Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Plasma Physics
Volume 56, Number 16
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session UO6: Shock Ignition and Laser Plasma Instabilities |
Hide Abstracts |
Chair: Pat McKenty, Laboratory for Laser Energetics Room: Ballroom G |
Thursday, November 17, 2011 2:00PM - 2:12PM |
UO6.00001: High-Intensity Shock-Ignition Experiments in Spherical and Planar Geometry W. Theobald, M. Hohenberger, K.S. Anderson, R. Betti, T.R. Boehly, J.A. Delettrez, V.Yu. Glebov, V.N. Goncharov, S.X. Hu, F.J. Marshall, D.D. Meyerhofer, R. Nora, T.C. Sangster, W. Seka, C. Stoeckl, B. Yaakobi, A. Casner, J.A. Frenje, M. Lafon, X. Ribeyre, G. Schurtz Shock ignition\footnote{R. Betti\textit{ et al.}, Phys. Rev. Lett. \textbf{98}, 155001 (2007).} has recently gained much attention as an inertial confinement fusion concept that assembles thermonuclear fuel to high areal densities and then ignites it by launching a strong shock wave into compressed fuel. OMEGA experiments study the shock-ignition concept using various types of adiabat-shaping laser pulses and a high-intensity spike. High-intensity laser--plasma interaction experiments in spherical and planar geometries provide valuable data on backscattering, fast-electron generation, and shock-wave timing for intensities $>$1 $\times $ 10$^{15}$ W/cm$^{2}$. A significant energy transfer into fast electrons was measured with hot-electron temperatures $>$100~keV in planar targets and $\sim $50 keV in spherical targets. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 2:12PM - 2:24PM |
UO6.00002: Shock Ignition in Non-Cryogenic Metal-Gas Targets on the National Ignition Facility L. John Perkins, C. Cerjan, V. Smalyuk, D. Bailey, A. Comley, W. Garbett, P. McKenty, B. Cheng Shock ignition offers the possibility of volumetric ignition and burn in single-shell, room-temperature gas targets on the National Ignition Facility. We are investigating whether the high fusion energy gains potentially available with shock ignition in cryogenic DT targets on NIF (\textit{L.J.Perkins et al, PRL 103 (2009)}) can be traded for modest gains and yields in such platforms. If so, being non-cryogenic with simple single-shell construction and medium-pressure gas fill, they should easier to field and diagnose. The targets are characterized by a thick, graded-density Be-Au ablator-pusher shell with low in-flight-aspect-ratios. Because the high-Z Au shell reflects Bremsstrahlung, such targets are capable of volumetric ignition at temperatures of around 4keV with low shell velocities around 1.5e7cm/s. Gas targets are inherently low gain ($\le $10) so they are probably not IFE relevant. The ultimate performance will be determined by degree and control of high-Z mix in the gas. Simulations indicate that we can potentially trade fusion yield for good ignition fall-line behavior by tuning gas pressure and shock launch time. [Preview Abstract] |
Thursday, November 17, 2011 2:24PM - 2:36PM |
UO6.00003: Shock-Ignition Target Designs for OMEGA R. Nora, R. Betti, K.S. Anderson, W. Theobald, G. Schurtz, M. Lafon, X. Ribeyre, A. Casner Shock-ignition designs of cryogenic targets on OMEGA are presented. The targets are designed to be an 83-\textit{$\mu $}m DT shell with a 10-\textit{$\mu $}m plastic ablator and outer radius of 430 \textit{$\mu $}m being driven by 25 kJ of laser energy in a triple-picket design. Using the triple-picket laser design makes it possible for the OMEGA Laser System to maximize the energy on target while shaping the adiabat to reduce the growth of Rayleigh--Taylor instabilities. One-dimensional simulations using the hydrodynamic code \textit{LILAC} indicate the cryogenic target achieves neutron yields of 4.6 $\times $ 10$^{13}$ and areal densities of 450~mg/cm$^{3}$. Two-dimensional \textit{DRACO} simulations, including ice roughness and multimode laser-imprint perturbations, will also be presented. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement Nos. DE-FC52-08NA28302 and DE-FC02-04ER54789. [Preview Abstract] |
