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 YP8: Poster Session IX: Supplemental and Postdeadline Posters |
Hide Abstracts |
Room: Preservation Hall |
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YP8.00001: SUPPLEMENTAL |
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YP8.00002: The evolution of the Rayleigh-Taylor and Richtmyer-Meshkov instabilities in a finite height domain Snezhana I. Abarzhi We apply group theory analysis to systematically study the nonlinear evolution of the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities in a domain of a finite height. The fluids with similar and contrasting densities are considered in case of two-dimensional RT and RM instabilities that are driven by sustained and impulsive accelerations respectively. The flow is periodic normal to the acceleration direction and has no external sources. For the nonlinear boundary value problem a family of asymptotic solutions is found, and the properties of the family solutions as well as their stability are thoroughly analyzed. For the first time the relation is identified between the family parameter (e.g. the front curvature) and the velocity shear at the front. The growth-rate of shear-driven Kelvin-Helmholtz instability is evaluated. It is shown in the nonlinear RT and RM flows in finite height domain there is an intense motion in a vicinity of the front and there is effectively no motion away from the front. In a finite size the domain the flow is decelerating in comparison to the spatially extended case. The theory outcomes for the numerical modeling of the RT and RM instabilities and for the design of experiments are discussed. [Preview Abstract] |
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YP8.00003: The scientific prototype, the only reasonable next step for the American MFE program; or why FESAC will never solicit my advice again Wallace Manheimer The scientific prototype [1] is a tokamak which builds on what has been accomplished in TFTR, JET and JT-60. Instead of attempting to advance the plasma parameters, or investigate a new confinement configuration, it takes the tokamak plasma parameters already achieved (or actually nearly already achieved), Q about 1 and run it at steady state or high duty cycle in a DT plasma. It is very much a nuclear device requiring all of the safeguards of any nuclear device. It is an important step forward for either pure fusion or fusion breeding, and it is difficult to see how fusion can advance very far with out the knowledge the scientific prototype would provide. The poster will be divided into two parts. The first part examines options other than the scientific prototype and shows why they should be rejected. The second part explains the scientific prototype in somewhat more detail.\\[4pt] [1] W. Manheimer, J. Fusion Energy, 32, 419, (2013) [Preview Abstract] |
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YP8.00004: Purely-growing fast reconnection from a fourth-order fluid equation Paul Bellan If either finite electron inertia or finite resistivity are included in 2D magnetic reconnection, the two-fluid equations become a pair of second-order differential equations coupling the out-of-plane magnetic field and vector potential to each other to form a fourth-order system. The coupling at an X-point is such that out-of-plane even-parity electric and odd-parity magnetic fields feed off each other to produce instability. The instability growth rate is given by an eigenvalue of the fourth-order system determined by boundary and symmetry conditions. The instability is a purely growing mode, not a wave, but has growth rate of the order of the whistler frequency. The spatial profile of both the out-of-plane electric and magnetic eigenfunctions consists of an inner concave region having extent of the order of the electron skin depth, an intermediate convex region having extent of the order of the ion skin depth, and a concave outer exponentially decaying region. If finite electron inertia and resistivity are not included, the inner concave region does not exist and the coupled pair of equations reduces to a second-order differential equation having non-physical solutions at an X-point. [Preview Abstract] |
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YP8.00005: Effect of parallel heat flux in the gyroviscous tensor on tearing mode instability in two-fluid magnetohydrodynamic model Atsushi Ito, J.J. Ramos Two-fluid magnetohydrodynamic (MHD) models with ion gyroviscous tensor are used to study finite Larmor radius effects on MHD instabilities such as the tearing mode instability. However, the conventional two-fluid models are valid for collisional plasmas. In the fluid moment equations for low collisionality plasmas, the parallel heat flux that arises in the gyroviscous force due to the non-Maxwellian part of the velocity distribution function cannot be neglected [1]. The effect of parallel heat flux in the gyroviscous tensor on the tearing mode instability in low collisionality plasmas is investigated by eigenmode analysis. The linear eigenmode equations for the tearing mode instability including the perturbed parallel heat flux in the gyroviscous tensor are derived from the fluid moment equations and are numerically solved. [Preview Abstract] |
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YP8.00006: Preliminary Results for Coded Aperture Plasma Diagnostic Magnus Haw, Paul Bellan A 1D coded aperture camera has been developed as a prototype for a high speed, wavelength-independent, plasma imaging diagnostic. Images are obtained via a coded or masked aperture that modulates incoming light to produce an invertible linear transform of the image on a detector. The system requires no lenses or mirrors and can be thought of as a multiplexed pinhole camera (with comparable resolution and greater signal than a single pinhole). The inexpensive custom-built system has a 13x1cm field of view, a vertical spatial resolution of 2mm, and a temporal resolution of 1$\mu$s. Visible light images of the Caltech MHD-driven jet experiment agree with simultaneous images obtained with a conventional camera. For the simple jet geometry, the system can also extract depth information from single images. Further work will revolve around improving shielding and acquiring X-ray and EUV scintillators for imaging in those wavelengths. [Preview Abstract] |
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YP8.00007: Robustness of the filamentation instability in arbitrarily oriented magnetic field Antoine Bret The filamentation (Weibel) instability plays a key role in the formation of collisionless shocks which are thought to produce Gamma-Ray-Bursts and High-Energy-Cosmic-Rays in astrophysical environments. While it has been known for long that a flow-aligned magnetic field can completely quench the instability, it was recently proved in 2D that in the cold regime, such cancelation is possible if and only if the field is perfectly aligned. Here, this result is finally extended to a 3D geometry. Calculations are conducted for symmetric and asymmetric counter-streaming relativistic plasma shells. 2D results are retrieved in 3D: the instability can never be completely canceled for an oblique magnetic field. In addition, the maximum growth-rate is always larger for wave vectors lying in the plan defined by the flow and the oblique field. On the one hand, this bears consequences on the orientation of the generated filaments. On the other hand, it certifies 2D simulations of the problem can be performed without missing the most unstable filamentation modes [1].\\[4pt] [1] Bret, PHYSICS OF PLASMAS 21, 022106 (2014) [Preview Abstract] |
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YP8.00008: Comparison of the spherical and ellipsoidal bubble models in laser wakefield accelerator MyungHoon Cho, YoungKuk Kim, MinSub Hur The bubble in the laser wakefield electron accelerator generally takes an ellipsoidal shape. However, the electron trapping condition in such a general shape has not been fully investigated yet. In this presentation, we describe our improved theory of electron trapping in an ellipsoidal bubble; especially we focus on the trapping condition for a transversely elongated one, which is not well explained by the spherical bubble model. First we introduce and compare the spherical and ellipsoidal bubble formation derived from Maxwell's equation. Specifically we introduce the relation between the bubble size and the field slope in longitudinal and transverse directions. Then we investigate the electron trapping condition by numerically integrating the equations of motion. From a series of numerical calculations, we found that the trapping is dominantly determined by the transverse bubble size, which makes the trapping condition much less restrictive than in the completely spherical bubble. To confirm our theoretical prediction, we carried out 3D PIC simulations, which exhibited good agreement with the theory. [Preview Abstract] |
