Bulletin of the American Physical Society
55th Annual Meeting of the APS Division of Plasma Physics
Volume 58, Number 16
Monday–Friday, November 11–15, 2013; Denver, Colorado
Session BO7: Shock, Magneto, Other ICF |
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Chair: Andrew Schmitt, Naval Research Laboratory Room: Governor's Square 12 |
Monday, November 11, 2013 9:30AM - 9:42AM |
BO7.00001: Electron Shock Ignition R. Betti, R. Nora, K.S. Anderson, M. Lafon, W. Theobald, R. Yan, C. Ren Shock ignition uses a late strong shock to ignite the hot spot of an inertial confinement fusion (ICF) capsule. In the standard shock-ignition scheme, the shell is driven at a relatively slow velocity of about 250 km/s and an ignitor shock with an initial pressure $\ge $300 Mbar is launched by the ablation pressure from a spike in laser intensity. Recent experiments on OMEGA have shown that focused beams with intensity up to $8\times 10^{15}\;\mbox{W/cm}^{2}$ can produce copious amounts of hot electrons. The hot electrons are produced by laser--plasma instabilities (LPI's) (such as stimulated Raman scattering and two-plasmon decay) and can carry up to $\sim $15{\%} of the laser energy. NIF-scale targets will likely produce even more hot electrons because of the large plasma scale length. We show that it is possible to design ignition targets with implosion velocities as low as 100 km/s that are shock ignited using LPI-generated hot electrons to raise the pressure of the shell up to 2 to 3 Gbar just before stagnation. These targets feature a mid-$Z$ layer designed to stop the hot electrons up to temperatures of 200 keV. The gigabar pressures in the heated mid-$Z$ layer drive a multigigabar shock in the hot spot, igniting it with a significant margin. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center). [Preview Abstract] |
Monday, November 11, 2013 9:42AM - 9:54AM |
BO7.00002: Low-Velocity Shock Ignition on the NIF K.S. Anderson, P.W. McKenty, T.J.B. Collins, J.A. Marozas, R. Betti Shock ignition (SI)\footnote{R. Betti\textit{ et al.}, Phys. Rev. Lett. \textbf{98}, 155001 (2007).} has been proposed as a low-energy alternative path to ignition on the National Ignition Facility (NIF). Previously, a polar-drive SI capsule and pulse design was presented\footnote{K. S. Anderson\textit{ et al.}, Phys. Plasmas \textbf{20}, 056312 (2013).} for the NIF at a velocity of $3.05 \times 10^{7}$ cm/s---substantially higher than the velocities of typical SI designs ($\sim$2.4 to 2.7 $\times$ 10$^7$ cm/s). The motivation for the higher velocity was to improve margin in 1-D simulations. This target was shown to be sufficiently stable in 2-D simulations to the various sources of nonuniformity anticipated on the NIF, being most sensitive to imprinted perturbations from laser speckle. This paper reports on lower-velocity SI designs aimed at reducing the in-flight aspect ratio, thereby decreasing sensitivity to laser imprint. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Monday, November 11, 2013 9:54AM - 10:06AM |
BO7.00003: Laser-plasma interactions and hot electron generation in shock ignition Rui Yan, Chuang Ren, Jun Li We present particle-in-cell (PIC) simulations for laser-plasma interactions in the recent 40$+$20-beam spherical shock ignition experiments on the Omega laser facility. Two-dimensional PIC simulations including electron-ion collisions and lasting more than 10 ps show a bursting pattern in both plasma waves and hot electron fluxes, which are attributed to the interplay between stimulated Raman scattering (SRS) and two-plasmon decay (TPD) instabilities. SRS is the main source for hot electrons but TPD can produce \textgreater 100 keV ones. The observed hot electron temperatures compare favorably to those measured in the experiments. [Preview Abstract] |
Monday, November 11, 2013 10:06AM - 10:18AM |
