Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012; Providence, Rhode Island
Session GO5: Fast Ignition/Shock Ignition Experiment |
Hide Abstracts |
Chair: Hiroshi Sawada, University of Nevada, Reno Room: 552AB |
Tuesday, October 30, 2012 9:30AM - 9:42AM |
GO5.00001: Shock-Ignition Studies in Planar Geometry on OMEGA M. Hohenberger, W. Theobald, S.X. Hu, R. Betti, T.R. Boehly, D.D. Meyerhofer, T.C. Sangster, W. Seka, C. Stoeckl, B. Yaakobi, A. Casner, X. Ribeyre, G. Schurtz In the shock-ignition concept,\footnote{R. Betti \textit{et al.}, Phys. Rev. Lett. \textbf{98}, 155001 (2007).} the gain in an inertial confinement fusion (ICF) experiment is enhanced compared to conventional hot-spot ignition through the separation of the fuel assembly and ignition stages. A strong, spherically converging shock of several hundred megabar is launched into the cold fuel assembly of an ICF target by a high-intensity laser spike of $\sim $10$^{16}$ W/cm$^{2}$ at the end of the assembly pulse, igniting the fuel. We present results from recent OMEGA experiments in planar geometry studying the shock-ignition concept and strong shock generation in the presence of a pre-plasma. These experiments provide important data on backscattering, hot-electron generation, and shock strength at shock-ignition relevant intensities of up to $\sim $5 $\times $ 10$^{15}$ W/cm$^{2}$. 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] |
Tuesday, October 30, 2012 9:42AM - 9:54AM |
GO5.00002: Experiments on 1,000 km/s flyer acceleration and collisions Max Karasik, J.L. Weaver, Y. Aglitskiy, D.M. Kehne, S.T. Zalesak, A.L. Velikovich, J. Oh, V. Serlin, S.P. Obenschain We will present results from follow-on experiments to the record-high velocities achieved using the ultra-uniform deep-uv drive of the Nike KrF laser [Karasik et al, Phys. Plasmas 17, 056317 (2010)], in which highly accelerated planar foils of deuterated polystyrene were made to collide with a witness foil to produce $\sim1$~Gbar shock pressures and result in heating of matter to thermonuclear temperatures. Such velocities may indicate a path to lower minimum energy required for central ignition. Still higher velocities and higher target densities are required for impact fast ignition. New results give velocity of $>1,100$~km/s achieved through improvements in pulseshaping. Variation of second foil parameters results in significant change in fusion neutron production on impact. In-flight target density is inferred from target heating upon collision via DD neutron time-of-flight ion temperature measurement. Availability of pressures generated by collisions of such highly accelerated flyers may provide an experimental platform for study of matter at extreme conditions. Work is supported by US DOE (NNSA). [Preview Abstract] |
Tuesday, October 30, 2012 9:54AM - 10:06AM |
GO5.00003: Extremely high pressure generation by implosion plasmas with cone-in shell targets Keisuke Shigemori, Yoichiro Hironaka, Hideo Nagatomo, Shinsuke Fujioka, Hiroyuki Shiraga, Mitsuo Nakai, Hiroshi Azechi, Atsushi Sunahara, Tomoyuki Johzaki, Toshihiko Kadono, Katsuya Shimizu We propose a novel scheme to generate ultra-high pressure by using laser implosion plasma. Experiments were conducted at GEKKO-XII laser facility at ILE, Osaka University. Nine of twelve beams irradiated the cone-in shell targets. Fundamental experimental conditions were same as the typical fast ignition experiments. The targets were cone (Au)-in-CD shell, whose cone tip diameter was 100 $\mu $m. Aluminum or gold witness plates with small ``hole'' (diameter: 40$\sim $50 $\mu $m) were embedded onto the tip of the cone in order to measure shock breakout timings by a streaked optical pyrometer (SOP). The thickness and hole depth of the witness plates were 10 -- 100 $\mu $m and 5 -- 40 $\mu $m, respectively. From the time difference of shock breakout at the stepped witness plates, shock velocity was directly obtained. We estimated the pressure by the measured shock velocity and an extrapolation of previous EOS measurements. [Preview Abstract] |
