Bulletin of the American Physical Society
2005 47th Annual Meeting of the Division of Plasma Physics
Monday–Friday, October 24–28, 2005; Denver, Colorado
Session UP1: Poster Session IX |
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Room: Adam's Mark Hotel Grand Ballroom I & II 9:30am |
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UP1.00001: SUPPLEMENTAL |
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UP1.00002: Blobs, momentum transport and tokamak rotation J.R. Myra, D.A. D'Ippolito, D.A. Russell, S.I. Krasheninnikov, B. Coppi This paper examines how instabilities in the vicinity of the separatrix can provide a mechanism for tokamak rotation. Our hypothesis is: (i) that edge instabilities saturate by the generation of filamentary coherent structures (blobs) which convect radially outward towards the wall; and (ii) when the underlying unstable waves carry momentum (i.e. have a preferred phase velocity), the momentum is transferred to the blobs and lost from the core plasma, providing a recoil force that can rotate the core. To test these ideas, a simple two field (2D PDE) model is proposed which embodies the essential features of collisionless electrostatic drift wave instability and curvature-driven blob transport in the separatrix layer. The model has sub-limits which reduce to the Hasegawa-Mima equation, and the blob propagation equation. Progress in understanding blob generation and the transport of momentum in this system using analytical and numerical methods will be reported. [Preview Abstract] |
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UP1.00003: A Novel Diagnostic For Ion Temperature Fluctuations Vladimir Sokolov, Amiya K. Sen The local measurement of radial ion thermal transport is an important issue in all plasma confinement experiments. In principle this requires the measurement of local ion temperature fluctuations. Compact double gridded electrostatic ion energy analyzers (IEA) are routinely used to measure equilibrium ion temperature. However, these cannot be used for fluctuating ($\sim 100kHz$) ion temperature measurements. This has motivated us to develop a new time dependent ion energy analyzer based on feedback. The novel physical idea is to modulate the retarding field synchronously at the fluctuation frequency (50-150 KHz) via feedback. The ion current from Langmuir probe is used as a feedback signal and applied on energy selector grid of IEA. The simultaneous measurement of ion currents of analyzer $I_{IEA}(t)$ and Langmuir probe $I_{LP} (t)$ allow us to determine local fluctuations density n(t), temperature $T_i (t)$, the ion thermal flux and conductivity.\\ This research was supported by U.S.Department of Energy Grant No. DE-FG02-98ER-54464. [Preview Abstract] |
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UP1.00004: Visualizing Gyrokinetic Turbulence in a Tokamak George Stantchev, William Dorland Multi-dimensional data output from gyrokinetic microturbulence codes are often difficult to visualize, in part due to the non-trivial geometry of the underlying grids, in part due to high irregularity of the relevant scalar field structures in turbulent regions. For instance, traditional isosurface extraction methods are likely to fail for the electrostatic potential field whose level sets may exhibit various geometric pathologies. To address these issues we develop an advanced interactive 3D gyrokinetic turbulence visualization framework which we apply in the study of microtearing instabilities calculated with GS2 in the MAST and NSTX geometries. In these simulations GS2 uses field-line-following coordinates such that the computational domain maps in physical space to a long, twisting flux tube with strong cross-sectional shear. Using statistical wavelet analysis we create a sparse multiple-scale volumetric representation of the relevant scalar fields, which we visualize via a variation of the so called splatting technique. To handle the problem of highly anisotropic flux tube configurations we adapt a geometry-driven surface illumination algorithm that places local light sources for effective feature-enhanced visualization. [Preview Abstract] |
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UP1.00005: Results in Guiding-center Kinetic Theory (Applicable to Antimatter Synthesis) R. Stowell Three new results are presented. (1) The first expression valid at all points in space for the dynamical Debye response of a plasma to a moving charged particle is presented. Previous results (Oberman '70) are valid very far from a super- thermal charged particle in a thermally equilibrated plasma without a magnetic field. In contrast, the present result is valid everywhere and for a particle of any velocity in a guiding-center (${\omega_p^2}/{\omega_c^2}{\;}{\ll}{\;}1$) plasma with any distribution function. (2) Of several new collision operators derived, the one corresponding to the spatially localized generalization to multiple species of the Dubin-O'Neil operator (Dubin and O'Neil '97) is studied in detail. For the first time, the integral over wave number is removed by evaluation from an analog (the present analog) of the Balescu-Guernsey-Lenard (BGL) operator. While this operator provides the leading-order contribution due to collisions, it is found not to thermally equilibrate most plasmas. (3) Using a result from differential topology, the Penrose criterion for kinetic stability (Penrose '60) is generalized to give the number of unstable modes of a plasma for any given wave number. In contrast, the Penrose criterion indicates whether at least one unstable mode exists. [Preview Abstract] |
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UP1.00006: Self-Consistent Phase-Space Moment Description of High-Energy-Density Plasma Jets Jing Zhou, Chiping Chen A self-consistent phase-space moment description is developed for high-energy-density plasma jets. The phase-space moment theory is the truncated moment average of the kinetic equation. Using the phase-space moment theory, the root-mean-square (rms) envelope equations, which describe the orientation and size of the plasma jet, are derived for high-energy-density plasma jets. The envelope equations are demonstrated to agree with the virrial theorem, which is the one of the most fundamental theorems in plasma physics. As an example, the rms envelope equations are solved for a co-axial plasma jet accelerator, where the collisions and radiation transport are considered negligibly small. The rms envelope equations can be used to study the energy density ultimately achievable in a plasma jet as it is ejected from a plasma gun and subsequently undergoes compression by inertia. [Preview Abstract] |
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UP1.00007: Effect of intense laser irradiation on the lattice stability of metals and semi-conductors using ab initio simulations. Vanina Recoules, Jean Clerouin, Gilles Zerah, Pierre-Mathieu Anglade, Stephane Mazevet We studied the effect of intense electronic excitations on the interatomic forces for electronic temperatures reached under intense laser irradiation and the possible melting of the underlying lattice. We use {\it ab initio} linear response to compute the phonon spectrum for a semi-conductor (Si) and two metals (Al and Au), using linear response in the Density Functional Theory framework for several electronic temperatures lying from 1 to 8 eV. We found that silicon and gold behave in an opposite ways when increasing electronic temperature: whereas a phonon instability appears in silicon at a electronic temperature of $1.5\;\rm{eV}$, gold samples become even more stable with increasing electronic temperature. The Debye temperature was deduced from the phonon spectrum and using the Linderman criterion, we showed that gold undergoes a sharp increase of its melting temperature under intense laser irradiation. [Preview Abstract] |