BO7.00004: Demonstration of 200-Mbar Ablation Pressure for Shock Ignition W. Theobald, R. Nora, M. Lafon, K.S. Anderson, J.R. Davies, M. Hohenberger, T.C. Sangster, W. Seka, A.A. Solodov, C. Stoeckl, B. Yaakobi, R. Betti, A. Casner, C. Reverdin, X. Ribeyre, A. Vallet The shock-ignition concept in inertial confinement fusion uses a high-power spike at the end of an assembly laser pulse, launching a strong shock wave with an ablation pressure of $\sim $0.3 Gbar that increases in strength as it converges in the imploding shell. A key milestone for shock ignition to be a credible path to ignition is to demonstrate the generation of a seed shock pressure 0.3 Gbar at laser intensities greater than $5\times 10^{15}$ W/cm$^{2}$. We demonstrate shock pressures close to 0.2 Gbar at $\sim 4\times 10^{15}$ W/cm$^{2}$ in OMEGA experiments with $\sim $500-$\mu $m-diam solid plastic ball targets doped with a small percentage of titanium. The strong shock wave converges in the center of the solid target and heats a small volume of $\sim 10^{3} \mu$m$^{3}$ to temperatures of several hundred eV, creating a short x-ray flash of titanium line emission. The emerging x-ray flash was measured with spatial and temporal resolution, allowing for the laser drive conditions to be inferred by comparison with hydrodynamic simulations. Hot-electron generation was also characterized by the measurement of K$_{\alpha }$ emission and hard x-ray emission. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Monday, November 11, 2013 10:18AM - 10:30AM |
BO7.00005: Fast electron heating of dense plasma relevant to shock ignition T.E. Fox, A.P.L. Robinson, J. Pasley With an intensity in the range of $10^{16}$ W/cm$^{2}$, the ignitor pulse in shock-ignition inertial confinement fusion is well above the threshold of parametric instabilities. Simulations (e.g.\ Klimo et al.\ 2011 Phys.\ Plasmas 18 082709) indicate that a significant amount of energy will be deposited in energetic electrons with energies $<$100 keV and it has been proposed that these may play a beneficial role in enhancing the ignitor shock. Simulations by Gus'kov et al. (Phys.\ Rev.\ Lett.\ 109 255004 (2012)) show that, under shock-ignition relevant conditions, a mono-energetic electron beam can drive strong shocks in a uniform plasma. We extend this study to the more realistic case of a Maxwellian energy distribution in the fast electron population. Having a distribution of electron mean-free-paths results in a more extended heating profile compared to a mono-energetic beam. However, we show it is still possible to launch strong shocks in this more realistic scenario and achieve equivalent pressures. The peak pressures achieved compare well with analytic scalings. [Preview Abstract] |
Monday, November 11, 2013 10:30AM - 10:42AM |
BO7.00006: Preliminary results from the first integrated Magnetized Liner Inertial Fusion (MagLIF) experiments on the Z accelerator* M.R. Gomez, S.A. Slutz, A.B. Sefkow, A.J. Harvey-Thompson, T.J. Awe, M.E. Cuneo, M. Geissel, M. Herrmann, C. Jennings, D. Lamppa, M. Martin, R.D. McBride, D.C. Rovang, D. Sinars, I.C. Smith Sandia National Laboratories' Z Machine [1] provides a drive current of up to 27 MA with 100 ns risetime to a magnetically-driven load. Magnetized Liner Inertial Fusion (MagLIF) [2] is the main focus of the inertial confinement fusion program on Z. The MagLIF concept uses an imploding metallic cylindrical liner to compress magnetized, pre-heated fusion fuel. Simulations indicate that fusion yields on the order of 100 kJ (5e16 DT neutrons) are achievable with a drive current of 27 MA in 100 ns, a laser preheat of 8 kJ in 8 ns, an applied axial B-field of 30 T, and deuterium-tritium fusion fuel. The first fully integrated MagLIF experiments are scheduled to be conducted on Z late summer 2013. These tests will utilize a drive current of 16 MA, a laser preheat of 2 kJ in 2 ns, an applied B-field of 10 T, and deuterium fuel. With these reduced parameters, simulations predict yields greater than 1e10 DD neutrons. [1] M. E. Savage, et al., 18th International Pulsed Power Conference Proceedings pp. 983-990 (2011). [2] S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010). *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, November 11, 2013 10:42AM - 10:54AM |