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YP8.00009: Characterization of the Inductively Heated Plasma Source IPG6-B Michael Dropmann, Rene Laufer, Georg Herdrich, Lorin Matthews, Truell Hyde In close collaboration between the Center for Astrophysics, Space Physics and Engineering Research (CASPER) at Baylor University, Texas, and the Institute of Space Systems (IRS) at the University of Stuttgart, Germany, two plasma facilities have been established using the Inductively heated Plasma Generator 6 (IPG6). The facility at Baylor University (IPG6-B) works at a frequency of 13.56 MHz and a maximum power of 15 kW. A vacuum pump of 160m$^{\mathrm{3}}$/h in combination with a butterfly valve allows pressure control over a wide range. Intended fields of research include basic investigation into thermo-chemistry and plasma radiation, space plasma environments and high heat fluxes e.g. those found in fusion devices or during atmospheric re-entry of spacecraft. After moving the IPG6-B facility to the Baylor Research and Innovation Collaborative (BRIC) it was placed back into operation during the summer of 2014. Initial characterization in the new lab, using a heat flux probe, Pitot probe and cavity calorimeter, has been conducted for Air, Argon and Helium. The results of this characterization are presented. [Preview Abstract] |
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YP8.00010: Anisotropic Radiation Transport Experiments on the OMEGA Laser Jonathan Hager, Nick Lanier, John Kline, Kirk Flippo, Jonathan Workman, H.C. Bruns, M. Schneider, M. Saculla, T. McCarville A new experimental platform is being developed at the OMEGA laser to generate an anisotropic radiation source to provide data that will challenge our implementation of Implicit Monte Carlo (IMC) radiation transport models. A low density silica aerogel foam physics package is mounted to a laser driven half-hohlraum. The x-ray drive from the hohlraum is modified by a filter and aperture to decrease the optical thickness of the foam and increase the source anisotropy, respectively. Point projection backlighting is used to measure the hydrodynamic response to the Marshak wave once it goes subsonic. The temperature of the driven foam can also be inferred using absorption spectroscopy when a titanium dopant is introduced. Experimental results using a Ti doped foam will be presented with analytic calculations and 2-D radiation hydrodynamic simulations demonstrating the impact of the source anisotropy on the measurable parameters in the foam. [Preview Abstract] |
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YP8.00011: Extension of GTC Capability for Simulating Non-Axisymmetric Systems Ihor Holod, Donald Spong Effects of magnetic field non-axisymmetry are important for all magnetic confinement systems, including tokamaks, stellarators, and reversed field pinches. In this work we present recent upgrade of GTC global gyrokinetic model to use general 3D toroidal equilibria and to study the associated phenomena. We have initially applied new capability to simulate electrostatic ITG, and fast ion driven electromagnetic TAE modes in the LHD stellarator. [Preview Abstract] |
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YP8.00012: Characteristic of Terahertz Radiation from a Counter-Pulse Scheme in a Magnetized Plasma Min Sup Hur, Myung-Hoon Cho, Young-Kuk Kim We studied a novel scheme of generating a quasi-continuous terahertz radiation from counter-propagating laser pulses colliding in a magnetized plasma. In this system, the strong ponderomotive force of colliding pulses leaves a standing oscillation of an electron current around the collision point, which acts as an antenna of the electromagnetic radiation in the terahertz frequency regime. Theoretically it was found that the terahertz amplitude scales with square of P, where P is the power of the driving pulse, while it scales just with P for a single pulse case. So the radiation intensity can be enhanced by tens of times from that of Cherenkov wake scheme driven by a single laser pulse. Furthermore it was found that, due to the growth of the central field, which is a direct result of driven-diffusion of the electric field near the cutoff, the density gradient of the plasma even increases the peak power of the terahertz radiation. [Preview Abstract] |
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YP8.00013: Characterizing Hot Electron Generation and Transport via Bremsstrahlung Emission on the High Intensity OMEGA EP Laser J. Peebles, C. McGuffey, C. Krauland, A. Sorokovikova, B. Qiao, S. Krasheninnikov, F.N. Beg, M.S. Wei, R.B. Stephens, C.D. Chen, B. Westover, H.S. McLean The investigation of high intensity laser generated fast electron beams is important for a number of High Energy Density Science applications, which include proton sources and fast ignition among others. A series of experimental campaigns performed using the kilojoule, 10-ps OMEGA EP laser closely examined the impact of a preformed plasma on laser plasma interaction and electron generation. Here we present the analysis of the measured bremsstrahlung x-ray radiation and the inferred results on fast electron characteristics. Simulations, performed with the Monte-Carlo code package ITS 3.0, generate the x-ray response of the target to an injected electron beam with a given temperature, energy and divergence angle. The simulated x-rays are then compared to those collected by the bremsstrahlung spectrometers, which allows us to characterize fast electrons created in the experiment. Preliminary results show a decrease in hot electron temperature with an increase in pre-pulse, which is further corroborated by magnetic electron and Cu-K$\alpha $ spectrometers. This work performed under the auspices of the US DOE under contracts DE-FOA-0000583 (FES, NNSA), DE-NA0002026 (NLUF) and DE-FC02-04ER54789 (FSC). [Preview Abstract] |
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YP8.00014: Analysis and simulation of double tearing modes Y. Nishimura, J.M. Chen, C.Z. Cheng Tokamak experiments with non-monotonic q-profile have attracted attention to the stability problem of double tearing modes. Interestingly, double tearing modes are one of the good examples where the pressure anisotropy effects become prominent. The bootstrap current contribution on the $\Delta '$ depends on the sign of $(dp/dr)/s$ ($s$ is the magnetic shear, $(dp/dr)$ is the pressure gradient), which is different on the inner surface and the outer surface, The $\Delta '$ matrix, including off diagonal elements are calculated by solving exterior equation.\footnote{Y. Nishimura, J.D. Callen, and C.C. Hegna, Phys. Plasmas {\bf 5}, 4292 (1998).} The analysis is compare with the numerical results from a three dimensional initial value simulation. The nonlinear evolution of toroidally asymmetric $m/n=2/1$ island chains has been investigated. To incorporate the pressure anisotropy, the kinetic-fluid model is employed\footnote{ C.Z. Cheng and J.R. Johnson, J. Geophysical Res.{\bf 104}, 413 (1999); Y. Nishimura and C.Z. Cheng, J. Plasma and Fusion Res. Series {\bf 9}, 452 (2010).} which replace the pressure evolution equation with the second order moment of the kinetic ions and electrons from kinetic (particle) simulation. [Preview Abstract] |
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YP8.00015: Nonlinear kinetic modeling of stimulated Raman scattering in a non-uniform and non-stationary plasma Didier Benisti We provide a theoretical description of stimulated Raman scattering that allows for collisionless dissipation as described in [1] (and, in particular, of the nonlinear reduction of the Landau damping rate), and that accounts for the nonlinear frequency shift of the plasma wave and for the growth of sidebands. Non-uniform and non-stationary effects are derived by making use of a variational principle. The central direction of propagation of the pump laser is calculated with the usual ray-tracing method. However, non-paraxial equations are used for the plasma and scattered waves in order to account for the self-focusing induced by the nonlinear frequency shift.\\[4pt] [1] D. B\'{e}nisti, O. Morice and L. Gremillet, Phys. Plasmas \textbf{19}, 063110 (2012). [Preview Abstract] |
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YP8.00016: Current Profile Control in DIII-D E.M. Schuster, J.E. Barton, M.D. Boyer, W.P. Wehner, J.R. Ferron, D.A. Humphreys, A.W. Hyatt, G.L. Jackson, T.C. Luce, M.L. Walker Experimental results successfully demonstrate the potential of physics-model-based control for systematic attainment of desired q profiles, with the subsequent benefit of enabling exploration and reproducibility. The control scheme is constructed by embedding a nonlinear, control-oriented, physics-based model of the plasma dynamics into the control design process. This modeling approach combines first-principles laws with empirical correlations obtained from physical observations, which leads to PDE models capturing the high-dimensionality and nonlinearity of the plasma response. Model-based control design includes not only the synthesis of feedback controllers for robust regulation or tracking, but also the determination of optimal feedforward actuator trajectories for a systematic approach to scenario planning. Feedforward+feedback (closed loop) control experiments in DIII-D consistently demonstrate improved current-profile control performance relative to feedforward (open loop) control alone. [Preview Abstract] |
