Bulletin of the American Physical Society
56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014; New Orleans, Louisiana
Session GO6: Shock and Fast Ignition |
Hide Abstracts |
Chair: Matthias Hohenberger, University of Rochester Room: Galerie 3 |
Tuesday, October 28, 2014 9:30AM - 9:42AM |
GO6.00001: An Implosion-Velocity Survey for Shock Ignition at the National Ignition Facility K.S. Anderson, P.W. McKenty, T.J.B. Collins, J.A. Marozas, M. Lafon, R. Betti Shock ignition (SI) is a low-energy, high-gain alternative path to ignition at the National Ignition Facility (NIF). In SI, a high-intensity laser spike added at the end of the compression pulse launches a strong shock into the precompressed capsule, raising the hot-spot pressure and temperature. This spike pulse allows SI targets to achieve ignition temperatures at lower shell velocities than standard hot-spot implosions. Optimizing the ignition margin in SI implosions requires finding an implosion velocity that balances 1-D target performance with multidimensional stability characteristics. Polar-drive SI designs for the NIF at 700 kJ will be reviewed and compared for stability and margin in 1-D and 2-D simulations at implosion velocities varying from 260 to 300 km/s. Stability studies will include both polar-drive beam geometry and beam repointing as well as laser-imprinted nonuniformities from laser speckle. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786. [Preview Abstract] |
Tuesday, October 28, 2014 9:42AM - 9:54AM |
GO6.00002: Shock Ignition Theoretical Studies: From Hot Electrons Pressure Generation To Converging Amplification Effects Xavier Ribeyre, Emma Llor, Alexandra Vallet, Philippe Nicolai, Vladimir Tikhonchuk The shock ignition (SI) concept in inertial confinement fusion uses an intense power spike at the end of an assembly laser pulse. The power spike launches a strong shock wave with an ablation pressure of $\sim$ 0.3 Gbar that increases in strength when converging through the imploding shell. However, the detail understanding of the role hot electrons in the pressure generation and the converging shell effects on pressure amplification is crucial in SI. First, we present a model describing the effect of the fast electron energy distribution on the dynamics of shock wave formation and the compression of matter behind its front. We have studied analytically and numerically the penetration and the energy deposition of fast electrons in a dense plasma and the shock wave formation. A criterion of a strong shock formation with an electron beam is obtained for an arbitrary distribution function. Finally, we present a new semi-analytical hydrodynamic model to describe the shock from its generation until fuel ignition. The shock pressure amplification follows mainly the overall imploded shell pressure enhancement but is not sufficient for SI. The shock is further amplified when it collides inside the shell with diverging shocks coming from the assembly phase. The shock is partially transmitted to the hot spot when it crosses the shell/fuel interface depending on the shock timing. A semi-analytical criterion for ignition on the shock pressure is expressed. [Preview Abstract] |
Tuesday, October 28, 2014 9:54AM - 10:06AM |
GO6.00003: Assessing target design robustness for Shock Ignition using 3D laser raytracing Angelo Schiavi, Stefano Atzeni, Alberto Marocchino Shock ignition (SI)[1] is a laser direct-drive Inertial Confinement Fusion scheme in which fuel compression and hot spot formation are separated. Shock ignition shows potential for high gain at laser energy below 1 MJ (see review Ref.[2]), and could be tested on present large scale facilities. We produced an analytical model for SI which allows rescaling of target and laser drive parameters starting from a given point design [3]. The goal is to redefine a laser-target configuration increasing the robustness while preserving its performance. We developed a metric for ignition margins specific to SI [4]. We report on simulations of rescaled targets using 2D hydrodynamic fluid model with 3D laser raytracing. The robustness with respect to target fabrication parameters and laser facility fluctuations will be assessed for an original reference design as well as for a rescaled target, testing the accuracy of the ignition margin predictor just developed. Work supported by the Italian MIUR project PRIN2012AY5LEL. \\[4pt] [1] R. Betti, C.D. Zhou et al, PRL 98, 155001 (2007)\\[0pt] [2] S. Atzeni, X. Ribeyre et al, Nucl. Fusion 14, 054008 (2014)\\[0pt] [3] S. Atzeni, A. Marocchino, A. Schiavi and G. Schurtz, New J. Phys. 15, 045004 (2013)\\[0pt] [4] S. Atzeni, A. Marocchino, A. Schiavi, EPS Conf. proc. submitted to PPCF (2014) [Preview Abstract] |
Tuesday, October 28, 2014 10:06AM - 10:18AM |
