Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012; Providence, Rhode Island
Session UP8: Poster Session VIII: Simulation and Modeling of Basic Plasma Phenomena; Plasma and Fusion Technology 
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Room: Hall BC 

UP8.00001: SIMULATION AND MODELING OF BASIC PLASMA PHENOMENA 

UP8.00002: Twofluid plasma modeling using mixed finite element methods Eder Sousa, Uri Shumlak The two fluid plasma system is modeled through the simultaneous use of the continuous (CG) and the discontinuous Galerkin (DG) finite element methods to represent the different fluids. In this application the electron fluid is modeled using the CG method while the ion fluid is modeled using DG. This method is valid in plasma regimes where the electron fluid ex periences no shocks. Similarly, the Maxwell equations can also be modeled using continuous methods since shocks are also not expected in the field vari ables. This approach should allow for better coupling between the fluxes and the source terms since these are unsplit methods. Additionally, because the electron fluid and electromagnetic fields are modeled using CG, there is no use of limiters, which should make those systems more amenable to implicit timestepping. [Preview Abstract] 

UP8.00003: WARPM Framework for advanced plasma model simulations on manycore architectures Noah Reddell, Uri Shumlak A new framework WARPM designed for manycore computing architectures such as GPU is presented. The framework supports both multifluid and continuum kinetic plasma models. We provide exemplary physics results including whistler wave propagation, and show performance gains. For good performance on manycore architectures, code design should minimize data movement. The algorithms developed are thus both local and explicit. Fluid and continuum kinetic models on structured grids also benefit from predictable data access patterns as opposed to PIC models. The resulting framework is a hybrid combination of MPI for communication between nodes, threads for task parallelism on each node, and OpenCL parallel numerical method implementation across hundreds of cores per node. The framework manages data movement, subdomain sequencing, and I/O intelligently such that memory bandwidth bottlenecks can be significantly hidden. Use of OpenCL and our method for sequencing computation naturally allows for heterogeneous computation utilizing both CPU and GPU on a node. A new dynamic OpenCL code assembly scheme allows support for many different models, numerical methods, and geometries; a specific combination of these is chosen at runtime then used to generate a single compiled kernel. [Preview Abstract] 

UP8.00004: Multidimensional Plasma Sheath Modeling Using The Three Fluid Plasma Model in General Geometries Robert Lilly, Uri Shumlak There has been renewed interest in the use of plasma actuators for high speed flow control applications. In the plasma actuator, current is driven through the surrounding weakly ionized plasma to impart control moments on the hypersonic vehicle. This expanded general geometry study employs the threefluid (electrons, ions,neutrals) plasma model as it allows the capture of electron inertial effects, as well as energy and momentum transfer between the charged and neutral species. Previous investigations have typically assumed an electrostatic electric field. This work includes the full electrodynamics in general geometries. Past work utilizing the research code WARPX (Washington Approximate Riemann Problem) employed cartesian grids. In this work, the problem is expanded to general geometries with the euler fluid equations employing Braginskii closure. In addition, WARPX general geometry grids are generated from Cubit or CAD files. Comparisons are made against AFRL magnetized plasma actuator experiments. [Preview Abstract] 

UP8.00005: Recent advances in nonlinear implicit, electrostatic particleincell (PIC) algorithms Guangye Chen, Luis Chac\'on, Daniel Barnes An implicit 1D electrostatic PIC algorithm\footnote{Chen, Chac\'on, Barnes, J. Comput. Phys. 230 (2011)} has been developed that satisfies exact energy and charge conservation. The algorithm employs a kineticenslaved Jacobianfree NewtonKrylov method\footnote{Ibid.} that ensures nonlinear convergence while taking timesteps comparable to the dynamical timescale of interest. Here we present two main improvements of the algorithm. The first is the formulation of a preconditioner based on linearized fluid equations, which are closed using available particle information. The computational benefit is that solving the fluid system is much cheaper than the kinetic one. The effectiveness of the preconditioner in accelerating nonlinear iterations on challenging problems will be demonstrated. A second improvement is the generalization of Ref. 1 to curvilinear meshes,\footnote{Chac\'on, Chen, Barnes, J. Comput. Phys. submitted (2012)} with a hybrid particle update of positions and velocities in logical and physical space respectively.\footnote{Swift, J. Comp. Phys., 126 (1996)} The curvilinear algorithm remains exactly charge and energyconserving, and can be extended to multiple dimensions. We demonstrate the accuracy and efficiency of the algorithm with a 1D ionacoustic shock wave simulation. [Preview Abstract] 

UP8.00006: Progress in Computational CoDesign of a Scalebridging Plasma Simulation Algorithm for Emerging Architectures Dana Knoll, Will Taitano, Bhuvana Srinivasan, Josh Payne, Bill Daughton, Luis Chacon, Al McPherson, David Daniel Los Alamos National Laboratory has recently initiated a new project on the topic of Computational Codesign of Multiscale Algorithms in the Natural Sciences (CoCoMANS). We define computational codesign and the synergistic interaction of Application, Algorithms and Architectures to produce a new class of physics simulation capability. One of our focus application areas is plasma physics, and one of the goals of the project is to demonstrate a paradigm shift in plasma kinetic simulation on emerging, heterogeneous computer architectures. We are developing momentbased scalebridging algorithms with the goal of enabling system scale simulation with selfconsistent kinetic effects. In this presentation we will discuss progress on 1) The overall scalebridging algorithm, 2) Our IMEX solver approach to the full twofluid moment system, 3) Performance profiling of our implicit electromagnetic particle push on a manycore + GPU node, and 4) Performance profiling of our overall scalebridging algorithm in a multinode manycore+GPU environment. [Preview Abstract] 

UP8.00007: Continuum Kinetic Plasma Modeling Using a Conservative 4thOrder Method with AMR Genia Vogman, Phillip Colella When the number of particles in a Debye sphere is large, a plasma can be accurately represented by a distribution function, which can be treated as a continuous incompressible fluid in phase space. In the most general case the evolution of such a distribution function is described by the 6D BoltzmannMaxwell partial differential equation system. To address the challenges associated with solving a 6D hyperbolic governing equation, a simpler 3D VlasovPoisson system is considered. A 4thorder accurate VlasovPoisson model has been developed in one spatial and two velocity dimensions. The governing equation is cast in conservation law form and is solved with a finite volume representation. Adaptive mesh refinement (AMR) is used to allow for efficient use of computational resources while maintaining desired levels of resolution. The model employs a flux limiter to remedy nonphysical effects such as numerical dispersion. The model is tested on the twostream, beamplasma, and DoryGuestHarris instabilities. All results are compared with linear theory. [Preview Abstract] 

UP8.00008: Programmable physical parameter optimization for particle plasma simulations Benjamin RaganKelley, John Verboncoeur, MingChieh Lin We have developed a scheme for interactive and programmable optimization of physical parameters for plasma simulations. The simulation code ObjectOriented Plasma Device 1D (OOPD1) has been adapted to a Python interface, allowing sophisticated user or program interaction with simulations, and detailed numerical analysis via numpy. Because the analysis/diagnostic interface is the same as the input mechanism (the Python programming language), it is straightforward to optimize simulation parameters based on analysis of previous runs and automate the optimization process using a userdetermined scheme and criteria. An example use case of the ChildLangmuir space charge limit in bipolar flow is demonstrated, where the beam current is iterated upon by measuring the relationship of the measured current and the injected current. [Preview Abstract] 

UP8.00009: CPIC: a curvilinear ParticleInCell code for plasmamaterial interaction studies Gian Luca Delzanno, Enrico Camporeale, J. David Moulton, Joseph Borovsky, Elizabeth MacDonald, Michelle Thomsen We present a recently developed ParticleInCell (PIC) code in curvilinear geometry called CPIC (Curvilinear PIC) [1], where the standard PIC algorithm is coupled with a grid generation/adaptation strategy. Through the grid generator, which maps the physical domain to a logical domain where the grid is uniform and Cartesian, the code can simulate domains of arbitrary complexity, including the interaction of complex objects with a plasma. At present the code is electrostatic and Poisson's equation is solved with a scalable multigrid method. CPIC also features a hybrid particle mover, where the computational particles are characterized by position in logical space and velocity in physical space. We will present our latest progress on the development of the code and document the code performance (in terms of solver and with a comparison of the hybrid mover relative to a conventional physical space mover) on standard plasmaphysics tests. \\[4pt] [1] G.L. Delzanno, E. Camporeale, et al., ``CPIC: a curvilinear ParticleInCell code for spacecraftplasma interaction studies,'' Proceedings of the 12st Spacecraft Charging and Technology conference, 2012. [Preview Abstract] 

