Bulletin of the American Physical Society
60th Annual Meeting of the APS Division of Plasma Physics
Volume 63, Number 11
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session CM9: Mini-Conference on Magneto-inertial Fusion Science and Technology II |
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Chair: Jonathan Davies, University of Rochester Room: OCC C123 |
Monday, November 5, 2018 2:00PM - 2:20PM |
CM9.00001: Progress in Magnetized Liner Inertial Fusion Research Kyle Peterson, David J. Ampleford, Thomas J Awe, Daniel Barnak, Edward Michael Campbell, Jonathan Davies, Matthias Geissel, Matt Gomez, Stephanie Hansen, Eric Harding, Adam Harvey-Thompson, Christopher Jennings, Brent M Jones, Patrick F Knapp, Derek C Lamppa, Grant Logan, Taisuke Nagayama, John L Porter, Gregory A. Rochau, Paul F Schmit, Daniel B Sinars, Stephen A Slutz, Ian C. Smith, Mingsheng Wei, Matthew Weis This talk will give an overview of progress in Magnetized liner inertial fusion (MagLIF) research and discuss near term plans to test scaling and understanding. Significant progress has been made in a number of areas. The efficiency of preheating the fuel with the ZBL laser has improved from depositing 200-500J in the first MagLIF experiments to >1.2kJ. Advances in diagnostics have improved our understanding of plasma conditions as well as sources of mix contaminants. We have also demonstrated significant improvements to liner stability. These improvements have led to a ~5X increase in neutron yield (1.1e13 DD) and are now within ~50% of pre-shot simulation predictions. We are now working to develop a more capable MagLIF platform with increased pre-magnetization, drive current, and fuel pre-heating. These new capabilities are predicted to improve overall target performance by more than an order of magnitude in yield and will be used to test scaling predictions. |
Monday, November 5, 2018 2:20PM - 2:40PM |
CM9.00002: Assessment of Mix in MagLIF Experiments using an Analytic Hotspot Model Patrick F Knapp, Michael E Glinsky, Matt Gomez, Matthew Evans, Stephanie Hansen, Eric Harding, Christopher Jennings, Matthew Weis, Stephen A Slutz, Kelly D Hahn, Matthew R Martin, Matthias Geissel, Ian C. Smith, Pierre-Alexandre Gourdain, Kyle J Peterson, Brent M Jones, Jens Schwarz, Gregory A. Rochau, Daniel B Sinars Mix-induced radiative losses are a significant potential source of degradation in MagLIF experiments. Mix can be introduced at the time of laser heating and late in time through traditional deceleration instability growth. Here we report on analysis of experimental data where an analytic hotspot model is used to determine the stagnation pressure and mix fraction in a suite of experiments. This information is used along with knowledge of the experimental parameters to infer the contribution to the total mix fraction from the various potential sources. We show that approximately half of the mix is incurred early in time, during laser heating, and the remainder at or near stagnation. Using our model we show that the early time mix has a larger impact on performance than the late time mix. |
Monday, November 5, 2018 2:40PM - 3:00PM |
CM9.00003: Scaled Neutron Yield Enhancement Experiments Using the Laser Driven MagLIF Platform on the OMEGA Laser Jonathan Peebles, Jonathan Davies, Daniel Barnak, Edward Hansen, Adam Sefkow, Vladimir Glebov, Riccardo Betti, Edward Michael Campbell The team at the LLE has developed an experimental platform using the OMEGA laser to explore a scaled version of the Z machine MagLIF point design. OMEGA, which delivers 1/1000th the energy of Z compresses a 1/10 scaled cylinder. A specialized 3ω preheat beam fires down the axis of the cylinder, raising the fuel temperature to 200 eV. Magnetic fields of up to 30 T were generated in the region of interest using coils driven by current from the Magneto-Inertial Fusion Electrical Discharge System (MIFEDS). Recent experimental campaigns have demonstrated the enhancement of neutron yield by the application of an initial magnetic field along the cylindrical implosion axis for multiple fuel densities. We present data from all 4 experimental cases that combine the application of the magnetic field and preheat beam to a cylindrical implosion. |
Monday, November 5, 2018 3:00PM - 3:20PM |
CM9.00004: Extended Magneto-hydrodynamic effects in MagLIF. Jeremy Chittenden, Aidan Boxall, Christopher Alexander Walsh We present results from simulations of MagLIF experiments at Sandia National Laboratory, using a recently developed extended MHD version of the 3D Gorgon code which includes the full Braginskii form of Ohm’s law and associated magnetised heat flow. The effects of anisotropic magnetised heat flow on the early growth of perturbations through MHD and electro-thermal instabilities is examined. The contribution of the Hall term to expansion of surface plasma is also studied. Different perturbation sources including surface roughness, volumetrically distributed defects or inclusions, and desorbed gases are investigated. Anisotropic heat flow due to the helical field is also important within the fuel region during implosion and stagnation as is the effect of Righi-LeDuc heat flow in the presence of r-theta plane asymmetry. The role of the Nernst and Ettingshausen terms in exacerbating heat flow in the fuel-liner interface region and determining the optimal level of laser pre-heat is also examined. |
