Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012; Providence, Rhode Island
Session BP8: Poster Session I: NonNeutral, Dusty, and Strongly Coupled Plasmas I; Non Linear Phenomena and Turbulence Experiment; Plasma Waves; Stellarator, General Tokamak, Transport and Turbulence Theory 
Hide Abstracts 
Room: Hall BC 

BP8.00001: NONNEUTRAL DUSTY AND STRONGLY COUPLED PLASMAS I 

BP8.00002: Experimental limit on the ratio of the gravitational mass to the inertial mass of antihydrogen Joel Fajans, Jonathan Wurtele, Andrew Charman, Andrey Zhmoginov Physicists have long wondered if the gravitational interactions between matter and antimatter might be different from those between matter and itself. While there are many indirect indications that no such differences exist, i.e., that the weak equivalence principle holds, there have been no direct, freefall style, experimental tests of gravity on antimatter. By searching for a propensity for antihydrogen atoms to fall downward when released from the ALPHA antihydrogen trap, we have determined that we can reject ratios of the gravitational mass to the inertial mass of antihydrogen greater than about 100 at a statistical significance level of 5{\%}. A similar search places somewhat lower limits on a negative gravitational mass, i.e., on antigravity. [Preview Abstract] 

BP8.00003: Studies of the residual gas composition in ALPHA using an autoresonantspectrometric method Marcelo BaqueroRuiz Knowledge of the residual gas composition in the ALPHA experimental apparatus is important in our studies of antihydrogen and nonneutral plasmas. Experiments done using autoresonant ion extraction from an electrostatic potential well have made it possible to study the vacuum in our trap through comparison with computer simulations. Here we report our findings after the 2011 experimental run in ALPHA. [Preview Abstract] 

BP8.00004: Cooling Electron Plasmas by CyclotronCavity Resonance Alex Povilus, Marcelo BaqueroRuiz, Steve Chapman, Joel Fajans A robust technique for cooling trapped nonneutral plasmas is to allow leptons to thermalize to the temperature of the experimental environment through cyclotron emission. Storing these plasmas in a highQ cavity can enhance or inhibit this cooling mechanism dependent on the cyclotron frequency, the electromagnetic mode structure in the cavity, and the profile of the trapped plasma. Also, thermalization rates may be limited as temperatures in the system approach the energy spacing between Landau levels the quantum mechanical levels of transverse particle motion in the system. This is a regime possible in a cryogenic environment with high magnetic fields, such as typically used in PenningMalmberg traps. Here, we report on the progress of the cold electron research experiment at UC Berkeley designed to measure these effects. [Preview Abstract] 

BP8.00005: Experimental and computational study of autoresonant injection of antiprotons into positron plasma in antihydrogen production Chukman So, Jonathan Wurtele, Joel Fajans, Lazar Friedland, William Bertsche The injection of antiprotons into positron plasma during antihydrogen synthesis in ALPHA is simulated numerically and compared with experimental measurements. The antiprotons and positrons are initially confined in adjacent axial potential wells in a nested PenningMalmberg trap. The antiproton plasma is excited autoresonantly and partially injected into the adjacent positron plasma, creating antihydrogen. The excitation and injection process is modeled numerically with a hybrid code in which the antiproton plasma responds to the autoresonant drive fully dynamically, and the positrons respond quasistatically. The strong axial magnetic field suppresses radial transport on the timescales of interest. The antiproton plasma is thus assumed to consist of concentric cylindrical tubes within which antiprotons move only in the axial direction, and the evolution of the phase space distributions in each tube obeys a onedimensional Vlasov equation. The antiproton selffield is obtained by solving the Poisson equation in twodimensions, thereby coupling the tubes. Alternative injection schemes and the effect of varying antiproton number and temperature are also examined. [Preview Abstract] 

BP8.00006: Single particle motion and gravitational measurements in magnetostatic antihydrogen traps Andrey Zhmoginov, Jonathan Wurtele, Joel Fajans, Andrew Charman Recent progress in antihydrogen trapping [13] marks the beginning of physics measurements on neutral antimatter. One of the goals of such experiments is the observation of gravitational interaction of antimatter with matter. New methods for such measurements have been proposed, based on the statistical analysis of the temporal and spatial pattern of antihydrogen annihilations during slow (compared to bounce times) shutdowns of the mirror and octupole magnets that comprise the magnetic trap. These techniques require a thorough understanding of nonlinear dynamics of antihydrogen in magnetic traps. We apply a Hamiltonian perturbation theory to this system, analyze phase space dynamics and classify single particle orbits. The role of the stochasticity, and the Arnold diffusion accompanying it, on the accuracy of gravitational measurements is discussed. The analytical results are verified numerically, different approaches to slow particle release are compared, and implications for lasercooling are discussed. \\[4pt] [1] G. B. Andresen and ALPHA Collaboration, {\em Nature} {\bf 468}, 673 (2010). \newline [2] G. B. Andresen and ALPHA Collaboration, {\em Nature Physics} {\bf 7}, 558 (2011). \newline [3] C. Amole and ALPHA Collaboration, {\em Nature} {\bf 483}, 439 (2012). [Preview Abstract] 

BP8.00007: Understanding axisymmetric Bernstein modes in a nonneutral plasma Grant W. Hart, Ross L. Spencer We have been studying axisymmetric Bernstein modes in a nonneutral plasma using both kinetic theory and simulation. Because of the large electric fields in these unneutralized plasmas, the oscillations are shifted down from the cyclotron frequency. Most of the modes occur near the Dopplershifted upperhybrid frequency, called the vortex frequency. In cylindrical geometry for a constantdensity initial plasma, the perturbed velocity goes as $J_{1}(kr)$. For any given $k$ there are two modes, one upshifted from the vortex frequency and one downshifted. The boundary condition which determines the allowed values of $k$ is that the perturbed pressure must go to zero at the boundary. There is also another mode that does not follow this rule, however. This mode is very near the vortex frequency (0.1\%  1\% frequency difference) and the pressure does not contribute significantly to the dynamics of the mode. This mode is most fruitfully treated as a small pressure perturbation of the upperhybrid oscillation. The pressure causes a small upward frequency shift, which creates a small deviation from a selfsimilar velocity profile and therefore a nonzero $k$. The simultaneous solution of the perturbed dynamics and the dispersion relation allows the frequency and $k$ to be calculated. [Preview Abstract] 

BP8.00008: Modeling axisymmetric radial Bernstein modes in a finitelength nonneutral plasma Mark Hutchison, Ross L. Spencer, Bryan G. Peterson, Grant W. Hart Axisymmetric radial Bernstein modes are known to exist in nonneutral plasmas and have been studied theoretically, but detection of these modes has still proven to be difficult due to selfshielding. While it is improbable that these modes will be detected in long systems, there is a possibility of exciting and detecting these modes in a finitelength plasma by oscillating the confinement potentials in a MalmbergPenning trap. Generating axisymmetric radial Bernstein modes in a short plasma will sufficiently couple the axial and radial motions that a clear oscillation signature may be observed on detection rings placed at the ends of the plasma. We are analyzing the excitation and frequency of these modes using an rz particleincell code in order to explore the possibility of detection via this method. We will be discussing our code and our progress in carrying out these objectives. [Preview Abstract] 

BP8.00009: Density Scaling Studies in Toroidal Electron Plasma and Upgrade Plans for the Lawrence NonNeutral Torus II M.R. Stoneking, J.W. Darrell, S.A. Exarhos, A.S. Patterson, M. Price, A.H. Wright Electron plasma is confined using a purely toroidal magnetic field ($R_{o}=$ 18 cm, $B <$ 550 G) for times ($\sim $500 ms) that are much longer than any of the dynamical timescales of the system. The Lawrence NonNeutral Torus II (LNT II) can be operated as a partial torus in which plasma is confined in Cshaped toroidal sectors or as a fully toroidal, closed field trap. Electron density is controlled by adjusting the injector (filament) bias and by attempts to apply a ``rotating wall.'' Confinement and diocotron mode damping are measured by monitoring image charge on isolated wall sectors. High relative density ($>$10$^{7}$ cm$^{3})$ fully toroidal plasma is also generated by placing the injector at the edge and gating the bias voltage. We also present plans to upgrade the magnetic field (to exceed 1 kG) and enhance the diagnostic capabilities of the LNT II to permit measurement of higher order modes. This work is supported by the National Science Foundation  Award {\#}1202540. [Preview Abstract] 

BP8.00010: Dependence of enhanced asymmetryinduced transport on collision frequency D.L. Eggleston Our previous studies\footnote{D.~L. Eggleston, Phys. Plasmas {\bf 19}, 042307 (2012).} of asymmetryinduced radial transport using a singleparticle code with collisional effects have identified, for asymmetries of the form $\phi_1(r)\cos{(kz)}\cos{(\omega t  l\theta)}$, two sources for the transport: resonant particles (RPs) and axially trapped particles (ATPs). We observe that this latter type, which occurs near the radius where $\omega$ matches the azimuthal rotation frequency $\omega_R$, is often dominant at low collision frequency $\nu$ but becomes negligible at higher $\nu$. This can be understood by noting that ATPs have a lower trapping frequency $\omega_T^2= (l^2\phi_1/rB)d\omega_R/dr$ than RPs. In the low $\nu$ (banana) regime, the radial oscillations have amplitude $\Delta r= v_r/\omega_T$, so ATPs dominate, and the transport may even exceed the RP plateau regime level. As $\nu$ increases, collisions start to interrupt the slower ATP oscillations while the RPs are still in the banana regime, so the ATP contribution to the transport decreases. At the largest $\nu$ values, ATP transport is negligible and the observed diffusion coefficient matches that given by plateau regime RP theory.\footnote{D.~L. Eggleston and T.~M. O'Neil, Phys. Plasmas {\bf 6}, 2699 (1999).} [Preview Abstract] 

BP8.00011: Simulation studies of the behavior of positrons in a microtrap with long aspect ratio Alireza Narimannezhad, Jia Xu, Christopher J. Baker, Marc H. Weber, Kelvin G. Lynn The capacity to store charged particles in microtraps (microPenningMalmberg traps) with large length to radius aspect ratios and with radii of the order of microns is explored. This paper presents how to reduce simulation noises by changing modeling parameters to achieve a nearly computational equilibrium distribution. Simulation studies of the motions of charged particles were conducted with the Charged Particle Optics (CPO) program and particleincell plasma code WARP. Individual microtraps have radii of 50 $\mu$m and 10 cm length and are immersed in a uniform 7 Tesla magnetic field. The new design of the trap consists of an array of microtraps with confinement voltages of 10 V. It has been computationally shown that each microtrap stores positrons with higher density ($\sim$4.8E11 cm$^{3}$) compared to a conventional PenningMalmberg trap ($<$1.0E11 cm$^{3}$). The results of the simulation of a plasma initialized with a uniform density and Boltzmann energy distributions showed that the plasma tends to transform to a soft edge distribution in radial direction as it approaches the equilibrium. Theoretically, more than hundred million positrons can be trapped in one microtrap with the present geometry. [Preview Abstract] 

BP8.00012: Transport coefficients in plasmas spanning weak to strong correlation Scott Baalrud, Jerome Daligault Plasmas encountered in several modern research areas can reach strong correlation parameters where the Coulomb potential energy of interacting particles exceeds their kinetic energy. These include dense plasmas (ICF, white dwarfs, giant planets, etc.), dusty plasmas and ultracold plasmas. We have developed two theories of transport coefficients for Coulomb collision processes that span weak to strong correlation. The first of these\footnote{Baalrud, POP {\bf 19}, 030701 (2012).} exploits symmetries of the binary collision process to compute transport coefficients directly from the Boltzmann collision operator, instead of applying the small angle scattering approximation that weakly correlated theories are based on. The second,\footnote{Daligault and Dimonte., PRE {\bf 79}, 056403 (2009).} more general, theory is akin to LenardBalescu theory, but with local field corrections that resolve the close interaction limit. Both theories are applied to calculate thermal equilibration rates and friction forces between Maxwellian species, as well as resistivity and thermal conductivity using Spitzer's approach to account for deviations from Maxwellian. The theories are shown to accurately predict coefficients calculated from \textit{ab initio} classical molecular dynamics simulations. [Preview Abstract] 

BP8.00013: Ionic diffusion in plasmas across coupling regimes J. Daligault, S.D. Baalrud Molecular dynamics simulations are used to investigate the diffusion properties of ions in onecomponent plasmas and binary ionic mixtures from the weakly to the strongly coupled regimes. A physically motivated model for the diffusivities is proposed that reproduces the simulation data and gives insight into the nature of ionic motions and interactions in plasmas across the coupling regimes. The model extends the widely used ChapmanSpitzer theory from the weakly to the moderately coupled regime. In the strongly coupled regime, diffusion is modeled in terms of thermally activated jumps between equilibrium positions separated by an energy barrier.\\[4pt] J Daligault, Phys. Rev. Lett. 108, 225004 (2012).\\[0pt] S. Baalrud, Phys. Plasmas 19, 030701 (2012) [Preview Abstract] 

BP8.00014: Velocity Relaxation in a Strongly Coupled Neutral Plasma Trevor Strickler, Georg Bannasch, Jose Castro, Patrick McQuillen, Thomas Pohl, Thomas C. Killian The analytical expressions developed by Landau and Spitzer to describe Coulomb collisions are fundamental to plasma physics, applicable over wide range of plasma conditions. However, in the stronglycoupled plasma regime (Coulomb coupling parameter $>$ 1), the theory underlying the LandauSpitzer formula breaks down, yielding nonsensical values for collision rates. Efforts to extend theory into the strongly coupled regime have not yet led to an agreed upon solution to the problem. Also, because of the short time scales involved, experiments to measure ultrafast relaxation times in a strongly coupled neutral plasma have also remained a challenge. In this work, we present the first direct measurement of velocity relaxation rates in strongly coupled neutral plasmas. Exploiting the very low temperatures in ultracold plasmas, we achieve strong coupling at low densities that permit timeresolved optical diagnostics of velocity relaxation. Already, we have measured relaxation rates with time resolution on the order of 100 ns. Currently, efforts are underway to achieve time resolutions on the order of 10 ns to study nonMarkovian relaxation dynamics. [Preview Abstract] 

BP8.00015: Rapid MultiComponent HNC Calculations for Modelling Warm Dense Matter Matthew Calef, Michael Murillo Xray Thomson Scattering (XRTS) can be an extremely accurate diagnostic for a dense plasma. In such settings one is often interested in the structure of the ions, however the incident electromagnetic energy couples more strongly with, and provides more information about, the electrons. One then must then infer the behavior of the ions by modeling their interaction with the electrons. To facilitate this we have developed a multicomponent arbitrarypotential HNC code that allows one to examine the physics connecting the electron response to XRTS with the underlying ion structure. In particular, we model the effect of multiple ionization states, effective ionion potentials derived from dielectric considerations, and, for certain conditions, explicit electrons interacting with via quantum statistical potentials. We describe and compare several iterative methods for solving the HNC equations rapidly. [Preview Abstract] 

BP8.00016: QuasiLocalized Charge Approximation for Strongly Correlated Plasmas in Traps Hanno K\"ahlert, Michael Bonitz, Gabor Kalman Over the last two decades, the QuasiLocalized Charge Approximation (QLCA) has been successfully applied to investigate the dielectric properties of various strongly coupled systems~[1]. While these earlier studies focused on bulk properties, we are concerned with the application of the QLCA to finite inhomogeneous systems. These situations are commonly encountered in ion trap plasmas, ultracold neutral plasmas, or dusty plasmas. Starting from the microscopic Lagrangian, we derive an equation for the fluid displacement field and compare our results with previous calculations~[2] and a theory for strongly correlated ion plasmas~[3]. Since the QLCA accounts for correlation effects, it improves upon socalled ``coldfluid'' theories and should allow to reduce the discrepancies between the latter and molecular dynamics simulations in a confined Yukawa plasma~[4]. Here, we present our first results.\\[3pt] [1] K. I. Golden and G. J. Kalman, Phys. Plasmas {\bf 7}, 14 (2000)\\[0pt] [2] C.J. Lee and G. J. Kalman, J. Korean Phys. Soc. {\bf 58}, 448 (2011)\\[0pt] [3] D. H. E. Dubin and J. P. Schiffer, Phys. Rev. E {\bf 53}, 5249 (1996), D.~H.~E.~Dubin, Phys. Rev. E {\bf 53}, 5268 (1996)\\[0pt] [4] H. K\"ahlert and M. Bonitz, Phys. Rev. E {\bf 83}, 056401 (2011) [Preview Abstract] 

BP8.00017: Dynamic Modeling of MultiComponent Strongly Coupled Plasmas Using ParticleinCell Simulations David Rose, Dale Welch, Robert Clark, Tom Genoni, Carsten Thoma A threedimensional dynamic simulation model of strongly coupled electronion and multicomponent plasmas is being developed. Based on the particleincell method, the simulations resolve subDebyelength interparticle spacing to accurately model these systems [D. V. Rose, \textit{et al}., Phys. Plasmas \textbf{16}, 102105 (2009)]. The simulation results are in very good agreement with classical hypernetted chain calculations for dense electronion and ionion plasmas. Our results demonstrate the feasibility and utility of largescale particleincell simulations for the modeling and analysis of multicomponent moderately and strongly coupled plasmas. Models for electronimpact ionization and recombination are being developed to follow the time dependent evolution of multicomponent coupled plasmas. Sample results will be presented. [Preview Abstract] 

BP8.00018: Dusty Plasma Physics Facility for the International Space Station John Goree, Inseob Hahn The Dusty Plasma Physics Facility is a proposed instrument for the International Space Station. The proposal, which is prepared by the Jet Propulsion Laboratory, is now under consideration by NASA. The proposed facility is expected to support multiple scientific users selected by NASA Research Announcement. It will have a modular design, with a scientific locker, or insert, that can be exchanged without removing the entire facility. The first insert will be designed for fundamental physics experiments. Possible future inserts could be designed for other scientific purposes, such as experimental simulations of astrophysical or geophysical conditions or engineering studies. The design of the facility will allow remote operation from groundbased laboratories, using telescience. [Preview Abstract] 

BP8.00019: Dynamics of Dust Aggregates in a Complex Plasma Allen Davis, Jorge Carmona Reyes, Lorin Matthews, Truell Hyde Charged dust aggregates play an important role in many astrophysical phenomena, such as early stages of protostellar and protoplanetary growth, the dynamics of planetary rings and cometary tails, and the formation of noctilucent clouds in earth's upper atmosphere. Dust is also expected to be an unwanted byproduct in the operation of plasma fusion devices, such as ITER. In all of these environments, direct study of the dust aggregates in their \textit{in situ} environment is extremely difficult, if not impossible. As a model for these complex plasma environments, dust aggregates are formed in a laboratory plasma as monodisperse spheres are accelerated in a selfexcited dust density wave. Individual dust particles are perturbed using a diode pumped solid state laser (Coherent VERDI) with their motions recorded by a highspeed camera at 1000 fps. Analysis of the particle motion allows determination of the aggregate characteristics which determine the grain dynamics, such as charge, mass, and gas drag. [Preview Abstract] 

BP8.00020: Molecular dynamics simulations of magnetized dusty plasmas Alexander Piel, Torben Reichstein, Jochen Wilms The combination of the electric field that confines a dust cloud with a static magnetic field generally leads to a rotation of the dust cloud. In weak magnetic fields, the Hall component of the ion flow exerts a drag force that sets the dust in rotation. We have performed detailed moleculardynamics simulations of the dynamics of torusshaped dust clouds in anodic plasmas. The stationary flow [1] is characterized by a shell structure in the laminar dust flow and by the spontaneous formation of a shearflow around a stationary vortex. Here we present new results on dynamic phenomena, among them fluctuations due to a KelvinHelmholtz instability in the shearflow. The simulations are compared with experimental results. \\[4pt] [1] T. Reichstein, A. Piel, Phys. Plasmas \underline{18}, 083705 (2011) [Preview Abstract] 

BP8.00021: Low frequency instabilities in dusty magnetized plasmas Marlene Rosenberg Motivated by current and upcoming dusty plasma experiments with large magnetic fields, we consider several electrostatic instabilities that could arise when (1) only the ions and electrons are magnetized, or (2) all the charged particles are magnetized. In the first category, we consider the excitation of dust acoustic type waves by crossfield drifts that may occur due to the presence of an electric field or density inhomogeneities perpendicular to the magnetic field. In the second category, we consider conditions under which electrostatic dust cyclotron (EDC) waves could be excited. We focus on the excitation of higher harmonic EDC waves, since these have shorter wavelengths than the fundamental mode and thus might be more easily accommodated in a dusty plasma device. [Preview Abstract] 

BP8.00022: Interaction of a flowing dusty plasma with a biased wire John K. Meyer, Jonathon R. Heinrich, SuHyun Kim, Robert L. Merlino We have developed methods of producing flowing dusty plasmas with a controllable flow speed. A threedimensional dusty plasma is formed by suspending micronsized glass spheres in a DC glow discharge plasma in argon at P $\sim $ 150 mTorr. Dust flows up to supersonic speeds (relative to the dust acoustic speed) have been obtained. We are investigating the interaction of this flowing dusty plasma with a circular cylinder (electrically biased wire). When the wire is biased below the plasma potential, a cylindrical void is formed around the wire within which the dust is excluded. The dust flows around the void boundary. For supersonically flowing dust, a bow shock is formed in front of the object, with an extended wake on the downstream side. The flow of dust around the void has been studied at the individual particle level using high speed video imaging. [Preview Abstract] 

BP8.00023: Simulation of the Taylor Instability in a Loosely Coupled Dusty Plasma Katherine Pacha Lord Rayleigh showed that the interface between two fluids of different densities, with the dense fluid above a fluid of lesser density, is unstable to the growth of downward moving irregularities which develop into fingerlike structures. In turn, Taylor showed that this situation is equivalent to one in which a lighter fluid is accelerated into a heavier fluid. I used a (2D) general hydrodynamic code, to model the Rayleigh Taylor Instability in a loosely coupled dusty plasma using the conditions from [1]. Other aspects of the instability were studied such as the effect of shear in how the instability starts, the formation of the bubbles, and the turbulent state. \\[4pt] [1] K. Pacha, et. al, Phys. Plasmas \textbf{19}, 014501 (2012). [Preview Abstract] 

BP8.00024: Experimental Determination of Horizontal Confinement Within a Glass Box in a GEC RF Reference Cell Angela Douglass, Robert Moore, Lorin Matthews, Truell Hyde Recent experiments have demonstrated that new and interesting phenomena are observed when dust particles are confined within a glass box in a GEC RF reference cell. The addition of the glass box to the lower, powered electrode of the cell allows for the formation of structures such as Coulomb balls or single, onedimensional vertical chains. While many experiments have been performed on these structures, little is known about the horizontal confinement created by the glass box. In this experiment, a single particle was perturbed with a laser in order to characterize the horizontal confinement due to the glass box. The shape of the confinement will be presented for various plasma powers, pressures, and heights above the lower electrode. [Preview Abstract] 