UP8.00010: Geometric integration of the VlasovMaxwell system with a variational particleincell scheme Jonathan Squire, Hong Qin, William Tang A fully variational, unstructured, electromagnetic particleincell integrator is developed for integration of the VlasovMaxwell equations. Using the formalism of Discrete Exterior Calculus [1], the field solver, interpolation scheme and particle advance algorithm are derived through minimization of a single discrete field theory action. As a consequence of ensuring that the action is invariant under discrete electromagnetic gauge transformations, the integrator exactly conserves Gauss's law. This work was supported by USDOE Contract DEAC0209CH11466.\\[4pt] [1] M. Desbrun, A. N. Hirani, M. Leok, and J. E. Marsden, (2005), arXiv:math/0508341 [Preview Abstract] 

UP8.00011: ParticleinWavelets scheme for the 1D VlasovPoisson equations Romain Nguyen van yen, Eric Sonnendrucker, Kai Schneider, Marie Farge A new numerical scheme called particleinwavelets is proposed for the VlasovPoisson equations, and tested in the simplest case of one spatial dimension. The plasma distribution function is discretized using tracer particles, and the charge distribution is reconstructed using waveletbased density estimation. The latter consists in projecting the Delta distributions corresponding to the particles onto a finite dimensional linear space spanned by a family of wavelets, which is chosen adaptively. The stability and accuracy of the scheme is supported by numerical computations of Landau damping and of the twostream instability. By direct comparison with a reference solution obtained by a very precise semiLagrangian method, we show that the precision is improved roughly by a factor three compared to a classical PIC scheme, for a given number of particles. Ref.: Nguyen van yen et al., ESAIM: Proc, 32 (2011), 134148. [Preview Abstract] 

UP8.00012: EntropyBased Accelerated Monte Carlo Methods for Coulomb Collisions Lee Ricketson, Mark Rosin, Russel Caflisch, Bruce Cohen, Andris Dimits We present a computational method for the simulation of Coulomb collisions in plasmas that significantly improves upon our earlier hybrid method, which combines a Monte Carlo particle scheme and a fluid dynamic solver in a single uniform method across phase space. The hybrid method represents the velocity distribution function $f(v)$ as the sum of a Maxwellian $M(v)$ and a collection of discrete particles $g(v)$. $M$ evolves in space and time through fluid equations, and $g$ through a Monte Carlo particle in cell (PIC) method. Interactions between $M$ and $g$ are mediated by mean fields and simulated collisions. Computational resources are reallocated by (de)thermalization processes that move particles from $g$ to $M$ and vice versa. We present a new algorithm for performing these (de)thermalizations that is more accurate and rigorously justifiable than previous efforts. This new algorithm assigns a passive scalar to each simulated particle that approximates a ``relative entropy.'' Particles are thermalized (dethermalized) when this quantity is sufficiently small (large). We present results from numerical simulations of two test problems  a two temperature Maxwellian and a bumpontail distribution, finding a computational savings between a factor of 5 and 20 over PIC. [Preview Abstract] 

UP8.00013: Multitemperature representation of electron velocity distribution functions JeanPierre Matte, Amir Abbas Haji Abolhassani In kinetic simulations of plasmas, the velocity distribution function is represented on finite difference grids in space and energy. Using spherical harmonics for the angular distribution helps, but the energy grid is still a burden. We propose to replace it by an expansion using three Maxwellians each multiplied by a series of generalized Laguerre or Sonine polynomials, or by a simple sum of 612 Maxwellians, which turned out to be simpler and to work better. We have fitted distribution functions obtained with the finite difference code ``FPI'' [1] using these techniques. We show that it provides a convenient alternative to numerical integration for computing rates of ionization or excitation. We have also developed a moment method to simulate the FP electron collision operator, and simulated the relaxation of a hot Maxwellian on a cold one, with initial temperature ratios as high as 1000. Comparisons with ``FPI'' simulations show good agreement. \\[4pt] [1] J.P. Matte and J. Virmont, Phys.Rev. Lett. 49, 1936 (1982). [Preview Abstract] 

UP8.00014: Visualization of TurbulenceGenerated Intrinsic Rotation Eliot Feibush, Stephane Ethier, Weixing Wang, William Tang A new visualization has been developed of the 3D vector field of plasma flow computed by global gyrokinetic simulations using the GTS code. The visualization shows the direction, magnitude, and structure of turbulencegenerated intrinsic rotation in a tokamak. Vectors indicate the clockwise and counterclockwise flows around the torus. Colorcoded vectors are drawn at each grid point on the poloidal planes. A color scale was developed to maximize contrast within the most heavily populated range of data while preserving visibility of the global minimum and maximum values. Technical highlights include transferring large amounts of simulation data from NERSC to PPPL using multiple streams, parallel rendering by the VisIt software, and multiple nx client sessions connecting to a persistent server session. Each of the 1,000 time steps is rendered to a high definition image. The images are assembled into an animated movie that is compressed for efficient, high quality playback. A workflow is in place for producing visualizations of new simulations. [Preview Abstract] 

UP8.00015: Numerical study of wave damping and amplification through ionization and recombination Vasily Geyko, Nathaniel Fisch Plasma wave energy in slowly ionizing or recombining plasma obeys general adiabatic invariants [1]. For a simple model of a homogeneous in space ionization we studied the behavior of a 1D Langmuir wave using our PIC code. However, discrepancies are found from the theory for linear waves [1] with unusual effects attributed possibly to ponderomotive focusing, namely, different damping rates for standing and moving waves.\\[4pt] [1] I.Y. Dodin and N.J. Fisch, Phys. Plasmas 17, 112113 (2010). [Preview Abstract] 

UP8.00016: The Kinetic Theory Molecular Dynamics Method Christopher Fichtl, Michael Murillo, Frank Graziani Plasmas under the thermonuclear burn conditions relevant to ICF and astrophysical plasmas typically consist of moderately degenerate, weakly coupled electrons and classical, moderately to strongly coupled ions. In order to better simulate such conditions, we have developed the Kinetic Theory Molecular Dynamics (KTMD) method to selfconsistently describe the nonequilibrium electron dynamics using an appropriate kinetic equation while leaving the ion dynamics to MD. To simulate the plasma electrons, we have developed a manyfermion quantum PIC code capable of simulating conditions in which the phase space evolution of the plasma electrons in an initial Wigner distribution is accurately described by the quantum Vlasov (Wigner) equation. The plasma ions are followed using a recently developed MD code that utilizes a PPPM field solver specifically tuned to work in conjunction with the PIC field solver. The PIC and MD codes are coupled via the field equations such that the plasma electrons and ions act as source terms for the update equations of the opposite species. We present the basic ideas behind our approach, its associated implementation, and several physics benchmking results to demonstrate its feasibility. [Preview Abstract] 

UP8.00017: An UnstructuredMesh Code for Iteratively Computing the Ion and Electron Distribution Functions Near a Collecting Object in a NonUniform Quasineutral Plasma Christian Bernt Haakonsen, Ian H. Hutchinson Probes and other collecting objects perturb the surrounding plasma, deforming and introducing voids in the ion and electron distribution functions. This perturbation complicates the inference of plasma parameters from probe measurements, and many settings remain without a satisfactory model or understanding. For example, previous work using a fluid approximation has suggested that diamagnetic drifts due to background density and temperature gradients may affect magnetized Mach probe measurements, but detailed computational study is required to validate and elaborate on those results. To that end, a new code has been developed for selfconsistently computing the steadystate sixdimensional ion and electron distribution functions in the perturbed region of a quasineutral plasma. The code computes the ion and electron density at each node of an unstructured mesh by integrating particle orbits backwards in time to the domain boundary, where arbitrary background distribution functions can be specified. The potential is then updated based on the computed densities, and the process is iterated until convergence. An overview of the code and its capabilities is presented, along with preliminary results on the impact of a background density gradient on magnetized Mach probe measurements. [Preview Abstract] 

