Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session R1: Poster Session: Magnetically Confined Plasma II 
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Room: Hyatt Regency Dallas Marsalis Hall B, 2:00pm  5:00pm 

R1.00001: Particlebased closure relations for Neoclassical MHD Studies D. Spong, S.P. Hirshman, D. delCastillo Negrete, E. D'Azevedo, R. Mills, M. Fahey The nonlinear dynamics of neoclassical MHD tearing modes (NTM) are significantly influenced by the variation of the local (perturbed) bootstrap current within magnetic tearing mode island regions. The bootstrap current is introduced into the MHD equations through closure relations involving the parallel component of the pressure tensor. The threedimensional magnetic field structure within island regions, coupled with the need to retain one and possibly tw velocity dimensions motivates the use of Monte Carlo methods. We have adapted the DELTA5D stellarator particle code for the calculation of such closure relations. A new deltaf partitioning has been used so that plasma flows and gradients can be held constant while viscous coefficients are calculated by the particle code. This method has been successfully tested against the DKES code for axisymmetric equilibria. Second, an improved compressed representation of the magnetic field data has been developed using principal orthogonal decomposition methods and singular value decomposition. This has been applied to data from the M3D MHD code and should lead to improved performance and a decreased memory footprint for the particle calculation. [Preview Abstract] 

R1.00002: Blobs, momentum transport and tokamak rotation J.R. Myra, D.A. D'Ippolito, D.A. Russell, S.I. Krasheninnikov, B. Coppi This paper examines how instabilities in the vicinity of the last closed surface (LCS) can provide a mechanism for tokamak rotation. Our hypothesis is: (i) that edge instabilities saturate by the generation of filamentary coherent structures (blobs) which convect radially outward towards the wall; and (ii) when the underlying unstable waves have a preferred phase velocity, momentum can be transferred to the blobs and lost from the core plasma, providing a recoil force that rotates the core. To test these ideas, a simple two field (2D PDE) model similar to the WakataniHasegawa and blob models is proposed which embodies the essential features of electrostatic drift wave instability and curvaturedriven blob transport in a layer near the LCS. The resulting equations are solved numerically in the strong (order unity fluctuation) limit. Then, employing an exact momentum conservation law, we derive a diagnostic to account for momentum flow across the LCS, and use it to obtain the net edge momentum source for tokamak rotation due to turbulencegenerated ExB flows. [Preview Abstract] 

R1.00003: A GyrotronPowered Pellet Accelerator for Tokamak Fueling P.B. Parks, F.W. Perkins A novel pellet acceleration concept [1] using microwave power from MW gyrotron sources has been developed that could pave the way for highspeed $>$3 km/s innerwall pellet injection on ITERclass tokamaks. The concept is based on the principal of a gun, where a highpressure propellant gas drives the projectile down the barrel. In the proposed concept, the high gas pressure is created by evaporative explosion of a composite ``pusher'' medium attached behind the DT fuel pellet. The pusher consists of micronsized conducting particles, (Li, Be, C) embedded uniformly in a D$_{2}$ ice slug with $<$5{\%} volume concentration, thus facilitating microwave energy absorption by dissipation of eddy currents flowing within the conducting particles only. Microwave power is delivered to the pusher along a waveguide, which also serves as the pellet launch tube. A scaling law predicts that a pellet of mass M accelerated over a distance $L$ reaches a velocity v $\cong $ (PL/M)$^{1/3}$, where P is the gyrotron power.$\backslash $pard[1] P. Parks {\&} F. Perkins, US patent application ``MicrowavePowered Pellet Accelerator,'' No. 11/256/662, October 21, 2005. [Preview Abstract] 

R1.00004: Gyrokinetic particle simulation of global Alfven modes in toroidal geometry Igor Holod, Zhihong Lin, Yasutaro Nishimura Global Alfven modes are important for energy confinement studies, since thay can resonantly interact with fusion alfa particles. The electromagnetic version of GTC PIC code has been devoloped in order to be capable to describe these modes. In the code ions are treated kinetically, while electrons are adiabatic in the zeroth order of an expansion based on the smallness of electrontoion mass ratio. Toroidal coupling of different shear Alfven modes leads to the apperance of gaps in the continuum frequency spectrum. Inside these gaps Toroidal Alfven Eigenmodes (TAE) can exist. Keeping electromagnetic effects by taking into account magnetic field perturbations in the simulations, gives us a possibility to observe various Alfven modes, in particular TAE. Starting with random perturbations of vector potential, the shear Alfven modes die out due to the continuum damping and the dstinctive peaks inside TAE frequency gaps are observed. Linear dispersion relation of the observed modes is compared with analytical theory to benchmark the simulations. [Preview Abstract] 

R1.00005: Regularization of Transport Bifurcation Models L. Beria, M.A. Malkov, P.H. Diamond A simple theoretical understanding of what regulates the width of both ITB and Hmode layers remains elusive. Onefield models ``solve'' the problem via the Maxwell construction, and related phase coexistence criteria. Unfortunately, an interesting barrier model must evolve two independently driven fields, such as density and temperature. We present an analytical solution of a simple twofield model. The problem of regularization, encountered previously, is solved by retaining pressure profile curvature effects in the electric field shear. Retaining such effects allows us to determine when a transition actually occurs within the interval of possible transitions. In fact, transitions are predicted to occur at the lower end (in heating power) of the coexistence range. This softens threshold requirements. A testable consequence of this approach is that the model predicts that transitions may occur in regimes of flat density. Ongoing work is aimed at exploring the effect of noise. [Preview Abstract] 

R1.00006: Momentum transport in magnetic islands F.L. Waelbroeck, D. Grasso, F. Porcelli, C. Tebaldi We examine the transport of momentum across an island using the reduced magnetohydrodynamic (RMHD) model. We find that the Reynolds stress gives rise to a momentum source proportional to the resistivity. As a result of the frozenin property the transport of momentum can be described by a onedimensional equation, even for islands with finite aspectratio. We present numerical and analytic solutions of this transport equation and compare these solutions to numerical solutions of the full time dependent RMHD equations. Of particular interest is the momentum transport in islands where the helical current density reverses sign. In such islands, the Reynolds stress also reverses sign, creating the possibility for localized zonal flow generation. The constantpsi approximation, however, fails in the presence of current reversal. We have developed new equilibrium solutions for thin islands that we plan to use to examine the transport of momentum in the presence of current reversal. [Preview Abstract] 

R1.00007: The Effects of Improved Equilibrium Accuracy on Resistive DCON Alan H. Glasser Numerical computation of the outer region matching data for resistive and other singular MHD modes of axisymmetric toroidal plasmas is much more sensitive to errors in the equilibrium solution of the GradShafranov Equation (GSE) than corresponding ideal MHD stability analysis. While many direct and inverse GSE solvers are capable of producing sufficiently accurate solutions for ideal analysis, most have difficulty achieving adequate resolution and iterative convergence for resistive analysis. We have developed a GradShafranov refiner using highorder spectral elements to improve on the accuracy of such solutions. The direct form of the GSE is solved iteratively, starting from an inaccurate initial solution, to obtain a highly accurate final solution, using the flux coordinates of the initial equilibrium, then mapped to a new refined inverse form. The effects of improved accuracy on resistive DCON will be shown. [Preview Abstract] 

R1.00008: Characteristics of impurity production and transport in ITER edge plasmas T.D. Rognlien, R.H. Bulmer, M.E. Rensink, J.N. Brooks The mixedmaterial (C, W, Be) aspect to the ITER wall makes it especially important to model to determine the intermixing of materials owing to spatial transport and redeposition of sputtering materials. Here the 2D UEDGE transport code includes both lower and (more remote) upper Xpoints to model the edge plasma with the possible existence of strong convective radial transport. The chargeexchange neutral hydrogen flux to the wall is assessed with the DEGAS 2 Monte Carlo neutral code. The impurity level in the edge plasma and the spatially dependent redeposition fluxes of different impurities are modeled from the multicomponent fluid model using approximate sputtering rates. The fluid results are also compared to the WBC ion Monte Carlo code. The WBC model includes a more detailed sputtering model and kinetic effects that can be important in the low density and nearsurface regions. [Preview Abstract] 