BP8.00025: Spatial evolution of the dust acoustic wave Jeremiah Williams A complex (dusty) plasma is a fourcomponent system composed of ions, electrons, neutral particles and charged microparticles. The presence of the microparticles gives rise to new plasma phenomena, including collective modes such as the dust acoustic wave. The dust acoustic wave mode has been the subject of intense experimental and theoretical study since being predicted in 1990 and identified experimentally in 1994. In this work, high speed video imaging is employed to measure of the evolution of wave fronts of a propagating dust acoustic wave as it propagates through a weaklycoupled dusty plasma system in an argon, dc glow discharge plasma. In particular, measurements of the growth, saturation and then damping of the wave mode as the wave propagates through the cloud are reported. It is observed that the wave amplitude initially exhibits rapid growth while the wave front compresses. After this initial growth, the width of the wave front remains relatively constant while the amplitude of the wave front evolves like the background dust medium. In some cases, it is also observed that the wave amplitude can decay more quickly than the background dust medium. [Preview Abstract] 

BP8.00026: NONLINEAR PHENOMENA AND TURBULENCE EXPERIMENT 

BP8.00027: Investigation of current sheet disruptions using laserproduced diamagnetic bubbles Stephen Vincena, Walter Gekelman, Pat Pribyl Rapid temporal changes in the magnetic field topology of currentcarrying plasmas can enhance or disrupt these currents and trigger magnetic reconnection. A clear natural example of this can be found in the earth's magnetotail during a magnetic substorm. In this laboratory study, preliminary results are presented of an effectively steadystate current sheet which is disrupted by the production of an impulsive diamagnetic bubble. The process is impulsive in that it occurs on a timescale less than the ion cyclotron period. The experiments are performed on UCLA's Large Plasma Device (LAPD). This is a linear device with $L$=17m, $d$=60cm, 300G$< B_{0}<$2kG, n$_{e}$=$2\times10^{12}$cm$^{3}$, $T_{e}$=6eV,$T_{i}\approx$1eV, and He, H, or Ar). The diamagnetic cavity is produced by a pulsed (8ns, 1J) Nd:YAG lasersolid target ablation. The current sheet is produced using a $CeB_{6}$ cathode, embedded within the main plasma column,($h$=10cm, $w$=1cm). In the current sheet, the plasma has higher density, $n\approx 4\times 10^{12}$cm$^{3}$, yielding scaled crossfield dimensions of $h=0.9c/\omega_{pi}$ and $w=3.8c/\omega_{pe}$ for a H plasma. Results will be presented which include fast camera imaging, magnetic field probe data, and the resulting time varying currents during the event. [Preview Abstract] 

BP8.00028: Stimulated Parametric Decay of Large Amplitude Alfv{\'e}n waves in the Large Plasma Device (LaPD) S. Dorfman, T. Carter, P. Pribyl, S.K.P. Tripathi, B. Van Compernolle, S. Vincena Alfv{\'e}n waves, the fundamental mode of magnetized plasmas, are ubiquitous in lab and space. While the linear behaviour of these waves has been extensively studied, nonlinear effects are important in many real systems. In particular, a parametric decay process in which a large amplitude Alfv{\'e}n wave decays into an ion acoustic wave and backward propagating Alfv{\'e}n wave may be key to the spectrum of solar wind turbulence. The present laboratory experiments aim to stimulate this process by launching counterpropagating Alfv{\'e}n waves from antennas placed at either end of the Large Plasma Device (LaPD). The resulting beat response has many properties consistent with an ion acoustic wave including: 1) The beat amplitude peaks when the frequency difference between the two Alfv{\'e}n waves is near the value predicted by Alfv{\'e}nion acoustic wave coupling. 2) This peak beat frequency scales with antenna and plasma parameters as predicted by three wave matching. 3) The beat amplitude peaks at the same location as the magnetic field from the Alfv{\'e}n waves. 4) The beat wave is carried by the ions and propagates in the direction of the higherfrequency Alfv{\'e}n wave. Strong damping observed after the pump Alfv{\'e}n waves are turned off is under investigation. [Preview Abstract] 

BP8.00029: Electron streams formation and secondary two stream instability onset in the postsaturation regime of the classical Weibel instability M.E. Innocenti, Giovanni Lapenta, Stefano Markidis, Marian Lazar, Stefaan Poedts The electrostatic activity in the postsaturation regime of the velocity anisotropy driven Weibel instability is investigated by means of 1D 3V particle in cell simulations. Two different initial simulation configurations have been chosen to characterize the electrostatic activity in the postsaturation stage. A secondary two stream instability arises in both cases. However, significant differences occur in the thickness of the electron streams, in their initial locations, and in their effects on the bulk electron phase space distribution. An Hamiltonian description of particle motion in a 1D setting explains these differences in terms of the effective potential experienced by particles as a function of their initial perpendicular velocity. The different roles of the longitudinal electric field and the Lorentz force in the formation of electron streams are discussed. M.E. Innocenti et al, PoP, 18, 052104 (2011). [Preview Abstract] 

BP8.00030: Selfregulating Drift wave  Zonal Flow turbulence in a linear plasma device Jinlin Xie, Ran Chen, Guanghai Hu, Xiaoli Jin, Hong Li, Wandong Liu, Changxuan Yu Here we report new and interesting results about the DWZF system in a linear plasma device with much better control environments to illustrate important Zonal flow physics: (1) The threedimensional spectral features of the LFZF have been provided. In particular, it is identified that the LFZF damping is dominated by ionneutral collision in our case. Also experimental evidence of the shearing effect of ZF on DW has been given. (2) A zonal flow dominated state of the DWZF system has been achieved. Theoretically, it has been predicted that a significant portion of the turbulence energy can be stored in the Zonal Flows for the case of low collisionality plasmas. In our experiments we achieve a zonal flow dominated state, in which the maximum ratio of the ZF energy to the total turbulence energy is about 80{\%}, which seems to support the hypothesis of zonostropic state in geostrophic turbulence. (3) The selfregulating dynamics in the DWZF system is clearly elucidated. The evolution of the energy partition ratio of driftwave turbulence and zonal flow is investigated with varying magnetic field strength, which is found consistent with the general preypredator model. [Preview Abstract] 

BP8.00031: Optimal ClosedLoop Control of the Azimuthal Velocity Profile in HELCAT by E$\times $B Actuation Zeki Ilhan, David HuxleyCohen, Jason Barry, Eugenio Schuster, Mark Gilmore, Andrew Ware The crossfield turbulencedriven particle transport in magnetically confined plasmas can be reduced by adequate shaping of the azimuthal flow profile. An openloop extremumseeking controller has been designed earlier to identify radial azimuthal flow profiles associated with low RMS fluctuations in a magnetized laboratory device (HELCAT). In this work we propose a modelbased feedback controller that can regulate the radial azimuthal velocity profile around a prescribed lowfluctuation profile. The governing partial differential equation for the azimuthal flow is reformulated into a reducedorder, control oriented model by using truncated Taylor Series expansion. Statespace and linear quadratic control methods are then used to come up with an optimal, feedback control law that can minimize both the tracking error and the control energy. Computer simulations reflect the effectiveness of the proposed controller as a tool to clarify the physics of laboratory plasmas. [Preview Abstract] 

BP8.00032: Review and perspectives of electrostatic turbulence and transport studies in the basic plasma physics device TORPEX Fabio Avino, Alexandre Bovet, Ambrogio Fasoli, Ivo Furno, Kyle Gustafson, Joaquim Loizu, Paolo Ricci, Christian Theiler TORPEX is a basic plasma physics toroidal device located at the CRPPEPFL in Lausanne. In TORPEX, a vertical magnetic field superposed on a toroidal field creates helicoidal field lines with both ends terminating on the torus vessel. We review recent advances in the understanding and control of electrostatic interchange turbulence, associated structures and their effect on suprathermal ions. These advances are obtained using highresolution diagnostics of plasma parameters and wave fields throughout the whole device crosssection, fluid models and numerical simulations. Furthermore, we discuss future developments including the possibility of generating closed field line configurations with rotational transform using an internal toroidal wire carrying a current. This system will also allow the study of innovative fusionrelevant configurations, such as the snowflake divertor. [Preview Abstract] 

BP8.00033: Initial results from the Controlled Shear Decorrelation eXperiment  Upgrade (CSDXU) Saikat Chakraborty Thakur, Ty Lee, Min Xu, Lang Cui, Peter Manz, Nicolas Fedorczak, Chris Holland, George Tynan Controlled Shear Decorrelation eXperiment (CSDX) is a linear plasma device dedicated to studies of drift wave turbulence zonal flow interaction and generation of intrinsic rotation in a simple plasma configuration. Previous studies in argon plasma, with a 13.56 MHz, 1.5 kW, 10 cm diameter RF helicon source, immersed in 1 kG magnetic field, demonstrated existence of a turbulence driven azimuthally symmetric radially sheared plasma flow (i.e., a zonal flow). To better understand the underlying mechanism of the emission, propagation and absorption of drift wave packets into the zonal shear layer, the machine has been upgraded. The upgrade includes a larger (15 cm diameter) helicon source, larger RF power (up to 5 kW) and larger magnetic field (up to 2.4 kG) to be used with lighter gases (neon, helium and hydrogen). Diagnostics include Langmuir probe arrays, optical emission spectroscopy and fast framing camera. Initial measurements of the radial profiles of density and potential fluctuations, Reynold's stresses and other time averaged plasma parameters will be shown. [Preview Abstract] 

BP8.00034: Dynamics of Turbulence Suppression in a Helicon Plasma Tiffany Hayes, Mark Gilmore Experiments are currently being conducted in the the HeliconCathode Device (HelCat) at the University of New Mexico. The goal is to the study in detail the transition from a turbulent to a nonturbulent state in the presence of flow shear. HelCat has intrinsic fluctuations that have been identified as driftwaves. Using simple electrode biasing, it has been found that these fluctuations can be completely suppressed. In some extreme cases, a different instability, possibly the KelvinHelmholtz instability, can be excited. Detailed studies are underway in order to understand the characteristics of each mode, and to elucidate the underlying physics that cause the change between an unstable plasma, and an instabilityfree plasma. Dynamics being observed include changes in flow profiles, both azimuthal and parallel, as well as changes in potential and temperature gradients. Further understanding is being sought using several computer codes developed at EPFL: a linear stability solver (LSS,\footnote{P. Ricci and B.N. Rogers (2009). Phys Plasmas 16, 062303.} a onedimensional PIC code/sheath solver, ODISEE,\footnote{J. Loizu, P. Ricci, and C. Theiler (2011). Phys Rev E 83, 016406} and a global, 3D Braginski code, GBS.\footnote{Ricci, Rogers (2009)} A basic overview of results will be presented. [Preview Abstract] 

BP8.00035: Experimental Measurement of the Nonlinear Interaction between Counterpropagating Alfv\'{e}n Waves in the LaPD J.W.R. Schroeder, D.J. Drake, G.G. Howes, F. Skiff, C.A. Kletzing, T.A. Carter, S. Dorfman, D. Auerbach Turbulence plays an important role in the transport of mass and energy in many space and astrophysical plasmas ranging from galaxy clusters to Earth's magnetosphere. One active topic of research is the application of idealized Alfv\'{e}nic turbulence models to plasma conditions relevant to space and astrophysical plasmas. Alfv\'{e}nic turbulence models based on incompressible magnetohydrodynamics (MHD) contain a nonlinear interaction that drives the cascade of energy to smaller scales. We describe experiments at the Large Plasma Device (LaPD) that focus on the interaction of an Alfv\'{e}n wave traveling parallel to the mean magnetic field with a counterpropagating Alfv\'{e}n wave. Theory predicts the nonlinear interaction of the two primary waves will produce a secondary daughter Alfv\'{e}n wave. In this study, we present the first experimental identification of the daughter wave generated by nonlinear interactions between the primary Alfv\'{e}n waves. [Preview Abstract] 

BP8.00036: Studies of Turbulence, Transport and Flow in the Large Plasma Device Troy Carter, David Schaffner, Giovanni Rossi, Brett Friedman, Maxim Umansky, Daniel Guice, Steve Vincena, Jim Maggs, Milo Taylor, Joseph Gibson, Eli Haims The LArge Plasma Device (LAPD) at UCLA is a 17~m long, 60~cm diameter magnetized plasma column with typical plasma parameters $n_e \sim 1\times 10^{12}$cm$^{3}$, $T_e \sim 10$eV, and $B \sim 1$kG. Recently, the capability to continuously vary the edge flow and flow shear has been developed in LAPD using biasing of an annular limiter. Spontaneous flow is observed in the ion diamagnetic direction (IDD), biasing tends to drive flow in the opposite direction, allowing a continuous variation of flow from the IDD to the electron diamagnetic direction, with nearzero flow and flow shear states achieved along the way. Enhanced confinement and density profile steepening is observed with increasing shearing rate; degraded confinement is observed at nearzero shear. Particle flux and radial correlation length are observed to decrease with increasing shear. The decrease occurs with shearing rates which are comparable to the inverse turbulent autocorrelation time in the zero flow state. LAPD turbulence has been modeled using the 3D Braginskii fluid turbulence code BOUT++. Good qualitative and semiquantitative agreement is found between BOUT++ simulations and LAPD experimental measurements. [Preview Abstract] 

BP8.00037: Modifications to intermittent turbulent structures by sheared flow in LAPD Giovanni Rossi, David Schaffner, Troy Carter, Danny Guice, Roger Bengtson Turbulence in the edge of the Large Plasma Device is generally observed to be intermittent with the production of filamentary structures. Densityenhancement events (called ``blobs'') are localized to the region radially outside the edge of the cathode source while densitydepletion events (called ``holes'') are localized to the region radially inward. A flowshear layer is also observed to be localized to this same spatial region. Control over the edge flow and shear in LAPD is now possible using a biasable limiter. Edge intermittency is observed to be strongly affected by variations in the edge flow, with intermittency (as measured by skewness of the fluctuation amplitude PDF) increasing with edge flow (in either direction) and reaching a minimum when spontaneous edge flow is zeroedout using biasing. This trend is counter to the observed changes in turbulent particle flux, which peaks at low flow/shear. Twodimensional crossconditional averaging confirms the blobs to be detached filamentary structures with a clear dipolar potential structure and a geometry also dependent on the magnitude of sheared flow. More detailed measurements are made to connect the occurrence of these blobs to observed flowdriven coherent modes and their contribution to radial particle flux. [Preview Abstract] 

BP8.00038: Coherent Phase Events in 2D Turbulence J.M. ReynoldsBarredo, D.E. Newman, P.W. Terry, R. Sanchez Interesting dynamics are found in the phase of Fourier modes in 2D turbulence simulations. The equations investigated can represent either 2D plasma drift wave turbulence or quasigeostrophic turbulence. The interesting dynamics are found to be caused by the appearance of strong coupling in the phase of the Fourier modes. This happens in regions inside the highk region of the spectrum where dissipation is dominant. In addition, a strong burst of energy transfer is associated with the phasecoupling event. Finally, these intermittent events can be shown to have strong connections with the saddle points of the velocity field. The mechanisms, importance and possible uses of these coherent events and their relation with the saddle points of the velocity field will be discussed. [Preview Abstract] 

BP8.00039: Turbulent transport and heating of trace heavy ions in hot, magnetized plasmas Michael Barnes, Felix Parra, William Dorland Heavy ions are present in hot, magnetized plasmas both in laboratory experiments and in nature. These ions are important in numerous contexts: main ion properties are often inferred from heavy ion measurements because heavy ions radiate more readily; accumulation of heavy ions leads to dilution and increased radiative energy losses in magnetic confinement fusion; and temperature measurements of minority ions in space and astrophysical plasmas indicate the existence of a novel massdependent heating mechanism. We present a derivation of scaling laws for the transport and heating of trace heavy ions in low frequency, magnetized plasma turbulence. The predicted dependences of turbulent fluxes and heating on ion charge and mass number are shown to agree with numerical results from nonlinear gyrokinetic simulations of both stationary and differentially rotating plasmas. Heavy ion momentum transport is found to increase with mass, and heavy ions are preferentially heated, implying a massdependent ion temperature for very weakly collisional plasmas and for partially ionized heavy ions in strongly rotating plasmas. These predictions are consistent with temperature measurements in the solar wind and indicate that errors may be present in ion temperature measurements in experiment. [Preview Abstract] 

BP8.00040: PLASMA WAVES 

BP8.00041: Whistler wave excitation from a dipole antenna in the NRL Space Physics Simulation Chamber David Blackwell, Erik Tejero, William Amatucci, Christopher Cothran, David Walker A dipole has large radiation resistance at resonances associated with odd half integral wavelengths matching the overall antenna length. The first, and strongest resonance, is when $kl=\pi/2$, with $k$ the wavenumber and $l$ the length of one dipole arm. Half and quarterwave dipoles and monopoles operate in such a manner to achieve good radio transmission and reception. At NRL's Space Physics Simulation Chamber, we have been investigating how this seemingly simple behavior is carried over, or not, when the antenna is immersed in a magnetized plasma. Short wavelength waves above the plasma frequency have been observed to have resonances with the driving antenna exactly as the halfwavelength dipole model predicts. However, the lower frequency short wavelength whistler mode resonance has not been observed, despite overlap of the measured wavelength with the resonance condition when whistler waves are excited. To address this inconsistency, we present a comparison between recent theoretical and experimental results with 2D spectral analysis and measurements of the antenna impedance for different antenna geometries and plasma conditions. It is expected that these observations will provide insight into the design of a resonant antenna for generating large amplitude whistler waves. [Preview Abstract] 

BP8.00042: Lower hybrid to whistler mode conversion on a density striation Enrico Camporeale, Gian Luca Delzanno, Patrick Colestock When a wave packet composed of short wavelength lower hybrid modes traveling in an homogeneous plasma region encounters a density inhomogeneity, it can resonantly excite long wavelength whistler waves via a linear mechanism known as mode conversion. We study the linear mode conversion using a scalarfield formalism (in the limit of cold plasma linear theory) which we solve numerically [1]. We show that the linear mode conversion can effectively transfer a large amount of energy from the short to the long wavelength modes, and we study how the efficiency scales for different width and amplitude of the density striation. We present a general criterion for the width of the striation that, if fulfilled, maximizes the conversion efficiency. Such a criterion could provide an interpretation of recent laboratory experiments carried out on the Large Plasma Device at UCLA. \\[4pt] [1] E. Camporeale, G.L. Delzanno, P. Colestock, ``Lower hybrid to whistler mode conversion on a density striation,'' submitted to Journal of Geophysical Research (2012). [Preview Abstract] 

BP8.00043: Systematic effects of Alfv\'{e}n waves on whistler mode transmission Fred Skiff, J. Schroeder, J.D. Drake, G.G. Howes, C.A. Kletzing, T.A. Carter, S. Dorfman, D. Auerbach We study the systematic effects on whistler mode transmission measurements caused by shear Alfv\'{e}n waves in the LAPD plasma device with the goal of detecting the plasma dielectric response and electron acceleration along the magnetic field. Alfv\'{e}n waves with $\delta $B/B$\sim $ 10$^{5}$ are generated using an arbitrary spatial waveform antenna adjusted to produce plane waves in the central region of the plasma with a perpendicular wavelength comparable to the collisionless skin depth. In the overdense ($\omega _{p}$/$\omega _{c} \sim $ 23) LAPD plasma with B=1800 G, the whistler mode is the only wave propagating parallel to the magnetic field just below the electron cyclotron frequency. Whistler mode absorption has previously been used successfully to measure the electron temperature, but here we observe systematic changes to the whistler transmission signal caused by the Alfv\'{e}n wave. We will discuss the problems of separating out the effect of changes in the plasma density (including ducting) with measurements of the perturbed electron velocity distribution. [Preview Abstract] 

BP8.00044: Undamped electrostatic plasma waves Francesco Valentini, Denise Perrone, Francesco Califano, Francesco Pegoraro, Pierluigi Veltri, Philip Morrison, Thomas O'Neil Dissipationless wave damping is a characteristic feature of plasma dynamics. However, when the equilibrium particle velocity distribution departs from the usual Maxwellian configuration due to the presence of a small plateau, plasma waves with certain frequency and wavenumber can survive against Landau damping: we name these waves ``corner modes'' since a significant contribution to the charge density associated to these oscillations mainly come from the sharp corners at the boundary of the velocity plateau. Here we show that these undamped waves can be obtained in a wide region of the $(k; \omega_R)$ plane ($\omega_R$ being the real part of the wave frequency and $k$ the wavenumber), away from the wellknown ``thumb curve'' for Langmuir waves and EAWs based on the Maxwellian. The effect of altering the tails of the velocity distribution on the thumb curve is also discussed and a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting recent experimental observations of electrostatic waves in nonneutral plasmas. Kinetic VlasovPoisson simulations are specifically designed to provide support to the analytical predictions. [Preview Abstract] 

BP8.00045: Low frequency electrostatic waves in a magnetized plasma with heavy negative ions SuHyun Kim, John K. Meyer, Robert L. Merlino We have observed large amplitude, low frequency (well below any cyclotron or plasma frequencies) electrostatic waves in a magnetized Qmachine plasma containing positive potassium ions (39 amu), electrons, and heavy negative ions (350 amu). The negative ions were produced by leaking $C_7 F_{14} $ (perfluoromethylcyclohexane) vapor into the Qmachine. $C_7 F_{14} $ has a large attachment rate for low energy electrons (in the Qmachine, $T_e \approx 0.2\,\,\mbox{eV})$, so that a relatively large fraction (${n_ } \mathord{\left/ {\vphantom {{n_ } {n_e }}} \right. \kern\nulldelimiterspace} {n_e }>10^3)$ of magnetized $C_7 F_{14}^ $ negative ions are formed at neutral pressures $\approx 10^{5}$Torr. The waves propagate in the azimuthal direction of the cylindrical plasma column. The frequency spectrum of the waves contains narrow features at the fundamental (m=1) and several harmonics. Possible excitation mechanisms being considered are the negative ionmodified drift instability driven by the radial density gradient, and radial shear in the azimuthal ($\vec {E}\times \vec {B})$ drift velocity. [Preview Abstract] 

BP8.00046: Two Stream Instability in Magnetized Warm Plasma under the Ionization Effect  Jyoti, Hitendra K. Malik Two  stream instability is considered in the presence of magnetic field in inhomogeneous plasma. The continuity and the momentum equation which take into account the ionization constant are formulated for ions and the electrons including the effect of finite temperature of ions along with the ionization effect. Using normal mode analysis along with linear approximation, potential is found from Poisson's equation neglecting higher order perturbed terms. The behavior of growth rate with magnetic field and the propagation angle along with ionization constant has been studied with different plasma oscillation wavelength to Debye length ratio for both the laboratory as well as the space plasma parameters. We observe two types of instability in both the cases. In case of laboratory plasma one of the instability is growing at larger plasma oscillation wavelength and another one at lower wavelength while in the case of space plasma both the instabilities grow only at smaller plasma oscillation wavelength but with different growth rates. All the instabilities has higher growth rate at smaller wave length of oscillations. Effect of finite ion temperature is studied with respect to different electron temperature both in the laboratory as well as in space plasma. [Preview Abstract] 

