Bulletin of the American Physical Society
57th Annual Meeting of the APS Division of Plasma Physics
Volume 60, Number 19
Monday–Friday, November 16–20, 2015; Savannah, Georgia
Session NO4: Magnetized Inertial Confinement Fusion II |
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Chair: Dan Sinars, Sandia National Laboratories Room: 105/106 |
Wednesday, November 18, 2015 9:30AM - 9:42AM |
NO4.00001: The PLX-$\alpha$ project: demonstrating the viability of spherically imploding plasma liners as an MIF driver S.C. Hsu, F.D. Witherspoon, J.T. Cassibry, M. Gilmore, R. Samulyak, P. Stoltz Under ARPA-E's ALPHA program, the Plasma Liner Experiment-ALPHA (PLX-$\alpha$) project aims to demonstrate the viability and scalability of spherically imploding plasma liners as a standoff, high-implosion-velocity magneto-inertial-fusion (MIF) driver [1] that is potentially compatible with both low- and high-$\beta$ targets. The project has three major objectives: (a) advancing existing contoured-gap coaxial-gun technology to achieve higher operational reliability/precision and better control/reproducibility of plasma-jet properties and profiles; (2) conducting $\sim \pi/2$-solid-angle plasma-liner experiments with 9 guns to demonstrate (along with extrapolations from modeling) that the jet-merging process leads to Mach-number degradation and liner uniformity that are acceptable for MIF; and (3) conducting $4\pi$ experiments with up to 60 guns to demonstrate the formation of an imploding spherical plasma liner for the first time, and to provide empirical ram-pressure and uniformity scaling data for benchmarking our codes and informing us whether the scalings justify further development beyond ALPHA\@. This talk will provide an overview of the PLX-$\alpha$ project as well as key research results to date.\\[4pt] [1] S. C. Hsu et al., IEEE Trans.\ Plasma Sci.~{\bf 40}, 1287 (2012). [Preview Abstract] |
Wednesday, November 18, 2015 9:42AM - 9:54AM |
NO4.00002: Coaxial Plasma Gun Development for the ARPA-E PLX-$\alpha$ Project F. Douglas Witherspoon, Andrew Case, Samuel Brockington We describe the renewed effort to design and build coaxial plasma guns [1] appropriate for a scaling study of spherically imploding plasma liners as a standoff magneto-inertial-fusion driver under the ARPA-E Accelerating Low-Cost Plasma Heating And Assembly (ALPHA) program. HyperV joins LANL, UAH, UNM, BNL, and Tech-X to develop, build, operate and analyze a 60 plasma gun experiment using the existing PLX facility [2] at LANL. The guns will be designed to operate over a scaling range of operating parameters: 0.5--5.0 mg of Ar, Ne, N2, Kr, and Xe; 20--60 km/s; $10^{16}-10^{17}$ cm$^{-3}$ muzzle density; and up to 7.5 kJ stored energy per gun. Each gun is planned to incorporate contoured gaps, fast dense gas injection and triggering, and innovative integral sparkgap switching and pfn configurations to reduce inductance, cost, and complexity, and to increase efficiency and system reliability. We will describe the overall design approach for the guns and pulsed power systems.\\[4pt] [1] Witherspoon et al., Rev. Sci. Instr. \textbf{80}, 083506 (2009).\\[0pt] [2] Hsu et al., IEEE Trans. on Plas. Sci. \textbf{40}, No. 5, May 2012. [Preview Abstract] |
Wednesday, November 18, 2015 9:54AM - 10:06AM |
NO4.00003: Modeling of the merging, liner formation, implosion of hypervelocity plasma jets for the PLX-$\alpha$ project Jason Cassibry, Scott Hsu, Kevin Schillo, Roman Samulyak, Peter Stoltz, Kris Beckwith A suite of numerical tools will support the conical and 4$\pi $ plasma-liner-formation experiments for the PLX-$\alpha $ project. A new Lagrangian particles (LP) method will provide detailed studies of the merging of plasma jets and plasma-liner formation/convergence. A 3d smooth particle hydrodynamic (SPH) code will simulate conical (up to 9 jets) and 4$\pi $ spherical (up to 60 jets) liner formation and implosion. Both LP and SPH will use the same tabular EOS generated by Propaceos, thermal conductivity, optically thin radiation and physical viscosity models. With LP and SPH,the major objectives are to study Mach-number degradation during jet merging, provide RMS amplitude and wave number of the liner nonuniformity at the leading edge, and develop scaling laws for ram pressure and liner uniformity as a function of jet parameters. USIM, a 3D multi-fluid plasma code, will be used to perform 1D and 2D simulations of plasma-jet-driven magneto-inertial fusion (PJMIF) to identify initial conditions in which the ``liner gain'' exceeds unity. A brief overview of the modeling program will be provided. Results from SPH modeling to support the PLX- $\alpha $ experimental design will also be presented, including preliminary ram-pressure scaling and non-uniformity characterization. [Preview Abstract] |
