Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Plasma Physics
Volume 54, Number 15
Monday–Friday, November 2–6, 2009; Atlanta, Georgia
Session NO5: Fast Ignition |
Hide Abstracts |
Chair: Richard Petrasso, Massachusetts Institute of Technology Room: Hanover CDE |
Wednesday, November 4, 2009 9:30AM - 9:42AM |
NO5.00001: Anomalous Divergence of Laser-Generated Hot Electrons Generated in a Cone Geometry R.B. Stephens, K.U. Akli, E.M. Giraldez, T. Ma, M.S. Wei, T. Yabuuchi, F.N. Beg, H.S. McLean, A.G. MacPhee, M.H. Key, L. Divol, D. Hey, A.J. Kemp, D. Lason, S. Le Pape, A.J. Mackinnon, P.K. Patel, S.C. Wilks, V.M. Ovchinnikov, R.R. Freeman, L.D. Van Woerkom, C.D. Chen, Y.Y. Tsui, R. Fedosejevs Short pulse, lasers generate hot electrons at the cone tip in a Fast Ignition (FI) target. Previous flat foil studies suggest they propagate forward, diverging by $\sim$40$^{\circ}$ [1]. Those experiments used thin-walled cones in vacuum, allowing electrostatic fields on the outside surface of the cone to redirect errant electrons. In an FI target the cone will be embedded in blow-off plasma, removing those fields. We have emulated such conditions with thick-walled cones. Initial results suggest that electrons produced in such geometry diverge much more widely than seen in flat foils. The size of this effect and its dependence on tip size will be discussed.\par \vskip6pt \noindent [1] R.B.\ Stephens, {\it et al.}, {\it Phys.\ Rev.\ E} {\bf 69}, 066414 (2004). [Preview Abstract] |
Wednesday, November 4, 2009 9:42AM - 9:54AM |
NO5.00002: Resistive Stopping of Fast Electrons in Fast Ignition D.P. Higginson, B. Westover, T. Bartal, S. Chawla, T. Ma, M.S. Wei, C.D. Chen, D.S. Hey, P.K. Patel, H. Chen, M.H. Key, A.J. Mackinnon, A.G. MacPhee, H. McLean, S. Le Pape, K.U. Akli, R.B. Stephens, R.R. Freeman, L.D. Van Woerkom, F.N. Beg The mechanisms of fast electron generation and transport are of critical important to the fast ignition approach to inertial confinement fusion. Fast electrons in multi-layered Al/Cu/Al/Ag/Al targets were created on the Titan Laser (150 J, 0.7 ps, 4x10$^{19}$ W/cm$^{2})$. The relative importance of resistive and collisional stopping effects was studied by varying the Ag layer depth. K shell fluorescence from Cu and Ag were measured with a highly oriented pyrolytic graphite spectrometer, which was cross-calibrated with a single photon counting charged coupled device. Analysis is performed with the collisional Monte Carlo code ITS 3.0 by injecting hot electrons into a cold target using the absolutely calibrated K shell yeilds as constraints. A comparison is made with the hybrid/PIC code LSP to demonstrate resistive effects [1]. This work was supported by the US DOE under contracts DE-FC02-04ER54789 (Fusion Science Center) and DE-FG-02-05ER54834 (ACE).\\[4pt] [1] M.S.Wei et al., this conference. [Preview Abstract] |
Wednesday, November 4, 2009 9:54AM - 10:06AM |
NO5.00003: Integrated Fast-Ignition Experiments on OMEGA W. Theobald, C. Stoeckl, V.Yu. Glebov, F.J. Marshall, K.S. Anderson, R. Betti, R.S. Craxton, D.D. Meyerhofer, P.M. Nilson, T.C. Sangster, A.A. Solodov, J.A. Frenje, R.D. Petrasso, D. Hey, P.K. Patel, R.B. Stephens, R. Lauck, P.A. Norreys Integrated fast-ignition experiments using room-temperature cone-in-shell targets have begun at the Omega/Omega EP Laser Facility. Empty 40-\textit{$\mu $}m-thick CD shells are imploded using 54 UV beams. At the time of peak compression, a short-pulse ($\sim $10 ps) IR laser with energy $>$1 kJ is focused into the tip of the hollow cone. A three-fold increase in time-integrated 2- to 7-keV x-ray emission was observed, indicating that fast-electron energy is coupled into the core. Neutron detectors are strongly affected by the emission of an intense \textit{$\gamma $}-ray pulse, making it challenging to measure neutron yield. Significant reduction of the \textit{$\gamma $}-ray background has been achieved by gating the MCP detector and using a liquid scintillator to suppress the afterglow. The D$_{2}$ neutron yield is being measured. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement Nos. DE-FC52-08NA28302, DE-FC02-04ER54789, and DE-FG02-05ER54839. [Preview Abstract] |
