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 GP8: Poster Session III: Gyrokinetic Theory and Transport; Nonlinear Phenomena and Turbulence Theory; Laboratory Plasma Astrophysics II, Shocks; Magnetoinertial Fusion; DIIID I, Edge Plasma, ELMs, Diag. 
Hide Abstracts 
Room: Hall BC 

GP8.00001: GYROKINETIC THEORY AND TRANSPORT 

GP8.00002: Beyond linear polarization in gyrokinetic theory Alain Brizard The concept of linear gyrocenter polarization in gyrokinetic theory is generalized to include contributions from guidingcenter polarization as well as nonlinear (quadratic) gyrocenter polarization. The former polarization is obtained from Hamiltonian guidingcenter theory in which higherorder corrections due to magneticfield nonuniformity are retained [1]. The latter polarization can be derived either variationally from the cubic gyrocenter Hamiltonian [2] or directly by pushforward construction [3]. \\[4pt] [1] A.J. Brizard and N. Tronko, submitted for publication (2012).\\[0pt] [2] A. Mishchenko and A.J. Brizard, Phys. Plasmas \underline{18}, 022305 (2011).\\[0pt] [3] A.J. Brizard, Comm. Nonlin. Sci. Num. Sim. \underline {13}, 24 (2008). [Preview Abstract] 

GP8.00003: Exact momentum conservation laws for truncated gyrokinetic VlasovPoisson equations Natalia Tronko, Alain Brizard The exact momentum conservation laws are derived by Noether method for the truncated gyrokinetic VlasovPoisson equations based on a variational formulation constructed in [1]. We thus obtain results similar to our previous work [2], which may find applications in the numerical investigations of intrinsic rotation of axisymmetric tokamak plasmas by deltaf gyrokinetic simulation methods. \\[4pt] [1] A.J. Brizard, Phys. Plasmas \underline {17}, 042303 (2010). \\[0pt] [2] A.J. Brizard and N. Tronko, Phys. Plasmas \underline {18}, 082307 (2011). [Preview Abstract] 

GP8.00004: HighOrder, Conservative Discontinuous Galerkin Algorithms for (Gyro) Kinetic Simulations of Edge Plasmas Ammar Hakim, Gregory Hammett We explore algorithms developed recently for the solution of a class of problems expressible as Hamiltonian equation coupled to elliptic field equation. Examples include 2D incompressible flow, VlasovPoisson and the gyrokinetic equations. Such systems admit two quadratic invariants, energy and a second quantity, known by various names (e.g., enstrophy or entropy) in different contexts. The algorithm uses a continuous finiteelement scheme for the elliptic equation and a DG scheme for the Hamiltonian dynamics. With a proper choice of basis functions and numerical flux function both energy and enstrophy are conserved. Even with a choice of a diffusive, but more stable, upwind flux the scheme is shown to conserve energy, in addition to being enstrophy stable. For the Vlasov equation coupled to a quasineutrality condition or a Poisson equation, the total energy is conserved. The highorder accuracy of the finiteelement representation, with a hypercollision operator to handle recurrence, results in an accurate and efficient scheme. We show results from passive advection, nonlinear vortex merger (incompressible 2D hydrodynamics) and several 1D VlasovPoisson problems, including electron plasma oscillations and ion acoustic waves with quasineutrality used to determine fields. [Preview Abstract] 

GP8.00005: Extension of Discontinuous Galerkin Algorithms To Preserve the Locality of Parallel Gyrokinetic Dynamics G.W. Hammett, A. Hakim A wide range of physics problems, including gyrokinetics, have an underlying Hamiltonian structure that can be expressed in terms of a Poisson bracket, which leads to two quadratic invariants, such as the energy and enstrophy invariants in 2D hydrodynamics or HasegawaMima equations. A type of Discontinuous Galerkin (DG) algorithm has been developed in the literature that can preserve both invariants, by coupling the DG algorithm for the advection part of the problem with a continuous Finite Element Method for the elliptic field equations. This algorithm can preserve both invariants if centered fluxes are used, and still preserves energy conservation even if upwind fluxes are used. However, when applied to gyrokinetics, the weak form of the continuous finiteelement part of the algorithm causes a coupling along the field line that would require a full 3D elliptic solver. We show a new type of DG algorithm that allows the potential to be discontinuous along the field line, just as the particle distribution function can be, thus restoring the property that the fields in gyrokinetics can determined by a set of uncoupled 2D elliptic problems. By accounting for the deltafunction electric field as particles cross cell boundaries, energy can still be preserved. [Preview Abstract] 

GP8.00006: Tests of Limiters for Discontinuous Galerkin Advection Algorithms Seth Davidovits, Ammar Hakim, Greg Hammett In continuum kinetic plasma simulations, maintenance of the positivity of the distribution function and monotonicity (avoiding numericallygenerated oscillations) is important for a physical solution. Here, we investigate issues surrounding maintaining positivity (and the more restrictive property of monotonicity) when using a discontinuous Galerkin (DG) approach. We are particularly interested in methods that do not break conservation properties of the solution algorithm and are amenable to implementation in high dimensional spaces without prohibitive computational difficulty. While finite volume approaches keep track of a cell mean, the discontinuous Galerkin method makes use of a number of higher solution moments and interpolations to quadrature points using these moments. Because of this fact, positivity enforcing methods that are successful for finite volume means do not necessarily guarantee a positive discontinuous Galerkin solution. Performance of several different limiting schemes on some tests cases will be shown. [Preview Abstract] 

GP8.00007: Gyrokinetic Edge Turbulence Bruce Scott Edge turbulence is computed using a generalised fluxtube deltaf gyrokinetic formulation. Energetic consistency in the model is reviewed. Gradient terms provide drive, and collisions and subgrid dissipation provide saturation. Full fluxsurface edge turbulence results are obtained with realistic scale separation. Instabilities occur at the scale of several ion gyroradii, while nonlinear redistribution fills the spectrum. A key feature of edge turbulence is the strong nonlinearity: all available degrees of freedom are maintained at finite amplitude, most especially a longwave shearAlfven component. Transport scaling of the turbulence is determined more by saturation through this component than the drive. In the turbulence, the dominant drive is by a longwave MHD which is self maintained but is very weak in the linear regime. The resulting scaling qualitatively diverges from the linear growth rates. Electron trapping is found to enhance the turbulence without changing its character, which is very similar to the results of gyrofluid computations at the same parameters. [Preview Abstract] 

GP8.00008: Extended gyrokinetic field theory for timedependent magnetic confinement fields Hideo Sugama, Tomohiko Watanabe, Masanori Nunami In conventional gyrokinetic theories, the gyrocenter phasespace variables are defined by using the background magnetic confinement field that is assumed to be independent of time. Recently, several studies have been trying to perform longtime gyrokinetic turbulent transport simulations up to the transport time scale although they still use the abovementioned assumption. However, the background or equilibrium magnetic field changes along with the pressure profile on the transport time scale. Therefore, in order to accurately describe the longtime behaviors of the gyrokinetic turbulence, we need to treat the timedependent background field and show how to determine its time dependence. In this work, the gyrokinetic field theory [1] is extended to derive the condition which determines the timedependent magnetic confinement fields in axisymmetric toroidal systems. Then, conservation laws of energy and momentum including the part of the timedependent background fields are naturally derived from the extended gyrokinetic field theory.\\[4pt] [1] H. Sugama, Phys. Plasmas \textbf{7}, 405 (2000). [Preview Abstract] 

GP8.00009: Gyrokinetic simulations of electrostatic drift modes with statistic neoclassical islands Peng Jiang Statistic neoclassical islands have been added to he gyrokinetic toroidal code (GTC). And the influence of neoclassical islands on the stability of electrostatic drift modes is studied in toroidal geometry. The main effect of islands on equilibrium is the modification on the density and temperature gradients, which induces the new equilibrium particle distribution function. Linear and nonlinear gyrokinetic simulations are used to clarify the influence of the new equilibrium on electrostatic drift modes. [Preview Abstract] 

GP8.00010: Compressive fluctuations in astrophysical gyrokinetic plasmas Anjor Kanekar, William Dorland, Alexander Schekochihin, Noah Mandell In the gyrokinetic description of plasma, at length scales larger than ion larmor radius, compressive fluctuations are passively advected by Alfvenic turbulence [A. A. Schekochihin et al. ApJS 182 310]. Linearly, these fluctuations are Landau damped, with a damping rate proportional to their wavenumber along the guide field. However, the nonlinear behavior of these fluctuations is still poorly understood. Particularly, whether compressive fluctuations undergo a parallel cascade is still an open question. We have developed a new code using CUDA for a graphics processor, which solves reduced equations rigorously derived from gyrokinetics for these scales. We present theory and numerical results from the new code exploring the question of parallel cascade for compressive fluctuations. [Preview Abstract] 

GP8.00011: Gyrosymmetry: global considerations Joshua Burby, Hong Qin In gyrokinetic theories, the gyrophase is measured with respect to a unit vector field defined on the physical domain that is everywhere perpendicular to the magnetic field. In some cases, such a perpendicular unit vector cannot be defined globally, meaning the gyrophase itself loses its global meaning. I will present the general condition for when this deviant behavior can occur. I will then justify the condition in two ways, first by making a physically appealing analogy to the physics of Dirac monopoles, and then by describing the relevant theorem from the theory of characteristic classes. This will lead to a discussion of assessing global existence of a perpendicular unit vector in a number of examples, including toroidal confinement devices. In particular, I will demonstrate that in tokamaks, global perpendicular unit vectors always exist. Finally, I will discuss why a global convention for measuring gyrophase is unnecessary for the validity of the guiding center expansion of the single particle equations of motion. To emphasize this last point, I will demonstrate how a gyrogauge invariant guiding center Lagrangian becomes manifestly independent of any choice of perpendicular unit vectors upon changing to cartesian position and velocity coordinates. [Preview Abstract] 

GP8.00012: Role of stable modes in zonal flow regulated ITG turbulence Kirit Makwana, Paul Terry, David Hatch, M.J. Pueschel Stable modes are studied in zonal flow regulated ITG turbulence using the gyrokinetic code GENE. Proper orthogonal decomposition (POD) modes are employed to investigate the eigenmode space of the distribution function. Both the unstable and stable POD modes show strong nonlinear energy transfer via three wave interactions that include zonal modes. The zonal mode itself absorbs a small fraction of the energy injected by the unstable mode. The remaining energy is deposited in the stable modes of nonzonal wavenumbers that are involved in the three wave coupling. These stable modes lie mostly within the wavenumber range of the instability. This indicates that zonal flows mediate energy transfer from unstable to stable modes, leading to saturation. The amplitude attenuation rate (AAR) of POD modes shows an equipartition across a large range of stable modes. This rate is balanced by three wave correlations of the POD modes and their time dependent amplitudes. These correlations are large if they involve zonal modes and they also show an equipartition for higher mode numbers. A similar analysis using linear eigenmodes also shows rough equipartition among the linear modes. Thus, AAR provides a handle to collectively describe the multitude of stable modes in a gyrokinetic simulation. [Preview Abstract] 

GP8.00013: Gyrokinetic Particle Simulation of FInite Beta Microturbulence in Tokamak Plasmas Ihor Holod Recent progress in gyrokinetic simulations of plasma microturbulence using GTC code is reported. Verification of the fluidkinetic hybrid electron model is done by running simulations at different values of $\beta_e$ using Cyclone base case parameters. Finitebeta stabilization, and transition from ITG to CTEM and later to the KBM mode is observed. The crosscode benchmark of real frequency and growth rate is done demonstrating good agreement. [Preview Abstract] 

GP8.00014: Implementation of 2D domain decomposition in the UCAN gyrokinetic PIC code for nondiffusive transport studies in tokamaks JeanNoel Leboeuf, Viktor Decyk, David Newman, Raul Sanchez The massively parallel, nonlinear, 3D, toroidal, electrostatic, gyrokinetic, PIC, Cartesian geometry UCAN code, with particle ions and adiabatic electrons, has been successfully exercised to identify nondiffusive transport characteristics in DIIIDlike tokamak discharges. The limitation in applying UCAN to larger scale discharges is the 1D domain decomposition in the toroidal (or z) direction for massively parallel implementation using MPI which has restricted the calculations to a few hundred ion Larmor radii per minor radius. To exceed these sizes, we have implemented 2D domain decomposition in UCAN with the addition of the ydirection to the processor mix. This has been facilitated by use of relevant components in the 2D domain decomposed PLIB2 library of field and particle management routines developed for UCLA's UPIC framework of conventional PIC codes. The gyroaveraging in gyrokinetic codes has necessitated the use of replicated arrays for efficient charge accumulation and particle push. The 2D domaindecomposed UCAN2 code reproduces the original 1D domain results within roundoff. Production calculations at large system sizes have been performed with UCAN2 on 131072 processors of the Cray XE6 at NERSC. [Preview Abstract] 

GP8.00015: High order Finite difference Constrained Transport Method for Ideal Magnetohydrodynamic Equations Qi Tang, Andrew Christlieb, Yaman Guclu, James Rossmanith A new algorithm will be used to simulate the ideal MHD equations based on AMR algorithm and a high order finite difference WENO reconstruction method [Shen, C., Qiu, J.M., Christlieb, A. J., Adaptive mesh refinement based on high order finite difference WENO scheme for multiscale simulations, JCP (2011)]. The base framework of the algorithm will be the magnetic potential advection constrained transport method (MPACT), which was originally a 2ndorder finite volume type solver for ideal MHD equations by Rossmanith, J. [An unstaggered, HighResolution Constrained Transport Method For Magnetohydrodynamic Flows, SIAM (2006)], but the treatment is significantly different. The important feature of the new algorithm will be (1) the method is finite difference type, (2) all quantities are treated as cellcentered, (3) high order (higher than 2nd) in both time and space, (4) all the quantities are nonoscillatory, (5) AMR will be used as the base framework. Convergence study will be done on the smooth problem. More 1D/2D/2.5D benchmark problems such as BrioWu shock tube, Rotor problem and Cloudshock interaction will be simulated. We expect our algorithm is robust, nonoscillatory and good at resolving solution structures, due to the very low numerical diffusion of high order scheme. [Preview Abstract] 

GP8.00016: Role of waveparticle interaction in parallel transport along open magnetic field Zehua Guo, Xianzhu Tang Ambipolar electric field is crucial in parallel transport such as the plasma flow. Our study shows that, for lowcollisionality boundary plasmas in the lowrecycling regime, the sheath potential does not obey the Bohm's relation (or its variations), but strongly couples to waveparticle interactions via electromagnetic instabilities. Unlike the collisional limit, trapped electrons due to finite ambipolar potential and source injection can only be detrapped by the waveparticle scattering processes at steady state. Therefore, to reduce trapped electrons from the source and access a stronger instability drive, the absolute value of ambipolar potential decreases. The dispersion analysis of whistler waves driven by the sharp gradient of electron distribution at the trappassing boundary shows more robust instability than the conventional temperature anisotropy driven mode. The detailed electron scattering process in given whistler waves is then analysed to account for the necessary detrapping particle flux and the associated energy flux. Combined effects of waveparticle interaction and collisions on the ambipolar potential have also been investigated with a scan of collisionality using VPIC simulation. [Preview Abstract] 

GP8.00017: NONLINEAR PHENOMENA AND TURBULENCE THEORY I 

GP8.00018: Structural stability of infinitedimensional Hamiltonian systems P.J. Morrison, G.I. Hagstrom The stability of physical systems depends on parameter values, especially values where bifurcations to instability occur. Bifurcations for finitedimensional Hamiltonian systems are detailed by the KreinMoser theorem, which says instability can only occur through collisions of positive and negative energy modes. Infinitedimensional Hamiltonian systems differ because of continuous spectra, which complicates the mathematics and the definition of signature essential to the theorem. All ideal plasma theories have Hamiltonian formulations with noncanonical Poisson brackets, which deviate from the canonical case by having a different phase space geometry and this affects the structural stability results we achieved.\footnote{G.~Hagstrom and P.~Morrison, Trans.\ Theory Stat.\ Phys.\ {\bf 39}, 466 (2011)} For the linearized VlasovPoisson (VP) equation we proved that if perturbations are dynamically accessible, bifurcations to instability only occur where the ``signature,'' sgn$(uf_0'(u))$, changes, consistent with intuition from finitedimensions. For nondynamically accessible perturbations the result fails and the VP system is structurally unstable. The methods used are strong and provided results for other systems, which will be described. [Preview Abstract] 

GP8.00019: Lagrangian, Eulerian, and Dynamically Accessible Stability of MHD flows Tommaso Andreussi, Philip Morrison, Francesco Pegoraro Stability conditions of magnetized plasma flows are obtained by exploiting the Hamiltonian structure of the magnetohydrodynamics (MHD) equations and, in particular, by using three kinds of energy principles. First, the Lagrangian energy principle of Ref. [1] is introduced and sufficient stability conditions are presented. Next, plasma flows are described in terms of Eulerian variables and the noncanonical Hamiltonian formulation of MHD [2] is exploited. For symmetric equilibria, the energyCasimir principle of Ref. [3] is expanded to second order and sufficient conditions for stability to symmetric perturbation are obtained. Then, dynamically accessible variations, i.e. variations that explicitly preserve the invariants of the system, are introduced and the respective energy principle is considered. As in Ref. [4], general criteria for stability are obtained. A comparison between the three different approaches is finally presented. \\[4pt] [1] E.A. Frieman and M. Rotenberg, \textit{Rev. Mod. Phys.}, \textbf{32} 898 (1960).\\[0pt] [2] P.J. Morrison, J.M. Greene, \textit{Phys. Rev. Lett.}, \textbf{45} 790 (1980).\\[0pt] [3] T. Andreussi, P.J. Morrison, F. Pegoraro, \textit{Phys. Plasmas}, \textbf{19} 052102\ (2012).\\[0pt] [4] E. Hameiri, \textit{Phys. Plasmas},\ \textbf{10} 2643\ (2003). [Preview Abstract] 