R1.00009: UEDGE Simulation of TripleX Divertors J. Wiley, M. Kotschenreuther, P. Valanju, M. Pekker, T. Rognlien Novel magnetic divertors with additional Xpoints downstream from the main plasma Xpoint have been proposed to overcome reactor heat flux limitations. These divertor designs may allow a fully detached state at the divertor plate  without the poor confinement and disruptive tendencies by avoiding xpoint MARFEs found in conventional divertor magnetic geometries. These new configurations are examined using UEDGE for existing machines that are considering experimental implementation of these divertors: PEGASUS, MAST, and EAST(China’s new longpulse, superconducting tokamak) as well as proposed reactor designs. [Preview Abstract] 

R1.00010: Resistive MHD simulations in support of SSPX E.B. Hooper, B.I. Cohen, L.L. LoDestro, C.R. Sovinec The SSPX spheromak has obtained Btor$>$0.6T, Te=350eV and t(pulse)$\approx $3ms. NIMROD simulations are used to interpret results, guide experiments, and explore upgrades. Voltage spikes during formation and sustainment are interpreted as reconnection across an n=1, negativecurrent layer close to the meanfield xpoint. Field lines are chaotic during these events, causing rapid electron energy loss to the walls; Te$<$50eV in experiment and simulation during strong helicity injection. Sustainment occurs at a high ratio of gun current to bias flux. During slow plasma decay at low gun current, high Te results when magnetic fluctuations are low ($<$1{\%}). If q crosses loworder rational surfaces, islands form causing reduced energy confinement. Fieldlines can become chaotic (Lyapanov length $>$ 4$\pi $R); if they reach walls Te drops to $<$50eV. Changing Zeff=1 to 2.3 (SSPX value) increases ohmic heating and decreases parallel thermal conduction, affecting spheromak evolution. An experimental upgrade to allow bias field reduction following formation may allow increased efficiency operation. [Preview Abstract] 

R1.00011: Application of GTCNeo neoclassical transport code for realistic tokamak cases G. Rewoldt, W.X. Wang, J. Manickam, W.M. Tang The GTCNeo neoclassical transport code [W.X. Wang, et al, Comp. Phys. Commun. 164, 178 (2004)] calculates neoclassical transport quantities for tokamaks, including particle, momentum, and energy fluxes, poloidal velocities, and radial electric fields. It is interfaced with numericallycalculated noncircularcrosssection MHD equilibria. Unlike previous calculations, it includes effects of finite orbit width (banana width), for both standard and nonstandard orbits. Using input data from experimentallyderived TRANSP calculations, the GTCNeo code has now been applied to nine NSTX shots, in both L and Hmodes, and one DIIID shot. The GTCNeo simulations suggest that there may exist nonlocal features in the ion neoclassical transport for NSTX plasmas. There is additional ``nonlocal smoothing'' in the ion heat flux profile. While GTCNeo results are sometimes comparable to standard (NCLASS) neoclassical results, the included finiteorbitwidth effects generally bring the simulated ion heat transport closer to the experimental measurements. For an ITB case, GTCNeo gives a larger electric field peak than NCLASS, at the ITB location. A limitation of the GTCNeo code now is the inclusion only of electrons and one hydrogenic ion species; it is planned to add an impurity species to the GTCNeo calculation in future work. [Preview Abstract] 

R1.00012: Nonlinear stability of rotating plasmas in a mirror geometry A. Y. Aydemir In a previous work, we studied the magnetohydrodynamic (MHD) equilibrium and stability of a mirror plasma in which a strong azimuthal rotation is driven by an externally applied radial electric field$^1$. Although the interchangestabilization through flowshear$^2$ was confirmed, centrifugally confined ``detached states'' obtained in this geometry were found to be linearly unstable to a wide range of other fluid modes driven by the rotation itself. These negative linear stability results left open the question of whether the unstable modes would be nonlinearly stabilized at modest amplitudes or have catastrophic consequences. The goal of the present work is to follow their nonlinear evolution and determine their effect on confinement. \begin{flushleft} \item[$^1$] A. Y. Aydemir, Phys. Plasmas {\bf 11}, 5065 (2004).\\[0.0in] \item[$^2$] YiMin Huang and A. B. Hassam, Phys. Rev. Lett. {\bf 87}, 2350021 (2001). \end{flushleft} [Preview Abstract] 

R1.00013: Dilemma of DriftTearing Modes V. Roytershteyn, B. Coppi, C. Crabtree The theory of the drifttearing mode [1] predicts that in the presence of a realistic transverse electron temperature gradient the mode is stable due to the effects of electron Landau damping or parallel electron thermal conductivity in both collisionless [2] or weakly collisonal [3] regimes typical of modern day experiments on magnetically confined plasmas. The apparent contradiction of this result with the relevant experimental observations calls for consideration of effects outside the scope of conventional linear theory. A radial local ``dip'' in the longitudinal electron thermal conductivity has been shown to restore a significant mode growth rate [4]. A more drastic option is a local flattening of the radial electron temperature profile. We argue that the presence of background shortwavelength microturbulence, associated with Inhomogeneous Electron Temperature (IET) modes can increase the longitudinal ``thermal resistivity'' locally and lower the excitation threshold of drifttearing modes. [1] B. Coppi, \textit{Phys. Fluids}, \textbf{8} 2273 (1965); [2] B. Coppi \textit{et al., Phys. Rev. Letters}, \textbf{42}, 1058 (1979); [3] J. Drake, \textit{et al., Phys. Fluids}, \textbf{25}, 2509 (1983); [4] V.Roytershteyn \textit{et al.} Paper P227, 2005 Sherwood Conference. [Preview Abstract] 

R1.00014: Magnetic topology effects on ion flows Andrei N. Simakov, Peter J. Catto We consider the effect of magnetic topology on the Pfirsch Schl\"{u}ter flows inside the separatrix of a tokamak for reversal in the direction of (i) the plasma current or poloidal magnetic field, (ii) the toroidal magnetic field, or (iii) both; and for (iv) a switch between lower and upper Xpoint operation. We find that the results of the magnetic topology changes on the flows observed in Alcator CMod are consistent with the predictions of neoclassical theory when both the updown symmetric and updown asymmetric drives for toroidal rotation are retained. [Preview Abstract] 

R1.00015: Nonlinearly driven second harmonic of Alfv\'{e}n cascades B. N. Breizman, H. Smith, M. Lisak, D. Anderson In recent experiments on Alcator CMod [J.A. Snipes, et al., Phys. Plasmas \textbf{12}, 056102 (2005)], measurements with Phase Contrast Imaging through the plasma core show a second harmonic of the basic Alfv\'{e}n cascade (AC) signal. The present paper describes a theory that interprets the second harmonic perturbation as a nonlinear sideband produced by the Alfv\'{e}n cascade eigenmode via quadratic terms in the magnetohydrodynamic equations. It is shown that in a lowpressure plasma the nonlinear coupling to compressional Alfv\'{e}n perturbations and acoustic perturbations can be neglected when calculating the second harmonic intensity. The derived expressions for the second harmonic density perturbation can be used together with the experimental measurements to determine the AC amplitude inside the plasma, rather than just at the edge as with magnetic probes. [Preview Abstract] 

R1.00016: Particleincell simulations of electromagnetic turbulence with kinetic electrons Jerome Lewandowski The accurate treatment of electron dynamics in global (toroidal) particleincell simulations is a considerable challenge from the numerical standpoint. The large thermal velocity of the (transit) electrons imposes a stringent condition on the time step for a brute force method. In the electrostatic case, it has been shown that the splitting scheme [1] for the electron dynamics is more accurate, both in the linear and nonlinear regimes, that the conventional perturbative delta f scheme. We present the electromagnetic version of the splitting scheme and specifically discuss the issues of energy and momentum conservation properties, the importance of the initial loading in phase space [2], and the spatial and time resolution requirements.\newline \newline [1] J.L.V. Lewandowski, Physics of Plasmas, 8, 3204 (2003).\newline [2] J.L.V. Lewandowski, Physics Letters A, 313, 291 (2003). [Preview Abstract] 