Wednesday, November 4, 2009 10:06AM - 10:18AM |
NO5.00004: Integrated Fast ignition Experiments on the NIF C.D. Chen, Pravesh Patel, Peter Amendt, Dan Clark, Bruce Cohen, Dan Hey, Laurent Divol, Doug Homoelle, Nobuhiko Izumi, Andreas Kemp, Mike Key, David Larson, Barbara Laskinski, Sebastien Le Pape, Andrew Mackinnon, Andrew MacPhee, Harry McLean, Don Meeker, Yuan Ping, Hank Shay, David Strozzi, Max Tabak, Richard Town, Scott Wilks The National Ignition Facility at LLNL will provide the first capability for assembling the fuel mass and $\rho $R required for full-scale Fast Ignition. A quad of NIF beams converted to short-pulse operation will provide an ignitor pulse with which to determine the efficiency of fast electron energy coupling to the ignition hot spot. In this talk we review progress in the design of fast ignition core heating experiments that use: (i) 600 kJ of NIF laser energy in indirect-drive to compress DT (cryo) and CD (warm) capsules, and (ii) 8 kJ of ARC at 5 ps duration injected via a Au cone to heat the assembled fuel. We describe 2-D integrated hohlraum and capsule designs that optimize the peak density, $\rho $R and spatial uniformity of the fuel assembly around the cone tip. The interaction of the short-pulse ignitor beam in the cone is simulated with the 3-D PSC explicit particle-in-cell (PIC) code, and the subsequent transport of the electrons and core heating calculated with the LSP hybrid transport code. [Preview Abstract] |
Wednesday, November 4, 2009 10:18AM - 10:30AM |
NO5.00005: Transport Simulations for Fast Ignition on NIF D.J. Strozzi, M. Tabak, D.P. Grote, R.P.J. Town, A.J. Kemp Calculations of the transport and deposition of a relativistic electron beam into fast-ignition fuel configurations are presented. The hybrid PIC code LSP is used, run in implicit mode and with fluid background particles. The electron beam distribution is chosen based on explicit PIC simulations of the short-pulse LPI. These generally display two hot-electron temperatures, one close to the ponderomotive scaling and one that is much lower. Fast-electron collisions utilize the formulae of J. R. Davies [S. Atzeni et al., Plasma Phys. Controlled Fusion 51 (2009)], and are done with a conservative, relativistic grid-based method similar to Lemons et al., J. Comput. Phys. 228 (2009). We include energy loss off both bound and free electrons in partially-ionized media (such as a gold cone), and have started to use realistic ionization and non-ideal EOS models. We have found the fractional energy coupling into the dense fuel is higher for CD than DT targets, due to the enhanced resistivity and resulting magnetic fields. The coupling enhancement due to magnetic fields and beam characteristics (such as angular spectrum) will be quantified. [Preview Abstract] |
Wednesday, November 4, 2009 10:30AM - 10:42AM |
NO5.00006: Simulations of Directly-Driven Cone-in-Shell Implosions R.P.J. Town, D.S. Clark, M.M. Marinak, H.D. Shay, M. Tabak, D.S. Hey, P.K. Patel, K.S. Anderson, R. Betti, W. Theobald In fast ignition a short-pulse high intensity laser is used to generate relativistic electrons that subsequently deposit their energy into the compressed fuel to initiate a propagating burn wave. A high-density cone is often inserted into the capsule to allow a clear path for the ignition laser to the compressed fuel. The presence of the cone alters the dynamics in two ways from a spherically symmetric implosion. First, x-ray preheat can be absorbed by the cone causing the cone material to expand ahead of the imploding fuel leading to mixing of the high-Z cone material into the fuel. Second, the stagnation of the fuel near the cone can launch a jet into the cone increasing the transport distance of the short-pulse generated relativistic electrons. This paper reports on HYDRA simulations of directly driven OMEGA-scale plastic capsule implosions. [Preview Abstract] |
Wednesday, November 4, 2009 10:42AM - 10:54AM |