BP8.00047: Alfv\'{e}n Wave Propagation in Strongly Inhomogeneous Partially Ionized Plasmas in the \textit{Hot hELicon eXperiment (HELIX)} Stephanie Sears, Jerry Carr Jr., Matthew Galante, Richard Magee, Dustin McCarren, Gregory Lusk, Robert VanDervort, Earl Scime Alfv\'{e}n wave damping is one of the most important mechanisms for understanding ion heating in the solar corona. The presence of ionneutral collisions in partially ionized plasmas, such as the chromosphere, has a significant but not wellunderstood effect on Alfv\'{e}n wave propagation and energy transfer. Since the neutral density in HELIX varies strongly with radius, a wide range of Alfv\'{e}n dynamics can be studied across the plasma column and the effects of changing the ionneutral collision frequency can be observed. The ratio of the ionneutral collision frequency to the ioncyclotron frequency in HELIX varies from about 0.02 to 0.5 across the plasma column. In the solar atmosphere this ratio varies from approximately 10$^{6}$ to 10.$^{ }$ With the use of a lowfrequency wavelaunching antenna and a smallscale (smaller than the ion gyroradius) magnetic sense coil probe, the behavior of radially confined Alfv\'{e}n waves is measured and characterized. These observations, coupled with LIF measurements of the plasma temperature and drift, are compared to observations in the corona. [Preview Abstract] 

BP8.00048: Excitation of waves by a spiraling ion beam in a large magnetoplasma Shreekrishna Tripathi, Bart Van Compernolle, Walter Gekelman, Patrick Pribyl, William Heidbrink, Troy Carter A helium ion source (25 kV, 5 A, 0.3 Hz rep rate, 0.51.5 ms pulsewidth) has been constructed for performing the fusionrelevant fastion studies on the Large Plasma Device (LAPD). The ion source comprises a hotcathode LaB$_6$ plasma source, a multiaperture threegrid beam extractor, power supplies, and neutral pumping system. The beam is injected from the end of the device with variable injection angles and it spirals down the LAPD plasma (n$\sim$10$^{11}$ cm$^{3}$, T$_e\sim$0.4 eV, B = 0.5  1.8 kG) radiating a multitude of waves in the drift, shear Alfven, ion cyclotron, and lower hybrid frequency ranges. The beam profiles are measured at several axial locations (up to 12 m from the deaccel grid) using a fastion collector. Measurements have confirmed the production of a lowdivergence ion beam that forms helical orbits during oblique injection. Initial results on the beamdriven lowfrequency waves ($f < f_{lh}$), with a particular emphasis on Alfven waves, will be presented. [Preview Abstract] 

BP8.00049: Ion beam generated modes in the lower hybrid frequency range in a laboratory magnetoplasma Bart Van Compernolle, Shreekrishna KP Tripathi, Walter Gekelman, Patrick Pribyl, Patrick Colestock The interaction of a fast ion beam with a low $\beta$ plasma has been studied in the laboratory. Experiments were performed at the LArge Plasma Device (LAPD) at UCLA. The experiments were done in a Helium plasma ($n \simeq 10^{12} \ \mbox{cm}^{3}$, $B_0$ = 1000 G  1800 G, $f_{pe}/f_{ce} \simeq 1  5$, $T_e = 0.25\ \mbox{eV}$, $v_{te} \ll v_A$). The ion beam is a Helium beam with energies ranging from 5 keV to 18 keV. The fast ion velocity is on the order of the Alfv\'en velocity. The beam is injected from the end of the machine, and spirals down the linear device. Waves were observed below $f_{ci}$ in the shear Alfv\'en wave regime, and in a broad spectrum above $f_{ci}$ in the lower hybrid frequency range, the focus of this paper. The wave spectra have distinct peaks close to ion cyclotron harmonics, extending out to the 100th harmonic in some cases. The wave generation was studied for various plasma parameters, as well as for different beam energies and pitch angles. The waves were measured with 3axis electric and magnetic probes. Detailed measurements of the perpendicular mode structure will be shown. Langmuir probes were used to measure density and temperature evolution due to the beamplasma interaction. Retarding field energy analyzers captured the ion beam profiles. [Preview Abstract] 

BP8.00050: Nonlinear ion acoustic waves in multiion species plasmas at low electron to ion temperature ratios Thomas Chapman, Richard Berger, Edward Williams, Bruce Cohen, Stephan Brunner The nonlinear evolution of ion acoustic waves in multiion species plasmas is studied in the context of stimulated Brillouin scattering. With the aid of Vlasov simulations, multiwavelength systems are investigated over a range of ratios of electron to ion temperatures relevant to current inertial confinement fusion experiments. The impact of nonlinear effects, such as harmonic generation, ion acoustic wave decay and both electron and ion trapping, and the interplay between the comparably damped fast and slow ion acoustic wave modes are demonstrated. \it{This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DEAC5207NA27344 and funded by the Laboratory Research and Development Program at LLNL under project tracking code 12ERD061.} [Preview Abstract] 

BP8.00051: Drift and ion sound instabilities of the magnetic field aligned shear flow with inhomogeneous ion temperature Volodymyr Mykhaylenko, Hae June Lee, Volodymyr S. Mykhaylenko, Mark Koepke The effects of the ion temperature gradient across the magnetic field on the development of the drift and ionsound shear flow modified and shear flow driven instabilities of the magnetic field aligned shear flow are studied analytically and numerically on the ground of a kinetic approach. The cases of cold and hot ions with respect to electrons are considered. Dominant excitation mechanisms (ionkinetic, electronkinetic, and hydrodynamic) of each instability is determined in different domains of the wave number space, velocity shearing rate and temperature ratio of the ions and electrons. Applications of the developed theory to fusion and space plasmas are given. [Preview Abstract] 

BP8.00052: Lagrangian model for interactions of nonlinear waves in inhomogeneous nonstationary plasma I.Y. Dodin, N.J. Fisch Asymptotic Lagrangian equations of nonlinear geometrical optics (GO) are extended to describe multiplewave coupling, particularly in application to Raman backscattering. The equations preserve conservative form in the presence of nonlinear frequency shifts, with both spatial and temporal gradients allowed in the bulk plasma. That, and also the fact that nonlinear splitting of group velocities is retained, renders the model more accurate than the popular GO limit of the nonlinear WignerMoyal equation. [Preview Abstract] 

BP8.00053: Theoretical and numerical studies of wavepacket propagation in tokamak plasmas ZhiXin Lu, Fulvio Zonca, Alessandro Cardinali Theoretical and numerical studies of wavepacket propagation are presented to analyze the time varying 2D mode structures of electrostatic fluctuations in tokamak plasmas, using general flux coordinates. Instead of solving the 2D wave equations directly, the solution of the initial value problem is obtained, following the propagation of wavepackets generated by a source and reconstructing the time varying field. As application, the 2D WKB method is applied to investigate the shaping effects of tokamak geometry on the lower hybrid wave propagation and absorption. Meanwhile, the mode structure decomposition (MSD) method is used to handle the boundary conditions and simplify the 2D problem, casted into two nested 1D problems. The MSD method reduces to the wellknown ``ballooning formalism'' when spatial scale separation applies. This method is used to investigate the time varying 2D electrostatic ITG mode structure with a mixed WKBfull wave technique. The time varying field pattern is reconstructed and the time asymptotic structure of the wavepacket propagation gives the 2D eigenmode and the eigenvalue. As a general approach to investigate 2D mode structures, our method also applies for waves with general source/sink terms, either by an antenna or nonlinear wave interaction. [Preview Abstract] 

BP8.00054: Adiabatic description of long range frequency sweeping Boris Breizman, Robert Nyqvist, Matthew Lilley A theoretical framework is developed to describe long range frequency sweeping events in the 1D electrostatic bumpontail model with fast particle sources and collisions. The model includes three collision operators (Krook, drag (dynamical friction) and velocity space diffusion), and allows for a general shape of the fast particle distribution function. The behavior of phase space holes and clumps is analyzed, and the effect of particle trapping due to separatrix expansion is discussed. With a fast particle distribution function whose slope decays above the resonant phase velocity, hooked frequency sweeping is found for holes in the presence of drag collisions alone. [Preview Abstract] 

BP8.00055: CrossMagneticField Flow Driven by Lower Hybrid Waves in LHCD Xiaoyin Guan, Hong Qin CrossMagneticField flow of electrons can be driven by lower hybrid waves during LHCD. The magnitude of the flow is calculated through quasilinear theory. The Lorentz force at toroidal direction caused by the flow is large enough to be considered as the momentum source of spontaneous plasma rotation observed during LHCD. This work is supported by the U.S. Department of Energy (DEAC0209CH11466) [Preview Abstract] 

BP8.00056: A Preliminary Basic Experiment on the Production and Identification of Toroidal ETG Modes Vladimir Sokolov, Abed Balbaky, Amiya K. Sen Production and identification of the slab branch of the Electron Temperature Gradient (ETG) mode and the measurement of the consequent electron thermal conductivity have been successfully made in a basic experiment in Columbia Linear Machine (CLM) [1,2]. A preliminary experiment on the transition of the slab mode to the toroidal (curvature) branch of ETG mode in CLM is reported. CLM was operated in the mirror configuration with cell length (50cm100cm) and mirror ratio (12.2). The radius of curvature is $R_c \sim 1.3m$ and the critical ratio for the transition to toroidal mode has been achieved, ${k_\} / 2 {\varepsilon}{_n}{k_\perp}< 0.1$ [3]. We first excite the slab ETG mode [1] and gradually increase the magnetic curvature drive by increasing the magnetic mirror ratio, and observe an increase of the ETG mode amplitude up to 2 times and a small change in mode frequency. Alternatively, we can shorten the mirror cell length via moving the mirror coil to increase the bounce average curvature drive and the mode amplitude. \\[4pt] [1] X.Wei, V.Sokolov, and A.K. Sen, Phys. Plasmas 17, 042108 (2010).\\[0pt] [2] V.Sokolov, and A.K. Sen, Phys. Rev. Lett. 107, 155001 (2011).\\[0pt] [3] J.Y.Kim and W.Horton, Phys.Fluids B 3, 1167 (1991). [Preview Abstract] 

BP8.00057: High Order Vlasov Solvers for the Simulation of KEEN Wavea Including the LB and FP Collision Models Eric Sonnendrucker, Nicolas Crouseilles, Bedros Afeyan Since the discovery of KEEN waves in 2002, it has been an open question whether the detailed phase space structures found in those well resolved simulations of Afeyan et al., would survive (essentially) intact, if instead of cubic splines, higher order interpolation schemes were used, up to spectral accuracy. In this work, the VlasovPoisson system is solved using FourierFourier descriptions in phase space, and Fourier spline. The splines can be any order approaching spectral accuracy quickly. These simulations show what the role of numerical dissipation is for the stable simulation of driven KEEN waves, how delicate structures found in low order simulations survive and persist even when the microscope with which they are being scrutinized is much more powerful. The Fourier capability also allows truncated descriptions for the theoretical advancement of reduced models of fully formed KEEN waves, as described previously by Afeyan et al. The partitioned phase space structures they found is further tested by the use of a LenardBernstein collision model on the way to including the full Fokker Planck collision operator in cylindrical (in velocity space) geometry, advanced by Greengard et al. [Preview Abstract] 

BP8.00058: Using a Kortewegtype model for modeling surface tension and its applications Wangyi Liu, John Barnard, Alice Koniges, Dave Eder, Alex Friedman, Aaron Fisher, Nathan Masters The Korteweg model is a relatively old but seldominvestigated model for numericallysurface tension. We present some advanced applications of this model:wave propagation and thinfilm flow. The results will be benchmarked against their analytic solution. In addition, we will investigate the performance of the model in fullscale expanding flow that breaks into droplets as the material enters the twophase. The conjunction of this method with ALEAMR will also be presented. Work performed under the auspices of the U.S. Department of Energy uncontract DEAC5207NA27344 at LLNL, and University of CaliforniaDEAC0205CH11231 at LBNL. [Preview Abstract] 

BP8.00059: Gyrokinetic Particle Simulation of Alfven Eigenmodes with Zonal Fields Zhixuan Wang Effects of collective Shear Alfven wave instabilities on the energetic particle confinement in tokamak depend ultimately on the nonlinear evolution of the turbulence with spontaneously generated zonal fields (zonal flows and zonal currents). In this work, we study nonlinear interaction of Alfv\'en eigenmodes with zonal fields using global gyrokinetic toroidal code GTC. Linear electrostatic simulations in the cylindrical geometry showed that ion temperature gradient instability is observed to be suppressed when ExB flow shear is strong enough. A good agreement has also been achieved between our simulation result of kinetic Alfv\'en wave and LAPD experimental result. Now we are doing TAE (torodicityinduced Alfv\'en eigenmodes) simulation using the DIIID equilibrium data. Linear simulation results agree well with experimental data. Nonlinear results will be shown, including frequency chirping and the interaction between zonal fields and TAEs. [Preview Abstract] 

BP8.00060: GeFi Particle Simulation of Landau Damping and Current Drive of Lower Hybrid Waves Lei Qi, Xueyi Wang, Yu Lin Landau damping of electrostatic lower hybrid waves (LHWs) is investigated using the gyrokinetic electron and fullykinetic ion (GeFi) particle simulation code [Lin et al., 2005], in which electrons and ions are treated as gyrokinetic and fullykinetic particles, respectively. It is found that both the linear electrostatic dispersion relation and the linear electron Landau damping rate of LHWs agree very well with the theoretical predications. Similar to the Langmuir waves, a transition from strong decay at small amplitudes to weak decay at large amplitudes is observed due to the nonlinear Landau damping effects. Unlike the Langmuir waves, however, the LHWs interact directly with both the magnetized electrons and unmagnetized ions through the Landau damping. The decay rate is calculated as a function of the wave amplitude for various electrontoion temperature ratio T$_{e}$/T$_{i}$ and the parallel wave number k$_{\vert \vert }$. In the longtime evolution, the lower hybrid waves are found to evolve to a steady BGK mode with a steady finite amplitude. In addition, the current drive through the LHW electron Landau damping is also investigated. The generated currents are calculated as a function of the wave amplitude. [Lin et al., 2005] Y. Lin, X. Wang, Z. Lin, and L. Chen, Plasmas Phys. Controlled Fusion 47, 657, (2005). [Preview Abstract] 

BP8.00061: ABSTRACT WITHDRAWN 

BP8.00062: Energetic Electron Pitch Angle Scattering Experiments at the NRL SPSC Christopher Cothran, Erik Tejero, William Amatucci Cyclotron resonance of whistler waves with electrons, leading to pitch angle diffusion into the loss cone, is thought to be an important mechanism for depleting energetic electron populations in the radiation belts. Laboratory experiments in progress in the Space Physics Simulation Chamber (SPSC) at the U.S. Naval Research Laboratory (NRL) are attempting to observe and characterize this process. A pulsed RF plasma source developed specifically for these experiments produces high ionization fraction plasmas at densities near $10^{10}$/cm$^3$ in half mirror, full mirror, and uniform magnetic field geometries. Whistlers are driven by a helicon antenna, separate from that used for the plasma source, and interact in a 3m uniform field region with an energetic electron beam. The beam can be steered magnetically to adjust the pitch angle, and can be operated in CW or pulsed mode at up to 5keV and 80mA. Results of gridded energy analyzer measurements of the energetic electron populations will be reported. [Preview Abstract] 

BP8.00063: Calculations and measurements of argon emission in a magnetized linear plasma column Ivan Arnold, Connor Ballance, Stuart Loch, Edward Thomas Performing spectroscopic measurements of emission lines in relatively cold laboratory plasmas is challenging because the plasma is often neutraldominated and is not in thermal equilibrium. However, these types of plasma do offer a unique opportunity for benchmarking the finer details of atomic physics codes. We report on new levelresolved calculations for the dielectronic recombination of low charge states of argon. The results are compared with existing configurationaverage distortedwave results and semiempirical calculations. The recombination rates are processed into metastableresolved recombination rate coefficients and used in nonequilibrium ionization balance modeling of an argon plasma experiment on the Auburn ALEXIS facility. [Preview Abstract] 

BP8.00064: Electronion hybrid instability study in a linear magnetized plasma column Ami DuBois, Ivan Arnold, Edward Thomas A new, dual plasma experiment has been designed for the Auburn Linear Experiment for Instability Studies (ALEXIS). Using the 170 cm long and 10 cm diameter magnetized plasma column, a new investigation has been performed of a regime of instabilities that occur when a highly localized, radial electric field with a scale length that is much less than the ion gyroradius but greater than the electron gyroradius is generated in the plasma. Under these conditions, this localized electric field is expected to have little effect on the ions, but the electron trajectories will be modified. This can give rise to an electronion hybrid (EIH) instability, which produces a broadband wave spectrum in the lower hybrid frequency range. This work is focused on the conversion of electrostatic to electromagnetic wave modes generated by sheared electron flows. Measurements of high frequency electrostatic fluctuations in the lower hybrid frequency range will be discussed and compared with theoretical dispersion relation calculations. [Preview Abstract] 

BP8.00065: STELLERATOR, GENERAL TOKAMAK TRANSPORT AND TURBULENCE THEORY 

BP8.00066: Compact Toroidal Hybrid Research Program: Recent Progress and Future Plans D.A. Maurer, M. Cianciosa, J.D. Hanson, G.J. Hartwell, J.D. Hebert, J.L. Herfindal, S.F. Knowlton, M.C. ArchMiller, P. Traverso, M. Pandya, X. Ma Understanding the control and avoidance of major disruptions in current carrying toroidal plasmas is important in mitigating the effects of rapid loss of confinement in future devices. The Compact Toroidal Hybrid (CTH) experiment is investigating the passive avoidance of disruptions with the addition of a small amount of vacuum transform provided by external coils. In ohmicallydriven stellarator plasmas no disruptions of any kind are observed if the vacuum transform exceeds $\sim $ 0.11. Recent progress on the suppression of low$q_{a}$ (high \textit{$\iota $}$_{a})$, density limit, and vertically unstable plasma disruptions is overviewed. Interpretation of these results makes use of 3D equilibrium reconstructions using the V3FIT code [1]. Several new diagnostic tools have recently been developed and implemented on CTH. These new research tools include multichord interferometry, bolometry, H$\alpha $ emission detection, a twocolor soft xray camera, and upgraded magnetic sensor arrays. In addition to these diagnostic improvements, a new 200 kW gyrotron system will provide additional heating power for stellarator target plasmas. Future research directions and plans will also be discussed. \\[4pt] [1] J. D. Hanson, S. P. Hirshman, S. F. Knowlton, L. L. Lao, E. A. Lazarus, J. M. Shields, Nucl. Fusion, \textbf{49} (2009) 075031 [Preview Abstract] 

BP8.00067: Suppression of density limit disruptions using vacuum rotational transform on the CTH experiment S.F. Knowlton, J.D. Hanson, G.J. Hartwell, J.L. Herfindal, X. Ma, D.A. Maurer, M.C. ArchMiller, M. Pandya Experiments on the Compact Toroidal Hybrid (CTH) demonstrate the suppression of disruptions in tokamak discharges in which a fraction of the net rotational transform is produced by torsatron coils. Torsatron plasmas with adjustable vacuum transform are generated in CTH by ECRH, followed by rampup of the plasma current and density. Neither density nor currentdriven disruptions are observed when the vacuum rotational transform is above a threshold value of \textit{$\iota $}$_{vac}(a) \sim $ 0.11. At lower vacuum transform levels, density limit disruptions can occur in CTH when gas puffing produces lineaveraged densities near the Greenwald limit. These density limit disruptions are preceded by growing $m$/$n$=2/1 MHD oscillations prior to the disruptiion, indicating internal tearing mode activity. Above the apparent threshold value of \textit{$\iota $}$_{vac}(a) \sim $ 0.11, the plasma current declines as the density is increased, indicating cooling of the plasma without an associated major disruption. Vertical displacement events are also reduced by the addition of vacuum transform. Disruptions in plasmas with varying levels of applied vacuum transform will be discussed in light of other diagnostic measurements and modeling. Supported by US. Department of Energy Grant No. DEFG0200ER54610 [Preview Abstract] 

BP8.00068: 3D Equilibrium Reconstruction with Improved Magnetic Diagnostics on the Compact Toroidal Hybrid X. Ma, J.D. Hanson, G.J. Hartwell, S.F. Knowlton, D.A. Maurer Threedimensional reconstruction of plasma equilibria is important for understanding the physics of both intrinsic 3D confinement in stellarators as well as axisymmetric plasmas in tokamaks. Equilibrium reconstructions using the V3FIT code [1] will be presented for current carrying plasma on the Compact Toroidal Hybrid (CTH) torsatron experiment. The CTH is a heliotrontype device, in which the magnetic configuration can be strongly modified by an ohmicallydriven plasma current. These reconstructions use sets of recently upgraded magnetic diagnostics (44 channels), including segment and full Rogowski coils and new saddle coils. Reconstruction results with these new diagnostics, especially the time evolution of the reconstructed current density profile for a series of plasma conditions, will be presented and compared to previous ones using a smaller set of input magnetic signals. New modelling of the effects of eddy currents in the helical coil frame and vacuum vessel will also be discussed.\\[4pt] [1] J. D. Hanson, S. P. Hirshman, S. F. Knowlton, L. L. Lao, E. A. Lazarus, J. M. Shields, Nucl, Fusion49, 075031 (2009) [Preview Abstract] 

BP8.00069: NIMROD Modeling of the Compact Toroidal Hybrid (CTH) J.D. Hebert, J.D. Hanson, S.F. Knowlton, D.A. Maurer, M.G. Schlutt, C.C. Hegna, S.E. Kruger The 3D extended MHD code NIMROD [1] has been modified to model the nonaxisymmetric vacuum fields of the Compact Toroidal Hybrid (CTH) torsatron. Previous results [2] have shown good agreement between modeled and experimental vacuum fields as well as the formation and growth of island structures in discharges with driven current at zero $\beta$ and constant conductivity. Modeling of currentdriven discharges with self consistent Ohmic heating and finite $\beta$ will be presented. A new postprocessor to calculate the expected signals from experimental diagnostics using NIMROD simulation data is under development. Preliminary comparisons using magnetic diagnostic data from CTH will be shown. \\[4pt] [1] C.R. Sovinec, A.H. Glasser, D.C. Barnes, T.A. Gianakon, R.A. Nebel, S.E. Kruger, D.D. Schnack, S.J. Plimpton, A. Tarditi, M.S. Chu and the NIMROD Team, ``Nonlinear Magnetohydrodynamics with Highorder Finite Elements,'' Journal of Computational Physics, 195, 355 (2004).\\[0pt] [2] M. G. Schlutt et al, submitted to Nucl. Fusion (2012) [Preview Abstract] 

