Bulletin of the American Physical Society
58th Annual Meeting of the APS Division of Plasma Physics
Volume 61, Number 18
Monday–Friday, October 31–November 4 2016; San Jose, California
Session BO8: Magneto-Inertial Fusion I |
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Chair: Jonathan Davies, University of Rochester Room: 212 CD |
Monday, October 31, 2016 9:30AM - 9:42AM |
BO8.00001: The PLX-$\alpha$ Project: Progress and Plans S. Hsu, F. D. Witherspoon, J. Cassibry, M. Gilmore, R. Samulyak, P. Stoltz The Plasma Liner Experiment-ALPHA (PLX-$\alpha$) project aims to demonstrate the viability of spherically imploding plasma liners as a standoff driver for plasma-jet-driven magneto-inertial fusion (PJMIF) [Hsu et al., IEEE Trans. Plasma Sci.~{\bf 40}, 1287 (2012)]. In the past year, progress has been made in designing and testing new contoured-gap coaxial guns, 3D model development and simulations (via Eulerian and Lagrangian hydrocodes) of PLX-$\alpha$-relevant plasma-liner formation/implosion via up to 60 plasma jets ($\sim 100$~kJ of liner kinetic energy), 1D semi-analytic and numerical modeling of reactor-scale PJMIF (10s of MJ of liner kinetic energy), and preparation/upgrade of the PLX facility/diagnostics. The design goal for the coaxial guns is to form plasma jets of up to initial $n \sim 2\times 10^{16}$~cm$^{-3}$, mass $\approx 5$~mg, $V_{jet}\approx 50$~km/s, $r_{jet}=4$~cm, and length $\approx 10$~cm. The modeling research is assessing ram-pressure amplification and Mach-number degradation during liner convergence, evolution of liner non-uniformity amplitude and mode number, and exploration of PJMIF configurations with promising 1D and 2D fusion gains. Conical multi-jet-merging and full-4$\pi$ experiments will commence in Fall, 2016 and late 2017, respectively. [Preview Abstract] |
Monday, October 31, 2016 9:42AM - 9:54AM |
BO8.00002: Coaxial-gun design and testing for the PLX-$\alpha$ Project F. Douglas Witherspoon, Samuel Brockington, Andrew Case, Edward Cruz, Marco Luna, Samuel Langendorf We describe the Alpha coaxial gun designed for a 60-gun scaling study of spherically imploding plasma liners as a standoff driver for plasma-jet-driven magneto-inertial fusion (PJMIF) [1]. The guns operate over a range of parameters: 0.5-5.0 mg of Ar, Ne, N2, Kr, and Xe; 20-60 km/s; $\sim$2$\times$ 10$^{16}$~cm$^{-3}$ muzzle density; and up to 7.5 kJ stored energy per gun. Each coaxial gun incorporates a fast dense gas injection and triggering system, a compact low-weight pfn with integral sparkgap switching, and a contoured gap designed to suppress the blow-by instability [2]. The latest design iteration incorporates a faster more robust gas valve, an improved electrode contour, a custom 600-$\mu$F, 5-kV pfn, and six inline sparkgap switches operated in parallel. The switch and pfn are mounted directly to the back of the gun and are designed to reduce inductance, cost, and complexity, maximize efficiency and system reliability, and ensure symmetric current flow. We provide a brief overview of the design choices, the projected performance over the parameter ranges mentioned above, and experimental results from testing of the PLX-$\alpha$ coaxial gun. [1] Hsu et al., IEEE Trans. Plasma Sci.~{\bf 40}, 1287 (2012). [2] Witherspoon et al., Rev. Sci. Instr. \textbf{80}, 083506 (2009). [Preview Abstract] |
Monday, October 31, 2016 9:54AM - 10:06AM |
BO8.00003: Simulations of Plasma-Liner Formation and Implosion for the PLX-$\alpha$ Project Roman Samulyak, Jason Cassibry, Kevin Schillo, Wen Shih, Kevin Yates, Scott Hsu Detailed numerical studies of the propagation and merger of high-Mach-number plasma jets and the formation and implosion of plasma liners have been performed using the FronTier and SPH codes enhanced with radiation, physical diffusion, and plasma-EOS models. These simulations support the Plasma Liner Experiment-ALPHA (PLX-$\alpha$) project (see S. Hsu’s talk in this session). Simulations predict properties of plasma liners, in particular 4$\pi$-averaged liner density, ram pressure, and Mach number, the degree of non-uniformity, strength of primary and secondary shock waves, and scalings with the number of plasma jets, initial jet parameters, and other input data. In addition to direct analysis of liner states, simulations also provide synthetic data for direct comparison to experimental data from a multi-chord interferometer and survey and high-resolution spectrometers. Code verification and comparisons as well as predictions for the first series of PLX-$\alpha$ experiments with 6 and 7 jets will be presented. Verified against experimental data, both codes will be used for predictive simulations of plasma liners for PLX-$\alpha$ experiments and potential scaled-up future experiments. [Preview Abstract] |