Wednesday, November 18, 2015 10:06AM - 10:18AM |
NO4.00004: Simulation of Plasma Jet Merger and Liner Formation within the PLX-$\alpha$ Project Roman Samulyak, Hsin-Chiang Chen, Wen Shih, Scott Hsu Detailed numerical studies of the propagation and merger of high Mach number argon plasma jets and the formation of plasma liners have been performed using the newly developed method of Lagrangian particles (LP). The LP method significantly improves accuracy and mathematical rigor of common particle-based numerical methods such as smooth particle hydrodynamics while preserving their main advantages compared to grid-based methods. A brief overview of the LP method will be presented. The Lagrangian particle code implements main relevant physics models such as an equation of state for argon undergoing atomic physics transformation, radiation losses in thin optical limit, and heat conduction. Simulations of the merger of two plasma jets are compared with experimental data from past PLX experiments. Simulations quantify the effect of oblique shock waves, ionization, and radiation processes on the jet merger process. Results of preliminary simulations of future PLX-$alpha$ experiments involving the $\sim \pi/2$-solid-angle plasma-liner configuration with 9 guns will also be presented. [Preview Abstract] |
Wednesday, November 18, 2015 10:18AM - 10:30AM |
NO4.00005: Stabilized Liner Compressor: The Return of Linus Peter Turchi, Sherry Frese, Michael Frese, Charles Mielke, Mark Hinrichs, Doan Nguyen To access the lower cost regime of magneto-inertial fusion at megagauss magnetic field-levels [1] requires the use of dynamic conductors in the form of imploding cylindrical shells, aka, liners. Such liner implosions can compress magnetic flux and plasma to attain fusion conditions, but are subject to Rayleigh-Taylor instabilities, both in the launch and recovery of the liner material and in the final few diameters of implosion. These instabilities were overcome in the Linus program at the Naval Research Laboratory, c. 1979, providing the experimentally-demonstrated basis for repetitive operation and leading to an economical reactor concept at low fusion gain [2]. The recent ARPA-E program for low-cost fusion technology has revived interest in this approach. We shall discuss progress in modeling and design of a Stabilized Liner Compressor (SLC) that extends the earlier work to higher pressures and liner speeds appropriate to potential plasma targets.\\[4pt] [1] P.J. Turchi, ``Imploding Liner Compression of Plasma: Concepts and Issues,'' IEEE Trans. on Plasma Science, 36, 1, 52 (2008).\\[0pt] [2] P.J. Turchi, et al, ``Review of the NRL Liner Implosion Program,'' in Megagauss Physics and Technology, P.J. Turchi, ed., Plenum, NY (1980). P. 375. [Preview Abstract] |
Wednesday, November 18, 2015 10:30AM - 10:42AM |
NO4.00006: Accelerated Taylor plumes for MIF targets M.R. Brown, D.A. Schaffner, H.L. Parks, A.B. Rock The SSX plasma device has been converted to a $2.5~m$ merging plasma wind tunnel configuration. Experiments are underway to study merging and stagnation of high density, helical Taylor states\footnote{Gray, et al, PRL {\bf 110}, 085002 (2013).} to employ as a potential target for magneto-inertial fusion. Eventually, SSX Taylor states will be accelerated to over $100~km/s$ and compressed to small volumes either by stagnation or merging. Initial un-accelerated merging studies produce peak proton densities of $5 \times 10^{15}~cm^{-3}$. Densities are measured with a precision quadrature He-Ne laser interferometer. Typical merged plasma parameters are $T_i = 20~eV, T_e= 10~eV, B = 0.4~T$ with lifetimes of $100~\mu s$. Results from a single prototype acceleration coil will be presented, as well as initial simulation studies of Taylor state plasma acceleration using multiple staged, pulsed theta-pinch coils. [Preview Abstract] |
