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 JO6: Magnetized Inertial Confinement Fusion I |
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Chair: Kyle Peterson, Sandia National Laboratories Room: 201/202 |
Tuesday, November 17, 2015 2:00PM - 2:12PM |
JO6.00001: Impact of target modifications on Magnetized Liner Inertial Fusion performance Matthew Gomez, Patrick Knapp, Adam Sefkow, Stephen Slutz, Thomas Awe, Stephanie Hansen, Kelly Hahn, Eric Harding, Christopher Jennings, Ryan McBride, Daniel Sinars, Gregory Rochau, Kyle Peterson Magnetized Liner Inertial Fusion (MagLIF) is a magnetically-driven fusion concept in which an axial magnetic field and laser heating are used to relax the implosion requirements of inertial confinement fusion [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)]. Initial experiments demonstrated the promise of the concept with relatively high yields (primary DD $=$ 2e12), ion temperatures (2.5 keV), and magnetic field-radius products (\textgreater 0.3 MG-cm). In order to better understand the portions of parameter space in which MagLIF can operate effectively, a series of experiments are being conducted to test the impact of various changes (e.g., laser-entrance-hole window thickness, imploding height of the target, endcap material, laser energy, laser spot size, initial fuel density). The impact of these changes on target performance (primary neutron yield, ion temperature, stagnation volume, etc.) will be discussed. *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 No. DE-AC04-94AL85000. [Preview Abstract] |
Tuesday, November 17, 2015 2:12PM - 2:24PM |
JO6.00002: Laser Pre-Heat Studies for MagLIF with Z-Beamlet Matthias Geissel, Adam J. Harvey-Thompson, T.J. Awe, M.R. Gomez, E. Harding, C. Jennings, M.W. Kimmel, P. Knapp, K. Peterson, M. Schollmeier, A.B. Sefkow, J.E. Shores, D.B. Sinars, S.A. Slutz, I.C. Smith, C.S. Speas, R.A. Vesey, J.L. Porter, E.M. Campbell, S.M. Lewis Magnetized Liner Inertial Confinement Fusion (MagLIF) relies on strong pre-heat of the fuel, typically hundreds of eV. Z-Beamlet delivers up to 4\,kJ of laser energy to the target to achieve this goal. Over the last year, several experimental campaigns at the Pecos target area of Sandia's Z-Backlighter Facility and in the center section of the Z-Accelerator have been performed to investigate pre-heat. Primary objectives of these campaigns were the transmission through the laser entrance hole (LEH) in dependence of window thicknesses and focus parameters (including phase plate smoothing), as well as energy coupling to the gaseous fuel. The applied diagnostic suite included a wide range of time integrated and time-resolved X-ray imaging devices, spectrometers, backscatter monitors, a full-beam laser transmission calorimeter, and X-ray diodes.We present the findings of these studies, looking ahead towards a standard pre-heat platform. [Preview Abstract] |
Tuesday, November 17, 2015 2:24PM - 2:36PM |
JO6.00003: Three Dimensional modeling of instability development in MagLIF loads on the Z Generator C.A. Jennings, E.C. Harding, M.R. Gomez, S.B. Hansen, T.J. Awe, R.D. McBride, M.R. Martin, K.J. Peterson, J.P. Chittenden Liners imploded by a fast rising (\textless 100ns) current to compress a magnetized, preheated fuel offer the potential to efficiently reach fusion conditions [S.A. Slutz \textit{et al}. Phys. Plasmas \textbf{17}, 056303 (2010)]. Experiments with these Magnetized Liner Inertial Fusion (MagLIF) loads have demonstrated success [M.R. Gomez et al Phys. Rev. Lett. \textbf{113}, 155003(2014)]. Performance may be limited by poor laser coupling in preheating the fuel to be imploded [A.B. Sefkow et al. Phys. Plasmas \textbf{21}, 072711(2014)]. However time integrated imaging also shows structure in the final fuel assembly indicating potential disruption from instabilities which may also limit neutron yield. We simulate the implosion and stagnation of MagLIF targets using the 3D MHD code GORGON. Generating synthetic diagnostics for comparison with data we discuss how implosion instabilities comparable to those diagnosed with radiography affect fuel compression and confinement. By further comparison of calculation results with PCD traces, time integrated spectra and crystal imaging we discuss how fuel conditions vary in response to feedthrough of implosion instabilities, and how structures formed may affect diagnostic interpretation. [Preview Abstract] |