BP8.00070: Whole Shot 3D MHD Equilibrium Reconstruction using V3FIT M.C. Cianciosa, J.D. Hanson, D.A. Maurer, S.F. Knowlton, G.J. Hartwell, M.C. ArchMiller, X. Ma Equilibrium reconstruction is the process by which diagnostic signals are used to determine parameters of a MHD model. As modern stellarators are designed to achieve larger values of $\beta$ with higher bootstrap currents, the deviation between vacuum magnetic fields and plasma magnetic fields becomes significant. Coupled with the intricately shaped magnetic field structures, a fully three dimensional equilibrium reconstruction becomes an important tool for understanding plasma response. On the Compact Toroidal Hybrid (CTH) device, the V3FIT code plays an important role in the operations and interpretation of experiments. To facilitate this, a clientserver system has been developed to allow remote, parallel execution of the V3FIT [1] code. This, coupled with client software, allows integration of V3FIT with diagnostic systems for automated (shot to shot) and whole shot reconstructions. This presentation will discuss the structure and development of this system. An example of whole shot reconstructions from CTH diagnostics using this system will be presented. The future direction of this system and the V3FIT code will also be discussed.\\[4pt] [1] J. D. Hanson, S. P. Hirshman, S. F. Knowlton, L. L. Lao, E. A. Lazarus, J. M. Shields, Nucl. Fusion, \textbf{49} (2009) 075031 [Preview Abstract] 

BP8.00071: Combining Soft XRay, Magnetic, and Interferometric Diagnostics for Equilibrium Reconstruction on the Compact Toroidal Hybrid Experiment G.J. Hartwell, J.D. Hanson, M. Cianciosa, J.L. Herfindal, S.F. Knowlton, M.C. Miller, D.A. Maurer, P. Traverso, M. Pandya, X. Ma Reconstruction of the 3dimensional equilibrium is important for both improving the operation and understanding the physics of nonaxisymmetric stellarator type devices. Equilibrium reconstructions using the V3FIT[1] code will be presented for current carrying plasmas on the Compact Toroidal Hybrid (CTH) torsatron experiment (R$_{o}$ = 0.75 m, a$_{p} \sim $ 0.2 m, B $\le $ 0.7T, n$_{e} \le $5 x 10$^{19}$ m$^{3}$, T$_{e} \le $ 300 eV, I$_{p}<$=75kA). The reconstruction input data set includes Soft XRay (SXR) chord signals, magnetic diagnostics, data from a 1mm microwave interferometer, and shunt signals. The SXR data set includes signals from four cameras, each consisting of a 20channel AXUV20EL photodiode array viewing the CTH plasma through 2$\mu $m Be foil. Two full rogowski coils measure the plasma and vacuum vessel current, while additional eightsegment rogowski coils measure moments of the plasma position. Interferometer measurements along three chords help to constrain the density profile, while the shunt signals provide external coil current inputs. Reconstructions are explored using different SXR emissivity, density and current profile models, with different combinations of input data. \\[4pt] [1] J.D. Hanson, S.P. Hirshman, S.F. Knowlton, L.L. Lao, E.A. Lazarus, J.M. Shields, Nucl. Fusion, \textbf{49} (2009) 075031 [Preview Abstract] 

BP8.00072: Electron Temperature Measurements Using Soft XRay Emission on the Compact Toroidal Hybrid J.L. Herfindal, G.J. Hartwell, S.F. Knowlton, D.A. Maurer Electron temperature measurements are important in characterizing the equilibrium of fusion plasmas as well as an aid in the understanding of MHD stability. Soft Xray (SXR) diagnostics used to measure the electron temperature have been installed on the Compact Toroidal Hybrid (CTH) torsatron ($R_0 = 0.75~m$, $a_p \sim 0.2~m$, $B \leq 0.7~T$, $n_e \leq 5~$x$~10^{19}~m^{3}$, $I_p \leq 75~kA$, $T_e \leq 300~eV$). Two Amptek SXR spectrometers independently determine the electron temperature by measurement of a ratio of counts in specific energy channels and from fitting the spectral intensity. A new two color SXR camera has been designed, built, and installed on CTH. This camera consists of two AXUV20ELG diode arrays viewing the same polodial crosssection of the plasma through Be filters of different thicknesses and different cutoff energies. Electron temperatures are calculated by taking the ratio of the SXR intensities measured by the two detectors. An overview of the design and preliminary data will be presented. [Preview Abstract] 

BP8.00073: MHD Mode Analysis of Magnetic and H$_{\alpha}$ Fluctuations on the Compact Toroidal Hybrid M.D. Pandya, G.J. Hartwell, S.F. Knowlton, X. Ma, D.A. Maurer Strong MHD activity is typically observed in Compact Toroidal Hybrid (CTH) when the edge transform, $\iota_{a}$, is near rational values. CTH is equipped with poloidal and toroidal pickup coil arrays that measure the poloidal magnetic field. Two poloidal arrays separated toroidally by $180^{\circ}$ have 16 coils each and two toroidal arrays located at poloidal angles of $\theta= \pm 90^{\circ}$ have 10 coils each. A seven channel array of $H_{\alpha}$ ($\lambda=656nm$) detectors has been recently installed and is operational. The plasma is viewed by these detectors on horizontal chords above and below the midplane. During the current rise when $\iota_{a} \sim 1/2$ or $1/3$ , rotating $m/n=2/1$ or $3/1$ modes respectively, are typically present. Fluctuation analysis using Singular Value Decomposition (SVD) leads to identification of the dominant spatial and temporal modes present in the plasma. Comparison of observed MHD activity during the initial current rise for low edge transform $(\iota_{vacuum} \sim 0.04)$ and high edge transform $(\iota_{vacuum} \ge 0.1)$ cases will be presented. Also, the structure of magnetic and $H_{\alpha}$ fluctuations before density limit and low$q$ disruptions will be discussed. [Preview Abstract] 

BP8.00074: Design and implementation of a Thomson scattering diagnostic for the Compact Toroidal Hybrid Peter Traverso, David Maurer, Gregory Hartwell, Stephen Knowlton, Matthew Miller The Compact Toroidal Hybrid (CTH) experiment is investigating the avoidance of disruptions in ohmically driven torsaton plasmas in which the ratio of vacuum or external coil transform to the total transform generated by the plasma current and external coils can be lower than 10{\%}. To aid in the characterization and equilibrium reconstruction of these currentcarrying CTH plasmas a new Thomson scattering system is under development. Details of the Thomson scattering system design and implementation will be discussed including choice of laser scattering geometry, laser wavelength, stray laser light rejection strategy, collections optics, and spectrometer design. [Preview Abstract] 

BP8.00075: Multichannel Density Measurements with a Millimeter Wave Interferometer on CTH M.C. ArchMiller, G.J. Hartwell, S.F. Knowlton, D.A. Maurer A threechannel 1\,mm wave interferometer has been installed on the Compact Toroidal Hybrid torsatron (CTH). The interferometer design makes novel use of a subharmonic mixer for detection, which simplifies alignment. It employs a single electronically tunable source that is repetitively chirped using a sawtooth waveform of frequency up to 1\,MHz. The 15.25\,GHz drive oscillator is multiplied in two stages to 122\,GHz before a final doubler stage brings it to 244\,GHz. Local oscillator (LO) power at 122\,GHz is directed through waveguide to the LO input of the subharmonic mixer of each viewing chord, simplifying alignment. Phase detection is performed by directly digitizing the amplified mixer outputs at 50\,MHz and processing them with a software algorithm. Measurements made with the central chord of the new interferometer agree with those from the existing 4\,mm system at low densities. The 1\,mm system performs well in currentdriven discharges reaching densities over $10^{19}$ m$^{3}$, whereas the lower frequency interferometer is found to be less reliable due to loss of fringes. This is a critical improvement for experiments studying disruptions in the CTH device. Results from the fully implemented threechannel interferometer will be presented and discussed. [Preview Abstract] 

BP8.00076: Overview and New Directions in the HSX Program F.S.B. Anderson Large intrinsic flows have been measured by CHERS in the direction of quasisymmetry. Impurity transport experiments have begun using laser blowoff. Edge probe measurements show the Reynolds stress may play an important role in the edge poloidal momentum balance. Improved Halpha diagnostics and fueling systems are being installed to better understand neutral transport. This is carried out with comparisons between DEGAS and EMC3EIRENE. These codes are being applied to guide new experimental studies of the divertor structure in HSX. Efforts are underway to determine and possibly test elements in the magnetic structure critical for energetic particle confinement. Previous equilibrium reconstruction and fluctuation studies are being extended through optimized diagnostics. A second ECRH system with beam steering and modulation is now operational and being used for heat pulse propagation studies. The GNET 5D FokkerPlanck code is being used to study both confinement of energetic ions produced by ICRH heating, and nonMaxwellian distribution function effects on SX and ECE measurements with high power density ECRH. [Preview Abstract] 

BP8.00077: Impurity Transport Research at the HSX Stellarator C. Clark, D.T. Anderson, F.S.B. Anderson, K.M. Likin, J.N. Talmadge, K. Zhai Predictive models of impurity transport are required to ensure the successful operation of future magnetic confinement fusion devices. As a step towards the creation and validation of such models for stellarator devices, experiments are under way to measure the impurity transport properties of HSX, the first quasisymmetric stellarator. A laser blowoff impurity injection system is used to rapidly deposit a small, controlled, quantity of aluminum into the confinement volume. AXUV photodiode arrays, some of which are equipped with filters that block visible light, but transmit ultraviolet and soft xray light, are used to take timeresolved measurements of the impurity radiation. Onedimensional emissivity profiles are recovered from the measurement using an inversion process that accounts for the fully threedimensional detector views. Impurity confinement times measured during an HSX density scan will be presented, along with data that demonstrates the improvement in impurity injection that occurs when a 10nm layer of chromium is present between the glass and the aluminum. [Preview Abstract] 

BP8.00078: Measurements of Reynolds stress flow drive in the HSX stellarator R.S. Wilcox, D.T. Anderson, J.N. Talmadge, F.S.B. Anderson The radial electric field has been measured using Langmuir probes and is found to deviate from its neoclassically predicted value in the HSX stellarator. HSX has been optimized for quasihelical symmetry, which has the effect of reducing the neoclassical nonambipolar particle losses which dominate the determination of the radial electric field in unoptimized stellarators. When the neoclassical transport is sufficiently reduced, other processes, such as the Reynolds stress, may also be important in determining the rotation. The Reynolds stress has been measured using floating potential signals to estimate the poloidal and radial velocity fluctuations. Based on these measurements and some estimate of the viscosity, the resultant flow drive from the measured Reynolds stress is shown to correspond qualitatively to the deviation in the measured radial electric field value from the neoclassical calculation. [Preview Abstract] 

BP8.00079: Modeling Neutral Hydrogen in the HSX Stellarator L. Stephey, A. Bader, D.T. Anderson, J.N. Talmadge, C. Hegna, F.S.B. Anderson Efforts to improve the understanding of neutral hydrogen in the HSX stellarator are ongoing. The DEGAS code [1], a fully 3D MonteCarlo neutral particle code, is used to simulate neutral particle density and synthetic Halpha emission in HSX. DEGAS simulations are compared to EMC3EIRENE [2] simulations in an effort to understand the similarities and differences in how each code predicts neutral physics in the unique HSX geometry and relatively low operating density. Additionally, experimentally motivated DEGAS simulations are presented of a supersonic gas injection system that will be installed on HSX. Finally, simulations of many different wall recycling scenarios are presented in an effort to develop a plasma wall interaction model that more closely matches experimental Halpha measurements.\\[4pt] [1] D. B. Heifetz et al, J. Comp. Phys. Vol. 46 (1982) p. 309.\\[0pt] [2] Y. Feng et al, Contribution Plasma Physics, 44 13 (2004) p. 5769. [Preview Abstract] 

BP8.00080: Targeted Physics Optimization in the HSX Stellarator J.N. Talmadge, K.M. Likin, V.V. Nemov, Y. Turkin, W. Kernbichler The quasihelically symmetric (QHS) stellarator HSX has a set of auxiliary magnet coils that were used in previous experiments to show that particle and heat transport, as well as plasma flow damping, is smaller in the QHS configuration compared to results obtained when the symmetry is degraded. To plan out future experiments, we have developed an optimization code to vary the currents in the auxiliary coils and to minimize or maximize several target physics functions. There are 48 such auxiliary coils in HSX, 12 per field period, but we vary only the currents in 6 of them and mirror those currents to maintain stellarator symmetry. We are particularly interested in minimizing and maximizing a parameter related to the bounceaveraged gradB drift velocity of trapped particles such as alpha particles in a fusion reactor [1]. The intent is to investigate how the magnetic configuration affects energetic particle confinement in HSX when heated with ICRF. Other target parameters that are being explored are the effective ripple, the geometric bootstrap current coefficient and the damping rate of the plasma flow. \\[4pt] [1] V.V. Nemov et al., Physics of Plasmas 12, (2005) 112507. [Preview Abstract] 

BP8.00081: 3D Plasma Equilibrium Reconstruction at the HSX Stellarator  Current Status and Diagnostic Development E. Chlechowitz, D.T. Anderson, J.C. Schmitt The equilibrium magnetic field configuration of tokamaks and stellarators can be determined by measuring the plasma current and pressure profile. V3FIT, a three dimensional plasma equilibrium reconstruction code [1], and a set of magnetic pickup coils have been used to reconstruct HSX equilibria in the past. To discriminate between possible equilibrium solutions, the output from a 10 channel Thomson scattering system has been implemented in the reconstruction algorithm. Furthermore, an upgrade of 50 magnetic diagnostics is planned, measuring poloidal and radial magnetic field components. The positions of the diagnostics have been chosen because of their high signal effectiveness and/or a high ranking in a SVD analysis study [2]. The efficiency of both placement methods can be compared by using subsets of the coils. The number of possible solutions from reconstruction has been drastically reduced, depending on the allowed $\chi^2$ range [1], using the complete set of coils. \\[4pt] [1] J.D. Hanson et al, Nucl. Fusion 49 075031 (2009) \newline [2] N. Pomphrey et al, Phys. Plasmas 14, 056103 (2007) [Preview Abstract] 

BP8.00082: Core Density Fluctuation Measurements by Interferometry in the HSX Stellarator C. Deng, D.L. Brower, D.T. Anderson, F.S.B. Anderson, A. Briesemeister, K.M. Likin, J.N. Talmadge, R. Wilcox, K. Zhai The measurement of density fluctuations by the multichannel interferometer system on the HSX stellarator has shown a variety of density fluctuation characteristics. Both coherent and broad band density fluctuation modes are observed in the plasma core. For quasihelically symmetric plasmas with B$_{T}$=1.0 T, significant increases (both amplitude and frequency) in the turbulent density fluctuation spectrum are observed when heating location changes from onaxis to high field side. The CHERS measurements show that the plasma flow velocities decrease significantly for offaxis heating and core fluctuations increase. In addition, a coherent mode with f$\sim $15kHz is observed with small displacement of the heating location inward. When HSX is operated without quasihelical symmetry, the sensitivity of broadband density fluctuations to changes of heating location and ECRH power were not observed. At B$_{T}$=1T and n$_{e} \sim $ 4x10$^{12}$ cm$^{3}$, a coherent electrostatic mode at $\sim $28 kHz is observed for the Mirror configuration. An attempt to identify the fluctuations modes will be made by exploring the relations between density fluctuations and different plasma parameters, heating locations, and configurations. [Preview Abstract] 

BP8.00083: Modulated Heating Experiments on the HSX Stellarator G.M. Weir, K.M. Likin, F.S.B. Anderson, J.N. Talmadge, D.T. Anderson Modulated heating experiments with a new ECRH system on the HSX stellarator are used to determine the electron thermal diffusivity from the dynamic response of the electron temperature using the Electron Cyclotron Emission (ECE) diagnostic. The new ECRH system has a poloidally steerable mirror that is capable of depositing energy across the minor radius and refraction of the heating beam leads to differences in the width of the absorbed power profile compared to the primary ECRH system. The ECE requires modeling to determine the electron temperature due to finite reflectivity and optical depth and analysis of the optically gray emission will be presented along with hardware upgrades and the absolute calibration of the 16channel heterodyne radiometer. Initial measurements yield an incremental thermal diffusivity consistent with the powerbalance value in the core of HSX and analysis of these heat pulse propagation results will be presented. [Preview Abstract] 

BP8.00084: Study of ICRH and ion confinement in the HSX stellarator Konstantin Likin, Sadayoshi Murakami, Joseph Talmadge In HSX the power at the electron cyclotron resonance harmonics is used to produce and heat the plasmas. The ion temperature in such plasmas remains low ($<$ 100 eV) as compared to the electron temperature ($\sim$ 2 keV). If the ions can be heated up to a few hundred eV then the ion low collisionality regime becomes accessible and the difference between plasma confinement in quasisymmetric and conventional stellarator configurations may be more pronounced. Also with RF heating directly to the ions the radial electric field can be varied that will help to study its effect on plasma confinement. The code GNET solves the linearized drift kinetic equation in 5D space using the full 3D equilibrium provided by VMEC. With GNET we would like to predict (1) efficiency of ion cyclotron resonance heating (ICRH); (2) fast ion confinement; (3) chargeexchange losses in various regimes; (4) ion confinement in different magnetic configurations. The code has been adapted to the HSX geometry and a new parallel version has been installed on the NERSC Cray computer. Results from GNET on modeling of ICRH and ion confinement in HSX will be presented. [Preview Abstract] 

BP8.00085: Modeling of HighPower Fundamental Omode ECRH Plasmas in the HSX Stellarator J.W. Radder, K.M. Likin, J.N. Talmadge, D.T. Anderson, G. Weir, S. Murakami Hard xray and ECE measurements provide evidence of suprathermal electron populations in the HSX stellarator for low density, 100 kW fundamental Omode ECRH. A fivedimensional FokkerPlanck code, GNET, is used to calculate the deviation from a Maxwellian background distribution via a Monte Carlo technique. Calculated electron distribution functions are presented for low line average density, hightemperature plasmas ($n_e \approx 2\times 10^{18}$~m$^{3}$, $T_e \approx 1.5$ keV) with low collision frequencies in the heating region. Calculated Xray bremsstrahlung emission spectra and electron cyclotron emission spectra will be presented for nonMaxwellian electron distribution functions obtained with GNET and compared to measured spectra. [Preview Abstract] 

BP8.00086: Investigation of HighRecycling Regime in QuasiHelically Symmetric Geometries A. Bader, D.T. Anderson, C.C. Hegna, J.N. Talmadge, Y. Feng, J.D. Lore We simulate the edge region of quasihelically symmetric (QHS) geometries based on the HSX stellarator in an attempt to understand the accessibility of a highrecycling (HR) regime in islanddivertor (ID) geometries. Stellarators with island divertors have typically had difficulty achieving HR, partially due to friction from counterstreaming flows along field lines with long connection lengths.\footnote{Y. Feng Nuc. Fus. 49 095002 (2009)} We use the EMC3EIRENE code to analyze the edge region of stellarators in both QHS geometry and in alternate configurations which employ auxiliary coils to modify the edge island structure. We show that HSXsized QHS geometries transition to HR at separatrix densities ($n_{\mathrm{sep}}$) between 1.0 $\times$ 10$^{13}$ and 1.0 $\times$ 10$^{14}$ cm$^{3}$, with $n_{\mathrm{target}}$ $> n_{\mathrm{sep}}$ at $\approx$ 1 $\times$ 10$^{14}$ cm$^{3}$. Furthermore, we show that using auxiliary coils to reduce both the size of the edge islands and the magnitude of the counterstreaming flows can improve divertor performance. In this poster, we explore the role of island size, separatrix temperature and separatrix density on the density and temperature at the targets. [Preview Abstract] 

BP8.00087: The path to exploring physics in advanced devices with a heavy ion beam probe D.R. Demers, P.J. Fimognari The scientific progression of alternative or advanced devices must be met with comparable diagnostic technologies. Heavy ion beam probe innovations from ongoing diagnostic development are meeting this challenge. The diagnostic is uniquely capable of measuring the radial electric field, critically important in stellarators, simultaneously with fluctuations of electron density and electric potential. HIBP measurements can also improve the understanding of edge physics in tokamaks and spherical tori. It can target issues associated with the pedestal region, including the mechanisms underlying the LH transition, the onset and evolution of ELMs, and the evolution of the electron current density. Beam attenuation (and resulting low signal to noise levels), a challenge to operation on devices with large plasma crosssections and high n$_{e}$ and T$_{e}$, can be mitigated with greater beam energies and currents. Other application challenges, such as measurements of plasma fluctuations and profile variations with elevated temporal and spatial resolutions, can be achieved with innovative detectors. The scientific studies motivating the implementation of an HIBP on HSX, ASDEXU, and W7X will be presented along with preliminary scoping studies. [Preview Abstract] 

BP8.00088: Development of Diagnostics and Plasma Facing Components for QuasiSteadyState Operation of the Wendelstein 7X Stellarator Thomas Sunn Pedersen We will report on the present status of the design and manufacturing of the plasma facing components and diagnostics that are being developed for Wendelstein 7X (W7X). W7X is scheduled to start its first physics operation phase (OP1) in 2015, with an uncooled graphite divertor, limiting discharges to 10 seconds at full power. The second operation phase (OP2), scheduled to begin in 2019, will have components actively cooled with water, including a divertor capable of withstanding 10 MW/m$^{2}$ in steady state, the socalled High Heat Flux (HHF) divertor. The elements for the HHF divertor are in series production, after a successful R{\&}D program which included rigorous testing at and above the heat flux levels expected in W7X. Highlights from this R{\&}D program will be presented. Many diagnostics being prepared for OP1 are being designed to withstand the up to 30minute pulses foreseen for OP2. These diagnostics must therefore already now be designed to be able to withstand the steady state heat loads both due to ECRH stray radiation and due to plasma radiation. Examples of the development, design and testing of optical and magnetic diagnostics for steady state operation will be given. [Preview Abstract] 

BP8.00089: Design of a new high heat flux divertor component for the W7X stellarator J.D. Lore, T. Andreeva, J. Boscary, J. Geiger, J.H. Harris, A. Lumsdaine, D. McGinnis, A. Peacock, J. Tipton A new divertor component, known as the ``scraper element,'' is being designed for the high heat flux operational phase of W7X. The scraper element (SE) protects regions of the main divertor from unacceptable heat loads that occur during the bootstrap current evolution in certain configurations. The excessive loads occur at intermediate values of the bootstrap current, as the configuration transitions from a limited divertor to an island divertor over $\sim $40s. The SE intercepts the field lines that would strike the overloaded components. Each row of the SE will be built using activelycooled carbon fiber composite monoblocks of a similar type as those qualified for ITER, with heat fluxes on the order of 1215MW/m$^{2}$ in steady state. The heat flux magnitudes and the strike point patterns are calculated from following field lines in a 3D magnetic field that includes contributions from the vacuum equilibrium and the plasma currents. The latest SE design and supporting modeling will be presented. Work supported by D.O.E. contract DEAC0500OR22725. [Preview Abstract] 

