Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012; Providence, Rhode Island
Session BO5: Target Charging and Wire Array Z-pinches |
Hide Abstracts |
Chair: Kyle Peterson, Sandia National Laboratories Room: 552AB |
Monday, October 29, 2012 9:30AM - 9:42AM |
BO5.00001: An empirical target discharging model for direct-drive implosions on OMEGA N. Sinenian, M.J.-E. Manuel, J.A. Frenje, F.H. Seguin, C.K. Li, R.D. Petrasso, V. Goncharov, J. Delettrez, C. Stoeckl, T.C. Sangster, J. Cobble Capsule charging of inertial confinement fusion (ICF) targets, observed previously on OMEGA, is detrimental to achieving the high areal densities ($\rho $R) required for ignition and gain. This is because the target potential traps energetic electrons that can preheat the fuel, raise the adiabat and degrade compression. The decay-time of this potential is therefore an important parameter for preheat calculations. A non-linear model of the electrical discharging of ICF capsules has been developed. The empirical model, which captures the essential dynamics of the target voltage decay, incorporates previous charged-particle spectroscopic and radiographic measurements of the fields. It is shown that return currents through the target support fiber have a profound effect on the voltage-decay time. Implications of these findings for inertial fusion energy (IFE) are considered. This work was supported in part by DOE, LLE and LLNL. [Preview Abstract] |
Monday, October 29, 2012 9:42AM - 9:54AM |
BO5.00002: Mapping kA Return Currents in Laser-generated Z-pinch Plasmas M.J.-E. Manuel, N. Sinenian, F.H. S\'eguin, C.K. Li, J.A. Frenje, H.G. Rinderknecht, D.T. Casey, A.B. Zylstra, R.D. Petrasso, M. Fatenejad, F.N. Beg During capsule irradiation ``hot'' electrons leave the capsule and a residual positive charge is left on the target. The positive potential, of order 10$^{6}$ V, drives a return current through the supporting stalk structure. The first measurements of the spatial extent and magnitude of these return currents were conducted using monoenergetic proton deflectometry. From the measured proton fluence radiographs an absolute current was inferred and shown to increase from $\sim $2 kA to $\sim $7 kA during a picketed laser pulse. These images also demonstrate that current begins near the stalk surface and move outward in a similar manner to a single exploding wire Z-pinch. The work described here was done as part of the first author's PhD thesis and supported in part by NLUF (DE-NA0000877), FSC/UR (415023-G), DoE (DE-FG52-09NA29553), LLE (414090-G), and LLNL (B580243). [Preview Abstract] |
Monday, October 29, 2012 9:54AM - 10:06AM |
BO5.00003: Aluminum Wire Array Experiments on the Z Generator D.J. Ampleford, S.B. Hansen, C.A. Jennings, B. Jones, M.E. Cuneo, R.W. Clark, Y.K. Chong, J. Apruzese, J.L. Giuliani Wire array Z-pinches consisting of Al wires are a bright source of $>1$~keV emission. We discuss data from recent experiments with large diameter Al wire array Z-pinches on the Z generator. Wire arrays at 40mm, 50mm and 65mm were imploded on the Z generator. Soft x-ray self-emission imaging is used to study the implosion dynamics. Spectroscopy is used to diagnose plasma conditions as material stagnates on the axis. Data indicates significant free-bound continuum emission is present. We will discuss the variation in plasma conditions and emission characteristics as the initial wire array setup is varied. [Preview Abstract] |
Monday, October 29, 2012 10:06AM - 10:18AM |
BO5.00004: ABSTRACT WITHDRAWN |
Monday, October 29, 2012 10:18AM - 10:30AM |
BO5.00005: Optical Spectroscopic Measurements of the Z Machine Power Flow Region Matthew Gomez, Ron Gilgenbach, Mike Cuneo, Ryan McBride, Greg Rochau, Brent Jones, Dave Ampleford, Dan Sinars, Jim Bailey, Bill Stygar, Mark Savage, Michael Jones, Aaron Edens, Mike Lopez, E. Stambulchik, Y. Maron, Dave Rose, Dale Welch Pulsed power machines typically utilize vacuum transmission lines to deliver energy to the load. Large-scale drivers often employ several parallel transmission lines to reduce inductance. Post-hole convolutes can be used to combine the current from the transmission lines at the load. Losses in the post-hole convolute and vacuum transmission lines on the Z-machine are as high as 20{\%} of the peak current. Spectroscopic measurements of the plasma that forms on the power flow surfaces are underway. A second visible spectroscopy system has been added to the Z diagnostic suite, which allows symmetry measurements of the plasma formation. Investigations of the convolute plasma origin and propagation are ongoing. *Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Monday, October 29, 2012 10:30AM - 10:42AM |
