Effects of variable x-ray preheat shielding in indirectly driven implosions

Landen, O. L.; Keane, C. J.; Hammel, B. A.; Levedahl, W. K.; Amendt, Peter; Colvin, Jeff; Cable, M. D.; Cook, Robert; Dittrich, Thomas; Haan, S. W.; Hatchett, S. P.; Hay, R.G.; Lerche, R. A.; McEachern, R.; Murphy, T. J.; Nelson, Michael; Suter, L. J.; Wallace, R. J.

doi:10.1063/1.872007

Cited by 21 publications

(6 citation statements)

References 38 publications

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“…Landen et al 12 reported temperatures 30% greater than calculated for indirectly driven capsule experiments performed on the Nova laser. 21 Despite the increased observed ion temperature, the simulated yield was 3-4 times the observed yield.…”

Section: Discussionmentioning

confidence: 95%

“…In inertial confinement fusion (ICF) experiments, 6,7 this distribution is usually measured 8 in the neutron time-of-flight domain using scintillation detectors operated in current mode 9 or neutron detector arrays, 10 but has also been measured using proton or other charged-particle recoil methods. 11 Neutron spectral widths from ICF experiments have often been observed to be wider than expected from simulations [12][13][14] or the measured yield. 15 This has been attributed to mass flows within the reacting region, 15,16 higher contributions to the spatially averaged ion temperature from the hottest central regions of the core, 12 and expansion of the reacting plasma at velocities near the sound speed.…”

Section: Introductionmentioning

confidence: 95%

“…11 Neutron spectral widths from ICF experiments have often been observed to be wider than expected from simulations [12][13][14] or the measured yield. 15 This has been attributed to mass flows within the reacting region, 15,16 higher contributions to the spatially averaged ion temperature from the hottest central regions of the core, 12 and expansion of the reacting plasma at velocities near the sound speed. 17 The energy of a neutron emitted from a moving plasma can be written…”

Section: Introductionmentioning

confidence: 95%

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The effect of turbulent kinetic energy on inferred ion temperature from neutron spectra

Murphy

2014

Physics of Plasmas

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112

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Measuring the width of the energy spectrum of fusion-produced neutrons from deuterium (DD) or deuterium-tritium (DT) plasmas is a commonly used method for determining the ion temperature in inertial confinement fusion (ICF) implosions. In a plasma with a Maxwellian distribution of ion energies, the spread in neutron energy arises from the thermal spread in the center-of-mass velocities of reacting pairs of ions. Fluid velocities in ICF are of a similar magnitude as the center-of-mass velocities and can lead to further broadening of the neutron spectrum, leading to erroneous inference of ion temperature. Motion of the reacting plasma will affect DD and DT neutrons differently, leading to disagreement between ion temperatures inferred from the two reactions. This effect may be a contributor to observations over the past decades of ion temperatures higher than expected from simulations, ion temperatures in disagreement with observed yields, and different temperatures measured in the same implosion from DD and DT neutrons. This difference in broadening of DD and DT neutrons also provides a measure of turbulent motion in a fusion plasma.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

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The effect of turbulent kinetic energy on inferred ion temperature from neutron spectra

Murphy

2014

Physics of Plasmas

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112

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“…In order to control the deposition of energy in the ablator, and thus the shock compression of the fuel, mid-Z ablator dopants such as germanium, bromine, or copper are often added to the low-Z ablator material. 1,2 The increased opacity provided by ablator dopants ͑see Fig. 1͒ serves to change the radiation-matter coupling as well as to shield the fuel from preheat.…”

Section: Introductionmentioning

confidence: 99%

Tracer spectroscopy diagnostics of doped ablators in inertial confinement fusion experiments on OMEGA

et al. 2004

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Use of d -H 3 e proton spectroscopy as a diagnostic of shell ρ r in capsule implosion experiments with 0.2 NIF scale high temperature Hohlraums at Omegaa) Rev. Sci. Instrum. 79, 10E526 (2008);A spectroscopy diagnostic of plasma gradients in inertial confinement fusion imploded cores (abstract) Rev. Sci.A technique has been developed for studying the time-dependent, local physical conditions in ablator samples in an inertial confinement fusion ͑ICF͒ hohlraum environment. This technique involves backlit point-projection absorption spectroscopy of thin tracer layers buried in the interior of solid samples mounted on laser-driven hohlraums. It is shown how detailed view-factor, atomic, hydrodynamics, and radiation-transport modeling can be used to infer time-dependent physical conditions in the interiors of these samples from the observed absorption spectra. This modeling is applied to the results of an experimental campaign on the OMEGA laser ͓T. R. Boehly et al., Opt. Commun. 133, 495 ͑1997͔͒ designed to compare radiation-wave velocities in doped and undoped ICF ablator materials.

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“…[This stage has previously been investigated in indirectly driven targets at the Lawrence Livermore National Laboratory (LLNL) using plastic targets with an inner layer of Ti-doped CH and an Ardoped D 2 fill. [6][7][8] ] The goal of our initial experiments was to ensure that our diagnostics could measure the conditions in both the core and the shell during shell deceleration and stagnation and that they had enough sensitivity to observe differences in core conditions under various RT-growth conditions. The RT growth was modified by varying the temporal pulse shape (Gaussian or square) and by doping the outer 6 µm of the CH shell with chlorine.…”

Section: Measurements Of Core and Pusher Conditions In Surrogatementioning

confidence: 99%

Measurements of core and pusher conditions in surrogate capsule implosions on the OMEGA laser system

Bradley¹,

Delettrez²,

Epstein³

et al. 1998

Physics of Plasmas

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Experiments have been carried out on the 60-beam, 30 kJ OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] as part of an integrated program to diagnose all phases of direct-drive capsule implosions. Laser-imprint levels and Rayleigh–Taylor growth rates associated with the spherical implosions have been inferred from planar-foil radiography experiments. In spherical targets, measurements of the combined effects of imprint and unstable growth at the ablation surface have been carried out using the burnthrough technique [J. Delettrez et al., Phys. Plasmas 1, 2342 (1994)]. Target behavior during the deceleration phase has been investigated using a series of surrogate cryogenic capsules in which the main fuel layer is represented by a Ti-doped CH shell and the hot spot is represented by an Ar-doped deuterium fill gas.

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Effects of variable x-ray preheat shielding in indirectly driven implosions

Cited by 21 publications

References 38 publications

The effect of turbulent kinetic energy on inferred ion temperature from neutron spectra

The effect of turbulent kinetic energy on inferred ion temperature from neutron spectra

Tracer spectroscopy diagnostics of doped ablators in inertial confinement fusion experiments on OMEGA

Measurements of core and pusher conditions in surrogate capsule implosions on the OMEGA laser system

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