GP8.00020: Nonlocal, Kinetic Stimulated Raman Scattering in Nonuniform Plasmas Pavel Khain, Lazar Friedland, Arkadiy Shagalov, Jonathan Wurtele Excitation of continuously phaselocked (autoresonant) plasma waves in a nonuniform plasma via stimulated Raman backscattering is analyzed with a focus on the kinetic regime ($k\lambda _{D}\sim 1$). The dominant nonlinear effect in this regime is that of resonant particles and the plasma wave excitation is a nonlocal process involving formation and transport of the electron phase space holes. Whitham's averaged variational principle is applied in studying the coupled plasma, laser pump and seed waves dynamics. A flattop electron velocity distribution is used as the simplest model allowing a variational formulation within the water bag theory. The corresponding Lagrangian, averaged over the fast phase variable, yields evolution equations for the slow field variables. The adiabatic multiple water bag extension of the theory for application to autoresonant plasma waves in nonuniform plasmas with more realistic initial distributions is also discussed. Numerical solutions of the system of slow variational equations are compared with VlasovAmpere simulations. [Preview Abstract] 

GP8.00021: Nonlinear energization of ions by beating electromagnetic waves P.A. Zestanakis, Y. Kominis, K. Hizandis, A.K. Ram We consider the interaction of ions with two high frequency electromagnetic waves in a uniformly magnetized plasma. The beat frequency of the waves is assumed to be close to the ion cyclotron frequency while the individual wave frequencies are much higher than the beat frequency. Analytical calculations using the Lie perturbation theory show that the beat wave can nonlinearly energize ions. The energization is due to a resonant interaction of the ions with the envelope of the beat wave. The analytical analysis is facilitated by the separation in time scales between the wave frequencies and the frequency of the beat wave. We construct a set of mapping equations which helps determine the dependence of ion energization on wave parameters. The mapping equations are an efficient means for calculating the evolution of a distribution function and determining the diffusion of ions in energy. Our analytical results are in very good agreement with exact numerical simulations of particle orbits from the Lorentz equation. The theory and computational results will be discussed in detail. [Preview Abstract] 

GP8.00022: Saturation Analysis of Four Dimensional Kinetic Slab Ion Temperature Gradient Driven Turbulence David Hatch, Vasil Bratanov, Frank Jenko Standard hydrodynamic turbulence paradigms define a saturation scenario wherein energy is transferred through a broad range of inertial scales via a conservative cascade and dissipated at small scales. In contrast, recent gyrokinetic studies have shown that in plasma microturbulence the energy injection scales and dissipation scales largely overlap. This phenomenon is linked to the excitation of damped eigenmodes at the same scales as the driving instabilities. We examine a reduced (retaining only parallel velocity dynamics) kinetic model for iontemperaturegradient (ITG) driven turbulence in slab geometry in order to further elucidate these fundamental properties of plasma microturbulence. This simple model is studied numerically with a fully spectral (Fourier in space, and Hermite in the parallel velocity dimension) code in order to facilitate a detailed examination of energy transfer in a turbulent kinetic system. Connections are made between the nonlinear turbulence and the underlying linear eigenmode spectrum, which consists of an ITG mode, a stable ion sound wave, and damped Landau modes. In addition to the fundamental interest of this study, these results are expected to provide insights into possible techniques for more efficient modeling of kinetic turbulence. [Preview Abstract] 

GP8.00023: A Mechanism for $\underline{E} \times \underline{B}_0$ Structure Formation Patrick Diamond, Ozgur Gurcan, T.S. Hahm, Guilhem DifPradalier A novel mechanism for $\underline{E} \times \underline{B}_0$ staircase formation is proposed. Staircases are quasiregular patterns of strong, localized shear layers and profile corrugations interspersed with regions of avalanching. The critical question is how do such quasiregular patterns selfconsistently form. We propose a simple model based on a.) symmetry constraints on the form of the flux, b.) the existence of a fluctuation amplitude dependent time delay between the profile perturbation and the flux. The time delay leads to the development of quasiperiodic jams or clusters in the transport flux. These in turn nucleate profile corrugations and a shear layer staircase. The implication for avalanche structure will be discussed. The aim of this work is a selfconsistent treatment of the spatiotemporal structure of transport and flows. [Preview Abstract] 

GP8.00024: Structuredriven turbulence in ``No man's Land'' Yusuke Kosuga, Patrick Diamond Structures are often observed in many physical systems. In tokamaks, for example, such structures are observed as density blobs and holes. Such density blobs and holes are generated at the tokamak edge, where strong gradient perturbations generate an outgoing blob and an incoming hole. Since density holes can propagate from the edge to the core, such structures may play an important role in understanding the phenomenology of the edgecore coupling region, socalled ``No Man's Land.'' In this work, we discuss the dynamics of such structures in real space. In particular, we consider the dynamics of density blobs and holes in the HasegawaWakatani system. Specific questions addressed here include: i) how these structures extract free energy and enhance transport? how different is the relaxation driven by such structures from that driven by linear drift waves? ii) how these structures interact with shear flows? In particular, how these structures interact with a shear layer, which can absorb structures resonantly? iii) how can we calculate the coupled evolution of structures and shear flows? Implications for edgecore coupling problem are discussed as well. [Preview Abstract] 

GP8.00025: Intermittency and scaling of vorticity in driftinterchange plasma turbulence Bogdan Hnat, Paula Dura, James Robinson, Richard Dendy Vorticity plays a central role in particle and energy transport driven by fluid and drift turbulence in plasmas with magnetic fields. Characterising the largest spatiotemporal concentrations of vorticity, and quantifying the scaling of vorticity with plasma parameters and system size, is therefore important for tokamak transport studies. We address this using a modified HasegawaWakatani model, extended (J M Dewhurst et al, Phys. Plasmas 16, 072306 (2009)) to include a background magnetic field gradient. Although vorticity is defined in terms of gradients in the underlying fluid velocity, we find that the statistical properties of fluctuations in vorticity can differ significantly from those of fluctuations in velocity and density. We relate this to changes in the morphology of coherent structures within the turbulence, and to the nature of turbulent interactions  cascade, or fewwave coupling. Some of the key properties depend on the direction of the magnetic field gradient. This may give rise to differences between inboard and outboard edge plasma transport in tokamaks. [Preview Abstract] 

GP8.00026: A Hybrid Statistics/Amplitude Approach to the Theory of Interacting Drift Waves and Zonal Flows Jeffrey Parker, John Krommes An approach to the theory of driftwavezonalflow systems is adopted in which only the DW statistics but the full ZF amplitude are kept. Any statistical description of turbulence must inevitably face the closure problem. A particular closure, the Stochastic Structural Stability Theory (SSST), has been recently studied in plasma\footnote{B.~F.~Farrell and P.~J.~Ioannou, Phys.\ Plasmas \textbf{16}, 112903 (2009).} as well as atmosphericscience contexts. First, the predictions of the SSST are examined in the weakly inhomogeneous limit, using the generalized HasegawaMima model as a simple example. It is found that the equations do not admit a complete solution, as the characteristic ZF scale cannot be calculated. To address that deficiency, an analysis is performed of a bifurcation from a DWonly state to a DWZF state in the HasegawaWakatani model in order to gain analytical insight into a nonlinear DWZF equilibrium, including prediction of the charactistic scale. The calculation permits discussion of the relative importance of eddy shearing and coupling to damped eigenmodes for the saturation of the selfconsistently regulated turbulence level. [Preview Abstract] 

GP8.00027: Quantifying Properties of Collisionless Turbulence Through Wavelet Analysis Homa Karimabadi, Kai Schneider, Vadim Roytershteyn, William Daughton, Burlen Loring Recent advances in fully kinetic simulations are enabling us to conduct simulations of collisionless turbulence that span the scales from MHD down to electron kinetic scales. One of our key findings is that the cascade process in collisionless plasma turbulence leads to generation of coherent structures in the form of kinetic scale current sheets. These current sheets are in turn found to play an important role in the dissipation of the cascading energy. Wavelets are ideally suited for characterizing localized multiscale structures and have been successfully used in studies of fluid turbulence. Here we apply wavelets in characterizing four important properties of turbulence: (a) its spectral features such as scale dependent statistics and their spatial fluctuations, (b) extraction of coherent structures using thresholding of the wavelet coefficients, (c) quantification of dissipation scales, and (d) compressibility of the fluctuations. Comparisons with Fourier techniques are also made. [Preview Abstract] 

GP8.00028: Mean Field Theory for Turbulent Transport of Momentum in the Solar Tachocline PeiChun Hsu, Patrick Diamond Zonal flow formation is mainly studied in wavenumber space, i.e., as transfer of kinetic energy between scales. A description based on momentum transport in real space is in many cases more useful. The physics of turbulent momentum transport in the solar tachocline is not clear; different models assume different roles of turbulence such as constant positive or negative viscosity. Here we show that turbulent transport of momentum cannot be simply described as a Fickian diffusion process; it is sensitive to flow structure, and the transport coefficients are functions of flow shears. In this work we consider the general structure of the momentum flux for a 2D quasigeostrophic system. A modulational calculation of the momentum flux reveals both a negative turbulent viscosity and a positive turbulent hyperviscosity. While the negative viscosity phenomenon of zonal flow growth by Reynolds work is generally known, positive hyperviscosity accounts for the saturation mechanism of zonal flow growth, which can originate from a cutoff scale from coarse graining wave packets. To address more realistic problems, largescale mean shear flows are included to the zonal flowwave turbulence system and the corresponding structure of momentum flux is obtained using the method of characteristics. [Preview Abstract] 

GP8.00029: Turbulence from inverted densitytotemperature gradients in LHD W. Horton, X.R. Fu, K. Tanaka Recent experiments in Large Helical Device(LHD) show interesting ``ears'' in the plasma density profiles  density peaks at $r/a\approx 0.8$. The local maximum produces an inner region with negative $\eta_e=L_n/L_T$ and an outer region with positive $\eta_e$. The linear analysis shows that electron temperature gradient(ETG) mode is very unstable in the negative $\eta_e$ region. We perform gyrokinetic simulations of ETG modes in cylinderical geometry with and without curvature effects using density and temperature profiles from LHD experiments. Fluctuations measured by 2DPCI also found the waves rotating in the electron direction inside the ear and in the ion direction outside the density ear as expected from the dispersion relation and standard radial electric field in these discharges. We also investigate ITG/TEM and other possible modes in these experiments. [Preview Abstract] 

GP8.00030: Dynamic Plasma Screening Effects on the Elastic ElectronIon Collision in Turbulent Plasmas YoungDae Jung The dynamic plasma screening effects on the elastic electronion collision are investigated in turbulent plasmas using the secondorder eikonal method. The results show that the dynamic screening effect strongly enhances the eikonal phase shift as well as the cross section. It is also found that the dynamic screening effect decreases with increasing impact parameter. In addition, the influence of the turbulence suppresses the eikonal phase shift and cross section, especially, for small impact parameters. Moreover, it is found that the dynamic screening effect on the eikonal cross section increases with decreasing thermal energy for large impact parameters. [Preview Abstract] 

GP8.00031: Ion gyroradius effects on zonal flows in extended HasegawaMima models Stephen Gallagher, Bogdan Hnat, Colm Connaughton, Sergey Nazarenko Zonal flows are important in fusion plasma where they regulate drift wave turbulence and improve plasma confinement. Two mechanisms can lead to the creation of zonal flows: an inverse cascade of energy, similar to that observed for 2D turbulence, and a coupling between wave modes known as the modulational instability. This work focused on the modulational instability; a four mode truncation of the extended HasegawaMima system was derived to model this. The extended HasegawaMima model is more appropriate for tokamaks than its predecessors as it decouples global flows from the flux surface averaged potential of the system. In addition to this truncated model a linearised set of equations for the system has been derived and used to produce a dispersion relation. Finite difference simulations of the whole system have been used to check these models. Previous work, which has largely considered the case where the ion gyroradius has been taken to its limits, has been expanded upon to show how the ion gyroradius can effect the behaviour of drift waves. It has been shown that the ion gyroradius can be used to change the strength of the nonlinearity of the system leading to changes in behaviour that have previously been demonstrated by altering the initial amplitude of the drift wave. [Preview Abstract] 

GP8.00032: Contributions of subgridscales to energy transfer in Hall MHD turbulence Hideaki Miura, Keisuke Araki Effects of the Hall term on energy transfer in MHD turbulence is studied numerically with a view point of modeling smallscales numerically. While MHD simulation is a convenient tool to study various plasma dynamics such as fusion plasma, solar winds and so on, the (singlefluid) MHD equations do not give an appropriate description for smallscale dynamics, because some smallscale effects such as the ion skin depth (Hall term) and the finite Larmor effects are discarded. The incorrectness of smallscale dynamics can be essential when the small scales are coupled with largescales through the nonlinearity of the discarded effects. In order to study influences of the ion skin depth to larger scales, we carry out direct numerical simulations of homogeneous Hall MHD turbulence as well as homogeneous MHD turbulence. A direct comparison of the energy transfers between the two kinds of turbulence reveals that Hall term can bring about a tight coupling between large and small scales. We also show that the roles of the Hall term cannot be replaced by a simple diffusive numerical model but should be replaced as a combination of diffusive and nondiffusive parts. [Preview Abstract] 

GP8.00033: Entropic Lattice Boltzmann Simulations of MHD Turbulence George Vahala, Jeffrey Yepez, Min Soe, Linda Vahala, Armen Oganesov Lattice Boltzmann (LB) codes are ideal to study MHD turbulence since it is a mesoscopic algorithm in a higher dimensional space but whose solution in that space is far simpler to achieve that direct CFD algorithms. In particular, one is no longer handcuffed by fast magnetoacoustic waves which are sometimes filtered out by an anelastic approximation. Moreover, these LB simulations can enforce div B = 0 automatically since this arises as the trace of an asymmetric tensor. However the achievable Reynolds and magnetic Reynolds numbers are restricted by numerical instabilities. Here we consider entropic formulations of LB for MHD. For NavierStokes turbulence, an entropic scheme has permitted fully resolved simulations on 1600 x 1600 x 1600 spatial grid at a Reynolds number of 25 000. [Preview Abstract] 

GP8.00034: Frequency spectra at large wavenumbers in twodimensional HasegawaWakatani turbulence Juhyung Kim, Paul W. Terry The twodimensional HasegawaWakatani model is well known to show weak (strong) turbulence for $\alpha \gg 1(\ll 1)$, where $\alpha$ is the adiabatic parameter. Weak turbulence has narrow frequency spectra peaked at linear wave frequecies $\omega_0$. However, fluctuations in weak turbulence at large wavenumbers are thought to show broad frequency spectra with zero mean frequency, a feature of strong turbulence. We present the numerical results of frequency spectra showing that these spectra at large wavenumbers have finite mean frequencies at intermediate $\alpha \sim O(1)$. The potential fluctuation have finite mean frequencies $(\ne\omega_0)$ and broad spectral widths while the density fluctuations reproduce linear wave frequencies despite broad spectra. These finite mean frequencies proportional to poloidal wavenumber imply the existence of nonlinear wave resonances. Since one wave in the resonance is in the energydominant wavenumbers, the resonance is a nonlocal threewave interaction, which may relay the linear wave properties of the low wavenumbers up to the large wavenumbers. This richness in the spectra will be presented in terms of the parameters of $\alpha$ and diamagnetic drift and the threewave coupling analysis will be applied. [Preview Abstract] 

GP8.00035: Study of symmetry breaking induced stochasticity in magnetic field surfaces with the 3DMaptor code Julio HerreraVel\'azquez, Esteban Ch\'avezAlarc\'on To a certain extent, the success in designing a magnetic confinement device, rests in the capacity of producing a configuration, such that there is a symmetry which allows the existence of closed and sturdy magnetic field surfaces. If such symmetry is broken, either by instabilities in the plasma, or by engineering defects in the design and construction of the system, the surfaces break up, leading to the loss of confinement. A simple approach is to study this problem, is by using discrete area preserving maps, but at the cost of missing some of the physics issues. As an alternative, a 3D code has been developed in order to simulate the magnetic field lines, starting from the currents involved. A simple way to break the symmetry is by including tilted coils either on the inboard or outboard sides. Using this approach, different configurations are studied in this work, leading to stochastization of the the magnetic field surfaces. [Preview Abstract] 

GP8.00036: Creation of second order magnetic barrier inside chaos created by NTMs in the ASDEX UG Halima Ali, Alkesh Punjabi Understanding and stabilization of neoclassical tearing modes (NTM) in tokamaks is an important problem. For low temperature plasmas, tearing modes are believed to be mainly driven by current density gradient. For collisionless plasmas, even when plasma is stable to classical tearing modes, helical reduction in bootstrap current in Opoint of an island can destabilize NTMs when an initial island is seeded by other global MHD instabilities or when microturbulence triggers the transition from a linear to nonlinear instability. The onset of NTMs leads to the most serious beta limit in ASDEX UG tokamak [O. Gubner et al 2005 NF \textbf{39 }1321]. The important NTMs in the ASDDEX UG are (m,n)=(3,2)+(4,3)+(1,1). Realistic parameterization of these NTMs and the safety factor in ASDEX UG are given in [O. Dumbrajs et al 2005 POP \textbf{12} 1107004]. We use a symplectic map in magnetic coordinates for the ASDEX UG to integrate field lines in presence of the NTMs. We add a second order control term [H. Ali and A. Punjabi 2007 PPCF \textbf{49} 1565] to this ASDEX UG field line Hamiltonian to create an invariant magnetic surface inside the chaos generated by the NTMs. The relative strength, robustness, and resilience of this barrier are studied to ascertain the most desirable noble barrier in the ASDEX UG with NTMs. We present preliminary results of this work, and discuss its implications with regard to magnetic transport barriers for increasing strength of magnetic perturbations. This work is supported by the grants DEFG0201ER54624 and DEFG0204ER54793. [Preview Abstract] 

GP8.00037: Chaotic Transport in nonmonotonic Zonal Flows with Finite Larmor Radius Effects Julio Martinell, Diego delCastilloNegrete The properties of chaotic transport is studied for a test particle in a nonmonotonic zonal flow including Finite Larmor radius (FLR) effects. Using Hamiltonian dynamical systems and a twomode drift wave model, the EXB Hamiltonian is averaged over the gyroradius and analyzed with Poincare plots. It is found that chaotic transport produced by the large amplitude modes is suppressed at the position of the shearless curve, as the FLR increases, reforming a transport barrier. The threshold for the destruction of the barrier is obtained, being of a fractal nature as function of the FLR and wave amplitude. The fraction of particles affected by the barrier in a thermal distribution is determined. For the transport along the flow the process is superdiffusive and thus it is nonlocal, but it is weakly dependent on the FLR. [Preview Abstract] 