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UP1.00008: Particle dynamics in relativistic sheared layers and acceleration of Ultra High Energy Cosmic Rays Maxim Lyutikov Relativistic outflows carrying large scale magnetic fields have large inductive potential and may accelerate protons to ultra high energies. We discuss a novel scheme of Ultra-High Energy Cosmic Ray acceleration due to drifts in magnetized, cylindrically collimated, sheared jets of powerful active galaxies. A proton carried by such a plasma is in an unstable equilibrium if ${\bf B} \cdot \nabla \times {\bf v}< 0$, so that kinetic drift along the velocity shear would lead to fast, {\it regular} energy gain. Acceleration rate {\it increases} with energy reaching at highest energies the absolute theoretical maximum of inverse relativistic gyro-frequency. [Preview Abstract] |
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UP1.00009: Comparison of Semi-Lagrangian Algorithms for Solving Vlasov-type Equations Stephan Brunner, Trach-Minh Tran, Maura Brunetti In view of pursuing CRPP's effort in carrying out gyrokinetic simulations using an Eulerian-type approach [M. Brunetti {\it et. al}, Comp. Phys. Comm. {\bf 163}, 1 (2004)], different alternative algorithms have been considered. The issue is to identify the most appropriate time-stepping scheme, both from a point of view of numerical accuracy and numerical efficiency. Our efforts have concentrated on two semi-Lagrangian approaches: The widely used cubic B-spline interpolation scheme, based on the original work of Cheng and Knorr [C. Z. Cheng and G. Knorr, J. Comp. Phys. {\bf 22}, 330 (1976)], as well as the Cubic Interpolation Propagation (CIP) scheme, based on cubic Hermite interpolation, which has only more recently been applied for solving Vlasov-type equations [T. Nakamura and T. Yabe, Comp. Phys. Comm. {\bf 120}, 122 (1999)]. The systematic comparison of these algorithms with respect to their basic spectral (diffusion/dispersion) properties, as well as their ability to avoid the overshoot (Gibbs) problem, is first presented. Results from solving a guiding-center model of the two-dimensional Kelvin-Helmholtz instability are then compared. This test problem enables to address some of the key technical issues also met with the more complex gyrokinetic-type equations. [Preview Abstract] |
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UP1.00010: Transport Studies of Bean- and Oval-Shaped Plasmas in DIII-D through Gyrokinetic Simulations R.V. Bravenec, F.L. Waelbroeck, E.A. Lazarus, W. Dorland Bean- and oval-shaped plasmas exhibit qualitative differences in ion transport and extreme differences in electron transport inside the sawtooth inversion radius during sawtooth reheat [1]. Here we attempt to understand this through gyrokinetic simulations. The GS2 code [2] is used because it is able to use actual equilibrium reconstructions necessary for the bean-shaped plasma. Both linear and nonlinear simulations will be presented (maximum growth rates and diffusivities, respectively). Of particular interest are the saturation of the ion temperature ramp in the bean discharges and the surprisingly low, near neoclassical values of the ion diffusivity in the oval discharges.\par \vspace{0.5em} \noindent [1]~E.A.\ Lazarus, et al., Proc.\ 20th IAEA Fusion Energy Conf., paper IAEA-CN-116/EX/PS-11.\par \noindent [2]~W.D.\ Dorland, et al., Phys.\ Rev.\ Lett.\ ${\bf 85}$, 5579 (2000). [Preview Abstract] |
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UP1.00011: POSTDEADLINE |
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UP1.00012: Implementation of Field Error and Resistive Wall Boundary Conditions in Finite Element Codes Scott Kruger, Dalton Schnack Current tokamak experiments depend critically on the boundary conditions of the magnetic fields for effective operation. While non-axisymmetric boundary conditions have been considered deleterious for plasma operation because of locked modes locked modes [J.T. Scoville et.al Nuclear Fusion 31, 875 (1991)], recent experiments show they might be advantageous for ELM control [T.E. Evans et.al. PRL 92, 235003 (2004)]. Instabilities which can arise due to the finite resistivity of the wall have also emerged as a emerged as a problem for advanced tokamak operation. \footnote{A. Garafalo et.al. Phys. Plasmas 9, 1997 (2002)} Implementation of these boundary conditions into finite element codes requires a different formulation of the boundary conditions as compared to the finite difference codes in earlier work [D.J. Ward and A. Bondeson, Phys. Plasmas 2, 1570 (1995)]. Here, we review the proper formulation with particular attention paid to numerical accuracy of the method. [Preview Abstract] |
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UP1.00013: Initial comparison of low mass, high current alumino-silicate ion sources David Baca Near-term High Energy Density Physics (HEDP) experiments prefer low mass ion sources and high current density. Thermionic emission from solid materials, such as, large diameter (2-10 cm) K$^{+}$ alumino-silicate surface ionization emitters have proven to be very reliable, long-lived, and supply current densities in the range of 2.5-10.0 mA/cm$^{2}$ for several experiments including the High Current Experiment (HCX) and Neutralized Drift Compression Experiment (NDCX). Recently, low mass alkali alumino-silicate materials coated onto porous tungsten substrates were fabricated and their space-charge limited ion emission properties were measured at an extraction electric field of 40 kV/cm and pulse duration of 20$\mu $s. In our presentation, Li+ and Na+ alumino-silicate ion sources will be compared to the previously characterized K+ and Cs+ alumino-silicate emitters. This data will show that either sodium or lithium ion sources can meet HEPD requirements. [Preview Abstract] |
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UP1.00014: Convective stability of a magnetized plasma containing cosmic rays Benjamin Chandran, Timothy Dennis Convection plays an important role in a variety of astrophysical settings, including stellar interiors, accretion flows, and the hot plasma between galaxies in galaxy clusters. As shown by S. Balbus (2000), magnetic fields powerfully affect the convective stability criterion in low-density plasmas by constraining heat to diffuse along magnetic field lines. In this poster, we extend Balbus' analysis by including cosmic rays, but restrict our focus to non-rotating plasmas. We derive the convective stability criterion, provide a physical description of stable and unstable modes, and discuss the implications of our work for convection in clusters of galaxies and the so-called ``cooling-flow problem.'' The convective modes that we discuss are similar to the local Parker instability in the high-beta limit, except that we take into account anisotropic thermal conduction and allow the equilibrium to be non-isothermal. [Preview Abstract] |
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UP1.00015: Persistent Spatially-Driven Kinetic Waves in Pure Electron Plasmas William Bertsche, Joel Fajans, Bedros Afeyan For the first time, high amplitude ($\Delta $n/n$\approx $40{\%}), high $Q $(up to 100,000) Bernstein, Greene, and Kruskal modes have been controllably excited in a non-neutral electron plasma with a spatially localized electrostatic drive. The modes are created by sweeping an excitation voltage downwards in frequency, thereby dragging a phase space ``bucket'' of low density into the bulk of the plasma velocity distribution. The modes have no linear limit and are instrinsically kinetic in nature. Preliminary experiments using a fixed-k drive for these waves and comparison with kinetic electrostatic electron waves investigated in neutral laser-plasma systems will be presented. [Preview Abstract] |
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UP1.00016: EOS and transport properties of dense carbon and aluminum plasmas Gerald Faussurier, Christophe Blancard, Patrick Renaudin The electronic and ionic structures of dense aluminum and carbon plasmas are determined self-consistently using the average-atom model SCAALP (Self-Consistent Approach for Astrophysical and Laboratory Plasmas) based on the finite-temperature density-functional theory and the Gibbs-Bogolyubov inequality. Various EOS data, such as internal energy, pressure, entropy, and sound speed, are calculated by numerical differenciation of the plasma Helmholtz free energy. The electronic electrical conductivity is obtained from the Ziman approach. We present numerical results for Hugoniot curves with non-standard density-temperature initial conditions. Comparisons with recent experiments are also presented and discussed. [Preview Abstract] |
