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 PO5: High-intensity Short-pulse Laser Plasma Interactions |
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Chair: Christina Back, General Atomics Room: Hanover CDE |
Wednesday, November 4, 2009 2:00PM - 2:12PM |
PO5.00001: Initial Results from the OMEGA EP Laser System D.D. Meyerhofer, R. Betti, T.R. Boehly, J.H. Kelly, S.J. Loucks, R.L. McCrory, S.F.B. Morse, P.M. Nilson, S.P. Regan, T.C. Sangster, V.A. Smalyuk, C. Stoeckl, W. Theobald, L.J. Waxer The OMEGA EP Laser, with four NIF-like beams, was completed in April 2008. The beams can be operated at 351~nm, with each ultimately producing 6.5 kJ in a 10-ns pulse into the OMEGA EP target chamber. Two of the beams can be operated as high-energy petawatt lasers (HEPW), each producing up to 2.6 kJ in a 1053 nm, 10-ps pulse. The HEPW beams can be directed into the OMEGA EP target chamber or into the 60-beam OMEGA target chamber for experiments that combine target compression with HEPW capability. Initial experiments include measurements of the duration-dependent HEPW laser-to-fast-electron conversion efficiency, isochoric heating of small-mass targets, radiography of imploding targets, integrated fast ignition, materials physics, and the development of $>$10-keV backlighting sources. These results show the effectiveness of OMEGA EP for high-energy-density physics experiments. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Wednesday, November 4, 2009 2:12PM - 2:24PM |
PO5.00002: Hot-Electron Generation with Kilojoule Pulses on OMEGA EP P.M. Nilson, J.F. Myatt, C. Stoeckl, P.A. Jaanimagi, W. Theobald, J.A. Delettrez, J.D. Zuegel, R. Betti, D.D. Meyerhofer, T.C. Sangster, K.U. Akli, P.K. Patel, A.J. Mackinnon Intense laser--solid interactions generate high-current electron sources with relativistic energies that are important for advanced ignition experiments. Applications include rapid heating for fast ignition and energy deposition in solid material for flash radiography, isochoric heating, and x-ray scattering experiments. Results of laser-electron coupling experiments carried out on the OMEGA EP laser with up to 1.3-kJ, 10-ps-long pulses will be presented. Strong ($\sim $20{\%}) energy coupling to electrons is demonstrated with conversion efficiencies \textit{independent} of the laser pulse duration. This work was supported by the U.S. D.O.E Office of Inertial Confinement Fusion under Cooperative Agreement Nos. DE-FC02-ER54789 and DE-FC52-08NA28302. (P.M. Nilson, R. Betti, and D.D. Meyerhofer also FSC.) [Preview Abstract] |
Wednesday, November 4, 2009 2:24PM - 2:36PM |
PO5.00003: Temperature measurement of short-pulse heated beryllium using non-collective x-ray Thomson scattering with a Zn K-$\alpha $ line source T. Doeppner, A.L. Kritcher, O.L. Landen, H.J. Lee, S.T. Le Pape, C. Stoeckl, W. Theobald, S.H. Glenzer Experiments are fielded on the OmegaEP laser facility at the Laboratory of Laser Energetics in Rochester that use the unique capability of sending two kJ-class short pulse beams on target. One of the beams is used to generate hot electrons that isochorically heat a 250 $\mu $m Be cube to T$_{e}$ = 20-100 eV at n$_{e}\sim $3 x 10$^{23}$ cm$^{-3}$. The second beam creates Zn K-$\alpha $ x-rays at 8.6 keV to measure Thomson scattering in the non-collective regime with time resolution of $\sim $10 ps. T$_{e}$ can be inferred from Doppler-broadening of the Compton feature that is energy down-shifted from the Rayleigh signal. Future experiments will aim at measuring collective scattering from plasmon oscillations. The collisionality can be inferred from broadening of the plasmon signal, allowing measurement of the conductivity at conditions encountered during capsule implosions at the National Ignition Facility. [Preview Abstract] |
Wednesday, November 4, 2009 2:36PM - 2:48PM |
