Bulletin of the American Physical Society
49th Annual Meeting of the Division of Plasma Physics
Volume 52, Number 11
Monday–Friday, November 12–16, 2007; Orlando, Florida
Session GP8: Poster Session III: Turbulence, Transport, and NL Processes; Fast Ignition and LaserPlasma Interactions; Divertors, Edge Physics and Fueling; MHD Theory, Heating and Current Drive; Simulation: MHD; Optimal Helicon Source Performance 
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Room: Rosen Centre Hotel Grand Ballroom, 9:30am  12:30pm 

GP8.00001: TURBULENCE, TRANSPORT, AND NONLINEAR PROCESSES 

GP8.00002: Fundamental Scalings of Zonal Flows in a Basic Plasma Physics Experiment Vladimir Sokolov , Xiao Wei , Amiya K. Sen A basic physics experimental study of zonal flows (ZF) associated with ITG (ion temperature gradient) drift modes has been performed in the Columbia Linear Machine (CLM) and ZF has been definitively identified [1]. However, in contrast to most tokamak experiments, the stabilizing effect of ZF shear to ITG appears to be small in CLM. We now report on the study of important scaling behavior of ZF. First and most importantly, we report on the collisional damping scaling of ZF, which is considered to be its saturation mechanism [2]. By varying the sum of ionion and ionneutral collision frequency over nearly half an order of magnitude, we find no change in the amplitude of ZF. Secondly, we study the scaling of ZF amplitude with ITG amplitude via increasing ITG drive though $\eta_i$, as well as feedback (stabilizing / destabilizing). We have observed markedly different scaling near and far above marginal stability. \\ $[1]$ V. Sokolov, X. Wei, A.K. Sen and K. Avinash, \it{ Plasma Phys.Controlled Fusion } 48, S111 (2006). \\ $[2]$ P.H. Diamond, S.I. Itoh, K.Itoh and T.S. Hahm, \it {Plasma Phys.Controlled Fusion } 47, R35 (2005). [Preview Abstract] 

GP8.00003: A Basic Experiment on the Production and Identification of ETG Modes Xiao Wei , Vladimir Sokolov , Amiya K. Sen One of the strongest candidates for the anomalous electron energy transport is believed to be electron temperature gradient (ETG) mode [1, 2]. However, the high frequency (few MHz) and short wave length ($k_\perp\rho_e<1$) make the direct observation of ETG modes difficult in experiments. Using a DC bias heating scheme of the core plasma, we are able to produce the drive parameter $\eta_e = d ln \it{T_e} / d ln \it n $ from 1 to 6 ($ T_e \sim 20 eV $ in the center and $\sim 1eV $ on the edge) in Columbia Linear Machine (CLM). A high frequency mode at $ \sim 2MHz $has been observed. Its azimuthal wave number in $ m \sim 30$ has been measured. These values are consistent with the results of a simple kinetic dispersion relation on appropriate $\vec{E_0} \times \vec {B}$ Doppler shift. The problem of the measurement of the small parallel wave number with the large azimuthal wave number has been resolved by a novel diagnostic method. The scaling of ETG fluctuation level versus $\eta_e$, as well as the radial structure of the mode will be reported. \\ $[1]$ W. Dorland et al., \it {Phys. Rev. Lett.} 85, 5579 (2000). \\ $[2]$ R.E. Waltz, J. Candy and M. Fahey, \it {Phys. Plasmas} 14, 056116 (2007). [Preview Abstract] 

GP8.00004: Edge turbulence scaling in RFXmod with GPI diagnostic Paolo Scarin , Matteo Agostini , Roberto Cavazzana , Gianluigi Serianni In the Reversed Field Pinch eXperiment RFXmod (R=2 m, a=0.46 m) a Gas Puffing Imaging (GPI) diagnostic is routinely used to investigate the dynamical structure of plasma edge turbulence in different plasma conditions. The GPI system (32 optical lines of sight) measures radiation emitted from puffed gas on a plane normal to the local magnetic field. Such diagnostic allows the investigations of edge plasma properties with high time and space resolution even at high plasma current and through the entire plasma pulse. The characterization of edge turbulence has been carried out in terms of power spectrum, toroidal velocity v$_{\phi }$ of emission fluctuations, linear density and toroidal width of emission structures. The packing fraction $f_{p }$ of emission intermittent structures has been estimated as the total area occupied by emission blobs in a plane perpendicular to magnetic field. The scaling with normalized Greenwald density n/n$_{G }$of v$_{\phi }$, $f_{p}$, linear density and toroidal width of emission structures and decay index of the power spectrum are reported. A comparison at different density regimes of the diffusivity D$_{p}$ of the plasma trapped in coherent structures is proposed and a decrease of about a factor of 2 results between low and high n/n$_{G}$ values. [Preview Abstract] 

GP8.00005: ABSTRACT WITHDRAWN 

GP8.00006: Relaxation of weights in a $\delta f$ code Allen Boozer The weight of particle $i$ in a $\delta f$ particle following code obeys $dw_i/dt=\dot{W}(\vec{x}_i,\vec{p}_i)$. The phase space location of the particle is $(\vec{x}_i,\vec{p}_i)$, and $\dot{W}$ is given by derivatives of a background Maxwellian. The weights $w_i$ tend to increase without limit. When the $w_i$ become sufficiently large the approximations used in $\delta f$ codes become invalid. The longterm increase in $w_i$ is unphysical since a particle should loose its history within a collision time. The addition of a term to the weight evolution equation solves the problem, $dw_i/dt=\dot{W}\nu_ww_i$. If the constant $\nu_w$ is chosen to be comparable to, or smaller than, the collision frequency it should have no effect on physically correct outputs of the code, but should keeps the weights at a low amplitude forever. In order to conserve particles, the background Maxwellian must be modified so its density obeys $dn(\psi)/dt=\nu_wn \sum_iw_if_i/\sum_if_i$, where the sum is over an annular radial region. Similar changes in flow and temperature of the background Maxwellian are required to conserve momentum, and energy. [Preview Abstract] 

GP8.00007: Entropic Lattice Boltzmann Algorithms for Turbulence George Vahala , Jeffrey Yepez , Min Soe , Linda Vahala , Brian Keating , Jonathan Carter For turbulent flows in nontrivial geometry, the scaling of CFD codes (now necessarily nonpseudo spectral) quickly saturate with the number of PEs. By projecting into a lattice kinetic phase space, the turbulent dynamics are simpler and much easier to solve since the underlying kinetic equation has only local algebraic nonlinearities in the macroscopic variables with simple linear kinetic advection. To achieve arbitrary high Reynolds number, a discrete Htheorem constraint is imposed on the collision operator resulting in an entropic lattice Boltzmann (ELB) algorithm that is unconditionally stable and scales almost perfectly with PE's on any supercomputer architecture. At this mesoscopic level, there are various kinetic lattices (ELB27, ELB19, ELB15) which will recover the NavierStokes equation to leading order in the ChapmanEnskog asymptotics. We comment on the morphology of turbulence and its correlation to the rate of change of enstrophy as well as simulations on 1600$^{3}$ grids. [Preview Abstract] 

GP8.00008: Nonlinear Excitation of Damped Eigenmodes in GYRO Microturbulence Simulations David Hatch , Paul Terry , Bill Nevins Recent work has demonstrated that linearly damped eigenmodes can be nonlinearly excited to levels that significantly affect saturated turbulent transport. This has been shown in reduced CTEM and ITGlike fluid models [1]. We analyze microturbulence data from GYRO to discover which if any of these effects exist in comprehensive simulations. It has long been noted that the spectrum for ITGdriven turbulence peaks at wavenumbers well below the fastest growing wavenumbers. In addition, the growth rate of the fastest growing ITG mode is positive well beyond the range of significant fluctuation amplitude. We examine the possibility of energy dissipation through linearly damped modes as an explanation for these phenomena. We bound damped eigenmode excitation from energetic considerations, given growth rate spectra and energy spectra. We examine cross correlations spectrally and compare to quasilinear values. Comparisons with simpler fluid models are also undertaken. \newline \newline [1] P.W. Terry, D.A. Baver, and S. Gupta, Phys. Plasmas \textbf{13}, 022307 (2006) [Preview Abstract] 

GP8.00009: Exponential Frequency Spectrum in a Magnetized PlasmaUCLA Meixuan Shi , David Pace , James Maggs , George Morales The frequency spectrum of density and temperature fluctuations associated with a controlled, electron temperature filament in a magnetized plasma is investigated. A hot, narrow electrontemperature structure is generated from injection of a small, lowvoltage beam into the LAPDU device. Fluctuations develop after an initial quiescent period dominated by classical electron heat transport. Coherent structures associated with driftAlfven modes grow due to the electron temperature gradient, but eventually a broadband frequency spectrum emerges, which exhibits an exponential frequency dependence for frequencies less than a third of the ion cyclotron frequency. Similar spectra have been previously observed in totally different experimental situations, including in tokamak plasmas.. Using a variety of signal analysis techniques, it is found that the exponential frequency dependence arises from a series of individual, solitonlike pulses. The relationship of the width, occurrencefrequency and amplitude of individual pulses to the exponential spectral index is determined. The dependence of the formation and characteristics of the solitary pulses on heating power, and magnetic field is explored. [Preview Abstract] 

GP8.00010: Thermal Waves in a Magnetized Plasma David Pace , M. Shi , J.E. Maggs , G.J. Morales In recent years the topic of ``thermal waves'' has received considerable attention outside the plasma community. This peculiar phenomenon refers to the temperature fluctuations that arise when a system, described by a thermal diffusion equation, is subjected to an oscillating heat source. By measuring the propagation characteristics of the oscillatory temperature signals it is possible to determine the thermal conductivities of gases and solids to great precision. The present study uses observations of selfâ€“modulated temperature fluctuations arising in a thermal filament produced by a small, lowvoltage beam to study the behavior of thermal waves in a magnetized plasma. The beam is injected, at fixed voltage, into the large LAPDU device and, in the absence of selfmodulation, it creates a quiescent temperature filament 6 meters long and 0.5 cm diameter. When temperature modulations arise, axial and radial propagation of thermal waves are clearly detected. Comparison of the measured phase speeds to theoretical predictions, and to results of a transport code, show excellent agreement with the classical conductivities due to Coulomb collisions. This classical transport behavior has been independently verified in the absence of modulation. An assessment is made of the utility of a voltagemodulated beam source designed to diagnose the thermal conductivity of plasmas based on thermal waves. [Preview Abstract] 

GP8.00011: Basis function bispectral analysis in a cylindrical coordinate system D.A. Baver , P.W. Terry , G.R. Tynan , S.H. Mueller Bispectral analysis is a class of algorithms for inferring turbulence parameters using measured data to fit to a generic model equation. However, the model equations used in previous bispectral algorithms do not account for the geometry of actual plasma experiments. This can potentially produce spurious results, so an algorithm tailored to the geometry of a specific experiment is desirable. We present an algorithm adapted to the cylindrical coordinate system found in experiments such as CSDX. This algorithm uses an incomplete basis approximation for both linear and nonlinear terms. This approach is chosen because the linear eigenmodes cannot be known a priori since mode width depends on flow shear; the resulting coupling between assumed eigenmodes requires the calculation of an interaction matrix, which greatly increases data requirements. Applying a smoothness assumption reduces data requirements to acceptable levels, allowing the algorithm to operate on limited data sets. We will demonstrate tests of this algorithm on simulation data, and we will also apply the algorithm to experimental data from CSDX. Varying the model equations permits solutions for both single field and multiple field data, which can be compared to determine the importance of multifield effects. Work supported by USDOE. [Preview Abstract] 

GP8.00012: Investigation of electrostatic and magnetic structures at small scale in the edge region of RFX Roberto Cavazzana , Matteo Agostini , Paolo Scarin , Gianluigi Serianni A set of three threeaxial high frequency magnetic pickup coils has been recently added to the gas puffing imaging (GPI) diagnostic system installed on RFX. The fluctuations of Healpha emission from the puffed gas cloud extend in the range above 10 kHz up to several hundred kHz and have been found to be mainly linked to density fluctuations associated to electrostatic structures moving in the plasma edge. The signals collected with the new magnetic probes show a strong correlation of these density fluctuations with magnetic fluctuations in the same frequency range. The spatiotemporal phase and amplitude relation between magnetic and emission signals will be investigated, aimed at identifying the principal instability driving the electrostatic turbulence in the edge RFP region. [Preview Abstract] 

GP8.00013: Nonlinear Dynamics of Fluctuations and Convective Blobs in the Presence of Sheared Flows in a Magnetized Laboratory Plasma L. Yan , M. Gilmore , C. Watts , S. Xie It has been observed that some instabilities can be triggered by localized flows, both azimuthally and axially. It also has been demonstrated that the presence of sheared flows at the plasma edge is strongly correlated to the reduction of low frequency instabilities and associated crossfield transport. To investigate the details of how those instabilities interact with plasma flows, experiments are being conducted in the HELCAT (HELiconCAThode) linear device at UNM. HELCAT is a 4 m long device, with B $<$ 0.22 T, and peak heliconproduced densities, n $\sim $ 10$^{13}$ cm$^{3}$. Sheared ExB flows, generated via biased concentric rings, are utilized to modify the flow profile. Fluctuations and flux are monitored with probe arrays, and flows, both azimuthal and axial, are measured by a Mach probe. It is found that drift waves are present when RF power exceeds a pressuredependant threshold. Biasing can suppress the drift instability, while increased bias drives a new mode, believed to be KelvinHelmholtz. Parameters, such as RF power, gas pressure, bias voltage, and magnetic field, are investigated for their effects on plasma behavior. Experimental and analysis results will be presented. [Preview Abstract] 

GP8.00014: Observation of Chaos in a Magnetized Laboratory Plasma under the Influence of Variable Biasing S. Xie , C. Watts , M. Gilmore , L. Yan Ion saturation current fluctuation data from helicon plasmas in the linear HELCAT (HELiconCAThode) device under positive biasing (with respect to the vacuum chamber wall) of a set of concentric rings is analyzed. HELCAT is 4 meters long, 0.5 meter in diameter, with dual plasma sources (RF Helicon and NiBaO thermionic cathode), helicon plasma peak density $\sim$ 10$^{19}$ m$^{3}$, and magnetic field up to 0.22T. Analysis shows that the helicon plasma is in a weakly turbulent state caused by drift waves before positive biasing of the rings. When the bias voltage is increased, drift waves start to be suppressed, finally disappearing when the bias voltage is around 12 volts ($\sim$ 3kTe/e). At suppression, a phase plot shows a simple attractor. As the bias is further increased, period doubling bifurcations are observed, and simultaneously the plasma enters a chaotic state with correlation dimension 23. At higher bias, the plasma develops a new, intermittent, instability, which is believed to be a KelvinHelmholtz mode, and a continued increase of the correlation dimension to values greater than 3. [Preview Abstract] 

GP8.00015: On the Statistical Properties of the Turbulent Reynolds Stress Zheng Yan , George Tynan , Jonathan Yu , Chris Holland , Stefan Muller , Min Xu Statistical properties of the turbulent Reynolds stress has been studied on the CSDX linear device. The strongest power of the turbulent Reynolds stress is located near the maximal density gradient region, and the crossphase between the turbulent radial and azimuthal velocity fields determines the shape and the amplitude of the Reynolds stress, and hence the shear flow generation. The PDF of the turbulent ionsaturation current shows that density bursts are born in the vicinity of the shear layer. Joint PDF between the turbulent ionsaturation current, turbulent radial and azimuthal velocity fields and Reynolds stress are computed, as well as the timeaveraged vorticity fields, which allows the study of the relation between the formation of blobs of enhanced plasma density in the far edge region, the behavior of the Reynolds stress, its crossphase and crosscoherence, generation of bursty radially going azimuthal momentum transport events, and the formation of the largescale shear layer. [Preview Abstract] 

GP8.00016: Microturbulence, shear and burstiness in basic experimental plasmas S.H. Muller , C. Holland , G.R. Tynan , M. Xu , Z. Yan , J.H. Yu , A. Fasoli , I. Furno , B. Labit , M. Podesta We present basic experimental studies of the interplay between microturbulence, shear flow and plasma bursts. On the linear devices CSDX and LAPD, a shear layer (SL) is found to develop in the transition region between the core and edge plasma. Multitip Langmuirprobe (LP) measurements on CSDX support the idea that the effective Reynolds stress (RS) of microscopic fluctuations acts as a momentum transport mechanism, which sustains the shear layer. On LAPD, wall biasing is used to study the response of the RSSL system to an external momentum source. Both on CSDX and on the toroidal device TORPEX, radial plasma bursts are observed to occur intermittently. In both cases, the bursts are found to originate from large wave crests of a dominant coherent mode that is subject to a background sheared flow. On TORPEX, the distortion of wave crests leading to the detachment of blobs is directly visualized using an 86tip LP array. The dynamical and transport properties of these blobs are characterized quantitatively and striking similarities with tokamak observations are reported. These results suggest that gradientdriven drift turbulence can drive largescale shear flows which, in turn, mediate the birth of bursty events. [Preview Abstract] 

GP8.00017: Experimental Study of Nonlinear Energy Transfer in Frequency Domain Min Xu , Chris Holland , Stefan Muller , George Tynan , Zheng Yan , Jonathan Yu The transfer of turbulent energy between different fluctuation scales is of great interest to obtain an understanding of the development of turbulence and formation of turbulentdriven shear flows in magnetized plasmas. Under some conditions, different spatial scales can generally be associated with different frequency scales, and thus the study of turbulent energy transfer in the frequency domain is also of interest. Based on the turbulent plasma continuity and momentum equations, the nonlinear internal and kinetic energy transfer terms can be explicitly measured in experiment. First attempt aimed at measuring these energy transfer terms have been carried out by using a 9tip Langmuir probe array in the CSDX linear plasma device. Initial results from this work are reported in this poster. [Preview Abstract] 

GP8.00018: Fluctuations, turbulence and related transport in the TORPEX magnetised toroidal plasma Ambrogio Fasoli , Ahmed Diallo , Ivo Furno , Davoud Iraji , Benoit Labit , Gennady Plyushchev , Francesca Poli , Paolo Ricci , Christian Teiler , Stefan Muller , Mario Podesta' Progress in understanding fluctuations, turbulence and related transport in magnetized plasmas is achieved in TORPEX via highresolution measurements of plasma parameters and wave fields throughout the plasma crosssection. Electrostatic driftinterchange instabilities are characterized in terms of dispersion relation, driving mechanisms and development into turbulence. Measurements of density fluctuation time series across the plasma crosssection in a variety of plasma conditions reveal universal aspects such as a quadratic relation between skewness and kurtosis. Full spatiotemporal imaging of the electrostatic fluctuations is undertaken, using a multiple probe array or via conditional sampling of data obtained from movable probes. Blobs are observed to carry plasma from the core to the plasma edge. The blob generation and ejection are related to the a strongly sheared ExB flow. The blob effect on crossfield transport is investigated in details. Future research lines, such as active control of driftinterchange spectra using tunable antennas, optical turbulence imaging, and the study of the interaction of suprathermal ions with driftinterchange turbulence, will be discussed. [Preview Abstract] 

GP8.00019: Onsager Regression in phasespace resolved ion fluctuations. Fred Skiff Onsager regression is the hypothesis that there is no difference between a fluctuation and a linear excitation. It implies that there is a connection between certain correlation functions and the linear response function. We explore this connection by comparing phasespace resolved correlation functions for ion fluctuations to linear response functions for the ion response. The data come from twopoint correlation functions measured in a singly ionized Argon discharge plasma using laserinduced fluorescence. The experiments are performed in a plasma cylinder of density 10$^{9}$ cm$^{3}$ and a uniform magnetic field of 1kG. The LIF laser is aligned parallel to the magnetic field and two periscope detection systems are aligned to view points on the beam separated by a variable distance along the magnetic field. LIF measurements of fluctuations are not able to directly view the presence of particle discreteness because optical pumping and collisions make it improbable that there will be even one detected photon per metastable ion. Thus, all the crosscorrelation results have to do with collective effects (modes). Nevertheless, there is a kinetic ``freestreaming'' part that is a significant part of the fluctuations. Although it is not at all clear that a linear theory should apply to these fluctuations because nonlinear correlations are evident in the bicoherence, and there should be trapped particle effects, we find that the kinetic component also can be described by an impulse response function [Preview Abstract] 