GP8.00038: Flow topology, Lagrangian statistics, and transport in resistive driftwave turbulence B. Kadoch, Diego delCastilloNegrete, W.J.T Bos, K. Schneider Transport is strongly influenced by coherent structures. In particular, trapping in vortices tends to arrest transport and zonal flows can induce large Lagrangian displacements. It is thus of interest to characterize coherent structures from a Lagrangian perspective. For 2D flows, the {\em Eulerian} Weiss criterion provides a tool to partition the flow into topologically different regions: elliptic (vortex dominated), hyperbolic (deformation dominated), and intermediate (turbulent background). In Ref.\footnote{B. Kadoch, D. delCastilloNegrete, W.J.T Bos, and K. Schneider, Phys. Rev. E 83, 036314 (2011).} we proposed the {\em Lagrangian} Weiss criterion (i.e. the Weiss field computed along particle orbits) and applied it to 2D NavierStokes turbulence. Here we apply this criterion to resistive driftwave turbulence. The probability density functions (pdfs) of residence time in the topologically different regions are computed for ensembles of Lagrangian tracers. It is shown that in elliptic and hyperbolic regions the pdfs have algebraically decaying tails. The pdf of residence time in elliptic regions is proposed as a measure of particle trapping, and the relationship with waiting time statistics in continuous time random walk models of anomalous transport is explored. [Preview Abstract] 

GP8.00039: Transport properties and radiation production in plasmas with subLArmorscale magnetic turbulence B. Keenan, M.V. Medvedev Kinetic streaming instabilities, such as the Weibel instability, occur in various plasma setups. It has earlier been proposed that radiation emitted by relativistic electrons, called jitter radiation, during the field generation and its subsequent selfsimilar evolution and selforganization can deliver wealth of information about the internal structure of ``Weibel turbulence.'' The smallscale fields simultaneously affect the particle transport via pitchangle diffusion and the radiation production and its spectra. Both effects are related and can be used to diagnose the plasma state. Indeed, the radiation pattern is intimately related to the particle orbits and, thus, to the transport properties of the turbulence. We study such a relation between transport and radiation in subLarmorscale turbulence numerical simulations and analysis. We discuss how our results will improve the radiative diagnostic technique of lab and astro HED plasmas. [Preview Abstract] 

GP8.00040: Nonlinear Interchange Modes in 3D Jupiter Bagaipo, Adil Hassam We have shown previously that, in 2D, the ideal magnetohydrodynamic interchange mode stabilized by a constant transverse magnetic field is nonlinearly unstable if near marginal conditions. This study is extended to a 3D system where the mode is marginally stabilized by allowing for wavenumbers weakly transverse to an axial field. Two different boundary conditions are studied: periodic and linetied in the axial direction. Periodic boundary conditions have applications in toroidal fusion devices while linetied systems are common in the solar corona. We use reduced equations for a strong axial field to find an analytic solution as a function of the deviation from marginality. Using a systematic perturbation analysis we show that, to lowest order, there exists a secondary, quasistatic equilibrium with a critical field strength. Allowing for deviations from criticality yield a nonlinear timeevolution equation for the perturbation amplitude. The periodic case allows for two types of modes, and it is shown that the mode isomorphic to the earlier 2D problem is nonlinearly unstable, while the ``sausage''type mode is nonlinearly stable. These modes are modes along a rational surface and ballooning type modes, respectively. The linetied case is shown to always be nonlinearly stable. [Preview Abstract] 

GP8.00041: LABORATORY PLASMA ASTROPHYSICS II AND SHOCKS 

GP8.00042: Magnetized collisionless shock studies using high velocity plasmoids Thomas Weber, Thomas Intrator, Kevin Gao Magnetized collisionless shocks are ubiquitous throughout the cosmos and are observed to accelerate particles to relativistic velocities, amplify magnetic fields, transport energy, and create nonthermal distributions. They exhibit transitional scale lengths much shorter than the collisional mean free path and are mediated by collective interactions rather than Coulomb collisions. The Magnetized Shock Experiment (MSX) leverages advances in Field Reversed Configuration (FRC) plasmoid formation and acceleration to produce highly supersonic and superAlfv\`{e}nic supercritical shocks with preexisting magnetic field at perpendicular, parallel or oblique angles to the direction of propagation. Adjustable shock speed, density, and magnetic field provide unique access to a range of parameter space relevant to a variety of naturally occurring shocks. This effort examines experimentally, analytically, and numerically the physics of collisionless shock formation, structure, and kinetic effects in a laboratory setting and draw comparisons between experimental data and astronomical observations. Approved for Public Release: LAUR1222886 [Preview Abstract] 

GP8.00043: Laboratory experiment to investigate collisionless shock production and dynamics A.L. Moser, S.C. Hsu, J.P. Dunn, D.T. Martens, C.S. Adams, E.C. Merritt, A.G. Lynn, M.A. Gilmore, C. Thoma, D.R. Welch Many shock waves in astrophysical systems are collisionless: the system scale is smaller than the collision meanfreepath, and plasma effects provide the required dissipation. Laboratory measurements of collisionless shocks would provide the spatial and temporal resolution not provided by current space measurements, providing insight into shock formation, dynamics, and shockparticle interactions. An experiment at LANL aims to produce $\sim $1cmthick, $\sim $3050cmdiameter collisionless shocks via headon collision of two railgunproduced hydrogen plasma jets. Jets with initial temperatures of a few eV, densities of $\sim $10$^{15}$ cm$^{3}$, and velocities of $\sim $100 km/s will propagate $\sim $1.1 m before colliding; PIC simulations predict shocklike behavior at planned jet parameters. Identification and characterization of collisionless shocks requires measurement of several plasma parameters both up and downstream of the shock. Interferometer and spectrometer measurements giving plasma density, temperature, and velocity will be augmented with a Schlieren imaging system and electrostatic probes; Bdot probes will provide magnetic field data. The ability of collisionless shocks to accelerate particles to superthermal velocities will be investigated with ion energy analyzers. We present here an overview of the experiment, including preliminary data. [Preview Abstract] 

GP8.00044: Numerical Simulations of Collisionless Shock Formation in Merging Plasma Jet Experiments Carsten Thoma, Dale Welch, Robert Clark, Scott Hsu In upcoming experiments at the Plasma Liner Experiment (PLX) facility at Los Alamos National Laboratory, two high Mach number plasma jets, composed of gases such as H and Ar, will be collided. We describe numerical simulations using particleincell (PIC) and hybridPIC methods using the code Lsp. Using expected experimental plasma conditions ($n \sim 10^{14}10^{17}$ cm$^{3}$), large scale transport simulations demonstrate that the jets are essentially collisionless at the merge point. In smallerscale 1D and 2D simulations we show that collisionless shocks are generated by the merging jets when immersed in applied magnetic fields ($B \sim 0.11$ T). Unmagnetized collisionless shocks are not found in simulations at the expected jet velocities ($\sim 10100$ km/s). Considerably higher velocities are required to see this effect. The orientation of the magnetic fields and the axial and transverse gradients of the jets are shown to have a strong effect on the nature of the interaction. [Preview Abstract] 

GP8.00045: Schlieren Imaging Diagnostic for a Collisionless Shock Experiment C.S. Adams, A.G. Lynn, M.A. Gilmore, E.C. Merritt, A.L. Moser, S.C. Hsu A schlieren imaging diagnostic has been designed and constructed to diagnose the properties of astrophysicallyrelevant collisionless shocks in colliding plasma jets. This system has been designed to capture electron density changes as small as 10\% over millimeter length scales in $\sim 1$10~eV hydrogen plasmas at $10^{14}$~cm$^{3}$ density. The diagnostic consists of a 1.064~$\mu$m Nd:YAG illumination system and a megapixel imaging camera. The layout is a Zconfiguration for compactness, with 20~cm diameter mirrors to enable a relatively wide imaging area. We present preliminary results from oblique and headon jet merging experiments at densities in the $10^{14}$ to $10^{17}$~cm$^{3}$ range. [Preview Abstract] 

GP8.00046: A platform to study magnetic field amplification of laser driven shocks due to induced turbulence Jena Meinecke, Hugo Doyle, A.R. Bell, Robert Crowston, Paul Drake, M. Fatenejad, Nick Hartley, Michel Koenig, Y. Kuramitsu, Carolyn Kuranz, Don Lamb, Mike MacDonald, F. Miniati, Chris Murphy, Alex Pelka, Alessandra Ravasio, Brian Reville, Y. Sakawa, A.A. Schekochihin, Anthony Scopatz, Petros Tzeferacos, Wesley Wan, Nigel Woolsey, Gianluca Gregori Misaligned pressure and temperature gradients associated with asymmetrical shock waves generate currents which seed magnetic fields (Biermann battery process). These fields could then be further amplified by increasing particle gyration driven by vorticity and turbulence. Studies of such phenomena have been conducted at the Rutherford Appleton Laboratory and scaled to astrophysical conditions (e.g., protogalacitc structure formation) using magnetohydrodynamic scaling techniques. Shock waves were driven in a 1 mbar Argon gas filled chamber from ablation of 500 micron Carbon rods using 300 J of 527 nm, 1 ns pulse light. A plastic grid was positioned 1 cm from the target to drive turbulence with outer scale $\sim $1 mm (the size of the grid opening). An induction coil, located 2 cm from the grid, was used to measure the magnetic field while optical diagnostics were used to track the fluid flow. Preliminary results and comparisons with hydrodynamic codes will be shown. [Preview Abstract] 

GP8.00047: Comparison of Laboratory and 2D Hybrid Simulations of LaserDriven Magnetic Pistons Relevant to Magnetized Collisionless Shocks E.T. Everson, D.B. Schaeffer, D. Winske, M. Lauter, G. Rennenkampff, S.E. Clark, A.S. Bondarenko, C.G. Constantin, C. Niemann Experiments performed at the University of California at Los Angeles (UCLA) utilized the Large Plasma Device (LAPD) and the Phoenix Laser to drive sub and superAlfv\'{e}nic laserplasma explosions through the uniform, magnetized background plasma of the LAPD. The $30$ J, $5$ ns FWHM Phoenix laser ablated a graphite target to produce a debrisplasma that is allowed to expand ($>50$ cm) across and shock the lowdensity ($15\times10^{12}$ cm$^{3}$), magnetized ($275600$ G) Helium (or Hydrogen) plasma of the LAPD. Magnetic flux probe measurements of the cross field expansion are compared to 2D hybrid simulations to provide insight on the decoupling between the fast debrisions and diamagnetic bubble, the coupling between the slower debrisions and ambientions, and the magnetic piston. [Preview Abstract] 

GP8.00048: Characterization of LaserAblated, Magnetized Carbon Plasmas Relevant to Magnetized Collisionless Shocks D.B. Schaeffer, A.S. Bondarenko, E.T. Everson, E.S. Clark, C.G. Constantin, C. Niemann, D. Winske We present experiments on laserablated, magnetized carbon plasmas performed at the University of California, Los Angeles (UCLA). A graphite target placed inside a static magnetic field ($\la 1$ kG) created by a $50$ cmdiameter Helmholtz coil was ablated by laser pulses at $1053$ nm with energies between $10100$ J. Magnetic flux probes measured the magnetic field compression and expulsion of the resulting blowoff plasma and diamagnetic bubble. A separate laser at $527$ nm was used for Thomson scattering to characterize the electron temperature and density up to several cm from the target and several microseconds after the initial laser ablation. The carbon ionization states and blowoff velocities were further measured with emission spectroscopy. The data was used to inform 2D hybrid simulations of a laserablated plasma expanding into an ambient plasma, relevant to upcoming magnetized collisionless shock experiments on the Large Plasma Device at UCLA. [Preview Abstract] 

GP8.00049: Magnetic Field Measurements in low Density Plasmas using Paramagnetic Faraday Rotator Glass Stephen Clark, Derek Schaeffer, Erik Everson, Anton Bondarenko, Carmen Constantin, Christoph Niemann, Dan Winske Paramagnetic Faraday rotator glass (rareearth doped borosilicate) with a high Verdet constant will be used to measure the magnetic field inside of low density Helium plasmas ($T_e$ $\sim$ 5 eV, $T_i$ $\sim$ 1 eV) with a density of n $\sim$ $10^{12}$~cm$^{3}$. Linearly polarized light is sent through the glass such that the plane of polarization is rotated by an angle that depends on the strength of the magnetic field in the direction of propagation and the length of the crystal (6~mm). The light is then passed into an analyzer and photodetector setup to determine the change in polarization angle. This setup can detect magnetic fields up to 5 kG with a resolution of $<$ 5 G and a temporal resolution on the order of a nanosecond. The diagnostic will be used to characterize the structure and evolution of laserdriven collisionless shocks in large magnetized plasmas. [Preview Abstract] 

GP8.00050: Spectroscopic Study of LaserAblated Carbon Plasmas Anton Bondarenko, Derek Schaeffer, Erik Everson, Carmen Constantin, Eric Clark, Chris Niemann Exploding, energetic plasmas produced by laser ablation of solid targets have been extensively utilized in the field of laboratory astrophysics. In particular, superAlfv{\'e}nic plasma expansions into magnetized background plasmas are vital for laboratory investigations of collisionless shocks, diamagnetic cavity formation, and ion coupling in astrophysical environments. In ongoing experiments at the Phoenix laser facility at UCLA, emission spectroscopy has been utilized in order to better characterize expanding carbon plasmas generated via intense laser ($200$$600$ GW/cm$^2$) ablation of graphite targets. The ablation plasmas are generated in vacuum, with and without the presence of a uniform external magnetic field ($\sim800$ G). A detailed spectroscopic survey in the $200$$600$ nm range has been conducted in order to identify the various carbon ionization stages present within the plasma, and the Doppler widths and shifts of several spectral lines have been measured in order to determine velocity distributions of the corresponding ions. The temporal evolution and 1D spatial distribution of spectral line intensities have also been analyzed in order to generate a qualitative visualization of the carbon plasma expansion. [Preview Abstract] 

GP8.00051: Magnetized, radiative shocks in aluminum plasma flows John Greenly, Charles Seyler, Xuan Zhao Arrays of aluminum wires driven by the 1 MA, 200 ns COBRA generator are used to produce uniform sheet flows of several cm scale size, consisting of multiply ionized aluminum plasma with velocity up to 400 km/s, density $\sim $10$^{18}$/cm$^3$ and variable magnetic field of several Tesla. Shocks are produced by obstacles placed in the flow. The shock structures radiate strongly in the XUV, as shown by imaging diagnostics. Laser shadowgraphy and interferometry are also used, and submm size magnetic probes are used to measure the fields associated with the shocks. Unstable shock structures are also observed at the leading edge of the flow when no physical obstacles are used; this structure is formed by the collision of the flow with the lowdensity cold background gas in the experimental chamber. The experimental results will be compared with simulations using the XMHD code PERSEUS, which shows characteristic magnetic signatures of these structures. [Preview Abstract] 

GP8.00052: Optical diagnostics in turbulent, laserdriven shockwave experiments with selfgenerated magnetic fields W.C. Wan, M.J. MacDonald, C.C. Kuranz, C.M. Krauland, E.J. Gamboa, C.A. Di Stefano, R.P. Drake The existence of magnetic fields on a cosmological scale is still poorly understood. Magnetic fields as large as a few $\mu$G have been observed in galaxy clusters, filaments, and voids. Recent experiments at the Vulcan and Titan laser facilities produced scaled models to investigate the generation and amplification of seed magnetic fields through induced turbulence. The study of magnetogenesis and amplification due to turbulence will contribute to our understanding of the dynamics of the early universe. These experiments were performed by focusing lasers on carbon rods and foils, resulting in a blast wave propagating through argon gas. Several grids with varied mesh spacing provided control over the level of turbulence. Here we discuss the results of the Schlieren and interferometry optical diagnostics obtained in these recent campaigns. This work was supported by many sponsors to be acknowledged in the presentation. [Preview Abstract] 

GP8.00053: Shock Waves in HallMHD George Hagstrom, Eliezer Hameiri We study shock waves and discontinuities in HallMHD. We characterize planar travelling wave solutions with discontinuities in the absence of viscosity. These solutions arise due to the presence of hydrodynamic characteristics in HallMHD. We demonstrate finitetime discontinuity formation for certain types of initial data with discontinuous derivatives. Using matched asymptotic expansions and introducing a small viscosity and heat conductivity, we calculate shock structures corresponding to the discontinuous travelling waves. When these structures exist the dynamical variables at each side of the inner region satisfy the RankineHugoniot conditions of the ionacoustic shock and also the entropy condition. We also explore the possible existence of solutions with discontinuous magnetic field. A nonalgebraic, nonlocal set of jump conditions is derived under the assumption of $[B]\neq0$. These conditions are used to study the contact discontinuity and it is shown that massless electrons crossing the surface of discontinuity may enter and leave at different locations. These conditions suggest the possible existence of mathematically novel shocks in HallMHD. [Preview Abstract] 

GP8.00054: Interaction of supersonic radiatively cooled plasma jet with solid targets L. Pickworth, S.V. Lebedev, F. SuzukiVidal, M. Bocchi, G. Swadling, S.N. Bland, G. Burdiak, J.P. Chittenden, P. de Grouchy, G.N. Hall, J. Skidmore, L. Suttle, M. Bennett, S. Patankar, A. Ciardi, A. Frank Results of experiments aimed on formation of reverse shocks in radiatively cooled supersonic plasma jets decelerated in collision with solid targets will be presented. The jet is produced by plasma flows in radial foil or wire array zpinch configurations driven by 1.4MA, 250ns current pulse on the MAGPIE Zpinch. The produced jet has internal Mach numbers of 320, Reynolds numbers of $>$10$^{5}$ and density of $\sim $10$^{18}$10$^{19}$cm$^{3}$. The interaction of the jet with a foil target produces several shock features which were investigated using laser imaging and interferometry at 532nm and 355nm, spectroscopy and Thompson scattering diagnostics, providing specially resolved measurements of the flow velocity and plasma temperature in the shock front. [Preview Abstract] 