Monday, October 31, 2016 10:06AM - 10:18AM |
BO8.00004: Radiation-MHD Simulations of Plasma-Jet-Driven Magneto-Inertial Fusion Gain Using USim Peter Stoltz, Kristian Beckwith, Mahdusudhan Kundrapu, Scott Hsu, Samuel Langendorf One goal of the modeling effort for the PLX-$\alpha$ project is to identify plasma-jet-driven magneto-inertial fusion (PJMIF) [Hsu et al., IEEE Trans. Plasma Sci.~{\bf 40}, 1287 (2012)] configurations with potential net fusion-energy gain. We use USim, which is a tool for modeling high-energy-density plasmas using multi-fluid models coupled to electromagnetics using fully-implicit iterative solvers, combined with finite volume discretizations on unstructured meshes. We include physical viscosity and advanced-EOS modeling capability, and are investigating the effects of different radiation (including flux-limited diffusion) and alpha-transport models. We compare 2D and 1D gain calculations [Knapp, C. E. and Kirkpatrick, R. C., Physics of Plasmas, ~{\bf 21}, 070701 (2014)] for various liner geometries, parameters, and plasma species, and consider the effects of liner non-uniformities on fusion-gain degradation. [Preview Abstract] |
Monday, October 31, 2016 10:18AM - 10:30AM |
BO8.00005: Characterization of Taylor plumes on SSX M. R. Brown, M. Kaur, J. Han, J. E. Shrock, D. A. Schaffner We have added a $1~m$ glass extension to the SSX plasma wind tunnel device. Initial experiments have been performed to characterize velocity, density, and magnetic field of relaxed helical Taylor states$^*$ formed in the glass boundary. We are also experimenting with resistive and mesh liners to provide some flux conservation of the Taylor states. Under construction is a theta pinch coil and pulsed power supply to accelerate the fully relaxed (tilted) Taylor states. Once characterization studies are complete, one or two prototype theta pinch coils will be used to accelerate the Taylor states to over $100~km/s$ and compressed to small volumes by stagnation. A segmented resistive or mesh flux conserver may also be employed. Preliminary un-accelerated characterizaton studies produce peak proton densities of $10^{15}~cm^{-3}$. Densities are measured with a precision quadrature He-Ne laser interferometer located in an expansion volume downstream of the glass extension. Temperatures will be measured by an ion Doppler spectrometer. Stagnated plasma parameters will be $n_e \approx 10^{16}~cm^{-3}$ with $T_i \ge 20~eV, B \ge 0.5~T$ with lifetimes over $100~\mu s$. Results from a single prototype acceleration coil will be presented. * Gray, et al, PRL {\bf 110}, 085002 (2013). [Preview Abstract] |
Monday, October 31, 2016 10:30AM - 10:42AM |
BO8.00006: Velocity and magnetic field measurements of Taylor plumes in SSX under different boundary conditions Manjit Kaur, M. R. Brown, J. Han, J. E. Shrock, D. A. Schaffner The SSX device has been modified by the addition of a $1~m$ long glass extension for accommodating pulsed theta pinch coils. The Taylor plumes$^*$ are launched from a magnetized plasma gun and flow to an expansion volume downstream. The time of flight (TOF) measurements of these plumes are carried out using a linear array of $\dot B$ probes (separated by $10~cm$). TOF of the plasma plumes from one probe location to the next is determined by direct comparison of the magnetic field structures as well as by carrying out a cross-correlation analysis. With the glass boundary, the typical velocity of the Taylor plumes is found to be $\approx 25~km/s$, accompanied by a fast plasma ($\ge 50~km/s$) at the leading edge. Magnetic field embedded in the Taylor plumes is measured in the expansion chamber using a three-dimensional array of $\dot B$ probes and is found to be $\approx 700~G$. Some flux conservation of the Taylor plumes is provided by using a resistive (soak time $\approx 3~\mu s$) and a mesh (soak time $\approx 170~\mu s >$ discharge time) liner around the glass tube for improving the downstream Taylor state velocity as well as the magnetic field. The results from these different boundary conditions will be presented. * Gray, et al, PRL {\bf 110}, 085002 (2013). [Preview Abstract] |