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UP1.00017: Relativistic radiation damping for simulation Amodsen Chotia, John Verboncoeur The aim of this work is to implement radiation braking into a simulation code. Radiation physics of accelerated charges is not new. It dates from the end of the 19th century, from Maxwell theory and Larmor, Poynting, Thomson, Poincare, Lorentz, Von Laue, Abraham, Schott, Planck, Landau, Einstein, Dirac, Wheeler et Feynmann (and many others). The result reaches out from the length of life of exited levels of atoms, antennas, and lays out through specific production of radiation by bremsstrahlung in particles accelerators but also spatial and stellar astrophysics. In this work we start from Landau Lifchitz equation to express the quadrivector acceleration in term of the fields. Using a result from Pomeranchouck we deduce the energy lost by radiation. We do an instantaneous colinear projection of the velocity vector in order to substract the loss of kinetic energy due to radiation. The equation of motion is then solved based on Boris algorithm. The code is tested on few examples. [Preview Abstract] |
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UP1.00018: ICF calculations with incorporation of an exact Riemann solver into the RAGE hydrodynamics algorithm J.G. Wohlbier, J.H. Cooley, J.W. Grove, E.D. Dendy Successful calculations of inertial confinement fusion implosions depend critically on the use of an accurate and well behaved hydrodynamics algorithm. Extensive use of the RAGE code~[1] is expected in ICF applications, especially for future NIF calculations. We have implemented an exact Riemann solver~[2] together with a MUSCL-Hancock time centering~[3] in the RAGE code hydro algorithm. In this paper we compare results for representative ICF calculations before and after the inclusion of the modifications. We compare, for example, the generation of grid-seeded instabilities and computed values of shock speeds as a function of grid refinement. [1] R.M.~Baltrusaitis {\em et al.}, {\em Phys.~Fluids} {\bf 8} (9), 2471--2483 (1996). [2] P.~Colella and H.~Glaz, {\em J.~Comput.~Phys.}, vol.~59, pp.~264--289, 1985. [3] B.~van Leer, {\em 16th AIAA Comp.~Fluid Dynamics Conf.}, AIAA 2003-3559. [Preview Abstract] |
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UP1.00019: Classical Theory of Compton Scattering Frederic Hartemann, David Gibson, Arthur Kerman The Dirac-Lorentz equation describes the dynamics of a classical point charge in an electromagnetic field, accounting for radiative effects in a manifestly covariant and gauge invariant manner. The validity of this equation is assessed by direct comparison between the Dirac-Lorentz dynamics of an electron subjected to a plane wave in vacuum and the well-known recoil associated with Compton scattering. In the small recoil limit, the classical Dirac-Lorentz is shown to yield the correct momentum transfer. For larger values of the recoil, the quantum scale appears explicitly, and the classical Dirac-Lorentz equation does not properly model this situation, as shown by deriving an exact analytical solution for a monochromatic plane wave of wavenumber $k$ to any order in \textit{kr}, where $r$ is the classical electron radius. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. [Preview Abstract] |
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UP1.00020: High-Energy Scaling of Compton Scattering Sources Frederic Hartemann, David Gibson, Scott Anderson, Aaron Tremaine, Ed Hartouni, Chris Barty No monochromatic, high-brightness, tunable light sources currently exist above 100 keV. Important applications that would benefit from such new hard x-ray sources include: nuclear resonance fluorescence spectroscopy, time-resolved positron annihilation spectroscopy, and MeV flash radiography. The peak brightness of Compton scattering light sources is derived for head-on collisions and found to scale with the electron beam brightness and the drive laser pulse energy. This $\gamma ^{2}$-scaling shows that for low emittance electron beams (1 nC, 1 mm.mrad, $<$ 1 ps, $>$ 100 MeV), and tabletop laser systems (1-10 J, 5 ps) the x-ray peak brightness can exceed 10$^{23}$ photons / mm$^{2}$ x mrad$^{2}$ x s x 0.1{\%} bandwidth near 1 MeV; this is confirmed by 3D codes that have been benchmarked against Compton scattering experiments performed at LLNL. Important nonlinear effects, including spectral broadening, are also taken into account in our analysis; they show that there is an optimum laser pulse duration in this geometry, of the order of a few picoseconds, in sharp contrast with the initial approach to laser-driven Compton scattering sources where femtosecond laser systems were thought to be mandatory. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. [Preview Abstract] |
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UP1.00021: Ignition of a Fusion Flame in DT by Nonlinear Force Driven Plasma Blocks at PW-ps Laser Irradiation Heinrich Hora, George Miley, J. Badziak, Jie Zhang It seemed to be an impossible task thirty years ago to shine a laser beam on uncompressed solid DT and to ignite a fusion flame because of the necessary energy flux densities are in the range of more than 100MJ/cm$^{2}$ or corresponding deuterium ion current densities above 10$^{10}$ Amp/cm$^{2}$. Since PW-ps laser pulses are available now, the situation has changed, however, by inclusion of a very sophisticated method for suppressing prepulses such that relativistic self-focusing is avoided and a purely plane or similar geometry interaction as a skin layer process appears. These conditions have been verified by very special experiments in agreement with predicted theory and detailed computations [1]. This leads to the space-charge neutral plasma blocks or pistons generated by the nonlinear (ponderomotive) acceleration for producing the necessary ion current densities for the optimized energies of 80 keV to irradiate DT [2]. [1] J. Badziak, S. Glowacz, S. Jablonski, P. Parys, J. Wolowski, H. Hora, Appl. Phys. Letters\underline { }\textbf{85, }3041 (2004). [2] H. Hora, Laser and Particle Beams\textbf{ 22, }439 (2004) [Preview Abstract] |
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UP1.00022: Debye Layers in Plasmas Generalized to Hadron Confinement of Nuclei and Quark-Gluon-Plasmas Heinrich Hora, George H. Miley $. $A new theory for the nuclear forces for confining the hadrons in a nucleus has been derived from a generalization of the Debye layer as known from the plasma ablation at laser irradiation where the temperature is substituted by the Fermi energy of the nucleons [1]. The first convincing proof is by using the empirical density of the nucleons defining their Fermi energy to arrive at a Debye length of about 3 fm as measured by Hofstadter for the decay of the nucleon density at the surface of heavy nuclei. This decay is interpreted as Wigner scattering and the Goos-Haenchen effect. With the same steps of substitutions, the surface energy of nuclei is always too small against the nucleon enthalpy to confine the hadrons until the density reaches such high values reproducing the empirical known radii of nuclei. By this way nuclei are possible only until uranium or curium by a Boltzmann equilibrium process explaining the endothermic generation of heavy nuclei in the Universe [2]. At and about six times higher nucleon density, the Fermi statistics changes into its relativistic branch excluding nucleation in neutron stars and explaining the quark-gluon plasma. [1] \textit{Edward Teller Lectures}, H. Hora and G.H. Miley eds. (Imperial College Press London 2005) p. 103. [2] H. Hora, G.H. Miley, F. Osman, Astrophysics and Space Science, \textbf{298}, 247 (2005) [Preview Abstract] |