Wednesday, November 18, 2015 10:42AM - 10:54AM |
NO4.00007: Microfabricated Ion Beam Drivers for Magnetized Target Fusion Arun Persaud, Peter Seidl, Qing Ji, Serhan Ardanuc, Joseph Miller, Amit Lal, Thomas Schenkel Efficient, low-cost drivers are important for Magnetized Target Fusion (MTF). Ion beams offer a high degree of control to deliver the required mega joules of driver energy for MTF and they can be matched to several types of magnetized fuel targets, including compact toroids and solid targets. We describe an ion beam driver approach based on the MEQALAC concept (Multiple Electrostatic Quadrupole Array Linear Accelerator) with many beamlets in an array of micro-fabricated channels. The channels consist of a lattice of electrostatic quadrupoles (ESQ) for focusing and of radio-frequency (RF) electrodes for ion acceleration. Simulations with particle-in-cell and beam envelope codes predict \textgreater 10x higher current densities compared to state-of-the-art ion accelerators. This increase results from dividing the total ion beam current up into many beamlets to control space charge forces. Focusing elements can be biased taking advantage of high breakdown electric fields in sub-mm structures formed using MEMS techniques (Micro-Electro-Mechanical Systems). We will present results on ion beam transport and acceleration in MEMS based beamlets. Acknowledgments: This work is supported by the U.S. DOE under Contract No. DE-AC02-05CH11231. [Preview Abstract] |
Wednesday, November 18, 2015 10:54AM - 11:06AM |
NO4.00008: Using a magnetized plasma jet colliding with a heavy gas cloud to investigate MIF adiabatic heating and compression mechanisms Paul Bellan, Pakorn Wongwaitayakornkul, Kil-Byoung Chai, Amelia Greig, Hui Li Magnetized inertial fusion (MIF) is based on having an imploding liner adiabatically compress a magnetized plasma to the density and temperature required for thermonuclear fusion. The goal of the Caltech research program is to determine the scaling of the temperature and density increase when an actual experimental plasma is adiabatically compressed. The plasma parameters will be more modest than a fusion-grade configuration, but in compensation, the shot repetition rate will be much higher and the experiments will be non-destructive. The non-destructive feature results from having a high-speed magnetized plasma jet impact a localized heavy gas. From the point of view of an observer in the frame of the magnetized plasma jet, it will look as if the heavy gas is impacting and compressing the magnetized plasma and so, except for some geometrical differences, the configuration is equivalent to a liner impacting and compressing a stationary magnetized plasma. The experiment will be modeled by 3D numerical MHD and PIC codes. [Preview Abstract] |
Wednesday, November 18, 2015 11:06AM - 11:18AM |
NO4.00009: Staged Z-pinch for Fusion Frank Wessel, Hafiz Rahman, Paul Ney, Tim Darling, Erik McKee, Aaron Covington, Farhat Beg, Julio Valenzuela, Jeff Narkis, Radu Presura The Staged Z-pinch (SZP)$\footnote{H. U. Rahman, F. J. Wessel, and N. Rostoker. Staged Z-pinch. PRL, 74:714, 1995}$ is configured as a plasma shell imploding onto an uniform, plasma fill (50:50 Deuterium:Tritium); the pinch is pre-magnetized, with an axial $B_z$ field. Gas-puff experiments, at the University of California, Irvine,$\footnote{F. J. Wessel, Staged Z-pinch, Final Report, DoE FG03-93ER544220, March 2000}$ 1.25 MA, 1.25 $ \mu$s, and 50 kJ, demonstrated that the implosion was stable, as primary (DD) and secondary (DT) neutrons were produced at peak compression. Subsequent analysis accounts for the stability and neutron yield, indicating that the SZP implosion is magneto-inertial, shock-driven, with magneto-sonic shocks in the liner and ordinary (sonic) shocks in the target. The shock waves preheat the target, as a stable, current-carrying, shock front forms at the interface. Near-term, the SZP team will test pinch loads on the 1 MA, 130 ns, 100 kJ University of Nevada, Reno, Nevada Terawatt, Zebra Facility. This paper details the context and our specific plans for the upcoming experiments, as well as our recent simulations predicting breakeven fusion on existing devices. [Preview Abstract] |