Monday, November 5, 2018 3:20PM - 3:40PM |
CM9.00005: Subsonic transport of magnetic flux via a Nernst wave A. L. Velikovich, J. L. Giuliani The Nernst effect plays a dominant role in the subsonic transport of magnetic flux in hot, dense fusion plasmas, where the temperature diffusivity is much greater than the magnetic diffusivity, as in MagLIF near stagnation. The existing theoretical scalings for the Nernst-dominated magnetic flux losses from hot magnetized fusion plasmas are based on the analysis of self-similar solutions of the full set of plasma transport equations in a planar geometry, for a half-space occupied by the hot magnetized plasma and confined by a fixed cold boundary that may or may not be ablating. The wall roughly emulates the liner or the DT layer in the “ice-burner” MagLIF regime. We have investigated the solutions that do not involve any artificial walls but describe both cold/dense and hot/rarefied regions of the plasma. As the heated cold plasma expands, the heat diffusion proceeds through the material interface that separates cold and hot layers. But the Nernst-transported magnetic flux leaves the material interface behind, propagating into the expanding cold plasma as a narrow front that we call the Nernst wave. We report analytic and numerical solutions involving Nernst waves and describe their effect on magnetic flux and heat losses from the hot plasma. |
Monday, November 5, 2018 3:40PM - 4:00PM |
CM9.00006: The magnetothermodynamics of compressed turbulent MHD plasmas for MIF Michael R Brown, Manjit Kaur, Adam D Light, Katie Gelber, Nicholas Anderson, Hariharan Srinivasulu, Katherine Lima, David A Schaffner We will provide an overview of magneto-inertial fusion-related studies of what we call magnetothermodynamics on compressed Taylor states at SSX. Our goal for the ALPHA project has been to accelerate a Taylor state to high velocity, then stagnate and compress the object into a suitable MIF target. We have characterized the magnetic structure, velocity, density ($0.5 \times 10^{16}~cm^{-3}$), proton temperature ($20~eV$), and magnetic field ($0.4~T$) of relaxed helical Taylor states. Since we measure proton pressure ($P = nkT$) and volume as a function of time, we can construct $PV$ diagrams, and measure equations of state. Recently, we have been focussing increasing the Taylor state lifetime, primarily by increasing electron temperature. We estimate $T_e$ with a VUV spectrometer measurement of the ratio of the $C_{III}$ to $C_{IV}$ line intensities. We have also begun studies of the temporal evolution of our Taylor state in the SSX MHD wind tunnel from an axisymmetric compact spheromak to an elongated Taylor state using the Dedalus framework. The EOS for our compression experiments is sensitive to proton dynamics along and across field lines, so we are also simulating particle orbits in the Taylor state geometry. |
Monday, November 5, 2018 4:00PM - 4:20PM |
CM9.00007: Experimental simulation of Magnetized Target Fusion compression physics by a magnetized plasma jet impacting a gas target cloud Paul Bellan, Byonghoon Seo, Hui Li Physics underlying magnetized target fusion is investigated using a method where reference frames are changed so that the imploding liner compressing a magnetized plasma is simulated by a fast MHD-driven plasma jet (representing the magnetized plasma) impacting a gas target cloud (representing the liner). This method is non-destructive so very large numbers of shots are possible. Diagnostics include an axially translatable interferometer (density), Thomson scattering (density, temperature), a magnetic probe array, spectrometers, and a radiated power detector. Detailed measurements indicate the impact causes jet plasma compression and heating as well as compression of the magnetic field frozen into the jet. The temperature initially increases in a manner consistent with adiabatic scaling but then suddenly drops. Analysis indicates this drop happens because of radiation via powerful atomic line emission from neutral hydrogen atoms created by three-body recombination driven by the compression. Numerical simulations show temperature increases similar to the experimental observations before the line emission occurs. These results show that to attain high temperature compression must occur much faster than all radiative loss rates. |
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