Simultaneous neutron and x-ray imaging of inertial confinement fusion experiments along a single line of sight at Omega

Danly, C. R.; Day, Thomas; Fittinghoff, D. N.; Herrmann, H. W.; Izumi, N.; Kim, Y. H.; Martinez, J. I.; Merrill, F. E.; Schmidt, D. W.; Simpson, Raspberry; Volegov, P. L.; Wilde, C. H.

doi:10.1063/1.4918285

Cited by 10 publications

(2 citation statements)

References 11 publications

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“…It is possible to measure the symmetry of a full-up DT-filled capsule using the neutron imaging system [100,101] to get the shape of the neutronemitting region. The x-ray self-emission (time-integrated) is recorded by the CNXI instrument [102].…”

Section: Symcapmentioning

confidence: 99%

Effect of Impurity Atoms on Thermonuclear Yield

Batha

2020

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The presence of impurity atoms in an inertial confinement fusion (ICF) implosion can greatly affect the burning of the thermonuclear fuel. This is a serious concern for attaining ignition as high atomic number atoms, such as carbon, can mix into the hot spot and reach the deuterium-tritium (DT) fuel, absorb energy from the implosion, and radiate away that energy. The temperature of the DT fuel drops and reduces the reactivity of the fuel resulting in lower thermonuclear yield. Fuel impurities can also be a useful diagnostic as when higher-Z atoms, such as Ar, Kr, and Xe, are purposefully mixed into the fuel. From the spectra emitted by these atoms, the temperature and density of the fuel can be deduced. The long history of using such tracer atoms by the national ICF program shows the great advances in experimental technique, diagnostic instruments, and atomic-physics modeling over the past 50 years. A particular set of experiments, the "High-Z" campaign, is reviewed in depth as this was the most systematic study of tracer element composition and quantity ever reported. Difficulties in interpreting the results of those experiments due to the limited code capabilities at that time are discussed. A main concern for the High-Z campaign was the then current state of non-Local Thermodynamic Equilibrium (nLTE) atomic physics models. The present state of nLTE modeling and its implementation in Los Alamos's multi-physics codes is discussed in this report. To further the understanding of the complex interaction of high-Z atoms in the gas, a survey of relevant existing experimental platforms at the National Ignition Facility (NIF) and the Omega Laser Facility are presented along with the current state of pertinent diagnostics at NIF and Omega. This review concludes with a discussion of the trade-off available between temperature and volume of the imploded ICF capsule with the goal of maximizing the total yield. 10 24 cm•3 3 x 10 23 cm•3

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Section: Symcapmentioning

confidence: 99%

Effect of Impurity Atoms on Thermonuclear Yield

Batha

2020

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“…Previous experiments have also involved intentionally asymmetrically driven OMEGA implosions (see, e.g., Refs. [22][23][24][25], but the inference of the impact of these asymmetries on the implosion flow field and directional inferred apparent T ion has not previously been attempted. In the experiments discussed in this paper, a mode 2 asymmetry was intentionally imposed by reducing the laser drive in two opposing cones around the implosion and apparent T ion measured at angles parallel and perpendicular to the imposed asymmetry.…”

Section: Introductionmentioning

confidence: 99%

Impact of imposed mode 2 laser drive asymmetry on inertial confinement fusion implosions

et al. 2019

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Low-mode asymmetries have emerged as one of the primary challenges to achieving high-performing inertial confinement fusion implosions. These asymmetries seed flows in the implosions, which will manifest as modifications to the measured ion temperature (T ion ) as inferred from the broadening of primary neutron spectra. The effects are important to understand (i) to learn to control and mitigate low-mode asymmetries and (ii) to experimentally more closely capture thermal T ion used as input in implosion performance metric calculations. In this paper, results from and simulations of a set of experiments with a seeded mode 2 in the laser drive are described. The goal of this intentionally asymmetrically driven experiment was to test our capability to predict and measure the signatures of flows seeded by the low-mode asymmetry. The results from these experiments [first discussed in M. Gatu Johnson et al., Phys. Rev. E 98, 051201(R) (2018)] demonstrate the importance of interplay of flows seeded by various asymmetry seeds. In particular, measured T ion and self-emission x-ray asymmetries are expected to be well captured by interplay between flows seeded by the imposed mode 2 and the capsule stalk mount. Measurements of areal density asymmetry also indicate the importance of the stalk mount as an asymmetry seed in these implosions. The simulations brought to bear on the problem (1D LILAC, 2D xRAGE, 3D ASTER, and 3D Chimera) show how thermal T ion is expected to be significantly lower than T ion as inferred from the broadening of measured neutron spectra. They also show that the electron temperature is not expected to be the same as T ion for these implosions.Published under license by AIP Publishing. https://doi.

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Demonstration of a time-integrated short line of sight neutron imaging system for inertial confinement fusion

Simpson

Christensen

Danly

et al. 2015

Review of Scientific Instruments

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The Neutron Imaging System (NIS) is an important diagnostic for understanding implosions of deuterium-tritium capsules at the National Ignition Facility. While the detectors for the existing system must be positioned 28 m from the source to produce sufficient imaging magnification and resolution, recent testing of a new short line of sight neutron imaging system has shown sufficient resolution to allow reconstruction of the source image with quality similar to that of the existing NIS on a 11.6 m line of sight. The new system used the existing pinhole aperture array and a stack of detectors composed of 2 mm thick high-density polyethylene converter material followed by an image plate. In these detectors, neutrons enter the converter material and interact with protons, which recoil and deposit energy within the thin active layer of the image plate through ionization losses. The described system produces time-integrated images for all neutron energies passing through the pinhole. We present details of the measurement scheme for this novel technique to produce energy-integrated neutron images as well as source reconstruction results from recent experiments at NIF.

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Simultaneous neutron and x-ray imaging of inertial confinement fusion experiments along a single line of sight at Omega

Cited by 10 publications

References 11 publications

Effect of Impurity Atoms on Thermonuclear Yield

Effect of Impurity Atoms on Thermonuclear Yield

Impact of imposed mode 2 laser drive asymmetry on inertial confinement fusion implosions

Demonstration of a time-integrated short line of sight neutron imaging system for inertial confinement fusion

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