GP8.00020: Application of fractional diffusion to model perturbative transport experiments in JET Diego delCastilloNegrete , Paola Mantica , Volker Naulin , J. Rassmussen Perturbative transport experiments follow the transient response of the plasma to externally applied small perturbations, e.g. plasma edge cooling and heating power modulation. These experiments provide time dependent information that can be used for testing models. JET experiments show an asymmetry between the relatively slow propagation of ICRH power modulation perturbations and the fast propagation of edge cold pulses [1]. Previous attempts to model these experiments have not been successful. In particular, while local models are able to reproduce the modulation data, they underestimate the speed of the pulses. Here we show that a nonlocal transport model based on the use of fractional diffusion operators [2] is able to describe the JET experiments. The model reproduces the amplitude and phase profiles of the modulation data and, most importantly, it gives pulse propagation speeds consistent with the experiment. \newline [1] P.Mantica et al.,Proc.19th Intern. Conf. on Fusion Energy, Lyon [IAEA,Vienna,2002] EX/P104. \newline [2] D. delCastilloNegrete, Phys. Plasmas 13, 082308 (2006). [Preview Abstract] 

GP8.00021: Numerical simulation of ETG fluid model in uniformly sheared $E\times B$ velocity Juhyung Kim , George Chagelishvili , Wendell Horton We construct an ETG fluid model (Horton et al. Nucl. Fusion 45, 2005) with uniformly sheared $E\times B$ velocity. The fluid model is implemented based on the pseudospectral method. The linear dynamics calculation is performed in the moving frame, where the periodicity is assumed in the Lagrangian coordinate, and the nonlinear term is implemented in the traditional Fourier transformation (Lithwick, arXiv:astroph/0702046, 2007). This method enables us to investigate the nonlinear dynamics in sheared flow at a typical growth rate $\gamma > \omega_E$, for which we observed longlived vortex structures when no instability is included (Kim et al. Phys. Plasma 13, 2304, 2006). We will report the spectrum for the electrostatic potential and the temperature. [Preview Abstract] 

GP8.00022: Feedback of largescale fluctuations on driving noise ChangBae Kim The socalled predatorprey model that describes the dynamics of largescale fluctuations and shortscale turbulence is studied by substituting the turbulence with noise. It is known that largescale fluctuations in the plasma driven by the paritynonconserving (PNC) noise become unstable if the relative level of the PNC noise is over a threshold $\alpha_{\mbox{c}} = log R/R$, where $R$ is the ratio of the largest to the smallest scales. The PNC noise may model such shortscale turbulence as the drift waves of short wave lengths. As a result, largescale fluctuations emerge and grow in time. If this is an action of the turbulence on large scales, the reaction of the largescale fluctuations on the turbulence is to lower the effective strength of the PNC noise below the threshold in order to make the plasma reach stationary state. This feedback is worked out by renormalizing the noise up to the lowest nontrivial order. It will be shown that the isotropic part of the noise is enhanced while the PNC piece being unchanged and that, as a result, the relative strength of the PNC to the isotropic noise is smaller than $\alpha_{\mbox{c}}$. [Preview Abstract] 

GP8.00023: IonAcoustic Turbulence in ECCDdriven TCV plasmas Christian Schlatter , Basil P. Duval , Alexander N. Karpushov , Timothy P. Goodman Strong X2 electroncyclotron current drive in the Tokamak \`{a} Configuration Variable (TCV) is typically accompanied by rapid (noncollisional) and strong bulk ion heating. Neutral Particle Analyzer (NPA) measurements of the ion properties transverse to the toroidal magnetic field indicate suprathermal ion populations comprising more than 20 \% of the ions with temperatures up to several keV [1]. Whereas the RF power is deposited in the very plasma center, fast ions are found almost throughout the plasma column. Theoretical calculations of the EC driven current are combined with experimental estimations of the relativistic electron drift velocities using oblique ECE measurements in order to assess the conditions to trigger ionacoustic turbulence, which is believed to be responsible for the ion heating [2]. An attempt of numerically modeling the experimentally observed level of turbulence saturation in the frame of quasilinear theory will be presented.\newline References: [1] A. N. Karpushov et al., 33rd EPS Conference on Plasma Phys. Rome (2006); [2] Ch. Schlatter et al., dito. [Preview Abstract] 

GP8.00024: FACETS: Towards a flexible infrastructure for building coupled transport models Alexander Pletzer , Ammar Hakim , Mahmood Miah , Srinath Vadlamani , Johan Carlsson , Scott Kruger , John R. Cary , Alexei Pankin The Framework Application for CoreEdge Transport Simulation (FACETS) is a project aimed at providing an infrastructure for building transport codes capable of exploiting massively parallel architectures. FACETS is driven by the requirement to simulate $>100$s long discharges in ITER, with time scales ranging from $\mu$s for plasma wallinteractions to 1s for the slow evolution equilibrium profiles. Critical to FACETS will be the capability to couple physics modules (transport models, neutral beam sources, equilibrium, ...) in flexible and efficient way. We report on the progress of building such an infrastructure. FACETS introduces the concept of components and updaters. Components hold data such as profiles while updaters act on these data, for example by timeadvancing fields. As an example, we show how to create building block components and updaters for a core transport code, which uses an implicit algorithm based on the block hypersecant method (BHS solver) to advance ion/electron densities and temperatures. Fluxes are computed by FMCFM's uniform interface to the GLF23/MMM95 reduced transport models. [Preview Abstract] 

GP8.00025: Transport in twofluid MHD turbulence Ellen Kumar , E. Kim We present a theory of transport of magnetic flux and momentum in two fluid 3D reduced magnetohydrodynamic (MHD) turbulence. By including the effects of shear flows and magnetic fields consistently, we show that kinetic Alfven waves can help weaken the quenching in turbulent transport of a strong magnetic field $B_0$ found in single fluid MHD turbulence, leading to turbulent diffusivity $\eta_T \propto (\eta/\Omega)^{1/3}B_0^{ 2}$. Here, $\eta$ and $\Omega$ are Ohmic diffusivity and shearing rate of the shear flow. Momentum transport is diffusive, with the value of eddy viscosity larger than that in single fluid MHD turbulence. The effects of drift waves are found to be weaker. Implications for the instability of shear flows are discussed. [Preview Abstract] 

GP8.00026: Turbulent resistivity in wavy 2D MHD turbulence Shane Keating , Patrick Diamond The theory of `wavy' MHD turbulence in 2D is presented. The goal is to explore the theory of quenching of turbulent resistivity in a regime for which the mean field theory can be rigorously constructed at large magnetic Reynolds number Rm. We extend the simple 2D problem to include body forces such as buoyancy or the Coriolis force, which convert large scale eddys into weakly interacting dispersive waves. The turbulence driven spatial flux of magnetic potential is calculated to fourth order in wave slope. Remarkably, adding an additional restoring force to the already tightly constrained system of high Rm MHD turbulence in 2D can actually increase turbulent resistivity, by admitting a spatial flux of magnetic potential which is not quenched at large Rm, although it is restricted by the conditions of applicability of weak turbulence theory. [Preview Abstract] 

GP8.00027: Numerical modeling of anisotropic 3D DriftAlfven turbulence J.C. Perez , Stanislav Boldyrev We present results from extensive numerical simulations of steady state DriftAlfven turbulence in the presence of a strong guide field. We use a turbulence model based on equations originally derived by Hazeltine as an extension of the Reduced MHD model (RMHD). The model includes three dynamical fields, potential, magnetic flux, density and allows for the existence of a background density gradient that drives large scale electromagnetic driftwave instabilities. Previous numerical simulations of this type of models have been mostly restricted to 2D or pseudo 2D simulations in the limit of vanishing $k_\$, which restrict the turbulence cascade to the fieldperpendicular plane. However, recent work in MHD turbulence have shown that the parallel dynamics can play a key role in anisotropic turbulent cascades. In this work we present fully 3D simulations of strong DriftAlfven turbulence in a rectangular box that reflects the anisotropy of the turbulence imposed by the guide field. Simulations are benchmarked against stateoftheart simulations of MHD turbulence at large scales and are used to investigate the energy spectrum as the turbulence reaches the ion sound radius, where the Shear Alfven makes the transition to a Kinetic Alfven wave. [Preview Abstract] 

GP8.00028: Numerical Simulations of Strong MHD Turbulence J. Mason , F. Cattaneo , S. Boldyrev Magnetohydrodynamic turbulence plays an important role in many astrophysical phenomena, including the solar wind, angular momentum transport in accretion disks and interstellar scintillation. Despite more than 40 years of investigations much within the subject remains controversial. Recently a new theory has been developed [1, 2]. It predicts a scaledependent dynamic alignment between the velocity and magnetic fluctuations and leads to the fieldperpendicular energy spectrum $E(k)\propto k^{3/2}$. Here we discuss this new theory and present the results of a series of numerical tests. Quantities measured include the alignment angle, the spectrum and the third order structure functions for which the exact relations due to Politano {\&} Pouquet [3] hold. \newline [1] Boldyrev, S. (2005) Astrophys. J. 626, L37. \newline [2] Boldyrev, S. (2006) Phys. Rev. Lett. 96, 115002. \newline [3] Politano, H. {\&} Pouquet, A. (1998) Geophys. Res. Lett. 25, 273. [Preview Abstract] 

GP8.00029: A laboratory study of a nonlinear interaction between copropagating kinetic Alfven waves B.T. Brugman , T.A. Carter , D.W. Auerbach , S.C. Cowley A study of a beatwave interaction between kinetic Alfv\'{e}n waves has been performed in the Large Plasma Device (LAPD) at UCLA\footnote{T.A. Carter, {\itshape et al.}, PRL 96, 155001 (2006)}. Two copropagating waves are observed to beat together and drive a strong lowfrequency mode which has a normalized amplitude comparable to or exceeding that of the two incident Alfv\'{e}n waves ($\delta n/n > \delta B/B \sim 1\%$). This lowfrequency mode then interacts with the incident Alfv\'{e}n waves, leading to strong sideband generation. The phase velocity beatdriven mode is consistent with threewave matching rules, but is not consistent with any linear wave. A nonlinear Braginskii fluid model of the interaction predicts that the beatdriven wave is a quasimode that is really an offresonance Alfv\'{e}n wave. The quasimode is driven by nonlinear crossfield convection which is effective due to the short perpendicular scale of the incident Alfv\'{e}n waves ($k_\perp \gg k_\parallel$). The model predicts a sizable amplitude for the beatdriven response, consistent with experimental observations. Details of experimental observations and the nonlinear model will be presented. [Preview Abstract] 

GP8.00030: Heating and background plasma modification associated with large amplitude kinetic Alfv\'{e}n wave launch in LAPD T.A. Carter , D.W. Auerbach , B.T. Brugman Large amplitude kinetic Alfv\'{e}n waves ($\delta B/B \sim 1\% > k_\parallel/k_\perp$) are generated in the Large Plasma Device (LAPD) at UCLA using loop antennas. Substantial electron heating is observed, localized to the wave current channels. The Poynting flux associated with the Alfv\'{e}n waves is substantial and the observed heating may be at least in part due to collisional and Landau damping of these waves. However, heating by antenna near inductive electric fields may also be responsible for the observations. A discussion of both possibilities will be presented, including measurements of near fields of the antenna. The heating structures the background plasma and results in the excitation of driftAlfv\'{e}n waves. These drift waves then interact with the incident Alfv\'{e}n wave, causing sideband generation which results in a nearly broadband state at high wave power. This process may represent an alternate mechanism by which unidirectional kinetic Alfv\'{e}n waves can nonlinearly generate a turbulent spectrum. In addition to electron heating, evidence for background density modification and electron acceleration is observed and will be presented. [Preview Abstract] 

GP8.00031: Studies of nonlinear interactions between counterpropagating Alfv\'{e}n waves in the LAPD D.W. Auerbach , J.C. Perez , T.A. Carter , S. Boldyrev From a weak turbulence point of view, nonlinear interactions between shear Alfv\'{e}n waves are fundamental to the energy cascade in lowfrequency magnetic turbulence. We report here on an experimental study of counterpropagating Alfv\'{e}n wave interactions in the Large Plasma Device (LAPD) at UCLA. Colliding, orthogonally polarized kinetic Alfv\'{e}n waves are generated by two antennae, separated by ~5m along the guide magnetic field. Magnetic field and langmuir probes record plasma behavior between the antennae. When each antenna is operated separately, linearly polarized Alfv\'{e}n waves propagate in opposite directions along the guide field. When two antennae simultaneously excite counter propagating waves, we observe multiple side bands in the frequency domain, whose amplitude scales quadratically with wave amplitude. In the spatial domain we observe nonlinear superposition in the 2D structure of the waves and spectral broadening in the perpendicular wavenumber spectrum. This indicates the presence of nonlinear interaction of the counter propagating Alfv\'{e}n waves, and opens the possiblity to investigate Alfv\'{e}nic plasma turbulence in controlled and reproducible laboratory experiments. [Preview Abstract] 

GP8.00032: Effect of ion composition on magnetosonic waves Mieko Toida , Hiroyuki Higashino , Yukiharu Ohsawa The propagation of the two kinds of fast magnetosonic waves, i.e., low and highfrequency modes, in a twoionspecies plasma is studied theoretically and numerically. It is analytically found that the KdV equation for the lowfrequency mode is valid for amplitudes $\varepsilon < 2 \Delta_{\omega}$, where $\Delta_{\omega} = (\omega_{+0}  \omega_{ {\rm r}})/ \omega_{+0}$ with $\omega_{+0}$ the cutoff frequency of the highfrequency mode and $\omega_{{\rm r}}$ the resonance frequency of the lowfrequency mode; $\Delta_{\omega}$ is given as a function of the density ratio and cyclotron frequency ratio of two ion species. It is then suggested that nonlinear coupling between the two modes can occur if $\varepsilon > 2 \Delta_{\omega}$. With electromagnetic particle simulations, the evolution of the low and highfrequencymode pulses is investigated for various density and cyclotron frequency ratios and is compared with theoretical predictions. In particular, it is shown that highfrequencymode pulses are generated from a longwavelength lowfrequencymode pulse if its amplitude $\varepsilon$ exceeds $2 \Delta_{\omega}$. [Preview Abstract] 

GP8.00033: A nonlinear 4wave resonant model for nonperturbative fast ion interactions with Alfv\'{e}nic modes in burning plasmas Fulvio Zonca , Liu Chen We adopt the 4wave modulation interaction model, introduced by Chen et al [1] for analyzing modulational instabilities of the radial envelope of Ion Temperature Gradient driven modes in toroidal geometry, extending it to the modulations on the fast particle distribution function due to nonlinear Alfv\'{e}nic mode dynamics, as proposed in Ref. [2]. In the case where the waveparticle interactions are nonperturbative and strongly influence the mode evolution, as in the case of Energetic Particle Modes (EPM) [3], radial distortions (redistributions) of the fast ion source dominate the mode nonlinear dynamics. In this work, we show that the resonant particle motion is secular with a timescale inversely proportional to the mode amplitude [4] and that the time evolution of the EPM radial envelope can be cast into the form of a nonlinear Schr\"{o}dinger equation a la GinzburgLandau [5]. \newline \newline [1] L. Chen et al, Phys. Plasmas {\bf 7} 3129 (2000) \newline [2] F. Zonca et al, Theory of Fusion Plasmas (Bologna: SIF) 17 (2000) \newline [3] L. Chen, Phys. \ Plasmas {\bf 1}, 1519 (1994).\newline [4] F. Zonca et al, Nucl. Fusion {\bf 45} 477 (2005) \newline [5] F. Zonca et al, Plasma Phys. Contr. Fusion {\bf 48} B15 (2006) [Preview Abstract] 

GP8.00034: Positive and negative effective mass of relativistic particles in oscillatory and static fields I.Y. Dodin , N.J. Fisch A relativistic particle oscillating in highfrequency and/or static fields can be treated as a quasiparticle with an effective mass $m_{\rm eff}$, which depends on the local parameters of the fields. Both ponderomotive and $\mu\nabla\kern 1pt B$ forces, as well as magnetic drifts, are derived from $m_{\rm eff}=m_{\rm eff} (\mathbf{r}, \dot{\mathbf{r}})$, $\mathbf{r}$ being the coordinate of the oscillation center. The effective mass is not necessarily positive; thus, if a (weak) external force is applied, acceleration in the direction opposite to this force is possible. As an example, adiabatic average dynamics with $m_{\rm eff}>0$ and $m_{\rm eff}<0$ is demonstrated for a wavedriven particle in a dc magnetic field. Different energy states are realized in this case, yielding up to three branches of $m_{\rm eff}$ for a given magnetic moment and parallel velocity. [Preview Abstract] 

GP8.00035: A water bag theory of autoresonant BGK modes Pavel Khain , Lazar Friedland The adiabatic water bag theory describing formation and passage through phasespace of driven, continuously phaselocked (autoresonant) coherent structures in plasmas [L. Friedland et al., Phys. Rev. Lett. \textbf{96}, 225001 (2006)] and of the associated BGK modes is developed. The phaselocking is achieved by using a chirped frequency ponderomotive drive, passing through kinetic Cherenkovtype resonances. The theory uses the adiabatic invariants (conserved actions of limiting trajectories) in the problem and, for a flattop initial distribution of the electrons, reduces the calculation of the selffield of the driven BGK mode to solution of a few algebraic equations. The adiabatic multiwater bag extension of the theory for applications to autoresonant BGK structures with more general initial distributions is suggested. The results of the theories are in a very good agreement with numerical simulations. [Preview Abstract] 

GP8.00036: Nonlinear Wave and Soliton Excitations in Coasting Charged Particle Beams Using a Kinetic gFactor Model Ronald Davidson , Edward Startsev , Hong Qin Making use of a onedimensional kinetic model based on the VlasovMaxwell equations, this paper describes nonlinear wave and soliton excitations in coasting charged particle beams. The kinetic description is based on the recentlydeveloped gfactor model [1] that incorporates selfconsistently the effects of transverse density profile shape at moderate beam intensities. The nonlinear evolution of wave and soliton excitations is examined [2] for disturbances both moving faster and moving slower than the sound speed, incorporating the important effects of wave dispersion. Analytical solutions are obtained for nonlinear traveling wave pulses, and the results of nonlinear perturabtive particleincell simulations are presented that describe the stability properties and longtime evolution. \\ (1) R. C. Davidson and E. A. Startsev, Phys. Rev. ST Accel. Beams 7, 024401 (2004).\\ (2) R. C. Davidson, E. A. Startsev and H. Qin, Proceedings of the 2007 Particle Accelerator Conference, in press (2007) [Preview Abstract] 

GP8.00037: KEEN Waves, Conformal Invariance and Connections to 2D Euler Turbulence Theory Bedros Afeyan , Mathieu CharbonneauLefort KEEN Waves are a manifestation of nonstationary, selforganized, nonlinear, kinetic states shown to be prevalent in coherently driven plasmas [1]. We will examine statistical mechanical and conformal invariance in critical phenomena based arguments that try to explain the existence and salient features of such states as well as indicating mechanisms by which turbulence and disorder are beaten in order to generate them. The connection with 2D Euler turbulence [2], multifractal characterizations of critical phase transitions and SchrammLoewner evolutions will be given. \newline [1] B. Afeyan, et al., Kinetic Electrostatic Electron Nonlinear (KEEN) Waves and their interactions driven by the ponderomotive force of crossing laser beams, Proc. IFSA, (Inertial Fusion Sciences and Applications 2003, Monterey, CA), B. Hammel, D. Meyerhofer, J. MeyerterVehn and H. Azechi, editors, 213, American Nuclear Society, 2004. \newline [2] Bernard, et al., Nature Phys. 2, 124 (2006) and references therein. [Preview Abstract] 