NO5.00007: Simulations of Electron-Beam Transport in Solid-Density Targets and the Role of Magnetic Collimation A.A. Solodov, M. Storm, J.F. Myatt, R. Betti, D.D. Meyerhofer, P.M. Nilson, W. Theobald, C. Stoeckl Three-dimensional simulations of solid-target electron-transport experiments at the Laboratory for Laser Energetics have been performed, using the hybrid-PIC code \textit{LSP}. The experimentally observed fast-electron divergence half-angle of 16\r{ } in the target was reproduced assuming an initial divergence half-angle of $\sim $56\r{ }, close to the value expected from the simple ponderomotive acceleration formula: $\theta _{1/2} =\tan ^{-1}\left[ {\sqrt {2/\left( {\gamma -1} \right)} } \right]$, where \textit{$\gamma $} is the electron relativistic factor. The simulations accurately reproduce the details of the electron transport observed in the experiment. The electron beam propagates as an expanding annulus that breaks into filaments because of the resistive filamentation instability. The electron-beam partial collimation and annular propagation is due to the resistive azimuthal magnetic field generated at the outer edge of the electron beam. Features of the electron-beam transport through the cone tip of fast-ignition cone-in-shell targets will also be discussed. This work was supported by the U.S. Department of Energy under Cooperative Agreement Nos. DE-FC02-04ER54789 and DE-FC52-08NA28302. [Preview Abstract] |
Wednesday, November 4, 2009 10:54AM - 11:06AM |
NO5.00008: LSP modeling of fast electron transport and K-shell x-ray production in multiple-layer solid targets H.K. Chung, M.S. Wei, B. Westover, D.P. Higginson, B.S. Paradkar, F.N. Beg, K.U. Akli, R.B. Stephens, T. Ma, P.K. Patel, M.H. Key, H.S. McLean, J. Myatt Understanding of fast electrons transport is crucial for Fast Ignition of Inertial Confinement Fusion. In experiments, transport of high intensity laser produced electrons is generally characterized by measuring fast electron produced K-shell photons using x-ray spectroscopic technique. Results from recent experiments performed at the Titan laser show that Ag K$\alpha $ yield is insensitive to the buried depth in Al/Cu/Al/Ag/Al targets [1]. We have performed a series of 2D hybrid/PIC simulations using LSP code to model fast electron transport and K$\alpha $ production in such targets to study underlying physics. The details of simulation results along with comparison with experimental data will be presented. [1] D.P. Higginson et al., this conference. [Preview Abstract] |
Wednesday, November 4, 2009 11:06AM - 11:18AM |
NO5.00009: Numerical study of the effects of preformed plasma on the fast electron transport B.S. Paradkar, M.S. Wei, T. Yabuuchi, F.N. Beg, R.B. Stephens Recent short pulse laser-solid interaction experiments performed at ILE, Japan [T. Yabuuchi et. al., Bull Am Phys Soc 2008.DPP.JP6.113] have reported pre-formed plasma causing a ring-like K$\alpha $ x-ray emission around the central bright spot from a Cu fluorescence layer buried between Al layers. To explain this, we have performed a series of 2D hybrid/PIC simulations with LSP code to model fast electron transport in pre-formed plasma. The pre-formed plasma and corresponding thermoelectric azimuthal magnetic fields are obtained by simulating the long pulse laser-solid interaction with 2-D radiation hydrodynamic code, h2d [larsen@casinc.com]. The LSP simulations suggest that the ring structure is due to the fast electrons deflected by B-fields into the pre-plasma and then reflected back by electrostatic sheath fields excited near the transverse edge of plasma plume. The details of simulation results along with comparison with experimental data will be presented. [Preview Abstract] |
Wednesday, November 4, 2009 11:18AM - 11:30AM |
NO5.00010: Resistive filamentation and collimation of relativistic electron beams in the fast ignition scenario Javier Honrubia, Arnaud Debayle, Emmanuel D'Humieres, Samuel Micheau, Vladimir Tikhonchuk We have reported recently resistive filamentation and magnetic collimation of relativistic electron beams with currents around 1 GA and 10 -- 20 ps pulses [J.J. Honrubia and J. Meyer-ter-Vehn, \textit{Nucl. Fus. }\textbf{46}, L25 (2006): \textit{Plasma Phys. Control. Fus}. \textbf{51}, 014008 (2009).]