GP8.00055: Shock formation from the interaction of supersonic, radiatively cooled plasma flows with neutral gases F. SuzukiVidal, S.V. Lebedev, J. Skidmore, G.F. Swadling, L.A. Pickworth, G. Burdiak, M. Bocchi, S. Patankar, M. Bennett, S.N. Bland, J.P. Chittenden, P. de Grouchy, G.N. Hall, E. Khoory, S.J.P. Stafford, L. Suttle, R.A. Smith, A.J. HarveyThompson, A. Frank, E. Hansen, M. Krishnan, R. Madden, K. WilsonElliott, P.L. Coleman, A. Ciardi The dynamics of the interaction of supersonic, radiatively cooled plasma flows with applications to laboratory astrophysics are under study on the MAGPIE generator. One of such astrophysicalrelevant experiments is the ablated plasma from a radial foil, with typical flow velocities reaching $\sim $100 km/s. The effect of the ambient medium is studied by adding neutral gases, either using a supersonic gasnozzle or by enclosing the foil inside a gascell. In both cases, the dynamics of the interaction are characterized by the formation of several shock features. Experimental results varying ambient parameters such as gas pressure and gas composition (e.g. He, Ar, Xe) will be presented together with 3D MHD simulations using the code GORGON. [Preview Abstract] 

GP8.00056: HED jetambient interaction studies in the lab Philip de Grouchy, Sergey Lebedev, Matthew Bennett, Guy Burdiak, Simon Bland, Gareth Hall, Lee Suttle, George Swadling, Francisco SuzukiVidal, Matteo Bocchi, Jeremy Chittenden, Sheng Liang The formation and evolution of shock structures and density nonuniformities along the jets from young stellar objects [1] provides insight into the basic fluid dynamics of collimated, radiatively cooled supersonic flows. Pulsed power driven jets (conical /radial wire arrays; radial foils [2,3]) have appropriate dimensionless parameters (Mach number; Reynolds number; cooling parameter) to simulate aspects of this class of astrophysical jets under controlled conditions. In our previous experiments gas cloud [4] and ablation of a plastic target [5] provided an ambient medium for jet interaction/deflection studies. Recent work has shown that hydrodynamic jets from conical arrays can be injected into the precursor plasma of cylindrical wire array mounted in series above it, and that diagnostic access remains open. In this paper we present our latest results illustrating the formation of shock structures in the target region, density distribution across the interaction and the influence of jet material on the flow dynamics.\\[4pt] [1] Hartigan et al. 2011, ApJ, 736, 29\\[0pt] [2] Lebedev et al. 2002, ApJ, 564, 113119\\[0pt] [3] Ciardi et al. 2009, ApJ, 691, L147L150\\[0pt] [4] SuzukiVidal et al. 2012, PoP, accepted\\[0pt] [5] Lebedev et al. 2004, ApJ, 616, 988997 [Preview Abstract] 

GP8.00057: Destruction of a Magnetic MirrorTrapped Hot Electron Ring by an Alfv\'{e}n Wave Yuhou Wang, Walter Gekelman, Patrick Pribyl, Konstantinos Papadopoulos Highly energetic electrons produced naturally or artificially can be trapped in the earth's radiation belts for months, posing a danger to valuable space satellites. Concepts that can lead to mitigation of the radiation belts have drawn a great deal of interest. In this work, we demonstrated that a shear Alfv\'{e}n wave can effectively detrap energetic electrons confined by a magnetic mirror field.\footnote{Y. Wang, W. Gekelman, P. Pribyl, and K. Papadopoulos, Phys. Rev. Lett. 108, 105002 (2012).} The experiment is performed in a quiescent afterglow plasma in the Large Plasma Device (LaPD) at UCLA ($n_e =0.11\times 10^{12}/cm^3$, $T_e =0.5eV$, $B_0 =4001600G$, $L=18m$, and $diameter=0.6m)$. A hot electron ring (along with hard xrays of energies up to 3 MeV) is generated by 2nd harmonic ECRH ($P=25kW$, $\tau _{pulse} =2050ms$, $f=2.45GHz)$ and is trapped in a magnetic mirror field ($L=3m$, $R_{mirror} =1.14)$. A shear Alfv\'{e}n wave ($f\approx 0.5f_{ci} $, $B_{wave} /B_0 \approx 0.1\% )$ is launched with a rotating magnetic field antenna with arbitrary polarity. The circularly polarized Alfv\'{e}n wave is observed to dramatically scatter the trapped fast electrons out of the mirror within as little as 10 wave cycles. A collimated detector outside the vacuum vessel detects Xrays of E$>$100 keV. Xray images are reconstructed from more than 1000 chord projections at each axial location by computed tomography. The detrapped electrons are observed outside the mirror field region. [Preview Abstract] 

GP8.00058: Magnetic field advection in two interpenetrating plasma jets D.D. Ryutov, N.L. Kugland, M.C. Levy, C. Plechaty, J.S. Ross, H.S. Park Two lasergenerated colliding jets can serve as a testbed for the study of various astrophysical phenomena [1] and the general physics of selforganization [2]. For jets of a sufficiently high energy, collisions of the ions of one jet with the ions of the other jet are negligible, and the jets can penetrate through each other [1, 3]. On the other hand, the intrajet collisions for highMachnumber jets can be very frequent, so that each jet can be described by hydrodynamic equations [4]. We present an analytical study of the effects of this flow on largescale magnetic fields either imposed by external sources or generated near the laser targets. Specifically, we consider an issue of the line tying (``Which jet is the magnetic field frozen into?''), possible stretching of the field by a shear flow, and the potential effect of hydrodynamic instabilities on the magnetic field. Work performed for U.S. DoE by LLNL under Contract DEAC5207NA27344.\\[4pt] [1] H. S. Park et al, HEDP, 8, 38 (2011).\\[0pt] [2] N.L. Kugland et al, submitted to NaturePhysics (2012).\\[0pt] [3] J.S. Ross et al, Phys. Plas., 19, 056501 (2012).\\[0pt] [4] D.D. Ryutov et al, Phys. Plas., 19, 074501 (2012). [Preview Abstract] 

GP8.00059: Background density channel generation by axial plasma jets Jeffrey Bonde, Stephen Vincena, Walter Gekelman The supersonic expansion of a dense plasma into an ambient plasma can be observed in phenomena ranging from coronal mass ejections and protostellar outflows to astrophysical jets. To produce a supersonic plasma jet in a laboratory setting, a laserproduced plasma explodes into an ambient argon plasma ($n\sim5\cdot10^{12}cm^{3}$,$c_{s}\sim6\cdot10^{5}cm/s$,$v_{A}\sim1.2\cdot10^{7}cm/s$) in the Large Plasma Device at UCLA. This study focuses on the initial formation and evolution of the jet and its effects on the background magnetized plasma. Using a laserinduced fluorescence diagnostic of ArII ions at their 611.5nm transition, the jet is seen to perturb the equilibrium population of the target argon ions. A CCD camera with a fast ($\geq3$ns) shutter spatially and temporally resolves images of the fluorescence. Timelapsed imaging shows an axially aligned channel of depleted fluorescence form near the source and travel with an undiminished speed characteristic of the jet ($v/c_{s}\sim20$) while remaining highly collimated. Langmuir probe measurements show a large ion flux moving in conjunction with the excited argon depletion after traveling more than an ion inertial length. [Preview Abstract] 

GP8.00060: The Eagle Nebula Science on NIF experiment Jave Kane, Robert Heeter, David Martinez, Marc Pound, Bruce Remington, Dmitri Ryutov, Vladimir Smalyuk The Eagle Nebula NIF experiment was one of nine selected for laser time through the Science on NIF program. The goal of this scale laboratory experiment is to study the dynamic evolution of distinctive structures in star forming regions of astrophysical molecular clouds such as the Pillars of the Eagle Nebula. That evolution is driven by photoionizing radiation from nearby stars. A critical aspect of the radiation is its very directional nature at the photoionization front. The long duration of the drive and its directionality can generate new classes of instabilities and dynamic flows at the front that may be responsible for the shapes of Pillars and other structures. The experiment will leverage and modify the existing NIF Radiation Transport platform, replacing the target at the back end of the halfraum with a collimating aperture, and extending the existing 20 ns drive to longer times, using a combination of gas fill and other new design features. The apertured, quasicollimated drive will be used to drive a target placed 2 mm away from the aperture. The astrophysical background and the status of the experimental design will be presented. [Preview Abstract] 

GP8.00061: FLASH Magnetohydrodynamic Simulations of Experiments to Explore the Generation of Cosmological Magnetic Fields Petros Tzeferacos, Milad Fatenejad, Norbert Flocke, Gianluca Gregori, Donald Q. Lamb, Dongwook Lee, Jena Meinecke, Anthony Scopatz, Klaus Weide Magnetic fields are ubiquitous throughout the universe. However, the origin and strength of these fields are not fully understood. A promising mechanism for the origin of seed fields is the asymmetric shocks that occur in hierarchical structure formation when smaller halos merge to form galaxies and galaxies merge to form clusters of galaxies. The seed fields are generated by the Biermann battery mechanism. The COSMOLAB team of the University of Oxford is conducting experiments to investigate the generation of magnetic fields by asymmetric shocks. These experiments involve the laser illumination of a foil target, driving a shock into a gasfilled chamber, and a variety of plasma and magnetic field diagnostics. In this paper, we describe magnetohydrodynamic simulations of the experiment carried out using the FLASH code. The scientific objective of these simulations is to explore the morphology and strength of the magnetic fields generated by ablation of target material by the laser, and by the jetlike shock that is produced on the opposite side of the target. [Preview Abstract] 

GP8.00062: The development of space plasma testing facility using RF source Richard Kamieneski, Alexander Hyde, Oleg Batishchev A new testing facility is being developed to simulate space and atmospheric plasmas. It utilizes modified helicon plasma source [1] to ionize gases common to space and ionosphere, namely hydrogen, helium, and nitrogen. Emission spectra of ionized gases are analyzed by vacuum spectrometer to understand plasma composition. The design of computerized controls and data acquisition system are discussed. \\[4pt] [1] O. Batishchev, Minihelicon Plasma Thruster, IEEE Trans. Plasma Science, 37 (8) 1563, 2009. [Preview Abstract] 

GP8.00063: MAGNETOINERTIAL FUSION 

GP8.00064: Summary of Plasma Liner Experiment (PLX) Research Results S.C. Hsu, A.L. Moser, J.S. Davis, J.P. Dunn, T.J. Awe, E.C. Merritt, C.S. Adams, A.G. Lynn, M.A. Gilmore, S. Brockington, A. Case, S.J. Messer, D. van Doren, F.D. Witherspoon, J.T. Cassibry, M. Stanic Spherically imploding plasma liners could result in cm, $\mu$s, and Mbarscale plasmas upon stagnation, which is of interest for fundamental high energy density (HED) plasma physics studies. They are also envisioned as a potential standoff compression driver for magnetoinertial fusion (MIF)\@. Experiments on PLX over the past year have focused on characterizing the propagation of a single argon plasma jet and the oblique merging of two jets, and assessing the suitability of the jets for the HED and MIF applications. Via a multichord interferometer, survey spectrometer, photodiode array, and fast framing imaging camera, we are determining that the jets are near the PLX design goal with respect to density ($10^{17}$~cm$^{3}$) and velocity (50~km/s). The key physics issues being studied are the rate of jet expansion during propagation, and the potentially deleterious effects of jet merging such as shock formation and heating which could degrade imploding liner performance. This poster will provide a project summary, and a highlight of experimental results on both sin [Preview Abstract] 

GP8.00065: Merging of High Speed Argon Plasma Jets Andrew Case, Sarah Messer, Sam Brockington, LinChun Wu, F. Douglas Witherspoon Formation of an imploding plasma liner for the Plasma Liner Experiment (PLX) requires individual plasma jets to merge into a uniform shell of plasma converging on the target region. Understanding dynamics of the merging process requires knowledge of the plasma phenomena involved. We present here results from the study of the merging of six plasma jets in three dimensional geometry. The experiments were performed using HyperV Technologies Corp. one centimeter MiniRailguns using a preionized Argon plasma armature on a vacuum chamber designed to partially reproduce the port geometry of the PLX vacuum chamber. Diagnostics include fast imaging, spectroscopy, interferometry, fast pressure probes, Bdot probes, and high speed spatially resolved photodiodes, permitting measurements of plasma density, temperature, velocity, stagnation pressure, and magnetic field. These experimental results are compared with simulation results from the LSP 3D hybrid PIC code. [Preview Abstract] 

GP8.00066: The HyperV 8000 $\mu g$, 50 km/s Plasma Railgun for PLX Samuel Brockington, Andrew Case, Sarah Messer, Linchun Wu, F. Douglas Witherspoon HyperV has developed a gas fed, pulsed, plasma railgun which accelerates 8000 $\mu g$ of argon to 50 km/s meeting the performance requirements originally specified for the Plasma Liner Experiment (PLX). The present 2.5 cm squarebore plasma railgun forms plasma armatures from high density neutral gas, preionizes it electrothermally, and accelerates the armature with 30 cm long parallelplate railgun electrodes driven by a pulse forming network (PFN). A high voltage, high current linear array sparkgap switch and flexible, lowinductance transmission line were designed and constructed to handle the increased current load. We will describe these systems and present initial performance data from high current operation of the plasma rail gun from spectroscopy, interferometry, and imaging systems. Measurements of momentum, pressure, magnetic field, and other optical diagnostics will also be discussed as well as plans for upcoming experimentation to increase performance even further. Work supported by USDOE under DEFG0205ER54810 and DEFG0208ER85114. [Preview Abstract] 

GP8.00067: Technology applications for Magneto Inertial Fusion T. Intrator, T. Weber, K. Gao, C. Yoo, J. Klarenbeek We describe several technology advances that we believe will be helpful for Magneto Inertial Fusion (MIF) experiments. We are developing plasma guns to improve the startup and flux trapping for magnetized plasma field reversed configuration (FRC) targets for MIF compression. This should aid initial pre ionization, freezing in of bias flux, line tie each end to the middle to retard toroidal rotation, and provide end shorting of radial electric fields. We are also developing a novel magnetic field diagnostic that uses a tiny section of Terbium doped optical fiber as a Faraday rotation medium. The optical path and hardware is inexpensive and simple, and has a small form factor that will fit inside a MagLIF capsule, and can be radation hardened. Low noise, optically coupled magnetic field measurements will be possible for vacuum MaGLIF shots. [Preview Abstract] 

GP8.00068: Pulsed polarimetry first results on the LANL MSX magnetized shock experiment R.J. Smith, P.R. Andrist, T.P. Intrator, T. Weber Pulsed polarimetry, a Lidarlike technique, promises to provide internal measurements of the distributions of ne, B and Te for Magnetized High Energy Density (MHEDLP) targets. The instrument in its final form is finished and presently being employed on the LANL MSX magnetized shock experiment as a first use. Snap shot temperature and density profile measurements with subcm resolution are possible along arbitrary sightlines through the plasma. Initial measurements of plasma parameters characterizing plasma operations as measured by the pulsed polarimeter will be presented. [Preview Abstract] 

GP8.00069: Development of FieldReversed Configuration Plasma Gun Formation Techniques for Magnetized Target Fusion Alan Lynn, Mark Gilmore, Tyler Wynkoop, Thomas Intrator, Thomas Weber Magnetized Target Fusion (MTF) is an innovative approach for a relatively fast and cheap path to the production of fusion energy that utilizes magnetic confinement to assist in the compression of a hot plasma to thermonuclear conditions by an external driver. Los Alamos National Laboratory (LANL) is currently pursing demonstration of the MTF concept via compression of an FRC (fieldreversed configuration) plasma by a metal liner zpinch in conjunction with the Air Force Research Laboratory in Albuquerque, NM. A key physics issue for the FRC as an MTF target lies in the initial preionization (PI) stage. The PI formation process determines the amount of magnetic flux that can be trapped to form the FRC. This trapped flux plays an important role in the FRC's final equilibrium, transport, and stability properties. It also provides the route to greatest potential gains in FRC lifetime, which is essential to provide enough time to translate and compress the FRC effectively. In conjunction with LANL we plan to test and characterize a new system to improve the initial PI plasma formation. This system will use an array of plasma guns to form the initial plasma. Initial characterization of the plasma gun behavior will be presented. [Preview Abstract] 

GP8.00070: ABSTRACT WITHDRAWN 

GP8.00071: Optimal Liner Material for Near Term Magnetized Liner Fusion Experiments Stephen Slutz Substantial fusion yields are predicted with existing pulsed power machines driving cylindrical liner implosions with preheated and magnetized deuteriumtritium [S.A. Slutz et al Phys. Plasmas 17, 056303 (2010)]. Experiments are planned using the Z accelerator to drive these implosions. However, the peak current, the laser heating energy, and the applied magnetic field will be less than optimal. We present simulations which show, that under these conditions, the yield can be improved significantly by decreasing the density of the liner material, e.g. Lithium substituted for Beryllium. Furthermore, the simulations show that decreasing the liner density allows the use of very low aspect ratio (R/$\Delta $R) liners, while still obtaining interesting yields. Low aspect ratio liners should be more robust to the RayleighTaylor instability. [Preview Abstract] 

GP8.00072: Code Verification of Magnetized Cylindrical Liner Implosions Mark Hess, Matthew Weis, Matthew Martin, Adam Sefkow, Charles Nakhleh, Y.Y. Lau We investigate the physics of magnetized cylindrical liner implosions with existing MHD codes to verify code accuracy, as well as to understand parametric behavior on figuresofmerit, e.g. radial liner velocity, for designing experiments. ~In our problem, we assume that there exists a 1D metallic cylindrical liner with an initial axial magnetic seed field imposed in the system. ~ The liner radially implodes due to a specified drive current while the effects of liner pressure and magnetic seed field compression oppose the implosion. This problem is of importance for future magnetized liner fusion experiments, e.g. MagLIF [1].\\[4pt]Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DEAC0494AL85000. \\[4pt] [1] S.A. Slutz et al, Phys. Plasmas 17, 056303 (2010). [Preview Abstract] 

GP8.00073: Experimental Platform for Magnetized HEDP Science at Omega P.Y. Chang, D.H. Barnak, M. Hohenberger, R. Betti, A. Agliata, W. Bittle, G. Fiksel, D. Hasset, D. Lonobile, M.J. Shoup III, C. Taylor Magnetized highenergydensity physics (HEDP) is an increasingly active research area with relevance to inertial confinement fusion (ICF), astrophysical sciences and basic plasma physics. A compact, selfcontained magneticfield generator MIFEDS (magnetoinertial fusion electrical discharge system) capable of providing a magnetic field up to 10 T was developed at the Laboratory for Laser Energetics and has been used at the Omega Laser Facility in recent experiments. The MIFEDS device has been upgraded to quadruple the stored energy and to double the magnetic field. In addition, the reliability of the device and the user interface has been improved. The device is now compatible with both OMEGA and OMEGA EP lasers and allows for fielding a wide variety of ICF, HEDP, and astrophysical experiments. Details of these new capabilities are provided and detail plans for experiments at Omega are shown. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DEFC5208NA28302. [Preview Abstract] 