GP8.00038: Destruction of transport barriers in a nontwist map model of a reversed magnetic shear tokamak with an ergodic magnetic limiter Alexander Wurm Recently, the magnetic field line structure of reversed magnetic shear tokamaks has been modeled by an area preserving nontwist map that includes nonintegrable perturbations describing ergodic magnetic limiters.[1] An expansion around the equilibrium shearless curve (corresponding to the main transport barrier in the model) showed that the map is locally equivalent to the standard nontwist map with an additional perturbation due to the limiter.[2] I report results of the investigation into the effect of the perturbation on the resilience of the shearless curve. \newline \newline [1] K. Ullmann and I.L. Caldas, Chaos, Solitons and Fractals, {\bf 11}, 2129 (2000).\newline [2] J.S.E. Portela, I.L. Caldas, R.L. Viana, and P.J. Morrison, to appear in J. Bifur. Chaos (2007). [Preview Abstract] 

GP8.00039: FAST IGNITION AND LASERPLASMA INTERACTIONS 

GP8.00040: Hydrodynamic assembly for Fast Ignition Max Tabak , Daniel Clark , Richard Town , Stephen Hatchett We present directly and indirectly driven implosion designs for Fast Ignition. Directly driven designs using various laser illumination wavelengths are described. We compare these designs with simple hydrodynamic efficiency models. Capsules illuminated with less than 1 MJ of light with perfect zooming at low intensity and low contrast ratio in power can assemble 4 mg of fuel to column density in excess of 3 g/cm$^{2}$. We contrast these designs with more optimized designs that lead to Guderleystyle self similar implosions. Indirectly driven capsules absorbing 75 kJ of xrays can assemble 0.7 mg to column density 2.7 g/cm$^{2}$ in 1D simulations. We describe 2D simulations including both capsules and attached cones driven by radiation. We describe issues in assembling fuel near the cone tip and cone disruption. [Preview Abstract] 

GP8.00041: Fast Ignition with UltraHigh Intensity Lasers John Tonge , M. Tzoufras , F.S. Tsung , W.B. Mori , C. Ren , M. Marti , L. Silva Energy transport within overdense plasma with a fast ignition target is explored by examining the interaction of different intensity ignition lasers with a 50 $\mu$ radius target using twodimensional ParticleInCell simulation. In fast ignition schemes the ignition energy must be delivered to a small region ($\sim$ 20 $\mu$ in radius) of dense plasma within the target in order to create a localized region where fusion occurs. The electron stopping length in the core and the energy spectrum of the ignition electrons determines the depth of this region. This depth is sensitive to the spectrum of the energy flux of fast electrons generated as a function of laser intensity at the critical surface. Coupled with current assumptions of the spectrum of electrons generated by high intensity lasers this limits ignition laser intensity to 5x10$^{19}$ W/cm$^{2}$. Our simulations show that the peak energy flux of the ignition electrons is significantly lowered as the electrons traverse the collisionless plasma from the critical density surface of the plasma to the high density target core where ignition occurs. This allows higher intensity lasers to be used thus delivering power to a narrower region. In addition we find that a higher percentage of the ignition lasers energy is delivered to the core with the higher intensity laser. [Preview Abstract] 

GP8.00042: Observations of the Effect of ErHydride Targets on the Conversion Efficiency to Laser Accelerated Protons D.T. Offermann , L.D. Van Woerkom , A.J. Mackinnon , Y. Ping , A.G. MacPhee , N. Shen , M.E. Foord , J.J. Sanchez , C.D. Chen For Fast Ignition Inertial Confinement Fusion using proton beams, methods must be developed to improve the efficiency in converting laser energy incident on thin foils to the accelerated proton beam from the foil's rear surface. Simulations suggest that targets with a heavy element hydride, such as ErH$_3$, on the rear surface will increase the conversion efficiency by a factor of two relative to proton signals originating from hydrocarbon contaminants. Using the Callisto Laser, at LLNL ((8J, 5$\times10^{19}$ W/cm$^2$)) we have compared proton beams originating from contaminant layers on Gold foil targets with beams from Gold targets coated with ErH$_3$. Contaminants were removed using an ArIon etching beam. Data was collected using radiochromic film and an ion spectrometer. [Preview Abstract] 

GP8.00043: Proton Focusing in a FI Target Compatible Configuration R.B. Stephens , A.J. MacKinnon , S.P. Hatchett , M.H. Key , B.F. Lasinski , B. Langdon , P.K. Patel , M. Foord , M. Tabak , R.P.J. Town , S.C. Wilks , M.S. Wei , F. Beg , S. Chen , R.R. Freeman , J.A. King , J. Pasley , K.U. Akli , D. Clark , L. Van Woerkom , D. Hey FI targets that use lasergenerated proton beams for ignition must protect the protongenerating surface from the imploding shell. The protective case surrounding the surface has the potential to change the ion production efficiency and its focus. We have explored these effects in recent experiments on the Titan laser with a focusing surface embedded in a washer. The proton beam was recorded with a radiochromic film stack. The shadow of a 1000~lpi SEM grid mounted beyond the nominal focus of the proton surface ($\sim $1.8x radius of curvature) allowed the calculation of focal point position and size as a function of proton energy. Simultaneous XUV measurements of the heated grid give total proton energy deposited in the grid. Experimental results will be compared to simulations. [Preview Abstract] 

GP8.00044: Capsule Design Studies for MidZ IonDriven Fast Ignition B.J. Albright , M.J. Schmitt , G.E. Cragg , J.C. Fern\'andez , I.L. Tregillis , N.M. Hoffman , G.R. Magelssen , B.M. Hegelich , K.A. Flippo Ion fast ignition (IFI) is an approach to fast ignition inertial confinement fusion where an energetic ion beam is used to ignite a hot spot. Recent work at LANL and elsewhere has shown that energetic midZ ion beams can be made when one directs a high intensity shortpulse laser onto a target foil cleaned to remove impurities. Use of such midZ ion beams in IFI may have advantages over other approaches to fast ignition. In this presentation, preliminary capsule designs for midZ IFI are assessed. These designs comprise a DT gas pocket, a DT ice fuel layer, and a lowZ ablator. Dependence of gain with beam parameters will be shown and the viability of this approach to fast ignition will be discussed. [Preview Abstract] 

GP8.00045: Liquid Cryogenic Target Development for Fast Ignition* D.L. Hanson , C. Russell , R.A. Vesey , D.G. Schroen , J.L. Taylor , C.A. Back , D. Steinman , A. Nikroo , J.L. Kaae , E. Giraldez , R.R. Johnston , K. Youngman As an alternative to foamstabilized cryogenic solid DT fuel layers for indirectdrive fast ignitor targets, which will tend to $\beta $layer to a nonuniform distribution in a reentrant cone geometry [1], we are investigating hemispherical cryogenic fast ignition capsules with a liquid fuel layer confined between a thick outer ablator shell and a thin inner shell [2]. The shape and surface quality of the fuel layer is determined entirely by the characteristics of the bounding shells. In the present design, structural support for the thin (4.5 um) hemispherical GDP inner shell is provided by a mounting ring. Fabrication of stronger thin Be hemishells is also being investigated. Technology issues for liquid cryogenic fuel capsule development and progress toward demonstration of a working target will be presented. \newline [1] J.K. Hoffer \textit{et al.}, Fusion Sci. Technol. \textbf{50}, 15 (2006). \newline [2] D.L. Hanson \textit{et al.}, Fusion Sci. Technol. \textbf{49}, 500 (2006). \newline \textbf{*}Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DEAC0494AL85000. [Preview Abstract] 

GP8.00046: PIC simulations of energetic electron transport in fast ignition Xianglong Kong , Rui Yan , Chuang Ren Transport of an energetic electron beam in a plasma is studied via PIC simulations with beamplasma parameters and boundary conditions relevant to fast ignition. This system is subject to currentfilamentation and twostream instabilities [Tonge, PhD thesis (2002), Bret, Firpo, and Deutsch, PRE, 70:046401 (2004)]. The simulations show that the current filaments resulting from the instabilities do not merge into a single filament as in the previous 2D simulations excluding the twostream instability [Lee and Lampe, PRL, 31:1390 (1971)]. The effects of ions and boundary conditions on the current filamenting and merging will also be presented. [Preview Abstract] 

GP8.00047: PIC simulations of energetic electron generation from laserplasma interactions Rui Yan , Gang Li , Chuang Ren Energetic electron generation from laserplasma interactions is important to inertial confinement fusion in many ways. Using particleincell (PIC) simulations we study the energetic electrons generation from Raman/twoplasmondecay instabilities near the 1/4critical surface. The possibility of target preheating from these electrons will be examined for the Omega laser parameters. We also study the energetic electron generation in the parameter regime relevant to fast ignition. Both 2D and 3D simulations are carried out to study different electron acceleration mechanisms near the laserplasma interface between linearlypolarized and circularlypolarized lasers. Energetic electron conversion efficiency and angular spread will be compared for the two polarizations. [Preview Abstract] 

GP8.00048: Laser channeling in mmscale underdense plasmas of fast ignition C. Ren , G. Li , R. Yan , T.L. Wang , J. Tonge , W.B. Mori Two dimensional particleincell simulations show that laser channeling in mmscale underdense plasmas is a highly nonlinear and dynamic process involving laser selffocusing and filamentation, channel expansion through ponderomotive blowout and high mach number shock waves, plasma density snowplowing, laser hosing, and channel bifurcation and merging. The channeling speed is much less than the laser linear group velocity. The simulations find that the channeling time $T_{c}$ and the total required energy $E_{c}$ to reach the critical surface scale with the laser intensity $I$ as $T_{c}$\textit{$\sim $I}$^{0.64}$ and $E_{c}$\textit{$\sim $I}$^{0.36}$. The scaling shows that lowintensity channeling pulses are preferred to minimize the required pulse energy but with an estimated lower bound on the intensity of \textit{I$\approx $4$\times $10}$^{18 }$W/cm$^{2}$ if the channel is to be established within 100ps. These results will also be compared with those from smaller scale 3D simulations. [Preview Abstract] 

GP8.00049: Hot electron energy coupling in coneguiding fast ignition Brian Chrisman , Yasuhiko Sentoku , Andreas Kemp , Thomas Cowan The Fast Ignition experiment relies on core ion heating due to laserplasma interactions. Potential underlying mechanisms for core ion heating include field instabilities, coronal ion wave incidence, and collisional coupling of energetic electrons accelerated from the coronal plasma.Previously demonstrated results show that after preplasma has been swept away, the ultraintense laser interacts with a steep density gradient, producing low energy hot electrons which are capable of penetrating and interacting with the high density core through collisional processes.Resolving known relevant physics in integrated 2D PIC simulations of a representative Fast Ignition experiment, simulation results are provided detailing the dependence of comprehensive core heating upon laser intensity. [Preview Abstract] 

GP8.00050: Saturation and LongTime Behavior of Weibel Instability and Electron Beam Transport in Dense Plasmas Oleg Polomarov , Ge Wange , Gennady Shvets , Adam Sefkow , Igor Kaganovich The propagation of electron beams in ambient plasma is considered analytically and numerically. For analytical treatment the twofluid hydrodynamics for beam and plasma electrons is used. Two numerical approaches are used: the reduced description [PoP, 14, 043103 (2007)] (in which the beam is modeled by particles and the plasma is an electron fluid) and the LSP PIC simulations. The detailed analysis of linear/nonlinear stages and the saturation of the Weibel filamentation instability is presented and the instability longterm nonlinear behavior is emphasized. For example, it is discovered that the filament formation and merger can lead to the growth as well as the decrease of the magnetic energy for sub/superalfvenik filaments. The plausible final state to which the Weibel instability evolves for large times is presented. Also, the peculiarities of 1D, 2D and 3D spatial behavior of the Weibel and electrostatic twostream instabilities of the relativistic electron beam propagating in constant density as well as in the steep gradient background plasmas (the Fast Ignition case) are considered. [Preview Abstract] 

GP8.00051: The effect of laser intensity on fast electron beam divergence in solid density plasmas V.M. Ovchinnikov , L. Van Woerkom , R.R. Freeman , J.S. Green , R.G. Evans , R. Heathcote , K.L. Lancaster , P.A. Norreys , K.U. Akli , M.H. Key , A.J. MacKinnon , A.G. MacPhee , F.N. Beg , J.A. King , T. Ma , R. Stephens , C. Bellei , Z. Najmudin , J. Waugh , H. Azechi , P. Nilson , W. Theobald , N.C. Lopes , R. Onofrei , J.R. Davies Metal foil targets were irradiated with 1 $\mu m$ wavelength ($\lambda )$ laser pulses of 5 ps duration and focused intensities up to $4\times 10^{19}Wcm^{2}$, giving values of both $I\lambda ^2$ and pulse duration comparable to those required for fast ignition inertial fusion. The divergence of the electrons accelerated into the target was measured using spatially resolved Xray $K_\alpha $emission and from transverse probing of the plasma formed on the back of the foils. Comparison of the divergence with other published data will be presented along with 2D PIC simulations. Supported by DOE grants DEFG0205ER54834, DEFG0200ER54606, and W7405Eng48 and STFC (UK). [Preview Abstract] 

GP8.00052: Measurement of Hot Electron Spatial Distribution Under the Presence of Laser Light Selffocusing in Overdense Plasmas Tsuyoshi Tanimoto , Kazuo A. Tanaka , Anle Lei , Toshinori Yabuuchi , Hideaki Habara , Kiminori Kondo , Ryousuke Kodama , Kunioki Mima In fast ignition (FI) scheme, ultra intense laser (UIL) pulse irradiates an imploded plasma core in order for fast heating via hot electrons generated in laserplasma interactions. Two important issues are the propagation of forward directed hot electron in the plasma and the spatial divergence of hot electrons. We measured the spatial distribution of hot electrons with different plasma density profiles when UIL pulse creates laser selffocused plasma channel in preformed plasma. When the selffocusing occurred, the hot electron number increased and the spatial distribution of hot electrons appeared more collimated . These hot electron distributions may be preferred for a high efficiency core heating in FI scheme. [Preview Abstract] 

GP8.00053: Simulation Studies on Fast Heating for FIREXI project Tomoyuki Johzaki , Hideo Nagatomo , Hitoshi Sakagami , Tatsufumi Nakamura , Atsushi Sunahara , Yasuyuki Nakao , Kunioki Mima At the fast ignition integrated experiments for coneguided CD targets with GekkoXII+PW laser systems [1], the efficient heating of imploded cores ($\sim $800eV) was demonstrated. As the next step, FIREX (Fast Ignition Realization EXperiment) project [2] has been started. In the phase I (FIREXI), a foamcryogenic DT target is imploded by the GekkoXII laser operated with higher energy mode and the imploded core is heated by the 10kJ LFEX laser. The goal of FIREXI is the core heating up to ion temperature of $\sim $5keV. From the previous experiments, the heating laser energy and the fuel material are different in FIREXI. In the present study, on the basis of core heating simulations for imploded core plasmas, where the core heating is treated with a simple heating model and the FokkerPlanck transport model, we evaluate those effects and show the requirement for achieving 5keV heating. \newline [1] R. Kodama, et al., Nature 418, 933 (2002). \newline [2] K. Mima, Annual Progress Rep. 2001 (Institute of Laser Engineering, Osaka University, 2001) p.1. [Preview Abstract] 

GP8.00054: Optimization of Nonspherical Implosion for Fast Ignition Hideo Nagatomo , Tomoyuki Johzaki , Tatsufumi Nakamura , Atsushi Sunahara , Hitoshi Sakagami , Kunioki Mima We have been studied the formation of highdensity and higharealdensity core plasma in coneguided nonspherical implosion for Fast Ignition. Sophisticated target designs are required, in which not only the target structure and laser pulse shape but also the detail specifications of the high density fuel core plasma for the high heating efficiency. Recently, we started the target design for the highdensity better configuration of core plasma for heating in realistic conditions using 2D radiation hydrodynamic code. Some sophisticated ideas, such as, a slow implosion for high density, high areal density concept [1] are taken account into. This concept is based on the 1D implosion and 2D effect caused by the guiding cone can not be ignored. Therefore, we have investigated the effect numerically. Also, the robustness over the hydrodynamic instabilities is studied. In this paper, these results are introduced and the best target design concept will be proposed, especially for FIREXI experiment. \newline [1] R. Betti et al., PoP (2005). [Preview Abstract] 

GP8.00055: Partial degeneracy effects in the stopping of relativistic electrons in supercompressed DT fuels Konstantin Starikov , Claude Deutsch The effects of supercompressed and partially degenerate electron fluid on projectile energy loss of femtolaser Produced relativistic electrons (REB) in the MeV energy range are investigated.Partial degeneracy is shown to effect Significantly the REB stopping power for 0.2 $<$ Theta=T/Tf $<$ 1 while its variations with beam energy appear much less Thetadependent.The latter exhibit a characteristic Vlike shape at any target electron density and Theta value. [Preview Abstract] 

GP8.00056: Measurements of Bremsstrahlung and Kshell Emission to Determine the Hot Electron Temperature and Conversion Efficiency in Shortpulse Laser Experiments C.D. Chen , J.A. King , F.N. Beg , A.G. MacPhee , M.H. Key , A.J. Mackinnon , L. Van Woerkom Understanding the conversion efficiency and temperature spectrum of relativistic electrons produced via laserplasma interactions is an essential first step for determining the coupling of laser energy to the compressed core of a fast ignition target. Measurements of the Bremsstrahlung spectrum and kshell yield were made using a differentially filtered imaging plate spectrometer and a singlehit CCD spectrometer on various foil and cone targets irradiated with the TITAN laser (1054 nm, 150 J, 10$^{20}$ W/cm$^{2})$ at Lawrence Livermore National Laboratory. The temperature and absolute number of relativistic electrons have been inferred from these xray measurements using the Monte Carlo code Integrated Tiger Series (ITS) 3.0. [Preview Abstract] 

GP8.00057: Enhanced harmonic generation by relativistic laser interaction with a nanostructured target Xavier LavocatDubuis , JeanPierre Matte The interaction of an ultra short (10 fs FWHM), ultra high intensity ($\mbox{I}\lambda^2 > 10^{10} \mbox{W}$) with a solid density target with a surface grating was simulated with the 2D relativistic PIC code XOOPIC [1], and compared to simulations with a smooth target surface. Very strongly enhanced emission at the wavelength of the grating period and its harmonics was obtained, nearly parallel to the target surface. The laser intensity required to obtain efficient harmonic emission was found to scale approximately with the square of the target density. \newline \newline [1] J. Verboncoeur, A. Langdon, and N. Gladd, Comput. Phys. Commun. \textbf{87}, 199 (1995). [Preview Abstract] 

GP8.00058: Modeling HighEnergy Backlighters Produced by Intense LaserMatter Interaction Gregory Pollak The utility of reasonably monoenergetic, high frequency backlighters for radiographic use in high energy density physics experiments has been understood for a long time. A reasonable approach to generating these xrays is to use a highintensity laser incident on suitable (typically midz) elements The deposition produces hot (nonthermal) electrons and ions, which ionize and excite inner shell electrons in a highly nonLTE environment Resulting xray generation often occurs in only a few boundbound transitions. Because the hot electrons have substantial range, the lines can be optically thick. In this presentation, I use the radhydro code Lasnex to deposit both a prepulse and a main pulse of order 10$^{18}$ to 10$^{19}$ watts/cm$^2$ onto Ag and Sn substrates. The physical situation is then postprocessed using Plaspp, with an embedded DCA package to produce spectra. A unique feature of these simulations are the multiphoton inversebremstrallung and photoionization physics for deposition near the critical surface, as well as nonthermal collisional physics for the nonLTE spectra. [Preview Abstract] 

GP8.00059: Development of a collisional PIC code for an analysis of cluster plasmas Toshihiro Taguchi , Thomas Antonsen , Howard Milchberg We have developed a new particleincell (PIC) code with ionization and collisional processes to analyze an interaction between a strong laser field and cluster plasmas. The code includes field and collisional ionization processes, electronelectron collisions by means of a Langevin type stochastic acceleration and electronion scattering. Using our new code, we analyzed the dynamics of a single cluster under a strong alternating electric field, which simulates a strong laser field in a range of 10$^{14}$10$^{17}$W/cm$^2$. The results show that the code has a capability to simulate a dynamical behavior of an Argon cluster from the aggregation of neutral atoms to a rapidly expanding plasma heated by a strong laser field. The results also show that a resonant heating at a specific laser intensity whose value depends on a size of the cluster, as we reported in the references. \newline [1] T. Taguchi, et al., Phys. Rev. Lett., 92, 20, 2004, 205003. \newline [2] T. M. Antonsen, Jr., et al., Phys. Plasmas 12, 5, (2005), 056703. [Preview Abstract] 