BP8.00090: Impact of selfconsistent bootstrap current on the magnetic structure of W7X P.S. Burns, A.S. Ware The impact of selfconsistent bootstrap current on the magnetic structure of equilibria in computational studies of the W7X stellarator is examined. While one of the criteria in designing W7X was the minimization of the bootstrap current, at finite$\beta$ there will likely still be some residual bootstrap current. Even a small bootstrap current can change the rotational transform profile and thus, change the magnetic configuration, especially in the edge region. In this work, freeboundary equilibria for the W7X coil configuration have been obtained at a range of $\beta$ values and the bootstrap current has been calculated for each. An optimization is underway to obtain equilibria with selfconsistent bootstrap current (i.e., where the plasma current is solely from the bootstrap current). The impact of both finite$\beta$ and bootstrap currents on the magnetic structure in the edge will then be examined using the SIESTA code [Hirshman, {\it et al.}, Phys. Plasmas {\bf 18}, 062504 (2011)]. [Preview Abstract] 

BP8.00091: Progress in the design of a driftoptimized torsatron device F. Bunt, A.S. Ware Progress on the design of a driftoptimized torsatron configuration is presented. Previous work developed two (unoptimized) coil torsatron coil sets  including vertical and solenoidal field coils for flexibility. Here, we present the results of optimizing these configurations for improved neoclassical confinement. The goal of this project is to design a driftoptimized torsatron device in order to blend the benefits of a natural divertor region provide by the torsatron coils with improved neoclassical confinement from driftoptimization. Equilibrium, transport and stability characteristics will be compared across the optimized configurations. [Preview Abstract] 

BP8.00092: Coil optimization for a high$\beta$ stellaratortokamak hybrid B. Schlomann, A.S. Ware, D.A. Spong Magnetic coil configurations are developed for a driftoptimized, tokamakstellarator hybrid that is stable to both pressure and currentdriven modes for high values of $\beta$. Previous work on this configuration [A. S. Ware, {\it et al.}, Phys. Rev. Lett, 89, 125003 (2002)] was carried out using a fixedboundary equilibrium (i.e., with no set of external coils). Here, we present initial work to produce a realizable coil set for such a configuration. This work is done using the COILOPT code to develop an initial coil set and the STELLOPT code to enhance the quality of the resulting freeboundary equilibria. Since this is a hybrid device, the initial modular coil sets have the advantage of being simpler than modular coils from recent stellarator design efforts (such as QPS and NCSX). The stability and confinement properties of the resultant optimized freeboundary configuration will be tested. [Preview Abstract] 

BP8.00093: Stellarator Pilot Plants with Simplified Coils M.C. Zarnstorff, G.H. Neilson, T. Brown, D. Gates Stellarators have a significant advantage as a pilot plant since they do not need current drive, reducing recirculating power, reducing required technology development, and easing tritium breeding. In addition, stellarators have soft performance limits without disruptions, and thus do not require nearby conducting walls, thick plasmafacing armor, active plasma stability control, or current profile control. A stellarator pilot plant design based on a quasiaxisymmetric (QA) configuration with aspect ratio 4.5, major radius 4.75 m, and magnetic field on axis of 5.6 T is projected to have a Qeng greater than 2.7 and a peak neutron wall load higher than $2 MW / m^2$. The pilot plant projects to net electricity production with 100200 MW of fusion power produced. The QA design can build on the tokamak understanding and data base, since it is predicted to share many confinement and stability characteristics with tokamaks. Strategies for simplified coils and sectorbased maintenance using magnetic materials for field shaping will be discussed. [Preview Abstract] 

BP8.00094: Simulating the Effects of Stellarator Geometry on Gyrokinetic Instabilities with the GS2 Code J.A. Baumgaertel, W. Guttenfelder, G.W. Hammett, D.R. Mikkelsen, P. Xanthopoulos, J. Geiger, M. Nunami, W. Dorland, E. Belli The gyrokinetic turbulence code, GS2, has been adapted to handle stellarator geometry. Herein a new computational grid generator and upgrades to GS2 itself are described and benchmarked with GENE and GKVX. Additionally, detailed linear studies using the National Compact Stellarator Experiment (NCSX) geometry are discussed, in particular those comparing stability in two equilibria with different $\beta$ and those comparing NCSX linear stability to a tokamak case. Finally, a comparison of linear stability of two locations in a Wendelstein 7AS (W7AS) plasma is presented. The experimentallymeasured parameters used were from a W7AS shot in which measured heat fluxes were too large for neoclassical predictions at both radii. Results from GS2 linear simulations show that the outer location has higher gyrokinetic instability growth rates than the inner one. Mixinglength estimates of the heat flux are within a factor of 3 of the experimental measurements, indicating that gyrokinetic turbulence may be responsible for the higher transport measured by the experiment in the outer regions. This work was supported by the SciDAC Center for the Study of Plasma Microturbulence and Department of Energy Contract DEAC0209CH11466. [Preview Abstract] 

BP8.00095: Gyrokinetic Transport Stiffness Calculations on Stellarator Geometries B.J. Faber, H. Mynick, G.M. Weir, K.M. Likin, J.N. Talmadge A significant, unanswered question in plasma physics is the difference in transport ``stiffness'' between tokamaks and stellarators. In an effort to shed light on this issue, presented are nonlinear gyrokinetic calculations on various machine geometries: the Helically Symmetric Experiment, the National Compact Stellarator Experiment and an equivalent tokamak configuration. Nonlinear gyrokinetic fluxes have been compared directly to experimental fluxes observed in HSX power modulation experiments. Linear calculations on HSX reveal large growth rates due to both ion temperature gradient and trapped electron turbulence, necessitating a kinetic treatment of electrons; one of the first calculations of its kind for stellarators. A comparison of transport stiffness profiles computed through nonlinear gyrokinetic calculations of ion temperature gradient turbulence for the different machine configurations will be presented. [Preview Abstract] 

BP8.00096: Theoretical investigation of GAMs in stellarators W. Sengupta, A.B. Hassam The possibility of observing GAMs in quasisymmetric (QS) stellarators such as HSX is investigated. GAMs in axisymmetric tokamaks can be excited because, theoretically, the parameter $\vec{B}\cdot\nabla \vec{B} /  \vec{B}\times \nabla B$, which is a measure of the bounce frequency compared to the GAM frequency $(\omega_{bounce} \approx c_s/qR << \omega_{GAM} \approx c_s/R)$, is small. In QS stellarators, however, this ratio may not be small enough, leading to Landau damping. We study a QS system, using a model which spans a broad range in this parameter, and apply the results to HSX in the QS mode. HSX can also operate in a Mirror Mode. Due to the intrinsic nonambipolarity of the Mirror mode, a zonal flow oscillation with frequency lower than that of the standard GAM may be excited, as shown by Helander et al.[1] Trapped particles contribute significantly to this oscillation. We study this case and assess whether GAMs could be observed on HSX in the mirror mode.\\[4pt] [1] Helander P et al. 2011 Plasma Physics and Controlled Fusion \textbf{53} 054006 [Preview Abstract] 

BP8.00097: Proxy functions for turbulent transport optimization of stellarators Mordechai Rorvig, Chris Hegna, Harry Mynick, Pavlos Xanthopoulos The design freedom of toroidal confinement shaping suggests the possibility of optimizing the magnetic geometry for turbulent transport, particularly in stellarators. The framework for implementing such an optimization was recently established [1] using a proxy function as a measure of the ITG induced turbulent transport associated with a given geometry. Working in the framework of local 3D equilibrium [2], we investigate the theory and implications of such proxy functions by analyzing the linear instability dependence on curvature and local shear, and the associated quasilinear transport estimates. Simple analytic models suggest the beneficial effect of local shear enters through polarization effects, which can be controlled by field torsion in small net current regimes. We test the proxy functions with local, electrostatic gyrokinetics calculations [3] of ITG modes for experimentally motivated local 3D equilibria.\\[4pt] [1] H. E. Mynick, N. Pomphrey, and P. Xanthopoulos, Phys. Rev. Lett. 105, 095004 (2010).\\[0pt] [2] C. C. Hegna, Physics of Plasmas 7, 3921 (2000).\\[0pt] [3] F. Jenko, W. Dorland, M. Kotschenreuther, and B. N. Rogers, Physical Review Letters 7, 1904 (2000). [Preview Abstract] 

BP8.00098: Asymptotic expansion for stellarator equilibria with a nonplanar magnetic axis: Numerical results Jeffrey Freidberg, Antoine Cerfon, Felix Parra We have recently presented a new asymptotic expansion for stellarator equilibria that generalizes the classic GreeneJohnson expansion [1] to allow for 3D equilibria with a nonplanar magnetic axis [2]. Our expansion achieves the two goals of reducing the complexity of the threedimensional MHD equilibrium equations and of describing equilibria in modern stellarator experiments. The end result of our analysis is a set of two coupled partial differential equations for the plasma pressure and the toroidal vector potential which fully determine the stellarator equilibrium. Both equations are advection equations in which the toroidal angle plays the role of time. We show that the method of characteristics, following magnetic field lines, is a convenient way of solving these equations, avoiding the difficulties associated with the periodicity of the solution in the toroidal angle. By combining the method of characteristics with Green's function integrals for the evaluation of the magnetic field due to the plasma current, we obtain an efficient numerical solver for our expansion. Numerical equilibria thus calculated will be given.\\[4pt] [1] J.M. Greene and J.L. Johnson, Phys. Fluids 4, 875 (1961)\\[0pt] [2] A.J. Cerfon, J.P. Freidberg, and F.I. Parra, Bull. Am. Phys. Soc. 56, 16 GP9.00081 (2011) [Preview Abstract] 

BP8.00099: Inclusion of pressure and flow in a new 3D MHD equilibrium code Daniel Raburn, Atsushi Fukuyama Flow and nonsymmetric effects can play a large role in plasma equilibria and energy confinement. A concept for such a 3D equilibrium code was developed and presented in 2011. The code is called the Kyoto ITerative Equilibrium Solver (KITES) [1], and the concept is based largely on the PIES code [2]. More recently, the workinprogress KITES code was used to calculate forcefree equilibria. Here, progress and results on the inclusion of pressure and flow in the code are presented. \\[4pt] [1] Daniel Raburn and Atsushi Fukuyama, Plasma and Fusion Research: Regular Articles, 7:240381 (2012).\\[0pt] [2] H. S. Greenside, A. H. Reiman, and A. Salas, J. Comput. Phys, 81(1):102136 (1989). [Preview Abstract] 

BP8.00100: Estimation of NBI Beam Pressure Including Orbit Effect Ryosuke Seki, Kiyomasa Watanabe, Yasuhiro Suzuki, Yoshimitsu Asahi, Yutaka Matsumoto, Kiyotaka Hamamatsu With a NBI heating, a volume averaged beta has been reached 5{\%} in the low field. In the high beta plasma of the LHD, it has been pointed out that the beam pressure and/or the pressure anisotropy significantly would affect the properties of MHD equilibrium and stability. Therefore, it is one of the important issues to identify the beampressure in the total plasma pressure. In this study, the beampressures due to the NBs are calculated by the Monte Carlo method, and the pressure anisotropy and the 3dimensional profile of the beam pressures are studied. In the LHD highbeta plasma, there is a lot of reentering fast ions which reenter in the region of the closed flux surfaces after they have once passed out of the Last Closed Flux Surface (LCFS). They are regarded as the lost particles in the conventional analyses using the magnetic coordinates. To include the reentering fast ions, the MonteCarlo code, MORH, on the basis of the orbit following in the real coordinates are used. [Preview Abstract] 

BP8.00101: Application/extension of the Landaufluid approach for energetic particle instabilities in stellarators and tokamaks Don Spong Reduced dimensionality Landaufluid models have been useful due to their computational efficiency and ease at evaluating the effects of different physics assumptions. Different challenges are present (global mode structure, finite orbit widths, nonMaxwellian distributions) in applying these methods to EPdriven instabilities than for applications to core microturbulence. The TAEFL model has demonstrated that Landau closure methods can be used to introduce the linear resonances that drive Alfv\`{e}n (AE) instabilities; this model has recently been extended to include coupling to acoustic waves, and higher order EP moments (providing the flexibility needed for analysis of nonMaxwellian distribution functions). Also, a secondorder nonlinear stepper has been implemented (allowing simulation of AE growth/decay cycles) and an eigenvalue solver version for 3D configurations is under development using parallel solvers. Recent applications have included RSAE to TAE frequency sweeps, JET antenna damping measurements, edge and core localized AE's, alphadriven instabilities in ITER, V\&V studies, and EP instabilities in stellarators (HAE, RSAE, TAE) and RFP's. These applications and the ongoing extensions to the model will be discussed. [Preview Abstract] 

BP8.00102: ABSTRACT WITHDRAWN 

BP8.00103: Neoclassical level poloidal rotation measurements based on the inboardoutboard asymmetry of toroidal rotation in the TCV tokamak Yann Camenen, Alessandro Bortolon, Alexander N. Karpushov, Yanis Andrebe, Basil Duval, Lucia Federspiel, Olivier Sauter Direct and indirect poloidal rotation measurements with improved accuracy were performed and compared in the TCV tokamak. The indirect measurement argues that, provided the plasma flow is divergence free on a flux surface, poloidal rotation can be inferred from the toroidal rotation at the high and low field sides of a flux surface. The key advantage of the method is an intrinsic amplification factor: instead of measuring poloidal rotation directly (typically ~few km/s i.e. of the order of the measurement accuracy), a difference in toroidal rotation is measured that is 4 to 10 times larger. Here, the main uncertainties arise from the flux surface mapping that are, however, largely compensated by this amplification factor. In TCV, the $C^{6+}$ toroidal rotation was measured across the whole plasma diameter by charge exchange (CX) spectroscopy for a series of low collisionality ($0.1<\nu^*<1.5$) OH and ECH Lmode plasmas, including positive and negative plasma current and toroidal magnetic field. Interestingly, the inferred poloidal rotation and the neoclassical theory predictions from the NEOART code, a variant of NCLASS, agree within $\pm 1$ km/s. In particular, a reversal of poloidal rotation is observed with the toroidal magnetic field direction, as predicted by theory. [Preview Abstract] 

BP8.00104: Utilization of 2D ECEI images for the study of the core instability structures under ECRH G.H. Choe, Y. Nam, G.S. Yun, J.E. Lee, M.J. Choi, H.K. Park, A. Bierwage, K.D. Lee A wide variety of sawtooth patterns have been observed in the core of plasmas assisted by electron cyclotron resonance heating (ECRH) in a large number of tokamaks. In the KSTAR tokamak, the sawtoothing core under ECRH has been visualized in 2D using an electron cyclotron emission imaging (ECEI) system. The 2D images revealed a variety of instability structures such as dual cores, triple cores, and crescent shaped structure, which are different from the internal kink mode of the normal sawteeth. For rapid identification of the core structure using 1D ECE signals, the characteristic patterns in the ECE time traces have been explained by the corresponding 2D ECEI images. The statistical analysis for more than 600 discharges using this identification method suggests that the current perturbation due to ECRH inside the q=1 surface may be responsible for the altered core instability structures. A simulation based on linearized twofield reduced MHD model is planned to study the role of localized current perturbations. [Preview Abstract] 

BP8.00105: Analysis of high resolution 2D images of the m/n=2/1 tearing mode in KSTAR RMP experiments Minjun Choi, G.S. Yun, W. Lee, H.K. Park, C.W. Domier, N.C. Luhmann, Jr., A.J.H. Donn\'e, S.G. Lee In the 2011 KSTAR campaign, the m/n=2/1 tearing mode has often been observed in plasmas with externally applied static n=1 Resonant Magnetic Perturbation (RMP) fields. It is generally believed that the RMP can induce tearing of flux surfaces via the socalled mode penetration mechanism [1]: (1) the RMP slows the plasma rotation down to the resonance condition, (2) the plasma shielding current is minimized, and (3) the RMP fields penetrate into the plasma, tearing the flux surfaces. This scenario of tearing mode generation induced by RMP is consistent with the observed changes of the toroidal velocity profile and the appearance of tearing mode structures as reconstructed from 2D electron cyclotron emission (ECE) images. In addition, the detailed 2D ECE images of the tearing mode enabled a straightforward estimation of the delta prime, which is a critical parameter for understanding the tearing physics.\\[4pt] [1] F.L. Waelbroeck, \textit{Nucl. Fusion} \textbf{49} (2009). [Preview Abstract] 

BP8.00106: Simulations of plasma shape and verticalinstability control in KSTAR L.L. LoDestro, R.H. Bulmer, W.H. Meyer, L.D. Pearlstein In recent years, prompted by applications to ITER, the Corsica code's capability for evolving freeboundary equilibria coupled to transport, in particular currentprofile transport, has been improved. All active and passive material conductors (coils, conducting plates, vessel walls) in these calculations are represented as axisymmetric wires, coupled to each other and the plasma with circuit equations; up/down asymmetric elongated plasmas require a feedback circuit to control the vertical instability. The improvements include: completion of the facility for running Corsica as the plasma model in Matlab/Simulink simulations of the circuits, benchmarked against standalone Corsica simulations; development of a general machinedescription database for importing or verifying a machine's conductor configurations; and modernization and generalization of the (scripted) algorithms that accomplish the couplings in Corsica, plus new features needed for ITER scenario development. The code has been used to assess the capability of ITER's invessel coils (VS3) and is presently being used for ITER control simulations. In this paper, we apply the code to KSTAR. We have updated the KSTAR machine description and will present simulations of plasmashape and verticalinstability control. [Preview Abstract] 

BP8.00107: Characterization of MHD instabilities, plasma rotation alteration, and RWM control analysis in the expanded Hmode operation of KSTAR Y.S. Park, S.A. Sabbagh, J.W. Berkery, J.M. Bialek, J.G. Bak, W.H. Ko, S.G. Lee, Y.M. Jeon, S.H. Hahn, K.I. You, K.D. Lee, J.K. Park, G.S. Yun, H.K. Park The Korea Superconducting Tokamak Advanced Research (KSTAR) has expanded its Hmode operational space to higher beta and lower internal inductance, moving toward design target operation. Plasmas have reached normalized beta of 1.9, stored energy of 340 kJ, and energy confinement time of 171ms evaluated by EFIT reconstructions. Advances from the fall run campaign will be reported. Rotating modes having n = 1, 2 tearing parities are observed by internal and external measurements and their characteristics and stability dependence on plasma rotation profile are analyzed and compared to initial observations. Initial alteration of the plasma rotation profile by applied nonaxisymmetric fields is investigated and has characteristics of nonresonant braking. Computation of active RWM control using the VALEN code examines the impact of available sensors for control. Both offaxis and midplane sensors are analyzed, and with offaxis sensors the mode can be stabilized up to normalized beta of 4.5 (C{\_}beta = 86{\%}) and up to 3.6 (44{\%}) with and without compensation of the prompt applied field of the control coils from the sensors, respectively. Power and bandwidth requirements for RWM stabilization are also calculated by including sensor noise and power supply time delay. [Preview Abstract] 

BP8.00108: Turbulence study via 2D microwave imaging reflectometry system on KSTAR Woochang Lee, J. Leem, M. Kim, G.S. Yun, H.K. Park, Y. Nam, Y.G. Kim, H. Park, K.W. Kim, C.W. Domier, N.C. Luhmann, Jr. A microwave imaging reflectometry (MIR) system [1] for KSTAR has been developed to study the turbulence based transport physics based on electron density fluctuation measurement in 2D (radial and poloidal). Twofrequency source will be introduced for probing two adjacent Xmode cutoff layers, simultaneously. A poloidal array of 16 detectors enables 2D imaging of the electron density fluctuations of the poloidal cross section. In this paper, test results of the system characteristics such as the spatial coverage and system resolutions using corrugated metal targets in the laboratory will be presented. In addition, descriptions of the twofrequency probing source, optics, detector array, and electronics will be provided. Preliminary measurements of the density fluctuations from 2012 campaign also will be reported.\\[4pt] [1] H. Park et al, Rev. Sci. Instrum. \textbf{74}, 4239 (2003). [Preview Abstract] 

BP8.00109: Measurements of internal magnetic structures from neutral beam emission spectra in KSTAR J. Ko, J. Chung, M. Song, K.I. You The magnetic pitch angle and the magnitude from magnetically confined fusion devices are measured by fitting the beam emission spectra under the motional Stark effect (MSE). Initial values for the free parameters in the complicated raw spectra are obtained from and constrained by the MSE model in the Atomic Data and Analysis Structure (ADAS) which uses a collisionalradiative model with level populations nlmresolved up to n = 4 and a simple born approximation for ionimpact cross sections. This technique is examined for the MSE spectra taken from the KSTAR plasma discharges and its validity and applicability are discussed to directly infer the internal magnetic field structure with a wide range of pitch angles. The sensitivity of EFIT reconstruction on these internal magnetic data is also discussed. [Preview Abstract] 

BP8.00110: Characteristics of EGAMs in EAST tokamak under ICRF Hmode Ah Di Liu, Chu Zhou, Xiao Hui Zhang, Jian Qiang Hu, Hong Li, Tao Lan, Jing Lin Xie, Chang Xuan Yu, Wan Dong Liu Doppler reflectometer is common plasma diagnostic used in magnetic confinement devices to measure density fluctuations and poloidal flow velocity. Two set of Doppler reflectometer (Qband {\&} Vband)were installed on EAST tokamak for the first time. A coherence mode with frequency of 20$\sim $50kHz was observed both on Doppler reflectometer and magnetic coils during ICRF Hmode on EAST. It appeared as zerosymmetric peaks in the spectrum of Doppler backscattering phase signal, implying that the density fluctuation has a standing wave structure with frequency not changing with the plasma rotation. The toroidal mode number is zero according to the magnetic coils. This feather was not observed on ECE and softX signals and there isn't obvious relationship between the mode appearance and the neutrons and hardX signals. Unlike the usual Geodesic Acoustic modes (GAM) in the edge plasma under Lmode, it was found that the mode only appeared in the core regime under Hmode through the raytracing code. The mode is suspected to be the energetic ion induced GAM. [Preview Abstract] 

BP8.00111: Investigation of locked mode thresholds on JTEXT tokamak Nengchao Wang, Yonghua Ding, Bo Rao, Wei Jin, Qiming Hu, Bin Yi, Quanlin Li, Wubing Zeng, Ge Zhaung Locked mode thresholds have been studied by applying externally resonant magnetic perturbations (RMPs) on the JTEXT plasma. The JTEXT RMPs can be either induced by a set of invessel saddle coils (named as DRMP) which is now operating in DC mode and produces mainly 2/1 perturbations, or by another set of saddle coils located outside the vacuum vessel (named as SRMP) which produces 2/1, 3/1 and other higher poloidal mode perturbations, or by both sets. The experiments on searching for locked mode thresholds by adjusting the DRMP has been carried out with various plasma parameters, including plasma current, toroidal magnetic field and line averaged electron density. It's verified that the scaling of JTEXT locked mode thresholds is similar to those of other conventional tokamaks. In the JTEXT Ohmic discharges with the same plasma parameters, the locked mode thresholds founded by applying both DRMP and SRMP fields are lower than those obtained by implementing DRMP alone. More detailed experimental results and the analysis will be presented in the meeting. [Preview Abstract] 