BO5.00006: Study of instabilities in wire-array Z pinches at stagnation V.V. Ivanov, J.P. Chittenden, R.C. Mancini, D. Papp, N. Niasse, S.D. Altemara, A.A. Anderson Stagnation of the wire array Z pinches was studied at a 1 MA generator with imaging UV and x-ray diagnostics. Cylindrical, linear, and star wire-array Z pinches present different sets of instabilities seeded to the pinch during implosion. Compact cylindrical wire arrays implode to Z-pinches with $m=$0 necks associated with bright spots on x-ray images. The electron temperature of bright spots measured with K-shell spectroscopy is higher by 20-40{\%} compared to cold areas. Maximum x-ray power is generated by Z pinches with strong instabilities. Fast plasma motion with a velocity $>$100 km/s was observed in the Z pinch at stagnation with two-frame shadowgraphy. Plasma instabilities may present a mechanism for conversion of magnetic energy to kinetic energy. Comparison of the implosions in small-diameter cylindrical and star wire array shows that the secondary implosion of non-imploded peripheral plasma prolongs the stagnation stage and provides the enhanced x-ray production. Development of instabilities in wire arrays is in agreement with 3D MHD Gorgon simulations. [Preview Abstract] |
Monday, October 29, 2012 10:42AM - 10:54AM |
BO5.00007: Theoretical Investigation of Radiation Characteristics of Silver Z-pinch Arrays with Applications M.E. Weller, A.S. Safronova, V.L. Kantsyrev, A.A. Esaulov, I. Shrestha, G.C. Osborne, V.V. Shlyaptseva, S.F. Keim, A. Stafford, E.E. Petkov, A.S. Chuvatin, J.P. Apruzese, I.E. Golovkin, J.J. MacFarlane Experiments of Ag planar wire array z-pinches have been carried out on the 1.7 MA Zebra generator at UNR and produced L-shell plasmas with electron temperatures exceeding 1.8 keV and total radiated energy upwards of 30 kJ, which is of interest for radiation physics studies. Recently, an important question about such Ag plasmas is whether lasing occurs in the Na-like and Ne-like soft x-ray range, and if so, at what gains was considered. To this end, level populations were used from modified SCRAM to calculate theoretical lasing gains for Ne-like Ag. In addition, HELIOS-CR from PRISM was utilized for 1D MHD calculations for simple cylindrical Ag configurations. The importance of the study of Ag planar wire arrays is discussed. [Preview Abstract] |
Monday, October 29, 2012 10:54AM - 11:06AM |
BO5.00008: Experiments and Numerical Simulation on a New Hohlraum Configuration with Planar Wire Array Sources at the 1.7 MA Zebra Generator V.L. Kantsyrev, A.S. Chuvatin, L.I. Rudakov, A.S. Safronova, A.A. Esaulov, I. Shrestha, G.C. Osborne, V.V. Shlyaptseva, M.E. Weller, S.F. Keim, A. Stafford, B. Jones, R.A. Vesey In new hohlraum configuration, multiple mm-size planar wire array (PWA) sources surround a central cavity [B. Jones et al., PRL, v.104 (2010)]. This might provide a hotter hohlraum for ICF than the prior double-ended scheme with cylindrical arrays. The current redistribution in two magnetically decoupled compact Z-pinches (0.75-0.82 MA each) was demonstrated at 1.7 MA UNR Zebra generator. Yield measurements from two cages with PWA sources show that such plasma dissipates the magnetic energy at stagnation as a resistor. For the first time, strong EUV radiation, that time-correlated with sub-keV source bursts, was registered from central cavity. The experimental cavity radiation temperature of 37-45 eV correlates well with 39 eV from VisRaD code (PRISM Co.) simulation. First results of new configuration optimization are reported. The possible applications for 30-60 MA ICF experiments are discussed. This work was supported by NNSA under DOE Coop. Agr. DE-FC52-06NA27586, 06NA27588, and in part by DE-FC52-06NA27616. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Monday, October 29, 2012 11:06AM - 11:18AM |