Monday, October 31, 2016 10:42AM - 10:54AM |
BO8.00007: Replicating magneto-inertial fusion compression by colliding a magnetized plasma jet with a heavy gas cloud Amelia Greig, Paul Bellan, Hui Li The Caltech plasma jet experiment is arranged to have a neutral gas cloud in the path of a magnetized plasma jet. When a hydrogen jet collides with an argon gas cloud, the jet is compressed as argon is much heavier than hydrogen. The compression is equivalent to the Magnetized Inertial Fusion situation of a heavy liner compressing a low-density, magnetized plasma, providing an inexpensive analog for non-destructive studies of the plasma compression physics. The strategy is to measure density, magnetic field and temperature in and around the compression region over a range of parameters both with and without the neutral gas cloud in the path of the jet, with the ultimate goal of determining an equation of state characterizing the observed behavior. Initial density and magnetic field measurements have been made and temperature measurements are about to begin. To complement the experimental measurements, 3D numerical MHD simulation is being performed based on a code used previously to model the magnetized plasma jet experiment. In addition, plans are underway to do modeling using a hybrid code. [Preview Abstract] |
Monday, October 31, 2016 10:54AM - 11:06AM |
BO8.00008: Development of a Thomson scattering diagnostic for the Caltech jet-target experiment Byong Hoon Seo, Amelia Greig, Paul Bellan A Thomson scattering diagnostic is being developed for studying the Caltech jet-target impact experiment. This experiment has a high-speed MHD-driven jet impact a dense, high-mass target cloud. The compression of the jet upon impact simulates the compression of an imploding liner. A preliminary bench top system consisting of a low power laser, lenses, a beam rotator, a monochromator, and a PMT is being used for measuring the Rayleigh and eventually Raman scattering signals from atmospheric pressure N2 and O2. The laser is modulated at 500 Hz to 1 kHz and lock-in techniques are used to recover the low-amplitude signal. For the actual pulsed plasma experiment, the low-power laser will be replaced by a high power Nd:YAG laser. The detector will consist of a double monochromator consisting of two single monochromators separated by a mask in the focal plane to block Rayleigh scattered light; detection will be by an intensified, gated camera. The diagnostic will be used to study the compression and heating that occurs when the jet plasma collides with a dense, high mass target cloud. [Preview Abstract] |
Monday, October 31, 2016 11:06AM - 11:18AM |
BO8.00009: Scaling of the Sheared-Flow Stabilized Z-Pinch: The Fusion Z-Pinch Experiment "FuZE" B.A. Nelson, U. Shumlak, E.L. Claveau, R.P. Golingo, T.R. Weber, H.S. McLean, K.K. Tummel, D.P. Higginson, A.E. Schmidt The sheared flow stabilized (SFS) Z-pinch ZaP experiment was constructed based on calculations [1] showing stabilization of kink and sausage instabilities. ZaP experimentally demonstrated production and sustainment of an SFS Z-pinch for a wide range of plasma parameters, with densities up to $n=10^{23}$ m$^{-3}$ and a pinch radius of $a$=1 cm. [2-4] The SFS Z-pinch is resistant to the instabilities of conventional Z-pinches, yet maintains the same favorable radial scaling, making it an energy-efficient way to achieve fusion-relevant conditions. The ZaP-HD (high density) experiment has demonstrated scaling of the SFS Z-pinch to 2-3$\times$ smaller $a$ and 10$\times$ higher $n$. [5] Supported by ZaP and ZaP-HD, the Fusion Z-pinch Experiment (FuZE) project investigates scaling plasma parameters toward fusion conditions by decreasing $a$ 2-3$\times$ to 1 mm, and increasing $n$ 10$\times$ to 10$^{25}$ m$^{-3}$. The approach combines improved gas injection and flexible power supplies with the successful ZaP SFS Z-pinch formation. Detailed fluid and kinetic simulations complement the experimental studies to gain scientific insight into the plasma behavior and predict scaling to higher performance. [Preview Abstract] |