PO5.00004: Transport of MA electron currents in ultra-fast heated conducting solids Yasuhiko Sentoku, Julien Fuchs, Emmanuel d'Humieres Transport of MA currents in conducting high Z solids is crucial for number of applications, e.g. the generation of efficient and fast secondary sources (ions, X-rays, g-rays, etc) or cone-guiding fast ignition of inertial fusion. We have simulated the ultra-intense ultra-short laser - solid target interaction with a particle-in-cell code, PICLS, which features the relativistic Coulomb collisions, dynamics ionization in gas and solid target, and have studied the MA current transport by irradiating an ultra-intense laser pulse ($5\times 10^{19}$W/cm$^2$, 300fs) in different conducting metal target, such as aluminum, copper, and gold. We found that the strong resistive magnetic fields are excited inside solid, and the fields become stronger in higher Z target because of $\nabla Z$ induced by dynamics ionization. The transport of hot electron currents are affected by these magnetic fields, $\sim$10 MG in a Al target, and $>$ 50MG in Cu or Au targets. The sheath field at target rear is also modulated because of the transport pattern. Simulations results are consistent with MeV proton beam images observed in experiments. [Preview Abstract] |
Wednesday, November 4, 2009 2:48PM - 3:00PM |
PO5.00005: Energy transport and isochoric heating of ultra-fast heated low-Z targets Rohini Mishra, Yasuhiko Sentoku, Peter Hakel, Roberto Mancini Ultra-short intense laser pulse generates hot electrons on a target surface. Energy transport and isochoric heating of solid target are important for number of applications, e.g. the generation of secondary sources (ions, X-rays, etc) or the fast ignition of inertial fusion targets. We have performed a particle-in-cell, PICLS, which incorporates the relativistic Coulomb collisions and dynamic ionization in gas and solid targets in order to study the MA current transport and isochoric heating in low Z insulator targets. Our target is a triple layered plastic target (C$_{2}$H$_{2}$/C$_{2}$H$_{3}$Cl/C$_{2}$H$_{2}$, 5$\mu$m-thick for each layer), inspired by the experiments by Ohshima, Nishimura et al., ILE, Osaka. In the experiment, the 2$^{nd}$ layer is heated up to 50 eV by irradiating a 0.5 PW laser pulse with 250 J in 500fs. We studied the isochoric heating processes in the triple-layered target, and identified three different heating processes, namely, resistive, collisional and diffusive heating, which compete in their different time frames. Re-circulating hot electrons ionize the target, and change the resistivity dynamically. Effects of hot electron recirculation, dynamic ionization, and the resistive magnetic fields are also discussed in this talk. [Preview Abstract] |
Wednesday, November 4, 2009 3:00PM - 3:12PM |
PO5.00006: Hydrodynamic Simulations and Optical Diagnosis of a Long-Scale-Length Channeling Experiment on OMEGA EP R.S. Craxton, W. Theoald, W. Seka, S. Ivancic, G. Li, C. Ren, D. Weiner An experiment is planned for OMEGA EP to investigate the channeling concept proposed for fast ignition. A long-scale-length plasma is first produced using long-pulse OMEGA EP beams and then irradiated with a tightly focused, high-intensity, short-pulse ($\sim $100 ps) ``channeling'' beam. An optical probe will be employed to characterize the long-scale-length plasma using the grid image refractometry\footnote{ R. S. Craxton \textit{et al.}, Phys. Fluids B \textbf{5}, 4419 (1993).} technique and the channel formed in the underdense plasma using schlieren imaging. Two-dimensional hydrodynamic simulations using \textit{SAGE} will be presented, together with ray-tracing simulations of the optical diagnostics using \textit{SAGE} profiles adjusted to include the channel predicted by particle-in-cell 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] |
Wednesday, November 4, 2009 3:12PM - 3:24PM |
PO5.00007: Self- Focusing and Channeling of Relativistic Laser Pulses in Underdense Plasmas Neda Naseri, Wojciech Rozmus We studied in details the ponderomotive channeling of the intense laser pulse in underdense homogeneous plasma using 3D PIC simulations, considering different laser powers and plasma densities. We found limits on plasma density in order to get fully evacuated channels. Also the effects of surface wakes on destruction of electron evacuated channels have been addressed. Evacuation can be lost due to surface wave excitation on the channel edges. The wavelength of the surface waves has been calculated in cylindrical geometry for arbitrary laser intensity on the channel edges. The rise time of the laser pulse plays an important role on the stability of the channels. We also found that the dominant mechanisms in higher densities is hosing and filamentation of the laser pulse. Formation of ring structure, central electron density enclosed by a hollow ring, has been observed in 3D simulations. We have also found that analytical multi-channel solutions are unstable due to the interaction between filaments. The simulation results are in a very good agreement with existing analytical results.\\[4pt] [1] Kim et al. Phys. Rev E, 65,036416 (2002) [Preview Abstract] |