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YP8.00017: MHD modes rotation and locking threshold studies in ITER-like plasmas Vadim Yanovskiy, Paolo Zanca, Roberto Paccagnella The non-linear dynamics of rotating tearing modes electromagnetically interacting with conducting shell is simulated for the parameters expected in ITER and their locking thresholds are calculated. The work is motivated by the fact that the relatively slow mode rotation during disruptions is considered to be particularly dangerous in ITER for its possible large detrimental effect through the excitation of a resonant response of the mechanical structures. The study is based on a simple cylindrical model for the evolution of the rotating MHD modes determined by the Rutherford equation, their coupling to the plasma flow and to the resistive wall. The modelling reveals the conditions under which the modes are likely to rotate or to lock during disruptions events. In addition, the comparison with the results obtained in nonlinear 3D plasma simulations is performed. [Preview Abstract] |
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YP8.00018: Ferromagnetic effect on the rotational stabilization of the resistive wall modes in tokamaks Vadim Yanovskiy, Vladimir Pustovitov The plasma stability in tokamaks with a ferromagnetic wall is analyzed because the presence of ferritic materials is expected in the ITER test blanket modules, and experiments with such elements are planned on the JT-60SA tokamak. The study is based on the dispersion relation for ferromagnetic resistive wall modes (RWMs) obtained in the cylindrical approximation by coupling the solution in the external region with arbitrary plasma model assuming only linearity of the plasma response to external perturbations. In contrast to the traditional thin wall approach to RWMs, the wall is treated as magnetically thick. We show that the rotational stabilization of RWMs, which in our model is similar to that observed in DIII-D and other tokamaks [M. S. Chu and M. Okabayashi, Plasma Phys. Control. Fusion \textbf{52}, 123001 (2010)] allowing the plasma operation above the no-wall stability limit, becomes stronger in the presence of ferromagnetic wall compared to the case of non-ferritic wall, and is possible even at lower rotation frequency, estimated as several kHz at realistic conditions. Simple analytical formulas describing the effect as well as their applicability ranges are presented. [Preview Abstract] |
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YP8.00019: Simulation of EGAM with GTS Ge Wang, Guoyong Fu, Weixing Wang Energetic particle induced geodesic acoustic mode is studied using the gyro-kinetic code GTS, where the electrons, ions and energetic particles are treated as fully kinetic species. The unstable EGAM is growing up when the beta of energetic particles increases up to the threshold. The eigen-frequency and growth rate of EGAM mode are benchmarked with the NEMROBE using the doubly bumped distribution function of the energetic particles. The frequency of the nonlinear EGAM is observed to chirp during the marginal instability of the EGAM. The EGAM plays a role in the ITG turbulence and therefore it will influence the transport of energetic particles in tokamak. We will discuss our results on this issue. [Preview Abstract] |
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YP8.00020: Introduction to the Neutrosophic Quantum Theory Florentin Smarandache Neutrosophic Quantum Theory (NQT) is the study of the principle that certain physical quantities can assume neutrosophic values, instead of discrete values as in quantum theory. These quantities are thus neutrosophically quantized. A \textit{neutrosophic values} (\textit{neutrosophic amount}) is expressed by a set (mostly an interval) that approximates (or includes) a discrete value. An oscillator can lose or gain energy by some neutrosophic amount (we mean neither continuously nor discretely, but as a series of integral sets: \textit{S, 2S, 3S, \textellipsis ,} where $S$ is a set). In the most general form, one has an \textit{ensemble of sets of sets}, i.e. $R_{1}S_{1}, R_{2}S_{2}, R_{3}S_{3}$\textit{, \textellipsis ,} where all $R_{n}$ and $S_{n} $are sets that may vary in function of time and of other parameters. Several such sets may be equal, or may be reduced to points, or may be empty. \textbraceleft The multiplication of two sets $A$ and $B$ is classically defined as: \textit{AB }$=$\textit{ \textbraceleft ab, a??A and b??B\textbraceright }. And similarly a number $n$ times a set $A$ is defined as: \textit{nA }$=$\textit{ \textbraceleft na, a??A}\textbraceright . \textbraceright The \textit{unit of neutrosophic energy} is $H\nu $, where $H$ is a set (in particular an interval) that includes Planck constant $h$, and $\nu $ is the frequency. Therefore, an oscillator could change its energy by a \textit{neutrosophic number of quanta}: $H\nu $, \textit{2H}$\nu $, \textit{3H}$\nu $, etc. For example, when $H$ is an interval$ [h_{1}, h_{2}]$, with \textit{0 }$\le h_{1} \le h_{2}$, that contains Planck constant $h$, then one has: $[h_{1}\nu , h_{2}\nu $\textit{], [2h}$_{1}\nu $\textit{, 2h}$_{2}\nu $\textit{], [3h}$_{1}\nu $\textit{, 3h}$_{2}\nu $\textit{],\textellipsis ,} as series of intervals of energy change of the oscillator. The most general form of the units of neutrosophic energy is $H_{n}\nu _{n}$, where all$ H_{n}$ and $\nu_{n}$ are sets that similarly as above may vary in function of time and of other oscillator and environment parameters. Neutrosophic quantum theory combines classical mechanics and quantum mechanics. [Preview Abstract] |
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YP8.00021: Lifting the Vlasov-Maxwell bracket by Lie-transform methods A.J. Brizard, P.J. Morrison, M. Vittot, L. de Guillebon The Vlasov-Maxwell equations possess a Hamiltonian structure expressed in terms of a Hamiltonian functional and a functional bracket [1]. In the present work, the transformation (``lift'') of the Vlasov-Maxwell bracket induced by the dynamical reduction of single-particle particle dynamics is investigated when the reduction is carried out by Lie-transform perturbation methods. A formal proof of the Jacobi identity for the reduced Vlasov-Maxwell bracket is presented. The ultimate goal of this work is to derive explicit Hamiltonian formulations for the guiding-center and gyrokinetic Vlasov-Maxwell equations that have important applications in our understanding of turbulent magnetized plasmas. A comparison with a bracket structure [2] for the gyrokinetic Vlasov-Poisson equations derived by Dirac-constraint method will be presented. \\[4pt] [1] See P.J. Morrison, RMP {\bf 70} 467 (1998) and references therein.\\[0pt] [2] J. Squire, H. Qin, W.M. Tang, and C. Chandre, PoP {\bf 20}, 022501 (2013). [Preview Abstract] |
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YP8.00022: POSTDEADLINE |
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YP8.00023: Wavelength Dependence of UV Effect on Etch Rate and Noise in CR-39 Micah Wiesner, Nathan Traynor, James McLean, Stephen Padalino, Craig Sangster, Michelle McCluskey The use of CR-39 plastic as a SSNTD is an effective technique for recovering data in high-energy particle experiments including inertial confinement fusion. To reveal particle tracks after irradiation, CR-39 is chemically etched at elevated temperatures with NaOH, producing signal pits at the nuclear track sites that are measurable by an optical microscope. CR-39 pieces also exhibit etch-induced noise, either surface roughness or pit-like features not caused by nuclear particles, which negatively affects the ability of observers to distinguish actual pits. When CR-39 is exposed to high intensity UV light after nuclear irradiation and before etching, an increase in etch rates and pit diameters is observed. UV exposure can also increase noise, which in the extreme can distort the shapes of particle pits. Analyzing the effects of different wavelengths in the UV spectrum we have determined that light of the wavelength 255 nm increases etch rates and pit diameters while causing less background noise than longer UV wavelengths. Preliminary research indicates that heating CR-39 to elevated temperatures ($\sim$ 80 $^{\circ}$C) during UV exposure also improves the signal-to-noise ratio for this process. [Preview Abstract] |
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YP8.00024: ABSTRACT WITHDRAWN |