Tuesday, November 17, 2015 2:36PM - 2:48PM |
JO6.00004: The effect of electro-thermal and electro-choric instabilities and material strength on MagLIF liner stability James Pecover, Jeremy Chittenden Magnetized liner inertial fusion (MagLIF) is a promising route to controlled thermonuclear fusion. The concept involves magnetically imploding a metal liner containing fuel with an azimuthal magnetic field (B$_{\mathrm{z}})$; a key limitation of such systems is the magneto-Rayleigh-Taylor (MRT) instability. MagLIF relevant liner implosions with B$_{\mathrm{z}}=$0 carried out at SNL showed high amplitude MRT growth; we present a quantitative comparison between experimental results and 3D results from our MHD code Gorgon, demonstrating closer agreement for the MRT properties with the inclusion of electro-thermal and electro-choric instabilities (ETI and ECI) and material strength. The ETI and ECI result in early time azimuthally correlated structures which provide a seed for the MRT. Material strength increases the ETI amplitude due to positive feedback during the solid phase of the liner. Similar liner implosions with B$_{\mathrm{z}}$ exhibited a re-orientation of the MRT into helical structures, which are yet to be reproduced by simulations without an artificial helical initialisation. Our 3D Gorgon results with B$_{\mathrm{z}}$ show helices prior to vapourisation; these occur at initially positive angles before changing sign, tending to zero later in time. This angle does not follow the relative magnitudes of B$_{\mathrm{z}}$ and B$_{\mathrm{\theta }}$ as would be expected for the MRT. The angle instead follows the ratio of axial and azimuthal currents (induced by compression or rarefaction of the initial B$_{\mathrm{z}})$, indicating an electro-thermal origin. [Preview Abstract] |
Tuesday, November 17, 2015 2:48PM - 3:00PM |
JO6.00005: Impact of Inner Surface Perturbations on the Stability of Cylindrical Liner Implosion Matthew Weis, Kyle Peterson, Mark Hess, Y.Y. Lau, Peng Zhang, Ronald Gilgenbach This paper studies the effects of initial perturbations on the inner liner surface (ILS) of an imploding cylindrical liner. In MagLIF [1], nonuniform preheat of the fuel could provide an additional source of spatial nonuniformity on the ILS. A blast wave generated by the laser preheat might trigger the Richtmyer-Meshkov instability (RM) on the ILS which then serves as another seed to the Rayleigh-Taylor instability (RT) during the stagnation (deceleration) phase of the implosion. Another scenario is that the shock initiated from the outer liner surface, during current rise [2], propagates inward and is reflected at the ILS. This reflected shock would carry the initial ILS perturbations [2] which then serve as an additional seed for the magneto-RT (MRT) during the acceleration phase of the implosion. These potentially dangerous interactions are analyzed using the 2D HYDRA code. The effects of axial magnetic fields, of the initial surface roughness spectrum, and of gas fill or water fill (to examine deceleration phase RT) are studied. \\[4pt] [1] M. R. Gomez, et al., PRL 113,155003 (2014); Phys. Plasmas 22, 056306 (2015).\\[0pt] [2] M. R. Weis, et al., Phys. Plasmas 21, 122708 (2014); 22, 032706 (2015). [Preview Abstract] |
Tuesday, November 17, 2015 3:00PM - 3:12PM |
