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Pulsed-power driven inertial confinement fusion development at Sandia National Laboratories

Proposed for publication in 5th Special Issue of the IEEE Transactions on Plasma Science Z-Pinch Plasmas.

Cuneo, M.E.; Mazarakis, Michael G.; Lamppa, Derek C.; Kaye, Ronald J.; Nakhleh, Charles N.; Bailey, James E.; Hansen, Stephanie B.; McBride, Ryan D.; Herrmann, Mark H.; Lopez, A.; Peterson, Kyle J.; Ampleford, David A.; Jones, Michael J.; Savage, Mark E.; Jennings, Christopher A.; Martin, Matthew; Slutz, Stephen A.; Lemke, Raymond W.; Christenson, Peggy J.; Sweeney, Mary A.; Jones, Brent M.; Yu, Edmund Y.; McPherson, Leroy A.; Harding, Eric H.; Knapp, Patrick K.; Gomez, Matthew R.; Awe, Thomas J.; Stygar, William A.; Leeper, Ramon J.; Ruiz, Carlos L.; Chandler, Gordon A.; Mckenney, John M.; Owen, Albert C.; McKee, George R.; Matzen, M.K.; Leifeste, Gordon T.; Atherton, B.W.; Vesey, Roger A.; Smith, Ian C.; Geissel, Matthias G.; Rambo, Patrick K.; Sinars, Daniel S.; Sefkow, Adam B.; Rovang, Dean C.; Rochau, G.A.

Abstract not provided.

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TYPE Journal Article YEAR 2012
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Penetrating radiography of imploding and stagnating beryllium liners on the Z accelerator

Physical Review Letters

McBride, Ryan D.; Peterson, Kyle J.; Sefkow, Adam B.; Nakhleh, Charles N.; Laspe, Amy R.; Lopez, Mike R.; Smith, Ian C.; Atherton, B.W.; Savage, Mark E.; Stygar, William A.; Slutz, Stephen A.; Rogers, Thomas J.; Jennings, Christopher A.; Sinars, Daniel S.; Cuneo, M.E.; Herrmann, Mark H.; Lemke, Raymond W.; Martin, Matthew; Vesey, Roger A.

Abstract not provided.

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TYPE Journal Article YEAR 2012
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Measurements of Magneto-Rayleigh-Taylor instability growth in initially solid liners on the Z facility

Sinars, Daniel S.; Edens, Aaron E.; Lopez, Mike R.; Smith, Ian C.; Slutz, Stephen A.; Shores, Jonathon S.; Bennett, Guy R.; Atherton, B.W.; Savage, Mark E.; Stygar, William A.; Leifeste, Gordon T.; Herrmann, Mark H.; Cuneo, M.E.; Peterson, Kyle J.; McBride, Ryan D.; Jennings, Christopher A.; Vesey, Roger A.; Nakhleh, Charles N.

Abstract not provided.

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TYPE Conference YEAR 2011
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Measurements of magneto-Rayleigh-Taylor instability growth during the implosion of initially solid metal liners

Physics of Plasmas

Sinars, Daniel S.; Edens, Aaron E.; Lopez, Mike R.; Smith, Ian C.; Shores, Jonathon S.; Slutz, Stephen A.; Bennett, Guy R.; Atherton, B.W.; Savage, Mark E.; Stygar, William A.; Leifeste, Gordon T.; Herrmann, Mark H.; McBride, Ryan D.; Cuneo, M.E.; Jennings, Christopher A.; Peterson, Kyle J.; Vesey, Roger A.; Nakhleh, Charles N.

Abstract not provided.

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TYPE Journal Article YEAR 2010
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Beryllium liner z-pinches for Magneto-Rayleigh--Taylor studies on Z

McBride, Ryan D.; Slutz, Stephen A.; Jennings, Christopher A.; Sinars, Daniel S.; Lemke, Raymond W.; Martin, Matthew; Vesey, Roger A.; Cuneo, M.E.; Herrmann, Mark H.