GO6.00004: Combined effects of laser and non-thermal electron beams on hydrodynamics and shock formation in the Shock Ignition scheme Ph. Nicolai, J.L. Feugeas, M. Touati, J. Breil, B. Dubroca, T. Nguyen-Buy, X. Ribeyre, V. Tikhonchuk, S. Gus'kov An issue to be addressed in Inertial Confinement Fusion (ICF) is the detailed description of the kinetic transport of relativistic or non-thermal electrons generated by laser within the time and space scales of the imploded target hydrodynamics. We have developed at CELIA the model M1 [1], a fast and reduced kinetic model for relativistic electron transport. The latter has been implemented into the 2D radiation hydrodynamic code CHIC [2]. In the framework of the Shock Ignition (SI) scheme, it has been shown in simplified conditions that the energy transferred by the non-thermal electrons from the corona to the compressed shell of an ICF target could be an important mechanism for the creation of ablation pressure [3]. Nevertheless, in realistic configurations, taking the density profile and the electron energy spectrum into account, the target has to be carefully designed to avoid deleterious effects on compression efficiency [4]. In addition, the electron energy deposition may modify the laser-driven shock formation and its propagation through the target. The non-thermal electron effects on the shock propagation will be analyzed in a realistic configuration. \\[4pt] [1] B. Dubroca \textit{et al.}, Eur. Phys. J. D 60, 301 (2010), [2] J. Breil \textit{et al.}, J. Comp. Phys. 224, 785 (2007), [3] S. Gus'kov et al., Phys. Rev. Letters 109, 255004 (2012), [4] Ph. Nicola\"{\i} et al, Phys. Rev. E 89, 033107 (2014). [Preview Abstract] |
Tuesday, October 28, 2014 10:18AM - 10:30AM |
GO6.00005: Spherical Strong-Shock Inferences on OMEGA R. Nora, M. Lafon, R. Betti, W. Theobald, W. Seka, J.A. Delettrez A milestone for shock ignition\footnote{ R. Betti \textit{et al}., Phys. Rev. Lett. \textbf{98} 155001 (2007).} is to experimentally verify the generation of several hundred Mbar shocks at shock-ignition--relevant laser intensities. This paper presents the first experimental evidence of strong shocks generated in a spherical geometry. Using the temporal delay between the launch of the strong shock at the outer surface of the spherical target and the time when the shock converges at the center, the shock properties can be inferred using radiation--hydrodynamic simulations. Peak ablation pressures exceeding 200 Mbar are inferred at laser intensities of $\sim 3 \times 10^{15}$ W/cm$^2$. The shock strength is significantly enhanced by the coupling of copius amounts of hot electrons, up to 2 kJ with $T_{\mbox{hot}} \sim$ 50 to 100 keV. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786. [Preview Abstract] |
Tuesday, October 28, 2014 10:30AM - 10:42AM |
GO6.00006: Effects of Preplasma in 10-ps Relativistic Laser Matter Interaction M.S. Wei, R.B. Stephens, J. Peebles, C. McGuffey, B. Qiao, F. Beg, Y. Sentoku, A. Link, H. Chen, H. McLean, W. Theobald, D. Haberberger, A. Davies Experiments were performed using the kJ 10-ps OMEGA EP laser to study the effect of preplasma on fast electron generation and energy coupling in relativistic laser plasma interaction (LPI) with a controlled preplasma at various scalelength created by a 1-ns UV laser. Targets were multilayered planar foil consisting of an Al substrate, a buried Cu layer and a thick conductive CH layer. Preplasma density profile and relativistic LPI generated fields were characterized using a 10-ps 4$\omega$ optical probe (angular filter refractometry and polarimetry) together with radiography using a high-energy proton beam produced by the second kJ 10-ps EP beam. Fast electrons were diagnosed by measuring Cu K-shell fluorescence emission and bremsstrahlung radiation. Electron energy spectrum was monitored by a magnetic spectrometer. Preliminary results showed nonlinear interaction instabilities and a reduced electron temperature with increasing preplasma scalelength. Dynamics of the relativistic LPI and the resultant fast electron beam characteristics and energy coupling will be presented. [Preview Abstract] |
Tuesday, October 28, 2014 10:42AM - 10:54AM |
GO6.00007: Impact of Pre-Plasma on Fast Electron Generation and Transport from Short Pulse High Intensity Lasers J. Peebles, C. McGuffey, C. Krauland, L.C. Jarrott, A. Sorokovikova, B. Qiao, S. Krasheninnikov, F.N. Beg, M.S. Wei, J. Park, A. Link, H. Chen, H.S. McLean, C. Wagner, V. Minello, E. McCary, A. Meadows, M. Spinks, E. Gaul, G. Dyer, B.M. Hegelich, M. Martinez, M. Donovan, T. Ditmire We present the results and analysis from recent short pulse laser matter experiments using the Texas Petawatt Laser to study the impact of pre-plasma on fast electron generation and transport. The experimental setup consisted of 3 separate beam elements: a main, high intensity, short pulse beam for the interaction, a secondary pulse of equal intensity interacting with a separate thin foil target to generate protons for side-on proton imaging and a third, low intensity, wider beam to generate a varied scale length pre-plasma. The main target consisted of a multilayer planar Al foil with a buried Cu fluor layer. The electron beam was characterized with multiple diagnostics, including several bremsstrahlung spectrometers, magnetic electron spectrometers and Cu-K$\alpha $ imaging. The protons from the secondary target were used to image the fields on the front of the target in the region of laser plasma interaction. Features seen in the interaction region by these protons will be presented along with characteristics of the generated electron beam. This work performed under the auspices of the US DOE under contracts DE-FOA-0000583 (FES, NNSA). [Preview Abstract] |