GP8.00060: PIC Simulations of ShortPulse, HighIntensity Light Interacting with Cone Targets Barbara F. Lasinski , A. Bruce Langdon , C.H. Still , Max Tabak , Richard P.J. Town In present day scenarios of fast ignition, a shortpulse high intensity laser propagates down a cone to produce hot electrons near the compressed core. Here we report on our continuing study of these cone irradiations in PIC simulations with our code, Z3. Previously we have shown\footnote{B. F. Lasinski, {\it et al}, 9$^{th}$ International Fast Ignitor Workshop, Cambridge, Mass. (2006) and B. A. P. S. {\bf 51}, 294(2006).} that in these PIC simulations, cones lead to increased absorption and higher laser intensities as compared to slab irradiations. Here, we report on the detailed spectra of the generated energetic electrons and in particular the increased hot electron temperature with cone irradiations. We look at the origin of these energetic electrons and their wide angular distribution. We vary the cone shape in both angle and the narrow end. And finally we consider the effect of underdense plasma created by a laser prepulse on these results. [Preview Abstract] 

GP8.00061: Quasimonoenergetic ions from lasertriggered multistage particle acceleration V. Yu. Bychenkov , G. I. Dudnikova , W. Rozmus , R. Fedosejevs , A. Maksimchuk A production of high quality beams of ions has received considerable attention throughout the last few years because of their potential for applications in science, technology, and medicine. In this paper we present two schemes for laser generation of quasimonoenergetic ion bunches based on 2D PIC simulations. In the first method quasimonoenergetic ion bunch is generated by twin laser pulse involving a prepulse and subsiquent main pulse both of the ultrashort duration. The spacetime parameters and energy spectrum are obtained. The second scheme exploits the effect of light ion acceleration at the heavy ion front. We found this effect to be well pronounced for moderate laser intensity ($\sim $ 10$^{18}$ W/cm$^{2})$ and pulse duration ($\sim $1 ps) by using 2D PIC simulation of laser interaction with thin CD$_{2}$ foils. Quasimonoenergetic deuterons form a jet from the rear side of the foil with the energy $\sim $1 MeV. The conversion efficiency to these quasimonoenergetic ions is 10$^{3}$. [Preview Abstract] 

GP8.00062: Energetic proton acceleration in ultraintense laser interaction with superlow density targets M. Tampo , R. Kodama , K. Higashi , K. Endo , K.A. Tanaka , T. Matsuoka , V. Yanovsky , M. Maksimchuk , G. Kalintchenko , K. Krushelnick , R. Tezuka , H. Yokogawa , R. Stephens , T. Nakamura , K. Mima Aiming to increase the maximum energy of laseraccelerated proton beams, we have studied the relation between maximum proton energies and electron distribution functions, which determine electrostatic sheath field to accelerate protons. We have proposed to increase the maximum proton energy using a distribution function of hot electrons produced by an interaction between ultrashort pulse laser ($<$ 100 f sec) and low density plasma ($<$ 10$^{20}$ cm$^{3})$. We have carried out the experiment using a silica foam (aerogel) with a density of 3mg /cc as a solid target and 30 fsec short pulse laser light at the laser intensity of 10$^{20}$ W/cm$^{2}$. We will report the result of the experiments and simulations. [Preview Abstract] 

GP8.00063: Preliminary highenergy xray measurements performed on the TRIDENT 250TW laser Jonathan Workman , J. Cobble , K. Flippo , D.C. Gautier , S. Letzring , M. Sherrill , E.S. Dodd We present preliminary measurements of Kalpha xray emission from foil and wire targets using copper, molybdenum and silver. Experiments are performed on the recently enhanced TRIDENT laser using 1ps pulses at energies up to 100J during this commissioning phase. 2D images from static grids will be presented along with pinhole measurements of emission and single photon measurements from CCD cameras. Copper emission will be recorded on timeintegrated crystal spectrometers. We will also present the design for a transmission crystal based highenergy spectrometer. [Preview Abstract] 

GP8.00064: Specular Reflection of Intense Laser Light Interacting with Solid Targets A. Link , K. Akli , D. Offermann , V. Ovchinnikov , L. Van Woerkom , R.R. Freeman , H. Chen , I. Jovanovic , A. Kemp , A. Mackinnon , A. Macphee , Y. Ping , R. Shepherd , S.C. Wilks , Cliff Chen , L. Elberson , J. King , T. Ma , F. Beg , R. AkliClarke The absorption efficiency in laser plasma interactions is of prime importance to the development of fast ignition as a nuclear fusion power source. It has been observed that the coupling of laser energy into targets is a complex process depending on target material, configuration, and laser parameters. Studies were conducted on the Callisto and Titan laser systems at Lawrence Livermore National Laboratory with intensities of up to 10$^{20}$ W/cm$^{2}$. Results will be presented for a variety of laser and target parameters. [Preview Abstract] 

GP8.00065: Determination of ElectronHeated Target Temperatures in Petawatt Laser Experiments Using Soft XRay Diagnostics Tammy Ma , Farhat Beg , Andrew MacPhee , Hyunkyung Chung , Michael Key , Andrew Mackinnon , Stephen Hatchett , Richard Stephens , Kramer Akli , Linn Van Woerkom , Bingbing Zhang The study of the transport of electrons, and the flow of energy into a solid target or dense plasma, is instrumental in the development of fast ignition inertial confinement fusion. Various solid targets (layered foils, cones, wires) were irradiated with the Titan Laser (4x10$^{19}$ Wcm$^{2})$ at LLNL. Analysis has been done on soft xray images, spectra, and streaked images to determine the thermal electron temperatures on target back surfaces. Three independent methods (Soft XRay Spectrometer, 68eV XUV Imager, and 256eV XUV Imager) were used to confirm temperatures, while a fourth diagnostic (Streaked 68eV XUV Imager) provided timeresolved temperature information. [Preview Abstract] 

GP8.00066: Hot Electron Generation Using High Intensity Laser Pulses on Machined Conical Targets Takeshi Matsuoka , Stephen Reed , Stepan Bulanov , Vladimir Chvykov , Andrei Brantov , Valery Bychenkov , Galina Kalinchenko , Christopher McGuffey , Pascal Rousseau , Victor Yanovsky , Dale Litzenberg , Karl Krushelnick , Anatoly Maksimchuk The relative number of the fast electrons has been experimentally measured for a high intensity (4x10$^{20 }$W/cm$^{2})$ laser pulse interaction with in situ machined conical aluminum targets. It is shown that the number of electrons and the plasma xray signal strongly depends on the cone depth. The cone was laser machined immediately before the 30 TW pulse arrival possibly allowing for a faster, cheaper alternative to traditional conical targets. Particleincell simulations performed for the experimental conditions will be presented. Laser machined conical targets provide a higher laser conversion efficiency into hot electrons. [Preview Abstract] 

GP8.00067: Implementation of a Stimulated Raman Amplifier/Compressor in Plasma Nikolai Yampolsky , Nathaniel Fisch , Shuanglei Li , Vladimir Malkin , Anatoli Morozov , Jun Ren , Szymon Suckewer , Ernest Valeo , Ryan Lindberg , Jonathan Wurtele A plasmabased resonant backward Raman amplifier/compressor for high power amplification of short laser pulses should, in principle, convert almost all of the pump energy to the seed pulse.\footnote{V. M. Malkin, G. Shvets, and N. J. Fisch, Phys. Rev. Lett. 82, 4448 (1999).} However, while the theoretically possible efficiency of this scheme has not yet been achieved, accompanied by strong pulse compression larger efficiencies than ever before obtained experimentally are now being reported.\footnote{J. Ren et al, invited talk, this Bulletin} These higher experimental efficiencies may be due to favorable compensation between laser parameters, including the chirp of the laser, and the density variations of the mediating plasma. This compensation may extend the region of resonance. The physical mechanisms, which might produce these effects, will be considered in light of the experimental data. This work is supported by DOE grant DEFG5207NA28122. [Preview Abstract] 

GP8.00068: Xray polarization spectroscopy for oblique laser incidence relevant to fast igniter research Y. Okano , Y. Inubushi , H. Nishimura , T. Kai , T. Kawamura , D. Batani , A. Morace , R. Redaelli , C. Fourment , J. Santos , G. Malka , A. Boscheron , A. Casner , M. Koenig , S. Fujioka , T. Nakamura , T. Johzaki , H. Nagatomo , M. Mima In a fast ignition study, xray polarization spectroscopy is known as one of the useful methods to investigate the velocity distribution function (VDF) of fast electrons in laser plasma, and anisotropy of the VDF has been observed experimentally in previous studies. In this study, we investigated the fast electron transport in intenselaser plasma under oblique incidence. The laser pulse (1 ps, 10 J) was focused onto a polyvinylchloride target at an angle of 67 degrees to the target normal at $10^{18}$ W/cm$^{2}$. It was clearly observed that the resultant ClHe$\alpha$ lines for s or ppolarized laser irradiation differed in polarization. In this presentation, the detail description of fast electron transport will be discussed along with the experimental results. [Preview Abstract] 

GP8.00069: Xray polarization spectroscopy to study energy transport in laser produced plasma at 10$^{18}$ W/cm$^{2}$ H. Nishimura , Y. Inubushi , Y. Okano , S. Fujioka , T. Kai , T. Kawamura , D. Batani , A. Morace , R. Redaelli , C. Fourment , J. Santos , G. Malka , A. Boscheron , A. Casner , M. Koenig , T. Nakamura , T. Johzaki , H. Nagatomo , K. Mima In ultrahigh intensity laser produced plasma, velocity distribution function (VDF) of hot electrons is highly anisotropic while that of cold electrons in the bulk plasma is isotropic. Xray polarization spectroscopy has been used to measure directly VDF of hot electrons in the plasma at 10$^{17}$ W/cm$^{2}$ [1, 2]. A new measurement was made at 10$^{18}$ W/cm$^{2}$ using Alis\'{e} facility at CEA/CESTA. Chlorinated triplelayer targets were irradiated and Cl He$\alpha $ line was observed with an xray polarization spectrometer. Experimental results and comparison with the model prediction will be discussed using a timedependent atomic kinetics code for polarized Cl He$\alpha$ radiation [3]. \newline [1] H. Nishimura, et al., \textit{Plasma Phys. Cont. Fusion}\textbf{47}, B823 (2005). \newline [2] Y. Inubushi, et al., JQSRT \textbf{99}, 305 (2006); \textit{Phys. Rev. }\textbf{E 75}, 026401 (2007). \newline [3] T.Kai, et al., \textit{Phys. Rev} \textbf{A 75}, 012703 (2007), T. Kawamura, et al., submitted. [Preview Abstract] 

GP8.00070: Magnetic field effects on moving onedimensional laser envelope solitons Poornakala Sethuraman Modulated nonlinear structures are formed in the interaction of an intense laser pulse with a plasma where the light energy is trapped by the density cavity. Extensive investigations have been carried out to understand the physics of these solitons. For a circularly polarized light, the electron motion leads to the generation of intense longitudinal magnetic field due to inverse Faraday effects [Sheng and MeyerterVehn, Phys. Rev. E 54, 1833 (1996)]. The effect of this magnetic field on the coherent structure is an interesting open problem. For a stationary soliton in a magnetized plasma, the trapped electromagnetic energy becomes higher in comparison to the unmagnetized case [Farina et al., Phys. Rev. E 62, 4146 (2000)]. The present study considers the moving structures in a magnetized plasma using relativistic fluidMaxwell model. The spectral characteristics as well as the stability would be investigated. The study would help qualitatively understand the role of self generated magnetic field on the stability of coherent structures. [Preview Abstract] 

GP8.00071: Implications of different stopping power models on target heating simulations using HYDRA Seth Veitzer , Peter Stoltz , John Barnard , Enrique Henestroza , Gary Kerbel , Marty Marinak Accurate numerical simulations of ion driven Warm Dense Matter experiments requires accurate models of stopping powers for targets with temperatures up to a few eV. For finite temperature targets, energy loss of beam ions is comprised of contributions from nuclear stopping, bound electron stopping, and free electron stopping. We compare two different stopping power algorithms and the implications on target heating for two different beams corresponding to the current Neutralized Drift Compression Experiment (NDCX) and proposed NDCX II experiments. The NDCX I beam has a beam energy much lower than the Bragg peak while the NDCX II beam is designed to enter the target just above the Bragg peak, and exit just below. The first stopping power algorithm is based on the classical BetheBloch formulation as is currently implemented in the HYDRA simulation code. The second algorithm is based on rescaling of experimental protonic stopping powers as developed by Brandt and Kitagawa for nuclear and bound electronic stopping, and free electron stopping following the model developed by Peter and MeyerterVehn. [Preview Abstract] 

GP8.00072: Ion beam driven warm dense matter experiments F.M. Bieniosek , P.A. Ni , M. Leitner , P.K. Roy , R. More , J.J. Barnard , M. Kireeff Covo , A.W. Molvik , H. Yoneda We report plans and experimental results in ion beamdriven warm dense matter (WDM) experiments. Initial experiments at LBNL are at 0.31 MeV K+ beam (below the Bragg peak), increasing toward the Bragg peak in future versions of the accelerator. The WDM conditions are envisioned to be achieved by combined longitudinal and transverse neutralized drift compression to provide a hot spot on the target with a beam spot size of about 1 mm, and pulse length about 12 ns. The range of the beams in solid matter targets is about 1 micron, which can be lengthened by using porous targets at reduced density. Initial experiments include an experiment to study transient darkening at LBNL; and a porous target experiment at GSI heated by intense heavyion beams from the SIS 18 storage ring. Further experiments will explore target temperature and other properties such as electrical conductivity to investigate phase transitions and the critical point. [Preview Abstract] 

GP8.00073: Diagnostics for heavy ion beam driven Warmdensematter experiments. Pavel Ni , Frank Bieniosek , Matthaeus Leitner , William Waldron Intense heavy ion beams are an excellent tool to create largevolume samples of warmdensematter (WDM) with fairly uniform physical conditions. An extensive WDM experimental program is scheduled at LBNL where NDCX accelerator is used as a driver for heating metallic targets. This poster will focus on designing and implementation of diagnostics for a target. The diagnostics include a fast multichannel optical pyrometer, absolutely calibrated streak camerabased spectrometer, Dopplershift laser interferometer (VISAR) and fast gated CCD cameras. This equipment is capable of precise measurement of temperature starting from 2000 K, pressure in kbar region, and expansion velocities up to several km/sec. Temporal resolution of the diagnostic is on a subnanosecond time scale. [Preview Abstract] 

GP8.00074: Measurement of ultrafast material dependent heating from solid foils in highintensity laserplasma interaction experiments R.L. Weber , E. Chowdhury , R.R. Freeman , J. Morrison , L. van Woerkom , E. Garcia Saiz , F. Khattak , D. Riley , S. Rose , S. Glenzer , S. Hansen , S. Wilks , B. Barbrel , M. Koenig , A. Pelka , M. Roth , R.J. Clarke , M. Notley , D. Neely , G. Gregori Ultrafast material dependent radiative heating of dense matter was observed at the Vulcan 100 TW laser facility at RAL (UK). These processes are driven by the transport of fast electrons which isochorically heat the solid at temperatures where radiative processes may become important. The peak laser intensity on target was $\sim $10$^{19}$ W/cm$^{2}$ for irradiation of 200 $\mu$m square solid foils consisting of PVDC sandwiched between either 1 $\mu$m Au, CH, or Al to study differences between high and low Z materials in the radiation drive. Characteristic xray emission from Cl was analyzed using time resolved and time integrated graphite Bragg crystals, as well as an XUV spectrometer. The plasma expansion at the rear of the target was monitored with a pinhole camera. Numerical simulations of the characteristic Cl emission have been used to infer the plasma conditions in the target. [Preview Abstract] 

GP8.00075: DIVERTORS, EDGE PHYSICS AND FUELING 

GP8.00076: Generation mechanisms of blobs in tokamak edge plasmas. Kowsik Bodi , Sergei Krasheninnikov , Andrei Smolyakov Mesoscale structures, driven by curvature and gradB effects, like blobs and ELMs play a very important role in edge and SOL plasma transport in tokamaks. Once these mesoscale structures formed, they exhibit clear convective behavior propagating mainly toward the wall at low Bfield side of the torus. The main features of convection mechanisms are relatively well understood. It is widely believed that generation of ELMs is triggered by peelingballooning instability. But, the mechanism (s) and the rate of blob generation are not clear yet. Here we present both analytic and modeling results describing the mechanisms of the blob generation triggered by subcritical phenomena related to the ballooning drive. [Preview Abstract] 

GP8.00077: Linear Analysis and Verification Suite for Edge Turbulence J.R. Myra , D.A. D'Ippolito , D.A. Russell , M. Umansky Tokamak edge physics research is becoming increasingly reliant on largescale plasma simulation. The accuracy and reliability of software codes must be insured through rigorous verification and validation. Kinetic edge physics simulation codes such as those being developed under the ESL and CPES projects could benefit from standardized benchmarks. Measurement of the linear growth rate of unstable modes emerging from a known, established equilibrium configuration provides one of the few quantitative ways of rigorously benchmarking turbulence codes with each other and with a universal standard. The present paper discusses the proposed development of a communitystandard suite of edge instability codes for linearized, nonlocal (e.g. separatrixspanning) modes in axisymmetric (realistic divertor), toroidal geometry. The suite will consist of a new eigenvalue code, as well as the recently revised BOUT code, and will be geared to provide a communitywide benchmarking/verification tool for nonlinear edge plasma simulations. Initial progress will be reported. [Preview Abstract] 

GP8.00078: Calculation of ion distribution functions and neoclassical transport in the edge of singlenull divertor tokamaks T.D. Rognlien , R.H. Cohen , X.Q. Xu The ion distribution function in the Hmode pedestal region and outward across the magnetic separatrix is expected to have a substantial nonMaxwellian character owing to the large banana orbits and steep gradients in temperature and density. The 4D (2r,2v) version of the TEMPEST continuum gyrokinetic code is used with a Coulomb collision model to calculate the ion distribution in a singlenull tokamak geometry throughout the pedestal/scrapeofflayer regions. The mean density, parallel velocity, and energy radial profiles are shown at various poloidal locations. The collisions cause neoclassical energy transport through the pedestal that is then lost to the divertor plates along the open field lines outside the separatrix. The resulting heat flux profiles at the inner and outer divertor plates are presented and discussed, including asymmetries that depend on the Bfield direction. Of particular focus is the effect on ion profiles and fluxes of a radial electric field exhibiting a deep well just inside the separatrix, which reduces the width of the banana orbits by the wellknown squeezing effect. [Preview Abstract] 

GP8.00079: Implementation of an anomalous radial transport model for continuum kinetic edge codes K. Bodi , S.I. Krasheninnikov , R.H. Cohen , T.D. Rognlien Radial plasma transport in magnetic fusion devices is often dominated by plasma turbulence compared to neoclassical collisional transport. Continuum kinetic edge codes [such as the (2d,2v) transport version of TEMPEST and also EGK] compute the collisional transport directly, but there is a need to model the anomalous transport from turbulence for longtime transport simulations. Such a model is presented and results are shown for its implementation in the TEMPEST gyrokinetic edge code. The model includes velocitydependent convection and diffusion coefficients expressed as a Hermite polynominals in velocity. The specification of the Hermite coefficients can be set, e.g., by specifying the ratio of particle and energy transport as in fluid transport codes. The anomalous transport terms preserve the property of no particle flux into unphysical regions of velocity space. TEMPEST simulations are presented showing the separate control of particle and energy anomalous transport, and comparisons are made with neoclassical transport also included. [Preview Abstract] 