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YP8.00025: An Electromagnetic Gauge Technique for Measuring Shocked Particle Velocity in Electrically Conductive Samples David Cheng, Akio Yoshinaka Electromagnetic velocity (EMV) gauges are a class of film gauges which permit the direct in-situ measurement of shocked material flow velocity. The active sensing element, typically a metallic foil, requires exposure to a known external magnetic field in order to produce motional electromotive force (emf). Due to signal distortion caused by mutual inductance between sample and EMV gauge, this technique is typically limited to shock waves in non-conductive materials. In conductive samples, motional emf generated in the EMV gauge has to be extracted from the measured signal which results from the combined effects of both motional emf and voltage changes from induced currents. An electromagnetic technique is presented which analytically models the dynamics of induced current between a copper disk moving as a rigid body with constant 1D translational velocity toward an EMV gauge, where both disk and gauge are exposed to a uniform external static magnetic field. The disk is modelled as a magnetic dipole loop where its Foucault current is evaluated from the characteristics of the fields, whereas the EMV gauge is modelled as a circuit loop immersed in the field of the magnetic dipole loop, the intensity of which is calculated as a function of space and, implicitly, time. Equations of mutual induction are derived and the current induced in the EMV gauge loop is solved, allowing discrimination of the motional emf. Numerical analysis is provided for the step response of the induced EMV gauge current with respect to the Foucault current in the moving copper sample. [Preview Abstract] |
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YP8.00026: Progress Towards a Microtrap Array for Positron Storage Alireza Narimannezhad, Marc H. Weber, Joshah Jennings, Chandrasekar Minnal, Kelvin G. Lynn The storage of positrons has been a key for antimatter research and applications. One important goal is the attempt to reach higher densities of confined antimatter particles. Progress in this area is explored through a novel microtrap array with large length to radius aspect ratios and radii of the order of tens of microns. The proposed design consists of microtraps with substantially lower barrier potentials than conventional Penning-Malmberg traps arranged in parallel within a single magnet. Simulations showed positron plasma with 1E10 cm$^{-3}$ density evolves toward a rigid-rotation phase in each microtrap while 10 V barriers confined the plasma axially. A trap of 4 cm length including more than 20,000 microtubes with 50 micron radii was fabricated and tested. Experiments conducted with electrons in a test structure addressing each microtube with a narrow beam will be described. This will explore the basic physics of the microtraps. Observed results were promising and they open a new avenue for manipulating high-density non-neutral plasmas. [Preview Abstract] |
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YP8.00027: A Complementary Type of Electrochromic Device by Radio Frequency Magnetron Sputtering System Lutfi Oksuz, Melek Kiristi, Ferhat Bozduman, Aysegul Uygun Oksuz Electrochromic (EC) devices can change their optical properties reversibly in the visible region (400-800 nm) upon charge insertion/extraction reactions according to the applied voltage. A complementary type of EC device composes of two electrochromic layers, which is separated by an ionic conduction layer (electrolyte). In this work, the EC device was fabricated using vanadium oxide (V2O5) and titanium doped tungsten oxide (WO3-TiO2) electrodes. The EC electrodes were deposited as thin film structures by a reactive RF magnetron sputtering system in a medium of gas mixture of argon and oxygen. surface morphology of the films was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Electrochemical property and durability of the EC device was investigated by a potentiostat system. Optical measurement was examined under applied voltages of $\pm$ 2.5 V by a computer-controlled system, constantly. [Preview Abstract] |
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YP8.00028: High Current Electron Beam Emission Driven by a Nonlinear Transmission Line David French, Brad Hoff, Susan Heidger Simulations of an electron beam diode driven by a modulated voltage pulse provided by a nonlinear transmission line (NLTL) will be presented. Based on a previous low voltage experiment [1] the new design operates at 250 kV and provides a multi-kA modulated electron beam based on the modulated drive signal from a ferrite based NLTL. The NLTL driver has been demonstrated experimentally and is tunable from 900-1400 MHz with pulse durations from 4-17 ns. Particle-In-Cell simulations in ICEPIC show the modulated voltage signal results in a modulated electron beam current emitted directly from the cathode in a few cm annular beam. Expected results and the experimental design for the electron beam diode and diagnostics will also be presented. \\[4pt] [1] D. M. French, B. W. Hoff, W. Tang, S. Heidger, J. Allen-Flowers, D. Shiffler, ``Nonlinear Transmission Line Based Electron Beam Driver,'' Rev. Sci. Instrum. 83, 123302 (2012). [Preview Abstract] |
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YP8.00029: High-Speed Particle-in-Cell Simulation Parallelized with Graphic Processing Units for Low Temperature Plasmas for Material Processing Min Young Hur, John Verboncoeur, Hae June Lee Particle-in-cell (PIC) simulations have high fidelity in the plasma device requiring transient kinetic modeling compared with fluid simulations. It uses less approximation on the plasma kinetics but requires many particles and grids to observe the semantic results. It means that the simulation spends lots of simulation time in proportion to the number of particles. Therefore, PIC simulation needs high performance computing. In this research, a graphic processing unit (GPU) is adopted for high performance computing of PIC simulation for low temperature discharge plasmas. GPUs have many-core processors and high memory bandwidth compared with a central processing unit (CPU). NVIDIA GeForce GPUs were used for the test with hundreds of cores which show cost-effective performance. PIC code algorithm is divided into two modules which are a field solver and a particle mover. The particle mover module is divided into four routines which are named move, boundary, Monte Carlo collision (MCC), and deposit. Overall, the GPU code solves particle motions as well as electrostatic potential in two-dimensional geometry almost 30 times faster than a single CPU code. [Preview Abstract] |
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YP8.00030: Discontinuous Galerkin modeling of Scrape-Off Layer Turbulence Tess Bernard, Fran\c{c}ois Waelbroeck, Craig Michoski Turbulence plays an important role in determining the transport and heating of space, astrophysical, and laboratory plasmas. Modeling this turbulence is particularly challenging because of the ability of the plasma to support waves with disparate space-time scales as well as to generate both short and long wavelength through nonlinear processes. Using a discontinuous Galerkin code called ArcOn, turbulence in the Texas Helimak is modeled. The Helimak experiment at the University of Texas aims to model the conditions in the scrape-off layer (SOL) of fusion devices. Effective modeling of this region is very important because much of the thermal power in fusion devices flows through it to divertor plates that must survive the resulting erosion and redeposition. It has been shown that electric biasing in this region can be used to reduce and control turbulence. The Arcon code is used to simulate such potential biasing, with the goal of improving the theoretical understanding of this phenomena and its role in other fusion devices, in addition to the Helimak. [Preview Abstract] |
(Author Not Attending)
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YP8.00031: Simplex-In-Cell Method for Kinetic Plasma Simulation Samuel Totorica, Julian Kates-Harbeck, Jonathan Zrake, Tom Abel We present a new particle-based method for kinetic plasma simulation that interprets the simulation particles as tracers of the distribution function in phase space. The construction of a piecewise linear approximation to the distribution function is enabled by interpolation of the tracer particles. With access to the full distribution function, moments such as density and velocity dispersion are defined continuously over the spatial domain. Charge and current densities obtained in this way are utilized in an improved particle-mesh force calculation, reducing particle discretization noise and more accurately modeling the continuum limit. The new method is implemented for 1D2V and compared with a cloud-in-cell deposit for electrostatic and electromagnetic test problems. Significant computational savings are shown when using the new method to model linear evolution. To simulate into the nonlinear regime we implement adaptive refinement of the mesh defined by the tracer particles, capturing the fine detail in the distribution function. These ideas may also be used as a post processing tool for standard PIC simulations, where the continuous density and velocity fields obtained eliminate the necessity of averaging over control volumes and associated statistical noise. [Preview Abstract] |