UP8.00018: Simulations of the VlasovPoisson system and the study of recurrence for the discontinuous Galerkin method Yingda Cheng, Irene Gamba, P.J. Morrison We describe the RungeKutta discontinuous Galerkin (RKDG) scheme\footnote{R. E.~Heath, I.~M.~Gamba, P.~J.~Morrison, and C.~Michler, J.\ Comp.\ Phys.\ {\bf 231}, 1140 (2012).} for the VlasovPoisson system that models collisionless plasmas. Onedimensional systems are emphasized. This numerical method used is seen to have excellent conservation properties, be readily designed for arbitrary order of accuracy, and be used with a positivitypreserving limiter that guarantees positivity of the distribution function. We compute the solutions using a highorder discontinuous Galerkin method for the Vlasov equation, and the classical representation by Green's function for the Poisson equation in the onedimensional setting. We performed Fourier analysis to study recurrence of the discontinuous Galerkin methods on Cartesian meshes. Results from several benchmark test problems, such as Landau damping, twostream instability and the KEEN (Kinetic Electrostatic Electron Nonlinear) wave, are given and interpreted. [Preview Abstract] 

UP8.00019: ABSTRACT WITHDRAWN 

UP8.00020: The Lacuna Open Boundary Condition For Electromagnetics and ParticleinCell Simulation of Plasmas Eric Wolf, Andrew Greenwood, Andrew Christlieb In many typical situations in computational electromagnetics (CEM), a finite computational domain must be truncated with a boundary condition (called an absorbing boundary condition or open boundary condition, among other names) that allows outgoing waves to exit with minimal spurious reflection. One highly successful such boundary condition is the perfectly matched layer (PML), introduced by Berenger in 1994 and refined by others in subsequent years, which provides for minimal reflection at an acceptable computational cost. One difficulty in the use of PML is the need to tune several parameters to suit any given problem. Another open boundary condition is the lacuna open boundary condition (LOBC), pioneered by Ryaben'kii, Tsynkov and others, which makes use of the presence of lacunae, still regions where all waves have left and will no longer return, in solutions to wave equations in odd dimensions with compactly supported sources. We examine the use of the LOBC as a means of truncating Finite Difference Time Domain (FDTD) meshes in electromagnetic simulations and particleincell simulations of plasmas, and compare to PML in terms of spurious reflections, computational cost and ease of use. [Preview Abstract] 

UP8.00021: Verification and Convergence Properties of ParticleinCell Codes Stephanie Y. Su, Viktor K. Decyk, Warren B. Mori ParticleinCell (PIC) codes are widely used throughout plasma physics. Nevertheless, there is considerable confusion about what precisely is the mathematical model behind PIC codes and whether PIC codes converge to such a model. This numerical study is intended to shed light on these issues. Our basic hypothesis is that a Klimontovich equation with finitesize particles is the basic mathematical model behind PIC codes. A gridless particle code is first used to establish basic convergence to that model and then PIC codes are compared to it. [Preview Abstract] 

UP8.00022: An Implicit Solver for the VlasovPoison Equation Michael Carri\'e, B.A. Shadwick Due to the numerical difficulties associated with the convective term in the Vlasovequation and the robustness and ease of implementation of PIC codes, phasespace grid methods have received little attention for describing laserplasma interactions and has been limited to lowdimensional problems. However, this method is theoretically noiseless and can be of great interest in applications where noise is of crucial importance and fine grained phasespace resolution is needed (for example, when studying particle trapping). In the scope of electron acceleration in underdense plasmas over a long distance (cm to m), we present the development of an implicit 1D1V Vlasov solver using a phasespace grid method. Benchmarking tests revealed surprisingly good results; all invariants are very well conserved with a relative error up to $10^{5}$. However, as filaments scale down to the grid resolution, oscillations are introduced in the solution and negative values for the distribution function appear. Nevertheless, their contributions to the macroscopic values (electric field, density, Vlasov invariants) are negligible. We present a number to standard test cases to illustrate the potential of this approach. [Preview Abstract] 

UP8.00023: Development of an Implicit, Charge and Energy Conserving 2D Electromagnetic PIC Code on Advanced Architectures Joshua Payne, William Taitano, Dana Knoll, Chris Liebs, Karthik Murthy, Nicolas Feltman, Yijie Wang, Colleen McCarthy, Emanuel Cieren In order to solve problems such as the ion coalescence and slow MHD shocks fully kinetically we developed a fully implicit 2D energy and charge conserving electromagnetic PIC code, PlasmaApp2D. PlasmaApp2D differs from previous implicit PIC implementations in that it will utilize advanced architectures such as GPUs and shared memory CPU systems, with problems too large to fit into cache. PlasmaApp2D will be a hybrid CPUGPU code developed primarily to run on the DARWIN cluster at LANL utilizing four 12core AMD Opteron CPUs and two NVIDIA Tesla GPUs per node. MPI will be used for crossnode communication, OpenMP will be used for onnode parallelism, and CUDA will be used for the GPUs. Development progress and initial results will be presented. [Preview Abstract] 

UP8.00024: A FluidKinetic ParticleinCell Solver Stefano Markidis, Pierre Henri, Giovanni Lapenta, Kjell Ronnmark, Maria Hamrin, Erwin Laure A fluid solver that retains kinetic effects by using the ParticleinCell (PIC) algorithm is presented in the context of future coupled fluidkinetic plasma simulations. The fluid continuity and momentum equations together with the second order formulation of Maxwell's equations are solved concurrently using the finite volume box scheme. The pressure tensor in the fluid momentum equation is selfconsistently computed using the computational particles. The electric field is corrected to take into account the discrepancies between the fluid densities calculated from the fluid equation and the one calculated directly from the computational particles. The magnetic field is determined from Faraday's law. Finally, the position and velocity of the computational particles are advanced in time. The fluidkinetic PIC solver is implemented starting from the iPIC3D code, a massively parallel fully kinetic code. The fluidkinetic PIC solver method could be used in spatial regions where kinetic effects are important, while a traditional fluid solver would be used in regions of space where the kinetic effects are negligible to save computational time. Therefore, the proposed scheme is a promising approach for coupling fluid and kinetic methods in a unified framework. [Preview Abstract] 

UP8.00025: Graphics Processing Unit Acceleration of Gyrokinetic Turbulence Simulations Benjamin Hause, Scott Parker We find a substantial increase in onnode performance using Graphics Processing Unit (GPU) acceleration in gyrokinetic deltaf particleincell simulation. Optimization is performed on a twodimensional slab gyrokinetic particle simulation using the Portland Group Fortran compiler with the GPU accelerator compiler directives. We have implemented the GPU acceleration on a Core I7 gaming PC with a NVIDIA GTX 580 GPU. We find comparable, or better, acceleration relative to the NERSC DIRAC cluster with the NVIDIA Tesla C2050 computing processor. The Tesla C 2050 is about 2.6 times more expensive than the GTX 580 gaming GPU. Optimization strategies and comparisons between DIRAC and the gaming PC will be presented. We will also discuss progress on optimizing the comprehensive three dimensional general geometry GEM code. [Preview Abstract] 

UP8.00026: Hamiltonian and Lagrangian approaches to hybrid kineticfluid plasmas Cesare Tronci, P.J. Morrison, Emanuele Tassi The development of multiscale multiphysics models is required in different contexts of plasma physics, from fusion theory to space plasmas. Indeed, plasmas are often found to consist of two different species: a cold (fluid) species and a hot (kinetic) component. Several modeling efforts over the last two decades culminated in the formulation of two main types of hybrid kineticfluid models: currentcoupling schemes (CCS') and pressurecoupling schemes (PCS'). Although CCS' conserve energy exactly, PCS' (used in simulations) require certain approximations that break exact energy conservation. In this work, we formulate new PCS models, whose exact energy conservation is guaranteed by an appropriate Hamiltonian (and Lagrangian) structure. A comparison of Hamiltonian and nonHamiltonian models is then presented, in terms of linear and nonlinear stability. [Preview Abstract] 