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UP1.00023: Monte Carlo simulations of gated microchannel plate x-ray detectors Craig Kruschwitz, Ming Wu, Jiaming Morgan, Dane Morgan High-speed, gated x-ray detectors based on straight-channel microchannel plates are a powerful diagnostic tool for two-dimensional, time-resolved imaging and time-resolved x-ray spectroscopy in the field of laser-driven inertial confinement fusion and fast z-pinch experiments. For these applications a short high-voltage pulse (typically a few hundred picoseconds) is sent across a microstrip transmission line coated onto the microchannel plate, thus producing the desired gating. The subject of this paper is a Monte Carlo code that we developed to simulate the electron cascade in a microchannel plate under such pulsing. The model includes the effects of space charge and channel wall charging. These contribute to high gain saturation in the microchannel plate. Additionally, elastic reflection of low-energy electrons from the channel wall, which is important at lower voltages, is also included. The model results are compared to measured microchannel plate sensitivities and good agreement is found. The results of simulations of pulsed behavior are presented and ramifications are discussed. [Preview Abstract] |
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UP1.00024: The LIL Facility: Overview Gaston Thiell The completion of the ``Ligne d'Intégration Laser'' (LIL) is a major milestone of the Laser M\'egaJoule (LMJ) project\footnote{C. Cavailler, N. Camarcat, F. Kovacs and M. André, Inertial Fusion Sciences and Applications 2003, September 7-12, 2003, pp. 523-528.}. The LIL Facility has been designed to achieve two main goals: i) act as a prototype beamline to demonstrate LMJ performances, ii) perform applied research into the physics of high temperatures and high densities. We discuss here the results of 1$\omega$ and 3$\omega$ commissioning shots for one quad of beams (30kJ total energy in 3.5ns at 0.35$\mu$m). The Stimulated Raman Scattering effects in the beam transport path are characterized using spatially shaped pulses and it is shown that the spatial modulation rate and the spot diameter of the best focus meet the LMJ requirements. The LIL quad of beams was focused using focusing diffraction gratings on solid targets for plasma diagnostics commissioning. The advantages of this final focusing system will be highlighted for laser-plasma interaction experiments and preliminary results of plasma experiments will be given. [Preview Abstract] |
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UP1.00025: Wave excitation by microwave power modulation in unstable linear ECR plasma Hayato Tsuchiya, Y. Nagasima, A. Fujisawa, S. Shinohara, Y. Kawai, K. Itoh, S.-I. Itoh Understandings of the wave structures in turbulent plasmas and their nonlinear processes are important topics concerning to plasma structural formation. The characteristics of waves excited by the external force have been investigated for clarifying the dominant nonlinear process caused by the flute instability. An ECR plasma is produced by 2.45 GHz microwaves in the mirror magnetic field with argon pressure of 0.4 mTorr. The electron density is 10\^{}11cm\^{}-3, and the electron temperature is 5 eV. Fluctuations excited by the flute instability are measured with several Langmuir probes. The frequency of the flute instability is about 4 kHz. The power of the microwaves is modulated at the frequency from 1 to 10 kHz in order to excite the test waves. The test waves do not have azimuthal but radial eigenmode structure. When the modulation frequency is lower than that of the flute instability of 4 kHz, this instability tends to be suppressed. On the other hand, as the modulation frequency becomes higher than 4 kHz, the power spectrum of the flute instability becomes sharper (more coherent). Aspects of nonlinear interaction between the flute instability and the excited test waves are discussed. [Preview Abstract] |
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UP1.00026: Diagnosing the Magnetic Structure of the Sustained Spheromak Experiment Hillary Cummings, Carlos Romero Talamas, David Hill, Harry McLean, Reg Wood Unlike in traditional fusion devices, SSPX plasmas are confined by a magnetic field that is predominately generated by the plasma itself. The process by which plasma creates and changes the magnetic field is complicated and therefore makes it difficult to know its exact structure everywhere in the plasma at any point in time. This poster describes three different methods of studying the magnetic structure of the experiment; using edge probes in conjunction with Corsica- an equilibrium fitting code, imaging the plasma with a high-speed intensified CCD camera, and inserting an array of magnetic probes internal to the plasma. The research was performed under appointment to the Fusion Energy Sciences Fellowship Program and supported by US DOE. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. [Preview Abstract] |
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UP1.00027: Drift Wave Excitation in Linear ECR Plasma Kunihiro Kamataki, Y. Nagashima, S. Shinohara, Y. Kawai, M. Yagi, K. Itoh, S.-I. Itoh In hot plasmas, there has been considerable interest in turbulence, especially drift wave turbulence, because of its role in anomalous transport. Here, we show an experimental study of the drift wave instability in bounded linear Electron Cyclotron Resonance (ECR) plasma device (inner diameter i.d. is 400 mm and axial length $L$ is 1200 mm). Plasma parameters were measured with Langmuir probes. ECR plasma was produced by launching a microwave with the frequency of 2.45GHz through a coaxial chamber (i.d.= 100 mm and $L$= 210 mm). By installing this, the plasma radius became smaller and the strong radial gradient in density was formed. In addition the axial boundary condition was determined by metals on both ends of chamber. By imposing these two boundary conditions, the drift wave was successfully excited. Furthermore, we found two modes were coexistent in Ar gas pressure $P$=1.0$\sim $1.6mTorr: the one was drift wave and the other was flute wave from the measurements of the axial wave number and the direction of azimuthal propagation. The drift wave was not observed when $P>$ 1.6mTorr. The present result suggests that the growth rate of drift instability is related to the ion-neutral collision frequency, which is proportional to gas pressure. The co-existence of two instability modes allows to study nonlinear interaction between them. [Preview Abstract] |
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UP1.00028: In-Situ Plasma Surface Interaction Diagnostics for Magnetic Fusion Soren Harrison, Dennis Whyte The real-time in-situ diagnosis of plasma surface interaction (PSI) processes, such as erosion, deposition and fuel retention, are presented. Such diagnostics are mostly absent in present fusion devices, but are necessary to improve our understanding of PSI toward the design and operation of ITER. Two in-situ PSI diagnostics are examined. Quartz-microbalances (QMB) are being installed in the DIII-D inner divertor for spring '06 operation. The QMBs will measure neutral particle (C) deposition behind protective tile gaps on a shot-to-shot basis. Deposition will be monitored over entire shot cycles, and during bakes. Development of a new Alpha Radiation Remote Ion Beam Analysis (ARRIBA) diagnostic for use in magnetic confinement devices is ongoing. ARRIBA will provide depth-resolved measurement of elemental concentrations and hydrogenic fuel retention on tile surfaces exposed to high local heat loads, such as the divertor. Both the QMBs and ARRIBA will allow erosion/deposition/retention measurements to be correlated with plasma conditions. Quartz Microbalance work supported by U.S. DOE. [Preview Abstract] |
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UP1.00029: Attosecond electron beam controllably generated from plasma layer by superintense ultrashort laser pulse Victor Kulagin, Min Sup Hur, Hyyong Suk, Vladimir Cherepenin For controllable generation of ultrashort electron beams, we propose to use a thin plasma layer (with or without compensating positive charge) irradiated normally by a super-high intensity ultrashort laser pulse [1,2]. The electrons of the plasma layer are accelerated during laser pulse action longitudinally to relativistic velocities by the nonlinear component of the Lorentz force, provided a dimensionless field amplitude is large enough. We show analytically and by 2D PIC simulations that it is possible to choose the parameters of the laser pulse and the plasma layer in such a way that only \textit{a single short and ultracold relativistic electron beam} will be produced (and can survive for some time) rather than a cloud of chaotically moving electrons. To realize this, the transparency of the plasma layer has to be large enough, the amplitude of the laser pulse has to be relativistic, and the laser pulse has to have a sharp rising edge. These ensure that the bunch will be greatly compressed in longitudinal direction at the initial stage of interaction with the front of the laser pulse. The theory for this process is elaborated, and results are compared with 1D PIC simulations. [1]. V. V. Kulagin, V. A. Cherepenin and H. Suk, Appl. Phys. Lett., \textbf{85}, 3322 (2004). [2]. V. V. Kulagin, V. A. Cherepenin and H. Suk, Phys. Plasmas, \textbf{11}, 5239 (2004). [Preview Abstract] |
