Download or read book Gyrokinetic Particle Simulation of a Multi ion Species Plasma written by Robert Andrew Santoro and published by . This book was released on 1994 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fully kinetic-particle simulations and hybrid simulations have been utilized for decades to investigate various fundamental plasma processes, such as magnetic reconnection, fast compressional waves, and wave-particle interaction. Nevertheless, due to disparate temporal and spatial scales between electrons and ions, existing fully kinetic-particle codes have to employ either unrealistically high electron-to-ion mass ratio, me/mi, or simulation domain limited to a few or a few ten's of the ion Larmor radii, or/and time much less than the global Alfven time scale in order to accommodate available computing resources. On the other hand, in the hybrid simulation, the ions are treated as fully kinetic particles but the electrons are treated as a massless fluid. The electron kinetic effects, e.g., wave-particle resonances and finite electron Larmor radius effects, are completely missing. Important physics, such as the electron transit time damping of fast compressional waves or the triggering mechanism of magnetic reconnection in collisionless plasmas is absent in the hybrid codes. Motivated by these considerations and noting that dynamics of interest to us has frequencies lower than the electron gyrofrequency, we planned to develop an innovative particle simulation model, gyrokinetic (GK) electrons and fully kinetic (FK) ions. In the GK-electron and FK-ion (GKe/FKi) particle simulation model, the rapid electron cyclotron motion is removed, while keeping finite electron Larmor radii, realistic me/mi ratio, wave-particle interactions, and off-diagonal components of electron pressure tensor. The computation power can thus be significantly improved over that of the full-particle codes. As planned in the project DE-FG02-05ER54826, we have finished the development of the new GK-electron and FK-ion scheme, finished its benchmark for a uniform plasma in 1-D, 2-D, and 3-D systems against linear waves obtained from analytical theories, and carried out a further convergence test and benchmark for a 2-D Harris current sheet against tearing mode and other instabilities in linear theories/models. More importantly, we have, for the first time, carried out simulation of linear instabilities in a 2-D Harris current sheet with a broad range of guide field BG and the realistic mi/me, and obtained important new results of current sheet instabilities in the presence of a finite BG. Indeed the code has accurately reproduced waves of interest here, such as kinetic Alfven waves, compressional Alfven/whistler wave, and lower-hybrid/modified two-stream waves. Moreover, this simulation scheme is capable of investigating collisionless kinetic physics relevant to magnetic reconnection in the fusion plasmas, in a global scale system for a long-time evolution and, thereby, produce significant new physics compared with both full-particle and hybrid codes. The results, with mi/me=1836 and moderate to large BG as in the real laboratory devices, have not been obtained in previous theory and simulations. The new simulation model will contribute significantly not only to the understanding of fundamental fusion (and space) plasma physics but also to DOE's SciDAC initiative by further pushing the frontiers of simulating realistic fusion plasmas.

Download or read book Gyrokinetic Particle Simulation of Ion Temperature Gradient Draft Instabilities written by W. W. Lee and published by . This book was released on 1987 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gyrokinetic Particle Simulation of Compressible Electromagnetic Turbulence in High Plasmas written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Supported by this award, the PI and his research group at the University of California, Irvine (UCI) have carried out computational and theoretical studies of instability, turbulence, and transport in laboratory and space plasmas. Several massively parallel, gyrokinetic particle simulation codes have been developed to study electromagnetic turbulence in space and laboratory plasmas. In space plasma projects, the simulation codes have been successfully applied to study the spectral cascade and plasma heating in kinetic Alfven wave turbulence, the linear and nonlinear properties of compressible modes including mirror instability and drift compressional mode, and the stability of the current sheet instabilities with finite guide field in the context of collisionless magnetic reconnection. The research results have been published in 25 journal papers and presented at many national and international conferences. Reprints of publications, source codes, and other research-related information are also available to general public on the PI's webpage (http://phoenix.ps.uci.edu/zlin/). Two PhD theses in space plasma physics are highlighted in this report.