Thursday, November 17, 2011 2:36PM - 2:48PM |
UO6.00004: Simulations of Shock-Ignition Targets for the NIF K.S. Anderson, R. Betti, R.S. Craxton, T.J.B. Collins, J.A. Marozas, P.W. McKenty, S. Skupsky, L.J. Perkins Shock ignition\footnote{ R. Betti\textit{ et al.}, Phys. Rev. Lett. \textbf{98}, 155001 (2007).} is a low-drive energy alternative to standard hot-spot ignition at the National Ignition Facility (NIF). A cryogenic shock-ignition design for the NIF with a thick plastic ablator is described. The target is driven by a triple-picket pulse shape\footnote{ V. N. Goncharov\textit{ et al.}, Phys. Rev. Lett. \textbf{104}, 165001 (2010).} to simplify shock tuning and improve stability via adiabat shaping.\footnote{ V. N. Goncharov\textit{ et al.}, Phys. Plasmas \textbf{10}, 1906 (2003).}$^{,}$\footnote{ K. Anderson and R. Betti, Phys. Plasmas \textbf{11}, 5 (2004).} Results from one- and two-dimensional simulations will assess the robustness of this target due to various sources of nonuniformity including ice roughness, beam geometry, laser power balance, laser imprint, and hot-electron energy deposition. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302 and DE-FC02-04ER54789. [Preview Abstract] |
Thursday, November 17, 2011 2:48PM - 3:00PM |
UO6.00005: Absorption by the Two-Plasmon-Decay Instability in Direct-Drive Implosions W. Seka, D.H. Froula, D.H. Edgell, J.F. Myatt, R.W. Short, I.V. Igumenshchev, V.N. Goncharov, A.V. Maximov There is mounting evidence that the two-plasmon-decay instability near $n_{c}$/4 absorbs non-negligible amounts of the incident laser energy in direct-drive implosion experiments. Most of this energy is deposited as thermal energy between 0.25 $\le \quad n_{c}$/$n_{e} \quad \le $ 0.2 (typical Landau cutoff location) with a small fraction going into energetic electrons. This conjecture is based on time-resolved 3\textit{$\omega $}/2 emission, scattered light at the laser wavelength, energetic-electron measurements, neutron and x-ray bang times, and comparison with hydrodynamic simulations. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 3:00PM - 3:12PM |
UO6.00006: Energetic-Electron Generation in Two-Plasmon-Decay Instabilities in Direct-Drive Inertial Confinement Fusion R. Yan, A.V. Maximov, C. Ren, F.S. Tsung We present a series of 2-D particle-in-cell (PIC) simulations of the long-term ($\sim $10-ps) nonlinear behavior of the two-plasmon-decay (TPD) instability for parameters relevant to inertial confinement fusion. The simulations used the full PIC code \textit{OSIRIS.} When the TPD threshold is exceeded, the simulation results show that significant laser absorption and energetic-electron ($>$50-keV) generation occur in the nonlinear stage. The energetic electrons are mostly forward-directed, which poses a preheating risk for targets. The hot electrons are stage-accelerated from the low-density region to the high-density region. New modes with small phase velocities develop in the low-density region after saturation, forming the first stage for electron acceleration. A fluid code has been developed to show that similar new TPD modes can develop with steady-state ion-density fluctuations. The laser absorption and hot-electron production from these 2-D plane-wave--driven PIC simulations are higher than experimental observations, which could indicate uncertainty in the simulation parameters or the importance of nonideal factors such as speckle structure in the actual laser profile. This work was supported by U.S. Department of Energy Grants No. DE-FG02-06ER54879, DE-FC02-04ER54789, DE-FG52-06NA26195, DE-FG52-09NA29552, and DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 3:12PM - 3:24PM |