GP8.00074: DIIID I, Edge Plasma, ELMs, Diagnostics 

GP8.00075: Sustained Suppression of TypeI Edge Localized Modes with Dominantly n=2 Magnetic Fields in DIIID M.J. Lanctot, M.E. Fenstermacher, I. Joseph, R.J. Buttery, M.R. Wade, T.E. Evans, N.M. Ferraro, J.S. deGrassie, P.B. Snyder, R. Nazikian, R.A. Moyer, D.M. Orlov, J.M. Hanson, W. Suttrop, S. Haskey TypeI edgelocalized modes (ELMs) are suppressed in DIIID using magnetic perturbations with dominant toroidal mode number $n=2$. ELM suppression is obtained with two rows of internal coils for 1.8 s with normalized beta of 1.9 and average triangularity of 0.53 corresponding to a scaled version of ITER scenario 2 at an ITER relevant electron collisionality of 0.2. The applied field reduces the pedestal density, pressure, and edge current without degrading the edge thermal transport barrier. ELITE calculations find the resulting profiles are stable to intermediaten peelingballooning modes. ELM suppression is demonstrated using different upper and lower phases enabling new investigations into the necessary conditions for suppression in terms of the resonant field amplitude and $q_{95}$. [Preview Abstract] 

GP8.00076: Singlerow versus doublerow RMP ELM suppression in \hbox{DIIID} J.S. deGrassie, T.E. Evans, P.B. Snyder, M.E. Fenstermacher, M.J. Lanctot, R.A. Moyer, D.M. Orlov, R. Nazikian, W.M. Solomon RMP ELM suppression in \hbox{DIIID} is consistent with the pedestal conditions being rendered stable to ELMs [1] by the application of resonant static magnetic perturbations. The detailed physical mechanism causing this pedestal relaxation is being pursued experimentally and theoretically. It is necessary to understand the relation between the RMP mode spectrum and attaining suppression in order to design efficient RMP coils for future devices. In \hbox{DIIID} ELM suppression conditions are being compared using the standard 2row evenparity set of \hbox{Icoils} and a single row of \hbox{Icoils}, with the latter having a broader monopolelike spectrum compared with the former. In particular, we have achieved suppression in the ITER baseline shape and $I/aB$ with a single row, a condition not yet achieved with 2row operation. We will discuss the possible differences in single and doublerow RMP suppression in relation to resonant and nonresonant components of the applied field. \vskip6pt\noindent [1] P.B. Snyder, et al., Nucl. Fusion {\bf 47}, 961 (2007). [Preview Abstract] 

GP8.00077: Comparison of Vacuum Model Predictions to Measurements in DIIID RMP Hmode Discharges D.M. Orlov, R.A. Moyer, D. Eldon, T.E. Evans, N.M. Ferraro, M.A. Van Zeeland, A. Wingen, M.W. Shafer, E.A. Unterberg, B.A. Grierson, R. Nazikian In this work we validate vacuum model predictions for the displacement of the separatrix due to applied resonant magnetic perturbations (RMPs) against experimental measurements. It is often assumed that plasma screening of RMP may be weak in the region of low rotation, high resistivity and high magnetic shear near the plasma separatrix and in the scrapeoff layer. Imaging beam emission spectroscopy (BES) shows radial displacement of the plasma boundary in the R,Z plane for $n=2$ and $n=3$ RMP experiments. Comparison of the vacuum field line tracing code (TRIP3DMAFOT) separatrix displacement calculations with the Thomson scattering and imaging BES measurements shows good agreement for $n=3$ discharges. However, separatrix displacements at the outer midplane in $n=2$ discharges is underestimated by the vacuum model, suggesting a nonresonant kink response that depends on the toroidal mode number. The vacuum code predictions of the homoclinic tangle formation are also found to be in good agreement with the SXR camera measurements in the vicinity of the divertor Xpoint and with passive imaging of CIII emission from the highfieldside of the plasma. [Preview Abstract] 

GP8.00078: Symplectic homoclinic tangles of the ideal separatrix of the DIIID from type I ELMs Alkesh Punjabi, Halima Ali The ideal separatrix of the divertor tokamaks is a degenerate manifold where both the stable and unstable manifolds coincide. Nonaxisymmetric magnetic perturbations remove the degeneracy; and split the separatrix manifold. This creates an extremely complex topological structure, called homoclinic tangles. The unstable manifold intersects the stable manifold and creates alternating inner and outer lobes at successive homoclinic points. The Hamiltonian system must preserve the symplectic topological invariance, and this controls the size and radial extent of the lobes. Very recently, lobes near the Xpoint have been experimentally observed in MAST [A. Kirk et al, PRL 108, 255003 (2012)]. We have used the DIIID map [A. Punjabi, NF \textbf{49}, 115020 (2009)] to calculate symplectic homoclinic tangles of the ideal separatrix of the DIIID from the type I ELMs represented by the peelingballooning modes ($m$,$n)$=(30,10)+(40,10). The DIIID map is symplectic, accurate, and is in natural canonical coordinates which are invertible to physical coordinates [A. Punjabi and H. Ali, POP \textbf{15}, 122502 (2008)]. To our knowledge, we are the first to symplectically calculate these tangles in physical space. Homoclinic tangles of separatrix can cause radial displacement of mobile passing electrons and create sheared radial electric fields and currents, resulting in radial flows, drifts, differential spinning, and reduction in turbulence, and other effects. This work is supported by the grants DEFG0201ER54624 and DEFG0204ER54793. [Preview Abstract] 

GP8.00079: Interpretative Modeling of RMP Effect on Edge Pedestal Transport T. Wilks, W.M. Stacey, J.P. Floyd, T.E. Evans Resonant magnetic perturbation (RMP) fields produced by 3D control coils are considered a viable option for the suppression of edge localized modes in future tokamaks, so an analysis of the diffusive and nondiffusive transport effects of these perturbations in the plasma edge has been performed. Repeated reversals of the toroidal phase of the Icoil magnetic field in RMP shot 147170 on DIIID has generated uniquely different edge profiles, implying different transport phenomena. The causes, trends, and implications of RMP toroidal phase change on transport are analyzed by comparing various parameters at $\phi =0$ and 60 degrees with an Icoil toroidal mode number of $n=3$. The change in the diffusive and nondiffusive transport in the edge pedestal for this RMP shot is characterized by interpreting the ion and electron heat diffusivities and the ion diffusion coefficient and pinch velocity in the edge pedestal region for both phases. [Preview Abstract] 

GP8.00080: Changes in Rotation and Rotational Shear by Resonant Magnetic Perturbations (RMPs) S. Mordijck, R.A. Moyer In order to understand the full impact of RMPs on peelingballooning stability we need to investigate not only the experimental changes in the pressure profile, but also in the edge rotation and rotational shear as a function of $q_{95}$. For $q_{95}$ values where edge localized modes (ELMs) are suppressed, there is strong reduction in the carbon toroidal rotational shear in the pedestal region as measured by the charge exchange recombination diagnostic. The changes in toroidal rotation are the main contributor to the changes in $E_r$ and $E\times B$ shearing rate. Suppression of ELMs by RMPs depends strongly on the value of $q_{95}$, whereas changes in the pressure profile only show a weak dependence. In contrast, the change in the $E\times B$ shearing rate is much more pronounced than the small changes in pressure profile and could play an important role in suppressing ELMs. [Preview Abstract] 

GP8.00081: Soft XRay Imaging of the DIIID Xpoint Region for Measurements of Magnetic Topology During 3D Magnetic Perturbations E.A. Unterberg, M.W. Shafer, A. Wingren, J.H. Harris, D.L. Hillis, R. Maingi, T.E. Evans, N. Ferraro A tangential 2D soft xray imaging system is installed on DIIID to directly measure the 3D magnetic topological structure around the Xpoint region where there is high poloidal flux expansion. Measurements of this structure are desired to aid in the understanding of the plasma response by comparisons with model analysis during the application of resonant magnetic perturbations. The diagnostic can be tailored to measure either in the ultrasoft xray (USXR) or soft xray (SXR) spectral range with different energy filters. Data contrast is enhanced by framesubtraction methods, spatial and temporal filtering, and impurity puffing. Data in the USXR energy band shows good agreement with vacuum modeling of the perturbed separatrix, while data in the SXR range has measured 3D magnetic structure inside the separtatrix, seen for the first time. Results from 3D image inversions are shown and compared with vacuum and plasma response models. [Preview Abstract] 

GP8.00082: Effect of Resonant Magnetic Perturbations on the Field Line Pitch Angle in the Pedestal of DIIID H. Stoschus, D.M. Thomas, T.E. Evans, B. Hudson Measurements of the field line pitch in the Hmode pedestal using the lithium beam (LIBEAM) diagnostic on DIIID are presented. The LIBEAM diagnostic has been brought back into operation to measure the poloidal magnetic field by means of polarimetry on the Zeeman split lithium emission lines with high temporal ($\approx$20 ms) and spatial (5 mm) resolution. Hardware upgrades and a new analysis technique based on fast Fourier transformation are presented. First measurements confirm the equilibrium variation of the field line pitch expected from EFIT. Application of the external Resonant Magnetic Perturbations (RMPs) results in a modification of the pitch angle, which increases nonlinearly with the RMP strength. Pitch angle profiles are compared to the electron density and pressure evolution measured with the lithium beam and Thomson scattering diagnostics. [Preview Abstract] 

GP8.00083: Influence of Plasma Response on Synthetic Soft \hbox{Xray} Image for DIIID A. Wingen, E.A. Unterberg, M.W. Shafer, N.M. Ferraro, T.E. Evans A synthetic soft xray diagnostic is applied to DIIID plasmas to model experimental measurements of soft xray emissions from the lower Xpoint and divertor region during applied resonant magnetic perturbations (RMPs). The synthetic soft xray diagnostic takes into account the modeled magnetic topology in DIIID using the full soft xray emission spectra. A first approach to the magnetic topology is the vacuum approximation, which consists of an EFIT equilibrium reconstruction and the perturbation fields of the external coil systems. In Hmode plasmas the plasma response to externally applied RMPs is believed to strongly alter the magnetic structures as compared to the vacuum approximation. To take into account this selfconsistent response, we use the M3DC1 code, a nonideal fluid MHD code. To analyze the influence of plasma response on the synthetic soft xray images, we investigate in detail the change in the magnetic topology between the vacuum approximation and the same case with the M3DC1 plasma response included. In the next step, synthetic images are calculated for both cases. The synthetic images are compared to determine if the plasma response can be resolved. [Preview Abstract] 

GP8.00084: Test of Plasma Equilibrium Response against MHD Models Using Slowly Rotating 3D Magnetic Perturbations in \hbox{DIIID} RMP Experiments L.L. Lao, N.M. Ferraro, R.J. Buttery, T.E. Evans, R.J. La Haye, E.J. Strait, A.D. Turnbull, M.R. Wade, W. Guo, M.J. Lanctot, E.A. Lazarus, A.C. Sontag, R. Nazikian, Y.Q. Liu Slowly rotating nonaxisymmetric magnetic perturbations provide a convenient means to study plasma response to perturbation fields in \hbox{Hmode} discharges using \hbox{DIIID} diagnostics such as the edge Thomson scattering measurements of electron temperature. Magnetic perturbations with $n=1$$$3 have been routinely used to investigate plasma response in DIIID RMP experiments. For $n=1$, a 0.1$$0.3\% perturbation of the poloidal equilibrium magnetic field can result in a large 2$$4\% change in the edge magnetic topology. Perturbations from higher $n=2$ and 3 typically result in smaller fluxsurface distortions. In this study, the effects of 3D perturbation fields on plasma equilibria from these experiments are tested against theoretical predictions using 3D linear and nonlinear MHD codes \hbox{MARSF}, \hbox{M3DC1}, and VMEC. First comparative results indicate that the response from stable helical kink modes contribute significantly to the observed plasma equilibrium responses. Details will be presented. [Preview Abstract] 

GP8.00085: Validation of BOUT++ Nonlinear ELM Simulations Using Fast Measurements from \hbox{DIIID} M.E. Fenstermacher, X. Xu, I. Joseph, M.J. Lanctot, C.J. Lasnier, W.H. Meyer, B.J. Tobias, L. Zeng Nonlinear edge localized mode (ELM) simulations have now been carried out with BOUT++ [1] at low experimental collisionality using a hyperresistivity model to allow reconnection and ELM crash without formation of unphysically thin current sheets. Multiple fast diagnostic measurements of ELM dynamics are available from DIIID [2,3] to validate these BOUT++ simulations. Using kinetic plasma and $E_r$ profiles averaged over the last 20\% of multiple ELM cycles, BOUT++ linear and nonlinear simulations of a large TypeI ELM in DIIID were performed. Multiple synthetic diagnostics applied to the BOUT++ output (e.g.\ ELM energy loss, pedestal pressure drop, target heat flux, ECE imaging etc.) will be compared with fast magnetics, Thomson scattering, IRTV, ECEI and other measurements of the ELM dynamics.\par \vskip6pt \noindent [1] X.\ Xu {\em et al.}, Nucl.\ Fusion {\bf 51}, 103040 (2011).\par \noindent [2] M.E.\ Fenstermacher {\em et al.}, J.\ Nucl.\ Mater.\ (2012) in press.\par \noindent [3] M.E.\ Fenstermacher {\em et al.}, Plasma Phys.\ Controlled Fusion {\bf 45}, 1597 (2003). [Preview Abstract] 

GP8.00086: Bursts in Electron Cyclotron Emission During ELMs and EHOs in Tokamaks E. Li, M.E. Austin Electron cyclotron emission (ECE) bursts during edge localized modes (ELMs) have been observed and reported in several tokamaks. A number of possible explanations have been suggested, but none describe completely the observed ECE bursts. A key to understanding these bursts is that they always occur during edge MHD activity such as ELMs or EHOs in QHmode plasmas. Other observed properties are that the ECE bursts appear on the lowfieldside with an intensity of several tens or hundreds times the thermal emission level, and with a bandwidth as narrow as the instrumental filter spacing of 400 MHz or narrower. A model based on the basic emission and absorption relationship of ECE in plasma is put forth. We calculate the radiation temperature for different electron velocity distribution functions, but with a small variable resonance frequency within the instrumental bandwidth. The resulting radiation temperature and its spectral width agree well with experimental observations both in nonMaxwellian and Maxwellian distribution, but the radiation temperature in nonMaxwellian case is much higher. [Preview Abstract] 

GP8.00087: The role of nearseparatrix gradients in establishing a link between pedestal stability and the heat flux power channel in DIIID J.H. Nichols, M.A. Makowski, A.W. Leonard, T.H. Osborne, R.J. Groebner, P.B. Snyder, P.C. Stangeby, R. Maingi Despite the key role that each will play in nextgeneration tokamak experiments, a comprehensive theory linking the physics of pedestal formation and stability to the physics governing the heat flux power channel has not yet been developed. Data taken from the highresolution edge Thomson scattering system on the DIIID tokamak has been analyzed to try to lay an empirical foundation for this link. Analysis is focused on gradients and gradient scale lengths near the separatrix: the upstream scale lengths are compared to divertor heat flux width measurements, and the upstream edge gradients are compared to calculated critical gradients for instabilities relevant to pedestal stability. As a first step, the infiniten ballooning mode is used as a proxy for the kinetic ballooning mode (KBM) that is thought to be partially responsible for setting the pedestal height and width. Results are presented from shot sequences scanning various important physics parameters, including electron density, injected beam power, and upper triangularity. [Preview Abstract] 

GP8.00088: Advances in Predictive Capability of Pedestal Structure from FY11 Joint Research Target R.J. Groebner, P.B. Snyder, C.S. Chang, J.W. Hughes, R. Maingi, X.Q. Xu Joint experiment/theory/modeling research, performed as part of a US DOE Joint Research Target in FY2011, has led to improved predictive capability of the Hmode pedestal structure. Comparisons of experiments in CMod, DIIID and NSTX with ELITE and BOUT++ show that the pedestals in the three machines reach the predicted peeling/ballooning (PB) limit at the onset of TypeI ELMs. Studies in all three devices show that the pedestal width scales approximately as the square root of the pedestal beta poloidal. This is expected if the pedestal $p^{'}$ is limited by kinetic ballooning modes (KBMs). Coherent density fluctuations with characteristics expected for KBMs have been observed in some plasma conditions in DIIID. The EPED model combines models for bootstrap current, PB modes and KBMs and predicts the pedestal pressure in DIIID and CMod to within $\sim$20\%. [Preview Abstract] 

GP8.00089: Predicting and Optimizing Pedestal Height With the EPED Model P.B. Snyder, R.J. Groebner, T.H. Osborne, J.W. Hughes, H.R. Wilson Fusion energy performance of tokamak plasmas is expected to scale strongly with the pressure at the top of the edge transport barrier (or ``pedestal height''). The EPED model predicts pedestal height by combining calculated peelingballooning (PB) and kinetic ballooning mode (KBM) constraints. EPED has been successfully compared to 270 cases on five tokamaks finding $\sim$20\% agreement with observed pedestal height. Avenues for further optimizing the pedestal height on existing devices as well as ITER are explored, including ``Super HMode'' operation. Ongoing development of the model, including direct electromagnetic gyrokinetic calculations, is also discussed, as is application of the model to edge localized mode suppressed regimes. [Preview Abstract] 