BO7.00007: Low-Convergence Magnetized Liner Inertial Fusion Stephen Slutz, Roger Vesey, Daniel Sinars, Adam Sefkow Numerical simulations indicate that pulsed-power driven liner-implosions could produce substantial fusion yields if the deuterium-tritium (DT) fuel is first magnetized and preheated [S.A. Slutz et al Phys. Plasmas 17, 056303 (2010)]. As with all inertial fusion, the implosions could be degraded by the Rayleigh-Taylor instability. Since highly convergent implosions are more susceptible to this instability, we have explored the necessary conditions to obtain significant fusion yield with low-convergence liner-implosions. Such low-convergence implosions can be obtained if the fuel is sufficiently preheated and magnetized. We present analytic and numerical studies of laser plasma heating, which indicate that low convergence implosions should be possible with sufficient laser energy. [Preview Abstract] |
Monday, November 11, 2013 10:54AM - 11:06AM |
BO7.00008: Semi-analytic modeling and simulation of magnetized liner inertial fusion R.D. McBride, S.A. Slutz, S.B. Hansen Presented is a semi-analytic model of magnetized liner inertial fusion (MagLIF). This model accounts for several key aspects of MagLIF, including: (1) pre-heat of the fuel; (2) pulsed-power-driven liner implosion; (3) liner compressibility with an analytic equation of state, artificial viscosity, and internal magnetic pressure and heating; (4) adiabatic compression and heating of the fuel; (5) radiative losses and fuel opacity; (6) magnetic flux compression with Nernst thermoelectric losses; (7) magnetized electron and ion thermal conduction losses; (8) deuterium-deuterium and deuterium-tritium primary fusion reactions; and (9) magnetized alpha-particle heating. We will first show that this simplified model, with its transparent and accessible physics, can be used to reproduce the general 1D behavior presented throughout the original MagLIF paper [S. A. Slutz \textit{et al}., Phys. Plasmas \textbf{17}, 056303 (2010)]. We will then use this model to illustrate the MagLIF parameter space, energetics, and efficiencies, and to show the experimental challenges that we will likely be facing as we begin testing MagLIF using the infrastructure presently available at the Z facility. Finally, we will demonstrate how this scenario could likely change as various facility upgrades are made over the next three to five years and beyond. 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, November 11, 2013 11:06AM - 11:18AM |
BO7.00009: Thermonuclear Burn in Ignition-Scale ICF Targets under Highly Compressed Magnetic Fields L. John Perkins, B. Grant Logan, George Zimmerman, John Moody, Darwin Ho, David Strozzi, Mark Rhodes, George Caporaso, Christopher Werner We report for the first time on full 2-D radiation-hydrodynamic implosion simulations that demonstrate the impact of highly compressed magnetic fields on the ignition and burn of spherically-converging ICF targets with application to the National Ignition Facility indirect-drive ignition capsule [L.J.Perkins et al, \textit{Phys. Plasmas}, to be published Aug 2013]. Initial seed fields of 20-100T (potentially attainable using present experimental methods) that compress to greater than 10$^4$ T (100 MG) under implosion can relax hotspot areal densities and pressures required for ignition and propagating burn by $\sim$50{\%} in targets degraded by lower-mode perturbations compared to those with no applied field. This accrues from range shortening and magnetic mirror trapping of fusion alpha particles, suppression of electron heat conduction and potential reduction of hydrodynamic instability growth. This may permit the recovery of ignition, or at least significant alpha particle heating, in submarginal capsules that would otherwise fail because of adverse hydrodynamic instabilities. The field may also ameliorate adverse hohlraum plasma conditions such as stimulated Raman scattering. We also discuss experimental concepts for a potential NIF hohlraum coil driven by a co-located pulsed power supply that may be capable of detectable alpha particle heating and fusion yield through magnetized volumetric burn in a high pressure DT gas capsule. [Preview Abstract] |
Monday, November 11, 2013 11:18AM - 11:30AM |