Magnetic Liner Inertial Fusion (MagLIF) [S. A. Slutz, et al., Phys. Plasmas 17 056303 (2010)] is a promising new concept for achieving >100 kJ of fusion yield on Z. The greatest threat to this concept is the Magneto-Rayleigh-Taylor (MRT) instability. Thus an experimental campaign has been initiated to study MRT growth in fast-imploding (<100 ns) cylindrical liners. The first sets of experiments studied aluminum liner implosions with prescribed sinusoidal perturbations (see talk by D. Sinars). By contrast, this poster presents results from the latest sets of experiments that used unperturbed beryllium (Be) liners. The purpose for using Be is that we are able to radiograph 'through' the liner using the 6-keV photons produced by the Z-Beamlet backlighting system. This has enabled us to obtain time-resolved measurements of the imploding liner's density as a function of both axial and radial location throughout the field of view. This data is allowing us to evaluate the integrity of the inside (fuel-confining) surface of the imploding liner as it approaches stagnation.

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TYPE Conference YEAR 2010
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Total x-ray power improvement on recent wire array experiments on the Z machine

Jones, Michael J.; Ampleford, David A.; Cuneo, M.E.; Jennings, Christopher A.; Jones, Brent M.; Lopez, Mike R.; Rochau, G.A.; Savage, Mark E.

Recent experiments on the refurbished Z-machine were conducted using large diameter stainless steel arrays which produced x-ray powers of 260 TW. Follow-up experiments were then conducted utilizing tungsten wires with approximately the same total mass with the hypothesis that the total x-ray power would increase. On the large diameter tungsten experiments, the x-ray power averaged over 300 TW and the total x-ray energy was greater than 2MJ. Different analysis techniques for inferring the x-ray power will be described in detail.

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TYPE Conference YEAR 2010
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2D rad-MHD model assessment of designs for multiple-shell gas nozzles for Z

Jones, Brent M.; Coverdale, Christine A.; Ampleford, David A.; Jennings, Christopher A.; Cuneo, M.E.

AASC is designing multiple-shell gas puff loads for Z. Here we assess the influence of the loads initial gas distribution on its K-shell yield performance. Emphasis is placed on designing an optimal central jet initial gas distribution, since it is believed to have a controlling effect on pinch stability, pinch conditions, and radiation physics. We are looking at distributions that optimize total Ar K-shell emission and high energy (>10 KeV) continuum radiation. This investigation is performed with the Mach2 MHD code with non-LTE kinetics and ray trace based radiation transport.

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TYPE Conference YEAR 2010
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Spectroscopic study of z-pinch stagnation on Z

Rochau, G.A.; Bailey, James E.; Coverdale, Christine A.; Ampleford, David A.; Cuneo, M.E.; Jones, Brent M.; Jennings, Christopher A.; Yu, Edmund Y.; Hansen, Stephanie B.

Fast z-pinches provide intense 1-10 keV photon energy radiation sources. Here, we analyze time-, space-, and spectrally-resolved {approx}2 keV K-shell emissions from Al (5% Mg) wire array implosions on Sandia's Z machine pulsed power driver. The stagnating plasma is modeled as three separate radial zones, and collisional-radiative modeling with radiation transport calculations are used to constrain the temperatures and densities in these regions, accounting for K-shell line opacity and Doppler effects. We discuss plasma conditions and dynamics at the onset of stagnation, and compare inferences from the atomic modeling to three-dimensional magneto-hydrodynamic simulations.

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TYPE Conference YEAR 2010
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The evolution of instabilities during magnetically driven liner implosions

Slutz, Stephen A.; Sinars, Daniel S.; McBride, Ryan D.; Jennings, Christopher A.; Herrmann, Mark H.; Cuneo, M.E.