GP8.00090: Phase Contrast Imaging Measurements of Short Wavelength Turbulence Generated by Shear in the \hbox{QHmode} Edge on \hbox{DIIID} J.C. Rost, M. Porkolab, J.R. Dorris, A. Marinoni, K.H. Burrell The Phase Contrast Imaging (PCI) diagnostic on \hbox{DIIID} provides a lineintegrated measurement of density fluctuations covering wavenumbers 2 to 30~cm$^{1}$. An outer gap scan during \hbox{QHmode} with stationary plasma parameters allowed the PCI to sample a large range in $k_r/k_\theta$. A narrow peak in turbulence amplitude is seen near the LCFS. The ExB Doppler shift allows the location to be determined precisely, showing two distinct regions of turbulence at 0.5 and 0.2~cm inside the LCFS with $k_r>0$ and $k_r<0$ respectively, consistent with the expected effects of shear in the Er well. PCI measurements at 200~kHz show that $k_\theta =0.8$~cm$^{1}$ with poloidal correlation length $L_\theta =6$~cm. Using a simple nonisotropic turbulence model, we find that $\mid k_r\mid =3$~cm$^{1}$ and $L_r=0.5$~cm, with $\tilde{n}/n\sim 25$\% in the pedestal for this high$k_r$ turbulence. These fluctuations, which are outside the parameter range accessible to most turbulence diagnostics, are large enough in amplitude to play a role in setting the pedestal structure. These PCI observations are qualitatively similar to those made in ELMfree \hbox{Hmode} and between ELMs suggesting that similar large $k_r$ turbulence may be important. [Preview Abstract] 

GP8.00091: ECEImaging of the Hmode Pedestal on \hbox{DIIID} B.J. Tobias, C.W. Domier, N.C. Luhmann, Jr., M.E. Austin Forward modeling of ECE originating near the edge of \hbox{DIIID} plasmas has improved our understanding of radiation properties in this region and enabled interpretation of ECEImaging and radiation temperature profiles of the \hbox{Hmode} pedestal. A variety of coherent edge modes have been imaged, revealing the nature of the edge harmonic oscillation (EHO) present in \hbox{QHmode} plasmas, as well as directly diagnosing the plasma response to RMP fields applied for ELM suppression. Attempts to image the most fleeting aspects of ELMs in low density \hbox{Hmode} discharges have revealed intense bursts of millimeter wave radiation. Initiating during ELM precursor oscillations and prevalent at ITER relevant collisionality, these bursts appear to be coherent, stimulated emission from thermal electrons interacting with a nonaxisymmetric perturbation of the plasma boundary. [Preview Abstract] 

GP8.00092: Evolution of Edge Pedestal Profiles Between ELMs J.P. Floyd, W.M. Stacey, R.J. Groebner The measured edge profile evolution in DIIID discharges is analyzed in terms of the implied thermal diffusivities, ion diffusion coefficients and pinch velocities, using the momentumbalance methodology of Ref. [1], extended to take into account ion orbit loss and Xpoint loss. The evolution of the density, temperature, rotation and radial electric field profiles in the edge pedestal between edge localized modes (ELMs) provides information of these diffusive and nondiffusive transport processes in the pedestal of Hmode plasmas. This methodology is incorporated in the GTEDGE code developed for \hbox{DIIID} data interpretation. Using a smaller integration time for the charge exchange recombination measurements than in Ref.~[1] allows a more detailed examination of the time evolution of the ion temperature and rotation profiles.\par \vskip6pt \noindent [1] W.M.\ Stacey and R.J.\ Groebner, Nucl.\ Fusion {\bf 51}, 063024 (2011). [Preview Abstract] 

GP8.00093: Evolution of Edge Pedestal Profiles Over the LH Transition M.S. Sayer, W.M. Stacey, J.P. Floyd, R.J. Groebner The detailed time evolution of thermal diffusivities, electromagnetic forces, pressure gradients, particle pinch and momentum transport frequencies (which determine the diffusion coefficient) have been analyzed during the LH transition in a DIIID discharge. Density, temperature, rotation velocity and electric field profiles at times just before and after the LH transition are analyzed in terms of these quantities. The analysis is based on the fluid particle balance, energy balance, force balance and heat conduction equations, as in Ref.~[1], but with much greater time resolution and with account for thermal ion orbit loss. The variation of diffusive and nondiffusive transport over the LH transition is determined from the variation in the radial force balance (radial electric field, $V\times B$ force, and pressure gradient) and the variation in the interpreted diffusive transport coefficients.\par \vskip6pt \noindent [1] W.M.\ Stacey and R.J.\ Groebner, Phys.\ Plasmas {\bf 17}, 112512 (2010). [Preview Abstract] 

GP8.00094: Comparison of an Extended Rotation Theory with Experiment C. Bae, W.M. Stacey, W.M. Solomon An extended neoclassical rotation theory (poloidal and toroidal) is developed from the fluid moment equations, using the Braginskii decomposition of the viscosity tensor extended to generalized curvilinear geometry and a neoclassical calculation of the parallel viscosity coefficient interpolated over collision regimes. Important poloidal dependences are calculated using the Miller equilibrium flux surface geometry representation, which takes into account elongation, triangularity, the Shafranov shift and flux surface compression/expansion. The resulting set of eight (for a twoionspecies plasma model) coupled nonlinear equations for the flux surface averaged poloidal and toroidal rotation velocities and for the updown and inout density asymmetries for both ion species are solved numerically. Comparison of prediction with measured carbon poloidal and toroidal rotation velocities in coinjected and counterinjected Hmode discharges in DIIID indicates agreement to within $<$10\% except in the very edge ($\rho > 0.95$). [Preview Abstract] 

GP8.00095: Pedestal Evolution Studies Using LIBEAM on DIIID D. Thomas, T.H. Osborne, R.J. Groebner, A.W. Leonard, H. Stoschus, C.M. Koch, M.F. Martin, M.A. Makowski Measurements using the refurbished LIBEAM accelerator have been used during the 2012 experimental campaign to address several pedestal issues on DIIID. Careful measurements of the temporal and spatial evolution of the pedestal are important for improving our empirical understanding of pedestal development and for testing pedestal models. The 30 kV neutral lithium beam is particularly suited for these measurements because it is nonperturbative and can yield highly localized measurements of density and local poloidal field through the scrapeoff layer to the top of the pedestal for most DIIID plasmas. Examples presented include the cyclic variation of edge current density with pedestal modification due to LHL transitions, localized effects due to the application of resonant Magnetic Perturbations, and variations in the pedestal width correlated with divertor strike point width and power. Studies are also underway to evaluate the potential of LIBEAM to yield other pedestal parameters including localized ion temperature and $Z_{eff}$ profiles. [Preview Abstract] 

GP8.00096: Effect of OffAxis Beam Injection on Alfv\'en Eigenmodes W.W. Heidbrink, Xi Chen, M.A. Van Zeeland, B.A. Grierson, B.J. Tobias Offaxis injection of neutral beams provides new insights into Alfv\'en eigenmodes (AEs). Offaxis injection flattens the local fastion gradient $\nabla\beta_f$ in the core, completely stabilizing reversed shear AEs (RSAEs). In contrast, at larger minor radius, $\nabla\beta_f$ is similar for on and offaxis injection. As a result, switching the angle of injection has little effect on the stability of global toroidal AEs. Twodimensional measurements of RSAE mode structure with an electron cyclotron emission imaging diagnostic show that the phase of the eigenfunction varies with radius. The phase variation was originally attributed to symmetry breaking associated with the fastion gradient but, unexpectedly, changes in $\nabla\beta_f$ have little effect on radial shearing. The mode structure of lowerfrequency betainduced Alfv\'enacoustic eigenmodes (BAAE) is similar to RSAEs. The BAAE real frequency is quite sensitive to $\nabla\beta_f$ but, surprisingly, stability is not. [Preview Abstract] 

GP8.00097: Localized FastIon Induced Heat Loads in Test Blanket Module Mockup Experiments on DIIID G.J. Kramer, R.V. Budny, R.A. Ellis, R. Nazikian, A.G. McLean, N.H. Brooks, M.J. Schaffer, M.A. Van Zeeland, W.W. Heidbrink, T. KurkiSuonio, T. Koskela, K. Shinohara, J.A. Snipes, D.A. Spong Localized hot spots can be created in ITER on the Test Blanket Modules (TBMs) because the ferritic steel of the TBMs distorts the local magnetic field near the modules and alters fast ion confinement. Predicting the TBM heat load levels is important for assessing their effects on the ITER first wall. Experiments in DIIID were carried out with a mockup of the ITER TBM ferromagnetic error field to provide data for validation of fastion orbit following codes. The front surface temperature of the protective TBM tiles was imaged directly with a calibrated infrared camera and heat loads were extracted. The detailed spot sizes and measured heat loads are compared with results from heat load calculations performed with a suite of orbit following codes. The codes reproduce the hot spots well, thereby validating the codes and giving confidence in predictions for fastion heat loads in ITER. [Preview Abstract] 

GP8.00098: Effects of magnetic perturbations and plasma response on loss of fast ions to the wall in DIIID and ITER M. Choi, N.M. Ferraro, L.L. Lao, V.S. Chan External magnetic coils have been used to control locked modes and edge localized modes (ELMs) in present tokamaks and are under consideration for use in ITER. A previous study on its effects on the loss of fast ions for a steady state ITER scenario indicates that the perturbation fields can cause a significant power loss of neutral beam injection (NBI) fast ions [1]. In that study, the effect of plasma response is not included. In this work, the effect of magnetic perturbations on the fast ion loss rate is considered using both a vacuum model and a twofluid resistive plasma response model. The plasma response to the applied nonaxisymmetric fields is calculated using the nonideal fluid code M3DC$^1$. Preliminary investigation in a typical DIIID plasma, using the 5D finiteorbit MonteCarlo code ORBITRF, indicates that a significant amount of 100~keV NBIproduced fast ions located near the magnetic resonant surfaces may be lost to the wall due to the effects of Coulomb collisions and large drift orbit widths. First results on the losses of fast ions at the presence of magnetic perturbations in typical DIIID plasmas and ITER, using ORBITRF/M3DC1, will be reported in this paper. \vskip2pt\noindent [1] K. Tani et. al, Nucl. Fusion {\bf 52} (2012) 013012. [Preview Abstract] 

GP8.00099: Gyrokinetic Simulation of Global and Local Alfv\'en Eigenmodes Driven by Neutral Beam Injection in DIIID E.M. Bass, R.E. Waltz In ITER, convection of fusionproduced alpha particles by energetic particle (EP)driven Alfv\'en eigenmodes (AEs) risks wall damage and loss of alpha heating needed for ignition. We examine beamexcited AEs and induced quasilinear transport in a DIIID AE experiment using the gyrokinetic code GYRO [1]. Global, linear eigenvalue simulations show reverseshear AEs (RSAEs), toroidal AEs, and betainduced AEs interacting over one (equilibrium time scale) RSAE frequency sweep. Eigenfunction modifications over MHD, including a poloidal twist and broad AE footprint observed in electron cyclotron emission imaging [2], show the value of a kinetic approach. Under a simple quasilinear saturation assumption, a sequence of comparatively inexpensive local simulations quantitatively recreates some global features, notably the quasilinear transport footprint. Accordingly, we present here a stiff EP transport model where AEs limit the EP density gradient to the local stability threshold, and a TGLFdriven quasilinear model elsewhere. The model gives some``worst case'' predictions of the AElimited alpha profile in ITER.\\[4pt] [1] J.~Candy and R.E.\ Waltz, Phys.\ Rev.\ Lett.\ {\bf 91}, 045001 (2003).\par \noindent [2] B.J.\ Tobias, et al., Phys.\ Rev.\ Lett.\ {\bf 106}, 075003 (2011). [Preview Abstract] 

GP8.00100: Gyrokinetic simulations of Reverse Shear Alfven Eigenmodes in DIIID plasmas Scott Parker, Yang Chen, Tobin Munsat, Michael Van Zeeland, William Heidbrink, Benjamin Tobias, Calvin Domier A gyrokinetic ion/massless fluid electron hybrid model as implemented in the GEM code\footnote{Y.~Chen and S.~E.~Parker, J. Comp. Phys. 220, 837 (2007)} is used to study the Reverse Shear Alfven Eigenmodes (RSAE) observed in DIIID, discharge 142111. This is a well diagnosed case with measurement of the corelocalized RSAE frequency chirping and mode structure. Simulations reproduce many features of the observation, including the mode frequency upchirping in time and the chirping range. A new algorithmic feature is acdded to the GEM code for this study. Instead of the gyrokinetic Poisson equation itself, its time derivative, or the vorticity equation, is solved to obtain the electric potential, and this permits a numerical scheme that ensures the ExB convection of the equilibrium density profiles for each species cancel each other in the absence of any finiteLarmorradius effects. These nonlinear simulations generally result in an electron temperature fluctuation level comparable to measurements, but the mode frequency has a spectrum broader than the experimental spectrum. The spectral width from simulations can be reduced if less steep beam density profiles are used, meanwhile the experimental fluctuation level can still be reproduced if [Preview Abstract] 

GP8.00101: Measurements and Modeling of Fastion Light From Edge Neutrals N.G. Bolte, W.W. Heidbrink, E.A. Unterberg Fast ions that are expelled to the plasma edge produce bursts of Dopplershifted fastion $D_\alpha$ (FIDA) light when they charge exchange with edge neutrals [1]. Presently, active FIDA diagnostics use injected neutrals to diagnose confined fast ions but passive FIDA measurements could diagnose losses or provide information on the edge neutral density. In a quantitative test of the technique, prompt losses from a modulated beam provide a known source of fast ions. The edge neutral density is inferred by tomographic inversion of $D_\alpha$ and $D_\gamma$ data. The FIDA spectrum is measured by an instrument that does not view the modulated beams. The data are compared with predictions of a new passive FIDA simulation code that is based on our active FIDA simulation code, FIDASIM [2].\par \vskip6pt \noindent [1] W.W.\ Heidbrink, {\em et al.}, Plasma Phys.\ Control.\ Fusion {\bf 53}, 085007 (2011).\par \noindent [2] W.W.\ Heidbrink, {\em et al.}, Commun.\ Comput.\ Phys.\ {\bf 10}, 716 (2011). [Preview Abstract] 

GP8.00102: Towards Bayesian Inference of the FastIon Distribution Function L. Stagner, W.W. Heidbrink, M. Salewski The fastion distribution function (DF) has a complicated dependence on several phasespace variables. The standard analysis procedure in energetic particle research is to compute the DF theoretically, use that DF in forward modeling to predict diagnostic signals, then compare with measured data. However, when theory and experiment disagree (for one or more diagnostics), it is unclear how to proceed. Bayesian statistics provides a framework to infer the DF, quantify errors, and reconcile discrepant diagnostic measurements. Diagnostic errors and ``weight functions" that describe the phase space sensitivity of the measurements are incorporated into Bayesian likelihood probabilities, while prior probabilities enforce physical constraints. As an initial step, this poster uses Bayesian statistics to infer the DIIID electron density profile from multiple diagnostic measurements. Likelihood functions for various fastion diagnostics are also described. [Preview Abstract] 

GP8.00103: Resolving the Physics of Error Field Correction Through Error Field Proxy Experiments in DIIID R.J. Buttery, N.M. Ferraro, R.J. La Haye, M.J. Schaffer, E.J. Strait, J.M. Hanson, J.K. Park, H. Reimerdes Recent studies have determined the scale and likely origins of limitations to error field correction by using DIIID's multiple coil arrays to apply known large amplitude proxy error fields and attempting correction with additional coils of different structure. It was found that even with pure $n=1$ proxy fields and carefully optimized correction field, the benefits of correction were substantially limited, at the $\sim$50\% level in terms of low density access. This indicates coupling of residual fields either through higher order resonances and/or through nonresonant braking of the plasma The interpretation is confirmed by modeling with the IPEC code, which shows that the correction process reduces resonant components, but increases nonresonant NTV damping, thus decreasing rotation and easing penetration of residual resonant fields. The result is significant, suggesting multiple field components must be compensated to achieve good correction, and that the best approach may be to minimize the total field in the plasma by cancelling error fields close to their source or close to the plasma. [Preview Abstract] 

GP8.00104: Model for Effect of NonResonant Error Field on Resonant Error Field Locking in Ohmic Plasmas in DIIID R.J. La Haye, E.J. Strait, M.J. Lanctot, C. PazSoldan Relatively small resonant ($m/n=2/1$) static error fields $B_{res}$ are shielded in Ohmic plasmas by the natural rotation at the electron diamagnetic drift frequency. However at low enough density and/or high enough $B_{res}$ the drag due to $B_{res}$ lowers rotation such that a bifurcation results going from shielding to an amplified state, a locked mode [1]. The empirically wellknown Ohmic scaling is locking density $\sim$$B_{res}$; this breaks down at lower density in DIIID with either optimized error field correction by the $n=1$ Ccoil (no handedness) or at yet lower density with the $n=1$ Icoil (with ``dominantly" resonant field pitch). Relatively larger nonresonant error fields $B_{nonres}$ also exert drag on the plasma rotation but pull the rotation in the ion diamagnetic drift direction [2]. An analytic model that includes both resonant and nonresonant drag accounts for the limit on low density. The possibility of improved correction, i.e. less drag, by using both coil sets will be considered.\par \vskip6pt \noindent [1] J.T.\ Scoville and R.J.\ La Haye, Nucl.\ Fusion {\bf 43}, 250 (2003).\par \noindent [2] R.J.\ La Haye, S.~Guenter, D.A.\ Humphreys, J.~Lohr, T.C.\ Luce, {\em et~al.}, Phys.\ Plasmas {\bf 9}, 2051 (2002). [Preview Abstract] 

GP8.00105: Assessment of Error Field Control with the ``\boldmath{$n=1$} Coil'' C. PazSoldan, E.J. Strait, R.J. La Haye, R.J. Buttery, J.M. Hanson, M.J. Lanctot Small deviations from the nominally axisymmetric field of a tokamak (termed the `error field') can drastically alter plasma performance. Improved performance can be achieved using arrays of nonaxisymmetric coils to optimize the error field. One metric for evaluating error field control is the lockedmode density limit in Ohmic plasmas, where better compensation allows operation at lower density. Based on this metric, not all coils are equally beneficial for error field control. On \hbox{DIIID}, the best correction was achieved by using a circular coil (called the `$n=1$ coil') placed above and offcenter to the machine in conjunction with an array of midplane saddle coils (called the \hbox{`Ccoil'}) [1]. We use recently developed analysis techniques that include the plasma response to examine why this coilset proved so successful on \hbox{DIIID}. The distinct roles of resonant and nonresonant error fields will be assessed. \vskip6pt\noindent [1] J.T. Scoville and R.J. La Haye, Nucl. Fusion {\bf 43}, 250 (2003). [Preview Abstract] 