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YP8.00032: Assessing the Plasma-Liquid Interface Using Single Bubble Studies John Foster, Athena Sagadevan, Sarah Gucker Interaction physics and chemistry between a plasma in contact with liquid water occurs at the interface. Energy transport as well as radical species production occurs in this region. An understanding of the physical processes occurring in this region is key to elucidating the effect that plasma has on water chemistry well beyond the interface. Such an understanding has implications in application areas such as plasma medicine and water purification. Here, we present preliminary results from a 2-D system aimed at elucidating the plasma-liquid interface through the study of the interfacial response under the influence of plasma produced in a single, trapped bubble. The spatial extent and associated reactivity of this active layer associated with the interface region is interrogated with chemical probes and optical imaging. Results from these studies are presented. [Preview Abstract] |
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YP8.00033: ``Debussy'' Orion campaign for assessing target shrapnel originating from laser experiments Didier Raffestin, Jean-Paul Jadaud, Jim Andrew, Mike Rubery, Laurent Videau, Patrick Combis, Jean-Marc Chevalier, Alain Galtie, Jean-Hugues Quessada, Alain Geille During plasma experiments on high energy laser facilities, debris and fragments originating from the target can result in significant damage to optics and/or equipment. In the scope of future experiments on the LMJ, it is thus necessary to develop an accurate predictive tool for assessing the speed, mass, state and direction of ejected material. In this context, a 28 shot campaign was performed in June 2014 on the Orion facility in collaboration with AWE. The first part was dedicated to the characterization of debris and shrapnel emitted from halfraum or cylinders using PDV laser velocimetry and passive collectors (aluminium and plastic sleeves, varagel and aerogel). The second part aimed at collecting basic data on fragmentation of samples (steel, Ta, Ti, Al, PMMA, SiO$_{2})$ irradiated by x-rays using PDV measurement. Some preliminary data and observations will be presented and compared to simulations (CEA Esther code). [Preview Abstract] |
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YP8.00034: Nonlinear Optical Interactions in Plasmas at JILA F. Dollar, D.D. Hickstein, D. Popmintchev, A. Becker, J. Ellis, C. Hernandez-Garcia, A. Jaron-Becker, T. Popmintchev, W. Xiong, M.M. Murnane, H.C. Kapteyn, G. Dukovic, J. Jimenez, B. Palm, K. Schnitzenbaumer, J. Perez-Hernandez, A. Gaeta, X. Gao, B. Shim, L. Plaja, R. Levis, M. Tarazkar, M.E. Foord, J.A. Gaffney, S.B. Libby We present data from two recent experiments. First, we demonstrate direct observations of localized light absorption in a single nanoparticle irradiated by a strong femtosecond laser field. By imaging the photoion momentum distribution resulting from plasma formation in a laser-irradiated nanostructure, we map the spatial location of the highly localized plasma and thereby image the nanoscale light absorption. Secondly, we show the high linear and nonlinear UV refractive indices of both neutral atoms and ions compensate for plasma dispersion, even in multiply-ionized gases. [Preview Abstract] |
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YP8.00035: Temperature Equilibration in Tantalum Nicholas Hartley, Patrick Belancourt, David Chapman, Tilo Doeppner, R Paul Drake, Dirk Gericke, Siegfried Glenzer, Dimitri Khaghani, Carolyn Kuranz, Sebastien LePape, Tammy Ma, Paul Neumayer, Art Pak, Lauren Peters, Scott Richardson, Jan Vorberger, Thomas White, Gianluca Gregori Understanding the behavior of materials with significantly different electron and ion temperatures is important for much of the experimental and theoretical work on dense plasmas. We present measurements of electron-ion temperature equilibration in proton-heated tantalum, under warm dense matter conditions. Our results agree with theoretical predictions calculated from {\it ab initio} molecular dynamics simulations, as well as with those from the Fermi Golden Rule approach often used for dense plasmas. However, the fast relaxation time observed in the experiment contrasts with much slower equilibration found in particle-heated carbon, indicating that the energy flow pathways in warm dense matter are far from being fully understood. [Preview Abstract] |
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YP8.00036: Simultaneous imaging of edge-localized filaments in inboard and outboard sides of KSTAR H-mode plasmas Jaehyun Lee, Gunsu Yun, Minwoo Kim, Minjun Choi, Gyeng-Hyeon Choe, Woochang Lee, Hyeon-Keo Park, Neville C Luhmann Jr, Sang-Hee Hahn, Kyu-Dong Lee, Siwoo Yoon The spatial structure and temporal dynamics of edge-localized modes (ELMs) have been visualized simultaneously in the inboard and the outboard side pedestal of the KSTAR H-mode plasmas for the first time [1] using electron cyclotron emission imaging (ECEI) system [2]. The poloidal mode spacing of the inboard ELM filaments is much larger than the ballooning mode spacing predicted from the images of the outboard ELM filaments. The inboard ELM filaments rotate counter-clockwise (or clockwise) poloidally, opposite to the clockwise (or counter-clockwise) rotation of the outboard ELM filaments. This discrepancy suggests an asymmetry in the poloidal and/or toroidal flow of ELM filaments. In the crash dynamics, the outboard perturbation amplitude is larger compared to the inboard one and the ELM crash seems to be initiated by the bursts of the outboard ELM filaments, which is indicative of the ballooning feature of the ELM crash. [1] H.K. Park et al 2014 Proc. 25th Int. Conf. on Fusion Energy 2014 (Saint Petersburg, 2014) (to be published) [2] G.S. Yun et al., Rev. Sci. Instrum. 81 (2010) 10D930 [Preview Abstract] |
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YP8.00037: Feasibility of an experiment to measure stopping powers in solid-density deuterium plasmas at OMEGA B. Lahmann, H.G. Rinderknecht, A.B. Zylstra, J.A. Frenje, C.K. Li, F.H. Seguin, R.D. Petrasso, S. Regan, C. Sangster, F. Graziani, G.W. Collins, J.R. Rygg, P. Grabowski, S. Glenzer, P. Keiter An experimental design to measure the stopping powers of charged-particles through solid-density, fully-ionized deuterium plasmas at temperatures around 10 eV is investigated. Stopping power in this regime is crucial to the understanding of alpha-heating and burn in Internal Confinement Fusion. Recent work by A.B. Zylstra \textit{et al.} on the OMEGA laser facility has demonstrated such measurements of stopping power in partially ionized Be plasmas, by measuring the downshift of D$^{3}$He-protons in an isochorically heated sample. As noted in their work, the effects of partial ionization are not well understood; however such effects are not applicable to hydrogenic fuels, for which the plasmas are expected to be fully ionized. This study will consider the viability of isochorically or shock heating a target to Warm Dense Matter conditions using a platform similar to the planar cryogenic system described by S.P. Regan \textit{et al.}\footnote{S.P. Regan \textit{et al}., Phys. Rev. Lett. \textbf{ 109}, 265003 (2012).} Plasma properties will be determined by x-ray Thomson scattering while stopping powers will be inferred through measuring downshift of either DD-protons, D$^{3}$He-protons or D$^{\mathrm{3}}$He-alphas, the latter of which is directly applicable to the stopping of DT-alphas in ignition experiments. This work was supported in part by the U.S. DOE, NLUF, LLE, and LLNL. [Preview Abstract] |
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YP8.00038: Design of a Dual-Beam Electron Gun Michael Lambrecht, Michael Haworth, Wilkin Tang, Peter Mardahl A dual beam electron gun is being designed as the driver for a microwave amplifier utilizing the two-stream instability. The two-stream amplifier was designed to use relativistic electron beams, and has achieved 30 dB gain at 9 GHz in 2-D ICEPIC simulations. Two annular electron beams are launched with different current, radii, and energies, co-propagating down a cylindrical waveguide to create the two-stream instability used for amplification. The parameters for the electron gun to create these beams simultaneously are stringent. The beam temperature must remain less than 0.5{\%}, and the amount of transverse energy of the beam as it enters the drift tube must be as close to zero as possible, as both of these parameters seriously degrade the amplification and efficiency of the amplifier. The dual-beam electron gun will be designed with TRAC (Field Precision, LLC), and will initially utilize a Friedman-style electron gun for the outer radius beam co-located with a ``cookie-cutter'' electron gun to create the inner radius beam. The design will seek to minimize beam spin and energy spread. [Preview Abstract] |