R1.00017: Pressure Gradient Effects on Alfven Cascade Modes in Tokamaks G.Y. Fu, H.L. Berk Alfven cascade modes are discrete shear Alfven eigenmodes localized at the radius of minimum of safety factor in tokamak plasmas with reserved shear q profiles [1]. The mode frequency is given by $\omega \sim (n m/q_{min})V_A/R$ over most parameters, and transforms to the geodesic acoustic mode near rational field lines. The mode is seen in experiments, where the mode frequency sweeps up as q drops. Numerical results indicate that the plasma pressure gradient helps establish the mode [2], in contrast to a previous analytic prediction [3] that the pressure gradient term hinders mode establishment. here a modification of the analysis is developed to include a previously neglected interchange term due to the favorable average curvature of a tokamak. This is the key addition that is needed for the pressure gradient to be favorable for the establishment of a cascade mode, and thereby explain the numerical results. \newline [1] H. L. Berk et al., Phys. Rev. Lett. {\bf 87}, 185002 (2001). \newline [2] G. J. Kramer et al., Plasma Phys. Controlled Fusion {\bf 46}, L23 (2004). \newline [3] B. N. Breizman et al., Phys. Plasmas {\bf 12}, 112506 (2005). [Preview Abstract] 

R1.00018: Phase space gradient driven descrete compressional Alfven eigenmodes in NSTX and DIIID Nikolai Gorelenkov, Eric Fredrickson, William Heidbrink The spectrum of Compressional Alfv\'{e}n Eigenmodes (CAE) is analyzed and shown to be discrete in tokamaks with low aspect ratio, such as NSTX, as well as in the DIIID. The study is focused on recent similarity experiments on NSTX and DIIID in which subcyclotron frequency instabilities of CAEs were observed at similar plasma conditions. The discrete spectrum of CAEs is characterized by three mode numbers $(M,S,n)$, where $M$, $S$, and $n$ are poloidal, radial and toroidal mode numbers, respectively. Expected mode frequency splitting corresponding to each of these mode numbers seem to be observed in experiments and is consistent with our numerical analysis. The polarization of the observed CAE magnetic field oscillations in NSTX was measured and also consistent with the numerical analysis, which helps to identify this activity as CAEs. CAE mode structure was simulated to be localized in both radial and poloidal directions with typical radial localization towards the plasma edge and poloidal localization at the low field side of the plasma cross section. [Preview Abstract] 

R1.00019: On Heat Loading, Divertors, and Reactors Michael Kotschenreuther, Prashant Valanju, Swadesh Mahajan, James Wiley We show that the relatively low thermal power handling capacity of the standard divertors (used in current as well as projected machines) forces extremely high ($\sim $95{\%}) radiation fractions f$_{Rad}$ in power reactors with characteristically large heating powers (much larger than ITERFEAT). Independent of how one apportions this radiation (in the SOL or in the core), such high values of f$_{Rad}$ have profound and deleterious consequences on the core confinement and stability to the extent that a high power hypothetical reactor operating with the standard divertor will not be able to meet the daunting confinement requirements. Even operation in the ITB mode could not lead to a dependable power reactor with acceptable economics. By designing a divertor with a considerably enhanced thermal capacity (through a flaring of the field lines) we have proposed a way out of the disabling core confinement and stability problems caused by high f$_{Rad}$. We suggest a possible class of experiments which could lay the foundation for an efficient and attractive path to practical fusion power. [Preview Abstract] 

R1.00020: Computing Coherent Structures with ChebyshevFourier Pseudospectral Techniques in Confinement Systems J.C. Perez, W. Horton, R. Dahlburg Chebyshevtau pseudospectral methods have been widely used for decades in the linear and nonlinear simulations of neutral fluid dynamics. In this work, we apply these techniques to different reduced models of fluid like plasma equations that describe various instabilities commonly present in many plasma confinement configurations, ranging from laboratory to space plasmas. Nonlinear highresolution simulations are performed for a plasma slab, periodic in one direction and satisfying Dirichlet boundary conditions in the other. As opposed to FourierFourier methods, usually applied to homogeneous problems, the ChebyshevFourier method allows for the study of equilibrium states that are inhomogeneous along one direction and have Dirichlet, Neumann or Robin boundary conditions. Adaptive fifth/sixth order RK time integration scheme is used to advance the initial condition. Simulations show the formation of longlived coherent structures from different equilibrium states with a random noise initial perturbation. The morphologies of the structures obtained include mushrooms, associated to the RayleighTaylor Instability, KelvinHelmholtz vorticity rollup, streamers and blobs. The simulations examples are in conexion to shear flow experiments in the LArge Plasma Device. [Preview Abstract] 

R1.00021: Nonlocal Property of a HallMHD Contact Discontinuity Eliezer Hameiri A contact discontinuity may model a transport barrier or a plasmavacuum interface. One outstanding question concerning such a discontinuity is whether, in a twofluid plasma, the electron fluid is allowed to cross the discontinuity even if the ion fluiid does not (because of the ``contact'' nature). Indeed we find that such a situation is possible in HallMHD, implying that the discontinuity problem is a global problem, where in order to preserve charge neutrality in the volume bounded by the contact discontinuity, electrons leaving the volume at one point have to be compensated for by electrons crossing in the opposite direction at another point. We carry out a full linear treatment of a toroidal plasma, deriving also stability criteria that conflict with some previous results\footnote{U. Schaper, J. Plasma Phys. {\bf 30}, 169 (1983).}$^{,}$\footnote{Rosenau et al., J. Plasma Phys. {\bf 21}, 385 (1975).} which ignored the issue of nonlocality and its implication for the appropriate jump conditions. [Preview Abstract] 

R1.00022: TripleX Divertor Coil Designs for EAST, PEGASUS, MAST, and Reactors Prashant Valanju, Michael Kotschenreuther, James Wiley, Mikhail Pekker, William Rowan, Huang He Novel magnetic divertor with additional Xpoints downstream from main plasma Xpoint have been proposed to overcome reactor heat flux limitations. PEGASUS, MAST, and EAST(China's new longpulse, superconducting tokamak) are considering experimental implementation of these divertors. MHD equilibria, optimized coil designs, sensitivity to plasma motion, stresses, and heating will be presented for these machines as well as for some reactor designs. [Preview Abstract] 

R1.00023: Bicubic Bezier patches and finite element method for nonlinear MHD codes. Olivier Czarny, Guido Huysmans For the numerical simulation of Edge Localised Modes, the presence of a separatrix (Xpoint) plays a important role for the relevant MHD instabilities i.e. external kink modes and ballooning modes. To investigate the MHD stability in plasmas with a separatrix, a new nonlinear MHD code named JOREK is under development which treats both the closed field lines inside the separatrix and the open field lines outside. The current version of the code solves reduced MHD equations, using generalized finite elements which allow flexibility in the plasma geometry. Moving to more complete equations needs optimization of the code efficiency as far as memory is concerned, that is, decreasing the number of degrees of freedom required for a given accuracy. We have developed an approach based on bicubic Bezier surfaces which are commonly used in Computed Aided Design. This approach differs from Hermite's method in that it provides geometric continuity (G$^{1})$ while Hermite's formulation imposes more restrictive parametric continuity (C$^{1})$. As a consequence, Bezier formalism makes it easier to implement a grid refinement strategy ($h$ adaptivity). Furthermore the method ensures continuous gradients of physical variables. We present some results from 2D MHD codes (Soloviev equilibrium, reduced MHD) in order to illustrate both validity and advantages of the approach. [Preview Abstract] 

R1.00024: Multiply Resonant Resistive Stability in DIIID Plasmas D.P. Brennan, A.D. Turnbull, M.S. Chu, L.L. Lao, L.E. Sugiyama MHD stability of resistive modes in the presence of multiple resonant surfaces, including central sawtooth oscillations, is examined using reconstructions of experimental equilibria in DIIID. Coupling to other rational surfaces, especially the 1/1, is important even at low beta. The outer ideal MHD and inner tearing layer solutions are important in determining mode stability. The PEST3 code is used to determine matrix solutions for the ideal MHD n=1 mode that has singular jumps at each rational surface. This outer region matrix of solutions is matched asymptotically to the resistive MHD inner layer solutions, where the equilibrium configuration differs significantly in high and low beta plasmas. The most important effects in the dispersion relation are the resistive interchange parameter D$_{R}$ and the coupling to the 1/1 surface. Twofluid diamagnetic effects were examined in the uncoupled case, and modify the growth rates significantly. Electron and ion diamagnetic effects are important at large diamagnetic frequencies. [Preview Abstract] 