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UP1.00030: Experimental results of the quasi-monoenergetic electron beam generation from the self-modulated laser wakefield acceleration using a pinhole-like collimator Hyyong Suk, Nasr Hafz, Hyojae Jang, Changbum Kim, Guanghoon Kim We report recent results from the self-modulated laser wakefield acceleration experiment that has been carried out at KERI (Korea Electrotechnology Research Institute), For this experiment, we used a 3 TW Nd:glass/Ti:sapphire hybrid laser system that can deliver an energy of 2.1 J with a pulse duration of 700 fs. In the experiment, the high power laser beam is focused to a beam size of $\sim $ 10 microns in the supersonically ejected He gas jet (density$\sim $10\^{19} cm\^{-3}) by a parabolic mirror. The strong laser-plasma interaction led to production of MeV-level high energy electrons up to $\sim $10 MeV. We used a pinhole-like collimator with a diameter of 1 mm to select only high energy electrons that propagate along the axis. In this way, we could obtain quasi-monoenergetic high-energy electrons. Detailed beam and plasma parameters were measured by using several diagnostic tools including an ICT for charge measurement, dipole magnet/lanex film for energy and energy distribution, spectrometer for plasma density from the Raman scattered laser beam, etc. In this presentation, detailed experimental results are shown. [Preview Abstract] |
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UP1.00031: Dynamics of plasma parameters during high pressure gas injection in tokamaks Elena Baronova, Victor Vikhrev, Dmitrii Morozov We propose two-fluid model, based on energy balance equations to describe plasma dynamics during high pressure gas injection in tokamaks. Model includes energy exchange between electrons and ions, Joule heating, radiation losses, generation of high energy electron beam (run away `seed' and avalanche effect are taken into account). Special attention is given to the calculation of radiation losses in unstable plasma. Density effect and opacity effects are analyzed in detail. Calculations are made for argon, neon, xenon gases. Dynamics of radiation losses is compared with that, measured in experiments. The results of calculations are in good agreement with experimental results on DIII-D machine. [Preview Abstract] |
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UP1.00032: Pulsed Flow Pinch Charles Hartman, David Reisman Formation of a Pulsed Flow Pinch is discussed, based on 2-D, MHD numerical calculations. The PFP utilizes the observed stable, Btheta magnetic ``bubble'' which propagates from breach to muzzle during the run-down phase of the coaxial Marshall gun. We consider two ways of launching a PFP onto a fiber or cylindrical gas cloud: 1) by propagating the bubble to small radius along an exponentially-decreasing-radius center conductor and, 2) by a radial launch to form reflex PFP's propagating in opposite directions along a fiber. We show that the bubble velocity increases to high values as the radius is decreased making the rise time of Btheta at an axial point very short. A bubble, launched into uniform gas is found to undergo unstable pinching of the front. Results will be presented of calculations of a PFP driven, neutron-producing, snow-plow pinch. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. [Preview Abstract] |
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UP1.00033: Laser Scattering From a Gas Jet Plasma Source Staci Brown, Arnesto Bowman, R. Williams The plume of a gas jet plasma source is studied using YAG and CO$_2$ lasers and a pulsed electron beam. The piezoelectric valve's opening and closing times are studied using HeNe and YAG lasers. Shadowgraphy is used to obtain images of the plume and to help align the lasers to the plume. Also discussed are attempts to generate and detect plasma waves in the plume. [Preview Abstract] |
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UP1.00034: Characteristics of an Electron Beam for User in Plasma Wave Probe Measurements Arnesto Bowman, Staci Brown, R. Williams We discuss measurements made to characterize an electron beam (5 to 50 keV) which is being used in experiments designed to measure the amplitude of laser generated plasma waves. Recently, the electron gun was operated in the pulsed mode with pulse lengths of 10 to 100 ns. Also the electron gun was pulsed synchronously with a gas jet plasma source, YAG laser and optical detectors. Also to be discussed are the Faraday Cup for measuring beam current, beam emittance measurements and calculations, and deflection of the electron beam by the earth's magnetic field.. [Preview Abstract] |
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UP1.00035: Limits for light intensification by reflection from relativistic plasma mirrors Andrei Solodov, Vladimir Malkin, Nathaniel Fisch Two new schemes for light intensification towards the vacuum breakdown intensities (the Schwinger limit) have been proposed recently [S. V. Bulanov et al., Phys. Rev. Lett. 91, 085001 (2003) and S. Gordienko et al., Phys. Rev. Lett. 94, 103903 (2005)], which contemplate huge frequency upshifts of laser pulses by means of reflection from ultra-relativistic plasma mirrors. Were these scheme to work, they would provide remarkable reduction in size and costs of lasers capable of producing the vacuum breakdown intensities. We show that there are severe limitations for laser frequency upshifts, that may prevent these schemes from reaching the Schwinger limit. [Preview Abstract] |
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UP1.00036: Anomolous Inward Particle Transport and Alcator Internal Transport Barrier B. Coppi The inward particle transport in the outer region of the plasma column has been attributed\footnote{B. Coppi and C. Spight, \textit{Physical Review Letters} \textbf{41} (8), 551 (1978)} to the combined effects of the collisional longitudinal electron thermal conductivity, the electron temperature gradient and the excitation of the ion temperature gradient driven mode. Since the density can penetrate toward the core of the plasma column, we consider that Inhomogenous Electron Temperature Gradient Driven Modes that are localized near rotational magnetic surfaces by the effects of magnetic shear like the ITG mode presented in Ref.\footnote{B. Coppi, M. Rosenbluth, R. Sagdeev, \textit{Phys. Fluids} \textbf{10}, 582 (1967)}, are shown to take over directly or indirectly the task of carrying particle inward if the ion temperature gradient is larger than the density gradient. An interpretation of the onset of the Internal Transport Barrier formed by off axis ICRH in a series of Alcator C-Mod experiments is interpreted as a displacement toward the outside of the inflexion point of the ion temperature profile where the degree of collisionality is higher and the particle inflow is more vigorous. Then, the density profile becomes more peaked in the center of the plasma column and the ITG modes that can carry angular momentum toward this region are suppressed\footnote{B. Coppi, \textit{Nucl. Fusion} \textbf{42}, 1-4 (2002)}. \\ $^*$Supported in part by the US DOE. [Preview Abstract] |