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YP8.00039: Measurements of Reynolds stress and its contribution to momentum balance in the HSX stellarator Robert Wilcox, David Anderson, Joseph Talmadge, Simon Anderson It has been predicted that for a sufficiently optimized quasi-symmetric stellarator, the neoclassical non-ambipolar transport and viscosity can be small enough that other terms, such as the Reynolds stress resulting from plasma turbulence, can compete with it in the momentum balance to determine the rotation and radial electric field. In this case, the experimental flows may deviate from values calculated using the ambipolarity constraint by purely neoclassical codes such as DKES and PENTA which are commonly used for stellarators. Using multi-tipped Langmuir probes in the edge of the HSX stellarator, the radial electric field and parallel ion flows are found to deviate from the values calculated by PENTA in the edge of the optimized quasi-helically symmetric (QHS) configuration. A large Reynolds stress flow drive is measured via fluctuating floating potential signals in the same radial region as the measured deviation from neoclassical calculations. Probe measurements are made at two locations on the device near the maximum of variation of magnetic geometry on a flux surface. Experiments have been run in both the QHS configuration and configurations with the symmetry intentionally broken to explore the relationship between the neoclassical optimization and the measured deviation of the flows from the calculated neoclassical value. [Preview Abstract] |
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YP8.00040: Waves in a strongly coupled 2D superparamagnetic dusty plasma M. Rosenberg, G.J. Kalman, Z. Donko, P. Hartmann, S. Kyrkos In a two-dimensional (2D) dusty plasma composed of superparamagnetic dust grains and immersed in an external magnetic field, the dust interacts via both Yukawa and magnetic dipole-dipole interactions. The induced magnetic dipole moments of the grains all lie along the magnetic field ${\bf B}$. When the direction of ${\bf B}$ is tilted with respect to the dust layer, the interaction between the grains becomes anisotropic. We have theoretically considered the behavior of waves in the strongly coupled liquid phase of this system [1], using the Quasi-Localized Charge approximation combined with molecular dynamics simulations. The analyis is confined to magnetic tilt angles where the interaction remains repulsive in the dust layer, which allows for a stable equilibrium. Two new directions are explored. One relates to possible coupling between in-plane and out-of-plane polarized modes in a quasi-2D liquid phase, taking into account the effect of an external potential that confines the layer. The other relates to the crystalline state and how different lattice structures can arise and how they affect wave behavior. \\[4pt] [1] P. Hartmann, Z. Donko, M. Rosenberg and G. J. Kalman, {\it Phys. Rev. E} {\bf 89}, 043102 (2014). [Preview Abstract] |
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YP8.00041: Impure tokamak pedestals with strong radial electric field Silvia Espinosa, Peter J. Catto A high confinement mode pedestal has density and potential variation on the poloidal ion gyroradius scale. As a result, the ExB-drift associated with radial electric field can compete with the poloidal projection of parallel ion streaming, making alternate neoclassical descriptions necessary. In addition, Alcator C-Mod experiments\footnote{C. Theiler et al., \textbf{Nucl. Fusion} 54,083017} make it clear that the impurity diamagnetic drift contribution must be allowed to be comparable to the impurity poloidal and toroidal flows to measure the radial electric field. Furthermore, Churchill et al.\footnote{R.M. Churchill et al., \textbf{Nucl. Fusion} 53,122002} experimentally observe stronger poloidal variation of the impurity density than predicted by the most comprehensive theoretical models developed to date. A neoclassical ordering valid for slowly varying background ion temperature profiles in subsonic pedestals has been formulated that allows impurity diamagnetic flow effects to enter to lowest order. It results in strong poloidal impurity variation and possibly provides a more realistic model for pedestal observations, by extending the seminal work of Helander.\footnote{P. Helander, \textbf{Phys. Plasmas} 5,3999} [Preview Abstract] |
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YP8.00042: Electrode Biasing Experiment In KMAX Tandem Mirror Xuan Sun, Qing Zhang, Ming Liu, Peiyun Shi, Munan Lin An electrode biasing system has been installed on KMAX (Keda Mirror with AXisymmetricity) tandem mirror machine to control the rotation speed. It consists of a metal disk-type and a concentric ring-shaped electrode. On each of them there are 12 embedded single probes distributed uniformly in the azimuthal direction plus a single probe on the center. An adjustable power supply provides the biasing voltage from -1kV to 1kV, and a SCR with rising time $\sim$ 10$\mu$s and maximum current up to 3000A is used to switch on the circuit. While most of applied voltages are lost on the sheath, the plasma potentials have been found to change substantially. [Preview Abstract] |
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YP8.00043: Investigation on the shaping of poloidal flow in the biased electrode experiment Yi Yu, Haijun Ren, Huajie Wang, Tao Lan, Yumei Hou, Shuangyuan Feng, Yizhi Wen, Changxuan Yu, Minyou Ye Investigations on the drives of the poloidal flow are presented in this article. The poloidal flow is the main contributor to the radial electric field. Not only Reynolds stress but also the Lorentz's force can drive the poloidal flow. The Reynolds stress accounts for about a quarter of the contribution to the poloidal flow in the biased electrode discharges. Investigations on the drives of poloidal flow and the spectra analyses in the biasing experiments show the momentum and energy transfer from the high frequency turbulence into the low frequency poloidal shear flow via Reynolds stress. [Preview Abstract] |
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YP8.00044: Electron fluid simulations of 2D electron vortices Justin Angus, Steve Richardson, Joseph Schumer, Steve Swanekamp, Paul Ottinger The production of electron vortices in current-carrying plasmas has been observed in recent 2D particle-in-cell (PIC) simulations of the plasma-opening switch. In the presence of a background density gradient in 2D Cartesian systems, vortices will drift in the \textbf{B}xGrad(n) direction, where \textbf{B} is the magnetic field vector and n is the background plasma density. Vortices are important because of the possible role they play in the penetration of magnetic fields into plasmas. The time scales relevant to electron vortices are typically small enough such that the ions can be considered as infinitely massive and motionless. Here we present results of numerical simulations of 2D, seeded electron vortices in an inhomogeneous background using the cold, collisionless electron fluid equations coupled to the full set of Maxwell's equations. The results of these simulations are compared with results of PIC simulations and the underlying physics of the drift is explored in detail. [Preview Abstract] |
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YP8.00045: GRIM: An Implicit Code for Nonideal General Relativistic MHD Mani Chandra, Charles Gammie Highly sub-Eddington black hole accretion flows like Sgr A* are expected to be collisionless yet are commonly modeled as an ideal fluid. Electron conduction, anisotropic pressure, and viscosity can be important in a collisionless plasma and will potentially alter the dynamics and radiative properties of the flow from that in ideal fluid models. We present a new code, GRIM, that enables conduction and other effects to be efficiently incorporated into a GRMHD code. GRIM is a fully implicit Newton-Krylov shock capturing code that converges at second order on smooth flows. It features an efficient and automated Jacobian assembly with finite differences that uses graph coloring to exploit the sparsity of the discretization of a pde. This makes it easy to incorporate additional physics. The code correctly captures classical GRMHD test problems as well as a new suite of test problems with anisotropic conductivity. As a test and an example application we report on a relativistic version of the magneto-thermal instability, and we show an example integration of a black hole accretion flow. [Preview Abstract] |