Tuesday, October 28, 2014 10:54AM - 11:06AM |
GO6.00008: Irradiation of intense laser on the inner surface of CD shell to generate the hot spark in the fast ignition Atsushi Sunahara, Takahiro Nagai, Yuki Abe, Seung Ho Lee, Yasunobu Arikawa, Shinsuke Fujioka, Tomoyuki Tohzaki, Kunioki Mima, Hiroyuki Shiraga, Hiroshi Azechi We propose the new heating scheme of the fast ignition. In this scheme, the inner surface of CD shell is irradiated by the relatively longer 100ps pulse with the intensity ranging from $10^{16} W/cm^2$ to $10^{17} W/cm^2$. In this laser intensity region, the laser absorption fraction is relatively low and most of the laser light reflects many times, and heats of the inner surface of the shell. Also, fast electrons with moderate energy ranging from 50keV to 100keV are generated and contribute the shell heating. Then, the heated shell expands toward the center of the target and generates the high temperature hot spark. In order to confirm this concept, we conducted the preliminary experiment by using 1.06 micron wavelength and 100ps duration beams of GXII laser system. We observed that high temperature region was formed at the center of the shell. We will show the concept and its possibility as a alternative method of spark formation in the inertial confiment fusion. [Preview Abstract] |
Tuesday, October 28, 2014 11:06AM - 11:18AM |
GO6.00009: Computational Study of Hydrodynamic Instability under the Strong Magnetic Field Hideo Nagatomo, Takashi Asahina, Atsushi Sunahara, Tomoyuki Johzaki Recent studies suggest that the magnetic field can improve the heating efficiency of Fast Ignition scheme, if high energy electrons are guided toward the compressed core plasma. However, the imposed magnetic field of which intensity is sub-Tesla may affect to the electron thermal conductivity. Our preliminary simulation result suggests that the hydrodynamic instability is seeded by the strong magnetic field. In order to investigate the mechanism of the seed of the hydrodynamic instability in early stage of laser driven acceleration, 2-D magnetic field transport which is coupled with radiation hydrodynamic is executed. The result shows the formation of the ablation surface is suffered by the magnetic field before the acceleration. In this presentation the result of the simulation and mechanism of the seed of the instability are shown in detail. [Preview Abstract] |
Tuesday, October 28, 2014 11:18AM - 11:30AM |
GO6.00010: Laser Channeling in an Inhomogeneous Plasma for Fast-Ignition Laser Fusion S. Ivancic, D. Haberberger, W. Theobald, K.S. Anderson, D.H. Froula, D.D. Meyerhofer, K. Tanaka, H. Habara, T. Iwawaki The evacuation of a plasma cavity by a high-intensity laser beam is of practical importance to the channeling fast-ignition concept. The channel in the plasma corona of an imploded inertial confinement fusion capsule provides a clear path through the plasma so that the energy from a second high-intensity laser can be deposited close to the dense core of the assembled fuel to achieve ignition. This study reports on experiments that demonstrate the transport of high-intensity ($>$ 10$^{17}$ W/cm$^2$) laser light through an inhomogeneous kilojoule-laser--produced plasma up to overcritical density. The multikilojoule high-intensity light evacuates a cavity inside the focal spot, leaving a parabolic trough that is observed using a novel optical probing technique---angular filter refractometery.\footnote{ D. Haberberger \textit{et al.}, Phys. Plasmas \textbf{21}, 056304 (2014).} The cavity forms in less than 100 ps using a 20-TW laser pulse and bores at a velocity of $\sim$ 2 $\mu$m/ps. The experimentally measured depths of the cavity are consistent with a ponderomotive hole-boring model. The experiments show that 100-ps IR pulses with an intensity of $\sim 5\times 10^{17}$ W/cm$^{2}$ produced a channel up to the critical density, while 10-ps pulses with the same energy but higher intensity did not propagate as far. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. [Preview Abstract] |
Tuesday, October 28, 2014 11:30AM - 11:42AM |