GP8.00080: Simulation of turbulence in tokamak edge plasmas M.V. Umansky , J. Boedo , B. LaBombard , R. Maqueda , J. Terry , S. Zweben We undertake a comparative computational study of edge plasma turbulence in tokamaks. Some, perhaps much, of the physics underlying edge turbulence in existing tokamak experiments can be captured by fluid equations for collisional plasma, however due to the complexity of the problem in most cases one has to rely on numerical simulations. Applying electromagnetic fluid turbulence code BOUT to tokamak edge plasmas we generally find consistency with experimentally known crossfield spatial structure of the N$_i$ fluctuations having characteristic scale on the order of a few cm. Coherent structures moving radially at a speed of a few km/s are also consistent with many experimental observations. However, the numerical results can be sensitive to details of physics model, choice of parameters, and geometry options. Certain parameters are not well known experimentally and thus can serve as free ``dialing knobs,'' e.g. effective ion charge, Z$_{eff}$, and radial electric field, E$_r$, at the core boundary. Simulation results and comparative analysis for edge plasmas in Alcator CMod, NSTX, and DIIID will be presented. [Preview Abstract] 

GP8.00081: Kinetic XGC0 study of the 3D resonance magnetic perturbation effect on edge pedestal dynamics and the ELM onset boundary Gunyoung Park , S. Ku , C.S. Chang , H. Strauss , I. Joseph , R. Moyer , P. Snyder Effect of the resonance magnetic field perturbation (RMP) on the edge pedestal dynamics is studied using an edge particle code XGC0. Its impact on the stability boundary of the edge localized modes (typeI ELM) is examined by coupling XGC0 to the linear ideal MHD code Elite. Reduction of the pedestal density by RMP is explained for the first time, with increased ion temperature. The electron temperature can rise if sufficient heat can flow out from the core into the edge. In addition to the pressure profile changes in an unconventional way, the bootstrap current profile can also change in an unconventional way in the presence of RMP. Thus, RMP can modify the MHD stability property of the edge localized mode. XGC0 is a fullf, edge guiding center particle code which has a realistic magnetic field geometry with a radial electric field solver. XGC0 can include 3D magnetic perturbation, magnetic separatrix, material wall with neutral recycling, Monte Carlo neutral particles with atomics, and ions and electron particles with conserving collisions. [Preview Abstract] 

GP8.00082: Effects of Elongation on Stochastic Layer and Magnetic Footprint in Divertor Tokamaks Hasina Wadi , Morgin Jones , Halima Ali , Alkesh Punjabi An areapreserving map is constructed to calculate effects of elongation on the stochastic layer and magnetic footprint in divertor tokamaks. The generating function for the map is S(x,y) = (1/2)$\alpha ^{2}$y$^{2}$ (1y$^{2}$/2a$^{2})$+(1/2)$\beta ^{2}$x$^{2}$. Method of maps developed by Punjabi and Boozer [1,2] is used to construct the map and to calculate the stochastic layer and the magnetic footprints. The poloidal magnetic flux inside the ideal separatrix and the safety factor profile are held constant, and elongation is varied by (1) varying the width of separatrix surface in the midplane keeping the height fixed, and (2) varying the height keeping the width of separatrix surface fixed. As the width is increased, the stochastic layer and the footprint become narrower. As the height is increased, the width of stochastic layer and the footprint become narrower. Detailed results of this study will be presented. This work is supported by US DOE OFES DEFG0201ER54624 and DEFG0204ER54793. \newline [1] A. Punjabi, A. Verma, and A. Boozer, \textit{Phys Rev Lett}, \textbf{69}, 33223325 (1992). \newline [2] A. Punjabi, H. Ali, T. Evans, and A. Boozer, \textit{Phys Lett A} \textbf{364} 140145 (2007). [Preview Abstract] 

GP8.00083: The DIIID Map  An AreaPreserving Map for Trajectories of Magnetic Field Lines in the DIIID Tokamak Alkesh Punjabi , Halima Ali , Allen Boozer , Todd Evans The EFIT data for the DIIID shot 115467 3000 ms is used to calculate the generating function for an areapreserving map for trajectories of magnetic field lines in the DIIID. We call this map the DIIID map. The generating function is a bivariate polynomial in base vectors $\psi^{1/2}$cos($\theta)$ and $\psi^{1/2}$sin($\theta)$. $\psi$ is toroidal flux and $\theta $ is poloidal angle. The generating function is calculated using a canonical transformation from ($\psi $,$\theta )$ to physical coordinates (R,Z) in the DIIID [1] and nonlinear regression. The equilibrium generating function gives an excellent representation of the equilibrium flux surfaces in the DIIID. The DIIID map is then used to calculate effects of the magnetic perturbations in the DIIID. Preliminary results of the DIIID map will be presented. This work is supported by US DOE OFES DEFG0201ER54624 and DEFG0204ER54793. \newline [1] A. Punjabi, H. Ali, T. Evans, and A. Boozer, \textit{Phys Lett A} \textbf{364} 140145 (2007). [Preview Abstract] 

GP8.00084: Canonical Representations of the Simple Map Olivia Kerwin , Alkesh Punjabi , Halima Ali , Allen Boozer The simple map is the simplest map that has the topology of a divertor tokamak. The simple map has three canonical representations: (i) toroidal flux and poloidal angle ($\psi $,$\theta)$ as canonical coordinates, (ii) the physical variables (R,Z) or (X,Y) as canonical coordinates, and (iii) the actionangle (J,$\zeta)$ or magnetic variables ($\Psi $,$\Theta)$ as canonical coordinates. We give the derivation of the simple map in the (X,Y) representation. The simple map in this representation has been studied extensively (Ref. 1 and references therein). We calculate the magnetic coordinates for the simple map, construct the simple map in magnetic coordinates, and calculate generic topological effects of magnetic perturbations in divertor tokamaks using the map. We also construct the simple map in ($\psi $,$\theta)$ representation. Preliminary results of these studies will be presented. This work is supported by US DOE OFES DEFG0201ER54624 and DEFG0204ER54793. \newline [1] A. Punjabi, H. Ali, T. Evans, and A. Boozer, \textit{Phys Lett A} \textbf{364} 140145 (2007). [Preview Abstract] 

GP8.00085: Second Order Magnetic Barriers in Tokamaks, Noble Tori, and Topological Noise Halima Ali , Alkesh Punjabi Second order perturbation method of creating invariant manifold inside chaos in Hamiltonian systems [14] is applied to tokamak to build magnetic barriers inside the region of magnetic chaos created by resonant magnetic perturbations. Different safety factor profiles are used to represent tokamaks such as the ohmically heated tokamaks (OHT), the DIIID and the ASDEX UG. In OHT, a magnetic barrier is created at about midway between two resonant magnetic surfaces. The barrier reduces the diffusion of magnetic field lines by about half. The barrier is fortified by adding up to third order magnetic perturbation. Beyond a maximum value of magnetic perturbation, the barrier is not sustainable. However, if a barrier is created at noble value of safety factor, then it is found to be much more robust. For the DIIID, the robustness of magnetic barrier is tested for topological noise, and the barrier is found to be robust up to some maximum value of noise. This work is supported by US DOE OFES DEFG0201ER54624 and DEFG0204ER54793. \newline [1] Ciraolo G \textit{et al.} 2004, \textit{J. Phys. A: Math Gen }\textbf{37 }3589. \newline [2] Ciraolo G \textit{et al.} 2004, \textit{Phys. Rev. E }\textbf{69 }056213. \newline [3] Vittot M 2004, \textit{Phys. A: Math Gen }\textbf{37 }6337. \newline [4] Chandre C \textit{et al.} 2005, \textit{Phys. Rev. Lett.}\textbf{94 }074101. [Preview Abstract] 

GP8.00086: Hmode edge physics in NSTX and Alcator CMod F. Kelly , R. Maqueda , R. Maingi In NSTX (National Spherical Torus Experiment), ELMs (Edge Localized Modes) are observed using a fastframing camera to interact with an innerwall MARFE (Multifaceted Asymmetric Radiation From the Edge), leading to partial burnthrough of the MARFE during the ELM cycle [1]. We reexamine the MARFE stability [2] to attempt an explanation of the MARFE/ELM dynamics in NSTX. The contribution of ion selfdiffusion [3,4] to the radial electric field is estimated for an LH transition in Alcator CMod. \newline [1] R. Maqueda, et al., Bull. Am. Phys. Soc., \textbf{51}(7), 237 (2006); \newline [2] F. Kelly, et al., Bull. Am. Phys. Soc. \textbf{51}(7), 237 (2006); \newline [3] A. Simon, Phys. Rev. \textbf{100}, 1557 (1955); \newline [4] C. L. Longmire and M. N. Rosenbluth, Phys. Rev., \textbf{103}, 507 (1957). [Preview Abstract] 

GP8.00087: Recent results on ELMlike plasmasurface interactions produced by a conical thetapinch Travis Gray , Michael Williams , David Ruzic , Isak KonKashbaev The Divertor Erosion and Vapor shielding eXperiment (DEVeX) at the University of Illinois at UrbanaChampaign is designed to produce plasmas with densities on the order of 10$^{21}$ m$^{3}$ with a total plasma temperature of several hundred eV. This is accomplished with the rapid discharge of a 64 kJ capacitor bank through a conical shaped $\theta$pinch coil. The general purpose of the facility is to generate energetic plasma flows to study plasmamaterial interaction relevant to disruption conditions in TOKAMAKs. However, the facility has been designed with great flexibility to be able to study high power, pulsed electric propulsion; FRC formation and translation; and relevant astrophysical plasma jets. Here, the first measurements of the plasma flow and translation from the $\theta$pinch are presented. A theoretical model is also shown to predict how these energetic plasma flows will interact with solid materials. This work is important to understanding the ultimate plasma facing component (PFC) lifetime and viability. It also provides an opportunity to measure plasma/vapor cloud formation and interaction with an incident flowing plasma. [Preview Abstract] 

GP8.00088: Divertor and confinement issues for nextstep devices. Michael Kotschenreuther , Prashant Valanju , Swadesh Mahajan Next step devices operating in advanced tokamak (AT) modes include proposed experiments (including NHTX and FDF), Component Test Facilities (CTFs), and ITER. We present an analysis of the likely scrapeoff layer widths and heat loads on the divertors for such devices. We include analysis of novel divertor configurations including Xdivertors and stochastic edge. The connection between divertor modifications and core plasma confinement is also examined. [Preview Abstract] 

GP8.00089: T$_{e}$ and n$_{e}$ profile measurements with HRTS during ELM mitigation experiments with external magnetic perturbation fields on JET Roberto Pasqualotto , Alberto Alfier , Marc Beurskens , Mark Kempenaars , Claire Mckenna , Edmondo Giovannozzi , Rudi Koslowski , Yunfeng Liang In recent experiments on JET, typeI ELMs in Hmode plasmas have been controlled by a set of 4 error field correction coils (EFCC) which externally generate magnetic perturbation field with toroidal mode numbers n=1 or n=2. The effect of this perturbation on T$_{e}$ and n$_{e}$ profiles has been studied with the High Resolution Thomson Scattering (HRTS) which has recently become operative on JET. The EFCCs effect on ELMs has been investigated in various plasma configurations with different directions of the perturbation field and mode numbers. The edge pedestal barrier is modified in different ways, depending on the configuration. In all cases, ELM mitigation correlates with a reduction of the edge pressure gradient due to a reduced height and an increased width of the edge pressure transport barrier. [Preview Abstract] 

GP8.00090: Twodimensional structure of volume recombination in JT60U detached divertor plasmas Fujimoto Kayoko , Nakano Tomohide , Kubo Hirotaka , Sawada Keiji , Takizuka Tomonori , Kawashima Hisato , Shimizu Katsuhiro , Asakura Nobuyuki The volume recombination in detached divertor plasmas is a key process to reduce the ion flux to the divertor plates. Twodimensional measurement is one of the ways to investigate a spatial structure of the volume recombination. In this work, the deuterium Balmerseries lines (D$_{\alpha }$, D$_{\beta }$, ..., D$_{\theta })$ from a detached divertor plasma were observed twodimensionally with a spatial resolution of $\sim $ 1 cm and were reconstructed into twodimensional emissivities with a tomography technique. The ratio of the D$_{\beta }$ to the D$_{\alpha }$ emissivity was compared to that calculated by the collisionalradiative model. This ratio could not be explained only by the excitation of D by electron impact, indicating that the volume recombination contributed to the D$_{\beta }$ emission. This is the case for the region above the inner strike point with $\sim $ 8 cm and $\sim $ 4 cm, respectively, in the r and the zdirection on the poloidal crosssection. In this region, from the ratios of the D$_{\alpha }$, D$_{\beta }$, ..., D$_{\theta }$ emissivities, the electron density and temperature were evaluated to be $\sim $ 1E20 m$^{3}$ and $<$ 0.3 eV, respectively. [Preview Abstract] 

GP8.00091: Flute instability in the divertor plasma D.D. Ryutov , R.H. Cohen An analysis of the flute instability in the realistic geometry of an Xpoint divertor is provided, for both common and private flux regions. The drive includes curvature and the electron temperature gradient, combined with the sheath boundary condition at the divertor plates. The effects of Xpoint shearing, that have been in the past described in a semiphenomenological manner, are included based on first principles. The curvature drive is shown to be significant for both inner and outer divertor legs, contrary to the slab analysis. Characteristic signatures of the ensuing instabilities (typical frequencies, wavenumbers, correlation between the density and potential perturbations) are presented. The effects of the sheath boundary conditions on the instabilities are explicitly displayed. The results can be used for the interpretation of experiments and for code benchmarking. Work performed for US DOE by UC LLNL under contract No. W7405Eng48. [Preview Abstract] 

GP8.00092: Effect of High Recycling StepWise Migration on ITER Codeposition Jim Strachan In the modeling of the JET $^{13}$C migration experiments [1], step wise migration of the $^{13}$C along the outer target was postulated to explain the lack of $^{13}$C deposits on the outer target. The consequence was deposits were created by neutral carbon transport into the Private Flux Region. Some of that deposit can be eroded by neutral deuterium emission from the inner and outer strike points. Also important is the effect of the \underline {\textbf{E}}x\underline {\textbf{B}} force on migration from the outer strike point to the inner strike point since the \underline {\textbf{E}}x\underline {\textbf{B}} force can be high in the Private Flux Region. In this paper, these effects will be estimated for the ITER divertor. In particular the step wise migration of tungsten from the W/C intersection on the divertor should cause higher C erosion. The carbon itself will also undergo the stepwise migration causing the eroded carbon to preferentially migrate to the Private Flux Region as neutrals and to suffer further erosion by neutral hydrogenic bombardment. \newline [1] J.D.Strachan, \textit{et al}, EPS Conference on Plasma Physics (Warsaw, 2007) paper P1.030 [Preview Abstract] 

GP8.00093: Initial results from Langmuir probe and thermal desorption spectroscopy (TDS) measurements in the Tritium Plasma Experiment (TPE) Masashi Shimada , Phil Sharpe , Robert Kolasinski , Rion Causey The Tritium Plasma Experiment (TPE) has been recently relocated from Los Alamos National Laboratory (LANL) to Safety and Tritium Applied Research (STAR) facility in Idaho National Laboratory (INL). The application of a Langmuir probe system, newly designed target holder, and thermal desorption spectroscopy (TDS) system were successfully carried out, and the initial results from Langmuir probe measurements in deuterium plasma and TDS measurements of deuterium retention in tungsten are discussed. TPE is now ready to provide data to the fusion community on the interaction of tritium plasma with plasma facing components, and the future research plan is discussed. [Preview Abstract] 

GP8.00094: MHD THEORY, HEATING AND CURRENT DRIVE 

GP8.00095: Theory of Intermediate Nonlinear Ballooning Mode in a Tokamak P. Zhu , C.C. Hegna In this work we extend the ideal MHD theory of intermediate nonlinear ballooning instabilities~\footnote{P. Zhu and C.~C. Hegna, Sherwood 2007.} to the case of tokamak plasmas. Evolution equations for plasma displacements induced by the ballooning instability are analytically derived that account for the dominant nonlinear effects in an ideal MHD description. The intermediate nonlinear regime of ballooning modes is defined by the ordering that the plasma displacement ($\xi_\Psi$) across field line in the direction of pressure gradient is comparable to the mode width ($l_\Psi$) in the same direction. In the tokamak case, this regime becomes particularly relevant for a transport barrier as the width of that barrier (or pedestal) region approaches the width ($l_\Psi$) of the dominant ballooning mode. [Preview Abstract] 

GP8.00096: Unified theory of resistive and inertial ballooning modes in threedimensional configurations Tariq Rafiq , Chris C. Hegna , James D. Callen A linear stability theory of nonideal MHD ballooning modes is investigated using a two fluid model. Electron inertia, diamagnetic effects, parallel ion dynamics, transverse particle diffusion and perpendicular viscous stress terms are included in calculations for arbitrary threedimensional electron ion plasmas. Drift RBM eigenvalues and eigenfunctions are calculated for a variety of equilibria including axisymmetric shifted circular geometry and configurations of interest to the Helically Symmetric Stellarator (HSX). For parameters of interest to HSX, characteristic growth rates exceed the electron collision frequency. In this regime, electron inertia effects can dominate plasma resistivity and produce an instability whose growth rate scales with the electron skin depth. Attempts to generalize previous analytic calculations of RBM stability using a two scale analysis on $(s\alpha)$[1] equilibria to more general 3D equilibria will be addressed. In this work, a unified theory of RBM and inertial ballooning modes is developed where both the effects of ideal MHD energy and geodesic curvature drives in the nonideal layer are included in the dispersion relation. [1] R.~H Hastie, J.J.~Ramos and F.~Porcelli {\it Phys.~Plasmas} {\bf 10,} 4405 (2003). [Preview Abstract] 

GP8.00097: Stabilization of the Vertical Mode in Tokamaks by Localized Nonaxisymmetric Fields Allan Reiman We find that vertical instability of tokamak plasmas can be controlled by nonaxisymmetric magnetic fields localized near the plasma edge at the bottom and top of the torus, and that the required magnetic fields can be produced by a relatively simple set of parallelogramshaped coils. By providing stable equilibria with more highly elongated crosssections, the addition of these nonaxisymmetric fields can potentially lead to devices with improved confinement and/or beta limits. The analytical calculation assumes a large aspect ratio plasma that is well approximated by a cylinder, $\beta $ = 0, and a uniform equilibrium current density. Stability is determined by a $\delta W$ calculation, using the stellarator approximation [1] for both the equilibrium and stability calculations. The physical mechanism of the stabilization suggests that the stability properties do not depend on the precise shape of the coils, so that curvature can be introduced to optimize relative to other considerations. \newline [1] J. Greene and J. Johnson, Phys. Fluids \textbf{4}, 875 (1961); J. Johnson and J. Greene, Phys. Fluids \textbf{4}, 1417 (1961). [Preview Abstract] 

GP8.00098: Studies of ELMs and RMPs with M3D H.R. Strauss , Bernhard Hientzsch , G.Y. Park , C.S. Chang , L. Sugiyama Several recent applications of M3D are presented. Studies are in progress in the penetration of resonant magnetic perturbations (RMP) which have been found to stabilize edge localized modes (ELM). In a two fluid MHD model, RMPs did not provide ELM stabilization in studies conducted so far. Instead the plasma relaxes toward a 3D equilibrium. The ELM stabilization evidently comes from kinetic modification of the pressure and current profiles. Simulations with the XGC kinetic neoclassical code suggest that RMPs are screened from the plasma. Calculation of screening caused by plasma rotation is in progress. In other work, ELM benchmarking simulations will be be presented. In linear simulations, M3D, NIMROD, and ELITE were found to be in reasonable agreement. Preliminary application of spectral elements to ELM simulations will be presented. [Preview Abstract] 

GP8.00099: Kinetic Effects of a NonMaxwellian Distribution of Energetic Particles on 2/1 Stability R. Takahashi , D.P. Brennan , C.C. Kim , A.D. Turnbull , R.J. La Haye Recent experiments have shown JET discharges to be stable for values of $\beta _N /4\ell _I $ as a function of $\rho ^\ast $ far exceeding where JT60U, DIIID, and ASDEXU are unstable. It is conjectured that kinetic effects of energetic particles can play a crucial role in the stability of the 2/1 mode in JET. Using model equilibria based on experimental reconstructions, the nonideal MHD stability and nonlinear evolution of the 2/1 mode is investigated including a deltaf PIC model for the energetic particles coupled to the MHD solution. Modifications of the ideal outer region solution of linear resistive MHD codes are discussed, along with preliminary results from initial value computations. [Preview Abstract] 