Tuesday, October 30, 2012 10:06AM - 10:18AM |
GO5.00004: Monochromatic 8.05-keV Flash Radiography of Imploded Cone-in-Shell Targets W. Theobald, A.A. Solodov, C. Stoeckl, V.Yu. Glebov, S. Ivancic, F.J. Marshall, G. McKiernan, C. Mileham, T.C. Sangster, F.N. Beg, C. Jarrott, E. Giraldez, R.B. Stephens, M.S. Wei, M.H. Key, H. McLean, J. Santos Fast ignition has the potential of high fusion gains through the ignition of massive DT fuel assemblies. The cone-in-shell target concept might be one way of achieving this goal. Integrated experiments on OMEGA have demonstrated $\sim $4{\%} coupling efficiency of short-pulse laser energy into the compressed target.\footnote{W. Theobald \textit{et al.}, Phys. Plasmas \textbf{18}, 056305 (2011).} An improved target design has been developed with a low-$Z$ cone tip. The goal was to validate 2-D radiation--hydrodynamic modeling predictions of the new target design. The technique used was flash radiography from a monochromatic 8.05-keV x-ray source.\footnote{ J. A. King\textit{ et al.}, Appl. Phys. Lett. \textbf{86}, 191501 (2005).} Cu foils were irradiated by the 1.5-kJ, 10-ps OMEGA EP short-pulse laser to generate a bright Cu K$_{\alpha }$ area backlighter source, which was used in combination with monochromatic imaging with a spherical Bragg crystal to backlight the cone-in-shell implosions at various times around peak compression. Flash radiography provides high-quality images of the fuel assembly with $\sim $10-ps time resolution and $\sim $10-\textit{$\mu $}m spatial resolution. This work was supported by the U.S. Department of Energy under Cooperative Agreement Nos. DE-FC52-08NA28302 and DE-FC02-04ER54789. [Preview Abstract] |
Tuesday, October 30, 2012 10:18AM - 10:30AM |
GO5.00005: Study of Fast Electron Energy Deposition into Imploded High Density Plasma Using Cu-Doped CD Shell Targets Leonard Jarrott, M.S. Wei, H. Sawada, W. Theobald, A.A. Solodov, C. Mcguffey, R.B. Stephens, C. Stoeckl, C. Mileham, F. Marshall, J. Delettrez, R. Betti, P.K. Patel, H. McLean, C. Chen, M.H. Key, T. Doeppner, T. Yabuuchi, T. Iwawaki, H. Habara, A. Greenwood, N. Alfonso, D. Hoover, E. Giraldez, F.N. Beg Fast electron spatial energy deposition into the imploded high density plasma has been characterized for the first time in an integrated cone-guided Fast Ignition experiment. This work uses the OMEGA beams (18kJ) for fuel assembly, and the high intensity EP beam (10ps, 0.5-1.5kJ, I$_{peak}$ $>$ 10$^{19}$ W/cm$^{2}$), focused onto the inner cone tip, to produce fast electrons. Energy deposition is diagnosed via Cu K-shell radiation from the Cu-doped CD shell. Results indicate Ka yield scaling with EP energy. Cu Ka distribution agrees with DRACO modeling. Ka images also suggest electrons being produced roughly 100$_{\mu}$m away from the cone tip, consistent with pre-plasma filling the cone. Comparison of experimental data with modeling will be presented. [Preview Abstract] |
Tuesday, October 30, 2012 10:30AM - 10:42AM |
GO5.00006: The progress in the neutron diagnostics in the Fast Ignition experiment with GEKKO XII and LFEX Yasunobu Arikawa, Takahiro Nagai, Yuki Abe, Sadaoki Kojima, Shohei Sakata, Hiroaki Inoue, Shinsuke Fujioka, Nobuhiko Sarukura, Mitsuo Nakai, Hiroyuki Shiraga, Hiroshi Azechi In the fast ignitor experiment the neutron diagnostics is very challenging due to too large backgrounds originated from hard X ray. In the Fast Ignition integrated experimental campaign held in 2010 in GEKKO XII and LFEX facility in Institute of Laser Engineering Osaka (ILE), the Xylen based new liquid scintillator coupled with the gated photomultiplier tube has successfully