BP8.00112: The generation and radial propagation of geodesic acoustic mode in HL2A and HT7 tokamak T. Lan, D.F. Kong, A.D. Liu, H.L. Zhao, H.G. Shen, H. Li, W.D. Liu, C.X. Yu, J. Cheng, L.W. Yan, J.Q. Dong, W.Y. Hong, W. Zhang, R. Chen, G.S. Xu, B.N. Wan Two geodesic acoustic modes (GAMs) with different mode frequencies, named as high frequency GAM (HFGAM) and low frequency GAM (LFGAM), are observed in the edge of HL2A and HT7 tokamaks. The mode frequencies of these two GAMs are constant in the whole measurement range. The radial wavenumber profiles of these two GAMs are measured. The radial wavenumber of HFGAM branch keeps positive, which means propagating outward, and become larger when radial position increasing. The radial wavenumber of LFGAM changes sign at about radial position $ra=0.8\rm{cm}$ from negative to positive. The envelop analysis applied on LFGAM and HFGAM shows that the LFGAM is generated locally and HFGAM comes from the deeper plasma. [Preview Abstract] 

BP8.00113: Large MgB$_2$ Superconducting Coils for the Ignitor Experiment A. Tumino, G. Grasso, B. Coppi Intermediate temperature, superconducting cables have been adopted for the fabrication of the largest poloidal field coils of the Ignitor experiment. This is an important step to achieve better duty cycles in Ignitorlike machines with innovative magnet technologies compared to traditional superconductors. The commercially available MgB$_2$ strands manufactured by Columbus Superconductors meets the target specifications for the considered coils, about 5 meters of outer diameter and maximum field on the conductor below 5 T, and they are also compatible with the Ignitor cryogenic system, which is designed to cool the machine at 30 K, although MgB$_2$ may use colder gas at 10 K. The technical feasibility of these coils, as well as their stability and protection in the unlikely case of its quench, has been studied. The final design includes about 300 MgB$_2$ multifilamentary strands of 1 mm in diameter and a copper pipe for the Hegas flow in the center. A mockup cable has been manufactured. Measurements of the critical current $J_c$ as a function of magnetic field and temperature have been done for the cable bent to a curvature radius of 20 cm and compared to the results of a straight sample. The feasability of the manufacturing and jacketing processes has thus been demonstrated. [Preview Abstract] 

BP8.00114: Ignition and other Plasma Regimes for the Ignitor Experiment A. Airoldi, G. Cenacchi, B. Coppi, P. Detragiache Ignitor was the first, and presently is the only experiment designed to reach ignition conditions in a DT plasma. The reference scenario at the maximum parameters of 13 T and 11 MA achieves ignition with ohmic heating only or with the contribution of modest amounts of ICRH auxiliary heating. Scenarios that are less demanding for the machine have been considered as well. Thanks to the flexibility of the Poloidal Field System, Ignitor is capable of producing a variety of equilibrium configurations (i.e., ``extended limiter'' or Double Xpoint) over a wide range of magnetic fields (8 to 13 T) and plasma currents (5 to 10 MA). The analysis by means of the 1 1/2D transport code JETTO, without considering the access to an enhanced confinement regime, indicate the possibility of producing considerable amounts of $\alpha$power in DT plasmas.\footnote{A. Airoldi, et al., \itshape Proceed. EPS Conf., \normalfont paper PI196, 2006.} The available ICRH power is expected to allow access to improved confinement regimes, for which a 0 dimensional analysis has been carried out that shows the range of plasma parameters to be expected in various cases. An updated and comprehensive review of all the considered operational scenarios for Ignitor scenarios is presented. [Preview Abstract] 

BP8.00115: Ignitor Duty Cycles and New Configuration of Magnet Cooling Channels A. Bianchi, B. Coppi The duty cycles of the Ignitor machine depend mainly on the cooling time of the copper plates that are the conducting components of the toroidal magnet. Taking into account that the temperature propagates through a diffusion process a new configuration for the cooling channels has been devised that minimizes the distance between the region (adjacent to the central solenoid) where the maximum temperature is produced and the region that is reached by the coolant. At the same time the structural integrity of the magnet plates is maintained and the stress distribution in the socalled Cclamps that contain the toroidal magnet is improved by the new distribution of the cooling cavities within them. For the most extreme operation parameters considered the cooling time of 5 hours is reduced by about a factor 2. [Preview Abstract] 

BP8.00116: Construction of a Fullsize Component of the ICRH System S. Mantovani, M. Sassi, B. Coppi The ICRH system is an important component of the Ignitor project and all efforts have been made to ensure that its design takes into account the construction experience gained in the most advanced laboratories. The system is designed to operate over a frequency range 80120 MHz, which is consistent with the use of magnetic fields in the range 913 T. The maximum delivered power ranges from 8 MW (at 80 MHz) to 6 MW (at 120 MHz) distributed over 4 ports. Since the transition from a detailed design to the actual construction is not without surprises we have constructed a full size prototype of the VTL between the port flange and the antenna straps, with the external support and precise guiding system. The innovative quick latching system located at the end of the coaxial cable was successfully tested, providing perfect interference with the spring BeCu electrical contacts. Special care was given to the finishing of the inox surfaces, and to the TIG welds. Vacuum levels of 10$^{6}$, compatible with the limit of material degassing, and electrical tests up to 12 kV without discharges have been obtained. A revision of the other key components of the Ignitor machine has been undertaken, taking into account the experience gained in the fabrication of the corresponding prototypes. [Preview Abstract] 

BP8.00117: Major Disruptions and Other Issues Driving the Design of the Ignitor Plasma Chamber G. Ramogida, P. Frosi, B. Coppi The Plasma Chamber of the Ignitor machine is designed according to the information available about electromagnetic loads coming from the experimental knowledge and the increasingly accurate numerical models of the eddy and halo currents resulting from the worst disruption events in existing machines. The developed models deal with static, dynamic and modal analysis. The loads during nominal operations and also those arising from plasma disruptions, by far the most important ones, have been taken into account, as well as the design problems arising from the Mo tiles in the inboard edge of the vacuum vessel, the Faraday shields covering the 6 ports devoted to the ICRH system and, finally, the reaction forces coming from the regions of constraints with the CClamps (the retaining structure that support the plasma chamber both statically and dynamically). The plasma chamber has to perform several additional functions, such as to keep the vacuum, be bakeable, and support the set of plates that carry the Mo tiles facing the plasma column. According to the present design the chamber is made of Inconel and has a thickness varying from 26 to 52 mm. [Preview Abstract] 

BP8.00118: HBTEP Program: Active MHD Mode Dynamics \& Control G.A. Navratil, S. Angelini, J. Bialek, A.H. Boozer, P. Byrne, A.J. Cole, B. Debono, K. Hammond, P. Hughes, J.P. Levesque, M.E. Mauel, Q. Peng, N. Rath, D. Rhodes, D. Shiraki, C. Stoafer, F.A. Volpe, I. Cziegler, S. Paul The HBT EP active mode control research program aims to (i) quantify external kink dynamics and multimode response to applied magnetic perturbations, (ii) understand the relationship between control coil configuration, conducting and ferritic wall effects, and active feedback control effectiveness, and (iii) explore advanced feedback algorithms. Biorthogonal decomposition is used to observe multiple simultaneous resistive wall modes (RWM) with m$<$9 and n$<$5. Transitions were observed for m/n=4/1 to 3/1 accompanied by 7/2 to 6/2. Nonrigid mode behavior is observed with independent 3/1 and 6/2 RWMs. Active MHD spectroscopy is used to study 3/1 resonant field response showing linear, saturated, and ultimately, disruptive behavior as the external field amplitude is increased. Using an improved GPU based MIMO digital control system with VALEN 3D feedback modeling, we aim to optimize modular feedback coils to control instability growth near the ideal wall limit. [Preview Abstract] 

BP8.00119: Multimode Structure of Resistive Wall Modes with a Variable Wall Geometry J.P. Levesque, J. Bialek, P.J. Byrne, B.A. DeBono, M.E. Mauel, G.A. Navratil, N. Rath, D. Shiraki An important instability that limits plasma performance in tokamaks is the resistive wall mode (RWM). When there are two or more unstable modes, or when a mode is near marginal stability, multimode effects may become important [1]. Nonuniformities in the conducting boundary break the toroidal symmetry, and can split the degeneracy of sine and cosine components of rotating modes, introducing multimode effects. We present a systematic study of multimode external kink structure and dynamics in HBTEP using a highresolution magnetic sensor set and variable conducting wall geometry [2]. Coherent, nonrigid activity of multiple simultaneous modes is observed using biorthogonal decomposition (BD) with no \emph{a priori} assumptions about mode structure. Modes are stronger when several walls sections are retracted, while spatial shapes of the dominant modes found using BD analysis do not change significantly. Secondary modes are lesssignificant with respect to the dominant mode for asymmetric wall configurations. Amplitude and rotation modulations are observed with nonuniform wall configurations, and are compared with VALEN predictions.\\[4pt] [1] A.H. Boozer, Phys. Plasmas \textbf{10} 1458 (2003) \newline [2] D.A. Maurer \emph{et al.}, Phys. Plasmas \textbf{19} 056123 (2012) [Preview Abstract] 

BP8.00120: Adaptive MultiMode Feedback Control of Magnetic Perturbations on the HBTEP Tokamak N. Rath, P.J. Byrne, B.A. DeBono, J.P. Levesque, M.E. Mauel, G.A. Navratil, Q. Peng, D. Shiraki We report the first multimode feedback studies of rotating wallstabilized kink modes in the HBTEP tokamak performed with its new, GPU based control system. The system processes up to 96 inputs from an array of magnetic pickup coils and calculates control currents for 40 magnetic saddle coils within a cycle time of 6~$\mu{}s$. A recursive highpass filter based on continuous polynomial fitting is used to separate the structure and time evolution of multiple threedimensional magnetic perturbations from the slowlyevolving equilibrium signals. Perturbations are well described by quadrature mode pairs, and their amplitude and phase is tracked and fitted recursively to a timeevolving mode rotation frequency, which is used to adjust the control output matrix to dynamically compensate for latency and amplifier response. Simultaneous control of $m/n=3/1$ and $6/2$ helical perturbations is studied as a function of edge safety factor and plasma rotation as well as other plasma equilibrium parameters. Highresolution detection using 216 poloidal and radial magnetic sensors is used to independently monitor the plasma's 3D magnetic structure during feedback control. Results are compared with previous demonstrations of singlemode feedback control and predictions from theoretical models. [Preview Abstract] 

BP8.00121: Edge biasing effects on instabilities and the plasma response to external magnetic perturbations in HBTEP Bryan DeBono, Michael Mauel, Gerald Navratil, Jeff Levesque, Niko Rath, Sarah Angelini, Paul Hughes, Qian Peng, Dov Rhodes, Pat Byrne, Chris Stoafer A biased electrode inserted into a tokamak plasma edge can be used to apply torque on the plasma and change the rotation rate of MHD instabilities, including the resistive wall mode (RWM). RWM's in HBTEP have a natural frequency of +49 kHz, however with appropriate bias the plasma rotation can be adjusted both positively and negatively. We present a study of the effect of biased plasma rotation on MHD instabilities; a comparison is made between plasma rotation rate and the plasma response to external resonant magnetic perturbations (RMP). The Boozer tokamak plasma reluctance equation $\rho=(\frac{1}{si\alpha}+1)\frac{1}{L_p}$ suggests that the plasma response to RMP's is enhanced as the toroidal torque dissapation coefficient $\alpha\rightarrow0$. Moderate biasing ($\approx$ 50V) slows down the RWM rotation to 23kHz, and an increase in the plasma responsivity to RMP's is seen. Strong positive bias ($\approx +300V$) accelerates the mode in the direction opposite to its natural rotation at $\approx$40 kHz. At this high rotation frequency the mode is being dragged at too rapid a rate for it to penetrate the wall. Therefore, the conducting shells behave like an ideal wall and a saturated ideal external kink is observed instead of a RWM. [Preview Abstract] 

BP8.00122: Initial Results from the Phantom Fast Camera on HBTEP Sarah Angelini, J.P. Levesque, M.E. Mauel, G.A. Navratil, S.F. Paul A Phantom v7.3 fast camera has been installed on HBTEP. A 656nm filter is used to ensure the light measured is due to $\mathrm{D_\alpha}$ emissions and not from other sources. Since these $\mathrm{D_\alpha}$ emissions are proportional to the neutral density and the plasma density, structural information about the plasma response and its instabilities can be reconstructed using the perturbations from the timeaveraged emission profile. In this poster, the experimental setup will be described and comparisons between data from the magnetics diagnostics and the emission fluctuations will be explored. [Preview Abstract] 

BP8.00123: Design of Wall Segments for Ferritic Wall Mode Studies on HBTEP Paul Hughes, J. Bialek, A. Boozer, M.E. Mauel, J.P. Levesque, G.A. Navratil Lowactivation ferritic steels are leading material candidates for use in nextgeneration fusion development experiments such as a prospective US component test facility and DEMO [1]. Understanding the interaction of plasmas with a ferromagnetic wall will be crucial physics for these experiments. Although there has been a linear FRWM experiment [2], the FRWM has not yet been observed in toroidal geometry. Using its highresolution magnetic diagnostics, HBTEP will explore the dynamics and stability of plasma interacting with ferromagnetic materials. We describe simple models [3] for plasmawall interaction in the presence of ferromagnetic material, and compare material options for magnetic properties, cost, and ease of fabrication. Also, initial modeling, design, and installation of moderate permeability ($1<\mu<10$) wall segments on HBTEP will be discussed.\\[4pt] [1] Kurtz, R.J., et. al. 2009 \emph{J Nucl Mater} \textbf{386388}\\[0pt] [2] Bergerson, W., et. al. 2008 \emph{Phys Rev Lett} \textbf{101}\\[0pt] [3] Kurita, G., et. al. 2003 \emph{Nucl Fus} \textbf{43} 949954 [Preview Abstract] 

BP8.00124: Harmonic magnetic field reconstruction from external sensor arrays on HBTEP Q. Peng, N. Rath, J.P. Levesque, P.J. Byrne, D. Shiraki, A. Cole, M.E. Mauel, G.A. Navratil In the vacuum region surrounding a toroidal plasma, it is natural to decompose the perturbed magnetic field in terms of an orthogonal representation of the magnetic scalar potential. In HBTEP, the relatively thin radial region between the conducting wall and the plasma surface is largeaspect ratio $(R/a\sim6)$, and as a first approximation we expand the perturbed magnetic field in a cylindrical representation, as $B=\sum_{m,n}\vec{\nabla}\psi_{m,n}$, where $\psi_{m,n}=\psi_{m,n}(r)e^{i(m\thetan\varphi)}$. Because HBTEP has more than 200 magnetic sensors distributed in both toroidal and poloidal arrays, we have been able to reconstruct the perturbed vacuum field harmonic amplitudes, $\psi_{m,n}$ as a function of time under a variety of conditions, including variations of the plasma equilibrium and the magnitude of applied error fields. Using these harmonic amplitudes, we describe how to compute the Maxwell stress tensor in the vacuum region and to estimate the net torque on the plasma exerted by the surrounding resistive wall and error field coils. [Preview Abstract] 

BP8.00125: NTV Model for RWM Feedback Control Dov Rhodes, J. Bialek, A.H. Boozer, A.J. Cole, M.E. Mauel, G.A. Navratil, N. Rath, Q. Peng Neoclassical toroidal viscosity (NTV) effects due to nonresonant applied magnetic fields have drawn attention in recent years as a potential means of introducing toroidal momentum in large tokamaks such as ITER. These effects are of particular interest at Columbia University's HBTEP facility, which specializes in the study of the resistive wall mode (RWM). The RWM has been extensively simulated in VALEN, a 3D finite element code which computes the coupling between the plasma and every conducting surface. In order to evaluate the RWM stability, VALEN depends upon a torque parameter alpha [1]. Informed computation of alpha from NTV could lead to improved RWM analysis. We develop a NTV model for computing alpha to be input into VALEN. The ultimate goal is to make use of the NTV rotation computations for real time feedback control of RWMs in HBTEP. \\[4pt] [1] A.H. Boozer, Phys. Rev. 86, 5059 (2001) [Preview Abstract] 

BP8.00126: Design of the HBTEP Shaping Coil P.J. Byrne, N. Rath, J.P. Levesque, D. Shiraki, D.A. Maurer, M.E. Mauel, G.A. Navratil The kinkmode instability is closely linked to the helicity of field lines in a toroidal plasma. Modifying this helicity will permit a new method of MHD multimode control on HBTEP. HBTEP's control coil system has allowed us to run preliminary low power shaping shots. Clear effects have been seen on the 3/1 mode despite the lower power and nonaxisymmetry of the control coil system vs. the shaping coil as designed. The HBTEP Shaping Coil will allow local, axisymmetric shaping of the toroidal flux surfaces up to and including the creation of a single poloidal field null, allowing fully diverted operation in HBTEP for the first time. The coil will allow the investigation of the effects on multimode stability of a toroidal plasma due to flux surface shaping Despite running with a poloidal field null, the plasma will maintain positional stability without the aid of active feedback. The finalized design of the capacitor power bank is also discussed. [Preview Abstract] 

BP8.00127: MultiPoint Thomson Scattering Upgrade and Measurements on HBTEP C.C. Stoafer, P.J. Byrne, B.A. DeBono, J.P. Levesque, M.E. Mauel, G.A. Navratil, Q. Peng, N. Rath, D. Rhodes, H.S. McLean, S.F. Paul A recent acquisition of the Thomson Scattering (TS) system from SSPX has allowed for significant upgrades to the TS system at HBTEP. The equipment allows for ten spatial point measurements, an improvement over the previous single point system. The installation of this new instrumentation will be described. Initial measurements of electron temperature and density will be presented. As one of few internal measurements on HBTEP, the multipoint system will enhance our equilibrium reconstruction and improve stability analysis of the HBTEP discharges. We show the additional pressure profile information will allow for a more accurate equilibrium reconstruction of the HBTEP plasmas for further understanding of the plasma characteristics during resistive wall mode (RWM) activity, and active control experiments. [Preview Abstract] 

BP8.00128: ABSTRACT WITHDRAWN 

BP8.00129: Application of the New Weiland Model for Studying Transport Barriers Arnold Kritz, Xiang Fan, Tariq Rafiq, Varun Tangri, Alexei Pankin, Jan Weiland Recent advances in the Weiland drift wave model include new correlation length and new kink (peeling) terms as well as collisions on free electrons. The new model also includes electromagnetic effects on toroidal and poloidal momentum transport. These advances make the model suitable for simulating anomalous effects in transport barriers. A description of the Weiland model content is included in the adjacent poster by T.~Rafiq {\it et al.} In this study, particle, thermal, and momentum transport coefficients are computed in systematic scans over electron and ion temperature gradients, temperature ratio, density gradient, magnetic $q$, collision frequency, trapped particle fraction, magnetic shear, Larmor radius, plasma $\beta$ and elongation. Special consideration is given to the plasma parameter scans that correspond to the plasma edge region such as large temperature and density gradients, large magnetic shear and large magnetic $q$. The transport results yielded by the new Weiland drift wave model are contrasted with the earlier version of the model. Combined with high fidelity models for neoclassical effects such as NEO and XGC0 models, it is anticipated that the new Weiland model can be used to model Hmode pedestal buildup and recovery between ELM crashes. [Preview Abstract] 

BP8.00130: Derivation and Physics Basis of MultiMode Anomalous Transport Module MMM8.1 Tariq Rafiq, Arnold Kritz, Jan Weiland, Alexei Pankin Derivation of MultiMode anomalous transport module version 8.1 (MMM8.1) is presented. The MMM8.1 module is advanced, relative to MMM7.1, through the inclusion of peeling ballooning modes, dependence of turbulence correlation length on flow shear, electromagnetic effects in the toroidal momentum diffusivity and the option to compute poloidal momentum diffusivity. The MMM8.1 includes contributions from ion temperature gradient, trapped electron, kinetic ballooning, peeling ballooning, collisionless and collision dominated MHD modes, electron temperature gradient modes and drift resistive inertial ballooning modes. In derivation of the MMM8.1, effects associated with collisions, fast ion dilution, impurity dilution, noncircular flux surfaces, finite beta, and Shafranov shift are included. Advances in the MMM8.1 module result mainly from advances in the Weiland model. The MMM8.1 can be used to compute thermal, particle, toroidal and poloidal angular momentum transport. The fluid approach which underlies the derivation of MMM8.1 is expected to reliably predict, on an energy transport time scale, the evolution of temperature, density and momentum profiles in plasma discharges for a wide range of plasma conditions. [Preview Abstract] 

BP8.00131: New predictive capabilities in PTRANSP with PTSOLVER Xingqiu Yuan, Steve Jardin, Robert Budny, Gary Staebler, Greg Hammett A new implicit transport equation solver (PTSOLVER) implemented in predictive TRANSP (PTRANSP) is used to integrate the highly nonlinear timedependent transport equations using implicit Newton iteration methods. Capabilities are extended to include density and angular momentum prediction. The new solver allows users to choose between different transport models via a standard namelist input. A wide range of neoclassical and/or turbulent models or semiempirical, including TGLF choices are available. Extensive benchmark test runs have been performed with PTSOLVER using the TGLF parallelized over fluxsurfaces and wavenumbers. A combined number of CPUs up to 128 have been used. The new solver is robust, efficient, and allows large timesteps to be used. PTRANSP predicted temperatures have also been compared with experimental data for various plasma regimes, and good agreement has been achieved. [Preview Abstract] 

BP8.00132: Deltaf to FullF ParticleInCell Simulation of Microturbulence in Tokamaks W.W. Lee, S. Ethier, J. Ganesh The use of a generalized weightbased particle simulation scheme suitable for simulating tokamak turbulence is reported. The scheme, which is a generalization of the perturbed distribution schemes developed earlier for PIC simulations, is now capable of handling the full distribution of the particles in the simulation. Specifically, we can simulate both the deltaf and the fullF particles within the same code. Its development [1] is based on the concept of multiscale expansion, which separates the scale lengths of the background inhomogeneity from those associated with the perturbed distributions, and on the fact that the intrinsic particle noise level is troublesome only in the beginning of the simulation, where the signal to noise ratio is low. But, when the signal to noise ratio becomes higher afterwards, we can gradually turn on the the fullF particles without interfering with the ensuing fluctuations. We will report on the simulation studies using GTC [2] for the ion temperature gradient (ITG) driven instabilities in the presence of zonal flows. The physics of steady state transport in tokamaks will be discussed.\\[4pt] [1] W. W. Lee, T. G. Jenkins and S. Ethier, Comp. Phys. Comm. 182, 564 (2011).\\[0pt] [2] Z. Lin, T. S. Hahm, W. W. Lee, W. M. Tang, R. White Science 281, 1835 (1998). [Preview Abstract] 