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YP8.00046: Magnetic field formation and diffusion via biermann battery effect for laboratory cluster blast waves Alberto Marocchino, Lorenzo Romagnani, Anna Levy, Satoshi Jinno, Yuji Fukuda, Livia Lancia, Alessandra Ravasio, Angelo Schiavi, Stefano Atzeni, Domenico Doria, Marco Borghesi A recent campaign on the ELFIE laser at LULI investigated laboratory Blast Waves (BW) relevant to astrophysical scenarios. A 2$\omega $ 2J laser was focused into an Argon cluster gas in order to launch an intense Blast Wave ($\varepsilon \sim$ 0.5MJ/cm$^{3})$. Its evolution was investigated from the early Coulomb explosion to late times ($\sim$ 50ns) via proton radiography, revealing an intense electric field with B-field traces at early times, and no fields detected in the later, purely hydrodynamic phase. Simulations performed with the DUED code reproduce well the experiment, confirming magnetic field formation in the early phase, where the Biermann Battery term is for a short time dominant. At late times, magnetic field diffusion becomes dominant with the B-field diffusing away in front of the BW and only a small portion captured within the remnant. [Preview Abstract] |
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YP8.00047: Ions acoustic oscillations driven by ion flow in a finite length systems Oleksandr Koshkarov, Andrei Smolyakov, Igor Kaganovich, Victor Ilgisonis Plasmas with stationary flow are common in a number of application such as diagnostics with emissive probes, plasma electronics and electric propulsion devices. The presence of plasma flows often lead to the instabilities in such systems and subsequent development of large amplitude perturbations. In this work we consider dynamics of ion acoustic oscillations in a finite length plasma with the equilibrium flow of ions. It is shown that the finite flow induces the instability due to coupling of the negative and positive energy modes. The mode coupling occurs via boundary conditions in a finite length system. The instability is studied via combination of analytical theory and numerical methods utilizing Godunov and multiple shooting schemes. The instability diagram is obtained as a function of the flow velocity and the system length. [Preview Abstract] |
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YP8.00048: Gradient-drift and low hybrid modes in Hall plasmas Ivan Romadanov, Winston Frias, Andrei Smolyakov, Yevgeny Raitses, Igor Kaganovich Hall plasmas with electron ${\bf E}\times {\bf B}$ drift often exhibits wide range of unstable modes affecting operation and performance of various devices, e.g. such as magnetrons and Hall thrusters. The plasma density and magnetic field gradients were previously identified as important source of long wavelength modes (Simon-Hoh or so called anti-drift mode). The shorter wavelength instabilities, such as low-hybrid, are also triggered by density and magnetic field gradients. On other hand, the low-hybrid modes are excited by collisional processes. Interaction of gradient-drift and low hybrid modes in presence of dissipation has a complex characters depending on the modes wavelength. Here, we investigate the characteristics such interaction for typical parameters of Hall thrusters. [Preview Abstract] |
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YP8.00049: Envelope structures of coupled drift-zonal flow system in a dissipative tokamak plasma Anuraj Panwar, Chang-Mo Ryu, Raghvendra Singh In this paper, the modulational instability and associated envelope structures of coupled drift-zonal flow system in a dissipative tokamak plasma are investigated. Dissipative non-linear Schrodinger (NLS) equation is derived by using the derivative perturbation expansion method to govern the dynamics of modulated waves. Dissipative effects due to the collisions and kinematic viscosity significantly modify the growth of modulational instability. Dissipative NLS equation admits the localized solutions in the form of drift wave envelope solitons along with shock like zonal flow structures. The height of drift wave envelope solitons and zonal flow shock structures decreases with the increase in collisional and viscous dissipation. [Preview Abstract] |
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YP8.00050: Physics Properties of High Ratio Compression Gases Cheng Li, Yian Lei High ratio adiabatic compression of gasses can reach very high temperature. In a conical liquid metal compression device, very high compression ratio up to 10$_{\mathrm{9}}$ to 1 can be quite easily achieved. Idea gas compression would give a temperature rise of 10$_{\mathrm{6}}$ times of original room temperature, which is tens of keVs, reaching the realm of nuclear fusion. However, as the gas is dissociated and ionized by under high temperature, the real situation is not so optimistic. We analyzed the physics of the high ratio compression of normal gasses, taking account of dissociation, ionization, radiation loss, and possible energy loss due to gas (plasmas) and wall interaction, and try to find the formalism for the temperature and pressure in the process. The above mechanism drastically lowered the temperature of adiabatic compression. We also discussed the possibility of fusion by pure compression. [Preview Abstract] |
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YP8.00051: ABSTRACT WITHDRAWN |
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YP8.00052: Measurements of Plasma Temperature and Density Profiles Using Grid Image Refractometry for Laser Fusion Research Jaechul Oh, J.L. Weaver, M. Karasik, L.Y. Chan Electron density ($n_e$) and temperature ($T_e$) profiles of coronal plasma have been experimentally characterized using the grid image refractometer\footnote{R.S. Craxton, et al, Phys. Fluids B 5, 4419 (1993).} recently implemented at the Nike KrF laser facility (Nike-GIR). This instrument measured propagation angles and transmissions of probe laser ($\lambda = 263$ nm, $\Delta t = 10$ psec) beamlets refracted through a CH plasma produced by the Nike laser pulse ($\sim 1$ nsec FWHM) with the intensity of $1.1 \times 10^{15}$ W/cm$^2$.\footnote{J. Oh, et al, BO4.2, APS DPP (2013).} The measured angles were processed by an iterative algorithm to construct self-consistent $n_e$ profiles. The spatial profile of $T_e$ was also examined using the obtained $n_e$ profiles and the measured transmission data. The resulting $n_e$ and $T_e$ profiles were verified to be self-consistent with the measured quantities of the refracted probe light. [Preview Abstract] |
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YP8.00053: Experimental investigation of the interaction between a short high-intensity laser pulse and a long and hot plasma Clement Goyon, Sylvie Depierreux, Claire Baccou, Cl\'ement Courvoisier, Guillaume Loisel, Vincent Yahia, Natalia Borisenko, Paul-Edouard Masson-Laborde, Andrei Orekhov, Olga Rosmej, Vladimir Tikhonchuk, Christine Labaune Shock ignition (SI) is a two steps alternative direct-drive scheme for inertial fusion. The first one is a several nanoseconds long compression with low intensity beams. The second one is a several hundred of picoseconds stage using high intensity beams to create a converging shock leading to ignition. The coupling of this intense pulse with the coronal plasma is the most unknown of this scheme. We have designed an experiment that couples a high intensity laser pulse (526nm 20J 1-12 ps) and a high-energy laser pulse (526nm 400J 1.5 ns). We are able to study the interaction in the intensity range from 1015 up to 3.1016 W/cm2 relevant to the interaction of the SI spike in preformed, hot (1 keV) and long (mm scale) plasmas. The picosecond beam was used with a random phase plate as the interaction pulse. We present the first measurements of time-resolved backscattered spectra from the smoothed picosecond beam as well as the transmitted intensity distribution through the plasma. We find that Brillouin instability can be responsible for up to 60{\%} reflectivity in plasmas while Raman reflectivity stays at low levels. [Preview Abstract] |
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YP8.00054: Numerical modeling and simulation of a magnetohydrodynamic(MHD) generators Hyoungkeun Kim, E. David Huckaby, Rigel Woodside, Thomas Ochs A MHD generator is a device that extracts electricity directly from thermal energy and kinetic energy. In a MHD generator, a supersonic fluid flow under applied magnetic field is used to produce electricity without any moving mechanical parts. Two numerical solvers have been developed to predict the dynamics of the fluid and the electricity generation efficiency: a 1D MHD code for quick assessment and design calculations and a customized OpenFOAM solver for multidimensional analysis under the low magnetic Reynolds number approximation. The 1D MHD code uses a space marching approach and includes non-equilibrium chemical reactions. The resulting differential algebraic system is integrated using the Sundials library via Assimulo package. Cantera(chemical reaction library) is used for non-equilibrium chemistry, thermodynamic properties and transport properties. The multidimensional code discretizes the equations via the standard finite-volume schemes available OpenFOAM. The compressible codes in OpenFOAM are modified to include the additional physical processes to model an MHD channel. Verification and validation work for both in progress. This testing includes consistency tests, comparison with previously published numerical solutions and with published experimental measurements. [Preview Abstract] |