UO6.00007: Energy Transfer Between Crossing Laser Beams in the Plasmas of Direct-Drive ICF A.V. Maximov, J.F. Myatt, R.W. Short, I.V. Igumenshchev, D.H. Edgell, W. Seka Nonlinear interaction between multiple crossing laser beams through low-frequency ion-acoustic waves is an important effect in direct-drive inertial confinement fusion (ICF) targets. It can lead to energy transfer between the beams and, consequently, increases the laser scattering and decreases the laser absorption.\footnote{I. V. Igumenshchev\textit{ et al.}, Phys. Plasmas \textbf{17}, 122708 (2010).} The non-paraxial model of coupled Maxwell's and hydrodynamic equations\footnote{A. V. Maximov\textit{ et al.}, Phys. Plasmas \textbf{11}, 2994 (2004).} has been used to study the nonlinear propagation of crossing laser beams in the plasma corona for different angles of incidence. This model is used to study the seeding of crossed-beam energy transfer by turning laser beams and by the transmitted part of opposing laser beams. The comparison between the results of the non-paraxial model and the results of the ray-based model used in large-scale simulations$^{1}$ suggests modifications to large-scale modeling of the plasma corona in direct-drive ICF. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 3:24PM - 3:36PM |
UO6.00008: A Quasilinear Model for the Two-Plasmon-Decay Instability in Inhomogeneous Plasmas J.F. Myatt, J. Zhang, A.V. Maximov, R.W. Short, D.F. DuBois, D.A. Russell, H.X. Vu A quasilinear-Zakharov model of two-plasmon decay is described and its validity tested, first by comparing the diffusion of test-particle orbits against quasilinear predictions for cases of interest to polar-drive ignition, and second by comparing heated electron-distribution functions with reduced particle-in-cell calculations using the code RPIC. The expected preheat arising from the predicted hot-electron temperature and hot-electron flux from the model calculations is discussed. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 3:36PM - 3:48PM |
UO6.00009: Experimental Optimization of Direct-Drive Implosions with Cross-Beam Energy Transfer D.H. Froula, I.V. Igumenshchev, W. Seka, D.H. Edgell, V.N. Goncharov Cross-beam energy transfer (CBET) in direct-drive implosions is measured to reduce the hydrodynamic efficiency of the laser drive. The outer rays of each beam interact through the ion-acoustic waves to extract energy from the central rays of each beam. This accounts for an $\sim $10{\%} loss of absorption, which results in an $\sim $20{\%} reduction in hydro-efficiency as measured by the scattered light and x-ray bang time. Experiments that reduce the laser energy in the outer rays by reducing the ratio of the laser spot size to target diameter by $R_{beam}$/$R_{target}$ = 60{\%} are shown to eliminate CBET and significantly increase the hydrodynamic coupling; however, the reduction in laser spot size leads to irradiation nonuniformities. An optimum laser spot size is experimentally determined that maximizes neutron yield by balancing the reduced CBET with the illumination nonuniformities. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 3:48PM - 4:00PM |
UO6.00010: Measurements of Hot Electrons Produced by Two-Plasmon Decay in Near Direct-Drive-Ignition Plasma Conditions D.T. Michel, B. Yaakobi, S.X. Hu, R.S. Craxton, J.F. Myatt, W. Seka, D.H. Edgell, V.N. Goncharov, D.H. Froula Measurements of hot-electron generation by two-plasmon-decay instability have been made in plasmas relevant to direct-drive-ignition plasma conditions. Four 351-nm, 2-ns-long beams on the OMEGA EP Laser provided the high energy (10 kJ) necessary to produce overlap laser intensities from 1 to 7 $\times $ 10$^{14}$ W/cm$^{2}$ in large 1-mm-diam laser spots. These laser conditions produced coronal electron temperatures $>$2 keV with density scale lengths at $n_{cr}$/4 greater than 400 \textit{$\mu $}m in CH plasmas. The total number of hot electrons increases exponentially over nearly four orders of magnitude and the hot-electron temperature increases from 30 keV to 110 keV. In this intensity range, changing the ablator material from CH to Al reduced the number of hot electrons by an order of magnitude over the entire range. Experiments to measure the angular dependence of the electrons and the coupling of these electrons to direct-drive implosions will be presented. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 4:00PM - 4:12PM |