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UP1.00037: Reduced, FLR, 2-fluid equations in 3-dimensional paraxial geometry. J.J. Ramos, A. Ishizawa A reduced, finite-Larmor-radius, two-fluid system for plasmas in a strong but weakly varying magnetic field is derived by means of asymptotic expansions of the fluid moment equations in two basic small parameters. The first one is the ratio between the ion gyroradius and the characteristic length scales perpendicular to the magnetic field. The second one is a measure of the magnetic field inhomogeneity, assumed to be comparable to the ratio between characteristic perpendicular and parallel length scales, and to the plasma beta. The relevant time scales exclude the fast magnetosonic waves while including the Alfven, sound and drift waves, and the flow velocities are ordered formally as comparable to the ion thermal speed. By keeping only linear terms in these two small parameters, a consistent fluid closure is achieved. This result is consistent with but more general that Newcomb's paraxial closure theorem derived within the framework of collisionless kinetic theory. Our system provides an extenstension of Hazeltine et al.'s four-field model. It includes diamagnetic effects, temperature gradients, pressure anisotropy, parallel flows, and Hall physics in the generalized Ohm's law. Electron inertia is retained only in the parallel component of Ohm's law, in order to make the model applicable to collisionless reconnection problems. [Preview Abstract] |
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UP1.00038: Equilibrium Reconstruction Techniques Applied to Compact Toroid Plasmas in MRX S.P. Gerhardt, M. Yamada, H. Ji, M. Inomoto We have developed a code for the solution of the Grad-Shafranov equation, constrained by available measurements, for compact toroid plasmas in MRX. While these methods have been commonplace in tokamak research and have been applied for RFP and spheromak plasmas as well, this represents a new application of the techniques to Field Reversed Configuration (FRC) plasmas. We model the vacuum vessel as a perfect flux-conserver when calculating Green's tables, which are subsequently used for fast calculations of the magnetic field in MRX. The code consists of two loops: an outer loop where the profiles and other free parameters are varied, and an inner loop where the Grad-Shafranov equation is solved by simple iteration. Data used to constrain the equilibrium include arrays of internal magnetic probes, plasma current Rogowski coils, and limited pressure information from Langmuir probes and Doppler Spectroscopy. The calculations illustrate that a significant variety of plasma shapes are available in MRX through control of the equilibrium field curvature. In particular, the external field index can be controlled, leading to different rigid-body stability regimes in MRX. This work is funded by the Department of Energy. [Preview Abstract] |
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UP1.00039: Virtual Diagnostics Toolset for Tokamak Simulations Jin-Soo Kim, Alan Turnbull FAR-TECH, Inc. is develpoing a virtual diagnostics toolset for tokamak simulations. As plasma modeling and simulation become mature, virtual diagnostics for tokamak simulations are poised to provide valuable data to be compared to experiments for further advancement of tokamak research. A virtual diagnostics toolset that allows direct comparison of numerical simulation with tokamak measurements can provide a valuable tool for thorough understanding of tokamak plasmas and further define future necessary diagnostics. A paradigm of the project will be presented using a linearized MHD instability as an example. Work supported by US Depatrment of Energy. [Preview Abstract] |
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UP1.00040: A finite element elliptic solver for gyrokinetic particle simulations in a global field aligned mesh Y. Nishimura, Z. Lin, M.F. Adams, D.E. Keyes, W. Lee, J. Manickam In the presence of non-adiabatic kinetic electrons, the inversion matrix for the gyrokinetic Poisson equation is no longer diagonally dominant. An iterative method cannot be applied. The challenge is to develop an efficient solver applicable to a global field-aligned mesh with a resulting matrix of rank of order a million. A new finite element solver is developed with the aid of an algebraic multigrid (AMG) method, employing PETSc,\footnote{PETSc: Portable Extensible Toolkit for Scientific computation,\\ (http://www-fp.mcs.anl.gov).} {\it hypre},\footnote{{\it hypre}: high performance preconditioners (http://www.llnl.gov/casc).} and Prometheus.\footnote{Prometheus: (http://www.columbia.edu/~ma2325/prometheus).} The field aligned mesh can be applied to the open-field-line regions as long as the magnetic field is given by the Clebsch form ${\bf B} = \nabla \psi \times \nabla ( \theta - \zeta / q ).$ As one of the exercises, we apply our finite element field solver to a tokamak divertor geometry. This work is supported by Department of Energy, Scientific Discovery through Advanced Computing (SciDAC). [Preview Abstract] |
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UP1.00041: Gridless DSMC using dynamic octrees Andrew Christlieb, Spencer Olson This work concerns the development of a gridless simulation tool for collisional plasmas. In this paper we focus on one part of this tool: a gridless algorithm for modeling the inter-particle collisions of a gas. Using an octree algorithm to automatically cluster the spatial distribution of particles, we implement a gridless Direct Simulation Mont\'e Carlo (DSMC) algorithm. Conventional fixed-grid algorithms are susceptible to grid-mismatch to the physical system, resulting in erroneous solutions. On the contrary, a gridless DSMC algorithm can be used to simulate various physical systems without the need to perform grid-mesh optimization. This provides additional flexibility for domains with extremely complex geometries. In DSMC, local macroscopic quantities are needed to maintain correct collision rates and are used to reduce statistical noise. Many of these macroscopic quantities tracked per grid cell are time-averaged. In a gridless approach, there is no underlying structure to track such time-averaged macroscopic quantities. We have developed a method of tracking these quantities at the lowest levels of the tree. Using a spherical spline, an estimate of previous time-averaged quantities at a new tree-node location can be found. To validate this method we have performed several benchmark simulations: Couette flow, thermal Couette flow, and two-dimensional flow past an thin plate. The results compare favorably with traditional DSMC. [Preview Abstract] |
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UP1.00042: Sequence of Rotating Plasma Rings Configurations in the Prevalent Gravitational Field of a Central Object B. Coppi, F. Rousseau The search for the axisymmetric equilibrium configurations of thin differentially rotating plasma structures in the prevalent gravitational field of a central object has led to identify a new kind of configuration consisting of a sequence of pairs of plasma rings corresponding to pairs of oppositely directed current channels. The plasma pressure is of the order of the magnetic energy density associated with the currents flowing within the rings, but larger than that of the field in which the rings are immersed. The magnetic configuration has a ``crystal structure'' of the type found first for accretion disks\footnote{B. Coppi, \textit{Phys. of Plasmas} \textbf{12}, 057302 (2005).} with relatively low magnetic energy densities. The ``sequence of plasma rings'' solution\footnote{B. Coppi and F. Rousseau, M.I.T. LNS Report HEP 05/01,(2005).} of the relevant equilibrium equations may in fact be extended to dusty plasmas, and be of interest in planetary physics\footnote{C.K. Goertz and G. Morfill, \textit{Icarus} \textbf{53}, 219 (1983)}. A necessary condition is that the plasma rotation frequency is constant on magnetic surfaces requiring relatively large electrical conductivity. Moreover, accretion structures for which the magnetic configuration has a dominant effect are suitable to represent those from which jets can emerge. Sponsored in part by the U.S. Department of Energy. [Preview Abstract] |