Wednesday, November 4, 2009 3:24PM - 3:36PM |
PO5.00008: Millimeter-scale laser channeling in underdense argon plasma diagnosed with K$\alpha $ x-ray imaging* N.L. Kugland, C.G. Constantin, T. Doeppner, A. Kemp, L. Divol, S.H. Glenzer, C. Niemann Two-dimensional x-ray imaging of K$\alpha $ self-emission from laser-irradiated Ar gas jets has been used to study laser channeling and fast electron transport over millimeter-scale distances. We irradiated high density (10$^{20}$ cm$^{-3}$ atomic density) supersonic Ar gas jets with an ultra-high intensity (10$^{19}$ W/cm$^{2})$, high power (100 TW class) 800 nm laser. K$\alpha $ fluorescence reveals a millimeter-scale laser channel, oriented along the laser axis, which ends in a forward-directed spray of fast electrons. K-shell x-ray spectroscopy diagnoses a spatially averaged mean ionization state of 6 $\pm $ 1 during the K$\alpha $ emission, implying an electron density of 0.5 n$_{c}$. Study of this system can help understand the initial stage of the hole-boring approach to fast ignition, during which an intense laser pulse must propagate through a mm-scale moderately underdense plasma. *This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Additional support was provided by LDRD grant 08-LW-004 and the DOE Plasma Physics Junior Faculty Award Program. [Preview Abstract] |
Wednesday, November 4, 2009 3:36PM - 3:48PM |
PO5.00009: LSP Modeling of Reflection and Absorption of an Intense Laser Pulse from a Solid Target Douglass Schumacher, Anthony Link, Vladimir Ovchinnikov, Richard Freeman, Linn Van Woerkom, Mingsheng Wei, Farhat Beg, Michael Key, Andrew Mackinnon, Pravesh Patel, Lujbomir Nikolic, Ying Tsui, Robert Fedosejevs We describe the results of LSP modeling of laser reflection from solid-density gold slabs surrounded by lower density plasma (scale length of order 10 $\mu $m). We treat p-polarized light at various incident angles, intensities up to 10$^{19~}$W/cm$^{2}$ and various pulse widths. We examine absorbed, specularly reflected, and scattered light, and near and far field spatial and spectral modification of the beam. We find large, regular variation of reflectivity and scatter with all parameters, increased divergence and red chirp in the reflected beam, and other effects. We compare to recent experiment. [Preview Abstract] |
Wednesday, November 4, 2009 3:48PM - 4:00PM |
PO5.00010: Efficient Generation of High-Quality Proton Beam in Laser Tailored-Target Interaction S. Kawata, K. Takahashi, D. Satoh, D. Barada, Y.Y. Ma, Z.M. Sheng, O. Klimo, J. Limpouch, Q. Kong, P.X. Wang Improvement of energy conversion efficiency from laser to proton beam is demonstrated in a laser-foil interaction. When an intense short-pulse laser illuminates the thin foil target, the foil electrons are accelerated around the target. The hot electrons generate a strong electric field, which accelerates the foil protons, and the proton beam is generated. In this paper a multihole thin-foil target is proposed in order to increase the energy conversion efficiency from laser to protons. The multiholes transpiercing the foil target help to enhance the laser-proton energy conversion efficiency significantly. 2.5-dimensional particle-in-cell simulations present that the total laser-proton energy conversion efficiency becomes 9.3{\%} for the multihole target, though the energy conversion efficiency is 1.5{\%} for a plain thin foil target. The transpiercing multihole target serves a new method to increase the energy conversion efficiency from laser to ions. \\[4pt] [1]~R. Sonobe, et al., Phys. Plasmas, 12 (2005) 073104. \\[0pt] [2] Y. Nodera, et al., Phys. Rev. E78 (2008) 046401. [Preview Abstract] |
Wednesday, November 4, 2009 4:00PM - 4:12PM |
PO5.00011: Radiation Pressure Acceleration of Ions A.P.L. Robinson The possibility of accelerating ions by ultraintense lasers in a regime where the radiation pressure of the laser pulse dominates the interaction has received considerable interest in recent years. Simple analytical models show that this regime of acceleration should be highly tunable and permit scaling to hundreds of MeV for laser intensities in excess of 10$^{21}$ Wcm$^{-2}$. The use of circularly polarized laser pulses has been very important in these theoretical studies. In this presentation we will describe a simple analytical model for RPA and compare this to numerical simulations. The outstanding question of transverse instabilities will also be discussed, as well as the possibility of the RPA mechanism occurring in underdense plasmas. [Preview Abstract] |