BO7.00010: Yield Enhancement in Magnetized ICF Targets Using Low-Adiabat Pulse Shapes on OMEGA P.-Y. Chang, G. Fiksel, D.H. Barnak, J.R. Davies, R. Betti We present the latest experimental data of neutron yield and ion-temperature enhancements obtained by magnetizing the hot spot of inertial confinement fusion (ICF) implosions. The capsules are 23-$\mu $m plastic shells filled with 11 atm of D$_{2}$ gas. The laser pulse is shaped to drive the shell on an adiabat of $\sim $2 and the $\sim $7-T seed magnetic field is produced using a single coil. The initial seed is predicted to be compressed to $\sim $20 MG---enough to magnetize the electrons in the hot spot and reduce the heat conductivity. Six null shots (without field) and six shots with B-fields were conducted. Four of the B-field shots show a yield and temperature enhancement of about $\sim $23{\%} and $\sim $10{\%}, respectively, in agreement with the predictions of 1.5-D and 2-D magnetohydrodynamic simulations. Those results are similar to previous experiments reported in.\footnote{P. Y. Chang \textit{et al.}, Phys. Rev. Lett. \textbf{107}, 035006 (2011).} Two of the B-field shots produced an anomalously high yield enhancement of 80{\%} and 200{\%}. Additional experiments are required to verify these anomalous results. Compressed field measurements using a high-energy proton backlighter are proposed and preliminary data from one field-measurement experiment will be presented. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center). [Preview Abstract] |
Monday, November 11, 2013 11:30AM - 11:42AM |
BO7.00011: Magneto-Rayleigh-Taylor growth and feedthrough in cylindrical liners Matthew Weis, Y.Y. Lau, Ronald Gilgenbach, Kyle Peterson, Mark Hess Cylindrical liner implosions in the MagLIF concept [1] are susceptible to the magneto-Rayleigh-Taylor instability (MRT). The linearized ideal MHD equations are solved, including the presence of an axial magnetic field and the effects of sausage and kink modes. The eigenmode solution, using appropriate equilibrium profiles, allows an assessment of the local MRT growth rate and of the instantaneous feedthrough factor during the entire implosion process. Of particular interest will be the high convergence/stagnation phase, which is difficult to image experimentally. Strong axial magnetic fields can mitigate feedthrough and MRT growth, which may be useful at the fuel/liner interface during this phase of the MagLIF implosion. For the MRT growth rate and feedthrough factors, the LLNL code, HYDRA, is used to benchmark with the analytic theory, and with experiments on the Z-machine [2]. This work was supported by DoE and NSF. \\[4pt] [1] S. A. Slutz, et. al, Phys. Plasmas 17, 056303 (2010).\\[0pt] [2] D. B. Sinars et. al, Phys. Plasmas 18, 056301 (2011). [Preview Abstract] |
Monday, November 11, 2013 11:42AM - 11:54AM |
BO7.00012: Hydrodynamic instabilities in interaction of laser radiation with a magnetized target Sergei V. Ryzhkov, Victor Kuzenov Laser-driven magneto-inertial fusion (MIF) allows to compress the preseeded magnetic field to thousands of teslas. Model of high pulse energy laser target interaction is presented. Richtmyer-Meshkov (R-M) instability is investigated for MIF systems. We have shown that there is a possibility to suppress the R-M instability by magnetic field. Modeling the impact of magnetic field on a single plasma jet formed at the ICF laser target compression is performed. It is shown that at the compression and heating of a plasma target by using a rapidly growing external magnetic field and laser radiation the R-M instability can be suppressed. Analysis of two-dimensional disturbances and composed structures, corresponding to the ``irregular'' regime is presented. We introduce the basic dimensionless parameters defining the solution of the problem. The NICA (Nonstationary Instruments and Codes for fusion Applications) code is developed and tested. Preliminary test results of magnetized plasma target compression by high energy laser pulses are shown. It can be argued that the magnetic field in terms of vortices plays a stabilizing role, which is manifested in the fact that the vortex structures dissipate in the presence of an externally applied magnetic field. [Preview Abstract] |
Monday, November 11, 2013 11:54AM - 12:06PM |