GP8.00100: Reduced energy principle for ideal/tearing modes in separatrix limited plasmas Joshua Kallman , Leonid Zakharov Ideal and tearing MHD modes near the edge of a plasma represent a significant threat to plasma stability, confinement, and plasma facing material surfaces. Theoretical and numerical studies of these modes are extremely difficult due to the presence of a magnetic separatrix and the multiple resonance surfaces inside it. In this presentation, we examine an exceptional case in which the MHD energy principle can be reduced to the minimization of a line integral functional instead of a complicated 2D expression, thereby avoiding numerical convergence problems. In addition, a numerical implementation of BishopTaylor equilibria, a special class of toroidal equilibria in which a unique set of magnetic flux surfaces can be determined by infinitely many pressure and current profiles, is discussed. Due to this indeterminacy, such equilibria are of great use in calibrating equilibrium codes, and can additionally contain a separatrix region, which makes them especially relevant for the stability analysis outlined above. [Preview Abstract] 

GP8.00101: A general MHD stability formulation for plasmas with flow and resistive walls Jeffrey Freidberg , Luca Guazzotto , Riccardo Betti Plasma rotation, induced either by means of neutral beams (e.g. in NSTX and DIIID) or appearing spontaneously (e.g. in Alcator CMod, JET and Tore Supra) is routinely observed in modern tokamak experiments. Plasma rotation has a major effect on plasma stability. In particular, flow and flow shear stabilize external modes such as the resistive wall mode (as observed e.g. in DIIID), and also have a significant influence on turbulence, internal kinks and ballooning modes. A selfconsistent analysis of the effect of rotation requires the use of numerical tools. In this work, we extend our previous analysis and present a general \textit{variational} eigenvalue formulation of the stability problem. The analysis includes arbitrary (both toroidal and poloidal) plasma rotation and a thin resistive wall of arbitrary shape and resistivity. It is shown the problem can always be reduced to a classic eigenvalue formulation of the kind i$\omega $\textbf{A}$\cdot $\textbf{$\zeta $=B}$\cdot $\textbf{$\zeta $}, where \textbf{$\zeta $} is the unknown eigenvector related to the plasma displacement, and $\omega $ the (complex) evolution frequency of the perturbation. The formulation is well suited for a finite element analysis. [Preview Abstract] 

GP8.00102: A Model for Coupled Turbulence and Resistive MHD Evolution D.P. Brennan , C. Holland , R. Takahashi The development of a coupled three field turbulence and resistive MHD mode theory is investigated. The effects of turbulence are known to be important in the evolution of MHD instabilities, and the modifications to the background equilibrium by the MHD instabilities are known to affect turbulent fields. Our initial investigations focus on the effects of turbulence on the linear resistive MHD stability of an unstable equilibrium in slab geometry, as well as the effects of the concomitant finite magnetic island structure on the local turbulent fields. Analytic descriptions are presented of the turbulent resistivity and viscosity, and MHD instability criteria in this equilibrium. Results are then presented of the turbulent fields and linear growth rates in the presence of the island. Both resistive Alfven wave and drift wave turbulence are addressed. Finally, preliminary results are presented from an initial value code modeling the turbulence, which will be coupled to the nonlinear MHD evolution of the island. [Preview Abstract] 

GP8.00103: Extending the collisional fluid equations into the long meanfreepath regime in toroidal plasmas. IV. Banana Regime K. Shaing In Part I [Phys. Fluids B \textbf{2}, 1190 (1990)] and Part II [Phys. Plasmas \textbf{12}, 082508 (2005)], it is emphasized that the equilibrium plasma viscous forces when applied for the magnetohydrodynamic (MHD) modes are only rigorously valid at the mode rational surface where $m$  \textit{nq} = 0. Here $m $is the poloidal mode number, $n$ is the toroidal mode number, and $q$ is the safety factor. This important fact has been demonstrated explicitly by calculating the viscous forces in the plateau regime in Part I, and II. Here, the effective viscous forces in the banana regime are calculated for MHD modes by solving the linear drift kinetic equation that is driven by the plasma flows first derived in Part I. At the mode rational surface, the equilibrium plasma viscous forces are reproduced. However, it is found that away from the mode rational surface, the viscous forces for MHD modes decrease, a behavior similar to that observed in the viscous forces for the plateau regime. The proper form of the momentum equation that is appropriate for the modeling of the MHD modes is also discussed. [Preview Abstract] 

GP8.00104: A family of analytic equilibrium solutions for the GradShafranov equation. Luca Guazzotto , Jeffrey Freidberg In toroidal systems, such as the tokamak, magnetohydrodynamic equilibria are routinely described by means of the well known GradShafranov (GS) equation. Analytic solutions of the equation are few and far between, and equilibria are normally determined with the help of numerical tools. Even though equilibrium codes are nowadays very reliable, it is still worthwhile to investigate the existence of analytic solutions of the GS equation, because (1) such equilibria are very useful in providing benchmark cases to test existing codes, (2) analytic solutions provide a good model to test for stability without having to worry about accuracy and resolution issues arising from numerically computed equilibria. In this work, we present a technique to solve the GS equation for special, but realistic, profiles of the two free functions of magnetic flux. Our solution allows us to retain arbitrary plasma elongation and triangularity, arbitrary aspect ratio, and arbitrary beta, while setting the edge current and pressure gradient to zero. We show that realistic equilibria for standard (e.g. ITER, CMOD) and spherical (e.g. NSTX) tokamaks can be obtained with our technique. [Preview Abstract] 

GP8.00105: Free boundary threedimensional anisotropic pressure equilibria W.A. Cooper , J.P. Graves , M. Jucker , S.P. Hirshman , J. Kisslinger , P. Merkel , H. Wobig , Y. Narushima , S. Okamura , K.Y. Watanabe An anisotropic pressure model for threedimensional magnetohydrodynamic equilibria with nested magnetic flux surfaces has been implemented in a free boundary version of the VMEC code. The energetic particles are described with a modified BiMaxwellian distribution function that satisfies the constraint ${\bf B\cdot\nabla}{\cal F}_h=0$. Applications to 2field period quasiaxisymmetric stellarator reactor system at large $\left<\beta\right>\sim 5\%$ with large pressure anisotropy and offaxis hot particle deposition have been explored to test the limits of the code. The hot particle pressure distributions reproduce the structures previously obtained under fixed boundary conditions. For example, for $p_{\perp}>p_{}$ and high field side hot particle deposition, the $p^h_{\perp}$ distribution localises also on the high field side contrary to the $p^h_{}$ structure which concentrates on the low field side. For low field side deposition, both hot particle components appear on the low field side. A radially outward shift of the entire plasma column constitutes the dominant finite $\left<\beta\right>$ effect. Plasma shape alterations are also observable. [Preview Abstract] 

GP8.00106: An Optimal Magnetic Coordinate system for HighBeta ST configurations Janardhan Manickam In the study of magnetohydrodynamics of magnetically confined systems, it is well known that both analysis and computation are facilitated by an appropriate coordinate system. Specifically, a magnetic coordinate system,$(\Psi,\theta,\zeta)$,where $\Psi$ is a flux label, $\theta$ a poloidal angle and $\zeta$ a generalized toroidal angle, such that magnetic field lines are straight in $(\theta,\zeta)$ space. The generalized toroidal angle, $\zeta$, can be related to the Cartesian angle $\phi$, by introducing a periodic function $\delta(\Psi,\theta)$. This function depends on the choice of Jacobian, and is identically zero when the Jacobian is proportional to $x^2$. This coordinate is commonly referred to as PEST coordinates. A more general approach to straight field line coordinates is obtained when the Jacobian is defined as $J = X^i/\alpha(\Psi) \nabla\dot\Psi^j$. Commonly used coordinate systems are: PEST, with i=2 , j=0; Equal Arcs, with i=j=1; and Hamada with i=j=0. Each of these coordinates has its own merits, but for high beta spherical tori, we identify a new coordinate system, i=0, j=1, which is optimal to this regime. We present results comparing the different coordinate systems in different parameter regimes. [Preview Abstract] 

GP8.00107: 3DMAPTOR Code for mapping toroidal magnetic field lines in three dimensions Esteban Ch\'avez , Julio Herrera A 3D code has been developed in order to simulate the magnetic field lines in circular crosssection tokamaks. The toroidal magnetic field can be obtained from the individual fields of circular coils arranged around the torus, or alternatively, as a rippleless field. The poloidal field is provided by a given toroidal current density profile. Proposing initial conditions for a magnetic filed line, it is integrated along the toroidal angle coordinate, and Poincar\'{e} maps can be obtained at any desired cross section plane. Following this procedure, the code allows the mapping of magnetic field surfaces for the axisymmetric case. For this work, the density current profile is chosen to be bellshaped, so that realistic safety factor profiles can be obtained. This code is used in order to study the breaking up of external surfaces when the symmetry is broken by an inner coil with tilted circular loops, with the purpose of modelling the behaviour of ergodic divertors, such as those devised for TEXTOR. [Preview Abstract] 

GP8.00108: Fast Particle Losses due to NTMs and Magnetic Field Ripple E. Strumberger , S. Guenter , E. Schwarz , C. Tichmann We performed a detailed numerical study for the interaction between fast particles and large scale magnetic perturbations and toroidal field ripple. In particular we focussed our study on the losses of fast ions created by neutral beam injection (NBI) for an ASDEX Upgrade discharge with neoclassical tearing mode (NTM) activity. For these investigations we used as an input an equilibrium carefully reconstructed from experimental data. The ripple is selfconsistently included by a 3D, freeboundary equilibrium computation. The magnetic islands caused by (2,1) NTM are introduced by a field perturbation superimposed to the equilibrium magnetic field. Experimental data have been used to reproduce the size and location of those islands numerically. Starting from a realistic seed distribution, the guiding centres of about 100000 fast ions are traced up to a given time limit, or until they hit plasmafacing structures. A detailed analysis of the particle trajectories will provide important information of the underlying loss mechanisms such as: i.) prompt losses of passing particles caused by drift island formation, and ii.) losses of trapped particles due to stochastic diffusion. [Preview Abstract] 

GP8.00109: Supersonic drifttearing magnetic islands in tokamak plasmas Richard Fitzpatrick , Francois Waelbroeck A twofluid theory of long wavelength, supersonic, drifttearing magnetic islands in low collisionality, low$\beta$ plasmas possessing relatively weak magnetic shear is developed. The model assume s both slab geometry and cold ions, and neglects electron temperature and equilibrium current gradient effects. The problem is solved in two asymptotically matched regions. The ``inner region'' contains the island. However, the island emits electrostatic driftacoustic waves which propagate into the surrounding ``outer region'', where they are absorbed by the plasma. Since the waves carry momentum, the inner region exerts a net force on the outer region, and {\em vice versa}, giving rise to strong velocity shear in the region immediately surrounding the island. Isolated supersonic islands propagate with a velocity which lies between those of the unperturbed local ion and electron fluids, but is much closer to the latter. The ion polarization current is {\em stabilizing}, and {\em increases}\/ with increasing is land width. Finally, the supersonic branch of isolated island solutions {\em ceases to exist}\/ above a certain critical island width. Supersonic islands whose widths exceed the critical width are hypothesized to bifurcate to the socalled ``subsonic'' solution branch. [Preview Abstract] 

GP8.00110: Nonlinear island dynamics in the presence of sheared toroidal flow C.C. Hegna Recent experimental observations indicate a sensitivity of neoclassical tearing mode threshold physics and saturated island widths to the plasma rotation properties. An analytic theory for nonlinear magnetic island physics in toroidal plasmas is developed that allows for equilibrium toroidal flows. Specifically, equations governing the helical equilibrium state in the vicinity of an isolated magnetic island are developed using an asymptotic theory based on a small island approximation. The island profiles are determined to within three functions of the helical magnetic flux that are subsequently determined by transport properties in the island region. The presence of sheared toroidal flow alter island polarization currents, helical PfirshSchl\"uter currents produced by pressure and curvature and the Mercier indices needed for the asymptotic matching. The effect of sheared rotation on the external ideal MHD matching data ($\Delta'$) will also be addressed. [Preview Abstract] 

GP8.00111: Plasma Rotation Effects on the Externally Driven Magnetic Island Formation Yasutomo Ishii , Andrei Smolyakov We investigate the effects of the current sheet caused by the Alfven resonance on the magnetic island formation by the externally applied perturbation in rotating plasmas. One of the important problems of the driven magnetic island formation is the onset of the rapid island growth after the flowsuppressed growth phase. This onset is triggered by the plasma rotation reduction around the resonant magnetic surface. In the standard theory on this problem, the plasma rotation is damped by the plasma current formed at the resonant surface. In the low viscosity regime, however, the current sheet is formed not at the resonant surface (neutral line) but around the Alfven resonant surfaces. Hence, the plasma rotation is damped in the wider region than that of the magnetic island width. In this case, the critical value shows weak dependence on the viscosity. We revisit the driven magnetic island formation problem by including the Alfven resonance effects in the wide parameter regime. [Preview Abstract] 

GP8.00112: Finite Ion Orbit Effects on Magnetic Islands in Toroidal Plasmas Xinzheng Liu , Chris Hegna A kinetic theory for the interaction of an ion population with an isolated magnetic island in a high aspect ratio tokamak plasma is presented. We examine islands whose characteristic widths are larger than the ion gyro radius but comparable to the ion banana width. In this regime, the trapped ions do not respond to the island electrostatic potential and helical magnetic geometry due to the banana drifts. When solving the drift kinetic equation for ions, a change in coordinates is used to account for this behavior. A bounce averaging procedure is developed to separate out and solve the lower order distribution function. A twofluid model is used to determine the electrons response. Quasineutrality leads to a selfconsistent calculation for the electrostatic potential. An iteration procedure is introduced to calculate the potential, which is shown to be a combination of functions of the helical flux surfaces and the topologically toroidal flux surfaces. These results are contrasted with the results of small ion orbit case. The contribution to the perturbed current is composed of the helical flux surfaceaveraged bootstrap current and the perpendicular ion polarization current. Using this current in the Rutherford equation, the island width evolution equation is determined. A pair of selfconsistent equations for the island width, $w$, and its rotation frequency, $\omega $, is to be derived. *Research supported by US DoE under grant No. DEFG0286ER53218. [Preview Abstract] 

GP8.00113: Critical Toroidal Rotation Profile for Resistive Wall Modes in Tokamaks K.C. Shaing , M. Chu , S.A. Sabbagh , M. Peng It is known that resistive wall modes in tokamaks can be stabilized by toroidal plasma rotation. The critical toroidal rotation speed is reduced when the enhanced plasma inertia is included in the polarization current density. Here, we develop a model to calculate the critical rotation profile when toroidal plasma rotation is actively controlled. This is accomplished by including the neoclassical dissipation mechanism associated with the perturbed parallel plasma viscosity, and its corresponding inertia enhancement factor. It is illustrated that the important quantity is the toroidal rotation profile and is not necessarily the toroidal plasma rotation speed at a particular radius. [Preview Abstract] 

GP8.00114: Toward incorporating the effects of a resistive wall in the linear stability spectrum of ideal MHD with arbitrary equilibrium flows S.P. Smith , S.C. Jardin , J.P. Freidberg , L. Guazzotto The ideal MHD linear stability normal modes and frequencies for a circular cylindrical plasma (having an arbitrary equilibrium flow and a conducting wall at the surface) are calculated using a variational finite element approach. A cubic bspline finite element is used for the radial component of the displacement and the derivative of a cubic bspline is used for the other two components. This both avoids spectral pollution and gives desirable convergence properties. Comparisons of the calculated normal modes and frequencies to analytic results and to other numerical studies are presented. Investigations into the effects of axial and azimuthal flows are also presented. Note that the formulation is such that in the future a resistive wall can be added seamlessly into the code, maintaining the form of a standard eigenvalue problem $\mathbf {A}\cdot\mathbf{x}=\omega\,\mathbf{B}\cdot\mathbf{x}$. [Preview Abstract] 

GP8.00115: AEGISGK: Gyrokinetic investigation of resistive wall mode stability L.J. Zheng , M. Kotschenreuther , J.W. Van Dam The stability of resistive wall modes (RWM) is an issue of concern for burning plasma confinement, e.g., in ITER. The kinetic resonances, as well as the shear Alfv\'en resonance, have been shown to be important for RWM stability. However, due to the complexity of kinetic effects, only hybrid models with partial kinetic effects have so far been used to investigate RWM stability. The success in recovering full MHD with our newly derived gyrokinetic theory [Phys. Plasmas {\bf 14}, 072505 (2007)] now allows the possibility to study RWMs in a selfconsistent kinetic manner. We will present our scheme for a gyrokinetic treatment of RWMs and also analyze various kinetic effects. In particular, we will demonstrate that the parallel electric field, missing in conventional kinetic treatments, cannot be ignored in studying the effects of waveparticle resonances on RWMs. Also, we will show how the kinetic resonances and the shear Alfv\'en resonance can couple with each other. Preliminary numerical results from the AEGISGK code, which incorporates the new gyrokinetic theory, will be also presented. [Preview Abstract] 

GP8.00116: Wall mode stabilization at slow plasma rotation Bo Hu , Riccardo Betti , Holger Reimerdes , Andrea Garofalo , Janardhan Manickam Unstable pressuredriven external kink modes, which become slowly growing resistive wall modes (RWMs) in the presence of a resistive wall, can lead to tokamak plasma disruptions at high beta. It has been shown that RWMs are stabilized by fast plasma rotation (about 12\% of the Alfv\'en frequency) in experiments. Conventional theories attribute the RWM suppression to the dissipation induced by the resonances between plasma rotation and ion bounce/transit or shear Alfv\'en frequencies [1]. In those theories, the kinetic effects associated with the plasma diamagnetic frequencies and trappedparticle precession drift frequencies are neglected. It has been observed in recent experiments [2,3] that the RWM suppression also occurs at very slow plasma rotation (about 0.3\% of the Alfv\'en frequency), where the conventional dissipation is too small to fully suppress the RWMs. Here it is shown, that the trappedparticle kinetic contribution associated with the precession motion [4] is large enough to stabilize the RWM in DIIID at low rotation. Work supported by the USDoE OFES. \noindent [1] A. Bondeson and M. S. Chu, Physics of Plasmas, {\bf 3},3013 (1996). [2] H. Reimerdes {\it et al.}, Physical Review Letters, {\bf 98},055001 (2007). [3] M. Takechi {\it et al.}, Physical Review Letters, {\bf 98},055002 (2007). [4] B. Hu and R. Betti, Physical Review Letters, {\bf 93},105002 (2004). [Preview Abstract] 

GP8.00117: Stability analysis of resistive wall mode including effects of plasma rotation and error field. Masaru Furukawa , Linjin Zheng We have formulated the resistive wall mode stability analysis via an initialvalue approach instead of the conventional normal mode approach in order to resolve the critical rotation for stability and the braking problems. Plasma inertia and rotation are taken into account at a narrow layer around a rational surface. In the plasma region except for the layer, the Newcomb equation (inertialess MHD equation) is solved. Then the solutions are matched across the narrow layer. In the vacuum region, the Laplace equation for the scalar potential of perturbed magnetic field is solved, and the solutions are connected across a thin resistive wall. In the resistive wall, the diffusion equation for the perturbed magnetic field is solved. Then, we obtain two evolution equations for the amplitude of the mode. The linear growth rates agree well with those obtained by the normalmode approach. By coupling an evolution equation of the plasma rotation, which includes torque by the mode and error field, we can investigate the quasilinear evolution. [Preview Abstract] 