BP8.00133: A quantitative study of parallel electron heat flow along magnetic field lines Mukta Sharma, E.D. Held, J.Y. Ji A code that solves the coupled electron drift kinetic and temperature equations has been written to study the effects of collisionality and particle trapping on temperature equilibration along magnetic field lines. A ChapmanEnskoglike approach is adopted with the time dependent distribution function written as the sum of a dynamic Maxwellian and a kinetic distortion expanded in Legendre polynomials. The drift kinetic equation is solved on a discrete grid in normalized speed and an FFT algorithm is used to treat the onedimensional spatial domain along the magnetic field. The dependence of the steadystate temperature on collisionality and magnetic well depths is discussed in detail. [Preview Abstract] 

BP8.00134: ABSTRACT WITHDRAWN 

BP8.00135: Wavenumberresolved turbulence investigations using Doppler reflectometry in the ASDEX Upgrade tokamak and comparison to numerical simulations Tim Happel, Alejandro Ban\'on Navarro, Garrard Conway, Clemente Angioni, Tobias G{\"o}rler, Frank Jenko, Francois Ryter, Ulrich Stroth Turbulence is known to cause substantial particle and heat losses from magnetically confined fusion plasmas. Different types of turbulence can (co) exist, for example iontemperaturegradient and trapped electron mode turbulence at large to intermediate scales along with electrontemperaturegradient turbulence at small scales. For the identification of the prevailing type of turbulence and its dependence on plasma parameters, scaleresolved measurements and comparison to numerical simulations are necessary. To this end, a newly installed optimized Doppler reflectometer is used to investigate core turbulence properties in the ASDEX Upgrade tokamak. In particular, the perpendicular electron density turbulence structure scale is scanned between $k_\perp = 5$  $25\ \mathrm{cm}^{1}$, yielding radially resolved turbulence amplitude measurements. Dedicated discharges have been performed in which electron heat flux and temperature gradients have been varied to excite different types of turbulence. Related numerical modeling is performed by means of linear and nonlinear gyrokinetic GENE simulations. Beyond the primary goal of turbulence type identification, comparisons of fluctuation amplitudes and spectral indices for the different physical scenarios are presented. [Preview Abstract] 

BP8.00136: Measurement of the transport characteristic using modulation ECH in high ion temperature plasma on LHD Hayato Tsuchiya, Masaki Osakabe, Hiromi Takahashi It is important issue to make realize the high temperature plasma in fusion oriented plasma devices including Large Helical Device (LHD), to demonstrate the ability of realizing reactor relevant plasmas. On LHD, the high ion temperature discharge is achieved after a carbon pellet injection into the plasma which is maintained by subsequent radial Neutral Beam Injection (NBI). At the high ion temperature discharge, the ion temperature radial profile often shows the flatting shape at the central region. The flatting profile is considered to be a factor that suppresses the value of the ion temperature at center. The experiment results using modulation electron cyclotron heating (ECH) to investigate the mechanism of central flatting, will be reported at DPP12. Although the ion temperature profile and the electron temperature profile are not necessarily similar at the time of high ion electron discharge, the structure of magnetic field line, which could determine the temperature profile and transport, can be investigated using propagation of electron heat pulse. As primary result, there is a possibility that the ion temperature flatting is caused by generation of the magnetic islands in core region. [Preview Abstract] 

BP8.00137: Survey of Electron Heat Diffusion Driven by Sawtooth Crashes in JTEXT Tokamak Jian Chao Li, Xiao Qing Zhang, Bo Rao, Yong Hua Ding, Ge Zhuang A soft Xray diagnostic system has been established on the JTEXT tokamak aiming to observe and survey the MHD activities, in particular, sawtooth behavior. The system consists of 8 cameras stretching to 128 collimated viewing chords which can cover the cross section of the tokamak. Investigation and analysis of the propagation of heatpulses due to sawtooth crashes can provide the possibility to evaluate the electron heat diffusivity $\chi _{ep}$. The value deduced by heat pulse measurements on JTEXT tokamak is about 7$\sim $18 m$^{2}$/s, 4 $\sim $ 9 times of $\chi _{e}$ ($\approx $2 m$^{2}$/s) which is predicted by power balance calculations. By applying externally resonant magnetic perturbations (RMPs), it is found that $\chi _{ep}$ is lower than that value without RMPs. More experimental results and the analysis will be presented in the meeting. [Preview Abstract] 

BP8.00138: Temperature gradient reversals in Boussinesq fluid between Kelvin's Cat's eye critical layers Grigori Kotovsky, Mikhail Malkov, Patrick Diamond We study a possibility that shear layers reverse local temperature gradient. First, we generalize a well known Kelvin's cat's eye nonlinear solution for a shear layer to the case of a Boussinesq fluid with temperature gradient and zero thermoconductivity. Next, we construct an approximate solution for a pair of shear layers (jet). The temperature gradient between the layers is opposite to that outside of them. From a given thermal flux across the fluid layer, a region with the negative thermal conductivity is formed between the shear layers. However, the flow within this region is likely to be unstable (for finite thermoconductivity) and should be replaced by a solution with the constant temperature. If the temperature contrast across the fluid layer is fixed, the entire fluid layer is split by the shear flow into a region with the flat temperature gradient and into adjacent regions with temperature gradients steeper than they would have in the flowfree case. We discuss the relevance of this flow configuration to the LH phases of plasma confinement (corepedestal adjacent domains) and to the temperature pinch effect. [Preview Abstract] 

BP8.00139: A Quasilinear Formulation of Turbulence Driven Current C.J. McDevitt, X.Z. Tang, Z.H. Guo Noninductive current drive mechanisms such as the familiar bootstrap current correspond to an essential component to the realization of steady state tokamak operation. In this work we discuss a novel collisionless mechanism through which a mean plasma current may be driven in the presence of microturbulence (as seen in [1]). In analogy with the traditional bootstrap current drive mechanism, in which the collisional equilibrium established between trapped and passing particles results in the formation of a steady state plasma current, here we show that velocity space scattering by drift wave microturbulence is capable of modifying the equilibrium between trapped and passing particles leading to the generation of a mean plasma current. In the collisionless limit, this current drive mechanism can in turn be balanced either by turbulence mediated electronion momentum exchange or radial electron momentum transport. A mean field formulation is utilized to incorporate the above components into a unified framework through which both collisional as well as collisionless current drive mechanisms may be selfconsistently treated. \\[4pt] [1] W. X. Wang et al., 53rd APSDPP, Salt Lake City, Utah, 2011 [Preview Abstract] 

BP8.00140: Nonaxisymmetry Effects in Neoclassical Transport Simulations E.A. Belli, J. Candy Toroidal nonaxisymmetry effects are implemented in the driftkinetic neoclassical code NEO. Important tokamak edge effects, such as magnetic field ripple, caused by the discreteness of the toroidal field coils, and imposed magnetic perturbations are studied. The equilibrium is generated using a new 3D local analytic equilibrium solver, analogous to a 3D extension of the Miller formalism for shaped axisymmetric equilibria, based on the formalism developed by Hegna [1]. Unlike a global numerical equilibrium solver, this allows for systematic studies of the effects of 3D fluxsurface shaping parameters. Initial studies focus on quasisymmetric configurations, for which the neoclassical transport is intrinsically ambipolar. The analytic development of a consistent formulation for inclusion of the radial electric field is considered. \vskip0.5pt\noindent [1] C.C. Hegna, Phys. Plasmas \textbf{7}, 3921 (2000). [Preview Abstract] 

BP8.00141: Changes to neoclassical flow and bootstrap current due to a steep density gradient Matt Landreman, Darin Ernst In a tokamak pedestal, radial scale lengths can become comparable to the ion orbit width, invalidating conventional neoclassical calculations of flow and current. Here, we generalize neoclassical calculations to allow radial density and electron temperature scale lengths as small as the ion orbit width [1], considering a relatively weak ion temperature gradient so the distribution remains nearly Maxwellian. In this ordering, nonlocal effects alter the magnitude and poloidal variation of the flow and current. The approach is implemented in a new global $\delta f$ continuum code using the full linearized FokkerPlanck collision operator. Arbitrary collisionality and aspect ratio are allowed as long as the poloidal magnetic field is small compared to the total magnetic field. Strong radial electric fields, sufficient to electrostatically confine the ions, are also included. In contrast to conventional neoclassical theory, we find analytically and numerically that a steep density gradient causes the parallel and poloidal flow coefficients to differ from each other, acquire poloidal variation, and possibly change sign.\\[4pt] [1] Landreman and Ernst, arXiv:1207.1795v1. [Preview Abstract] 

BP8.00142: Electron and Ion Channel Transport Barriers: Initiation and Dynamical Coevolution and their implications for burning plasmas D.E. Newman, P.W. Terry, R. Sanchez Simple dynamical models have been able to capture much of the dynamics of the transport barriers found in many devices, however an open question has been the often disconnected nature of the electron thermal transport channel sometimes observed in the presence of a standard (``ion channel'') barrier. By adding to a simple barrier model an evolution equation for electron fluctuations we can investigate the interaction between the formation of the standard ion channel barrier and the somewhat less common electron channel barrier. Barrier formation in the electron channel is even more sensitive to the alignment of the various gradients making up the sheared radial electric field then the ion barrier is. Electron channel heat transport is found to significantly increase after the formation of the ion channel barrier but before the electron channel barrier is formed. This increased transport is important in the barrier evolution. Parameters relevant to ITER like devices will be investigated. [Preview Abstract] 

BP8.00143: Investigating nondiffusive transport in drift wave turbulence D. Ogata, D.E. Newman, R. Sanchez, J.M. ReynoldsBarredo This poster presents preliminary results on the competing characteristics of nondiffusive transport in drift wave turbulence. This work arises from previous observations of both supercritical transport in the presence of an evolving mean profile as well as subcritical transport in the presence of sheared flows. This investigation aims to quantify transport behaviors when ingredients for both supercritical transport and subcritical transport are included into a numerical model. The turbulence model used in this investigation is based on the twofield equations for drift wave turbulence in magnetized plasmas. Currently, the mean field has been implemented in an existing twofield model that couples the mean field to the evolution of perturbed density and potential. Parameters required to successfully observe supercritical transport are still being determined. Next steps include the addition of tracers to quantify nondiffusive transport behaviors and external shear flows for the subcritical component of radial transport. Transport behaviors will be discussed in terms of tracers' trajectories and the characterization of the transport based on these lagragian trajectories. [Preview Abstract] 

BP8.00144: Selfconsistent dynamics of impurities in magnetically confined plasmas: turbulence intermittency and nondiffusive transport F. Shimpei, D. delCastilloNegrete, X. Garbet, S. Benkadda, N. Dubuit Selfconsistent turbulent transport of highconcentration impurities in magnetically confined fusion plasmas is studied using a threedimensional nonlinear fluid global turbulence model which includes iontemperature gradient (ITG) and trapped electron mode (TEM) instabilities. It is shown that the impurity concentration can have a dramatic feedback in the turbulence and, as a result, it can significantly change the transport properties of the plasma. High concentration impurities can trigger strong intermittency, that manifests in nonGaussian heavy tails of the probability density functions (PDFs) of the ${\bf E} \times {\bf B}$ fluctuations and of the iontemperature flux fluctuations. At the heart of this selfconsistent coupling is the existence of inward propagating iontemperature fronts with a sharp gradient at the leading edge that give rise to instabilities and avalanchelike bursty transport. Numerical evidence of time nonlocality (i.e., history dependence) in the response of the flux to the gradient is presented. Related to this, the temporal, crosscorrelation function between the impurity flux and the impurity density gradient exhibits a delay in the response depending on the concentration of the impurity. [Preview Abstract] 

BP8.00145: Nonlocal models of nondiffusive transport in magnetically confined plasmas A. Kullberg, D. delCastilloNegrete, G.J. Morales, J.E. Maggs The standard diffusion model assumes that the heat flux is determined by the local value of the temperature gradient. Although this paradigm is highly successful, there are situations in which it does not hold; instead, the flux at a point may depend nonlocally on the gradient throughout the entire spatial domain. Examples include perturbative experiments in tokamaks and stellarators, numerical simulations of turbulent plasmas, and generalized random walk models. Going beyond the previously studied case of 1D models in slab geometry, we construct 2D nonlocal models in bounded domains. The new models incorporate effects and boundary conditions relevant to magnetically confined fusion plasmas. Analytic and numerical results are presented comparing 1D slab nonlocal models to 2D isotropic nonlocal models. Problems investigated include: profile peaking due to offaxis heating, fast pulse propagation, and heat waves. In the context of 1dimensional models, new results are presented of nonlocal transport in thermal wave resonators in bounded domains. [Preview Abstract] 

BP8.00146: Anisotropic heat transport in reversed shear configurations: shearless Cantori barriers and nonlocal transport D. Blasevski, D. delCastilloNegrete Heat transport in magnetized plasmas is a problem of fundamental interest in controlled fusion. In Ref.\footnote{ D. delCastilloNegrete, and L. Chac\'on, Phys. Rev. Lett., {\bf 106}, 195004 (2011); Phys. Plasmas {\bf 19}, 056112 (2012).} we proposed a LagrangianGreen's function (LG) method to study this problem in the strongly anisotropic ($\chi_{\perp}=0$) regime. The LG method bypasses the need to discretize the transport operators on a grid and it is applicable to general parallel flux closures and 3D magnetic fields. Here we apply the LG method to parallel transport (with local and nonlocal parallel flux closures) in reversed shear magnetic field configurations known to exhibit robust transport barriers in the vicinity of the extrema of the $q$profile. By shearless Cantori (SC) we mean the invariant Cantor sets remaining after the destruction of toroidal flux surfaces with zero magnetic shear, $q^\prime=0$. We provide numerical evidence of the role of SC in the anomalously slow relaxation of radial temperature gradients in chaotic magnetic fields with no transport barriers. The spatiotemporal evolution of temperature pulses localized in the reversed shear region exhibits nondiffusive selfsimilar evolution and nonlocal effective radial transport. [Preview Abstract] 

BP8.00147: A systematic study of tokamak pedestal instability trends using gyrokinetic simulations Weigang Wan, Alexei Pankin, Scott Parker, Yang Chen Global gyrokinetic simulations of DIIID Hmode edge pedestal show two types of instabilities: an intermediaten, high frequency mode that propagates in the electron diamagnetic direction which we identify as the ``kinetic peeling ballooning mode (KPBM),'' and a highn, low frequency mode that propagates in the ion direction which we identify as the ``ion mode.'' When the $q$ profile is flattened by the bootstrap current, the ion mode transits to kinetic ballooning mode and becomes the dominant instability. Properties of these two instabilities are studied by varying the density and temperature profiles of equilibria. It is found that the KPBM is destabilized by density and ion temperature gradient, and the ion mode is mostly destabilized by electron temperature gradient. In a more selfconsistent study, a sequence of DIIID like equilibria has been generated using the TOQ equilibrium solver. The Hmode pedestal parameters have been modified in a systematic way in order to produce equilibria with distinguishably different stability properties that have been audited with ideal MHD stability codes including BALOO, DCON, and ELITE. The MHD stability analysis of these equilibria are then compared with gyrokinetic simulations using the code GEM. [Preview Abstract] 

BP8.00148: Edge electric fields in the PfirschSchl\"uter regime and their role in the LIH transitions A.Y. Aydemir, B.N. Breizman, R.D. Hazeltine n the PfirschSchl\"uter regime, a parallel electric field can be defined unambiguously on each flux surface within the separatrix as a function of the parallel density and temperature gradients, with a finite contribution from resistive effects. The integrated potential, unfortunately, is not unique and depends on an arbitrary flux function that is traditionally determined using highorder, toroidal angular momentum transport arguments. Here this flux function and the resulting radial electric field are calculated using a variational principle. The resulting net radial electric field at the edge, defined as the flux surface average $<\!E_\psi\!>$ just inside the separatrix, exhibits a high degree of correlation with a wide range of experimental observations on the LIH transitions in various devices. In particular, dependence of $<\!E_\psi\!>$ on magnetic topology, geometric factors like the upper/lower triangularity and elongation, and the relative position of the Xpoint(s) in the poloidal plane parallels the changes in the power threshold requirements for the transitions. This agreement with experimental results lend strong support to the variational principle used to derive the fields and imply that they may indeed be an important ``hidden variable'' in the LH transitions. [Preview Abstract] 

BP8.00149: LIH Transition with Avalanche Noise C.J. Lee, P.H. Diamond, K. Miki Discharges have been observed to persist in a state subcritical to the Hmode, called Iphase, for extended periods. LH transitions occur spontaneously in this state. Iphase edges are excited by noise, due to the statistical variability of core heat avalanches arriving at the edge. This suggests that the LH transition problem should be formulated statistically, given an ensemble of colored noise tied to the mean heat flux. In this paper, we study the LH transition in the presence of a noisy mean heat flux using 0D multifield models, with special attention on the marginally subcritical state. The transition problem is formulated of the ``waiting time'' variety, studied as a function of margin below mean threshold, noise spectrum, and noise strength. Results indicate that 1/f noise, as expected for avalancheinduced flux perturbations, is more effective at triggering transitions. Our analyses of crossing rates and the effects of temporal coherence extend beyond a related analysis by Bian (PoP 2010). The effects of noise characteristics on reverse HL transition dynamics is also investigated and related 1D modeling will be discussed. [Preview Abstract] 

BP8.00150: Twofluid edge plasma stability analysis in divertor tokamak geometry Tom Neiser, Derek Baver, Troy Carter, James Myra, Philip Snyder, Maxim Umansky Plasma in the edge region of tokamaks sets a boundary condition for the core plasma and interacts with plasma facing components. Edge Localized Modes, which occur in some highconfinement mode plasmas, can restrict the pedestal height and send large heat loads to the divertor. This work applies 2DX, a code capable of solving eigenvalue problems of any fluid model [1], to the ideal magnetohydrodynamic (MHD) fluid models associated with the edge region. Currently, this code has been successfully benchmarked against linear ideal MHD codes such as ELITE [2] for simple shifted circle geometry and ballooning dominated cases of peelingballooning (PB) modes [3]. We extend this simple geometry study to peeling dominated cases before studying PB modes in the more general case of strongly shaped twofluid plasmas. Moreover, this code can be used to extend analysis of PB modes across the separatrix to assess the effect of the scrape off layer model on stability. Ultimately, this code can also be benchmarked against nonideal MHD models.\\[4pt] [1] D.A. Baver et al., Comp. Phys. Comm. 182, 1610 (2011).\\[0pt] [2] H.R. Wilson et al., Phys. Plasma 9, 1277 (2002).\\[0pt] [3] P.B. Snyder et al., Phys. Plasmas 12, 056115 (2005). [Preview Abstract] 

BP8.00151: Gyrokinetic analysis of Hmode pedestals Eric Wang, Xueqiao Xu, Jeff Candy, Siye Ding Recent advances in GYRO allow simulations to map out the linear stability of many eigenvalues and eigenvectors of the gyrokinetic equation (as opposed to only the most unstable) at low computational cost. These advances have been used to demonstrate the onset of the KBM in the pedestal DIIID shot 131997 is slightly below ideal MHD predictions, and the most unstable mode has been benchmarked against other gyrokinetic codes. The present work expands on the previous results by including physics previously neglected and extending the work to additional discharges. In particular, the effects of collisions, parallel magnetic compression ($\delta B_\parallel$), and full shaping will be quantified in relation to the previous modeling. In addition, global effects will be addressed, with attention to how the boundary conditions should be handled near the edge. Finally, results from initial nonlinear simulations will be discussed. [Preview Abstract] 

BP8.00152: Gyrokinetic particle simulation of linear instabilities in DIIID pedestal plasmas Daniel Fulton, Zhihong Lin Understanding the physics in the pedestal region of toroidal plasmas is critical to obtaining confinement with high core temperatures. The pedestal region is characterized by large gradients in pressure, temperature, and density profiles, which provide a source of free energy to drive a number of instabilities, such as ion and electron temperature gradient modes, kinetic ballooning mode, and trapped electron modes. Studying these instabilities can provide information on the limits of allowable gradients in the pedestal. In this study, we explore linear instabilities in the pedestal region of DIIID discharge 131997 using Gyrokinetic Toroidal Code (GTC). Results using parameters from a region at the top of the pedestal show the dominant mode to be a trapped electron interchange instability. We also demonstrate that nonlocal effects are important in this simulation regime. [Preview Abstract] 

BP8.00153: Kinetic effects in a tokamak pedestal: ion flow, ion heat transport, and bootstrap current Peter J. Catto, Felix I. Parra, Grisha Kagan, Matt Landreman, Jeff Parker, Istvan Pusztai We consider the effects of a finite pedestal radial electric field on ion orbits using an approach that properly determines the localized portion of the ion distribution function in the banana regime in the small aspect ratio limit. We then solve the modified kinetic equation to retain finite \textbf{E}$\times $\textbf{B} drift departures from flux surfaces by a procedure allows a clear distinction between transit averages and flux surface average. The rapid variation of the poloidal ion flow coefficient as well as the electrostatic potential can modify previous evaluations of the ion particle flow in a flux surface, the radial ion heat flux, and the bootstrap current in the banana and plateau regimes for a subsonic pedestal. [Preview Abstract] 

BP8.00154: XGC1 totalf simulation of electrostatic edge turbulence and neoclassical physics with kinetic electrons and ions SeungHoe Ku, C.S. Chang, J. Seo, J. Lang, S. Parker Understanding the turbulence phenomena at the edge region of tokamak plasma is one of the most important issues for magnetic fusion and ITER. XGC1 is a totalf gyrokinetic code working on realistic tokamak geometry including separatrix, and has been upgraded for kinetic electron capability. Neoclassical, Xtransport (orbit loss) and turbulence physics are solved together. A stable logical sheath algorithm for the determination of wall sheath potential, without the actual resolution of the Debye sheath profile, has been a critical part of this development. Verification and validation activities will be reported on the electrostatic edge turbulence and neoclassical physics, with the kinetic electrons and ions. The present capability of the electromagnetic turbulence and kinetic neutrals in XGC1 will also be reported, with the nearfuture plans on resolving the existing issues. Discussions will also include the XGC1 application to the understanding of the pedestal structure, the LH transition physics, and the divertor heat load width. [Preview Abstract] 

BP8.00155: GBS: Global 3D simulation of tokamak edge region Ben Zhu, Dustin Fisher, Barrett Rogers, Paolo Ricci A 3D twofluid global code, namely Global Braginskii Solver (GBS), is being developed to explore the physics of turbulent transport, confinement, selfconsistent profile formation, pedestal scaling and related phenomena in the edge region of tokamaks. Aimed at solving driftreduced Braginskii equations [1] in complex magnetic geometry, the GBS is used for turbulence simulation in SOL region. In the recent upgrade, the simulation domain is expanded into close flux region with twistshift boundary conditions. Hence, the new GBS code is able to explore global transport physics in an annular fulltorus domain from the top of the pedestal into the far SOL. We are in the process of identifying and analyzing the linear and nonlinear instabilities in the system using the new GBS code. Preliminary results will be presented and compared with other codes if possible.\\[4pt] [1] A. Zeiler, J. F. Drake and B. Rogers, Phys. Plasmas 4, 2134 (1997) [Preview Abstract] 

