock wave transit from the front to the rear surface of the target, and a rarefaction wave transit in the opposite direction. During this time interval, the areal mass perturbations caused by all sources of non-uniformity are expected to oscillate [4][5][6][7][8][9]. The physical mechanisms driving the oscillations depend on whether the perturbations are initially at the front surface of the target (laser imprint, front surface roughness) or at its rear surface (feedout, see [9]). Here, we limit ourselves to the former case, where the oscillations are caused by the rocket effect, or the dynamic overpressure [6,8,10,11]. The oscillatory behavior is consistent with the expression for the growth rate Γ of ablative RT instability, which has recently been established [10,11] for the case of large Froude number (low acceleration): perturbed, and a part of it gets closer to the hot laser absorption zone, the temperature at the ablation front does not increase, but the temperature gradient in its vicinity, T ∇ , does. This, in turn, increases the local heat flux to the ablation front, T ∇ − κ , hence, the rate of mass ablation from it, thereby increasing the ablative pressure and pushing this part of the ablation front back. The physics of this rocket effect is explained in detail inRefs. 6,8,10. The rocket effect rat...

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High-resolution monochromatic x-ray imaging system based on spherically bent crystals

Cited by 96 publications

References 33 publications

Laser-driven cylindrical compression of targets for fast electron transport study in warm and dense plasmas

Laser-driven cylindrical compression of targets for fast electron transport study in warm and dense plasmas

Effects of thin high-Z layers on the hydrodynamics of laser-accelerated plastic targets

Direct Observation of Mass Oscillations Due to Ablative Richtmyer-Meshkov Instability in Plastic Targets

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