recorded neutron signal with heating the energy of up to 400 J. However there was significant large background in the signal originated from neutrons via ($\gamma $,n) reaction from the target chamber wall. The neutron collimator was developed and implemented to suppress these neutron backgrounds. We succeeded to record a very clear neutron signals in every shot in the fast ignitor experimental campaign held in July 2012 with the heating laser energy of around 1000 J with the pulse width of 2.2 ps. The details of the detector and the result of the fast ignition experiment will be presented. [Preview Abstract] |
Tuesday, October 30, 2012 10:42AM - 10:54AM |
GO5.00007: Effect of Laser Pulse Length on Fast Electron Generation and Transport M.S. Wei, J. Jaquez, R.B. Stephens, A. Sorokovikova, R. Mishra, L.C. Jarrott, H. Sawada, F.N. Beg, W. Theobald, C. Mileham, H. Chen, P. Patel, H. McLean, Y. Sentoku Experiments have been performed to determine the pulse length effects on fast electron generation using the OMEGA EP laser with multilayer foil targets consisting of an Al substrate with a Cu tracer layer buried $\sim$100$\,\mu$m beneath. Pulse lengths of 0.7, 3 and 10 ps were used with a constant intensity of $I_{peak}\sim 10^{19}\,$W/cm$^2$. Fast electrons were measured via Cu K-shell and bremsstrahlung radiation. We observed electron beams evolving from a single beam in sub-ps interaction into multiple widely spread filaments ($\sim$100$\,\mu$m between each filament) in the 10 ps case. Electron beam size decreased with increasing pulse length suggesting collimation by strong resistive B-fields that grow with time inside the solid target. Bremsstrahlung data suggesting an increase in electron temperature and conversion efficiency in the 10 ps case, was possibly due to presence of a longer preplasma. Experiments are being modeled with 2D collisional PIC simulations and results will be discussed. [Preview Abstract] |
Tuesday, October 30, 2012 10:54AM - 11:06AM |
GO5.00008: Electron transport and instabilities in laser plasma interaction Bhuvanesh Ramakrishna, Kevin Quinn, Lorenzo Romagnani, Gianluca Sarri, Puthenparampil Wilson, Marco Borghesi, Oswald Willi, Julien Fuchs, Livia Lancia, Thomas Cowan The propagation of laser-driven, relativistic electron beams in plasmas is a phenomenon of relevance in astrophysical scenarios, particularly concerning the problem of the generation of strong, spatially extended and sustained magnetic fields in astrophysical jets. We report on experiments where the transport of hot electron currents through foam has been studied using the proton imaging technique. Strong filamentation has been observed, possibly due to electromagnetic instabilities of the Weibel type. A multitude of tubelike filamentary structures is also observed to form behind the front of a plasma created by irradiating solid-density wire targets with a high-intensity ($I\sim $10$^{19}$ W/cm$^{2})$, picosecond-duration laser pulse. These filaments exhibit a remarkable degree of stability, persisting for several tens of picoseconds, and appear to be magnetized over a length corresponding to several filament radii. [Preview Abstract] |
Tuesday, October 30, 2012 11:06AM - 11:18AM |
GO5.00009: Fast electron beam divergence in foil targets with embedded high-Z gold layers irradiated with ultraintense 527nm laser pulses Shaun Kerr, Anthony Link, Christopher McGuffey, Gregory Kemp, Douglas Wertepny, Mianzhen Mo, Zhijiang Chen, Henry Tiedje, Ying Tsui, Robert Fedosejevs, Jonathan Peebles, Farhat Beg, Richard Freeman, Harry McLean, Prav Patel, Yuan Ping, Hirotaka Nakamura, Mingsheng Wei, Richard Stephens, Rafael Ramis, Javier Honrubia We report on experimental measurements of fast electron beam divergence in planar Al targets with buried and surface Au layers, irradiated with second harmonic (2$\omega $, 527-nm) laser