R1.00025: Ray tracing for ballooning modes in quasisymmetric stellarators E. Mondloch, A. S. Ware, R. Sanchez, D. S. Spong, D. delCastilloNegrete The ray tracing techniques introduced by Dewar and Glasser [R. L. Dewar and A. Glasser, Phys. Fluids {\bf 26}, 3038 (1983)] are used to examine global ballooning stability for three different quasisymmetric stellarator equilibria: the quasipoloidally symmetric QPS, the quasihelically symmetric HSX, and the quasi axisymmetric NCSX. In the ray tracing method, global ballooning mode stability is calculated by following rays in the eigenvalue space determined by the results of local, infinite $n$ ballooning theory. For all three of these configurations, the unstable structures are of the localized, ballooning type and are limited to narrow bands of field lines. This is true even well above a marginal stable $\beta$. The range of $alpha$ (where $\alpha$ is the field line label) for which unstable surfaces are found is broader in QPS than in NCSX while the range of $\theta_{k}$ (where $\theta_{k}=k_{q}/k_{\alpha}$ is the ballooning parameter) for which unstable surfaces are found is narrower in QPS than in NCSX. For HSX, the weak global shear results in modes which only weakly depend on the ballooning parameter, $\theta_{k}$. This weak dependence makes the ray tracing for HSX challenging. [Preview Abstract] 

R1.00026: Large Turbulent Transport of Alpha Particles in Reactor Plasmas C. EstradaMila, J. Candy, R.E. Waltz The study of energetic particle transport in fusion plasmas has been largely confined to processes connected with MHD oscillations, whereas the effect of core microturbulence on alpha particle transport has received little attention. Indeed, the \textit{conventional wisdom} is that fast particles do not interact with smallscale perturbations because of gyroradius and drift averaging effects. In this poster we present a systematic study of the behavior of energetic species in ITER. Using gyrokinetic simulations from the GYRO code [1,2], we found that alpha particles interact strongly with core ITG turbulence. The most surprising finding of this work is that the fluxes per particle of alphas can be stronger than the main ion fluxes counterpart, as opposed to \textit{conventional wisdom} where species with large gyroradii do not interact with the turbulence. \newline \newline [1] J. Candy and R.E. Waltz, J. Comput. Phys. \textbf{186}, 545 (2003).\newline [2] J. Candy and R.E. Waltz, Phys. Rev. Lett. \textbf{91}, 45001 (2003). [Preview Abstract] 

R1.00027: Quasilinear MHD model to determine beta and energy confinement time in a hardcore Zpinch magnetic configuration Alexei Kouznetsov, Jeffrey Freidberg, Jay Kesner The energy confinement time of plasma is a critical figure of merit for any magnetic configuration. In addition to the magnetic configuration itself, energy confinement depends on experimentally controlled parameters such as the edge conditions and the shape of the heating profile. This paper deals with the hardcore Zpinch magnetic configuration, which can be considered to be an approximation to a large aspect ratio levitated dipole. We assume classical transport in the MHD stable region and carry out quasilinear diffusion analysis in the unstable region. Using quasilinear approximation, we analytically showed that a violation of the MHD stability condition results in enhanced particle and energy transport, which brings pressure profile back to marginal stability and forces particle density to be linearly proportional to $\oint {\frac{d\ell }{B}} $. Selfconsistent numerical calculation of the density and pressure profiles allowed us to determine energy confinement time as the experimental parameters are varied. The resulting power law for beta and energy confinement time is discussed. [Preview Abstract] 

R1.00028: Bootstrap current in optimized stellarators A.S. Ware, D.A. Spong, L.A. Berry, S.P. Hirshman, J.F. Lyon This work examines bootstrap current and its impact on the equilibrium properties in optimized stellarators. Two independent methods are used to calculate the bootstrap current: a fast code based on a calculation in an asymptotically collisionless limit [K. C. Shaing, {\it et al.}, Phys. Fluids B {\bf 1}, 148 (1989)] and a fluid moments approach that self consistently calculates the neoclassical transport coefficients, including the bootstrap current [D. A. Spong, Phys. Plasmas {\bf 12}, 056114 (2005)]. The bootstrap current calculations from the two codes were done for low density, ECHheated and high density, ICHheated plasmas. In the configurations examined here, namely, the QuasiPoloidal Stellarator (QPS), the National Compact Stellarator Experiment, the Helically Symmetric Experiment (HSX), the Large Helical Device, and the Wendelstein 7X Stellarator (W7X), the bootstrap currents predicted from the two codes agree qualitatively for both ICH and ECH profiles. A selfconsistent bootstrap current results in a negligible increase in the rotational transfrom for W7X, an increase in the rotational transform for QPS, and a larger decrease in the rotational transform for HSX. [Preview Abstract] 

R1.00029: The highfrequency gyrokinetic model. Roman Kolesnikov, W.W. Lee As demonstrated earlier [1], the linear gyrokinetic formulation for $\rho /L_B \ll 1$ can be generalized to include the high frequency ion cyclotron waves, where $\rho $ is the ion gyroradius and $L_B $ is the scale length of the ambient magnetic field. In this paper, we present an extended nonlinear $\delta f$ gyrokinetic particle simulation model that can be used to study tokamak physics in the arbitrary frequency regime. The model is based on the separation of the ion gyromotion from its gyrocenter motion, and it is fully equivalent to the original Lorentzian description for $\rho /L_B \ll 1$. As such, the original Vlasov equation can be divided into a gyrophase independent part and a gyrophase dependent part. For the latter, we have developed a numerical scheme to simulate the fast ion gyromotion as well as the polarization effects in the electrostatic limit. The numerical properties of this new gyrokinetic formulation resulting from the separation of time scales between gyromotion and gyrocenter motion will be reported. The comparisons of the simulations for Bernstein harmonics between the conventional VlasovPoisson scheme and the new high frequency gyrokinetic model will also be discussed. \newline \newline [1] H. Qin, W. M. Tang, W. W. Lee, and G. Rewoldt, Phys. Plasmas 6, 1575 (1999). [Preview Abstract] 

R1.00030: Gyrokinetic simulations of magnetic reconnection Paolo Ricci, Barrett Rogers, William Dorland, Tomo Tatsuno We present linear and nonlinear simulations of magnetic reconnection in a simple slab geometry using the GS2 code. The GS2 code treats both the electrons and the ions gyrokinetically, and includes effects such as trapped particles and the outofplane magnetic field perturbations due to finite plasma beta. We show numerical convergence studies in both the linear and nonlinear cases, and compare the GS2 results to those obtained using a simple twofluid model. We address the dependence of the reconnection rate on the iontoelectron temperature ratio, the plasma beta, the simulation box geometry, and the mass ratio. [Preview Abstract] 

R1.00031: Impact of the Reynolds Stress on Edge Poloidal Flow Generation N. D. Daniels, A. S. Ware, B. A. Carreras, D. E. Newman, C. Hidalgo A onedimensional transport model is used to study the impact of the form of the Reynolds stress on edge poloidal flow generation during gas puffing experiments. Gas puffing at the edge of the TJII stellarator has been used to control the development of an edge poloidal velocity shear layer [C. Hidalgo, {\it et al.}, Phys. Rev. E {\bf 70}, 067402 (2004)]. In this work, a numerical transport model is used to examine for hysteresis in the development of an edge poloidal velocity shear layer due to a modeled gas puff. The transport model [D. E. Newman, {\it et al.}, Phys. Plasmas {\bf 5}, 938 (1998)] couples together density, ion temperature, electron temperature, poloidal flow, toroidal flow, radial electric field, and a fluctuation envelope equation which includes a shearsuppression factor and now implements a modified RungeKutta with adaptive time stepping. Two different models of the Reynolds stress generation of poloidal flow are examined. The first model requires a gradient in the product of the sqare of the fluctuation amplitude and the radial electric field shear for the generation of flow. The second model requires only a gradient in the radial electric field. Both models are tested for parameters consisting with the TJII experiment. The impact on flow generation is discussed. [Preview Abstract] 