Numerical simulations [S.A. Slutz et al Phys. Plasmas 17, 056303 (2010)] indicate that fuel magnetization and preheat could enable cylindrical liner implosions to become an efficient means to generate fusion conditions. A series of simulations has been performed to study the stability of magnetically driven liner implosions. These simulations exhibit the initial growth and saturation of an electro-thermal instability. The Rayleigh-Taylor instability further amplifies the resultant density perturbations developing a spectrum of modes initially peaked at short wavelengths. With time the spectrum of modes evolves towards longer wavelengths developing an inverse cascade. The effects of mode coupling, the radial dependence of the magnetic pressure, and the initial surface roughness will be discussed.

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TYPE Conference YEAR 2010
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Evaluation of nested wire array dynamics with mixed wire array Z pinches

Coverdale, Christine A.; Jones, Brent M.; Jennings, Christopher A.; Cuneo, M.E.

A series of experiments at the Z Accelerator was performed with 40mm and 50mm diameter nested wire arrays to investigate the interaction of the arrays and assess radiative characteristics. These arrays were fielded with one array as Al:Mg (either the inner or the outer array) and the other array as Ni-clad Ti (the outer or inner array, with respect to location of the Al:Mg). In all the arrays, the mass and radius ratio of the outer:inner was 2:1. The wire number ratio was also 2:1 in some cases, but the Al:Mg wire number was increased in some loads. This presentation will focus on analysis of the emitted radiation (in multiple photon energy bins) and measured plasma conditions (as inferred from x-ray spectra). A discussion on what these results indicate about nested array dynamics will also be presented.

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TYPE Conference YEAR 2010
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Doppler effects on 3-D non-LTE radiation transport and emission spectra

Hansen, Stephanie B.; Jones, Brent M.; Ampleford, David A.; Bailey, James E.; Rochau, G.A.; Coverdale, Christine A.; Jennings, Christopher A.; Cuneo, M.E.

Spatially and temporally resolved X-ray emission lines contain information about temperatures, densities, velocities, and the gradients in a plasma. Extracting this information from optically thick lines emitted from complex ions in dynamic, three-dimensional, non-LTE plasmas requires self-consistent accounting for both non-LTE atomic physics and non-local radiative transfer. We present a brief description of a hybrid-structure spectroscopic atomic model coupled to an iterative tabular on-the-spot treatment of radiative transfer that can be applied to plasmas of arbitrary material composition, conditions, and geometries. The effects of Doppler line shifts on the self-consistent radiative transfer within the plasma and the emergent emission and absorption spectra are included in the model. Sample calculations for a two-level atom in a uniform cylindrical plasma are given, showing reasonable agreement with more sophisticated transport models and illustrating the potential complexity - or richness - of radially resolved emission lines from an imploding cylindrical plasma. Also presented is a comparison of modeled L- and K-shell spectra to temporally and radially resolved emission data from a Cu:Ni plasma. Finally, some shortcomings of the model and possible paths for improvement are discussed.

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TYPE Conference YEAR 2010
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Scaling of X pinches from 1 MA to 6 MA

Sinars, Daniel S.; McBride, Ryan D.; Wenger, D.F.; Cuneo, M.E.; Yu, Edmund Y.; Harding, Eric H.; Hansen, Stephanie B.; Ampleford, David A.; Jennings, Christopher A.

This final report for Project 117863 summarizes progress made toward understanding how X-pinch load designs scale to high currents. The X-pinch load geometry was conceived in 1982 as a method to study the formation and properties of bright x-ray spots in z-pinch plasmas. X-pinch plasmas driven by 0.2 MA currents were found to have source sizes of 1 micron, temperatures >1 keV, lifetimes of 10-100 ps, and densities >0.1 times solid density. These conditions are believed to result from the direct magnetic compression of matter. Physical models that capture the behavior of 0.2 MA X pinches predict more extreme parameters at currents >1 MA. This project developed load designs for up to 6 MA on the SATURN facility and attempted to measure the resulting plasma parameters. Source sizes of 5-8 microns were observed in some cases along with evidence for high temperatures (several keV) and short time durations (<500 ps).