BO5.00009: Larger Size Planar Wire Arrays with a Modified Central Plane and Their Applications on Zebra with LCM A.S. Safronova, A.A. Esaulov, V.L. Kantsyrev, A.S. Chuvatin, C.A. Coverdale, B. Jones, V.V. Shlyaptseva, M.E. Weller, A. Stafford, I. Shrestha, G.C. Osborne, S.F. Keim The increase in current up to 1.7 MA on Zebra with a Load Current Multiplier (LCM) allows implosions of larger size wire arrays compared to loads at 1 MA. In the previous experiments without LCM, different planar wire arrays (PWA) were tested, all with distance between the outer planes of 6 mm or less. Recently, we collected and analyzed the results of implosions of complex PWAs with a larger distance of 9 mm between outer planes, allowing better diagnostic access to early-time plasma flows near the stagnation axis. In particular, Triple PWAs with outer planes from mid-Z material and with a modified central plane from Al, were investigated. Different designs of the central Al plane were used to exclude magnetic field from the central volume. Shadowgraphy images show formation of stationary shock waves which existed over tens of ns. Time-gated spectroscopy indicates for the first time emissions from both Al K- and Ni L-shell plasmas as early as 20 ns before the main x-ray burst. This work was supported by NNSA under DOE Coop. Agr. DE-FC52-06NA27588, 06NA27586, and in part by DE-FC52-06NA27616. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Monday, October 29, 2012 11:18AM - 11:30AM |
BO5.00010: Shell-Like Loads and Spherical Arrays Driven by a Two-Stage Wire-Array Configuration Gareth Hall, Sergey Lebedev, Essa Khoory, Jeremy Chittenden, Francisco Suzuki-Vidal, George Swadling, Simon Bland, Adam Harvey-Thompson, Guy Burdiak, Philip de Grouchy, Louisa Pickworth, Jonathan Skidmore, Lee Suttle, Matthew Bennett Experiments were carried out on the MAGPIE facility, which delivers a 1.4MA current pulse with a rise time of 240ns. In a two-stage wire-array configuration, an inverse array [1] is used to pre-conditioned the wires of an imploding array before acting as a fast current switch to provide a drive current of $\sim $1MA with a rise time of $\sim $100ns. Pre-conditioned imploding arrays driven in this way do not exhibit the familiar extended ablation phase but instead display 0D-like implosion dynamics [2]. We will present an investigation of the modifications to implosion dynamics that can be achieved through utilization of the pre-conditioning technique. Examples include the creation of shell-like loads through the merging of neighboring pre-conditioned wires prior to implosion, and the implosion of pre-conditioned spherical arrays. This research was sponsored by the DOE under Cooperative Agreements DE-F03-02NA00057 and the Imperial College Junior Research Fellowship scheme.\\[4pt] [1] A. Harvey-Thompson et al., PoP 16, 022701 (2009). \\[0pt] [2] A. Harvey-Thompson et al., PRL 106, 205002 (2011) [Preview Abstract] |
Monday, October 29, 2012 11:30AM - 11:42AM |
BO5.00011: End-On Laser Interferometry of Wire Array Z-Pinch Implosions on the MAGPIE Generator G. Swadling, S.V. Lebedev, S. Patankar, A. Harvey-Thompson, F. Suzuki-Vidal, G.N. Hall, S.N. Bland, G. Burdiak, J.P. Chittenden, P. de Grouchy, J. Skidmore, L. Pickworth, L. Suttle, M. Bennett, R.A. Smith End-On interferometric measurements of the electron density distribution of wire array z-pinches has revealed striking differences in the behavior of ablation plasmas. A change in wire material from aluminum to tungsten results in a change from a highly collisional structure dominated by shock formations to a much less collisional regime. Analysis of the results will be presented and comparisons made to both simulations produced using the GORGON MHD code, and calculations of the expected mean-free-path of the plasma. Experiments were carried out on the MAGPIE generator (1.4 MA peak, 240ns rise) at Imperial College, London. A two-color Mach-Zender imaging interferometer was used to collect the data. This uses the 2$^{nd}$ and 3rd harmonics (532nm and 355nm) of a pulsed Nd:YAG laser with a pulse duration of $\sim $500ps. [Preview Abstract] |
Monday, October 29, 2012 11:42AM - 11:54AM |
BO5.00012: Predictions of non-LTE spectra from large scale 3D magneto-hydrodynamic modelling of wire array Z-pinches Nicolas Niasse, Jeremy Chittenden The last few years have seen considerable advances in the application of high performance computing techniques to 3D simulations of wire array Z-pinches. Whilst the intense soft X-ray radiation output is the principle application of wire arrays, the ability to encompass spectrally detailed models of this emission within such 3D calculations was thought to be computationally prohibitive. We have developed a non-LTE atomic and radiation physics model with detailed configuration accounting and n-l splitting which is sufficiently streamlined to run in-line with large scale 3D simulations. In order to handle the volume of data generated by the spectral treatment of the billions of numerical cells, a novel data structure derived from a self-balancing binary search tree was developed, enabling the use of non-LTE DCA calculations within large scale 3D simulations for the first time. A brief description of the model is provided and the application of the simulations to understanding the X-ray generation processes within wire array Z-pinches on the Z generator at Sandia National Laboratory is reported. The contribution of the ion temperature and the motion of the unstable plasma at stagnation to the Doppler widths of the lines is described in detail. [Preview Abstract] |