R1.00032: Deltaf particleincell simulation of XB mode conversion N. Xiang, J.R. Cary, D.C. Barnes, J. Carlsson Lownoise, deltaf particleincell algorithm has been implemented in VORPAL, a massive parallel, hybrid plasma modeling code (Chet Nieter and John. R. Cary, J. Comp. Physics 196, 448 (2004)). This computation method allows us to simulate the mode conversion between the extraordinary wave (X) and electron Bernstein wave (EBW) in both linear and nonlinear regimes. In the linear regime, it is found that a full XB mode conversion can be obtained for optimized parameters as $\omega/\omega_{ce} <2$ ($\omega$ is the driving frequency and $\omega_{ce}$ is the electron cyclotron frequency). No 100\% conversion is found for $\omega/\omega_{ce} $ moderately larger than 2. The simulation results agree with the predictions of Ram's theory (Ram \& Schultz, Phys. Plasma 4084 (2000)). The agreement indicates that XB mode conversion can be well described by the quadratic wave equation based on cold plasma approximation, and this is consistent with the phasespace picture of mode conversion. It is also shown that the conversion efficiency is significantly affected by the gradient of magnetic fields. When the amplitude of the incident X wave increases, it is shown that the nonlinear selfinteraction of the electron converted EBW gives rise to the second harmonic generation at a pump power as low as three orders smaller than the electron thermal energy. If the fundamental EBW is sufficiently large, the nonpropagating third and fourth harmonic modes are also generated. *The work was supported by DOE Contract No.DEFG0204ER54735. [Preview Abstract] 

R1.00033: Spontaneous tearing instability of m=0 modes in the RFP V.V. Mirnov Standard RFP discharges in the Madison Symmetric Torus (MST) exhibit cyclic sawtooth oscillations associated with core (m=1, n=6,7) and edge (m=0, n=1) resonant tearing modes. It is believed that the core tearing modes are spontaneously unstable while linearly stable m=0 modes are nonlinearly driven by coupling to core resonant modes. This scenario of forced m=0 magnetic reconnection is based on robust linear stability properties demonstrated in the past by various $\Delta ^{\prime }$ calculations. These earlier results have indicated that the m=0 tearing mode is mainly stable. Recent MST experiments have shown[1] that in some regimes with improved plasma confinement the m=0 mode becomes linearly (spontaneously) unstable. This motivated our interest in revisiting the m=0 tearing mode analysis including a broader range of current profiles. We introduced a threeparameter cylindrical model which permits to vary the radial position and the width of the current gradient independently and found a wide class of unstable current profiles. We report on ideal MHD $\Delta ^{\prime }$ analysis as well as the results obtained from a cylindrical resistive eigenvalue code. [1] S.H.Choi et al., submitted to Phys. Rev. Lett. [Preview Abstract] 

R1.00034: Kinetic simulation of burning plasmas Giovanni Lapenta Burning plasmas pose new challenges to the fusion theory community. The presence of hot alpha particles generated by fusion reactions introduces new scales and new processes not important in conventional plasmas. Particularly challenging is the fact that the gyroradius of alpha particles can become significant and require a more carefull analysis. For example, in ITER the regular ions at 10keV will have a gyroradius of the order of a tenth of a centimiter, but the alpha particles generated at 3.5MeV will have a gyroradius of 10cm. This scale is no longer small compared to may important processes developing in a fusion device (e.g. neoclassical tearing islands). Therefore many of the approximations we are accustomed to, will no longer be accurate. We present here an approach that is ideally suited to study alpha particles in burning plasmas: the implicit moment kinetic particle in cell method implemented in the code CELESTE. We discuss the method and its aplication to burning plasmas. [Preview Abstract] 

R1.00035: Current and potential distribution in a divertor with toroidallyasymmetric biasing of the divertor plate D.D. Ryutov, R.H. Cohen, G.F. Counsell, P. Helander Toroidallyasymmetric biasing of the divertor plate may increase convective crossfield transport in SOL and thereby reduce the divertor heat load. Experiments performed with the MAST spherical tokamak generally agree with a simple theory of nonaxisymmetric biasing. However, some of the experimental results have not yet received a theoretical explanation. In particular, existing theory seems to overestimate the asymmetry between the positive and the negative biasing. Also lacking a theoretical explanation is experimentally observed increase of the average floating potential in the main SOL in the presence of biasing. We attempt to solve these problems by accounting for the closing of the currents (driven by the biasing) in a strongshear region near the Xpoint. We come up with a picture which, at least qualitatively, agrees with these experimental results. Work performed for the US DOE by UC LLNL under contract W7405Eng48; work at Culham jointly funded by the UK Dept. of Trade and Ind. and Euratom. [Preview Abstract] 

R1.00036: Reduced twofluid equations for plasma dynamics on the diamagnetic drift scale. Jesus J. Ramos A reduced system of finiteLarmorradius twofluid equations is derived, based on the ``paraxial'' or ``longthin'' approximation, namely a largeaspectratio and longparallelwavelength ordering for plasmas in a strong guide magnetic field of weak curvature. The main new features are the full account of diamagnetic effects associated with temperature gradients and the allowance for strong pressure anisotropies, with dynamically evolved ion and electron parallel and perpendicular pressures. A slow dynamics ordering is assumed, whereby flow velocities and time derivatives are respectively comparable to the diamagnetic drift velocities and frequencies. Arbitrary threedimensional background geometries are considered, but the analysis is later specialized to the tokamakrelevant case of an axisymmetric background. The final reduced system takes into account all the twofluid effects associated with the Hall physics in the generalized Ohm's law, the ion gyroviscosity, the ion and electron pressure anisotropies (sometimes called parallel viscosities) and the diamagnetic perpendicular heat fluxes, within the assumed orderings. The parallel heat fluxes do not contribute to these lowestorder reduced equations by virtue of the largeaspectratio and smallparallelgradient orderings, with the result that the system is consistently closed except for the collisional terms. [Preview Abstract] 

R1.00037: On transport barriers in a nontwist map model of a reversed magnetic shear tokamak with ergodic magnetic limiter Alexander Wurm, Kathrin Fuchss, P.J. Morrison 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] We investigate the effect of this perturbation on the resilience of transport barriers and separatrix reconnection scenarios that have been studied extensively in the case of the standard nontwist map.\newline \noindent $[1]$ K. Ullmann and I.L. Caldas, Chaos, Solitons and Fractals, {\bf 11}, 2129 (2000)\newline $[2]$ J.S.E. Portala, I.L. Caldas, R.L. Viana, and P.J. Morrison, preprint (2005). [Preview Abstract] 

R1.00038: Multimode waveparticle interactions and the quasilinear transition Roderick Vann, Boris Breizman Multiple mode interactions are ubiquitous in fusions plasmas. In the generic kinetic picture, the excitation of waves leads to the formation of potential wells corresponding to islands in phase space in which some of the particles are trapped. Island coalescence may lead to energy avalanche across a large phase space region. In the limit that modes are far apart (i.e. their island widths are much less than the mode separation), the particle dynamics of the modes can be treated independently; if there are many modes close together, the quasilinear approximation applies and multimode interactions may be treated as a diffusion in velocity space. We consider the intermediate regime of several modes whose island widths are comparable to their separation and investigate under what conditions the modes interact. Our Vlasovian model equations allow for an arbitrary number of modes which couple solely through the spatiallyaveraged component. The equations are integrated via a timesplitting algorithm which calculates the advective terms using the Piecewise Parabolic Method. The code has already successfully been applied in the single mode case (e.g. to study mode chirping); it is extended to handle multiple modes via a Fourier representation in velocity space. In this Poster we introduce the numerical algorithm and present preliminary results of multimode coupling. This work was funded in part by Euratom and the UK EPSRC. [Preview Abstract] 