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TYPE SAND Report YEAR 2010
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Mass accretion and nested array dynamics from Ni-Clad Ti-Al wire array Z pinches

Coverdale, Christine A.; Jones, Brent M.; Cuneo, M.E.; Jennings, Christopher A.

Analysis of 50 mm diameter wire arrays at the Z Accelerator has shown experimentally the accretion of mass in a stagnating z pinch and provided insight into details of the radiating plasma species and plasma conditions. This analysis focused on nested wire arrays with a 2:1 (outeninner) mass, radius, and wire number ratio where Al wires were fielded on the outer array and Ni-clad Ti wires were fielded on the inner array.In this presentation, we will present analysis of data from other mixed Al/Ni-clad Ti configurations to further evaluate nested wire array dynamics and mass accretion. These additional configurations include the opposite configuration to that described above (Ni-clad Ti wires on the outer array, with Al wires on the inner array) as well as higher wire number Al configurations fielded to vary the interaction of the two arrays. These same variations were also assessed for a smaller diameter nested array configuration (40 mm). Variations in the emitted radiation and plasma conditions will be presented, along with a discussion of what the results indicate about the nested array dynamics. Additional evidence for mass accretion will also be presented.

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TYPE Conference YEAR 2010
OSTI

3-Dimensional modeling of large diameter wire array high intensity K-shell radiation sources

Jennings, Christopher A.; Ampleford, David A.; Hansen, Stephanie B.; Cuneo, M.E.; Coverdale, Christine A.; Jones, Brent M.

Large diameter nested wire array z-pinches imploded on the Z-generator at Sandia National Laboratories have been used extensively to generate high intensity K-shell radiation. Large initial radii are required to obtain the high implosion velocities needed to efficiently radiate in the K-shell. This necessitates low wire numbers and large inter-wire gaps which introduce large azimuthal non-uniformities. Furthermore, the development of magneto-Rayleigh-Taylor instabilities during the implosion are known to generate large axial non-uniformity These effects motivate the complete, full circumference 3-dimensional modeling of these systems. Such high velocity implosions also generate large voltages, which increase current losses in the power feed and limit the current delivery to these loads. Accurate representation of the generator coupling is therefore required to reliably represent the energy delivered to, and the power radiated from these sources. We present 3D-resistive MHD calculations of the implosion and stagnation of a variety of large diameter stainless steel wire arrays (hv {approx} 6.7 keV), imploded on the Z-generator both before and after its refurbishment. Use of a tabulated K-shell emission model allows us to compare total and K-shell radiated powers to available experimental measurements. Further comparison to electrical voltage and current measurements allows us to accurately assess the power delivered to these loads. These data allow us to begin to constrain and validate our 3D MHD calculations, providing insight into ways in which these sources may be further optimized.

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TYPE Conference YEAR 2010
OSTI

Wire array Z-pinch length variations for K-shell x-ray generation on Z

Jones, Brent M.; Hansen, Stephanie B.; Coverdale, Christine A.; Cuneo, M.E.; Ampleford, David A.; Jennings, Christopher A.

Large diameter (50-70 mm) wire array z pinches are fielded on the refurbished Z machine to generate 1-10 keV K-shell x-ray radiation. Imploding with velocities approaching 100 cm/{micro}s, these loads create large dL/dt which generates a high voltage, stresses the convolute, and leads to current loss. High velocities are required to reach the few-keV electron temperatures required to strip moderate-atomic-number plasmas to the K shell, thus there is an inherent trade-off between achieving high velocity and stressing the pulsed power driver via the large dL/dt.Here, we present experiments in which the length of stagnated Cu and stainless steel z pinches was varied from 12-24 mm. The motivation in reducing the pinch height is to lower the final inductance and improve coupling to the generator. Shortening a Cu pinch from 20 to 12 mm by angling the anode glide plane reduced the final L and dL/dt, enhancing the feed current by 1.4 MA, nearly doubling the K-shell power per unit length, and increasing the net K-shell yield by 20%. X-ray spectroscopy is employed to assess differences in plasma conditions between the loads. Lengthening the pinch could lead to yield enhancements by increasing the mass participating in the implosion, provided the increased inductance is not overly detrimental to the current coupling. In addition to the experimental results, these scenarios are studied via thin-shell 0D and also magneto-hydrodynamic modeling with a coupled driver circuit model.