Monday, October 31, 2016 11:18AM - 11:30AM |
BO8.00010: A Reactor Development Scenario for the FUZE Shear-flow Stabilized Z-pinch H.S. McLean, D.P. Higginson, A. Schmidt, K.K. Tummel, U. Shumlak, B.A. Nelson, E.L. Claveau, R.P. Golingo, T.R. Weber We present a conceptual design, scaling calculations, and a development path for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device [U. Shumlak, et. al., Nucl. Fusion 49 (2009) 075039] have demonstrated stable operation for $\sim$40 us at $\sim$150kA total discharge current (with $\sim$100kA in the pinch) for pinches that are $\sim$1cm in diameter and 100 cm long. Scaling calculations show that achieving stabilization for a pulse of $\sim$100 usec, for discharge current $\sim$1.5 MA, in a shortened pinch $\sim$50 cm, results in a pinch diameter of $\sim$200 um and a reactor plant Q$\sim$5 for reasonable assumptions of the various system efficiencies. We propose several key intermediate performance levels in order to justify further development. These include achieving operation at pinch currents of $\sim$300 kA, where Te and Ti are calculated to exceed 1 keV, $\sim$700 kA where fusion power exceeds pinch input power, and 1 MA where fusion energy per pulse exceeds input energy per pulse. [Preview Abstract] |
Monday, October 31, 2016 11:30AM - 11:42AM |
BO8.00011: The Role of Magnetosonic Shocks in the Dynamics and Stability of the Staged Z-pinch Hafiz U. Rahman, F. J. Wessel, E. Ruskov, P. Ney, J. Narkis, J. Valenzuela, F. Conti, F. Beg A Staged Z-pinch$\footnote{H. U. Rahman, et. al., Phys.Rev.Lett.$\bf74$, 714 (1995)}, \footnote{F. J. Wessel, et. al. AIP Conf. Proc. 1721, 060002 (2016)}$ is comprised of a magnetized, high-Z liner compressing a low-Z target and is predicted to achieve high, final-energy-density through enhanced stability, shock heating, and flux compression. Magnetosonic waves propagate radially in the system producing a stable, current carrying shock front that heats the target plasma during run-in, prior to inertial-adiabatic compression by the liner. The propagation of nonlinear-magnetosonic waves is described analytically by the KdV-Burger's Equation, providing stable-stationary solutions. We include a finite resistivity in the energy equation and generalized Ohm's law. A radiation-hydrodynamic code is used to evaluate the dynamic shock behavior, energy coupling, and the stability of the pinch. During implosion the axial-magnetic field provides enhanced stability and thermal insulation between the liner and the target plasmas. At peak compression the large amplitude $B_z$ traps the fusion products leading to ignition in a deuterium-tritium target mixture. [Preview Abstract] |
Monday, October 31, 2016 11:42AM - 11:54AM |
BO8.00012: Staged Z-pinch Experiments on the University of Nevada, Reno, NTF Zebra Facility Frank J. Wessel, E. Ruskov, H. U. Rahman, P. Ney, T. W. Darling, Z. Johnson, E. McGee, A. Covington, E. Dutra, J. C. Valenzuela, F. Conti, J. Narkis, F. Beg A Staged Z-pinch$\footnote{``Staged Z Pinch", Phys.Rev.Lett.$\bf74$, 714 (1995)}$ load is tested on the University of Nevada, Reno, Zebra Facility, located at the Nevada Terawatt Facility. The annular liner was argon (1-cm radius $\times$ 0.5-cm thickness), the target was a deuterium fill (either gas, or plasma), and the axial-magnetic field was either, $B_z$ = 0, 100 G. This paper presents experimental data and analyses, including neutron-total yield and time-of-flight measurements. The results are benchmarked against the predictions from a 2D-MHD simulations. Results from this first (Spring 2016) series of experiments indicate that the initial-operating points selected for the mass injectors were sub-optimal. Design revisions are underway and changes in the injector timing will be implemented the Fall 2016 campaign. Companion papers in this session, and in poster papers, provide the basis for the SZP, designs and performance for the injectors, and details on the Zebra Facility. [Preview Abstract] |
Monday, October 31, 2016 11:54AM - 12:06PM |