R1.00039: Effects of short wavelength turbulence associated with inhomogeneous electron temperature modes Kevin Takasaki, Bruno Coppi, Chris Crabtree, Vadim Roytershteyn The background short wavelength turbulence that is generated by modes associated with the combined effects of magnetic field and electron temperature gradient is shown to be relevant to three important physical issues. First, due to an enhanced ``thermal resistivity'' along the magnetic field lines, drifttearing modes may become unstable in weakly collisional or collisionless plasmas. Second, in the central region of the plasma column the short wavelength modes can produce a particle inflow, which in the outer region of the plasma column can be explained by the finite electron collisional thermal conductivity [1]. Finally, the influence of the different topologies that the considered modes can have on magnetic reconnection at the microscopic scale is pointed out. [1] B. Coppi and C. Spight, \textit{Phys. Rev. Lett.} \textbf{41}, 551 (1978). [Preview Abstract] 

R1.00040: Transport bursts in simulations of tokamak edge turbulence Robert Kleva, Parvez Guzdar The character of particle and energy transport in simulations of tokamak edge turbulence is determined by the magnitude of the density gradient. Edge turbulence becomes increasingly intermittent as the edge density gradient increases. Beyond a critical limit in the edge density gradient, the transport is dominated by short, repetitive bursts of particles and energy outward toward the wall. These bursts are extremely ballooning in character, strongly localized on the large major radius side of the torus. The duration of a burst is of the order of the ballooning growth time $t_0 = (R L_n)^{1/2} /c_s$, where $c_s$ is the sound speed, $R$ is the major radius of the torus, and $L_n$ is the density gradient scale length. With further increases in the edge density gradient, the fluxes of energy and particles in the bursts become larger in magnitude. The particle and energy bursts seen in the simulations are similar to the bursts in $D_\alpha$ radiationseen during edge localized modes (ELM's) in tokamaks. [Preview Abstract] 

R1.00041: Successes of the ``Accretion Theory'' for the Spontaneous Rotation Phenomenon and Relevent Theoretical Issues J. Thomas, B. Coppi A considerable series of experiments have shown evidence for the key elements of the ``Accretion Theory'' [1,2] of the Spontaneous Rotation Phenomenon in axisymmetric plasmas with rather diverse magnetic confinement configurations (tokamaks with and without divertors, RFP's, etc.). These elements are: i.) angular momentum is ``ejected'' toward the material wall surrounding the plasma; ii.) angular momentum of the opposite sign is transported from the edge of the plasma column toward the center; iii.) rotation is strongly affected by the physical regime and the magnetic configuration of the outer region of the plasma column; iv.) rotation is inverted in the transition from the Lregime to a good ion confinement regime; v.) the phase velocities of the mode excited near the edge are inverted in this transition. In the good ion confinement regime the edgemodes that scatter angular momentum to the wall are expected to have phase velocities in the direction of the electron diamagnetic velocity while the modes transporting angular momentum toward the center from the edge have opposite phase velocities. Experimental observations have also confirmed this expectation. [1] B. Coppi, \textit{Nucl. Fus.} \textbf{42}, 1 (2002). [2] B. Coppi, MITRLE Report PTP 02/05, Cambridge 2002 [Preview Abstract] 

R1.00042: Single helicity and quasisingle helicity states in RFPs Gian Luca Delzanno, Luis Chacon, John M. Finn We present a systematic study of single helicity (SH) states and quasisingle helicity (QSH) states in RFPs. We begin with cylindrical paramagnetic pinch equilibria with uniform resistivity, characterized by a single dimensionless parameter proportional to the toroidal electric field, or the RFP toroidal current parameter $\Theta$. For suficiently high $\Theta$, there are several unstable $m=1$ ideal MHD instabilities, typically one of which is nonresonant, with 1/n just above $q(r=0)$. We evolve these modes nonlinearly to saturation for low Hartmann number H. We then obtain the $m=k=0$ quasilinear profiles, which typically have toroidal field reversal, and study their stability. For typical cases, these profiles may remain unstable to tearing modes, but only for sufficiently high $H$. For lower $H$ these states are stable. We show results indicating the proximity of these thresholds to the thresholds between SH and QSH behavior. [Preview Abstract] 

R1.00043: Effect of parallel electric field on ion heating in RFPs. Vladimir Svidzinski, Vladimir Mirnov, Stewart Prager Strong ion heating is observed in the reversed field pinch (RFP). During a sawtooth crash in the Madison Symmetric Torus RFP the ion temperature can spontaneously double in 100 microseconds. It is also observed that high Z impurities are heated stronger than bulk ions. The possibility of ion heating due to tearing instabilities is examined. Our previous study examined the heating due to viscous damping of strongly localized perpendicular flows existing in the vicinity of resonant surface in tearing mode. Here we present the results due to the parallel electric fields in the tearing mode. We estimate the parallel electric field in the vicinity of resonant surface from the two fluid equations in which the electric field is mainly balanced by the parallel pressure gradient. The perturbed pressure profile is found from the cylindrical tearing eigenmode in resistive MHD approximation. The ion heating in the electric field with the parallel gradient is estimated from numerical solution of kinetic equation with Landau collision operator. The potential energy of high Z impurities in such a field can exceed their thermal energy, thus the effective heating is expected. [Preview Abstract] 

R1.00044: Breakup of shearless tori in the standard nontwist map Kathrin Fuchss, Alexander Wurm, P. J. Morrison The standard nontwist map is a simple model for degenerate Hamiltonian systems that describe, e.g., magnetic field lines in toroidal plasma devices with reversed magnetic shear profile. As a numerically easily accessible system, this map can be used to gain understanding of basic field line features, such as the breaking of transport barriers represented by shearless invariant tori. Breakup of several sample tori with noble winding numbers have been studied in the past.[1] Here, for a sequence of noble tori, tori breakup is investigated systematically, in order to gain insight into how the breakup of different tori are interrelated and whether the sequence can describe the breakup of non noble tori as a limiting case.\\  [1] D.~DelCastilloNegrete, J.~M. Greene, and P.~J. Morrison, Physica D {\bf 100}, 311 (1997); A.~Apte, A.~Wurm, and P.~J. Morrison, Physica D {\bf 200}, 47 (2005); K.~Fuchss, A.~Wurm, A.~Apte, and P.~J. Morrison, preprint/submitted to Chaos (2006). [Preview Abstract] 

R1.00045: Propagation of global shear Alfven waves in gyrokinetic tokamak plasmas Y. Nishimura, Z. Lin, I. Holod, L. Chen, V. Decyk, S. Klasky, K. Ma, M. Adams, S. Ethier, T. Hahm, W. Lee, J. Lewandowski, G. Rewoldt, W. Wang Employing the electromagnetic gyrokinetic simulation models,\footnote{W.W.Lee {\it et al.}, Phys. Plasmas {\bf 8}, 4435 (2001).}$^{,2}$ Alfven wave dynamics in global tokamak geometry is studied. Based on a small parameter expansion by the squareroot of the electronion mass ratio, the fluidkinetic hybrid electron model\footnote{Z.Lin and L.Chen, Phys. Plasmas {\bf 8}, 1447 (2001).} solves the adiabatic response in the lowest order and solves the kinetic response in the higher orders. We verify the propagation of shear Alfven waves in the absence of drives or damping mechanisms by perturbing the magnetic field lines at $t=0$ in a global eigenmode structure. The Alfven wave experiences continuum damping.\footnote{J.A.Tataronis and W. Grossman, Z. Phys. {\bf 14}, 203 (1973).} In the presence of energetic particles, excitations of toroidal Alfven eigenmode (TAE) is expected within the frequency gap.\footnote{C.Z.Cheng, L.Chen, and M.S.Chance, Ann.Phys. {\bf 161}, 21 (1984).} With the $\eta_i$ gradient drive, at a critical $\beta$ value, the kinetic ballooning mode (KBM)\footnote{C.Z.Cheng, Nucl. Fusion {\bf 22}, 773 (1982).} is excited below the ideal MHD limit. [Preview Abstract] 

R1.00046: Progress in Gyrokinetic Particle Simulation of Electron Transport in Fusion Plasmas Zhihong Lin Electron thermal transport driven by electrostatic driftwave turbulence in tokamak plasmas is studied using full device gyrokinetic particle simulations. Trapped electrons are found to enhance ion temperature gradient (ITG) turbulence by mostly not responding to the ITG modes and thus induce relatively low level of electron transport. On the other hand, resonant excitation of trapped electron mode (TEM) turbulence leads to large electron thermal and particle transport. TEM modes have much broader linear spectrum and the nonlinear saturation is characterized by twostep processes. Shorter wavelength modes saturate first and induce high electron thermal transport but relatively small ion transport; longer wavelength modes saturate later and induce higher ion thermal and particle transport. [Preview Abstract] 