BO7.00013: Continuous conic imploding magneto-inertial fusion Yian Lei Magneto-inertial fusion (MIF) compresses a magnetized plasma target, combining the features of both magnetic confinement fusion (MCF) and inertial confinement fusion (ICF). We proposed a new MIF scheme in which the fusion fuel is continuously compressed by a large ratio conic implosion, as the fuel has been compressed to about a millionth of its original volume (about 1 cubic centimeter), the temperature rises to a few electron-volts and pre-ionized, a small single turn coil (STC) at the cone top then discharges to produce a very strong magnetic field in the fusion fuel, the discharge will magnetize the plasma and create a field reversed configuration (FRC) or theta-pinch in the plasma, as the compression goes on, the magnetized plasma will be further compressed to fusion burn. The implosion happens inside a solid cone coated or wetted by lead-bismuth (Pb-Bi) eutectic alloy (LBE). LBE is driven by high pressure air into the conic chamber to compress the very thin fuel. To minimize the amount of impurities in the fuel, the cone is pre-filled by LBE and a small fuel bubble is put in, then LBE sinks to bottom to create a large volume (about 1 cubic meter) and very thin bubble. This approach does not require artificial pre-ionization; the compression is continuous and accelerating because of the conic shape; a small sized STC producing high magnetic field is also a known technology. All these features should make the approach promising. [Preview Abstract] |
Monday, November 11, 2013 12:06PM - 12:18PM |
BO7.00014: A new concept of inertial magnetic confinement fusion with the ultra-intense laser system Kenjiro Takahashi We will present a new magnetic field machine generating strong magnetic field using by ultra-intense laser system and suggest a new concept of the fusion research with this system. High energy electron generation with the interaction of the solid target and short pulse laser is well-known phenomena. This hot electron jet produces high-intense magnetic field which surround the electron jet axis. Four laser beams separated with the beam splitters from one beam irradiate four solid targets at the same time, and four electron jets shaping small square product a uniform and strong magnetic field at the center of the square modeled on a single-turn coil driven by the hot electron. Furthermore, a same coil is produced by more four laser beams, and the two coils set on parallel to each other make a Helmholtz coil. Setting a thin metal liner on the center of the Helmholtz coil and implosion of the cavity in which a seed magnetic field driven by the Helmholtz coil with long pulse laser for ICF research compresses stronger magnetic field in the cavity. This system could generate extremely high-intense magnetic field. Such a strong magnetic field confines dense plasma of the fusion fuel. It is a new research concept of inertial magnetic confinement fusion. [Preview Abstract] |
Monday, November 11, 2013 12:18PM - 12:30PM |
BO7.00015: Multiple Experimental Platform Consistency at NIF L.R. Benedetti, M.A. Barrios, D.K. Bradley, D.C. Eder, S.F. Khan, N. Izumi, O.S. Jones, T. Ma, S.R. Nagel, J.L. Peterson, J.R. Rygg, B.K. Spears, R.P. Town ICF experiments at NIF utilize several platforms to assess different metrics of implosion quality. In addition to the point design--a target capsule of DT ice inside a thin plastic ablator--notable platforms include: (i)Symmetry Capsules(SymCaps), mass-adjusted CH capsules filled with DT gas for similar hydrodynamic performance without the need for a DT crystal; (ii)D:$^{3}$He filled SymCaps, designed for low neutron yield implosions to accommodate a variety of x-ray and optical diagnostics; and (iii)Convergent Ablators, SymCaps coupled with x-radiography to assess in-flight velocity and symmetry of the implosion over $\sim$1ns before stagnation and burn. These platforms are expected to be good surrogates for one another, and their hohlraum and implosion performance variations have been simulated in detail. By comparing results of similar experiments, we isolate platform-specific variations. We focus on the symmetry, convergence, and timing of x-ray emission as observed in each platform as this can be used to infer stagnation pressure and temperature. This work performed under the auspices of the U.S. Dept. of Energy by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-640865 [Preview Abstract] |
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