JO6.00006: Effects of Magnetic Field Topology on Secondary Neutron Spectra in MagLIF Brian Appelbe, Jeremy Chittenden Ignition in Magneto-Inertial Fusion schemes requires both inertial and magnetic confinement of the fuel and charged fusion products. Recent theoretical and experimental work has demonstrated the confinement of charged fusion products by magnetic fields in Magnetized Liner Inertial Fusion (MagLIF) experiments. This confinement can be inferred from the ratio of secondary to primary neutron yields and the shape of secondary neutron spectra. In this work we investigate the effects of magnetic field topology on the shape of secondary neutron spectra. The MagLIF design has a cylindrical geometry and includes both axial and azimuthal magnetic fields. The azimuthal field is initially in the liner surrounding the fuel but instability growth may cause it to penetrate into the fuel. Charged fusion products (such as tritons or alpha particles) that are isotropically emitted and then confined by an axial field will flow parallel and anti-parallel to the field with equal intensities. In the case of tritons, this motion results in a secondary neutron spectrum emitted in the axial direction that is symmetric. However, in an azimuthal field such particles exhibit singular orbits and there is a net ion drift along the axis. This ion drift can cause the secondary neutron spectrum to be asymmetric. We examine the effects on the spectrum shape of confinement by a combination of axial and azimuthal fields. [Preview Abstract] |
Tuesday, November 17, 2015 3:12PM - 3:24PM |
JO6.00007: MagLIF scaling on Z and future machines Stephen Slutz, William Stygar, Matthew Gomez, Edward Campbell, Kyle Peterson, Adam Sefkow, Daniel Sinars, Roger Vesey The MagLIF (Magnetized Liner Inertial Fusion) concept [S.A. Slutz et al Phys. Plasmas 17, 056303, 2010] has demonstrated [M.R. Gomez et al., PRL 113, 155003, 2014] fusion--relevant plasma conditions on the Z machine. We present 2D numerical simulations of the scaling of MagLIF on Z indicating that deuterium/tritium (DT) fusion yields greater than 100 kJ could be possible on Z when operated at a peak current of 25 MA. Much higher yields are predicted for MagLIF driven with larger peak currents. Two high performance pulsed-power machines (Z300 and Z800) have been designed based on Linear Transformer Driver (LTD) technology. The Z300 design would provide approximately 48 MA to a MagLIF load, while Z800 would provide about 66 MA. We used a parameterized Thevenin equivalent circuit to drive a series of 1D and 2D numerical simulations with currents between and beyond these two designs. Our simulations indicate that 5-10 MJ yields may be possible with Z300, while yields of about 1 GJ may be possible with Z800. [Preview Abstract] |
Tuesday, November 17, 2015 3:24PM - 3:36PM |
JO6.00008: Transport Phenomena in Magnetized Plasmas across Coupling Regimes Scott Baalrud, Jerome Daligault Plasmas with components that are magnetized, strongly coupled, or both arise in a variety of frontier plasma physics experiments including magnetized dusty plasmas, magnetized ICF concepts, as well as from self-generated fields in ICF. Here, a theory is described that treats classical mixtures of magnetized and unmagnetized species across coupling regimes. The approach is based on an extension of the recent effective potential transport theory [1] to include a magnetic field. The utility of this approach is that it can be incorporated into magnetohydrodynamic descriptions by modification of the Coulomb logarithm in the transport coefficients. Like weakly coupled plasma theory, the magnetic field is found to suppress cross-field transport. However, the ratio of parallel to cross field transport rates is much closer to unity at strong coupling. Not only cross field, but also parallel, transport rates are found to be reduced by the field. Results are compared with classical molecular dynamics simulations of self-diffusion of the one component plasma [2], and with simulations of parallel to perpendicular temperature equilibration of an initially anisotropic distribution.\\[4pt] [1] S.D. Baalrud, and J. Daligault, PRL 110, 235001 (2013).\\[0pt] [2] T. Ott and M. Bonitz, PRL 107, 135003 (2011). [Preview Abstract] |
Tuesday, November 17, 2015 3:36PM - 3:48PM |