Wednesday, November 18, 2015 11:18AM - 11:30AM |
NO4.00010: Simulations for a Staged Z-pinch and MagLIF at 26 MA, 130 ns, and 22 MJ Hafiz Rahman, Frank Wessel, Paul Ney, Jeff Narkis, Julio Valenzuela, Farhat Beg, Radu Presura Simulations for a Staged Z-pinch (SZP),$\footnote{H. U. Rahman, F. J. Wessel, and N. Rostoker. Staged Z-pinch. PRL, 74:714, 1995}$ using a 6-mm diameter, 100-$\mu$m thick Silver plasma shell, imploding onto a uniform (target) plasma fill of Deuterium, are compared to MagLIF, configured similarly, except with a 500 $\mu$m Beryllium solid liner. Both pinches are pre-magnetized with: $B_z =$ 0, 3, 7, and 10 T and the driver parameters are: $\tau_{1/4}$ = 130 ns, $I_{peak}$ = 26 MA, $E_{stored}$ = 22 MJ; the simulation code is MACH2, a 2-1/2 D, radiation-MHD code. Solid-liner simulations reproduce well, experimental results.$\footnote{M. Gomez, et.al., Phys.Plasmas (22)056306:1-10, 2015}$ Plasma-liner simulations exhibit magnetosonic shocks in the liner and ordinary sonic shocks in the target, preheating the plasma. A conduction-channel, shock-front at the interface remains stable throughout compression, even as the liner's outer surface becomes RT unstable. At peak compression the target decelerates and interface instability appears, triggering ignition and a fusion yield of, $Y > 200$ MJ; that is, $10 \times$ greater than $E_{stored}$. The yield from the solid liner implosion is 4 orders-of-magnitude less, even though it is more stable than the SZP. [Preview Abstract] |
Wednesday, November 18, 2015 11:30AM - 11:42AM |
NO4.00011: Staged Z-pinch Simulations for the UNR, Nevada Terawatt Zebra Facility Paul Ney, Hafiz Rahman, Frank Wessel, Jeff Narkis, Julio Valenzuela, Farhat Beg, Radu Presura, Tim Darling, Erik Mckee, Aaron Covington We simulate a Staged Z-pinch$\footnote{H. U. Rahman, F. J. Wessel, and N. Rostoker. Staged Z-pinch. PRL, 74:714, 1995}$ imploded on the 1 MA, 130 ns, 100 kJ, Nevada Terawatt Zebra Facility. The load is a magnetized, cylindrical, double gas-puff, plasma liner imploding onto a plasma target. Simulations use the 2-1/2 D, radiation-MHD code, MACH2. Three different liner gases are evaluated: Ar, Kr, and Xe and the target is either: DD, or DT, with a liner-plasma radius of: 1.0 cm and 2.0 cm, and a 5.0-mm thickness. Initial conditions are optimized to produce the highest neutron yield. Shocks propagate at different speeds in the liner and target, leading to a shock front at the interface. Magnetosonic shock waves pre-heat the target plasma and provide a stable implosion. The shock front provides a secondary conduction channel which builds up during implosion. The axial magnetic field controls the MRT instability and traps $\alpha$-particles, leading to ignition. Magnetic flux is compressed, and at peak parameters the magnetic field and current density exceed, by an order of magnitude, values outside the pinch, providing a magneto-inertial confinement. A smaller radius provides $10^{2}-10^{3} \times$ higher neutron yield. [Preview Abstract] |
Wednesday, November 18, 2015 11:42AM - 11:54AM |
NO4.00012: Interaction of a Plasma Jet with a Magnetized Planar Obstacle A.M. Rasmus, M.J.-E. Manuel, C.C. Kuranz, S.R. Klein, J.S. Davis, R.P. Drake, D.S. Montgomery, S.C. Hsu, C.S. Adams, B.B. Pollock The propagation of high velocity plasma-jets into transverse magnetic fields has applications to pulsed power and fusion, as well as astrophysical processes, e.g. pulsed jets and the interaction of the solar wind with the magnetosphere. In experiments at the Trident Laser Facility at Los Alamos National Laboratory an Al plasma-jet propagated into a uniform, 4.5T, magnetic field produced by an electromagnet. The flow collided with a planar obstacle. Interferometry and Faraday rotation measured the path integrated electron density and magnetic field. Preliminary results from these diagnostics will be discussed. [Preview Abstract] |
Wednesday, November 18, 2015 11:54AM - 12:06PM |