R1.00047: Observations from the CDX Nonlinear Sawtooth Study J. Breslau, W. Park, S. Hudson, S. Jardin, H. Strauss We present two separate sets of observations from modeling sawteeth in the CDX tokamak with the M3D code [1] as part of a crosscode benchmark. One is that, in addition to the internal kink, the starting equilibrium is linearly unstable to a range of highn resistive ballooninglike modes [2], which can only be suppressed by the assumption of extremely high perpendicular heat transport. There is evidence that such transport is present in CDX itself, possibly induced by the edge modes [3], which would thereby saturate nonlinearly. Analysis of field line stochasticity as a mechanism for this saturation will be presented. The second topic is the finding that the sawtooth, though fundamentally a 1,1 mode, has considerable structure in the toroidal direction which is not easily resolved even with the retention of tens of mode numbers in the nonlinear run. The demands of a convergence study are therefore more stringent than might at first be supposed; implications for the development of predictive capability are discussed. [1] W. Park et al., Phys. Plasmas 6, 1796 (1999). [2] H.R. Strauss. Phys. Fluids 24, 2004 (1981). [3] B.A. Carreras and P.H. Diamond, Phys. Fluids B 1, 1011 (1989). [Preview Abstract] 

R1.00048: Implicit PIC Studies of MHD Instabilities D.C. Barnes, W.D. Nystrom We are studying the gravitationally driven interchange (gmode) with implicit PIC. In addition to full implicit PIC, we also use an implicit hybrid approach with electrons described by fluid equations, and full, Lorentz force ion orbits. We have also implemented a deltaf approach (QIP). The models are described in detail and numerical properties considered. Conservation laws are shown to hold for appropriate time centering. We examine the effects of iterating the particles in concert with the moment equations, in contrast with the standard approach of using the moment equations only for the field solve. Implicit systems are solved with Krylov methods (GMRES) with 1 or 2D preconditioning matrices. Preliminary results for the gmode will be presented. [Preview Abstract] 

R1.00049: Selfsustaining vortex perturbations in smooth shear flows Juhyung Kim, Jean C. Perez, Wendell Horton, George D. Chagelishvili, R. G. Chanishvili, J.G. Lominadze, John C. Bowman The nonlinear dynamics of coherent cyclonic and anticyclonic vortices in plane flow with constant shear is investigated numerically using a Fourier pseudospectral code. The flow is asymptotically linearly stable, but is highly nonnormal, allowing transient perturbations to gain energy from the background shear flow. This linear transient growth interplays with nonlinear processes and can lead to change the asymptotic behavior. We show that a fixed background shear flow can maintain finite amplitude cyclonic vortices indefinitely in time through a positive feedback mechanism between the nonlinear interactions and the external shearing of the vortex flow. A plasma laboratory experiment is suggested based on the results of this investigation. [Preview Abstract] 

R1.00050: Ignited Spherical Tokamaks and their supercritical regime Leonid Zakharov The LiWall concept, which is now completed, and based on it Ignited Spherical Tokamaks (IST) for developing a fusion power reactor is outlined. With a central fueling of the plasma by the neutral beam injection and with pumping boundary conditions the temperature profiles inside the plasma will be automatically flattened, thus eliminating the major channel of energy loss due to the iontemperature gradient instability. Such a property would change the entire approach to tokamak magnetic fusion and make it consistent with the power reactor development. The selfconsistency of the LiWall concept (only 7 years old) and resulting IST, in terms of stability (both internal and freeboundary), confinement, high power density, fueling, external control of the density and bootstrap current, and power extraction is discussed. The unique combination of the small size of IST, large Shafranov shift and a good confinement exceeding what is necessary for ignition would constitute a new, supercritical ignition (SCI) regime, which significantly simplifies the physics and the design of IST and the way to the power reactor. [Preview Abstract] 

R1.00051: Twodimensional simulations of the inertial electrostatic confinement device Alberto Marocchino, Giovanni Lapenta, Evstati Evstatiev, Richard Nebel, Jaeyoung Park We discuss the application of the CELESTE simulation package to the simulation of the experiments conducted at the Los Alamos Inertial Electrostatic Confinement (IEC) device. Recently considerable experimental advances have been made in understanding of the stability of the virtual cathode and in the physics of POPS. This momentous experimental advance requires a new simulation effort for explaining the new experimental findings, particularly in the area of stability of the configurations obtained experimentally. We have conducted a 2D stability study of the virtual cathode in the IEC device using the DEMOCRITUS package. DEMOCRITUS is a 2D general geometry electrostatic PIC code. In the present study we have done complete stability study and investigate the twostream instability occuring in the IEC device. [Preview Abstract] 

R1.00052: Analytically and numerically computed tokamak equilibria at unity beta Russell Neches, Steven Cowley, PierreAlexandre Gourdain, JeanNoel Leboeuf The characteristics of near unity$\beta$ equilibria are investigated with two codes. CUBE is a multigrid GradShafranov solver, and ACUBE was written to compute solutions using analytic unity$\beta$ equilibria [S.C. Cowley {\em et. al.}, 1991]. Results from each method are quantitatively compared in several distinct equilibrium conditions. These comparisons corroborate the theoretical results and provide benchmarks for highresolution numerical results available from CUBE. These tools facilitate exploration of many properties of high$\beta$ equilibria, such as a highly diamagnetic plasma and its ramifications for stability and transport as $\beta$ approaches unity. [Preview Abstract] 

R1.00053: Progress and plans for the PTRANSP project Stephen Jardin, LongPoe Ku, Charles Kessel, Doug McCune, Holger St. John, Linda Lodestro, Glen Bateman, Arnold Kritz We describe progress on a twoyear multiinstitutional project to perform a significant upgrade of the TRANSP code by implementing several new predictive capabilities. The product will be an integrated predictive transport code that is fully coupled to the UEDGE edge transport code and to a number of existing MHD equilibrium and stability codes and transport models. This capability will be of immediate benefit to the U.S. ITER physics team by providing a unique advanced ITER discharge simulation capability. It will also provide opportunities for collaboration and code sharing with our international partners. Progress to date has been made in the areas of extracting utilities from the TRANSP code that can be accessed by an external driver. The utility XPLASMA is being used to represent the plasma state. The solver routine has been hardened so that it can use extremely stiff transport models such as GLF23 without relaxation or other smoothing techniques. Examples of these are presented. [Preview Abstract] 

R1.00054: Stability of high beta poloidal configurations in tokamak geometries. P.A. Gourdain, S.C. Cowley, J.N. Leboeuf, R.Y. Neches The resilience of high beta plasmas to internal instabilities precluding high kinetic pressure in conventional tokamaks remains to be fully examined. In fact, a bell shape current profile restricts the stability of these plasmas below the Troyon limit. Furthermore, such configurations exhibit little magnetic shear as the safety factor q varies from 1 at the center of the plasma to only 3 at the edge. We propose to explore the stability of highly shifted plasma equilibria using the high beta ideal MHD code CUBE and the stability code DCON. Using the geometry and magnetic field of the Electric Tokamak, we will demonstrate that fixedboundary plasmas with Shafranov shifts on the order of unity are stable for several MHD criteria such as Mercier, resistive or highn ballooning. The strong magnetic shear of these configurations makes them quite attractive for turbulence suppression and ballooning stability. Stable plasmas with a peak beta of 15{\%} and a shift of 75{\%} have been reached. A stable path from regular to highly shifted current profile configurations will also be discussed. [Preview Abstract] 