BO8.00013: Performance of a Liner-on-Target Injector for Staged Z-Pinch Experiments F. Conti, J. C. Valenzuela, J. Narkis, I. Krasheninnikov, F. Beg, F. J. Wessel, E. Ruskov, H. U. Rahman, E. McGee We present the design and characterization of a compact liner-on-target injector, used in the Staged Z-pinch experiments conducted on the UNR-NTF Zebra Facility. Previous experiments$\footnote{F. J. Wessel, et. al. AIP Conf. Proc. 1721, 060002 (2016)}$ and analysis$\footnote{P. Ney, et.al., Phys. Plasmas {\bf 8}, 616(2001)}$ indicate that high-Z gas liners produce a uniform and efficient implosion on a low-Z target plasma. The liner gas shell is produced by an annular solenoid valve and a converging-diverging nozzle designed to achieve a collimated, supersonic, Mach-5 flow. The on-axis target is produced by a coaxial plasma gun, where a high voltage pulse is applied to ionize neutral gas and accelerate the plasma by the $\vec{J}\times\vec{B}$ force. Measurements of the liner and target dynamics, resolved by interferometry in space and time, fast imaging, and collection of the emitted light, are presented. The results are compared to the predictions from Computational Fluid Dynamics and MHD simulations that model the injector. Optimization of the design parameters, for upcoming Staged Z-pinch experiments, will be discussed. [Preview Abstract] |
Monday, October 31, 2016 12:06PM - 12:18PM |
BO8.00014: MEMS based ion beams for fusion A. Persaud, P.A. Seidl, Q. Ji, W.L. Waldron, T. Schenkel, S. Ardanuc, K.B. Vinayakumar, Z.A. Schaffer, A. Lal Micro-Electro-Mechanical Systems (MEMS) fabrication provides an exciting opportunity to shrink existing accelerator concepts to smaller sizes and to reduce cost by orders of magnitude. We revisit the concept of a Multiple Electrostatic Quadrupole Array Linear Accelerator (MEQALAC) and show how, with current technologies, the concept can be downsized from gap distances of several cm to distances in the sub-mm regime. The basic concept implements acceleration gaps using radio frequency (RF) fields and electrostatic quadrupoles (ESQ) on silicon wafers. First results from proof-of-concept experiments using printed circuit boards to realize the MEQALAC structures are presented. We show results from accelerating structures that were used in an array of nine (3x3) parallel beamlets with He ions at 15 keV. We will also present results from an ESQ focusing lattice using the same beamlet layout showing beam transport and matching. We also will discuss our progress in fabricating MEMS devices in silicon wafers for both the RF and ESQ structures and integration of necessary RF-circuits on-chip. The concept can be scaled up to thousands of beamlets providing high power beams at low cost and can be used to form and compress a plasma for the development of magnetized target fusion approaches. [Preview Abstract] |
Monday, October 31, 2016 12:18PM - 12:30PM |
BO8.00015: Non-electric applications for magneto-inertial fusion John Slough In addition to the generation of commercial electric power, there are several other applications for an intense pulse of neutrons that would be produced by magneto-inertial fusion (MIF) systems. Many of these applications can be achieved without the need for a fully developed reactor at high gain, and could thus be pursued at a much earlier stage of development which would dramatically reduce the risk of the long-term development and concern for the expense of an all-encompassing, single use system such as the tokamak or stellerator. A short list of applications well suited for MIF would include: (1) production of radioisotopes for medical applications and research, (2) efficient, high power propulsion through direct fusion heating of lithium propellants (3) Noninvasive interrogation of objects for homeland security (4) neutron radiography and tomography (5) destruction of long-lived radioactive waste, and (6) breeding of proliferation proof fissile fuel for existing nuclear reactors. These applications could all be pursued at lower neutron yield, but clearly the energy goals are by far the most significant and far reaching such as applying fusion energy as a hybrid to enable thorium cycle reactors which produce very little waste compared to the current uranium reactors. A discussion of how MIF could be configured and utilized to realize several of these uses will be discussed. [Preview Abstract] |
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