UP8.00027: Ultra High Resolution ParticleInCell Simulations of Transition to Turbulence using GPU acceleration Kai Germaschewski, William Fox, Homa Karimabadi, Vadim Roytershteyn, William Daughton Advances in computing power have enabled kinetic particleincell simulations of plasma transition to turbulence at unprecedent resolutions. Nonlinear KelvinHelmholtz and tearing instabilities, driven by an initial shear flow, lead to fully developed turbulence, spanning scales from MHD down to electron kinetic scales. Currently, advances in computational capabilities for some of the largest computers in the world, like DOE's upcoming Titan machine, are driven by the use of graphics processing units (GPUs) to accelerate computationally intensive tasks. We present new modules in the electromagnetic particleincell code PSC that enable effective use of the computational capabilities of massively parallel GPU based computers for kinetic plasma simulations. In particular, we will address (1) efficient algorithms for implementing particle advance, current deposition and sorting, (2) a load balancing scheme based on decomposition into small patches and spacefilling curves, and (3) challenges of using both CPU and GPUs simultaneously in order to exploit all available computational resources optimally. [Preview Abstract] 

UP8.00028: Kinetic ParticleinCell Simulations and Generation of Current Sheets in High Temperature Turbulent Plasmas Michael Shay, Pin Wu, Homa Karimabadi, William Matthaeus, Minping Wan, Vadim Roytershteyn, William Daughton An important unsolved problem in plasma turbulence is how energy is dissipated at small scales. Particle collisions are too infrequent in hot plasmas to provide the necessary viscosity. We simulate strong turbulence using kinetic PIC simulations, starting with shear flow dominated initial conditions that are unstable to KelvinHelmholtz. The system generates strong electron scale current sheets which eventually reconnect. We examine the dissipation mechanisms in the system to determine if these current sheets are playing an important role in the damping of turbulent energy~[1]. Preliminary results for other initial conditions will also be presented. \\[4pt] [1]~Karimabadi et al., Coherent Structures, Intermittent Turbulence and Dissipation in HighTemperature Plasmas, Submitted to {\em Nature}, 2012. [Preview Abstract] 

UP8.00029: Accelerated Monte Carlo Methods for Coulomb Collisions Mark Rosin, Andris Dimits, Lee Ricketson, Russel Caflisch, Bruce Cohen As an alternative to binarycollision models for simulating Coulomb collisions in the FokkerPlanck limit, we present a new numerical higherorderaccurate time integration scheme for Langevinequationbased collisions. A Taylorseries expansion of the stochastic differential equations is used to improve upon the standard Euler time integration. Additional Milstein terms arise in the timediscretization due to both the velocity dependence of the diffusion coefficients, and the aggregation of angular deflections. We introduce an accurate, easily computable direct sampling method for the multidimensional terms  an approximation to the double integral over products of Gaussian random processes. Including these terms improves the strong convergence of the time integration of the particle trajectories from O($\Delta $t1/2) to O($\Delta $t). This is useful as a both a first step towards direct higherorder weak schemes (for computing average quantities), and as a key component in a ``multilevel'' scheme that returns a computationally efficient estimate of averaged quantities. The latter is maximally efficient, in the asymptotic sense, when used with Milstein terms, and therefore the optimal choice of multilevel scheme. We present results showing both the improved strong convergence of the new integration method, and the increased efficiency multilevel scheme. [Preview Abstract] 

UP8.00030: Suprathermal ion transport theory and experiments in the SMT Kyle Gustafson, Alexandre Bovet, Ambrogio Fasoli, Ivo Furno, Paolo Ricci Recent advances in the suprathermal ion diagnostic in the basic plasma experiment TORPEX have inspired our comprehensive theoretical study of suprathermal ion transport. TORPEX, an example of a simple magnetized toroidal plasma (SMT), is equipped with a flexible fast ion source and detector capable of exploring fast ion dynamics in a wide range of positions and energies. We simulate an ensemble of ion tracer trajectories as specified by ideal interchangemode turbulence imported from a validated numerical simulation based on the driftreduced Braginskii model. Using the variance of displacements, $\sigma^2(t) \sim t^{\gamma}$, we find that $\gamma$ depends strongly on suprathermal ion injection energy and the magnitude of turbulent fluctuations. When the beam interacts with the turbulence, we find the remarkable presence of three regimes of dispersion: superdiffusive, diffusive, and subdiffusive, depending on the energy of the suprathermal ions and the amplitude of the turbulent fluctuations. Results from the source on TORPEX are consistent with the theoretical predictions. [Preview Abstract] 

UP8.00031: Noninertial Eulerian Hydrodynamic Code for ICF Implosion Simulations A. Bose, P.Y. Chang, J.R. Davies, R. Betti We present the first results from a 2D Eulerian hydrodynamic code that solves the equations of motion in the frame of reference of the target center of mass. The fluid equations are written in the conserved Eulerian form with extra source terms arising because of the noninertial nature of the coordinate system. The accelerated coordinate system allows for the use of a static Eulerian grid. The coordinates move with a sharp density gradient therefore specifying the location of a finemesh region. The code uses the finitevolume method with several schemes that have been compared for propagating shock fonts. Numerical experiments have been implemented to test the code. The results from this new code are compared with those from existing Eulerian and Lagrangian hydrodynamic codes. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement Nos. DEFC5208NA28302 and DEFC0204ER54789. [Preview Abstract] 

UP8.00032: PLASMA AND FUSION TECHNOLOGY 

UP8.00033: Stable isotope enrichment using a plasma centrifuge Mahadevan Krishnan, Brian Bures, Robert Madden A primary goal of the Department of Energy's Isotope Development and Production for Research and Applications Program (Isotope Program) within the Office of Nuclear Physics (NP) is to produce isotopes that are in short supply in the U.S. and of which there exists no or insufficient domestic commercial production capability. A vacuum arc plasma centrifuge is a rigid rotor column of metal plasma in which centrifugal forces redistribute ions radially according to their mass/charge ratio. Early work demonstrated rotation at 2 million rpm and separation of various stable isotopes. The spinning plasma column had a Gaussian flux profile, peaked on the rigid rotor axis. This work adopts a more efficient approach, with the plasma created as a hollow column, wherein the flux is concentrated at larger radii where the centrifugal action is highest. By tailoring the vacuum arc discharge geometry, the rotation rate can also be increased to $\sim $10 million rpm. Data from Cu, Al and other metal plasmas will be presented and discussed in light of enriched stable isotopes needed for research and medicine. [Preview Abstract] 

UP8.00034: High Field Plasma Experiments with Optimal Temperature Hybrid Magnets G. Grasso, B. Coppi Developments in the technology of MgB$_2$ superconducting magnets operating at temperatures around 10 K has led to envision their use for fields up to 10 T and as components of hybrid (copper for the highest field + MgB$_2$) magnets. A hybrid magnet of this kind is being constructed at Grenoble. The common coolant is Hegas, the optimal temperature for Cu being about 30 K. The goal of this solution is to construct machines producing plasmas with values of the poloidal field close to those considered for the design of the Ignitor machine but with longer burning times and higher duty cycles. A perspective of this program is to produce devices to be used as neutron sources or material testing systems. Since the relevant machines will have to be larger than Ignitor, they will have to be able to sustain higher plasma currents under macroscopically stable conditions. [Preview Abstract] 

UP8.00035: A Robust Modular IGBT Power Supply for Innovative Confinement Concepts Timothy Ziemba, Kenneth Miller, James Prager Eagle Harbor Technologies (EHT) has developed an IGBTbased switching module for pulsed high power ($>$ 10 MW) RF applications. These modules contain a control voltage supply (isolated to 30 kV) and fiber optically isolated drive circuitry, which allows for easy integration into a wide variety of power supply configurations. Each module is capable of switching 2.5 kA (pulsed) or at 1 kV or switching 100 kW (CW) up to megahertz frequencies with rise times of 40 ns. The modules are designed for precise switching control, which reduces jitter ($<$ 5 ns) between modules, enabling robust series operation. EHT will present the final module design and performance results. In addition, data will be presented from two power supplies utilizing the EHT module: a 10 kV series stack that drives a resistive load at 500 A and a half bridge configuration that drives series resonant network with over 5 MW oscillating power. [Preview Abstract] 