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UP1.00043: The dynamics of electron and ion holes in electron-ion plasmas Bengt Eliasson, Padma Kant Shukla We present analytical and numerical studies of the dynamics of nonrelativistic electron and ion holes in collisionless plasmas. The new results are based on a class of analytic solutions, which work as initial conditions to numerical simulations of the dynamics of ion and electron holes and their interaction with radiation and the background plasma. Our analytic and numerical studies reveal that ion holes can work as s a resonance cavity which can trap Langmuir waves, due the local electron density depletion associated with the negative ion hole potential. Our study of the dynamics between electron holes and the ion background reveals that standing electron holes can be accelerated by the self-created ion cavity owing to the positive electron hole potential. The results of our simulations could be helpful to understand the nonlinear dynamics of electron and ion holes in space and laboratory plasmas. [Preview Abstract] |
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UP1.00044: Simulation of mode competition and start-up in a grounded-cathode Magnetron Katia Gomberoff, Jonathan Wurtele Simulations results of a relativistic magnetron using the MAGIC PIC code are reported. The time evolution of the buildup process for different magnetron azimuthal modes is studied for a variety of initial voltages, with and without a second, oscillatory small voltage in addition to the drive. The self-field is seen to evolve so that the anode-cathode voltage nears the Buneman-Hartree voltage of a particular mode. Simulations show that the output power is larger than in the case where the voltage dynamically approaches the Buneman-Hartree value from above than when it is approached from below. An oscillatory voltage, of relatively small amplitude and possibly chirped in frequency is seen to modify mode competition. Small changes in the azimuthal structure are seen to lead to different mode dynamics; when the $\pi$ mode symmetry is enforced other competing modes are greatly suppressed. [Preview Abstract] |
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UP1.00045: Effects of nonlinear left-hand circularly polarized waves Luis Gomberoff We study the effect of nonlinear left-hand polarized waves supported by a proton beam on the linear circularly polarized instabilities driven by the same beam. We show that the nonlinear wave can either stabilize or destabilize the linear instabilities. The effects depend on the amplitude of the nonlinear wave and on the temperature of the system. We also show that purely electrostatic ion-acoustic like waves, can be destabilized by the large amplitude wave. The latter instabilities do not occur in the absence of the nonlinear waves. [Preview Abstract] |
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UP1.00046: Interaction of a supernova shock with two interstellar clouds J.F. Hansen, A.R. Miles, H.F. Robey, R.I. Klein, C.F. McKee The interaction of supernova shocks and interstellar clouds is an important astrophysical phenomenon since it can result in stellar and planetary formation. Our experiments attempt to simulate this mass-loading as it occurs when a shock passes through interstellar clouds. We drive a strong shock using a 5 kJ laser into a foam-filled cylinder with embedded Al spheres (diameter D=120 $\mu $m) simulating interstellar clouds. The density ratio between Al and foam is $\sim $9. We have previously reported on the interaction between shock and a single cloud, and the ensuing Kelvin-Helmholtz and Widnall instabilities. We now report on experiments under way in which two clouds are placed side by side. Cloud separation (center to center) is either 1.2$\times $D or 1.5$\times $D. Initial results for 1.2$\times $D show that cloud material merges and travels further downstream than in the single cloud case. For 1.5$\times $D, material does not merge, but the clouds tilt toward each other. Work performed under the auspices of the Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48. [Preview Abstract] |
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UP1.00047: Heat and Ash Removal by Curved Liquid Metal Divertor Ahmed Hassanein, Paul Fischer, Isak Konkashbaev Liquid flow divertors are being considered for use in future fusion reactors to remove most candidate fluids and particles (D, T, He, impurities) exiting the tokamak core plasma via the scrape off layer (SOL). Problems of heat removal can be solved, but particle removal remains a problem. The main difficulty is high diffusion rate in fluids thus recycling rate can be very large. Flow in the curved tray of our interest, regarded as a sector of the Couette flow between two rotational cylinders, has been well studied. Vortexes displaced along the flow direction (rotating cells) are called Gortler vortexes. Such curved trays are being theoretically studied at ANL for heat smoothing and removal in targets of high power ($\approx $1 MW) accelerators (e.g., RIA, linear colliders, and SNS). The effects of heat rates and particle transportation on material properties and divertor design (geometry, flow velocity, and depth) were calculated by numerical simulation using the 3D MHD spectral-element code developed at ANL and the University of Chicago for astrophysical purposes. Recommendations for experimental study of liquid metal divertors are given for different candidate materials having very high electrical conductivity (Li) to very low conductivity (Flibe). [Preview Abstract] |
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UP1.00048: High Brightness Accelerator for Warm Dense Matter Studies. Enrique Henestroza, Simon S. Yu, David P. Grote, Richard J. Briggs A high brightness heavy ion accelerator for creating powerful beams to study warm dense matter is being designed at LBNL. The components are an injector that delivers 0.1 $\mu $C of sodium beam, and an accelerator that boosts the energy to about 20 MeV. Further beam manipulations will compress the beam to a final spot radius of 1 mm and a pulse length of 1 ns. In order to reach those final parameters, it is required to extract a high brightness beam and minimize the transverse and longitudinal emittance growth along the accelerator. The injector is based on the Accel-Decel concept which enables the extraction of a high line charge density beam from the ion source, and the accelerator is based on the Pulse Line Ion Accelerator concept, which uses a slow-wave structure based on a helical winding, on which a voltage pulse is launched and propagated to generate the accelerating fields. We will present numerical simulations of the beam dynamics in this system. [Preview Abstract] |
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UP1.00049: Structural phases in complex plasmas Truell Hyde, Bernard Smith, Ke Qiao, Lorin Matthews, Jerry Reay, Mike Cook, Jimmy Schmoke Dust particles imbedded within a plasma will acquire an electric charge from collisions with free electrons in the plasma. If the ratio of the inter-particle potential energy to the average kinetic energy is sufficient, the particles can form either a ``liquid'' structure with short range ordering or a crystalline structure with longer range ordering. With the dust particles residing in two-dimensionally extended lattice planes, different stable crystalline phases have been observed experimentally and energetically favored structures identified employing various DC biases. These experimental results are shown to be in good agreement with theoretical predictions for this strongly coupled complex plasma. They are also shown to be in good agreement with results from experimental observations determining the structural phases of crystallized ion plasmas. [Preview Abstract] |