GP8.00106: Resistive wall mode stability and plasma response modeling of DIIID plasmas F. Turco, J.M. Bialek, J.M. Hanson, G.A. Navratil, S.A. Sabbagh, M.J. Lanctot, H. Reimerdes, Y. Liu Recent \hbox{DIIID} experiments have shown the effect of offaxis neutral beam injection (NBI) on the resistive wall mode (RWM) stability, evaluated by means of active MHD spectroscopy. This work is focused on new modeling efforts aimed at investigating the role of kinetic damping in the stabilization of the RWM. In \hbox{DIIID} experiments, the latter is affected by the changes in the fast ion distribution, due to varying on and offaxis beam combinations used to sustain the plasma current. The MARS code is used to evaluate the ideal stability and the predicted plasma response using modeled experimental equilibria, which are compared to experimental results. Results on pressure, frequency and plasma rotation scans are presented, comparing equilibria with constant beta, and different fractions of offaxis NBI power. Comparison of the kinetic damping model to experiment will shed light on the role of fast ions in the stability of the RWM at moderate to high beta plasmas. [Preview Abstract] 

GP8.00107: Effect of Fast Ion Distribution on Resistive Wall Mode Stability J.M. Hanson, J. Berkery, G.A. Navratil, S.A. Sabbagh, F. Turco, M.J. Lanctot, H. Reimerdes, I. Chapman, Y. Liu, M. Okabayashi, G.L. Jackson, R.J. La Haye, E.J. Strait DIIID experiments with offaxis NBI yield evidence for the impact of passing fast ions on resistive wall mode (RWM) stability. The fast ion radial and pitch angle distribution can be modified in DIIID by offaxis neutral beam injection (NBI). Offaxis injection results in an increased fraction of passing ions relative to onaxis injection. RWM stability is assessed by measuring the plasma response to a slowly rotating $n=1$ perturbation. The plasma response decreases in amplitude as the fraction of offaxis neutral beam injected ions is increased at constant normalized beta, implying increased RWM damping. Transport and stability modeling using a fixed pressure profile also indicate increased RWM damping with offaxis NBI, due to increased damping from passing fast ions. While previous investigations have confirmed the importance of trapped thermal and fast ions, this result is the first experimental evidence of the significance of passing fast ions for RWM stability. [Preview Abstract] 

GP8.00108: Design of a 3D Magnetic Diagnostic System for \hbox{DIIID} J.D. King, E.J. Strait, R.L. Boivin, R.J. La Haye, L.L. Lao, D.J. Battaglia, N.C. Logan, J.M. Hanson, M.J. Lanctot, A.C. Sontag A new set of magnetic sensors has been designed to diagnose the 3D plasma response due to applied resonant magnetic perturbations (RMPs). The system will also allow for detailed investigation of locked modes and the effects of error fields. This upgrade adds more than 100 colocated radial and poloidal field sensors positioned on the high and low field sides of the tokamak. The sensors are arranged in toroidal and poloidal arrays. Their dimensions and spacing are determined using \hbox{MARSF} and IPEC model predictions to maximize sensitivity to expected 3D field perturbations. Irregular toroidal spacing is used to minimize the condition numbers for simultaneous recovery of toroidal mode numbers $n\leq 4$. A subset of closely spaced sensors will also be installed to measure short wavelength MHD such as ELM precursors and TAEs. [Preview Abstract] 

GP8.00109: Application of the Ideal Perturbed Equilibrium Code to \hbox{DIIID} Magnetic Diagnostic Upgrade Designs N.C. Logan, J.E. Menard, J.K. Park, E.J. Strait The Ideal Perturbed Equilibrium Code (IPEC) has been upgraded with advanced visualization tools and synthetic diagnostics to make its output directly comparable with \hbox{DIIID} diagnostic measurements. Using the synthetic magnetic diagnostics, IPEC has been used to assist in the design of an advanced 3D magnetic field diagnostic currently being built as an upgrade to the \hbox{DIIID} tokamak experiment. This poster outlines the application of IPEC modeling to the magnetic diagnostic design, highlighting the power and versatility of both the computational tools and proposed diagnostics. Of the many new measurements that will be possible with the magnetic diagnostic upgrade, special emphasis is given here to the ability to directly measure electromagnetic torques on the plasma. The magnetic diagnostic design will be able to simultaneously measure electromagnetic torque from nonaxisymmetric fields with toroidal mode numbers 1, 2 and 3. This will open the door to many new possibilities in studying rotational braking effects that will be further supported by IPEC. [Preview Abstract] 

GP8.00110: Study on Sawtooth and ELM activities in DIIID and KSTAR Plasmas J.G. Bak, H.S. Kim, S.G. Lee, K.D. Lee, W.H. Ko, J. Kim, Y.M. Jeon, W.C. Kim, Y.S. Bae, E.J. Strait, R.J. La Haye, R.J. Buttery, M.R. Wade, J.K. Park, J.M. Hanson Sawtooth precursor oscillations (SPOs) are studied in neutral beam heated plasmas on \hbox{DIIID} and KSTAR. The characteristics of the SPO (520 kHz, $m/n=1/1$) are investigated using magnetic sensors along with electron cyclotron emission (ECE) and soft xray diagnostics. In addition, the Type I edge localized mode (ELM) precursors (840 kHz, $n=2,3$) are detected before the ELM burst in neutral beam heated plasmas. The characteristics of the ELM precursors are investigated by using magnetic sensor data. In this work, the experimental investigations of the SPOs and ELM precursors in DIIID and KSTAR plasmas will be presented. [Preview Abstract] 

GP8.00111: ELMLike Events Excited by the OffAxisFishbone Mode and Accompanied by Electron Density Snake M. Okabayashi, W.M. Solomon, G. Matsunaga, J.R. Ferron, J.S. deGrassie, G.L. Jackson, R.J. La Haye, T.C. Luce, D.C. Pace, E.J. Strait, A.D. Turnbull, M.A. Van Zeeland, J.M. Hanson, F. Turco, W.W. Heidbrink, C.T. Holcomb, M.J. Lanctot, Y. In, Y.Q. Liu Fusion reactors require high confinement of energetic particles (EPs) to achieve fusion gain and prevent wall damage. However, EPs can excite various harmful modes. Recent high beta exploration in DIIID shows that the EPdriven OffaxisFishbone Mode (OFM) triggers an Edge Localized Mode (ELM)like event causing massive wall material (carbon) influx preventing highbeta performance. This event is accompanied by bursting density perturbations observed by the CO$_2$ interferometer, with characteristics of an ideal MHDtype ``electron densitysnake.'' Analysis indicates that the OFM is necessary for the formation of the snake, but that the snake can survive after the OFM decays. The role of the snake in the massive carbon influx event is investigated. [Preview Abstract] 

GP8.00112: Using ECE Measurements to Assess Equilibrium Reconstructions on DIIID M.E. Austin, E. Li, R.F. Ellis Information from electron cyclotron emission (ECE) can be used to evaluate a wide range of plasma parameters in tokamaks outside of $T_e$ profile and $T_e$ fluctuation measurements. On DIIID, the ECE data is increasingly used to assess equilibrium reconstructions and to aid in the determination of the magnetic field and density profile. For reconstructions, the correct location of the magnetic axis and nested flux surfaces is determined by the overlap of the highfieldside and lowfieldside ECE$T_e$ data. Both absolutely calibrated Michelson interferometer and relatively calibrated heterodyne radiometer measurements are employed. For simple profile comparison of EFITs, good calibration of the ECE instruments is of course critical. However, for the case of modulated heat input, it is possible to do the comparison with uncalibrated data using the heat pulse amplitude on flux surfaces. Examples for modulated electron cyclotron heating and sawteeth are given. The effects of errors are discussed and the importance of relativistic and Doppler broadening are also examined. [Preview Abstract] 

GP8.00113: 3D Equilibrium Reconstruction of \hbox{DIIID} Discharges using V3FIT A.C. Sontag, J.H. Harris, M.W. Shafer, E.A. Unterberg, J.D. Hanson, L.L. Lao Nonaxisymmetric perturbations to tokamak magnetic fields have become increasingly important for tokamak operation to modify pedestal profiles. Such modifications have led to ELM mitigation, triggering and full stabilization. These perturbations affect transport and stability at the plasma edge, but the physics mechanisms responsible for these changes are not fully understood. An open question is the degree of penetration of the applied fields, and whether these perturbations result in ideal distortions of the magnetic flux surfaces, create magnetic islands, or stochasticize the edge region. The V3FIT code is being used to reconstruct 3D equilibria for \hbox{DIIID} discharges with the assumption of nested flux surfaces. The present work is a study of the ability of the V3FIT code to reliably reconstruct the plasma equilibrium state for a variety of discharge types with particular focus on the edge pedestal region. A diagnostic set consisting of magnetic diagnostics, ion and electron temperature and density profile and soft \hbox{xray} diagnostics is used for the reconstructions. The ability of these diagnostics to reconstruct equilibria that agree with observed toroidal asymmetries is assessed and the relative effectiveness of each diagnostic is determined. [Preview Abstract] 

GP8.00114: Efficient NonFourier Implementation of LandauFluid Operators in the BOUT++ Code A.M. Dimits, I. Joseph, M.V. Umansky, P.W. Xi, X.Q. Xu Tokamak edge plasmas have regions in which kinetic effects are important, which strongly motivates the implementation of Landaufluid operators in edgeplasma fluid codes such as BOUT++. However, they also have significant spatial inhomogeneities and complicated boundary conditions, which pose significant difficulties for the standard Fourier implementations. We have therefore developed nonFourier, configurationspacebased approaches for the computation of these operators. One of these is a ``fast'' method, with Fourierlike computational scaling, based on an accurate and tunable approximation that can be numerically implemented through the solution of tridiagonal or narrowly banded matrix equations. Another approach, which is useful for moderate mesh sizes, is the direct discretization of the spatial kernel and its application via standard matrix multiplication algorithms. Investigations of the accuracy and computational efficiency of these approaches have been completed and will be presented. We will also show the effects of the inclusion of the Landaufluid closures in BOUT++ simulations on a variety of linear and turbulent microinstabilitydrivent test cases. [Preview Abstract] 

GP8.00115: A upwind PPM with limiter for tokamak edge plasmas simulation under BOUT++ framework Chenhao Ma, Xueqiao Xu To study the propagation of blobs driven by edge plasma instability, the PPM should be applied to improve numerical accuracy. The upwind Piecewise Parabolic Method(PPM) with limiter preserves accuracy at smooth extrema. The interpolated values only at extrema is restricted by nonlinear combinations of various different approximations of the second order derivatives. This method has the same accuracy for smooth initial data as PPM without limiter and preserves shape of initial data exactly during its propagation. BOUT++ is a C++ framework for 3D plasma fluid simulation in real geometry, including both open and closed field lines, and was developed in part from the original fluid edge code BOUT. Our goal is to implement the PPM with limiter as one of numerical differencing methods in BOUT++'s library. Because the spatial scale of blobs driven by edge plasma instability are typically ten times smaller than the simulation region, the PPM with limiter will preserve the shape of blobs exactly at smooth extrema and provide better long time simulation result. [Preview Abstract] 

GP8.00116: ETG turbulence simulation of tokamak edge plasmas via 3+1 gyrofluid code P.W. Xi, X.Q. Xu, A. Dimits, M. Umansky, I. Joseph, S.S. Kim To study ETG driven turbulence at Hmode pedestal, which is important for the magnetic reconnection of ELM dynamics via ETGMHD interaction, a 3+1 gyrofluid code is developed under BOUT++ framework. Four evolving quantities are density, parallel velocity, parallel pressure and perpendicular pressure for electron and adiabatic ion is used. Gyroaverage is done by utilizing Pad\'e approximation and parallel Landau closure for Landau damping is implemented by using a newly developed nonFourier method. By calculating the ETG mode growth rate and real frequency for the ETG cyclone equilibrium, our code is benchmarked with gyrokinetic codes. We also calculated the electron heat transport level at turbulence saturation phase for both cyclone case and Hmode pedestal. Because the pedestal width is typically ten times larger than ETG simulation domain, the three different region of pedestal, i.e. pedestal top, peak gradient region and pedestal bottom, are simulated separately. The dramatic difference on magnetic shear and temperature length scale of these three regions lead to different ETG linear and nonlinear behaviors. [Preview Abstract] 

GP8.00117: Core Gyrofluid Simulations of Ion Temperature Gradient Turbulence Using BOUT++ S.S. Kim, X.Q. Xu, Hogun Jhang, Tongnyeol Rhee, S. Tokunaga, P.W. Xi, P.H. Diamond Starting from a tokamak edge plasma simulation code, BOUT++ has evolved into a versatile framework that can be used to simulate a wide range of fluid models in complicated magnetic geometry. Extension of the code into the core region is a natural outgrowth, aiming at the possible integration of selfconsistent coreedge coupling. In this regard, we developed a core gyroLandaufluid code using a 3field model. Landau damping is implemented using the HammettPerkins closure that has been realized in configuration space to cope with the BOUT++ framework. Verification of the code was realized by comparing linear growth rates calculated from BOUT++ with those from an eigenvalue solver and gyrokinetic codes. Ongoing works focus on the physics studies of the internal transport barrier (ITB) formation in a reversed shear plasma. In particular, we emphasize the role of nonresonant modes on the ITB formation. Details of the code development and preliminary physics results will be presented. [Preview Abstract] 

GP8.00118: Comparison study between the observed ELM dynamics in the KSTAR Hmode and simulation results from BOUT++ Minwoo Kim, Xueqiao Xu, Gunsu S. Yun, Jaehyun Lee, Hyeon K. Park The BOUT++ simulations [1] of edge localized modes (ELMs) have been quantitatively compared with high resolution 2D images of ELMs observed in typical KSTAR Hmode plasmas through an electron cyclotron emission imaging (ECEI) system [2]. The poloidal structure of the most unstable mode predicted by the linear 3field simulation qualitatively matches with the observed ELM structure. As the next step, simulation studies for the nonlinear aspects of the ELM dynamics are planned; in particular, the transient mode structure change prior to the ELM crash [2] will be investigated. In addition, the parametric dependence of the observed ELM suppression/mitigation process during resonant magnetic perturbation (RMP) [2, 3] and supersonic molecular beam injection (SMBI) experiments will be studied using 5field BOUT++ simulation.\\[4pt] [1] X.Q. Xu et al., PRL, \textbf{105} (2010).\\[0pt] [2] G.S. Yun et al., Phys. Plasmas, \textbf{19} (2012).\\[0pt] [3] Y.M. Jeon et al., accepted for publication in PRL. [Preview Abstract] 

GP8.00119: ECE imaging of modified edge localized modes (ELMs) under n=1 magnetic perturbations in KSTAR Jaehyun Lee, G.S. Yun, M. Kim, M.J. Choi, W. Lee, H.K. Park, J.H. Lee, Y.M. Jeon, C.W. Domier, N.C. Luhmann, Jr., A.J.H. Donn\'e In order to control the ELMs in KSTAR Hmode plasmas, magnetic perturbations (MPs) of toroidal mode number n=1 were introduced through three sets of field error correction (FEC) coils [1] during the 2011 campaign. The plasma response was studied in 2D using electron cyclotron emission imaging (ECEI) diagnostic [2], which showed alteration of both the spatial structure and temporal dynamics of the ELMs. The characteristics of the ELMs such as the growth rate, filament size, and poloidal flow are compared before and after the n=1 MP for various configurations of the FEC coil currents. In particular, the ELM suppression by resonant MP condition is characterized by occasional (nonperiodic) tiny transport events, which involve the appearance and crash of transient filament structure localized near the separatrix.\\[4pt] [1] Y. Jeon et al., accepted for publication in Phys. Rev. Lett.\\[0pt] [2] G.S. Yun et al., Phys. Rev. Lett., 107, 045004 (2011). [Preview Abstract] 

GP8.00120: BOUT++ Simulations of ELMs with FourField Model Tongnyeol Rhee, G.Y. Park, H.G. Jhang, S.S. Kim, P.H. Diamond, X.Q. Xu Filamentary edge localized modes (ELM) structures has been often observed in numerous tokamak Hmode discharges. To understand/interpret these observations, we study linear and nonlinear ELM phenomena and the associated dynamics using the BOUT++ code. In this work, we perform ELM simulations using a fourfield model [1]. This model improves the previous threefield equations by including additional physics such as parallel compressibility, electron Hall, and finite Larmor radius effects, which are all important in a steep gradient pedestal region [2]. Preliminary linear simulation results with the fourfield model show the qualitative agreement with those from the threefield equations. Furthermore, we study the coupled effects of Alfven, drift, and ion sound waves on linear growth of the pedestal instability showing a significant modification of the linear results of ideal peelingballooning mode theory. Ongoing works include the study of ELM responses to the soft edge pedestal perturbations and the application of resonant magnetic perturbations (RMP) shown to have significant impact on ELM characteristics. We implemented the RMP boundary condition into the BOUT++ code to understand how ELM filamentary structure changes when RMP is applied. Details of the implementation of the fourfield model and physics results will be presented.\\[4pt] [1] R.D. Hazeltine and J.D. Meiss, Phys. Rep., 121, 1 (1985).\\[0pt] [2] X.Q. Xu et al., Phys. Rev. Lett., 105, 175005 (2010) [Preview Abstract] 

GP8.00121: Simulations of Plasma Profile Evolution during SMBI using BOUT++ Code Z.H. Wang, X.Q. Xu, T.Y. Xia, P.W. Xi, L.H. Yao The SBMI (supersonic molecular beam injection) has high fuelling efficiency and low particle recycle coefficient due to the beam particles directed injection. A physical model of SMBI has been developed in BOUT++ framework to study SMBI as an effective fuelling method and a useful tool for plasma control. By adding evolution equations for neutral density and velocities with localized 3D boundary conditions, we study the neutralplasma interactions via ionization and chargeexchange. The SMBI is modeled as a radial advection, instead of diffusion for neutrals as in gaspuffing. In slab geometry, we found that an edge injected SMB can penetrate to bottom pedestal region within about 0.1ms. If plasma density is lower, beams can penetrate further inside the pedestal. Due to neutral ionization, we found plasma density increases and temperature decreases which are qualitatively consistent with the experiments. The fuelling efficiency of the localized 3D SMB and its impact on the ELM mitigation will be studied in tokamak geometry. Quantitative comparisons between simulation and experiment results at HL2A will be reported. [Preview Abstract] 