UP8.00036: Operational Space within Power Amplifier Limits for IGNITOR R. Albanese, G. Ambrosino, G.M. De Tommasi, A. Pironti, G. Rubinacci, F. Villone, G. Ramogida, B. Coppi The avoidance and mitigation of plasma disruptions plays an important role in the safe operation of IGNITOR, the high field compact machine designed for the investigation of fusion burning plasmas at or close to ignition. The plasma control system is designed to obtain stable closed loop plasma configurations with an assigned plasma shape and current. This accurate and integrated control of plasma position, shape and current can be indeed an effective aid for disruption avoidance and mitigation. In some cases, the PF coil currents can attain values very close to their saturation limits. The redistribution of the currents in the PF coil system with small modifications of the plasma shape can provide better control margins while keeping the main shape constraints. A critical aspect is related to the constraints imposed by the voltage and current limits of the amplifiers affecting the time needed to implement a suitable dynamic currents allocation. While taking these constraints into account, a parametric study has been carried out showing the possible enlargement of the operational space in terms of the poloidal beta and of the internal inductance values. [Preview Abstract] 

UP8.00037: Tokomak disruption runaway electron beam energy deposition Yian Lei Disruption is one of the major concerns in magnetic confinement fusion (MCF) research. People believe the energetic runaway electron beam can damage the first wall by depositing most of its energy to certain region as heat, melting the wall. However, as the energy of the beam electron is very high (up to 50 MeV), most of the beam energy should be converted as gamma radiation and escape, and the fraction of thermal energy deposition is relatively small. We will calculate the runaway electron energy deposition in typical first wall configurations in ITER disruption scenario, and give the temperature profile of the wall. We will also calculate the bremsstrahlung gamma ray spectra of the beam and discuss the consequences. [Preview Abstract] 

UP8.00038: Modeling of Hydrogen Retention in Metallic Plasma Facing Components Jerome Guterl, R. Smirnov The retention of hydrogen isotopes in the vacuum vessel of the ITER device is a critical plasma wall interaction issue for safety (tritium inventory) and operational reasons (hydrogen recycling). In particular, longterm retention of hydrogen have been observed both in the nearsurface region and in the bulk of material in experiments reproducing ITER first wall conditions [1]. In this work, we present a modeling of the longterm hydrogen retention in a plasma exposed metallic walltaking into account processes both at the wall surface (material erosion, hydrogen adsorption, etc.) and in the bulk (hydrogen implantation, creation of trap sites, etc.). Using numerical simulations, the model is applied to analyze retention as a function of various parameters of the wall irradiated by hydrogen plasma for beryllium wall. Depth profiles of retained hydrogen for several ion energies as well as dependencies of retained hydrogen amount on wall temperature are obtained, showing good agreement with experimental data. The role of radiationinduced pointdefects in the hydrogen retention as well as other aspects of retention are discussed in application to ITER conditions. \\[4pt] [1] R.A. Anderl, et al., J. Nucl. Mater. 273 (1999) 1 [Preview Abstract] 

UP8.00039: Characterization of a compact ECR microwave plasma source for the purpose of examining early stage tungsten fuzz growth David Donovan, Dean Buchenauer, Josh Whaley Exposure of tungsten to low energy ($<$ 100 eV) helium plasmas at temperatures between 9001900 K in both laboratory experiments [1] and tokamaks [2] has been shown to cause severe nanoscale modification of the near surface, termed tungsten fuzz growth. Fuzz formation can lead to nonsputtered erosion and dust formation. To better compare with models being developed for the fuzz formation, we are exploring the use of a compact ECR plasma in situ with scanning tunneling microscopy to investigate the early stages of helium induced tungsten migration under these conditions. Here we report on preliminary characterization of the plasma source for helium plasmas with a desired ion flux of $\sim $5x10$^{18}$ ions m$^{2}$ s$^{1}$ on the tungsten surface. The characterization is performed using a cylindrical Langmuir probe capable of moving axially along the direction of the plasma as well as rotationally between fully exposed and fully removed from the plasma. Variations in background pressure, plasma density, and total input power are discussed. \\[4pt] [1] M.J. Baldwin and R.P. Doerner, Nucl. Fusion 48 (2008) 035001; M.J. Baldwin and R.P. Doerner, J. Nucl. Mater. 404 (2010) 165. \\[0pt] [2] G.M. Wright, D. Brunner, M.J. Baldwin, et al, Nucl. Fusion 52 (2012) 042003. [Preview Abstract] 

UP8.00040: Analysis of the interaction of deuterium plasmas with tungsten in the FuegoNuevo II device Gonzalo Ramos, Ferm\'In Castillo, Mart\'In Nieto, Marco Mart\'Inez, Jos\'e Rangel, Julio HerreraVel\'azquez Tungsten is one of the main candidate materials for plasmafacing components in future fusion power plants. The FuegoNuevo II, a plasma focus device, which can produce dense magnetized helium and deuterium plasmas, has been adapted to address plasmafacing materials questions. In this paper we present results of tungsten targets exposed to deuterium plasmas in the Fuego Nuevo II device, using different experimental conditions. The plasma generated and accelerated in the coaxial gun is expected to have, before the pinch, energies of the order of hundreds eV and velocities of the order of 40,000 m s$^{1}$. At the pinch, the ions are reported to have energies of the order of 1.5 keV at most. The samples, analysed with a scanning electron microscope (SEM) in cross section show a damage profile to depths of the order of 580 nm, which are larger than those expected for ions with 1.5 keV, and may be evidence of ion acceleration. An analysis with the SRIM (Stopping Range of Ions in Matter) package calculations is shown. [Preview Abstract] 

UP8.00041: \textit{Insitu} synergistic D/He irradiation studies of Lithium coated commercial and multimodal Tungsten and nanocomposite LiW thin films Anton Neff, Jean Paul Allain, Osman ElAtwani, Chase Taylor, Yousung Han, Ming Gan, Vikas Tomar, Ashish Singh, Sandip Harimkar Because of their high melting temperature and resistance to sputtering, refractory metals, such as W or Mo, are an attractive wall material for burning plasma devices like fusion tokamaks. For example, the current plan for ITER is to use a pure W divertor. However the refractory metals can result in damage (i.e., hardening, blistering, embrittlement, nanostructuring, etc) due to lowenergy irradiation by hydrogen and helium. These effects could potentially allow high Z particles to enter the fusion plasma and extinguish it. Three potential methods of preventing the irradiationinduced damage are investigated: increasing the density of the grain boundaries via ultrafine multimodal grained tungsten, using lithium as a coating material, and creating WLi nanocomposite thin films. Hydrogen, helium, and synergistic D/He irradiations were performed in PRIHSM at Purdue University, up to fluences of $\sim $10$^{17}$ cm$^{2}$, energies between 1001000 eV, and temperatures from room temperature up to 300 \r{ }C, while monitoring in situ the sputtering rate and the surface evolution using XPS. Other surface characterizations were performed using SEM and AFM. [Preview Abstract] 

UP8.00042: FARTECH's Nanoparticle Plasma Jet System and its Application to Disruptions, Deep Fueling, and Diagnostics J.R. Thompson, I.N. Bogatu, S.A. Galkin, J.S. Kim Hyper{\}velocity plasma jets have potential applications in tokamaks for disruption mitigation, deep fueling and diagnostics. Pulsed power based solidstate sources and plasma accelerators offer advantages of rapid response and mass delivery at high velocities. Fast response is critical for some disruption mitigation scenario needs, while high velocity is especially important for penetration into tokamak plasma and its confining magnetic field, as in the case of deep fueling. FARTECH is developing the capability of producing largemass hypervelocity plasma jets. The prototype solidstate source has produced: 1) $>$8.4 mg of H$_{2}$ gas only, and 2) $>$25 mg of H$_{2}$ and $>$180 mg of C$_{60}$ in a H$_{2}$/C$_{60}$ gas mixture. Using a coaxial plasma gun coupled to the source, we have successfully demonstrated the acceleration of composite H/C$_{60}$ plasma jets, with momentum as high as 0.6~g$\cdot $km/s, and containing an estimated C$_{60}$ mass of $\sim $75 mg. We present the status of FARTECH's nanoparticle plasma jet system and discuss its application to disruptions, deep fueling, and diagnostics. A new TiH$_{2}$/C$_{60}$ solidstate source capable of generating significantly higher quantities of H$_{2}$ and C$_{60}$ in $<$0.5 ms will be discussed. [Preview Abstract] 