Wednesday, November 4, 2009 4:12PM - 4:24PM |
PO5.00012: The Effect of Hemispherical Target Diameter on Proton Focusing T. Bartal, D.P. Higginson, M.S. Wei, F.N. Beg, D. Hey, S. Le Pape, M.H. Key, P.K. Patel, A.J. Mackinnon, H.S. McLean, S.A. Gaillard, K. Flippo, D.T. Offermann, R.P. Johnson, D.S. Montgomery, T. Shimada, R. Gonzales, S. Reid, F. Archuleta, S. Letzring, T. Hurry, R.B. Stephens Proton focusing from hemispherical targets, to be used in the concept of proton fast ignition, was investigated using the 200TW Trident laser at LANL delivering 80J in 0.5ps with 45{\%} of the energy focused to 7 microns fwhm. High-density carbon hemispherical segments, 0.35-2mm in diameter with 10 miron thick walls, were irradiated at normal incidence. On the rear side of the target, two Cu meshes were placed 1mm and 1.5mm from the opening of the hemispherical segment, one angled with respect to the other. Radiochromic film (RCF) was used to image the proton beam, which carried an imprint of each mesh. The mesh images were used to reconstruct the proton beam and determine the focal plane using a ray tracing technique. Experimental results will be discussed. *Performed for U.S. DOE under contracts FI-ACE, DE-FG-02-05ER54834, DE-AC52-07NA27344. [Preview Abstract] |
Wednesday, November 4, 2009 4:24PM - 4:36PM |
PO5.00013: Simulations of relativistic positron creation using ultra-intense, short pulse lasers S.C. Wilks, H. Chen, C.D. Chen, S.N. Chen, J. Gronberg, J. Myatt, D.D. Meyerhofer, G. Gregori, C.D. Murphy, J. Mithen, D. Welch The recent generation of positrons using ultra-intense lasers will be discussed in detail [1]. Although good agreement between theory and experiment for the number of positrons created is obtained [2], the positron peak appears to be shifted in energy by several MeV, depending on the number of electrons that are heated by the laser. We attribute this shift to the TNSA mechanism [3], and will present simulation results consistent with this hypothesis. Indications are that even with targets a few millimeters thick, the electric field on the rear of the target can be $\sim$10 MeV/micron. Particle-in-cell and Monte Carlo simulations of the process have been performed in an attempt to maximize the positron production, and these results will be presented. \\[4pt] [1] H. Chen, \textit{et al}., PRL \textbf{102}, 105001 (2009). \\[0pt] [2] J. Myatt,\textit{ et al}., PRE \textbf{79}, 066409 (2009). \\[0pt] [3] S.C. Wilks, \textit{et. al.,} Phys. Plasmas \textbf{8}, 542 (2001). [Preview Abstract] |
Wednesday, November 4, 2009 4:36PM - 4:48PM |
PO5.00014: Using x-ray-free-electron lasers to generate and probe high-energy-density matter Stefan Hau-Riege, Richard London, Siegfried Glenzer, Jon Weisheit, Jim Glosli, Dave Richards, Frank Graziani Recently, lasing has been achieved at the LCLS x-ray free electron laser. Sub-200 fs pulses with a wavelength of 0.15 nm and a pulse energy of 2 mJ have been produced. We have designed an experiment, which utilizes this laser to study ultrafast processes in warm- and hot-dense matter, including ionization, energy transfer, and initial atomic motion. We use the unique high peak-brightness radiation to heat solids isochorically to temperatures up to 100 electron volts, corresponding to pressures up to 20 Mbar. The x-ray free electron laser pulses will also serve as a probe of the state of the material via by Bragg and x-ray Thomson scattering. Elastic Bragg scattering provides ionic properties and structural information about the crystal, while the inelastic Compton and plasmon scattering spectrum reflects the electrical/optical properties, and further provides temperature and density information. We used a new modeling methodology that includes the relevant ionization processes in a massively-parallel molecular dynamics code to simulate the full experiment, including the generation of the high-energy-density material and the formation of the probe-signals. [Preview Abstract] |
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