UO6.00011: Three-Dimensional Numerical Investigation of Oblique Laser Irradiation of Planar Targets J.A. Delettrez, W. Seka, D.H. Froula, T.J.B. Collins, M.M. Marinak The two-plasmon-decay (TPD) instability from multiple overlapped beams has been shown to depend on the overlapped beam intensity.\footnote{C. Stoeckl\textit{ et al.}, Phys. Rev. Lett. \textbf{90}, 235002 (2003).} Recent analysis indicates that the gain increases with the angular tilt of the group of beams participating in the TPD process.\footnote{R. W. Short, this conference.} This dependence on tilt affects the TPD gain in polar-drive\footnote{S. Skupsky\textit{ et al.}, Phys. Plasmas \textbf{11}, 2763 (2004).} implosions in which one or more rings are pointed away from the target radial direction. Experiments will be performed on planar targets that will be tilted with respect to the beam axis to evaluate the TPD. Simulations with the 3-D code \textit{HYDRA}\footnote{M. M. Marinak\textit{ et al.}, Phys. Plasmas \textbf{8}, 2275 (2001).} will provide the conditions near the quarter-critical surface needed in the TPD analysis of the experimental results. The results of the simulations, including ray-trace information at the quarter-critical surface, will be presented. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 4:12PM - 4:24PM |
UO6.00012: Convective Multibeam Two-Plasmon Decay for Spherical and Planar Irradiation Geometries R.W. Short, J.F. Myatt There is mounting evidence that the two-plasmon-decay (TPD) instability near $n_{c}$/4 absorbs non-negligible amounts of the incident laser energy in direct-drive implosion experiments.\footnote{W. Seka \textit{et al}., this conference.} Some of this energy is imparted to hot electrons that can preheat the compressed core and degrade implosion efficiency, while the remainder contributes to heating the bulk-electron distribution. How much energy goes into hot electrons and how these electrons interact with the core depends on the spectrum, propagation direction, and amplitude of the plasma waves produced by TPD. To investigate these questions the dependence of TPD instability gain on the geometry of the irradiating beams is investigated. It is found that TPD depends on the collective intensity of several beams when the beams are near normal incidence,\footnote{C. Stoeckl\textit{ et al.}, Phys. Rev. Lett. \textbf{90}, 235002 (2003).} but becomes essentially a single-beam process when the beams are more oblique. Consequences for spherical and planar experiments will be discussed. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 4:24PM - 4:36PM |
UO6.00013: Particle-in-cell Simulations of laser plasma interactions near the quarter critical surface Frank Tsung, B.B. Afeyan, W.B. Mori We present simulation results on the laser-plasma interaction near the quarter critical surface under conditions relevant to inertial fusion. Under these conditions, the high frequency hybrid instability (HFHI) where the backward going daughter wave have mixed polarizations, may be important in both the early and nonlinear regimes. We find in high temperature plasmas where HFHI modes are important that the absorption level can be high (up to 40\%) for systems which are below the two plasmon threshold. This result implies, for laser pulses with a long (compared to the instability growth time, in the order of 1ps) rise time, the mixed polarization modes with small perpendicular wavenumber can significantly modify the plasma conditions before the laser greatly exceeds the threshold. We also will present results for when the laser intensity is adiabatically increased. Other nonlinearities such as the generation of hot electrons, the generation of half harmonics, and the effects of overlapping beams will also be discussed. [Preview Abstract] |
Thursday, November 17, 2011 4:36PM - 4:48PM |
UO6.00014: ABSTRACT WITHDRAWN |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700