UP8.00043: Development of a double plasma gun device for investigation of effects of vapor shielding on erosion of PFC materials under ELMlike pulsed plasma bombardment I. Sakuma, D. Iwamoto, Y. Kitagawa, Y. Kikuchi, N. Fukumoto, M. Nagata It is considered that thermal transient events such as type I edge localized modes (ELMs) could limit the lifetime of plasmafacing components (PFCs) in ITER. We have investigated surface damage of tungsten (W) materials under transient heat and particle loads by using a magnetized coaxial plasma gun (MCPG) device at University of Hyogo. The capacitor bank energy for the plasma discharge is 144 kJ (2.88 mF, 10 kVmax). Surface melting of a W material was clearly observed at the energy density of $\sim $2 MJ/m2. It is known that surface melting and evaporation during a transient heat load could generate a vapor cloud layer in front of the target material [1]. Then, the subsequent erosion could be reduced by the vapor shielding effect. In this study, we introduce a new experiment using two MCPG devices (MCPG1, 2) to understand vapor shielding effects of a W surface under ELMlike pulsed plasma bombardment. The capacitor bank energy of MCPG2 is almost same as that of MCPG1. The second plasmoid is applied with a variable delay time after the plasmoid produced by MCPG1. Then, a vapor cloud layer could shield the second plasma load. To verify the vapor shielding effects, surface damage of a W material is investigated by changing the delay time. In the conference, the preliminary experimental results will be shown.\\[4pt] [1] A. Hassanein et al., J. Nucl. Mater. \textbf{390391}, pp. 777780 (2009). [Preview Abstract] 

UP8.00044: Heat transfer in freesurface, flowing liquid metal J. Rhoads, E. Spence, E. Edlund, P. Sloboda, H. Ji The presence of a strong external magnetic field affects structures within the flow of conducting fluids such as liquid metals, which may have significant implications for thermal convection in proposed liquidmetal divertor concepts. Experiments have been conducted in the Liquid Metal Experiment (LMX) using a GaInSn eutectic alloy as a working fluid to investigate the anisotropization due to the magnetic field on turbulent structures in the flow and the resulting effects on convective heat transfer. These experiments considered freesurface, wide aspectratio flow through a channel situated in a magnetic field (up to $\textrm{Ha} \approx 50$). Heat was injected into the fluid via resistive heaters located either on the surface or submerged in the fluid. The thermal profile was tracked on the surface of the flow by a midwavelength IR camera and at the bottom of the flow by a dense array of fine gage thermocouples. Along with internal velocity measurements, the temporal and spatial thermal profiles show the effects of the magnetic field on convection, yielding valuable insight into the behavior of heat transfer in freesurface, liquid metal flows. Experimental results and proposed explanations will be presented. [Preview Abstract] 

UP8.00045: Chemical Sputtering Studies of Lithiated Graphite Priya Raman, Andrew Groll, Tyler Abrams, Davide Curreli, Daniel Andruczyk, D.N. Ruzic Lithium treatments in the National Spherical Torus Experiment have shown dramatic improvements in plasma performance. In order to understand the complex system of lithiated ATJ graphite, chemical sputtering measurements of plain and lithiated ATJ graphite are conducted in IIAX (Ion Surface Interaction Experiment) facility with a differentially pumped Magnetic Sector Residual Gas Analyzer (MSRGA). The ATJ graphite target is mounted in such way that the target can be translated along a line to different positions to get direct comparison of ATJ and lithiated ATJ. Target is heated using joule heating and is connected to a biasing circuitry. Chemical sputtering of graphite is dependent on the ion energy and substrate temperature, hence the total effects of treating ATJ graphite with lithium in hydrogen plasma is investigated in terms of different target temperatures and bias voltages. For this purpose, lithium is evaporated insitu onto ATJ graphite and chemically sputtered species in hydrogen plasma is measured using MSRGA. The dominant chemical sputtering product is CH4. It was found that lithium treatments have suppressed the chemical sputtering of ATJ Graphite. The suppression of chemical sputtering effect is presented as a function of varying lithium thickness on ATJ Graphite. [Preview Abstract] 

UP8.00046: Seebeck Coefficient of Lithium and LithiumTin Alloys L. Kirsch, P. Fiflis, D. Andruczyk, D. Curreli, D.N. Ruzic Experiments into the viability of lithium as a first wall material in a fusion device have shown that it offers great benefits in reducing recycling of hydrogenic species at the wall, increasing energy confinement times, and gettering impurities. However, concerns have been raised about its practicality in regions of high heat fluxes, and one of the greatest is whether or not a lithium divertor concept can function at high steady state temperatures without significant evaporation of the lithium. Lithiumtin alloys might offer a solution by suppressing evaporation, but their performance in a TEMHD driven device such as the LIMIT device under development at UIUC is directly dependent on their thermoelectric properties, namely their unknown Seebeck coefficient. In support of the use of lithiumtin alloys in such a device, experiments are performed to recover the Seebeck coefficient of several different compositions of lithiumtin alloys. Experiments previously performed at the University of Illinois of the Seebeck coefficient of lithium [1] were confirmed and expanded upon by this study. Values of ranging from 12 +/1 uV/K at 82C to 28 +/1 uV/K at 240C were obtained.\\[4pt] [1] V. Surla et al. Journal of Nuclear Materials 415 (2011) 1822. [Preview Abstract] 

UP8.00047: Numerical simulations of evolutionary surface morphology including fractal geometry and dynamic composition changes K.A. Lindquist, D. Curreli, D.N. Ruzic The TRIM code [Biersack and Haggmark, 1980] is a widely used Monte Carlo algorithm for the computer simulations of the interaction of an energetic beam with a solid material. A number of subsequent improvements have been developed after the release of TRIM. As a part of the SciDAC effort, the present work focuses on merging the TRIDYN code [Moller and Eckstein, 1984] with the Fractal Geometry method [Ruzic and Chiu, 1989]. TRIDYN is a TRIM simulation code including dynamic composition changes. From the merging of this code with the fractal method, a more realistic atomicscale treatment of surface modifications and plasmamaterial interactions can be obtained. Numerical tests are oriented toward tungsten and lithiumcovered PFCs. [Preview Abstract] 

UP8.00048: The origin of isotope fractionation in multicollector inductivelycoupledplasma massspectrometer: a case study of Mg isotope fractionation Zhengrong Wang, Dequan Xiao, Xi Shao Mg isotope fractionation in multicollector inductivelycoupledplasma massspectrometer (MCICPMS, Neptune) has been systematically investigated on a standard solution as a function of radiofrequency (RF) power, radius of skimmer cone orifice, Ar gas flow rate (sample and auxiliary gas), and voltage on extraction lens. Our experiments show that 26Mg/24Mg and 25Mg/24Mg ratios measured by Neptune are higher than their true ones by hundreds of per mil. This fractionation could be significantly reduced by decreasing RFpower, increasing radius of skimmer cone orifice, and increasing the Argas flow rate (more so for sample gas than for auxiliary gas). However, voltage of extraction lens has little effect on the fractionation. Our results suggest the plasma gas expansion and collision of ions between sample and skimmer cone is another mechanism for isotope fractionation that can better explain our experimental experiments. A qualitative model and a numerical simulation are presented in this study. The numerical simulation, based on plasma/ion dynamics, provides a detailed picture of the process. Our study proposes an alternative mechanism for the origin of isotope fractionation in Neptune, and improves analytical precisions for studying nontraditional metal isotopes. [Preview Abstract] 

UP8.00049: Measurements of lineaveraged electron density of pulsed plasmas using a HeNe laser interferometer in a magnetized coaxial plasma gun device D. Iwamoto, I. Sakuma, Y. Kitagawa, Y. Kikuchi, N. Fukumoto, M. Nagata In next step of fusion devices such as ITER, lifetime of plasmafacing materials (PFMs) is strongly affected by transient heat and particle loads during type I edge localized modes (ELMs) and disruption. To clarify damage characteristics of the PFMs, transient heat and particle loads have been simulated by using a plasma gun device. We have performed simulation experiments by using a magnetized coaxial plasma gun (MCPG) device at University of Hyogo. The lineaveraged electron density measured by a HeNe interferometer is 2x10$^{21}$ m$^{3}$ in a drift tube. The plasma velocity measured by a time of flight technique and ion Doppler spectrometer was 70 km/s, corresponding to the ion energy of 100 eV for helium. Thus, the ion flux density is 1.4x10$^{26}$ m$^{2}$s$^{1}$. On the other hand, the MCPG is connected to a target chamber for material irradiation experiments. It is important to measure plasma parameters in front of target materials in the target chamber. In particular, a vapor cloud layer in front of the target material produced by the pulsed plasma irradiation has to be characterized in order to understand surface damage of PFMs under ELMlike plasma bombardment. In the conference, preliminary results of application of the HeNe laser interferometer for the above experiment will be shown. [Preview Abstract] 