light (50 J, 0.7 ps). In particular we study the propagation through the buried high-Z layers, which could deflect the fast electron beams through magnetic fields generated at the layer interfaces. Low prepulse energies, on the order of 10 $\mu $J, enabled electron creation at well-defined surfaces and with cooler energy spectra compared to 1$\omega $; in addition, shots were taken with a controlled 3mJ prepulse to generate a preplasma density profile. K$_{\alpha }$ emission from buried Cu tracer layers was imaged to give electron beam divergence, while electron temperature measurements were made with Bremsstrahlung detectors and electron spectrometers. The results will be presented and compared to PIC and hybrid-PIC simulations. [Preview Abstract] |
Tuesday, October 30, 2012 11:18AM - 11:30AM |
GO5.00010: Angular distribution of fast electrons in intense laser-solid interactions Ross Gray, David Carroll, Xiaohui Yuan, Christopher Murphy, Haydn Powell, David Maclellan, Mark Quinn, Olivier Tresca, Mireille Coury, Graeme Scott, Ceri Brenner, Christopher Brady, Christopher Ridgers, James Green, Nicola Booth, David Neely, Paul McKenna A clear understanding of the generation and transport of fast electrons is critical for applications of laser-solid interactions, such as ion driven cancer therapy or the fast ignition scheme of ICF. In this paper, we report on two experimental campaigns in which the escaping fast electron angular distribution (AD) was measured. In the first, a novel ``wrap-around'' detector is used to measure the electron and proton AD, as well as providing crude spectral information. By varying the laser incidence angle from 10$^{\circ}$ to 80$^{\circ}$. The clear growth of a dominant surface guided component of fast electrons is directly observed. In the second, a novel 360$^{\circ}$, fibre coupled scintillator detector is used to measure the escaping electrons AD. A magnetic spectrometer is used to provide a high resolution spectral measurement of the accelerated protons and electrons. For the first time, the effect of laser intensity, polarisation and target thickness, down to 20 nm, on the observed AD, at ultra-high contrast, is reported. A strongly polarisation dependent transition into a radiation pressure dominant regime is observed. [Preview Abstract] |
Tuesday, October 30, 2012 11:30AM - 11:42AM |
GO5.00011: Deuteron Beam Driven Fast Ignition of a Pre-Compressed Inertial Confinement Fusion (ICF) Fuel Capsule Xiaoling Yang, George Miley, Kirk Flippo, Heinrich Hora, Sandrine Gaillard, Dustin Offermann We proposed to utilize a new ``Deuterium Cluster'' type structure for the laser interaction foil to generate an energetic deuteron beam as the fast igniter to ignite inertial confinement fusion fuel capsule. The benefit of deuteron beam driven fast ignition is that its deposition in the target fuel will not only provide heating but also fuse with fuel as they slow down in the target. The preliminary results from recent laser-deuteron acceleration experiment at LANL were encouraging. Also, in most recent calculations, we found that a 12.73{\%} extra energy gain from deuteron beam-target fusion could be achieved when quasi-Maxwellian deuteron beam was assumed, and when a $\rho $rb = 4.5 g/cm2 was considered, where $\rho $ is the fuel density, and rb is the ion beam focusing radius on the target. These results provide some insight into the contribution of the extra heat produced by deuteron beam-target fusion to the hot spot ignition process. If the physics works as anticipated, this novel type of interaction foil can efficiently generate energetic deuterons during intense laser pulses. The massive yield of deuterons should turn out to be the most efficient way of igniting the DT fuel, making the dream of near-term commercialization of FI fusion more achievable. [Preview Abstract] |