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TYPE Conference YEAR 2010
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Two-dimensional radiation MHD K-shell modeling of stainless-steel double-wire-array experiments on the refurbished Z machine

IEEE Transactions on Plasma Science

Thornhill, J.W.; Giuliani, John L.; Dasgupta, Arati; Apruzese, John P.; Davis, Jack; Chong, Young K.; Jennings, Christopher A.; Ampleford, David A.; Jones, Brent M.; Coverdale, Christine A.; Jones, Brent M.; Cuneo, Michael E.; Stygar, W.A.

Two-dimensional (r, z) magnetohydrodynamic simulations with nonlocal thermodynamic equilibrium ionization and radiation transport are used to investigate the K-shell radiation output from doubly nested large-diameter (> 60 mm) stainlesssteel arrays fielded on the refurbished Z pulsed-power generator. The effects of the initial density perturbations, wire ablation rate, and current loss near the load on the total power, K-shell power, and K-shell yield are examined. The broad mass distribution produced by wire ablation largely overcomes the deleterious impact on the K-shell power and yield of 2-D instability growth. On the other hand, the possible current losses in the final feed section lead to substantial reductions in K-shell yield. Following a survey of runs, the parameters for the perturbation level, ablation rate, and current loss are chosen to benchmark the simulations against existing 65-mm-diameter radiation data. Themodel is then used to predict the K-shell properties of larger diameter (70 mm) arrays to be imploded on the Z generator. © 2010 IEEE.

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TYPE Journal Article YEAR 2010
ScopusOSTI

Investigation of radial wire arrays for inertial confinement fusion and radiation effects science

Ampleford, David A.; Jennings, Christopher A.; Cuneo, M.E.; McBride, Ryan D.; Sinars, Daniel S.; Jones, Brent M.; Coverdale, Christine A.; Jones, Michael J.

Radial wire arrays provide an alternative x-ray source for Z-pinch driven Inertial Confinement Fusion. These arrays, where wires are positioned radially outwards from a central cathode to a concentric anode, have the potential to drive a more compact ICF hohlraum. A number of experiments were performed on the 7MA Saturn Generator. These experiments studied a number of potential risks in scaling radial wire arrays up from the 1MA level, where they have been shown to provide similar x-ray outputs to larger diameter cylindrical arrays, to the higher current levels required for ICF. Data indicates that at 7MA radial arrays can obtain higher power densities than cylindrical wire arrays, so may be of use for x-ray driven ICF on future facilities. Even at the 7MA level, data using Saturn's short pulse mode indicates that a radial array should be able to drive a compact hohlraum to temperatures {approx}92eV, which may be of interest for opacity experiments. These arrays are also shown to have applications to jet production for laboratory astrophysics. MHD simulations require additional physics to match the observed behavior.

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TYPE SAND Report YEAR 2010
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Astrophysical jets with conical wire arrays : radiative cooling, rotation & deflection

Ampleford, David A.; Jennings, Christopher A.

Highly collimated outflows or jets are produced by a number of astrophysical objects including protostars. The morphology and collimation of these jets is thought to be strongly influenced by the effects of radiative cooling, angular momentum and the interstellar medium surrounding the jet. Astrophysically relevant experiments are performed with conical wire array z-pinches investigating each of these effects. It is possible in each case to enter the appropriate parameter regime, leading the way towards future experiments where these different techniques can be more fully combined.

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TYPE Conference YEAR 2008
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Results 201–290 of 290
Results 201–290 of 290