GP8.00122: Simulations of plasma responses due to RMP and external antenna with BOUT++ code Bin Gui, Xueqiao Xu, Tianyang Xia A minimum set of threefield twofluid equations based on the peelingballooning (PB) model with nonideal physics effects was used to simulate pedestal collapse by Xu, et al using the BOUT++ code (Xu, et al., Nucl. Fusion, 2011). We extended the model to include the resonant magnetic perturbation (RMP), to study the influence of RMP field on the pedestal plasmas turbulence, transport and ELMs. The RMP field is added at the radial boundary and is selfconsistently calculated in the plasma using the twofluid model. Based on this work, we will also upgrade the capability to include high k$_{\bot}$ antenna system to drive driftAlfvenic modes at the outer midplane, to simulate the plasma fluctuations responses in Lmode, Hmode and ELM discharges. This capability can also be used to simulate the SOL plasmawave interaction and impurity transport under a large localized RF sheath potential generated during the plasma heating by ICRF wave. [Preview Abstract] 

GP8.00123: Flutereduced driftMHD model for external magnetic perturbations using the BOUT++ code I. Joseph, M.V. Umansky, X.Q. Xu, M.E. Fenstermacher, M.J. Lanctot, A. Allen, B.D. Dudson, F.L. Waelbroeck Numerical simulations of the plasma response to external magnetic perturbations are performed using a flutereduced driftMHD model implemented within the BOUT++ code [1]. Benchmarks against the linear ideal and resistive response are performed in slab and circular geometry. The plasma response to external magnetic perturbations is necessary to understand the mechanism for controlling edge transport and edge localized mode stability [2]. DriftMHD models that incorporate first order gyroradius effects generally predict that reconnection can only occur at the location where the perpendicular electron velocity vanishes [3]. An experimentally measurable prediction is that the quasilinear torque and induced particle flux should change sign across this point. The effect of hyperresistivity/anomalous electron viscosity on the scaling of reconnection processes is explored both analytically and numerically. \\[4pt] [1] B. D. Dudson, M. V. Umansky, X. Q. Xu, et al., Comput. Phys. Commun. \textbf{180}, 1467 (2009).\\[0pt] [2] I. Joseph, Contrib. Plasma Phys. \textbf{52}, 326 (2012).\\[0pt] [3] F. L. Waelbroeck, I. Joseph, E. Nardon, et al., Nucl. Fusion \textbf{52}, 074004 (2012). [Preview Abstract] 

GP8.00124: Edge Plasma Response to Resonant Magnetic Perturbation in Extended MHD Model P. Zhu Resonant magnetic perturbation (RMP) can suppress and mitigate edge localized modes in tokamak experiments. To understand the effects of RMP on the properties of tokamak edge pedestal, we study the edge plasma response to RMP using the extended MHD models with anisotropic heat transport as implemented in the NIMROD code. A lown RMP is imposed as the boundary condition at the tokamak wall location. Plasma responses to RMP are obtained by following the linear and nonlinear evolution of the configuration into steady state subject to the RMP boundary condition. For stable equilibrium, magnetic islands form on resonant surfaces. For marginally and weakly unstable equilibrium, RMP first drives highern modes to saturation and the edge region becomes stochastic. As the saturated perturbation decays due to dissipations the RMPinduced islands reemerge. For unstable equilibrium, the system is driven to a steady state where island structures are buried in the stochastic edge region. A prescribed subsonic toroidal rotation in the pedestal region is found to slightly shrink the sizes of islands induced by RMP. The flow does not affect the formation and inward expansion of the stochastic region resulting from the highern modes nonlinearly driven by RMP, in the case of unstable equilibrium. [Preview Abstract] 

GP8.00125: Convective radial energy flux due to RMPs at the tokamak plasma edge F. Alberto Marcus, Peter Beyer, Guillaume Fuhr, Arnaud Monnier, Sadruddin Benkadda Transport barriers in tokamak edge plasmas are typically unstable and exhibit quasiperiodic relaxation oscillations associated with high energy flux peaks known as Edge Localize Modes (ELMs). The efficiency of ELMs control by RMPs is enhanced when the RMP amplitude is increased, which is generally attributed to field line stochastisation, induced by overlapping of magnetic islands, and it is due to a reduction in pressure gradient by a radial energy flux. Although the experiments confirmed RMPs as an important tool to control barrier relaxations, the mechanisms of how they work are not well understood, in particular if the penetration is sufficient to produce stochasticity. Here we study an additional mechanism leading to convective radial flux even in the absence of stochasticity.This new mechanism is based on the coupling between electrostatic potential and pressure via magnetic curvature, also leading to poloidal $E \times B$ flow generation.By using the 3D toroidal electromagnetic edge turbulence code EMEDGE3D, we consider cases where the total heat flux and the corresponding pressure gradient are below the microinstability limit. We analyze the effects of the RMP intensity on the convective energy flux and the pressure gradient profile on perturbed magnetic surfaces. [Preview Abstract] 

GP8.00126: The design of a lowcost Thomson Scattering system for use on the ORNL PhIX device T.M. Biewer, J. Lore, R.H. Goulding, D.L. Hillis, L. Owen, J. Rapp Study of the plasmamaterial interface (PMI) under high power and particle flux on linear plasma devices is an active area of research that is relevant to fusiongrade toroidal devices such as ITER and DEMO. ORNL is assembling a 15 cm diameter, $\sim$3 m long linear machine, called the Physics Integration eXperiment (PhIX), which incorporates a helicon plasma source, electron heating, and a material target. The helicon source has demonstrated coupling of up to 100 kW of rf power, and produced n$_e$ $\geq$ 4 x 10$^{19}$ m$^{3}$ in D, and He fueled plasmas, measured with interferometry and Langmuir probes (LP). Optical emission spectroscopy was used to confirm LP measurements that Te is about 10 eV in helicon heated plasmas, which will presumably increase when electron heating is applied. Plasma parameters (ne, Te, n0) of the PhIX device will be measured with a novel, lowcost Thomson Scattering (TS) system. The data will be used to characterize the PMI regime with multiple profile measurements in front of the target. Profiles near the source and target will be used to determine the parallel transport regime via comparison to 2D fluid plasma simulations. This work was supported by the US. D.O.E. contract DEAC0500OR22725. [Preview Abstract] 

GP8.00127: Ongoing Atomic Physics Research for Fusion Diagnostics at the NIST EBIT Yuri Podpaly, John Gillaspy, Yuri Ralchenko, Joseph Reader, John Curry Passive xray spectroscopy on fusion devices uses wellknown emission lines for measuring the plasma rotation and ion temperature profile, impurity surveys, and estimating electron temperature and Zeff. These measurements require the use of wellknown diagnostic lines from injected impurity elements such as argon and krypton and from intrinsic impurities, particularly tungsten. Electron Beam Ion Traps (EBITs), which use electromagnetic traps with a precise electron beam energy to ionize a known charge state of an atom, are ideally suited to study fusionrelevant impurity ions in a controlled environment and generate wavelengths, relative intensities, and crosssections. The ongoing work at the NIST EBIT is presented on tokamakrelevant impurities in the xray and EUV region including studies of diagnostic elements such as krypton and xenon and intrinsic impurity elements such as tungsten, tantalum, hafnium, and gold. [Preview Abstract] 

GP8.00128: Recent Progress of the JTEXT Xray Imaging Crystal Spectrometer Wei Jin, Zhongyong Chen, Duwei Huang, Yonghua Ding, Zhijiang Wang, Ge Zhuang, Sang Gon Lee, Yuejiang Shi An Xray imaging crystal spectrometer (XICS) equipped with a multiwire proportional counter has been developed aiming to measure the electron temperature, ion temperature and toroidal rotation velocity in the JTEXT Ohmic discharges with a count rate of 350 kHz and a temporal resolution of 0.1 s. It records spectra of heliumlike argon from a number of viewing chords with tangential radii from 10 cm to 10 cm vertically. Here the maximum count rate is mainly determined by the electron density and amount of argon particles injected by either PEV1 valve or supersonic molecular beam injection. For a typical JTEXT Ohmic plasma, the core electron temperature of about 700 eV can be deduced from the ratio of resonant line (W line) intensity and its satellites (n = 3) of the spectra, while the ion temperature of about 400 eV is obtained by evaluating the Doppler broaden of resonant line. In addition, the evolution of the relative toroidal rotation velocity can also be given. It is worth to note that in the low density discharges the intensity of satellites (q and r lines) increases to the same level of resonant line. More experimental results and explanations will be presented in the meeting. [Preview Abstract] 

GP8.00129: New Digital Control System for the JET Alfv\'{e}n Eigenmode Active Spectroscopy Diagnostic P.P. Woskov, J. Stillerman, M. Porkolab, A. Fasoli, D. Testa, R. Galvao, A. Pires dos Resis, W. Pires de Sa, L. Ruchko, P. Blanchard, J. Figueiredo, S. Dorling, J. Farthing, M. Graham, S. Dowson, L. Yu, S. Concezzi The stateoftheart JET Alfv\'{e}n active spectroscopy diagnostic with eight internal inductive antennas is being upgraded from a single 5 kW tube amplifier to eight parallel, 10  1000 kHz, 4 kW solid state class D power switching amplifiers. A new digital control system has been designed with arbitrary constant phase controlled frequency sweeps for traveling mode studies, amplifier gain control through a feedback loop referenced to programmed antenna current profiles, and integration with CODAS for synchronization, triggering, gating, and fault tripping. A combination of National Instruments Real Time LabView software and FPGA circuits is used to achieve the multiple control requirements with better than 1 ms response. System specifications and digitalanalog design trade offs for sweep rates, response times, frequency resolution, and voltage levels will be presented. [Preview Abstract] 

GP8.00130: An Electron Cyclotron Emission Imaging (ECEI) System for HL2A Calvin Domier, Shao Che, Michael Huff, Neville C. Luhmann, Jr., Zhongbing Shi, Xuantong Ding, Yi Liu, Qingwei Yang A high resolution Electron Cyclotron Emission Imaging (ECEI) system is under development for the HL2A tokamak in Chengdu, China. The diagnostic instrument has a tunable RF range of 75 to 135 GHz, and will generate 192 channel (24 vertical by 16 radial) images of the 2nd harmonic Xmode radiation from the HL2A plasma, and is equipped with both vertical and horizontal zoom capabilities. Fabrication and characterization are scheduled to be completed by November 2012, with installation and commissioning on HL2A to take place in early 2013. Details regarding the optical and electronic performance of the system will be presented. [Preview Abstract] 

GP8.00131: Technology Advances in Support of Fusion Plasma Imaging Diagnostics Qi Jiang, Jiali Lai, Fengqi Hu, Maijou Li, YuTing Chang, Calvin Domier, Neville Luhmann, Jr. Innovative technologies are under investigation in key areas to enhance the performance of microwave and millimeterwave fusion plasma imaging diagnostics. Novel antenna and mixer configurations are being developed at increasingly higher frequencies, to facilitate the use of electron cyclotron emission imaging (ECEI) on high field ($>$ 2.6 T) plasma devices. Low noise preamplifierbased imaging antenna arrays are being developed to increase the sensitivity and dynamic range of microwave imaging reflectometry (MIR) diagnostics for the localized measurement of turbulent density fluctuations. High power multifrequency sources, fabricated using advanced CMOS technology, offer the promise of allowing MIRbased diagnostic instruments to image these density fluctuations in 2D over an extended plasma volume in high performance tokamak plasmas. Details regarding each of these diagnostic development areas will be presented. [Preview Abstract] 

GP8.00132: Preliminary results from a novel ECE imaging system under various RF heating schemes on EAST Chen Luo, Bingxi Gao, Yilun Zhu, Jinlin Xie, Tao Lan, Adi Liu, Hong Li, Wandong Liu, Changxuan Yu, Benjamin Tobias, Calvin Domier, Neville Luhmann, Tony Donne, ECE Team, Liqun Hu A novel 384 channel electron cyclotron emission imaging system is installed on EAST with wideband electronics that enables a continuous radial coverage up to 30 cm and a flexible vertical coverage up to 80 cm controlled by zoom optics. Recent investigations of the plasma current rampup and plateau phases reveal various kinds of MHD activities. Detailed 2D ECE images in those phases have revealed different mechanisms around sawtooth crashes. 2D ECE imaging under various auxiliary heating schemes has revealed a superposition of various MHD modes with different harmonics, and the response of these modes to RF power modulation has been studied. Furthermore, low frequency upchirping modes during LHCD have been observed. Finally, the application of several novel analysis techniques for 2D microwave imaging data is discussed. [Preview Abstract] 

GP8.00133: Design of an EightChannel Doppler Backscattering System for use on the EAST Tokamak E.J. Doyle, W.A. Peebles, X. Nguyen, T.L. Rhodes, G. Wang, C. Wannberg, H. Li, A.D. Liu, C. Zhou, C.X. Yu Doppler backscattering (DBS) is a powerful millimeterwave plasma diagnostic used in tokamaks and other magnetic confinement devices to measure turbulence characteristics [1]. DBS systems measure the laboratory frame propagation velocity of intermediate wavenumber density fluctuations, and also monitor fluctuation amplitudes and frequency spectra, with high spatial resolution (cm level). A DBS system has been designed and is under construction for use on the EAST superconducting tokamak, located in Hefei, China. The new system will provide eight simultaneous fixedfrequency Doppler channels, spanning the Vband (5075 GHz) frequency range, i.e. the system will provide eight spatially localized measurement locations. The microwave source design for the EAST system is a modified version that used for the eight channel DBS system on the DIIID tokamak [2]. Details of the modified microwave system design and measured performance characteristics will be presented, along with a design for the microwave interface system for EAST.\\[4pt] [1] M. Hirsch, et al., Plasma Phys. Control. Fusion 43, 1641 (2001).\\[0pt] [2] W.A. Peebles, et al., Rev. Sci. Instrum. 81, 10D901 (2010). [Preview Abstract] 

GP8.00134: High Gain and Frequency UltraStable Integrators for ICC and Long Pulse ITER Applications Kenneth Miller, Timothy Ziemba, James Prager Eagle Harbor Technologies has developed a high gain and frequency ultrastable integrator for small scale concept experiments and long pulse ITER applications. The Phase I integrator has a 10 $\mu $s RC time with a frequency response greater than 10 MHz. The device has been operated for the 3600 s with a drift error less than 600 $\mu $V, which exceeds the ITER specification. Longer period operation is also possible ($>$ 30 hours). Additionally, this integrator has an extremely large dynamic range thereby increasing the effective bit depth of a digitizer. These integrators allow for both the fast and slow magnetic/plasma dynamics to be resolved with a single diagnostic. Data will be presented demonstrating the success of the Phase I program, and the Phase II work plan will be discussed. Work has begun to incorporate the integrators into legacy (CAMAC) and modern (National Instruments) DAQ systems. [Preview Abstract] 

GP8.00135: Measuring drift velocity and electric field in mirror machine by fast photography Ilan Be'ery, Omri Seemann, Amnon Fruchtman, Amnon Fisher, Amiram Ron The flute instability in mirror machines is driven by spatial charge accumulation and the resulting E$\times $B plasma drift. E$\times $B drift due to external electrodes can be used as a stabilizing feedback mechanism. In order to measure the plasma drift and the internal electric field distribution we used fast photography to visualize Hydrogen plasma in a small mirror machine. We use incompressible flow and monotonic decay assumptions to deduce the velocity field from the evolution of the plasma cross section. The electric field perpendicular to the density gradient is then deduced from E=V$\times $B. Using this technique we measured the electric field of the flute instability and the field induced by electrodes immersed in the plasma. [Preview Abstract] 

GP8.00136: Development of a polarization resolved spectroscopic diagnostic for measurements of the vector magnetic field in the Caltech coaxial magnetized plasma jet experiment Taiichi Shikama, Paul M. Bellan In the Caltech coaxial magnetized plasma jet experiment, fundamental studies are carried out relevant to spheromak formation, astrophysical jet formation/propagation, solar coronal physics, and the general behavior of twisted magnetic flux tubes that intercept a boundary. In order to measure the spatial profile of the magnetic field vector for understanding the underlying physics governing the dynamical behavior, a nonperturbing visible emission spectroscopic method is implemented to observe the Zeeman splitting in emission spectra. We have designed and constructed a polarizationresolving optical system that can simultaneously detect the left and rightcircularly polarized emission. The system is applied to singly ionized nitrogen spectral lines. The magnetic field strength is measured with a precision of about +/13 mT. The radial profiles of the azimuthal and axial vector magnetic field components are resolved by using an inversion method. [Preview Abstract] 

GP8.00137: Development of a Radial Electric Field Diagnostic for LTX Using the Stark Effect Fred Levinton, Richard Majeski, Ethan Schartman The Lithium Tokamak eXperiment (LTX) is investigating confinement and transport in the lowrecycling regime of tokamak discharges. A liquid lithium coated shell reduces recycling of particles into the plasma by up to 90\% versus highly recycling walls. Power flow in the edge region is dominated by convection. By reducing the number of particles transporting energy to the wall, the energy per particle must be higher for a constant input power to the plasma core. Therefore a large edge temperature gradient is expected to form in low recycling plasmas. As a consequence of electron force balance, the temperature gradient will produce in LTX a radial electric field of $E_r\sim100$kV/m. Nova Photonics, Inc is developing a high spatialresolution measurement of $E_r$ using Stark splitting of Balmer emission of a diagnostic neutral hydrogen beam. The beam will be injected nearly perpendicular to LTX's toroidal magnetic field with viewing sightlines nearly parallel to the field. This geometry will optimize sensitivity to the radial electric field. The design of the diagnostic and estimates of its performance will be presented. [Preview Abstract] 

GP8.00138: Experimental Measurements of the Dynamic Electric Field Topology Associated with Magnetized RF Sheaths Elijah Martin, John Caughman, Steven Shannon, Christopher Klepper, Ralph Isler The dynamic Stark effect is a phenomenon in which photon(s) associated with an oscillating electric field are absorbed or emitted with the photon associated with an electronic transition. This multiphoton process leads to the formation of satellites in the spectrum at integer multiples of the frequency associated with the dynamic electric field. Utilizing the dynamic Stark effect the electric field parameters can be determined from the timeaveraged and phase resolved emission spectra. Currently two methods are available to calculate the emission spectrum associated with an atomic system in the presence of a dynamic electric field: the quasistatic method and the Floquet method. The methodology and applicability of the quasistatic and Floquet methods will be discussed. The RF sheath electric field parameters are determined, utilizing a generalized dynamic Stark effect model and a novel line shape analysis package, from the timeaveraged and phase resolved optical emission spectra. Results will be presented for working gases of hydrogen and helium. [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