Tuesday, October 30, 2012 11:42AM - 11:54AM |
GO5.00012: Spatial and Temporal Evolution of Megagauss Magnetic Fields in Petawatt Laser-Solid Interactions in the Fast Ignition Regime Gourab Chatterjee, Prashant K. Singh, Amit D. Lad, A.P.L. Robinson, N. Booth, J.S. Green, K.L. Lancaster, P. Koester, L.A. Gizzi, R.J. Gray, R.J. Dance, O. Culfa, John Pasley, N.C. Woolsey, G. Ravindra Kumar, P.P. Rajeev In view of the crucial role played by the relativistic mega-ampere electron currents in mediating the energy transfer to the core of the DT fuel in fast ignition (FI), it is imperative to obtain a direct unambiguous measure of the fast electron transport, laden with the well-known filamentary instabilities. Here, we report the first direct pump-probe Cotton-Mouton polarimetric measurements of the spatial and the temporal evolution of the megagauss magnetic fields, which bear the signature of fast electron transport, generated at the rearside of a petawatt-laser-irradiated solid target in an intensity regime (3 ps pulses at $10^{20}-10^{21}$ W/cm$^2$) of direct relevance to FI. The experiment was performed at the Vulcan Petawatt laser facility. The temporal and the spatial evolution of the megagauss magnetic fields will be presented, emphasizing on the filamented beam transport to the rearside of 50 $\mu$m thick Al targets, as well as a central hollow in the rearside magnetic field profile in 50 $\mu$m thick plastic targets, previously predicted in simulations. [Preview Abstract] |
Tuesday, October 30, 2012 11:54AM - 12:06PM |
GO5.00013: Ray-Trace Simulations for the Optical 4$\omega$ Probe Diagnostic on OMEGA EP S. Ivancic, W. Theobald, D.H. Froula, R. Boni, S.X. Hu Characterization of the density and temperature of long-scale-length plasmas provides important information for inertial confinement fusion applications. This is required to better understand laser--plasma instabilities at approximately quarter-critical density and to study the channeling of a high-intensity, short-pulse laser through large plasmas for fast ignition. A short-pulse (10-ps) UV optical probe operating at $\lambda$ = 263 nm has been developed to diagnose long-scale-length plasmas on OMEGA EP. The diagnostic includes schlieren and shadowgraphy imaging and will provide quantitative measurements of the plasma density. Simulations of the optical diagnostics for the channeling experiments have been performed. A 3-D ray-trace code (\textit{FRED}) was used to simulate the optical system and take the refraction and diffraction of the probe light into account when propagating through plasma. Simulations show that the diagnostics are capable of measuring the density profile over several mm field of view and resolving a channel over a range of tens of $\mu$m diameter. Implications on spatial resolution and peak density measurements with the diagnostics are considered. 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] |
Tuesday, October 30, 2012 12:06PM - 12:18PM |
GO5.00014: On scaling laws for ignition at NIF Baolian Cheng, Thomas Kwan, Yi-Ming Wang, Steven Batha The Ignition Threshold Factor (ITF) [1] was developed to guide the ignition campaign at the National Ignition Facility (NIF). In this work, we derive from first-principle the minimum energy required for implosion of a capsule to achieve ignition. We obtain a general expression relating the ITF to the capsule implosion velocity. With a particular choice of the equation of states (EOS) for the fuel, we recover the eighth power dependence. However, the sensitivity of the dependence is found to be different for different choices of EOS. We will present the general results and its significance in achieving ignition at NIF. \\[4pt] [1] S. W. Haan, et. al, Phys. Plasmas 18, 051001 (2011) and references therein. [Preview Abstract] |
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