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UP1.00050: Compression and acceleration of high-energy electron beam by intense short pulse laser Shigeo Kawata, Shuji Miyazaki, Kei Sakai, Shotaro Hasumi, Ryo Sonobe, Qing Kong, Takashi Kikuchi A generation of a high-density electron bunch is investigated. In order to compress a pre-accelerated electron bunch, we employ a laser of a TEM$_{10}$ mode + TEM$_{01}$ mode. This laser has a circle-shaped intensity distribution in transverse, and the pre-accelerated electrons are confined by the transverse ponderomotive force in transverse. A laser longitudinal electric field accelerates the pre-accelerated electrons further in longitudinal$^{[1]}$. At the parameter values of $a_{0}$=10, \textit{$\lambda $}=0.8 \textit{$\mu $m}, $w_{0}$=20\textit{$\lambda $}, $L_{z}$=10\textit{$\lambda $}, and \textit{$\gamma $}$_{i}$=7, the maximum electron energy is about 400 MeV. Here $a_{0}$ is the dimensionless value of the laser amplitude, \textit{$\lambda $} is the laser wavelength, $w_{0}$ is the laser spot size, $L_{z}$ is the pulse length and \textit{$\gamma $}$_{i}$ is the relativistic factor of the pre-accelerated electrons. The electrons accelerated are compressed into a length of about 10\textit{$\lambda $} from the original size of 150\textit{$\lambda $}. Our analytical study also shows that if the laser intensity and pre-accelerated electrons are in relativistic, the electron energy is proportional to $a_{0}$. This scaling law agrees well with the simulation results. [1] S. Miyazaki, S. Kawata, Q. Kong, et al., J. Phys. D: Appl. Phys. 38, pp. 1665-1673 (2005). [Preview Abstract] |
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UP1.00051: Heavy ion beam illumination and implosion simulation in inertial confinement fusion Shigeo Kawata, Tetsuo Someya, Takashi Kikuchi, A.I. Ogoyski In direct-driven pellet implosion, heavy ion beams (HIBs) illuminate a spherical target and deposit their energy on a target after a HIB final transport. In our study, we develop a three-dimensional HIB illumination code [1] and a target hydrodynamic implosion code for heavy ion fusion (HIF). The main objects of our study are to clarify a dependence of multi-HIB illumination non-uniformity on parameter values of HIB illumination in HIF and to calculate the target hydrodynamics during the HIB pulse by using the our HIB illumination and implosion code. In our illumination code, we calculate the HIB energy deposition. The target nuclei, target bound electrons, free electrons and target ions contribute to the HIB energy deposition. The HIB ions impinge the target surface, penetrate relatively deep into the deposition layer and deposit their energy in a rather wide region in the deposition layer: this HIB deposition feature influences the beam illumination non-uniformity. Therefore we calculate target implosion using the coupled hydrodynamic code in order to investigate the beam illumination non-uniformity influence on a fuel ignition. [1] T.Someya, et.al, Phy.Rev.STAB, 7, 044701 (2004). [Preview Abstract] |
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UP1.00052: Radiation Transport Through Inhomogenous Materials Paul Keiter, Mark Gunderson, John Foster, Paula Rosen, Mark Taylor Calculations of radiation transport in heated materials are greatly complicated by the presence of regions in which two or more materials are inhomogeneously mixed. We describe laboratory experiments to test modeling of radiation transport through inhomogeneous plasmas. A laser-heated hohlraum is used as a thermal source to drive radiation through a polymer foam containing randomly-distributed gold particles. We present experimental measurements of the radiation transport through different foam/gold particle mixtures. Simulation results will also be compared to the experimental results. [Preview Abstract] |
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UP1.00053: Compression of Plasmas: shocks and stuff Giovanni Lapenta, Joshua King, Gian Luca Delzanno A common occurrence in plasmas is local compression. We revisit the issue by asking the question: how is compressing a plasma different from compressing a gas? Compressing an ideal gas is hardly a new topic in physics. Indeed our modern industrial civilization was spurred by the first experiments on gas and steam compression. Still the issue is worth revisiting in the light of how different it is when magnetization effects are included. When a gas is compressed, the classic Riemann problem needs to be solved. The same is true in plasma physics, but is rarely done. Often one neglects the effects of shocks. We investigate the issue on 3 levels. First, we consider a gas dynamics model based on Euler’s equations. Second, we consider the same approach including the effect of B (MHD shocks). Finally, we consider the kinetic answer for a collisionless system, focusing primarily on the role of the pressure tensor anisotropy. [Preview Abstract] |
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UP1.00054: Development of a 1 mm Collective Scattering System for NSTX L. Lin, C.W. Domier, M. Johnson, N.C. Luhmann, Jr., R.E. Feder, E. Mazzucato, H. Park, D.R. Smith A millimeter-wave collective scattering system has been developed to investigate high-k density fluctuations in the core of NSTX plasmas. The key physics issues to be addressed lie in the detection of ETG turbulence and the study of electron thermal transport. Operating at 280 GHz (1.1 mm), the five channel receiver samples radial density fluctuations with wavenumbers k$_{r}<$20 cm$^{-1}$. System details regarding the source and superheterodyne receiver electronics, and active and passive laboratory measurement data taken prior to installation on NSTX, will be presented. [Preview Abstract] |
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UP1.00055: Divinylbenzene Foam Films Katharine Nelson, Sue Carter, Joe Florio, Josh Gregory, Jim Heuer, Ed Hsieh, Derrick Mathews, Brian Motta, Nicole Petta, Keith Shillito Divinylbenzene (DVB) foam is a common material used for ICF targets. It is formed by the crosslinking radical reaction of DVB while in a solvent and then dried in a supercritical fluid. When it is cast on most substrates, the flat film is difficult to release. Coated mold release agents are unacceptable because they will contaminate the foam. At Schafer Laboratories, a method has been developed to chemically modify a glass substrate with a monolayer of a silane coupling reagent that creates a substrate that the foam will not stick to. This provides superior results and the ability to make flat DVB films easily that are large enough to make targets out of. This work is supported under DOE DE-AC03-01F22260. [Preview Abstract] |
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UP1.00056: Equilibrium and stability in the transport of off-axis beams in magnetic focusing systems Renato Pakter, Felipe Rizzato, Jorge Moraes, Karen Fiuza A general equation for the centroid motion of free, continuous, intense beams propagating off-axis in solenoidal periodic focusing fields is derived [J.S. Moraes, R. Pakter, and F.B. Rizzato, Phys. Rev. Lett., {\bf 93}, 244801 (2004)]. The centroid equation is found to be independent of the specific beam distribution and may exhibit unstable solutions. A new Vlasov equilibrium for off-axis beam propagation is also obtained. Properties of the equilibrium and the relevance of centroid motion to beam confinement are discussed. The effects of a conducting pipe encapsulating the beam are also investigated [J.S. Moraes, R. Pakter, and F.B. Rizzato, Phys. Plasmas, {\bf 12}, 023104 (2005)]. It is shown that the charge induced at the pipe may generate chaotic orbits. [Preview Abstract] |
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UP1.00057: Recent Developments in ICF Target Support Nicole Petta, Sue Carter, Joe Florio, Josh Gregory, Jim Heuer, Ed Hsieh, Derrick Mathews, Brian Motta, Katharine Nelson, Keith Shillito This paper summarizes recent advancements in coatings, foam target chemistry and assembly techniques at Schafer Laboratories. Characterization techniques are also discussed with emphasis on new confocal imagery and a multi axis assembly station. Machined sine waves, improved surface finishes and gas bag developments are addressed. This work is supported under DOE DE-AC03-01F22260. [Preview Abstract] |
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UP1.00058: Relativistic shock surfing acceleration of ions at the oblique shock Vitali Shapiro, Defne Ucer It was shown in Lee et al (1996) that one of the important limitation for shock surfing acceleration of ions at the quasiperpendicular shock is due to the obliqueness of the shock wave. In this paper a critical obliqueness for the relativistic shock wave is found below which the energy gain by surfing acceleration is not limited by shock obliqueness. Lee et al., J. of Geophys. Res. 101,4777, 1996 [Preview Abstract] |
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