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YP8.00055: Heat Pulse Thermal Conductivity in Alcator C-Mod L-mode and I-mode Plasmas A.J. Creely, E.M. Edlund, N.T. Howard, A.E. Hubbard, A.E. White I-mode plasmas are characterized by high energy confinement, similar to H-mode, but with L-mode-like particle confinement, making I-mode very favorable for reactors due to the natural absence of Edge Localized Modes (ELMs) [D.G. Whyte et al 2010 Nucl. Fusion 50, 105005]. It is also observed at Alcator C-Mod that core turbulence (0.4 \textless r/a \textless 0.8) is reduced in I-mode compared to L-mode [A.E. White et al 2014 Nucl. Fusion 54, 083019]. Power balance analysis indicates that the effective thermal diffusivity, is reduced in I-mode as well, and linear gyrokinetic analysis suggests that the growth rate of the ion temperature gradient mode is reduced in I-mode. It is of interest to consider perturbative transport analysis, not just steady state analysis. We calculate a perturbative thermal diffusivity from the propagation of heat pulses generated by sawtooth crashes. Preliminary analysis indicates that the heat pulse thermal diffusivity is reduced by 35{\%} in I-mode compared to L-mode, which appears, superficially, to be consistent with the overall improved energy confinement in I-mode. [Preview Abstract] |
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YP8.00056: Correlation of dust injection rate and microwave penetration of an overly dense plasma layer Eric D. Gillman, Jeremiah Williams, Bill Amatucci Microparticle injection into a plasma discharge, producing a dusty plasma, has been shown to significantly reduce the electron density as electrons are captured during the microparticle charging process. This has in turn been shown to increase the transparency and penetration of microwaves into an overly dense plasma layer. Results from these studies focus on understanding the correlation between the rate of microparticle injection and effects on microwave penetration of the plasma layer, as well as microwave scattering off of the charged microparticles. These studies are applicable for mitigating the communications radio blackout problem experienced by hypersonic vehicles and may have additional applications for satellite communications. [Preview Abstract] |
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YP8.00057: 3D Diagnostics of Plasma Interactions with Surface Alexander Mustafaev, Artiom Grabovskiy, Anastasiya Strakhova, Vladimir Soukhomlinov The plasma-surface interactions play an important role in various kinds of plasma applications. In the same time the physical behind of these processes is not well understood, that's why developing new plasma diagnostics methods is the main task for plasma engineering. This talk presents 3D diagnostics method of plasma interaction with surface, which has been developed for wide range of plasma types. In knudsen diode with surface ionization the processes of secondary electron emission (SEE) from poly-crystal surfaces has been investigated. It is shown that SEE yield can be indeed very high ($\sim$ 0.8) but still not approaching unity. This result is explained by additional reflection of primary electrons from a potential barrier near the poly-crystal surface. The contribution of electron reflection from the barrier and the surface has been identified and studied. In plasma of helium and mercury glow discharge this method has been successfully applied for measurements of electron and ion distribution functions. The reliability of the method has been tested by comparing experimentally measured distributions of electrons and ions with results of theoretical calculations, taking into account ambipolar field in plasma. This work was supported by Education Ministry of Russian Federation. [Preview Abstract] |
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YP8.00058: Generation of high-density, thin gas jets for high repetition-rate experiments Yuan Tay, Luke Hahn, Yong-Sing You, Howard Milchberg, Ki-Yong Kim We have investigated the production of thin (50 - 500 microns), high-density (10$^{19}$ - 10$^{21}$ cm$^{-3})$ gas jets at high backing pressure (1000 psi) and cryogenic temperature (100 K). Capillary tubes with various diameters are used to produce thin and dense gas jets in continuous flow. The gas density profiles are characterized by optical interferometry. Rayleigh/Mie scattering is also monitored to check the presence of argon clusters. Our result shows a peak gas density of 10$^{21}$ cm$^{-3}$ near the nozzle orifice, approaching the critical plasma density at 800 nm laser wavelength when the gas target is singly ionized. This high-density gas jet, achieved by high backing pressure and cryogenic cooling, can allow studies of laser interaction with overdense plasmas in gas targets, without generating unwanted debris as in solid targets. [Preview Abstract] |
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YP8.00059: Electon oscillation damping in ultracold plasmas Wei-Ting Chen, Jacob Roberts By applying sharp electric field pulses to an ultracold plasma (UCP), it is possible to induce an electron center-of-mass oscillation around the ion center-of-mass. This oscillation damps at a rate that is dependent on UCP parameters such as electron temperature, UCP charge neutrality, electron density, and others. By tuning the experimental parameters of the UCP carefully, the main contribution to the damping rate is electron-ion collisions. Thus, the electron-ion collision rate can be studied in these systems. Our recent experimental results are reported, as well as our plans to extend these measurements further towards a more strongly-coupled electron component regime. [Preview Abstract] |
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YP8.00060: Development of the Small Helicon Magnetoplasma Thruster (SHMAPT) Celso Ribeiro, Jorge Andres-Diaz, Ralph Garcia-Vindas, Elian Conejo, Gerardo Padilla-Viquez, Alexis Devitre, Esteban Avendano, Eduardo Calderon, Leonardo Lesser-Rojas Magnetoplasma-based electric rocket devices are envisaged to be used for the same tasks as those of ion thrusters (e.g. satellites' orbital correction). So far, the electrodeless types seem as the only feasible way to lead manned missions into deep space. We have constructed a small helicon magnetoplasma thruster (SHMAPT) to study the physics of helicon plasma (e.g. the double helicon structure) and its relation with the thrust, specific impulse, and the plasma-wall interaction, using a variety of gases. Diagnostic developments have been planned using Mach and Langmuir probes, strain-gauges, and light emission spectroscopy. SHMAPT is composed by a water-cooled cooper helicon antenna (6 cm length, 2.6 cm diameter) mounted onto a sapphire tube (1.5 mm thickness, 2.5 cm external diameter, 40 cm length). The antenna is coupled to a commercial 13.56 MHz source with variable power (initially up to 600 W and later up to 5 kW). Two NdFeB permanent magnets, each of 0.24 T, are fitted at the extremities of the antenna. This structure is assembled into a square 0.07 m$^{3}$ high vacuum chamber pumped by a 50 l/s turbo pump backed by a 2.5 m$^{3}$/h diaphragm pump. Preliminary results will be presented. [Preview Abstract] |
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YP8.00061: Calibration of $^{22}$Na Using the Sum-Peak Counting Method Mollie Bienstock, Ryan Fitzgerald A calibrated positron emitter, $^{22}$Na, is needed for nuclear cross section measurements. The calibration of this source was performed using a self-calibrating sum-peak counting method which has the potential to replace calibrated sources for various other applications. The sum-peak method was used with three different detector setups: a single high purity germanium detector, a 4"x5" NaI well detector and the same NaI well detector paired with a 3"x3" NaI detector, obtaining a 4$\pi$-counting geometry. The $^{22}$Na decays via positron emission mostly to an excited state of $^{22}$Ne which promptly de-excites and emits a 1275 keV gamma ray. The 511 keV gamma ray produced from the positron annihilation sums with the 1275 keV gamma generating a 1786 keV peak in the observed spectra. The total counts in the three peaks as well as the total counts observed in the spectrum are used to calculate a value for the activity of the source. In order to get a better understanding of the source and the detector geometries, a simulation of the setups was generated using EGSnrc: software that uses Monte Carlo simulations to model radiation transport. Using this program, and subsequent Monte Carlo calculations, a model of the spectra produced from each setup was created and used to fit theory to data and get a more accurate number for the activity of the source. Results obtained from this experiment are being compared to independent measurements from HPGe gamma ray spectrometry and 4$\pi$ NaI integral counting using calibrated detectors. [Preview Abstract] |
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