BP8.00156: Linear Analysis of Drift Ballooning Modes in Tokamak Edge Plasmas Varun Tangri, Arnold Kritz, Tariq Rafiq, Alexei Pankin The Hmode pedestal structure depends on the linear stability of drift ballooning modes (DBMs) in many Hmode pedestal models. Integrated modeling that uses these pedestal models requires fast evaluation of linear stability of DBMs. Linear analysis of DBMs is also needed in the computations of effective diffusivities associated with anomalous transport that is driven by the DBMs in tokamak edge plasmas. In this study several numerical techniques of linear analysis of the DBMs are investigated. Differentiation matrix based spectral methods are used to compute the physical eigenvalues of the DBMs. The model for DBMs used here consists of six differential equations~[T. Rafiq {\it et~al.}~Phys.~Plasmas, {\bf 17,} 082511, (2010)]. It is important to differentiate among nonphysical (numerical) modes and physical modes. The determination of the number of eigenvalues is solved by a computation of the `nearest' and `ordinal' distances. The Finite Difference, Hermite and Sinc based differentiation matrices are used. It is shown that spectral collocation methods are more accurate than finite difference methods. The technique that has been developed for calculating eigenvalues is quite general and is relevant in the computation of other modes that utilize the ballooning mode formalism. [Preview Abstract] 

BP8.00157: Collective Edge Modes and Advanced Confinement Regimes Tianchun Zhou, Bruno Coppi A unified theory has been developed for the modes excited at the plasma edge that are signatures of the advanced confinement regimes (the EDA/ELMy HRegimes and the IRegime). The modes identified theoretically have traits that are consistent with or have anticipated those of the modes observed experimentally for these regimes. The QCM in the EDA HRegime is identified as a ballooning mode [1] near FLR marginal stability involving ion transverse viscosity and other dissipative effects. In the EDA Regime impurities are driven outward as the combined effects of their temperature gradients and thermal conductivity, while in the ELMy HRegime impurities are driven toward the core. In the IRegime the ``Heavy Particle'' mode [2] has a phase velocity in the $v_{de}$ direction and expels the impurities toward the plasma edge. The modes for the ELMy HRegime are also of the ballooning kind and close to conditions under which the growth rates are proportional to half power of the relevant dissipation parameters involving finite magnetic diffusivity and electron thermal conductivity and can have phase velocities in either directions.\\[4pt] [1] B. Coppi \& T. Zhou, submitted to PoP.\\[0pt] [2] B. Coppi \& T. Zhou, PoP 19, 012302(2012); Phys. Lett. A 375, 2916(2011). [Preview Abstract] 

BP8.00158: Heavy Particle Modes and Imode Plasmas M. Victora, B. Coppi, T. Zhou The excitation of a heavy particle mode [1,2] at the plasma edge is considered as the signature of the IRegime [3]. The mode phase velocity, predicted in the electron diamagnetic velocity direction, was confirmed by the experiments [4]. The outward impurity transport produced by this mode is consistent with the observation that impurities accumulate at the edge in the IRegime, a feature not present in the EDA or Elmy HRegime. The plasma spontaneous rotation in the ion diamagnetic velocity direction is also consistent with the mode phase velocity direction, according to the Accretion Theory [5] of this phenomenon. In accordance with our theory, the IRegime exhibits a temperature pedestal at the edge but no density pedestal as the mode excitation involves large values of $d\ln T_i/d\ln n_i$. A correlation of the values of the observed poloidal magnetic field fluctuations with those of the derived density fluctuations is provided by the same theory.\\[4pt] [1] B. Coppi et al., Phys. Rev. Lett. 17, 377 (1966).\\[0pt] [2] B. Coppi and T. Zhou, Phys. Lett. A 375, 2916 (2011); PoP 19, 012302 (2012).\\[0pt] [3] A. Hubbard et al., PoP 18, 056115 (2011).\\[0pt] [4] I. Cziegler (2010).\\[0pt] [5] B. Coppi, Nucl. Fusion 42, 1 (2002). [Preview Abstract] 

BP8.00159: On relaxing the Boussinesq approximation in scrapeoff layer turbulence (SOLT) model simulations D.A. Russell, D.A. D'Ippolito, J.R. Myra In the Boussinesq approximation, spatial variations in the plasma density are ignored in the convection of vorticity, leading to an equation of evolution for n$\nabla ^{2}\phi $ rather than $\nabla \cdot $(n$\nabla \phi )$, where n and $\phi $ are the density and potential. In the blobdominated turbulence of the near edge and SOL, density and potential fluctuation scales are similar, making this approximation hard to justify. The shortcomings of the approximation have been shown in studies of isolated blob motion [1], while recent studies of SOL turbulence suggest a relatively weak effect [2]. The numerical hardships and physical advantages of relaxing the approximation in the SOLT model [3] are discussed. On the algorithmic side, a Poisson solve for the potential becomes n$\nabla ^{2}\phi +\nabla $n$\cdot \nabla \phi =\rho $, to be solved for $\phi $ at each time step, given the evolved \textit{turbulent} fields n and $\rho $. We present multigrid relaxation and direct (sparse matrix) methods for doing so. Eliminating the approximation allows us to add physics to the SOLT model that could not otherwise be included, such as \textit{selfconsistent} ion diamagnetic drift evolution.\\[4pt] [1] G. Yu et al., Phys. Plasmas \textbf{13}, 042508 (2006).\\[0pt] [2] K. Bodi et al., 38$^{\rm th}$ EPS Conf. Plasma Phys. (2011).\\[0pt] [3] D.A. Russell et al., Phys. Plasmas \textbf{16}, 122304 (2009). [Preview Abstract] 

BP8.00160: Kineticbased layer response to RMPs J.D. Callen, C.C. Hegna, A.J. Cole Plasma toroidal rotation can prevent reconnection of resonant magnetic perturbation (RMP) fields near rational surfaces. A low collisionality kinetic toroidal model of RMPflutterinduced electron density and thermal transport in toroidally flowing plasmas has been developed [1]. Since this electron transport is nonambipolar, it produces a cocurrent toroidal torque on the plasma. This low collisionality torque differs from fluidbased cylindrical results [2] in three key ways: the effective electron collision frequency is increased because only untrapped electrons carry parallel currents, this effect increases the singular layer width, and electron temperature gradient effects are included. A $T_e$ gradient torque is caused by the parallel electron thermal force which is usually neglected in Ohm's law. It changes the perpendicular electron flow where the torque at the rational surface vanishes to where $(e/T_e)(d\Phi/dr)=d\ln p_e/dr+c_T d\ln T_e/dr$ in which $c_T$ is 0.71 for Z=1. The $c_T\neq 0$ effect moves the radial location for RMP field penetration and hence reconnection to smaller radii relative to theories [2] that neglect the thermal force.\\[4pt] [1] J.D. Callen, A.J. Cole and C.C. Hegna, UWCPTC 1115R (2012).\\[0pt] [2] F.L. Waelbroeck et al., Nucl. Fusion 52, 074004 (2012). [Preview Abstract] 

BP8.00161: Spontaneous Rotation as a Recoil ProcessNovel Experimental Evidences and Consistency with the Tenets of the Accretion Theory B. Basu, B. Coppi, T. Zhou The Accretion Theory [1] of the spontaneous (a.k.a. intrinsic) rotation phenomenon observed on axisymmetric toroidal plasmas was based on the idea that angular momentum is ejected by collective modes from the plasma column and therefore the plasma rotates in the opposite direction. Until recently, the entire plasma column was observed to rotate unidirectionally and the ejection was directed to the plasma chamber, which can not be seen to counterrotate. According to recent experiments [2], pairs of adjacent regions rotating in opposite directions can emerge within a given plasma column. Thus we argue that, if the prevalent modes are excited in the narrow region within the plasma column where the radial gradients of relevant plasma parameters are significant, angular momentum can be expelled toward the outer region. Then the inner region rotates as a recoil from this expulsion, in the direction opposite to that of the rotation of the outer region. The linear and quasilinear theories of the modes involved in the relevant transport processes are given.\\[4pt] [1] B. Coppi, Nucl. Fusion 42,1 (1966).\\[0pt] [2] J. Rice et al., Nucl. Fusion 51, 083005 (2011). [Preview Abstract] 

BP8.00162: Rotation studies in electron Internal Transport Barriers on TCV Lucia Federspiel, Basil Paul Duval, Olivier Sauter, Yanis Andrebe, Stefano Coda, Alexander Karpushov This paper reports measurements of intrinsic toroidal and poloidal plasma rotation during the evolution of electron Internal Transport Barriers (eITBs) on TCV. A CXRS diagnosticbeam system provides ion parameter profiles for stationary prebarrier formation and eITB sustainment phases with a 15mm spatial resolution across the entire barrier width. This special configuration is used to assess the role of $E_r$ and $E\times B$ shearing for the eITBs sustainment and formation in TCV. Two eITBs targets were developed either by applying central counterECCD with offaxis ECH, giving a central barrier, or offaxis coECCD with central ECH/counterECCD. The first target, characterized by a central Te barrier, is used to study the evolution of the rotation and $E_r$ with respect to the development of MHD modes, ECH power and plasma density. MHD modes cause a toroidal rotation reversal leading to increasingly positive $E_r$. It is also shown that, when applying central counterECCD, a peaked counter current rotation is sustained in the core with rotation values approximately doubled compared with the ECH phase where both cases have flat $E_r$ profiles, suggesting that the $E\times B$ shearing does not influence the eITB. [Preview Abstract] 

BP8.00163: XPoint Flow Measurements at the LH Transition in ASDEX Upgrade S.H. Muller, L. AhoMantila, G.D. Conway, R.P. Doerner, A. Herrmann, C. Holland, P. de Marne, R.A. Moyer, H.W. Mueller, S. Potzel, U. Stroth, M. Tsalas, G.R. Tynan The Xpoint reciprocating Langmuir probe in ASDEX Upgrade has been recently upgraded with a new drive system and higherbandwidth measurement electronics. The horizontal plunge direction allows the probe to penetrate through both LFS and HFS at the level of the Xpoint, thus completely covering the divertor entrance. We present first measurements of density, temperature and flow profiles in different L and Hmode plasmas close to the transition. The flows are generally larger on the HFS, where the plasma is also denser and colder. Significant differences in temperature and flow patterns are observed in different plasma conditions. Ideas for upgrading the probe shaft to perform LFS and HFS measurements simultaneously for the characterization of transients will be presented. [Preview Abstract] 

BP8.00164: Toroidal Flow Shear Driven turbulence and Transport Weixing Wang, S. Ethier, F.L. Hinton, T.S. Hahm, W.M. Tang New results from global nonlinear gyrokinetic simulations with the GTS code show that strong flow shear can drive a negative compressibility mode [13] unstable in tokamak geometry in some experimentally relevant parameter regimes. The modes reside in a lowk range, similar to that of ITG mode, with smaller but almost constant growth rate over a wider k$_{\theta }$ range, while the mode frequency increases strongly with k$_{\theta }$. More interestingly, the flow shear modes show significantly finite k$_{//}$, unlike ITG and TEM. The nonlinear energy transfer to longer wavelength via toroidal mode coupling and corresponding strong zonal flow and geodestic acoustic mode (GAM) generation are shown to play a critical role in the nonlinear saturation of the instability. The associated turbulence fluctuations can produce significant momentum and energy transport, including an intrinsic torque in the cocurrent direction. Remarkably, strong ``resonance'' in the fluctuations and associated transport peaks at the lowest order rational surfaces with integer qnumber (rather than fractional), consistent with theoretical calculation. As a consequence, local ``corrugations'' are generated in all plasma profiles (temperatures, density and toroidal rotation), potentially impacting transport barrier formation near the rational surface. Discussions on flow optimization for minimizing plasma transport will be reported.\\[4pt] [1] N. Mattor and P. H. Diamond, Phys. Fluids \textbf{31}, 1180 (1988).\\[0pt] [2] P. J. Catto \textit{et al.}, Phys. Fluids \textbf{16}, 1719 (1973).\\[0pt] [3] M. Artun and W. M. Tang, Phys. Fluids \textbf{B4}, 1102 (1992). [Preview Abstract] 

BP8.00165: The effect of poloidal asymmetries on turbulent impurity transport Istvan Pusztai, Tunde Fulop, Albert Mollen We show that a poloidally varying electrostatic potential can lead to a strong reduction or sign change of the impurity peaking factor. The poloidal variation of the potential has a twofold effect. First, magnified by the charge of the impurities, it can lead to significant inout impurity asymmetry which, provided being sufficiently strong, can lead to a sign change in the impurity peaking factor in itself. Second, the sign change of the impurity peaking factor can happen at realistically low impurity asymmetry strength, aided by the $\mathbf{E\times B}$ drift of impurities in the poloidally varying equilibrium potential. The peaking factor of highly charged impurities depends mainly on magnetic shear, the forms of the ballooning eigenfunction, and the equilibrium potential. We present an approximate expression for the impurity peaking factor retaining finite $\mathbf{E\times B}$ and parallel compressibility effects. Using the properties of the full linearized collision operator for impurity self collisions we demonstrate that collisions  as well as finite Larmor radius effects  have no impact on the impurity peaking to leading order in $1/Z$, where $Z$ is the impurity charge number. [Preview Abstract] 

BP8.00166: Nonlinear gyrokinetic simulations of intrinsic rotation in updown asymmetric tokamaks Justin Ball, Michael Barnes, Felix Parra, William Dorland, Greg Hammett, Steve Cowley Experiments and theory show that tokamak plasmas with strong toroidal rotation and rotation shear can stabilize the resistive wall mode and exhibit a reduction in turbulent transport. However, using external neutral beams to inject toroidal momentum, as is done in many current experiments, would require a prohibitive amount of energy in larger, reactorsized devices. The most promising alternative to achieve significant mean plasma flow in large devices is intrinsic rotation, the rotation that is observed in the absence of external momentum injection. Recent theoretical work concludes that updown asymmetry in the poloidal crosssection of tokamaks can drive significant amounts of intrinsic rotation [1]. In this work, we extend GS2, a local delta f gyrokinetic code that selfconsistently calculates momentum transport, to permit updown asymmetric designs. We also present the results of nonlinear simulations of momentum transport in updown asymmetric tokamak designs. \\[4pt] [1] Y. Camenen, et al. ``Transport of Parallel Momentum Induced by CurrentSymmetry Breaking in Toroidal Plasmas.'' Phys. Rev. Lett. 102, 125001 (2009). [Preview Abstract] 

BP8.00167: Effect of impurities on the turbulent momentum pinch in tokamaks Felix I. Parra, Michael Barnes, William D. Dorland In tokamaks, rotation shear is not the only effect that drives turbulent momentum transport. There is a pinch of momentum due to the Coriolis force that appears in the frame rotating with the plasma [1]. This Coriolis force breaks a symmetry of the nonlinear gyrokinetic equations that makes the turbulent momentum transport vanish [2]. Interestingly, the turbulent momentum pinch vanishes for adiabatic electrons even though the symmetry of the equations is broken. We prove this cancellation for the nonlinear gyrokinetic equations. The proof also provides the circumstances under which the momentum pinch is nonzero, showing that the presence of impurities with a ratio of charge over mass $Z_s/m_s$ different from the main ion species is sufficient to drive a momentum pinch. We will confirm these results with nonlinear gyrokinetic simulations using GS2, proving that the impurities are as important for the momentum pinch as trapped electrons.\\[4pt] [1] A.G. Peeters, C. Angioni and D. Strintzi, {\em Phys. Rev. Lett.} {\bf 98}, 265003 (2007).\\[0pt] [2] F.I. Parra, M. Barnes and A.G. Peeters, {\em Phys. Plasmas} {\bf 18}, 062501 (2011). [Preview Abstract] 

BP8.00168: Turbulence, Turbulence Suppression, and Velocity Shear in the Helimak Kenneth Gentle, William Rowan, Bo Li The Helimak is an approximation to the infinite cylindrical slab with a size large compared with turbulence transverse scale lengths, but with open field lines of finite length. Radiallysegmented isolated end plates allow application of radial electric fields that drive radial currents. Above a threshold in applied voltage (driven current), the fractional turbulent amplitude is greatly reduced. Reductions are observed for both positive and negative bias over a broad range of collisionality and parallel connection length. Concurrent measurements of the ion flow velocity profile are made by Doppler spectroscopy of the argon plasma ion. Turbulence reductions are broadly correlated with reductions in radial correlation length, but not with velocity flow shear. No evidence of zonal flows has been found. The turbulence  density, potential, and temperature fluctuations, is compared with simulations from a twofluid model for this geometry, which also show reduced turbulence with bias. Work supported by the Department of Energy OFES DEFG0204ER54766. [Preview Abstract] 

BP8.00169: New pinch for the ion toroidal rotation generated by a radial pressure gradient in a tokamak Jungpyo Lee, Michael Barnes, Felix Parra Previous work has described a turbulent pinch of toroidal angular momentum due to the Coriolis drift in a rotating frame. This pinch is only valid if the ion toroidal rotation is generated by a radial electric field only. It is well known that the ion rotation has two pieces: the one generated by the radial electric field and the other by the radial pressure gradient. We propose a new pinch mechanism for the piece of the rotation generated by the radial pressure gradient, which is important for a subsonic flow or the flow in the pedestal where the radial electric field and the pressure gradient are similar in size. The pressure gradient does not modify the particle orbits but imparts rotation to the plasma due to the finite orbit width effect (e.g. a neoclassical flow), while the radial electric field changes both the orbits and the rotation. We evaluate the pinch of the piece of the rotation generated by the pressure gradient using a nonlinear gyrokinetic analysis, and compare it with the pinch due to the piece of the rotation by the radial electric field that is well described by the Coriolis drift analysis. The parallel dynamics and the trapped electron responses are important to determine the size of the pinches for ion temperature gradient (ITG) driven turbulence. [Preview Abstract] 

BP8.00170: Nonlinear ion turbulent heating in electron drift wave turbulence Lei Zhao, Patrick H. Diamond The total turbulent heat transfer is composed of quasilinear electron cooling, quasilinear ion heating, nonlinear ion heating and zonal flow frictional heating. In a previous paper [1], we discussed quasilinear turbulent heating and zonal flow frictional heating. Here we apply weak turbulence theory to calculate the nonlinear ion turbulent heating via the beat mode resonance in electron drift wave turbulence [2]. The nonlinear diffusion in velocity space, affected by E x B motion and by the parallel velocity scattering, is further analyzed. This calculation proposes and analyzes a \textit{new} collisionless turbulent energy transfer channel through nonlinear Landau damping. This process enters the electronion energy coupling. We estimate it by using the saturation balance. The results show that the collisionless turbulent energy transfer through the nonlinear Landau damping and the zonal flow frictional damping can \textit{both} be important in a low collisionality, electron heated plasma, such as ITER. \\[4pt] [1] L. Zhao and P. H. Diamond, submitted to Phys. Plasma, 2012.\\[0pt] [2] W.M. Manheimer and T.H. Dupree, Phys. Fluid, 11, 2709 (1968). [Preview Abstract] 

BP8.00171: Effects of phase mixing and resonant detuning on GAMs ChingPui Hung, Adil Hassam Geodesic acoustic modes (GAMs) are axisymmetric poloidal oscillations of plasma in tokamaks, caused by magnetic curvature and perpendicular compression of flux tubes as they move in a nonuniform magnetic field. It has been proposed\footnote{ K. Hallatschek and G. McKee, Sherwood Fusion Theory Meeting (Austin, Tx., 2011)} to drive GAMS resonantly by external drivers. For power requirements, it is important to study the dissipation mechanisms. Here we study damping from (1) phase mixing of oscillations and (2) nonlinear detuning. Phase mixing of 2D waves propagating in inhomogeneous media can result in a higher damping rate. For example, for Alfven waves propagating transverse to a phase speed inhomogenenity, the damping rate is proportional to exp[(t/$\tau )^{3}$], instead of the usual exp(t/$\tau )$, where 1/$\tau $ is proportional to the resistivity $\eta $. We study this phenomenon for Alfven waves and for GAMs. The results are verified by simulation with a dissipative MHD code. In addition, numerical simulation shows that the resonant amplification of magnetosonic waves driven at resonance is greatly inhibited by nonlinearities: the power spectrum is broader than the linear case Lorentzian. GAMs have similar mathematical structure to magnetosonic waves. The effect of nonlinearity in driven GAM systems will be examined. [Preview Abstract] 

BP8.00172: Verification of the Spectral Shift Paradigm for ExB Shear Suppression of Transport G. Staebler, R.E. Waltz, J. Candy, J.E. Kinsey Detailed study of the way in which shear in the mean field $ExB$ velocity Doppler shift impacts the nonlinear spectrum of electric potential fluctuations in gyrokinetic simulations has lead to a deeper understanding of the suppression mechanism [1]. The impact of the Doppler shear can be interpreted with a simple analytic model, which shows that the spectrum shifts in the \hbox {direction} where the Doppler shear is linearly destabilizing but nonlinear mixing recenters the spectrum about a finite radial wavenumber at \hbox {reduced} peak amplitude. This new paradigm leads to a model of the finite radial wavenumber shift induced by the Doppler shear that is solely responsible for the reduction of turbulence. Including parallel velocity shear leads to interesting asymmetries. The verification of the new model, implemented in the TGLF quasilinear transport code, with a large number of simulations with the GYRO gyrokinetic turbulence code will be presented.\par \vskip6pt \noindent [1] G.M.~Staebler, {\em et al.}, A New Paradigm for Suppression of GyroKinetic Turbulence by Velocity Shear submitted to Phys. Rev. Lett. (2012). [Preview Abstract] 

BP8.00173: Enabling Fusion Codes for Upcoming Exascale Platforms Alice Koniges, Xuefei Yuan, Wangyi Liu, Praveen Narayanan, Robert Preissl, Stephane Ethier, Weixang Wang, Stephen Jardin, Jeff Candy Emerging computational systems including multicore homogenous nodes as well as accelerated heterogeneous nodes provide new and important platforms for moving plasma modeling codes to the next level of predictive performance. We discuss the effects of these new architectures on plasma physics applications using examples from MHD, plasma turbulence, gyrokinetics, and radiation hydrodynamics. First, we profile the existing codes on current machines, to determine both scalability and bottlenecks [1]. Then, we determine how best to use ``application proxies,'' for fusion, that provide a vehicle for computational scientists to modify and test new programming models in realistic fusion code frameworks. We describe how well these application proxies mimic the performance of full fusion codes, and give examples of the use of advanced programming models to improve their performance. \\[4pt] [1] Performance Characterization and Implications for Magnetic Fusion Codesign Applications, P. Narayanan, et al. Proc. CUG 2011 [Preview Abstract] 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2022 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700