GP8.00118: Control of magnetohydrodynamic modes in RFPs with a resistive wall above the wall stabilization limit John Finn , Gian Luca Delzanno Studies are shown of control of magnetohydrodynamic (MHD) modes in a cylindrical model for an RFP, in the presence of a resistive wall, below and above the regime for which stabilization is possible with a perfectly conducting wall, i.e. below and above the ideal wall limit. The results show that resistive plasma (tearinglike) modes can be feedback stabilized for current profiles which are unstable below and above the ideal wall limit, for reversed field pinch RFPlike profiles (q(r) decreasing) in a simple model with step function current and pressure profiles. Similar results were found for tokamaklike (q(r) increasing) profiles. However, above the limit for wall stabilization of ideal plasma modes, resonant or nonresonant, the feedback scheme cannot provide stabilization. The control scheme senses both normal and tangential components of the perturbed magnetic field, and the feedback is proportional to a linear combination of the two. More recent results with realistic RFP profiles also show that ideal and resistive (tearing) modes can both be stabilized below their wall stabilization limits. Tearing modes, but not ideal plasma modes, can be stabilized above their wall limits. A physical interpretation of these results is presented. We will also present new results including plasma rotation or complex gain. [Preview Abstract] 

GP8.00119: RF Sheath Models D.A. D'Ippolito , J.R. Myra RF sheath formation on the antennas and walls in ICRFheated experiments can reduce the heating efficiency, limit the coupled power, and cause damage to plasmafacing structures. The sheaths are driven by a slow wave component of the rf field due to a mismatch between the magnetic field and the boundary (antenna or wall). Quantitative modeling of the highly nonlinear sheaths may now be feasible for the first time in massivelyparallelprocessing (MPP) codes developed in the RF SciDAC project. Recently, a new approach to sheath modeling was proposed,\footnote{D.A. D'Ippolito and J.R. Myra, Phys. Plasmas {\bf 13}, 102508 (2006).} in which the sheath physics is incorporated into the RF wave computation by using a modified boundary condition (BC) on the RF fields in both wave propagation and antenna codes. Here, we illustrate the use of the sheath BC for nearfield sheaths by a model calculation that includes electromagnetic effects and a simple antenna coupling model. Properties of the model (such as the role of sheathplasma waves) and implications for antenna codes such as TOPICA\footnote{V. Lancellotti et al., Nucl. Fusion {\bf 46}, S476 (2006).} will be discussed. [Preview Abstract] 

GP8.00120: Electromagnetic high frequency gyrokinetic particleincell simulation of radio frequency waves in magneticallyconfined plasmas. Roman Kolesnikov , Hong Qin , W.W. Lee Using the gyrocentergauge kinetic theory, we developed an electromagnetic version of the high frequency gyrokinetic algorithm [1, 2] for particleincell (PIC) simulation of plasma heating and current drive with RF waves. Gyrokinetic formalism enables separation of gyrocenter and gyrophase motions of a particle in a magnetic field. From this point of view, a particle may be viewed as a combination of a slow gyrocenter and a quickly changing Kruskal ring. The efficiency of the algorithm is due to the fact that the simulation particles are advanced along the slow gyrocenter orbits, while the Kruskal rings capture fast gyrophase physics. The nonlinear dynamics of RF waves is described by the Kruskal rings based on first principles physics. Selfconsistent simulation is performed by solving Faraday's and Ampere's laws using Yee's algorithm together with the locally implicit method [3]. We performed a number of simulations of electromagnetic wave propagation in hot inhomogeneous plasmas using new nonlinear deltaf PIC algorithm. Comparisons with a direct Lorentzforce approach are presented. This work is supported by the MSG project (U.S. DoE ASCR Multiscale Mathematics Research and Education Program). [1] R. A. Kolesnikov et al., Phys. Plasmas, \textbf{14}, 072506 (2007). [2] H. Qin et al., 17$^{th}$ RF Conference (2007). [3] D.Smithe et al., 17$^{th}$ RF Conference (2007). [Preview Abstract] 

GP8.00121: Relativistic effects in electron cyclotron resonance heating and current drive A.K. Ram , J. Decker In the electron cyclotron range of frequencies (ECRF) the X and O modes are used in conventional tokamaks for generating plasma current and for modifying the current profile. The same is envisioned for ITER. In spherical tokamaks (ST) electron Bernstein waves (EBW) are expected to play a similar role. For a proper description of the damping of EC waves, the code R2D2 numerically solves the fully relativistic dispersion relation [1]. It also evaluates the quasilinear diffusion operator for the interaction of EC waves with electrons. This is used in the relativistic threedimensional FokkerPlanck code LUKE [2] to solve for the electron distribution function. We will present results obtained with R2D2 and LUKE on the relativistic characteristics of EC waves and on the driven plasma current. We will show that the EBW interaction with electrons in present day STs has similar physics to that of O waves interacting with electrons in ITER. \newline [1] A.\ K.\ Ram, J.\ Decker, and Y.\ Peysson, {\it J.\ Plasma Physics} {\bf 71}, 675 (2005). \newline [2] J.\ Decker and Y.\ Peysson, {\it EuratomCEA Report EURCEAFC1736} (2004). [Preview Abstract] 

GP8.00122: Progress in theoretical and numerical modeling of RF/MHD coupling using NIMROD Thomas G. Jenkins , Dalton D. Schnack , Chris C. Hegna , James D. Callen , Carl R. Sovinec , Eric D. Held , JeongYoung Ji , Scott E. Kruger Preliminary work relevant to the development of a general framework for the selfconsistent inclusion of RF effects in fluid codes is presented; specifically, the stabilization of neoclassical and conventional tearing modes by electron cyclotron current drive is considered. For this particular problem, the effects of the RF drive can be formally captured by a quasilinear diffusion operator which enters the fluid equations on the same footing as the collision operator. Furthermore, a ChapmanEnskoglike method can be used to determine the consequent effects of the RF drive on the fluid closures for the parallel heat flow and stress. We summarize our recent research along these lines and discuss issues relevant to its implementation in the NIMROD code. [Preview Abstract] 

GP8.00123: Sheath boundary in 3D timedomain edge plasma simulation D.N. Smithe , A. Hakim , D.A. D'Ippolito , J.R. Myra , E.F. Jaeger , L.A. Berry A general purpose timedomain plasma simulation algorithm has been constructed and implemented in the VORPAL software framework.[1] It is able to represent the complex physical boundaries of the ICRF antenna structure, and complex magnetic topology of the edge region. This timedomain algorithm is now being supplemented with a subgrid boundary sheath model based upon the work of D'Ippolito et al.[2] We verify the model against known behavior from frequencydomain sheath calculations in 1dimension. We also test the model in 3D simulation including RF launcher geometry, and compare results with related models being implemented in 1, 2, and 3D full wave solvers. This new model will provide realistic estimates of power loss due to short range sheaths. We will also present possible strategies for treating mid and long range sheaths within the model. \newline [1] D. N. Smithe, Physics of Plasmas, Vol. 14 056104 (2007). \newline [2] D. A. D'Ippolito and J. R. Myra, Phys. Plasmas 13, 102508 (2006). [Preview Abstract] 

GP8.00124: Simulation of High Power ICRF Wave Heating in the ITER Burning Plasma E.F. Jaeger , L.A. Berry , R.F. Barrett , E.F. D'Azevedo ITER relies on Ioncyclotron Radio Frequency (ICRF) power to heat the plasma to fusion temperatures. To heat effectively, the waves must couple efficiently to the core plasma. Recent simulations using AORSA [1] on the 120 TF Cray XT4 (Jaguar) at ORNL show that the waves propagate radially inward and are rapidly absorbed with little heating of the plasma edge. AORSA has achieved 87.5 trillion calculations per second (87.5 teraflops) on Jaguar, which is 73 percent of the system's theoretical peak. Three dimensional visualizations show ``hot spots'' near the antenna surface where the wave amplitude is high. AORSA simulations are also being used to study how to best use ICRF to drive plasma currents for optimizing ITER performance and pulse length. Results for Scenario 4 show a maximum current of 0.54 MA for 20 MW of power at 57 MHz. \newline [1] E.F. Jaeger, L.A. Berry, E. D'Azevedo, \textit{et al}., Phys. Plasmas. \textbf{8}, 1573 (2001). [Preview Abstract] 

GP8.00125: Full wave simulations of lower hybrid waves in toroidal geometry with nonMaxwellian electrons John Wright , Ernest Valeo , Cynthia Phillips , Paul Bonoli , Marco Brambilla Analysis of LH wave propagation in the past has been done using ray tracing and the WKB approximation. Advances in algorithms and the availability of massively parallel computer architectures has permitted the solving of the MaxwellVlasov system for wave propagation directly. These simulations have shown that the bridging of the spectral gap (the difference between injected phase velocities and the velocity at which damping on electrons occurs) can be explained by the diffraction effects captured by the full wave algorithm  an effect missing in WKB based approaches. However, these full wave calculations were done with a Maxwellian electron distribution and it is well know that a quasilinear plateau between the point of most efficient damping on electrons at about 23 v$_{te}$ and where collisional and quasilinear diffusion balance. Ray tracing codes have long iterated to a selfconsistent steady state with FokkerPlanck codes. To address this discrepancy and better model experiment, we have implemented a nonMaxwellian dielectric in our full wave solver. We will show how these effects improve coupling and penetration into the plasma of the waves and show comparisons with ray tracing and experiment. [Preview Abstract] 

GP8.00126: Influence of the poloidal phase difference of antenna current on eigenmodes and power absorption in the ion cyclotron range of frequencies Suwon Cho , JongGu Kwak The load resilient antenna utilizing the conjugate T matching method is known to be effective in the rf power coupling for ELMy plasmas. Contrary to the conventional antenna, the load resilient antenna can have the phase difference of the current between the two straps above and below the equatorial plane, which may affect the heating efficiency. In this work, effects of the phase difference are examined using the full wave simulation code TORIC. It is found that the poloidal phase difference can cause eigenmodes to appear at different toroidal mode numbers and it influences power absorption especially large when distinct eigenmode modes are excited. They can exist over the entire range of the toroidal mode number when the density is relatively low and can exist at either very low values or high values of the toroidal mode number otherwise. As the density increases, distinct eigenmodes at particular toroidal mode numbers disappear smoothing the power absorption spectrum except for a few lowest toroidal mode numbers and interference due to the poloidal phase difference generally leads to weak power absorption over the broad range of the toroidal mode number. [Preview Abstract] 

GP8.00127: Design of the ITER Electron Cyclotron Heating and Current Drive Waveguide Transmission Line T.S. Bigelow , D.A. Rasmussen , M.A. Shapiro , J.R. Sirigiri , R.J. Temkin , H. Grunloh , J. Koliner The ITER ECH transmission line system is designed to deliver the power, from twentyfour 1 MW 170 GHz gyrotrons and three 1 MW 127.5 GHz gyrotrons, to the equatorial and upper launchers. The performance requirements, initial design of components and layout between the gyrotrons and the launchers is underway. Similar 63.5 mm ID corrugated waveguide systems have been built and installed on several fusion experiments; however, none have operated at the high frequency and longpulse required for ITER. Prototype components are being tested at low power to estimate ohmic and mode conversion losses. In order to develop and qualify the ITER components prior to procurement of the full set of 24 transmission lines, a 170 GHz high power test of a complete prototype transmission line is planned. Testing of the transmission line at 12 MW can be performed with a modest power ($\sim $0.5 MW) tube with a low loss (1020{\%}) resonant ring configuration. A 140 GHz long pulse, 400 kW gyrotron will be used in the initial tests and a 170 GHz gyrotron will be used when it becomes available. Oak Ridge National Laboratory, managed by UTBattelle, LLC, for the U.S. Dept. of Energy under contract DEAC0500OR22725. [Preview Abstract] 

GP8.00128: Modulated LHCD with Feedbak control to Active Suppress MHD m=2 on HT7 J.S. Mao , J.R. Luo , Y.W. Sun , B.J. Ding A crucial issue for the extension of advanced tokamak scenarios to long pulse operation is the avoidance of MagnetoHydrodynamics (MHD) activity. Active Modulation of Lower Hybrid Current Drive (LHCD) was used successfully to suppress MHD activity on HT7, a superconducting tokamak. A feedback system was used which activated modulation only when MHD activity reach a predetermined level so as to optimize the current drive through out the discharge. The LHCD modulation was varied in power and frequency, with the frequency always being less than the resistive skin time (100ms). Optimal MHD suppression was achieved when modulating LHW power $>$ 200kW, and frequency of 50Hz. Details of the MHD suppression will be discussed in this poster. Active Modulation of LHCD was used successfully to suppress MHD activity. This was achieved in discharges with MHD m=2 tearing modes during the discharge conditions Ip=110KA, Bt=1.75T, Ne$\sim$1.1x1013cm$^{3}$. The amplitude, interval and the period of LHCD modulation pulse can be adjusted very conveniently. The modulation LHCD can be delivered very fast at the any time during the discharge. The modulation LHCD period was always much shorter than the plasma resistive time. So the profile of plasma current is changed much fast than the plasma resistive time. The different forms of LHCD modulating can be proved. [Preview Abstract] 

GP8.00129: SIMULATION: MHD 

GP8.00130: SIESTA: an Scalable Island Equilibrium Solver for Toroidal Applications Raul Sanchez , Steven Hirshman , Vickie Lynch The construction and development of a new ideal MHD 3Dequilibrium solver, capable of dealing with magnetic islands and stochastic regions in a fast, accurate and scalable manner will be described. The SIESTA code will complement other existent 3D MHD island solvers and is particularly suited for applications that require not only accuracy but speed of evaluation as well, such as experimental 3D equilibrium reconstruction or stellarator design. SIESTA will also be useful to calculate MHD equilibria at very high spatial resolutions, such as those that might be required for the investigation of NTMs at ITERrelevant temperature and resistivity conditions. SIESTA is based on a preconditioned, iterative algorithm that takes advantage of a preexistent VMEC solution to provide both a background coordinate system that guarantees a compact representation as well as a good initial guess for the iterative procedure. Details of the algorithm implementation, its performance on some simple test problems and initial steps towards its porting to a massively parallel environment will be discussed. [Preview Abstract] 

GP8.00131: Results from the PSICenter Interfacing Group B.A. Nelson , C.C. Kim , A.I.D. Macnab , R.D. Milroy , T.R. Jarboe , J. Kesner , D.T. Garnier , C.R. Sovinec , P.M. Bellan , M.R. Brown The Interfacing Group of the Plasma Science and Innovation Center (PSICenter  http://www.psicenter.org) facilitates simulations of collaborating Innovative Confinement Concept (ICC) experiments. Present collaborating experiments include the Bellan Plasma Group (Caltech), FRXL (Los Alamos National Laboratory), HITSI (Univ of Wash  UW), LDX (M.I.T.), MBX (Univ of TexasAustin), MST, Pegasus (Univ of WiscMadison), PHD (UW), SSPX (Lawrence Livermore National Laboratory), SSX (Swarthmore College), TCS (UW), and ZaP (UW). NIMROD code meshes have been created and/or modified for the Caltech, SSX, and LDX experiments. Simulations of the Caltech and SSX experiments study formation and buildup of electrodedriven helicity injection. LDX simulations study stability of marginallystable equilibria as additional heating increases pressure gradients. NIMROD output files are interfaced to the powerful 3D viewer, VisIt (http://www.llnl.gov/visit), which will be demonstrated. Results from these simulations, as well as an overview of the Interfacing Group status will be presented. [Preview Abstract] 

GP8.00132: MHD Simulations with Self Consistent Boundary Conditions G.J. Marklin , T.R. Jarboe Modern ICC experiments, such as those using inductive helicity injection and rotating field current drive, use insulation to allow flux from multiple circuits to enter and form complex patterns of rotating E{\&}M fields over the surface. The HITSI geometry is used to develop a new method of handling such boundary conditions for 3D simulations. The insulating layer between the plasma and the conducting wall allows magnetic flux to move along the surface at the speed of light, assumed to be infinite, until it finds equilibrium with the plasma and circuit conditions it encounters on each time step. This 2D surface equilibrium determines the locally self consistent magnetic boundary condition. Plasma inflow is used to model gas injectors and the momentum boundary condition couples to the surface magnetic field leading to a nonlinear Poisson equation. This poster will derive these surface equilibrium equations and show how they are solved on a tetrahedral mesh. Simulations of a spheromak tilting mode in a cylinder, a toroidal RFP, and HITSI will show the difference between the insulated conductor and the conventional bare conductor boundary condition. The HITSI results will be compared with experimental data to determine whether the physics of the resistive MHD model is adequate to describe observed reconnection rates. [Preview Abstract] 

GP8.00133: The Effect of a Weak Toroidal Field on the n=2 Rotational Instability in an FRC R.D. Milroy , L.C. Steinhauer , A.I.D. Macnab , C.C. Kim , C.R. Sovinec The n=2 rotational instability has almost always been observed in dynamically formed FRCs. This instability is driven by centrifugal forces in the rotating plasma, but can be stabilized with multipole fields. Translated FRCs often do not exhibit this instability and a recent analysis [H.Y. Guo, et al., Phys. Rev. Lett. 95, 17001 (2005)] implies that a small toroidal field could stabilize it. We are investigating this effect numerically with the NIMROD code, and analytically using the energy principal. When modest toroidal magnetic field is added to an FRC with its high elongation and small aspect ratio, a spherical torus like configuration can be formed with a safety factor q exceeding 1 over the entire configuration. We have found that the addition of a relatively weak toroidal magnetic field to an FRC can stabilize the n=2 rotational instability, but for calculations that do not include the Hall term, a more complex n=2 mode remains unstable. Inclusion of the Hall term can dramatically reduce the growth rate, or stabilize this mode too. [Preview Abstract] 

GP8.00134: Nonlinear MHD simulation of DC helicity injection in spherical tokamaks R.A. Bayliss , C.R. Sovinec 3D nonlinear MHD computations using the NIMROD code have been performed to study DC helicity injection in the HITII and Pegasus spherical tokamaks. Current drive via DC helicity injection has been successfully employed with either a poloidalgap voltage known as coaxial helicity injection (CHI) [used in HITII and NSTX] or a biased miniature plasma gun [used in CDX and Pegasus]. Numerical studies of CHI in a simplified geometry with $\beta=0$ reproduce the ``bubbleburst" formation and the subsequent excitation and saturation (characterized in HITII by amplification of poloidal flux) of a linetied internal kinkmode. The computed strength of saturated fluctuations and poloidal flux are in quantitative agreement with data obtained in the HITII experiment. Results from $\beta\neq0$ simulations with an experimentally accurate geometry will also be presented. Cases driven by a numerical representation of miniature plasma gun selfconsistently evolve pressure and anisotropic thermal transport and simulate the formation, merger, and relaxation of the current filaments to a tokamaklike plasma. The results are compared to experimental data from the Pegasus ST. In both injection scenarios the simulations permit a detailed description of the 3D equilibria exhibited by the helicityinjected driven plasma and reproduce the observations made in the Pegasus ST and HITII of amplified poloidal flux and generation of toroidal current. [Preview Abstract] 

GP8.00135: Impact of velocity space distribution on hybrid kinetic MHD simulation of the $(1,1)$ internal kink mode Charlson C. Kim Simulation studies of the impact of the velocity space distribution on the stabilization of $(1,1)$ internal kink mode and excitation of the fishbone mode were performed with a hybrid kinetic MHD model. The simulations were performed by extending the physics capabilities of \textbf{NIMROD}(NonIdeal MHD with Rotation  Open Discussion)a three dimensional extended magnetohydrodynamic (MHD) code to include kinetic effects of an energetic minority ion species. These kinetic effects are included by computing a pressure moment tensor using $\delta f$ particleincell (PIC) method. The marker particles are advanced in the self consistent NIMROD fields. We outline the implementation and present simulation results of energetic minority ion stabilization of the $(1,1)$ internal kink mode and excitation of the fishbone mode. A benchmark of the linear growth rate and real frequency are shown to agree well with M3D. We examine the impact of the details of the velocity space distribution such as extending the velocity space cut off and the impact of passing versus trapped particles and show that they strongly impact the stabilization and excitation of the $(1,1)$ mode. [Preview Abstract] 