JO6.00009: First Results from Laser-Driven MagLIF Experiments on OMEGA: Time Evolution of Laser Gas Heating Using Soft X-Ray Diagnostics D.H. Barnak, R. Betti, P.-Y. Chang, J.R. Davies Magnetized liner inertial fusion (MagLIF) is a promising inertial confinement fusion scheme comprised of three stages: axial magnetization, laser heating of the deuterium$-$tritium gas fill, and compression of the gas by the liner. To study the physics of MagLIF, a scaled-down version has been designed and implemented on the OMEGA-60 laser. This talk will focus primarily on the heating process of a MagLIF target using a 351-nm laser. A neon-doped deuterium gas capsule was heated using a 2.5-ns square pulse delivering 200 J of laser energy. Spectral analysis of the x-ray emission from the side and the laser entrance hole of the capsule is used to infer the time evolution of the gas temperature. The x-ray spectra for a grid of possible gas temperatures and densities are simulated using \textit{Spect3D} atomic modeling software. The simulation results are then used to deconvolve the raw signals and obtain density and temperature estimations. A gas temperature lower bound of 100 eV at 1.3 ns after the start of the laser pulse can be inferred from these estimations. The estimations are then compared to 2-D hydrocode modeling. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by DE-FG02-04ER54786 and DE-FC02-04ER54789 (Fusion Science Center). [Preview Abstract] |
Tuesday, November 17, 2015 3:48PM - 4:00PM |
JO6.00010: First Results from Laser-Driven MagLIF Experiments on OMEGA: Backscatter and Transmission Measurements of Laser Preheating J.R. Davies, D.H. Barnak, R. Betti, P.-Y. Chang A laser-driven version of MagLIF (magnetized liner inertial fusion) is being developed on the OMEGA laser. In the first experiment, laser preheating with a single OMEGA beam was studied. Laser energies of 60 to 200 J in 2.5-ns-long pulses were used, with a distributed phase plate giving a Gaussian intensity profile with a 96 $\mu $m full width at half maximum. We report on backscatter measurements from gas-filled cylinders and both backscatter and transmission measurements from the 1.84-$\mu $m-thick polyimide foils used for the laser entrance windows. Backscatter spectra and energies from both cylinders and foils alone were very similar. Approximately 0.5{\%} of the total incident laser energy was backscattered. Backscattering lasted for little more than 0.5 ns. The fraction of laser energy transmitted through foils within the original beam path increased from 50{\%} to 64{\%} as the laser energy was increased from 60 to 200~J. Up to 10{\%} of the laser energy was sidescattered as the foil started to transmit. Sidescattering of transmitted light lasted $\sim$0.5 ns. The sidescattering might be avoided by using a short prepulse at least 0.5 ns prior to the main pulse. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by DE-FG02-04ER54786 and DE-FC02-04ER54789 (Fusion Science Center). [Preview Abstract] |
Tuesday, November 17, 2015 4:00PM - 4:12PM |
JO6.00011: First Results from Laser-Driven MagLIF Experiments on OMEGA: Optimization of Illumination Uniformity P.-Y. Chang, D.H. Barnak, R. Betti, J.R. Davies, G. Fiksel The physics principles of magnetic liner inertial fusion (MagLIF) are investigated on the Omega Laser Facility using 40 beams for compression and 1 beam for preheating a small (300-$\mu $m-radius, 1-mm-long) cylindrical plastic shell. Here we report of the first implosion experiments to optimize the illumination uniformity. These initial experiments do not include laser preheat. The beams in ring 3 and ring 4 around the symmetric axis are used to implode a cylindrical target. Beams in different rings illuminate the target surface with different incident angles, leading to different energy-coupling efficiencies. The beams in ring 3 have a shallower angle of incident than ring 4. When implosion velocities are compared for targets driven by either ring 3 or ring 4, we find that ring 3 couples $\sim 40\% $ less kinetic energy than ring 4. One- and two-dimensional simulations using \textit{LILAC} (1-D) and \textit{FLASH} (2-D) are used to compare to the experimental results and to optimize the illumination uniformity. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by DE-FG02-04ER54786 and DE-FC02-04ER54789 (Fusion Science Center). [Preview Abstract] |