NO4.00013: Turbulent amplification of magnetic fields in colliding laboratory jets P. Tzeferacos, J. Meinecke, A.R. Bell, H. Doyle, R. Bingham, E.M. Churazov, R. Crowston, C.D. Murphy, N.C. Woolsey, R.P. Drake, C.C. Kuranz, M.J. MacDonald, W.C. Wan, M. Koenig, A. Pelka, A. Ravasio, R. Yurchak, Y. Kuramitsu, Y. Sakawa, H.-S. Park, B. Reville, F. Miniati, A.A. Schekochihin, D.Q. Lamb, G. Gregori Turbulence and magnetic fields are ubiquitous in the universe. In galaxy clusters, turbulence is believed to amplify seed magnetic fields to values of a few $\mu $G, as observed through diffuse radio-synchrotron emission and Faraday rotation measurements. In this study we present experiments that emulate such a process in a controlled laboratory environment. Two laser-driven plasma flows collide to mimic the dynamics of a cluster merger. From the measured density fluctuations we infer the development of Kolmogorov-like turbulence. Measurements of the magnetic field show it is amplified by turbulent motions, reaching a non-linear regime that is a precursor to turbulent dynamo. We also present numerical simulations with the FLASH code that model these experiments. The simulations reproduce the measured plasma properties and enable us to disentangle and characterize the complex physical processes that occur in the experiment. This study provides a promising experimental platform to probe magnetic field amplification by turbulence in plasmas, a process thought to occur in many astrophysical phenomena. [Preview Abstract] |
Wednesday, November 18, 2015 12:06PM - 12:18PM |
NO4.00014: Production of high-beta magnetised plasmas by colliding supersonic flows from inverse wire arrays Jack Hare, Lee Suttle, Sergey Lebedev, Matthew Bennett, Guy Burdiak, Thomas Clayson, Francisco Suzuki-Vidal, George Swadling, Siddharth Patankar, Timothy Robinson, Nicholas Stuart, Roland Smith, Qingguo Yang, Jian Wu, Wojciech Rozmus HEDP often exhibit a high plasma $\beta$ and an electron Hall parameter greater than one. This results in a complex interplay between the transport of heat and magnetic fields, relevant to the Magnetised Liner Inertial Fusion (MagLIF) concept. We can produce such plasmas by colliding two supersonic quasi-planar flows from two adjacent inverse wire arrays made from carbon. The standing shock formed by the collision heats and compresses the plasma. The plasma flows advect magnetic fields which are perpendicular to the flow direction. Depending on the experimental set up, this can result in either flux compression or reconnection in the interaction region. The experiments are conducted on MAGPIE (1.4 MA, 250 ns current pulse). The formed shock is stable over long timescales ($\sim$100 ns), and the electron temperature (100 eV) is close to the ion temperature (500 eV), measured by spatially resolved Thomson scattering. Magnetic fields above 5 T is observed using a Faraday rotation diagnostic, and an electron density of around 5x10$^{17}$ cm$^{-3}$ is measured by interferometry. [Preview Abstract] |
Wednesday, November 18, 2015 12:18PM - 12:30PM |
NO4.00015: Compression and Cavitation of Externally Applied Magnetic Field on a Hohlraum due to Non-Local Heat Flow Effects Archis Joglekar, Alec Thomas, Chris Ridgers, Rob Kingham In this study, we present full-scale 2D kinetic modeling of externally imposed magnetic fields on hohlraums with laser heating. We observe magnetic field cavitation and compression due to thermal energy transport. Self-consistent modeling of the electron momentum equation allows for a complete treatment of the heat flow equation and Ohm's Law. A complete Ohm's Law contains magnetic field advection through the Nernst mechanism that arises due to the heat flow. Magnetic field amplification by a factor of 3 occurs due to magnetic flux pile-up from Nernst convection. The magnetic field cavitates towards the hohlraum axis over a 0.5 ns time scale due to Nernst convection. This results in significantly different magnetic field profiles and slower cavitation than can be expected due to the plasma bulk flow. Non-local electrons contribute to the heat flow down the density gradient resulting in an augmented Nernst convection mechanism that is included self-consistently through kinetic modeling. In addition to showing the prevalence of non-local heat flows, we show effects such as anomalous heat flow up the density gradient induced by inverse bremsstrahlung heating. [Preview Abstract] |
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