GP8.00136: Nonlinear simulations of the m=0 instability development in zpinch equilibria with axial sheared flows Ioana Paraschiv , Bruno S. Bauer , Irvin R. Lindemuth , Volodymyr Makhin A detailed study of the linear and nonlinear development of the m=0 instability in the presence of sheared axial flows has been performed using a twodimensional magnetohydrodynamic numerical code, MHRDR, to solve singlefluid ideal MHD equations. In order to accurately study the sheared flow effects on the zpinch stability, the code was modified to include periodic boundary conditions and a monotonic van Leer advection algorithm. Linear growth rates obtained with MHRDR were in good agreement with the linear theory ($<$10{\%} difference). Nonlinear mode coupling and saturation of the sausage instability have been studied for zpinch equilibria with and without sheared flows. It was found that sheared flows changed the m=0 development by reducing the linear growth rates, decreasing the saturation amplitude, and modifying the instability spectrum. High spatial frequency modes were stabilized to small amplitudes, and only the long wavelengths continued to grow. Full stabilization was predicted for supersonic plasma flows. [Preview Abstract] 

GP8.00137: Timedependent closures for plasma fluid equations Eric Held , JeongYoung Ji , Michael AddaeKagyah Two approaches to calculating timedependent parallel closures for plasma fluid equations are presented. Both solve a lowestorder drift kinetic equation that includes time dependence, free streaming, and an exact treatment of the linearized Coulomb collision operator. The first approach extends the theory of Chang and Callen \footnote{ Z. Chang and J. D. Callen, {\it Phys. Fluids B} {\bf 4} (5), 1167 (1992).} by including additional moments in the treatment of the collision operator as well as initial value effects for the distribution function. Timedependent equations for the closures are derived via inverse Laplace/Fourier transforms of single pole approximations to the pseudotransport equations. The second approach entails a continuum solution to the drift kinetic equation using 2D finite elements for the velocity space variables. As enhancements to the first approach, this method allows for arbitrary geometry as well as the full Coulomb collision operator. [Preview Abstract] 

GP8.00138: Comparing Reduced Fluid Models to the TwoFluid Plasma System Bhuvana Srinivasan , Uri Shumlak The twofluid plasma model is studied and compared to reduced fluid models such as HallMHD. Three asymptotic approximations are independently applied to the full twofluid plasma model to obtain the reduced models which include charge neutrality, infinite speed of light and negligible electron inertia. HallMHD is pursued because it captures additional physics as compared to ideal MHD. The additional physics takes into account twofluid effects by using the Hall and the diamagnetic drift terms believed to be important in Hall accelerators, Zpinches, Field Reversed Configurations, and other such applications. Twofluid effects become significant when the characteristic spatial scales are small compared to the ion skin depth and the characteristic time scales are short compared to the inverse ion cyclotron frequency. The motivation here is to compare HallMHD to the twofluid model to study the physics that is lost or captured by applying the approximations in addition to comparing the simplicity of implementation of the models. Simulations of electromagnetic plasma shock, and current sheets with inplane magnetic fields (i.e. collisionless reconnection) and outofplane magnetic fields are performed and the results are compared between the models. [Preview Abstract] 

GP8.00139: Twofluid simulations of sawteeth in a periodic boundary driven screwpinch. V.S. Lukin , S.C. Jardin We numerically study nonlinear evolution of m=1 internal kink mode in 2D helical geometry. Initial value simulations have been conducted with the macroscopic modeling code SEL. A number of plasma fluid models, from reduced MHD to full twofluid extended MHD, have been applied to the problem. Both resistive and twofluid evolution of an ideally unstable initial condition through full Kadomtsev reconnection is studied. In the semicollisional regime, onset of fast reconnection is shown to be correlated with the width of resistive current sheets falling below characteristic inertial scales available to the system. In simulations with assumed peaked radial profile of conductivity and Ohmic current drive, formation of a helical paramagnetic quasi equilibrium with enhanced stability properties is observed following the initial reconnection event. Plasma is then shown to produce periodic sawtoothing behavior which is independent of the initial conditions. Observed sawteeth are characterized by relatively slow semiresistive kinking followed by apparent onset of the quasiinterchange mode on an ideal MHD timescale. Incomplete reconnection of the plasma core, maintaining the safety factor $q$ in the central plasma region below unity throughout a sawtooth cycle, is demonstrated. [Preview Abstract] 

GP8.00140: Toroidal Axisymmetric ExtendedMHD SteadyStates with Flow N.M. Ferraro , S.C. Jardin , A.C. Bauer Axisymmetric steadystates of the full extendedMHD (XMHD) equations, including twofluid effects, flow, and gyroviscosity, are obtained by evolving the XMHD equations from an initial idealMHD equilibrium. Steadystates for both large aspectratio limited plasmas and NSTXlike diverted plasmas are presented. Selfconsistent PfirchSchl\"uter flows are observed, and spontaneous spinup is observed to develop even when a simple resistive singlefluid model is used, in agreement with previous theoretical and numerical results. In the steadystate, resistive and thermal losses are offset by inductive current drive. These accurate and selfconsistent steadystates may be used as the initial equilibrium for nonaxisymmetric XMHD linear stability calculations, for example. The axisymmetric steadystates are obtained using M3D$C^1$, a parallel, implicit, nonlinear, highorder finite element code. Cylindrical coordinates are used instead of flux coordinates, eliminating difficulties arising from the coordinate singularity at the magnetic xpoint in diverted plasmas. The vacuum region is modeled as a highresistivity plasma, allowing the same physical equations to be applied throughout the simulation domain. An unstructured, adaptive triangular mesh is used to maximize computational efficiency without degrading spatial resolution. This work was supported by US DOE contract DEAC0276CH03073. [Preview Abstract] 

GP8.00141: A New Code for Resistive Wall Mode Modeling with 3D Conducting Structures Yueqiang Liu , R. Albanese , A. Portone , G. Rubinacci , F. Villone The resistive wall mode (RWM) is a macroscopic MHD instability that limits the fusion power production of advanced tokamaks. Realistic modeling of this mode often requires detailed 3D description of the conducting structures such as the surrounding resistive wall. We have developed a new code CarMa [1] by coupling the MHD stability code MARSF [2] with the 3D finite element based eddy current code CARIDDI [3]. The coupling scheme is shown correct both analytically and numerically. Feedback stabilization of RWM is investigated for ITER advanced scenarios. \newline [1] R. Albanese, et al., COMPUMAG 2007 conference, Aachen (Germany), June 2007 \newline [2] Y.Q. Liu, et al., Phys. Plasmas 7, 3681 (2000) \newline [3] R. Albanese, G. Rubinacci, Adv. Im. El. Phys.,102, 186, Acad. Press 1998 [Preview Abstract] 

GP8.00142: Simulations of NTM Stabilization using Current Drive Offset Relative to the ISLAND Center Jennifer Woodby , Eugenio Schuster , Arnold Kritz , Glenn Bateman , Alexei Pankin High plasma pressure can cause simply nested magnetic flux surfaces to tear and reconnect, leading to the formation of magnetic islands. The neoclassical tearing mode (NTM) instability drives magnetic islands to grow to saturated widths, at which the islands can persist stably. The presence of magnetic islands leads to a local flattening of the pressure profile and locally hollow current profile within the island. The flattening of the pressure profile is undesirable in that it can result in degradation of plasma confinement. One common method of stabilizing NTMs and shrinking the magnetic islands is to replace the diminished currents within the islands using direct current injection via electron cyclotron current drive. Maximum stabilization is achieved when current is driven at the island center, the location of which is not accurately known in experiments. In this study, the current drive is expressed mathematically as a Gaussian current drive density in Hamada coordinates. The effect of current drive offset relative to the island center is investigated in preparation for feedback control. [Preview Abstract] 

GP8.00143: Numerical Studies of Linear Two Fluid Tearing Modes in Slab and Cylindrical Geometries J.R. King , C.R. Sovinec , V.V. Mirnov The NIMROD code is applied to twofluid tearing computations in slab and cylindrical geometry. Linear computations in slab geometry with large guide field and forcefree equilibria scan plasma beta and the tearing stability parameter for benchmarking with analytical theory. A revised meshing algorithm improves numerical resolution, and convergence studies for all parameter regimes are presented. Growth rates approach the MHD values at beta values much less than 1{\%}. Nonlinear results for these forcefree cases show broadening of a Hall dynamo effect to the island width scale upon saturation. The effect of adding guide field to the nonforcefree GEM problem is also investigated; fast twofluid reconnection becomes suppressed. Finally, cylindrical forcefree linear calculations with parameters relevant to the Madison Symmetric Torus Reversed Field Pinch are compared to existing analytics. The broadening of the flowvelocity profile is understood qualitatively from the analytical foundation. Requirements for nonlinear 3D twofluid cylindrical computations are also considered. [Preview Abstract] 

GP8.00144: Simulations of Decaying Kinetic Alfv\'en Wave Turbulence: Intermittent and Coherent Structures Kurt Smith , Paul Terry We simulate decaying kinetic Alfv\'en wave turbulence in a strong guide field, appropriate for modeling interstellar turbulence at scales $\leq 10\rho_s$. Ion flow decouples from the system at these scales, while electron density fluctuations equipartition with the magnetic field. From an initial Gaussian distribution, the system decays to a nonGaussian PDF characterized by a large current kurtosis and positiveedge, negativecore Gaussian curvature filaments. Current filaments and their associated magnetic and density structures are longlived, unmixed by the surrounding turbulence. The intensity of density structures does not scale with the intensity of current filaments, since the system permits a density structure to exist with a corresponding filament of either sign. Structures merge only if they correspond to likesigned current filaments. We investigate the scaling of structure radial extent with magnitude, the physics of structure mergers, and the averaged radial profile of density structures outside the core region, proposed to track the $r^{1}$ profile of the magnetic field.Work supported by NSF. [Preview Abstract] 

GP8.00145: Kinetic excitation of Alfv\'{e}nic instabilities near the second ballooning stability boundary in a high$\beta$ toroidal plasma Andreas Bierwage , Liu Chen The kinetic excitation and/or damping of plasma waves in a high$\beta$ tokamak plasma is studied using linear gyrokinetic simulations. A new code was developed to accurately simulate excitations in a broad range of frequencies and wavelengths. It describes the evolution of the electromagnetic fields $\delta{\bf B}_\perp$, $\delta B_\parallel$ and $\delta E_\parallel$ subject to effects of kinetic compression of thermal and energetic ions, finite Larmor radii and finite drift orbit widths. The $s$$\alpha$ equilibrium model and ballooning representation are employed. For example, the code is capable of investigating kinetic ballooning modes, Alfv\'{e}nic ion temperature gradient modes, $\beta$ and toroidicityinduced Alfv\'{e}n eigenmodes, and energetic particle modes. Our current focus is on the parameter regime near the second ballooning stability boundary, where the properties of Alfv\'{e}nic instabilities including kinetic thermal ion compression will be examined. Corresponding results will be reported as they become available. [Preview Abstract] 

GP8.00146: Large Eddy  Lattice Boltzmann (LESLB) Simulations of Fluid and MHD Turbulence Brian Keating , Min Soe , George Vahala , Linda Vahala , Jeffrey Yepez , Jonathan Carter For high Reynolds number turbulence, the resource requirements for a full spacetime DNS simulation scales as Re$^{3}$  which is far beyond any foreseeable computational resources. For problems that require instantaneous fields, one is forced into an LES in which one filters out the unresolvable small scales in the simulation but must then deal with the effects of the subgrid scales on the resolvable scales. In the Lattice Boltzmann (LB) mesoscopic approach one sidesteps the stiff nonlinear convective derivatives in the nonlinear continuum equations by simple linear advection in kinetic space together with local collisional relaxation at each spatial node. The relaxation distribution functions have simple algebraic continuum nonlinearities. In LES, the Smagorinsky eddy viscosity is related to the mean rate of strain tensor. However this tensor can be computed from purely locally moments in LB. In a Smagorinsky LESMHD, the subgrid magnetic Reynold stress can be determined from local kinetic moments. [Preview Abstract] 

GP8.00147: Low Frequency Plasma Lagrangian H. Vernon Wong A formulattion of the plasma Lagrangian for low frequency electromagnetic perturbations is discussed, The analysis is based on a small Larmor radius expansion of the Vlasov equation in which the perpendicular magnetohydrodynamic (MHD) response is separated from the intrinsic parallel particle response. The EulerLagrange equations reproduce the linearized MHD and driftkinetic equations. Hybrid ``fluidkinetic'' equations are readily derived, with inclusion of kinetic and finite Larmor radius effects. Gauge invariance is preserved, and any representation of the perturbed fields can be accommodated. [Preview Abstract] 

GP8.00148: Magnetohydrodynamics inside a rotating sphere. David Montgomery , Pablo Mininni , Leaf Turner The equations of incompressible MHD are solved inside a uniformly rotating rigid spherical shell. The method of solution is a Galerkin expansion for the vector fields involved. The normal components of these fields vanish at the spherical boundary. The expansion basis functions are the spherical ChandrasekharKendall eigenfunctions of the curl. A prescribed mechanical forcing excites a wide variety of dynamo behavior, all (so far) at unit magnetic Prandtl number. Key control parameters seem to be mechanical and magnetic Reynolds numbers, the Rossby and Ekman numbers (which we vary by varying the rotation rate of the sphere), and the amount of mechanical helicity injected. Magnetic energy levels and magnetic dipole behavior fluctuate strongly in a few eddy turnover times, but seem to stabilize as the rotation rate is increased, until the limit of the code resolution is reached. The detailed geometry of the mechanical forcing appears to be important. [P.D.Mininni et al, Phys. Fluids 18, 116602 (2006) and New Journ. of Physics (to appear, 2007).] [Preview Abstract] 

GP8.00149: Plasma Wave Echoes in a Weakly Collisional Plasma C. Black , K. Germaschewski , C.S. Ng , A. Bhattacharjee It has been shown recently that weak collisions, which are a singular perturbation on the collisionless Vlasov equation, have a profound effect on the underlying spectrum for linear plasma waves by eliminating the CaseVan Kampen continuous spectrum and replacing it with a complete class of discrete eigenmodes [C.S. Ng, A. Bhattacharjee, F. Skiff, Phys. Rev. Lett. {\bf 83}, 1974 (1999); {\bf 92}, 065002 (2004).]. This discovery has important consequences for the validity of the classical theory of C. H. Su and C. Oberman [Phys. Rev. Lett. {\bf 20}, 427 (1968)] on the collisional decay of plasma wave echoes. We have developed a parallel onedimensional VlasovPoisson system solver including the LenardBernstein collision operator, and benchmarked this code with our earlier numerical results on the discrete spectrum. We have also completed simulations of plasma wave echoes in the collisionless system. We will report our results on the effect of collisions on the echoes, testing the theory of Su and Oberman, and present some novel features in echo dynamics caused by the discrete spectrum of collisional eigenmodes. [Preview Abstract] 

GP8.00150: Driven, autoresonant threeoscillator interactions Oded Yaakobi , Lazar Friedland , Zohar Henis An efficient control scheme of resonant threeoscillator interactions (R3OI) using an external chirped frequency drive is suggested. The approach is based on formation of a double phase locked (autoresonant) state in the system, as the driving oscillation passes the linear resonance with one of the interacting oscillators. When doubly phaselocked, the amplitudes of the oscillators increase with time in proportion to the driving frequency deviation from the linear resonance. The stability of this phaselocked state, the effects of dissipation and of the initial threeoscillator frequency mismatch on the autoresonance are analyzed. The associated autoresonance threshold phenomenon on the driving amplitude is also discussed. In contrast to other nonlinear systems, driven, autoresonant threeoscillator excitations are independent of the sign of the driving frequency chirp rate. [Preview Abstract] 

GP8.00151: MH4D Benchmarking and Atomic Physics Implementation Eric Meier Two key benchmarks of MH4D have been made: 1) Screw pinch kink and spheromak tilt modes have been simulated in MH4D with nonlinear ideal MHD. Linear growth rates are compared to results from linear stability computations. 2) MH4D has been used to simulate the ZaP Flow ZPinch experiment, and benchmarked against results from a welldeveloped 2D MHD code, MACH2. Periodic boundary conditions are used in MH4D to allow quasi2D simulation. Resistivity and ohmic heating are included in these simulations. Beyond these benchmarks, the 3D capability of MH4D has been explored by simulating gas injection in ZaP. Also, the accuracy and utility of the implicit and semiimplicit features of MH4D have been assessed. First order atomic physics have been implemented in MH4D. A cold static neutral fluid is tracked, and the applicable temperaturedependent ionization, recombination, and charge exchange terms are included in each of the MHD equations and in the neutral fluid density equation. A significant background density of neutral fluid is shown to cause the expected slowing of spheromak tilt mode growth. The effect of ionization (delayed plasma generation) on ZaP plasma dynamics is explored. [Preview Abstract] 

GP8.00152: OPTIMAL HELICON SOURCE PERFORMANCE 

GP8.00153: Crosscorrelation diagnostics of electrostatic fluctuations in a helicon source Michael Kraemer The absorption of helicon waves was observed to be intimately connected with the excitation of shortscale electrostatic fluctuations [1]. Crosscorrelation techniques using microwave backscattering at the upperhybrid resonance as well as electrostatic probes enable measurements of their frequency and wavenumber spectra. The lowfrequency band can be attributed to ionsound fluctuations, while the highfrequency fluctuations obey the dispersion relation of TrivelpieceGould waves. The fluctuations satisfy the matching conditions for the parametric decay instability of the helicon wave. Operating the helicon discharge in a pulsed mode, the growth rates and the thresholds of the fluctuations can be deduced from their temporal growth in a wide parameter range. Good agreement with a theory that accounts for the nonzero axial wavenumber of the helicon pump was achieved. The close relationship between the rf absorption and the excitation of the fluctuations is studied in more detail by performing time and spaceresolved measurements of the helicon field and the electrostatic fluctuations. In particular, the role of the radial plasma inhomogeneity on the parametric excitation of the fluctuations is examined. Supported by the Deutsche Forschungsgemeinschaft (SFB 591, Project A7). [1] B. Lorenz, M. Kr\"{a}mer, V.L. Selenin, Yu.M. Aliev, Plasma Sources Sci. Technol. 1\textbf{4}, 623 (2005). [Preview Abstract] 

GP8.00154: Slow wave measurement using the WVU 300 GHz collective scattering diagnostic Robert Hardin , Earl Scime , Alex Hansen Recent experiments in helicon plasma sources by Kr\"{a}mer \textit{et al}. [2006] and Kwak \textit{et al}. [2006] have employed mmwave technology to investigate electron densities in a pulsed source and density fluctuations due to ionacoustic waves, respectively. Measurement of the temporal and spatially resolved electron densities by Kramer was accomplished with a mmwave interferometer. The ionacoustic waves measured by Kwak employed a collective scattering system with a heterodyne detection scheme. The WVU 300 GHz quasioptical collective scattering diagnostic, uses a homodyne detection method similar to the interferometer, designed to measure the ``slow'' wave. Experimental parameters observed to heat ions in the plasma edge in conjunction with theoretically calculated wave numbers associated with the slow wave, as seen in Kline \textit{et al}. [2002], were examined for evidence of the slow wave using the mmscattering diagnostic. Here we present initial wave number spectrum measurements of the slow wave in a helicon plasma source. M. Kr\"{a}mer, B. Clarenbach, and W. Kaiser, Plasma Sources Sci. Technol. \textbf{15}, 332 (2006). J.G. Kwak, S.J. Wang, S.K. Kim, and S. Cho, Phys. Plasmas \textbf{13}, 074503 (2006). J.L. Kline, E.E. Scime, R.F. Boivin, A.M. Keesee, and X. Sun, Plasma Sources Sci. Technol. \textbf{11}, 413 (2002). [Preview Abstract] 

GP8.00155: Resonant power absorption experiments on the Radially Localized Helicon mode C. Lee , G. Chen , D. Berisford , R. Bengtson , T. Scarborough We present results of a series of experiments exploring the resonant power absorption as it relates to the Radially Localized Helicon (RLH) mode. We expand on previous work on this field by doing a frequency scan using a second RF generator as a frequency probe. We increase the measured frequency range to include the lower hybrid resonance (LHR) frequency as well frequencies above the driving frequency. The external magnetic field is varied in order to change LHR frequency conditions. Measurements of power absorption are taken using an insitu RF sensor to measure voltage, current, and phase. [Preview Abstract] 
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