UP8.00050: Measurements of ion temperature and flow of pulsed plasmas produced by a magnetized coaxial plasma gun device using an ion Doppler spectrometer Y. Kitagawa, I. Sakuma, D. Iwamoto, Y. Kikuchi, N. Fukumoto, M. Nagata It is important to know surface damage characteristics of plasmafacing component materials during transient heat and particle loads such as type I ELMs. A magnetized coaxial plasma gun (MCPG) device has been used as transient heat and particle source in ELM simulation experiments. Characteristics of pulsed plasmas produced by the MCPG device play an important role for the plasma material interaction. In this study, ion temperature and flow velocity of pulsed He plasmas were measured by an ion Doppler spectrometer (IDS). The IDS system consists of a light collection system including optical fibers, 1mspectrometer and a 16 channel photomultiplier tube (PMT) detector. The IDS system measures the width and Doppler shift of HeII (468.58 nm) emission line with the time resolution of 1 $\mu $s. The Doppler broadened and shifted spectra were measured with 45 and 135 degree angles with respect to the plasmoid traveling direction. The observed emission line profile was represented by sum of two Gaussian components to determine the temperature and flow velocity. The minor component at around the wavelength of zerovelocity was produced by the stationary plasma. As the results, the ion velocity and temperature were 68 km/s and 19 eV, respectively. Thus, the He ion flow energy is 97 eV. The observed flow velocity agrees with that measured by a time of flight technique. [Preview Abstract] 

UP8.00051: Overview of the CCLDAS Dust Accelerator T. Munsat, A. Collette, K. Drake, E. Grun, M. Horanyi, S. Kempf, A. Mocker, P. Northway, A. Shu, Z. Sternovsky, E. Thomas The Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) has completed the construction of a new dust accelerator facility. The 3 MV electrostatic linear accelerator features a 20kV preaccelerating dust source which launches positively charged particles into the primary beamline. The beam consists of wellfocused and characterized dust particles in the size range of 0.1 to a few micrometers, and velocity range of 1 to 10's of km/s. The facility is used for impact experiments to study material damage characteristics, the production of secondary particles, plasma and neutrals, crater formation and film penetration studies, and for the testing and calibration of dedicated dust instruments. We present the technical details of the facility, its capabilities, our associated sample analysis tools, and the results of our recent campaign of impact and cratering experiments. Additionally, we discuss opportunities for the wider physics communities to use this new facility. [Preview Abstract] 

UP8.00052: The Motional Stark Effect with LaserInduced Fluorescence Diagnostic E.L. Foley, F.M. Levinton The motional Stark effect with laserinduced fluorescence diagnostic (MSELIF) was installed on NSTX for demonstration in the 2011 run year. The MSELIF will enable radially resolved measurements of the magnetic field pitch angle and magnitude, both of which can be used to constrain plasma equilibrium reconstructions. A diagnostic neutral beam with low axial energy spread, low divergence, and high reliability has been developed. It operates routinely at 35 kV and 40 mA. A laser has been developed with high power ($\sim$10 W) and optimal linewidth match to the neutral beam ($\sim$6 GHz). The laser wavelength is near 651 nm for a match to the Dopplershifted Balmeralpha transition in the beam neutrals. The unique highpower, moderate linewidth laser system utilizes a 19 emitter diode laser bar and feedback from a volume holographic grating. A magnetic shield protects the ion source from the NSTX stray fields. Initial data in a gasfilled torus and low magnetic fields was taken on NSTX and is presented here. [Preview Abstract] 

UP8.00053: The conceptual design of a robust, compact, modular tokamak reactor based on highfield superconductors D.G. Whyte, P. Bonoli, H. Barnard, C. Haakonsen, Z. Hartwig, C. Kasten, T. Palmer, C. Sung, D. Sutherland, L. Bromberg, F. Mangiarotti, J. Goh, B. Sorbom, J. Sierchio, J. Ball, M. Greenwald, G. Olynyk, J. Minervini Two of the greatest challenges to tokamak reactors are 1) large singleunit cost of each reactor's construction and 2) their susceptibility to disruptions from operation at or above operational limits. We present an attractive tokamak reactor design that substantially lessens these issues by exploiting recent advancements in superconductor (SC) tapes allowing peak field on SC coil $>$ 20 Tesla. A R$\sim $3.3 m, B$\sim $9.2 T, $\sim $ 500 MW fusion power tokamak provides high fusion gain while avoiding all disruptive operating boundaries (nowall beta, kink, and density limits). Robust steadystate core scenarios are obtained by exploiting the synergy of high field, compact size and ideal efficiency current drive using highfield side launch of Lower Hybrid waves. The design features a completely modular replacement of internal solid components enabled by the demountability of the coils/tapes and the use of an immersion liquid blanket. This modularity opens up the possibility of using the device as a nuclear component test facility. [Preview Abstract] 

UP8.00054: Multidimensional optimization of fusion reactors using heterogenous codes and engineering software Zachary Hartwig, Geoffrey Olynyk, Dennis Whyte Magnetic confinement fusion reactors are tightly coupled systems. The parameters under a designer's control, such as magnetic field, wall temperature, and blanket thickness, simultaneously affect the behavior, performance, and components of the reactor, leading to complex tradeoffs and design optimizations. In addition, the engineering analyses require nontrivial, selfconsistent inputs, such as reactor geometry, to ensure high fidelity between the various physics and engineering design codes. We present a framework for analysis and multidimensional optimization of fusion reactor systems based on the coupling of heterogeneous codes and engineering software. While this approach is widely used in industry, most codecoupling efforts in fusion have been focused on plasma and edge physics. Instead, we use a simplified plasma model to concentrate on how fusion neutrons and heat transfer affect the design of the first wall, breeding blanket, and magnet systems. The framework combines solid modeling, neutronics, and engineering multiphysics codes and software, linked across Windows and Linux clusters. Initial results for optimizing the design of a compact, highfield tokamak reactor based on hightemperature demountable superconducting coils and a liquid blanket are presented. [Preview Abstract] 

UP8.00055: Liquid immersion blanket design for use in a compact modular fusion reactor Brandon Sorbom, Justin Ball, Harold Barnard, Christian Haakonsen, Zachary Hartwig, Geoffrey Olynyk, Jennifer Sierchio, Dennis Whyte Traditional tritium breeding blankets in fusion reactor designs include a large amount of structural material. This results in complex engineering requirements, complicated sector maintenance, and marginal tritium breeding ratios (TBR). We present a conceptual design of a fully liquid blanket. To maximize tritium breeding volume, the vacuum vessel is completely immersed in a continuously recycled FLiBe blanket, with the exception of small support posts. FLiBe has a wide liquid temperature window (459 C to 1430 C), low electrical conductivity to minimize MHD effects, similar thermal/fluid characteristics to water, and is chemically inert. While tritium breeding with FLiBe in traditional blankets is poor, we use MCNP neutronics analysis to show that the immersion blanket design coupled with a beryllium neutron multiplier results in TBR $>$ 1. FLiBe is shown to be a sufficient radiation shield for the toroidal field magnets and can be used as a coolant for the vacuum vessel and divertor, allowing for a simplified singlephase, lowpressure, singlefluid cooling scheme. When coupled with a highfield compact reactor design, the immersion blanket eliminates the need for complex sector maintenance, allows the vacuum vessel to be a replaceable component, and reduces financial cost. [Preview Abstract] 