. Beam collimation due to self-generated magnetic fields reduces significantly the ignition threshold of imploded fuel capsules and depends strongly on the source size and the initial distribution function of relativistic electrons. We will demonstrate fast ignition integrated simulations in 2D axi-symmetric geometry including 1) laser-driven relativistic electron sources obtained by 2D PIC simulations for actual laser intensities and pulse durations, 2) optimized configurations of the assembled fuel in re-entrant cone targets, and 3) interaction of fast electrons with the cone tip. The material of the cone tip has been selected as a compromise between hydrodynamic and electron transport requirements to guarantee the cone tip survival and to minimize the electron energy loss and scattering. We will provide estimates for the ignition energies. [Preview Abstract] |
Wednesday, November 4, 2009 11:30AM - 11:42AM |
NO5.00011: Numerical simulations of laser hole boring for fast ignition fusion R. Trines, P. Norreys, G. Sarri, M. Borghesi Hole boring fast ignition is an attractive scenario for fast ignition (FI) fusion, as it requires much simpler targets than cone guided FI, a clear advantage for future operations at high repetition rate. In a recent experiment at the Rutherford Appleton Laboratory, hole boring has been investigated in a laser parameter regime (25 ps, $10^{18}$ W/cm$^2$) that is relevant to realistic FI scenarios but has scarcely been investigated before. We have conducted particle-in-cell simulations of laser-driven hole boring in plasma that follow the conditions of this experiment, i.e. at the critical density and at 1\% of the critical density. At the lower density most of the laser energy is transmitted through the plasma, while at the higher density most of the energy is absorbed, leading to large differences in the evolution of the laser-driven channel. Good agreement between the numerical and experimental results has been obtained. Possible physical mechanisms underlying the hole boring process and the consequences of our findings for hole boring FI will be discussed. [Preview Abstract] |
Wednesday, November 4, 2009 11:42AM - 11:54AM |
NO5.00012: Modeling the Modification of Escaping Energetic Electron Spectrum by Target Charging with LSP A. Link, R.R. Freeman, D.W. Schumacher, L.D. Van Woerkom, M.S. Wei, F.N. Beg, M.H. Key, A.J. Mackinnon, P.K. Patel, R.B. Stephens Ultraintense lasers interacting with solid density plasma transfer their energy to electrons at the laser-plasma interface (LPI). The resulting electron spectrum is typically acquired by direct measurement of the electrons which escape the plasma. A 1D capacitor model and 2D LSP simulations were used to determine the relationship between the externally measured spectrum and the in situ spectrum. A time and space varying electron source was generated consistent with electron temperature scaling laws and experimentally observed laser to electron energy coupling as the input for the models. Results will be presented for the modification of the escaped electron spectrum's energy, angular, and temporal properties for a collisional plasma with pulse durations of 70 fs and 700 fs. [Preview Abstract] |
Wednesday, November 4, 2009 11:54AM - 12:06PM |
NO5.00013: Characteristics of fast electrons generated in laser-cone interaction for the HiPER project Samuel Micheau, Arnaud Debayle, Emmanuel D'Humieres, Javier Honrubia, Marco Borghesi, Michael Geissler The fast ignition scheme considered for future facilities such as HiPER relies on the efficient generation and propagation of a relativistic electron beam to ignite a pre-compressed fusion pellet. Conical targets have proven to be very attractive to produce high-energy electrons close to the core plasma. However, hybrid PIC simulations have shown that the coupling efficiency between the high-energy electrons and the dense core is highly sensitive to the initial properties of the fast electrons. Here, we present 2D-PIC simulations with the code ILLUMINATION of the laser-cone interaction. We focus on the characteristics of the fast electron beam emitted at the cone tip, such as divergence, temporal evolution, energy and spatial distributions, as a function of the interaction parameters, so as to reach the requirements for fast ignition. [Preview Abstract] |
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