GO6.00011: Auxiliary Heating of Inertial Confinement Fusion Targets Peter Norreys The role of collisionless ion heating arising from the propagation of petawatt-laser driven relativistic electron beams in dense plasma will be discussed. The energy cascade mechanism begins first with the rapid growth of electrostatic waves near the electron plasma frequency. These waves reach high amplitudes and break, which then results in the generation of a strongly driven turbulent Langmuir spectrum. Parametric decay of these waves, particularly via the modulational instability, then gives rise to a coupled turbulent ion acoustic spectrum. These waves, in turn, experience significant Landau damping, resulting in the rapid heating of the background ion population. In this talk, I will review the evidence for this cascade process in laboratory plasmas and describe the theoretical background that underpins this process. I will then present the most recent analytic modelling, particle-in-cell and Vlasov-Poisson simulation results of my team within Oxford Physics and the Central Laser Facility that explores the optimum parameter space for this process, focusing in particular on the requirements for auxiliary heating of the central hot spot in inertial confinement fusion target experiments now underway on the National Ignition Facility. I will also describe new methods for hole-boring through the coronal plasma surrounding the fuel using strongly relativistic laser beams that demonstrates the strong suppression of the hosing instability under these conditions. [Preview Abstract] |
Tuesday, October 28, 2014 11:42AM - 11:54AM |
GO6.00012: Auxiliary Heating with Fast Electrons Naren Ratan, Raoul Trines, Nathan Sircombe, Robert Bingham, Peter Norreys Indirect drive inertial confinement fusion experiments can now achieve hot spot temperatures and densities tantalizingly close to ignition conditions. We are investigating the use of a fast electron beam to provide auxiliary heating to tip an existing scheme over the edge to ignition. Experiments on the stopping of fast electron beams have demonstrated that fast electrons are stopped in a much shorter distance than can be accounted for by collisions. Beam-plasma instabilities, a collective phenomenon, are a good candidate for explaining this anomalous stopping. Simulations of electron beams in plasmas have shown heating of the ions in the plasma. A possible explanation for these observations is that a beam-plasma instability produces Langmuir waves which decay to produce ion-acoustic waves, and that these ion-acoustic waves are subsequently damped leading to ion heating. We are studying the possibility of using such a mechanism to provide auxiliary heating of the hot spot using fast electron beams. We will present analytical work and simulations of each stage of this heating mechanism: the beam-plasma system becoming unstable, the decay of the resulting Langmuir waves, and the damping of the ion waves produced. [Preview Abstract] |
Tuesday, October 28, 2014 11:54AM - 12:06PM |
GO6.00013: A novel laser plasma interaction geometry to generate a convergent fast-electron beam Robbie Scott A simple, novel, geometry for the laser-plasma interaction is presented that generates a convergent fast-electron beam. The fast-electron beam focuses within the target, with the focal length determined by the interaction geometry. As the fast electron beam's intensity peaks within the target (i.e. within the Deuterium-Tritium fuel region), this scheme may offer a route to achieving fast-ignition with reduced laser energy. Particle-in-cell simulations are used to demonstrate the potential efficacy of this scheme. [Preview Abstract] |
Tuesday, October 28, 2014 12:06PM - 12:18PM |
GO6.00014: Implosion of indirect-drive fast ignition targets with CH coated reentrant cone Weimin Zhou, Lianqiang Shan, Yuqiu Gu, Baohan Zhang Compared with central ignition of laser fusion, fast ignition separates compression and ignition thus it can relax the requirements on the implosion symmetry and the driven energy. The implosion of indirect-drive fast ignition targets with CH coated reentrant cone was experimentally researched on SHENGUANG (SG) II laser facility. The small scale cone-in-shell target fast ignition was pre-compressed by the SG II eight 260J/1ns/3$\omega $ laser beams indirectly since beam smoothing was not available currently. The maximum density of the compressed cone-in-shell target 1.37 ns after the lasers' irradiation on the inside wall of hohlraum is about 8.7 g/cm3, and the areal density is close to 8.9 mg/cm2, which are well consistent with the simulation results with two-dimensional radiation hydrodynamic code. To minimize the mixing of the compressed fuel and high-Z vapor produced by the M-line emission from the gold holhraum, a 3$\mu $m CH foil was coated on the full outer surface of the cone and guiding wire. Experimental results and simulation results also demonstrated the coated CH foil could minimize the mixing effectively. By the appropriate design, target can remain robust before the maximum compression, that is, the time while the hot electrons produced by ignition laser pulse deposit energy in the compressed fuel. [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