UP8.00056: Plasma performance required for fusion power control of tokamak power plant Ryoji Hiwatari, Kunihiko Okano A control of fusion power is a basic function of the fusion power plant. There are several options to control the fusion power; the plasma density control, tritium ratio control, helium ratio control, and plasma current control. To assess those control methods, analysis on MHD stability and current drive is carried out by EQLAUS/ERATO, and DRIVER codes using design parameters of a conceptual tokamak DEMO design, DemoCREST. First of all, density control can directly control the fusion power, but applicability of this method is found to be limited by compatibility with divertor plasma, where the high density is preferable for the detachment condition. Tritium ratio control is also found to be a candidate to control widely the fusion power maintaining the high density for the divertor detachment. However, this control method requires the high confinement improvement about HH=1.5. Helium ratio control is possibly one of the candidates. Wide range control of fusion power is confirmed concerning MHD stability and current drive property for DemoCREST, but it is not easy to control helium density/transport, especially active exhaust of helium. Plasma current control is also investigated. Finally, plasma performance required for the fusion power control is discussed. [Preview Abstract] 

UP8.00057: Rollback planning for a compact fusion system Simon Woodruff, Ronald Miller, James Stuber, Nate Hicks The development path for a compact ($<$100MWe) fusion power core is examined by use of advanced modeling to assess performance metrics at each step towards first commercial reactor. To guide the modeling, a new systems code is used to roll back from reactor, parameterizing and costing intermediate steps, such as Proof of Principle and fusion neutron source. Necessary performance metrics for current ramp, plasma beta, confinement scaling and profile control defined at each stage are assessed with physics models (CORSICA, NIMROD, DCON), constrained also by recent experimental results. A compact system such as a spheromak reduces operational and maintenance complexity, thereby increasing availability and reducing costs. Currents flowing the in the spheromak plasma produce toroidal field, so external windings are not necessary. Absent the TF, OH coil, inner shield and blanket, the power core becomes compact with small poloidal coils, and substantially lower cost than GWscale systems. Our patentpending quasi steadystate concept [1] includes an adiabatic compression of the plasma between short current drive periods to reach ignition conditions with converges, C (=a0/af) = 3. Compression allows the fusion island to become even more compact so that some technological issues, such as instantaneously high heat loads, can be avoided.\\[4pt] [1] S. Woodruff US Patent {\#} 12/706,963 [Preview Abstract] 

UP8.00058: FLASH simulations of 120MJ target explosions in LIFE reactor chamber Ryan Sacks, Gregory Moses, Milad Fatenejad The LIFE conceptual reactor design\footnote{Moses, E.I., Ignition on the National Ignition Facility: a path towards inertial fusion energy, \textit{Nucl. Fusion }\textbf{49} 104022} is a 12 m diameter reaction chamber with a steel first wall. The chamber is filled with 6 $\mu $g/cm$^{3}$ Xenon gas to protect the wall from fusion burn products. Indirect drive 120 MJ fusion targets are shot at 13 Hz repetition rate. For purposes of simulating the target explosion the target is approximated as a 1 g lead hohlraum. Fusion burn product energy is added to the Pb in a 100 ps flattop source at a rate of 12 MJ / 100 ps. The additional 13 MJ of fusion energy is assumed to be radiated as prompt xrays. The resulting spherical microexplosion of the heated Pb target into the surrounding Xe is simulated in 2D using the FLASH radiation hydrodynamics code. The FLASH code\footnote{Fryxell, B., Olson, K. \textit{et al.,}FLASH: An Adaptive Mesh Hydrodynamics Code for Modeling Astrophysical Thermonuclear Flashes, \textit{Astro. Journal Sup. Series.}, \textbf{131}, 273} is an AMR blockstructured, parallel scalable radiation hydrodynamics code. FLASH has separate electron and ion temperatures and single group or multigroup radiation diffusion. Shock generation in the Xe and mixing of the Pb and Xe behind the shock due to RayleighTaylor instability is investigated. Comparison with results from the 1D BUCKY radiation hydrodynamics code will be presented. This work was supported by Lawrence Livermore National Laboratory under contract number B587835. [Preview Abstract] 

UP8.00059: Ion concentration diffusion in inertially confined plasmas Grigory Kagan, XianZhu Tang Optimizing fusion yield in inertial confinement fusion (ICF) experiments requires number densities of the reactants to be equal throughout the fuel assembly. This condition can be easily satisfied during target fabrication. However, dynamical process of implosion gives rise to the interionspecies transport, resulting in these species' concentrations being perturbed from their initial values. In particular, classical, baro, electro and thermodiffusive mechanisms of such a transport should be distinguished. Baro and electrodiffusion ratios are obtained from ion fluid equations without invoking a kinetic calculation. Interestingly, plasma barodiffusion is found to be identical to its neutral counterpart. On the other hand, thermodiffusion ratios appearing in front of the ion and electron temperature gradients, as well as the classical diffusion coefficient, are intrinsically nonthermodynamic quantities. Their evaluation therefore does require a kinetic approach. By employing such an approach explicit dependence of the diffusion coefficients on the species' concentrations is found numerically for selected pairs of ion species. Initial implications of these newly obtained results are discussed. [Preview Abstract] 

UP8.00060: The compensation of the PC beam of the scattered beam by a foam target with FWM for beam steering Nobukazu Kameyama, Hiroki Yoshida It is necessary for the direct IFE to irradiate a target with laser beams. The laser beams have to be steered for accurate laser irradiation since the target is injected at several hundreds meters per second. The method of beam steering with phase conjugate mirrors is one of the candidates. In the method, probe beams whose energies are low enough not to damage it and expanded larger than the target radius are illuminated the target. The scattered beam enters into the phase conjugate mirrors and the phase conjugate beam is generated in the opposite direction of it. The phase conjugate beam retraces the same path for the property and irradiated the target. As the target has moved several hundreds micrometers for the high speed when the phase conjugate beam comes back, it is necessary for the phase conjugate beam to compensate for accurate irradiation. Four wave mixing is used as the compensation way. The interaction of two counterpropagating pump beams and a seed beam generates a phase conjugate beam in four wave mixing. The phase conjugate beam is adjustable by setting the angle between two pump beams. The compensation with a scattered beam by a foam target as a seed beam is reported. [Preview Abstract] 

UP8.00061: Target Injector and Sabot Remover for IFE Hiroki Yoshida, Nobukazu Kameyama Target injectors for IFE are required to inject targets to the reactor center at a velocity of over 100 m/s with accuracy of several millimeters. A target injector system with a magnetic sabot remover is developed to demonstrate injection of polystyrene targets. A typical target used in this study is 4.0 mm in diameter and 0.8 mg in weight. It is inserted in to an aluminum sabot that is 9.2 mm in outer diameter and 40 mm in length. They are accelerated together by a pneumatic gun. Before injection into the reactor, the sabot is removed for laser irradiation. The sabot remover is composed of Neodymium magnets array that generates Lorentz force as a result of interaction between the magnets' field and induced current on the sabot. The Neodymium magnets are 14 mm at inner diameter and 316 mT on its surface. The magnetic array is designed and optimized its magnets number for complete target extraction. The theoretically and experimentally confirmed deceleration rate of the sabot is 60.2 m/s/s per one meter. The targets are shot into the vacuum chamber after extraction from the sabot at accelerated velocity of 30 m/s. The experimentally obtained injection accuracy is 5.3 mm in horizontal direction and 4.8 mm in vertical direction. [Preview Abstract] 

UP8.00062: Improving Target Repeatability Yields Broader Results in Component Fabrication and Overall Build Sallee Klein, Eliseo Gamboa, Robb Gillespie, Channing Huntington, Christine Krauland, Carolyn Kuranz, Carlos di Stefano, Peter Susalla, Bruce Lairson, Fred Elsner, Paul Keiter, R. Paul Drake The University of Michigan has been fabricating targets for high energy density experiments since 2003. Our experiments study physics relevant to laboratory astrophysics. Machined acrylic structures serve as a backbone supporting all the components on our targets, as well as providing us with a method that eases our build. A most vital component to nearly every target we build, is shielding. Employing techniques to bend gold foils, enables complex geometries and eliminates seams that possibly allow unwanted emission in our diagnostics. Many of our experiments explore the dynamics of a radiative shock launched into xenon or argon gas. Polyimide (PI) tubing confines the gas and is transmissive to the diagnostic xrays used to probe the experiment. Recent interest in the shock dynamics of nonaxisymmetric shocks has lead to the development of PI tubes with noncircular cross sections. We present the techniques we use to produce repeatable targets as well as recent improvements in our techniques. [Preview Abstract] 
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