Monday, October 29, 2012 11:54AM - 12:06PM |
BO5.00013: Hybrid X Pinches at 1.2 MA Tatiana A. Shelkovenko, Sergey A. Pikuz, Adam D. Cahill, Cad L. Hoyt, David A. Hammer, Ivan N. Tilikin, Sergey N. Mishin, Albert R. Mingaleev A hybrid X-pinch (HXP) configuration consisting of solid conical electrodes connected by a wire as a central load has been tested on four different generators with currents varying from 200 kA to 1.2 MA and risetimes ranging from 50 ns to 170 ns. It was possible to optimize the wire material, length and diameter so that most of these HXPs generated an intense single burst of soft x-rays with energy yield comparable with that produced by standard X pinches. This configuration is useful primarily for pulsers with MA current level and was suggested to simplify standard wire X-pinch configurations with many wires. Wires as well as hollow and filled tubes made of Al, Ni and polyethylene were tested as a load on the COBRA pulser (1.2 MA, 100 ns rise time). The filled tubes expand the range of materials that can be studied under extreme conditions. Electron beams generation in HXPs has also been studied. [Preview Abstract] |
Monday, October 29, 2012 12:06PM - 12:18PM |
BO5.00014: Investigation of the interaction between a supersonic, radiatively cooled, plasma jet with metallic foil targets Louisa Pickworth, Sergey Lebedev, Francisco Suzuki-Vidal, Simon Bland, Gareth Hall, George Swadling, Matteo Bocchi, Guy Burdiak, John Skidmore, Phil de Grouchy, Lee Suttle, Mathew Bennett, Siddharth Patankar, Jerry Chittenden, Nicolas Niasse, A. Frank Presenting results from an experimental investigation into the interaction of supersonic, radiatively cooled plasma jets with solid targets. The jet is produced with a converging plasma flow from a radial foil array driven by 1.4MA, 240ns current pulse on the MAGPIE Z-pinch. The produced jet has scalable characteristics (Mach number of 20) that allow exploration of astrophysically relevant shock structures arising from the jets interaction with the target and pre ionized material from the target. The interaction with a foil target of the supersonic jet produces a reverse shock which has been initially documented with several diagnostics. These include; laser imaging and interferometry at 532nm and 355nm, spectroscopic analysis in both the optical and XUV regime, and Thompson probing through the target using the CERBERUS laser beam line to give spatially localized ion/electron plasma temperature in the shock front. [Preview Abstract] |
Monday, October 29, 2012 12:18PM - 12:30PM |
BO5.00015: Energetic cavitation collapse: tabletop high energy density once per minute with $\sim $1 J, $\sim $1 kW driver Marc Ramsey, Robert Pitz Liquid water is compressed to high energy density in an efficient and precisely controlled cavitation event with a repetition rate up to several times per minute. A vapor bubble of radius 1-2 mm is driven to collapse with a uniform pressure of 2-20 bar provided by a symmetric array of pulsed piezo-electric transducers, resulting in total kinetic energy of 1 to 100 mJ. Spherical symmetry is maintained to a convergence ratio of at least 100. Prior to stagnation a plasma is generated at a radius of 10-40 $\mu $m which persists for 2-10 ns over the range of collapse energies. In all cases, light emission begins abruptly (rise time $<$ 1 ns) in the liquid just outside the bubble wall when it reaches a velocity of 4 km/s and acceleration above 10$^{15}$ m/s$^{2}$ . At this point, inertial forces have adiabatically compressed the water to a pressure of roughly one megabar. The remainder of the collapse is obscured within this opaque plasma, which emits at a blackbody temperature above 5500 K. However, based on the final size of the cavity observed after the plasma quenches, it can be inferred that the implosion proceeds to significantly higher velocity higher before stagnation and emission of a strong shock wave. Diagnostic data to be presented includes 80 MHz 2D imaging and sub-ns time resolved spectral and spatial streak imaging. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700