R1.00055: Fullwave coupling to a 3D antenna code using Green's function formulation of waveparticle response. John Wright, Paul Bonoli, Marco Brambilla, Vito Lancelloti, Riccardo Maggiora, Mark Carter Using the fullwave code, TORIC ,and the 3D antenna code, TOPICA, we construct a complete linear system for the RF driven plasma. The 3D finite element antenna code, TOPICA, requires an admittance, \textbf{Y}, for the plasma, where $B=Y\bullet E$. In this work TORIC was modified to allow excitation of the (E$\eta $, E$\zeta )$ electric field components at the plasma surface, corresponding to a single poloidal and toroidal mode number combination (m,n). This leads the tensor response: $Y=\left( {{\begin{array}{*{20}c} {Y\eta \eta } \hfill \& {Y\eta \zeta } \hfill \\ {Y\zeta \eta } \hfill \& {Y\zeta \zeta } \hfill \\ \end{array} }} \right)$, where each of the Yn submatrices is Nm in size. It is shown that the admittance matrix is equivalent to a Greens function calculation for the fullwave system and in addition, the net work done in the calculation is on the order of twice a single fullwave calculation. After the admittance calculation is done, the response of a plasma to an antenna driven at a given frequency can be calculated by only running the TOPICA code for a new antenna geometry. In tests of loading, TOPICA has been able reproduce loading of the Alcator D antenna (S12 coefficient accurately.). [Preview Abstract] 

R1.00056: Tetrahedral Mesh MHD Simulations and Taylor States of HITSI George Marklin, Tom Jarboe This poster will report on progress to validate a tetrahedral mesh resistive MHD code by doing simulations of the HITSI experiment at the University of Washington and comparing the results to experimental data and to Taylor state calculations. The experiment has two AC helicity injectors which generate a rotating n=1 field structure that is expected to undergo Taylor relaxation (magnetic reconnection conserving global helicity) to form and sustain a time independent n=0 spheromak. Taylor state calculations show what is to be expected if complete relaxation occurs. MHD simulations will show varying degrees of relaxation depending on how much physics is included in the MHD model. Initial simulations will only include resistive MHD and should underestimate the rate of magnetic reconnection and the amount of relaxation that occurs. Experimental observations should be bracketed by the simulation results and the Taylor states. Comparisons of predicted magnetic field structure from the MHD simulations and the Taylor states to probe and flux loop measurements will indicate how much relaxation is occurring and whether the physics included in the MHD model is adequate to predict it. Over time, more physics will be added into the MHD code until predictability is achieved. [Preview Abstract] 

R1.00057: Overview of Experimental and Theoretical Studies of the Periodically Oscillating Plasma Sphere (POPS) Richard Nebel, Jaeyoung Park, Evstati Evstatiev, Alberto Marocchino, Giovanni Lapenta, Luis Chacon Theoretical work has suggested that a tiny oscillating ion cloud may undergo a selfsimilar collapse that can result in the periodic and simultaneous attainment of ultrahigh densities and temperatures. A remarkable feature of these oscillations is that they stay in local thermodynamic equilibrium (lte) at all times independent of the collisionality of the system (i.e. they are exact solutions of the Vlasov equation for Maxwellian distribution functions). In recent experimental work on the INSe device at LANL we have observed the POPS oscillations by resonantly driving the plasma at the POPS frequency. Ongoing theoretical work is focused in two areas: multidimensional kinetic simulations of the stability of the virtual cathode and space charge neutralization during the ion collapse phase of the POPS oscillation. POPS simulation results indicate that significant gains in plasma compression can be achieved by properly programming the electron distribution function at the boundary. Two dimensional kinetic simulations indicate that the virtual cathode stability to electronelectron twostream modes is similar to the 1D result. [Preview Abstract] 

R1.00058: Full Orbit PIC in NIMROD Charlson Kim The primary goal of the Plasma Science and Innovation Center (PSI Center) is to refine and optimize existing MHD codes to achieve improved predictability for emerging concept (EC) experiments. Kinetic effects have been shown to play a dominant role in some EC experiments, particularly in FRC stability\footnote{\normalsize{E.~Belova et.al. ``Numerical Study of tilt stability of prolate fieldreversed configurations,'' PoP, {\bf 7}, 4996, 2000}}. The PSI Center will extend the hybrid kineticMHD implementation in NIMROD\footnote{\normalsize{C.C. Kim et.al. ``Hybrid KineticMHD Simulations in General Geometry,'' CPC, {\bf 164}, 448, 2004}} from the drift kinetic model to the full kinetic model to include sufficient physics to accurately account for these effects, in particular large Larmour radius. The Boris push has been implemented for particles in NIMROD. However, this places a severe timestep restriction on the particle time step. We discuss several strategies for circumventing this restriction to simulate on the MHD time scale. We will show some of the preliminary results from the implementation of full orbit (Lorentz force) particles coupled to the NIMROD code. [Preview Abstract] 

R1.00059: Nonlinear Energy Transfer in Ion Temperature Gradient Turbulence W.X. Wang, T.S. Hahm, W.W. Lee, G. Rewoldt, W.M. Tang Nonlinear energy couplings in ion temperature gradient (ITG) turbulence are studied by global gyrokinetic particle simulation of shaped toroidal plasmas based on DIIID geometry. It is observed that the average toroidal mode number is rapidly downshifted by $2/3$ along the $m/n\sim q$ surface, coincidently occurring during the turbulence saturation process. This indicates that the ITG saturation is strongly correlated with nonlinear energy transfer to longerwavelength modes. The nonlinear toroidal coupling is considered as a dominant channel for the energy transfer to lown modes, and simultaneously, to strongly damped highn modes, resulting in the overall spectrum downshift. Our numerical experiments suggest that the zonal flows can drive turbulence. However, the associated energy coupling is very weak. In contrast, the zonal flows are shown to extract a large amount of energy from turbulence components during their generation process. This, in part, represents turbulent transport reduction by zonal flows. In addition, zonal flows also affect the nonlinear energy coupling process in $k$space by transferring turbulence energy faster and more efficiently from unstable modes to stable modes, compared to the case without zonal flows. This is compared to the corresponding effect of an applied equilibrium radial electric field determined by the neoclassical dynamics. [Preview Abstract] 

R1.00060: Study of a simulated sustained edgecurrent driven spheromak in SSPX geometry Lynda LoDestro, B.I. Cohen, E.B. Hooper, C.R. Sovinec The sustainment of current in the core of a toroidal plasma by electrostatic edgecurrent drive requires the radial transport of current across imperfect magnetic surfaces. Full sustainment concurrent with adequate energy confinement has been difficult to find either experimentally or numerically. A NIMROD simulation in SSPX geometry with fixed bank current has recently been extended to nearly an L/R time, and exhibits apparent steadystate cycles with timeaveraged sustainment: intervals of closed surfaces and peaked temperature profiles, punctuated by short bursts with voltage spikes and open surfaces. The confinement properties of this simulation will be analysed, and results presented. [Preview Abstract] 

R1.00061: ASTROPHYSICS POSTERS 

R1.00062: Discovery of the Nearby Universal Center Disproves Big Bang's FL Spacetime Expansion Hypothesis, Showing the Big Bang Is False Science, Being the Greatest Faux Pas in the History of Science and Disqualifying It From Being Taught in Public Schools Robert Gentry Hubble's galactic redshiftdistance relation is known as the greatest astronomical discovery ever. I will show, however, that he strongly opposed the most obvious interpretation of his own observations and how this has influenced generations of astronomers to follow his steps and develop the big bang theory based on the FL spacetime expansion hypothesis. Based on my Preprints ``Discovery of a Major Contradiction in Big Bang Cosmology Points to the New Cosmic Center Universe Model.'' CERN Ext2003021, and ``New Cosmic Center Universe Model Matches Eight of Big Bang's Major Predictions Without the FL Paradigm,'' CERN Ext2003022, I will discuss why FL expansion is fatally flawed and why a new cosmic model is a viable replacement. More astrophysical results are available at www.orionfdn.org. These papers were submitted to and received arXiv numbers in 2001 but P. Ginsparg and Cornell continue to suppress their release. The Center of the Universe discovery and the New Cosmic Model affirm the Genesis six day record of God's creation of the heavens, or visible universe (Ps.33:6,9), just as my earlier discoveries and publications unequivocally affirm Earth's almost instantaneous creation (www.halos.com). God left evidence of His creatorship and the validity of His Creation Commandment (Exodus 20:11) for all who look. [Preview Abstract] 
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