Tuesday, November 17, 2015 4:12PM - 4:24PM |
JO6.00012: Magnetized Inertial Confinement Fusion on the National Ignition Facility L. John Perkins, G. Logan, M. Rhodes, G. Zimmermann, D. Ho, D. Strozzi, D. Blackfield, S. Hawkins We are assessing the potential of imposed magnetic fields on ignition targets for the National Ignition Facility. Both magnetized room-temperature DT gas targets and CH/diamond cryo-ignition capsules are under study. Initial applied fields of 30-70T that compress to greater than 10,000T (100MG) under capsule implosion may relax conditions required for ignition and burn due to suppression of electron heat conduction, reduction of alpha deposition range and stabilization of hydro instabilities. This may permit recovery of ignition, or at least significant alpha particle heating, in otherwise submarginal capsules. We will report on the design and performance simulations of magnetized ignition targets and hohlraum physics, and summarize present experiments testing the attainable magnetic field limits in hohlraum-coil systems driven by a pulsed power supply. [Preview Abstract] |
Tuesday, November 17, 2015 4:24PM - 4:36PM |
JO6.00013: Magnetized High-Density Carbon (HDC) ignition capsules: yield enhancement and ignition conditions G. Zimmerman, D. Ho, L.J. Perkins, B. Logan, M. Rhodes, J. Salmonson Imposing a magnetic (B) field on capsules can turn capsules that either fail or have low yield, because of low 1-D margin or mix, into igniting capsules that give yield in the MegaJoule range. The imposed B field, e.g. 50 T can be amplified by up to O(10$^{3})$, in the hotspot, as it is being compressed by the imploding shell. At this high field strength, the gyro radius of $\alpha $-particles becomes smaller than the hotspot size. Consequently, the heating of the hotspot becomes more efficient. (We have experimentally demonstrated that field strength \textgreater 30 T can be generated inside a hohlraum.) We give three examples of implosions with HDC ablators that are sub or marginally ignited because of high fuel entropy, low implosion velocity, or high mix. By imposing seed field between 40 -- 50 T, all these capsules can generate yield in the MegaJoule range. The MHD stability in these configurations will be discussed. The generalization of Lindl-Widner ignition condition with the inclusion of B field and the dependence of fraction of $\alpha $ energy deposition on $\rho $R will be presented. With the magnitude of B field mentioned here, the ignition condition, or the minimum hotspot $\rho $R required, can be reduced to about 0.2 from 0.3 g/cm$^{2}$ for the case without B field. [Preview Abstract] |
Tuesday, November 17, 2015 4:36PM - 4:48PM |
JO6.00014: The Progress of Research Project for Magnetized Target Fusion in China Xian-Jun Yang The fusion of magnetized plasma called Magnetized Target Fusion (MTF) is a hot research area recently. It may significantly reduce the cost and size. Great progress has been achieved in past decades around the world. Five years ago, China initiated the MTF project and has gotten some progress as follows: 1. Verifying the feasibility of ignition of MTF by means of first principle and MHD simulation; 2. Generating the magnetic field over 1400 Tesla, which can be suppress the heat conduction from charged particles, deposit the energy of alpha particle to promote the ignition process, and produce the stable magnetized plasma for the target of ignition; 3. The imploding facility of FP-1 can put several Mega Joule energy to the solid liner of about ten gram in the range of microsecond risen time, while the simulating tool has been developed for design and analysis of the process; 4. The target of FRC can be generated by ``YG 1 facility'' while some simulating tools have be developed. Next five years, the above theoretical work and the experiments of MTF may be integrated to step up as the National project, which may make my term play an important lead role and be supposed to achieve farther progress in China. [Preview Abstract] |
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