Download or read book Center for Gyrokinetic Particle Simulations of Turbulent Transport in Burning Plasmas written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the Final Technical Report for University of Colorado's portion of the SciDAC project 'Center for Gyrokinetic Particle Simulation of Turbulent Transport.' This is funded as a multi-institutional SciDAC Center and W.W. Lee at the Princeton Plasma Physics Laboratory is the lead Principal Investigator. Scott Parker is the local Principal Investigator for University of Colorado and Yang Chen is a Co-Principal Investigator. This is Cooperative Agreement DE-FC02-05ER54816. Research personnel include Yang Chen (Senior Research Associate), Jianying Lang (Graduate Research Associate, Ph. D. Physics Student) and Scott Parker (Associate Professor). Research includes core microturbulence studies of NSTX, simulation of trapped electron modes, development of efficient particle-continuum hybrid methods and particle convergence studies of electron temperature gradient driven turbulence simulations. Recently, the particle-continuum method has been extended to five-dimensions in GEM. We find that actually a simple method works quite well for the Cyclone base case with either fully kinetic or adiabatic electrons. Particles are deposited on a 5D phase-space grid using nearest-grid-point interpolation. Then, the value of delta-f is reset, but not the particle's trajectory. This has the effect of occasionally averaging delta-f of nearby (in the phase space) particles. We are currently trying to estimate the dissipation (or effective collision operator). We have been using GEM to study turbulence and transport in NSTX with realistic equilibrium density and temperature profiles, including impurities, magnetic geometry and ExB shear flow. Greg Rewoldt, PPPL, has developed a TRANSP interface for GEM that specifies the equilibrium profiles and parameters needed to run realistic NSTX cases. Results were reported at the American Physical Society - Division of Plasma Physics, and we are currently running convergence studies to ensure physical results. We are also studying the effect of parallel shear flows, which can be quite strong in NSTX. Recent long-time simulations of electron temperature gradient driven turbulence, show that zonal flows slowly grow algebraically via the Rosenbluth-Hinton random walk mechanism. Eventually, the zonal flow gets to a level where it shear suppresses the turbulence. We have demonstrated this behavior with Cyclone base-case parameters, except with a 30% lower temperature gradient. We can demonstrate the same phenomena at higher gradients, but so far, have been unable to get a converged result at the higher temperature gradient. We find that electron ion collisions cause the zonal flows to grow at a slower rate and results in a higher heat flux. So, far all ETG simulations that come to a quasi-steady state show continued build up of zonal flow, see it appears to be a universal phenomena (for ETG). Linear and nonlinear simulations of Collisional and Collisionless trapped electron modes are underway. We find that zonal flow is typically important. We can, however, reproduce the Tannert and Jenko result (that zonal flow is unimportant) using their parameters with the electron temperature three times the ion temperature. For a typical weak gradient core value of density gradient and no temperature gradient, the CTEM is dominant. However, for a steeper density gradient (and still no temperature gradient), representative of the edge, higher k drift-waves are dominant. For the weaker density gradient core case, nonlinear simulations using GEM are routine. For the steeper gradient edge case, the nonlinear fluctuations are very high and a stationary state has not been obtained. This provides motivation for the particle-continuum algorithm. We also note that more physics, e.g. profile variation and equilibrium ExB shear flow should be significantly stabilizing, making such simulations feasible using standard delta-f techniques. This research is ongoing.

Download or read book Gyrokinetic Particle Simulation of Ion Temperature Gradient Drift Instabilities written by and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ion temperature gradient drift instabilities have been investigated using gyrokinetic particle simulation techniques for the purpose of identifying the mechanisms responsible for their nonlinear saturation as well as the associated anomalous transport. For simplicity, the simulation has been carried out in a shear-free slab geometry, where the background pressure gradient is held fixed in time to represent quasistatic profiles typical of tokamak discharges. It is found that the nonlinearly generated zero-frequency responses for the ion parallel momentum and pressure are the dominant mechanisms giving rise to saturation. This is supported by the excellent agreement between the simulation results and those obtained from mode coupling calculations.

Download or read book Center for Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasma written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The UCLA work on this grant was to design and help implement an object-oriented version of the GTC code, which is written in Fortran90. The GTC code is the main global gyrokinetic code used in this project, and over the years multiple, incompatible versions have evolved. The reason for this effort is to allow multiple authors to work together on GTC and to simplify future enhancements to GTC. The effort was designed to proceed incrementally. Initially, an upper layer of classes (derived types and methods) was implemented which called the original GTC code 'under the hood.' The derived types pointed to data in the original GTC code, and the methods called the original GTC subroutines. The original GTC code was modified only very slightly. This allowed one to define (and refine) a set of classes which described the important features of the GTC code in a new, more abstract way, with a minimum of implementation. Furthermore, classes could be added one at a time, and at the end of the each day, the code continued to work correctly. This work was done in close collaboration with Y. Nishimura from UC Irvine and Stefan Ethier from PPPL. Ten classes were ultimately defined and implemented: gyrokinetic and drift kinetic particles, scalar and vector fields, a mesh, jacobian, FLR, equilibrium, interpolation, and particles species descriptors. In the second state of this development, some of the scaffolding was removed. The constructors in the class objects now allocated the data and the array data in the original GTC code was removed. This isolated the components and now allowed multiple instantiations of the objects to be created, in particular, multiple ion species. Again, the work was done incrementally, one class at a time, so that the code was always working properly. This work was done in close collaboration with Y. Nishimura and W. Zhang from UC Irvine and Stefan Ethier from PPPL. The third stage of this work was to integrate the capabilities of the various versions of the GTC code into one flexible and extensible version. To do this, we developed a methodology to implement Design Patterns in Fortran90. Design Patterns are abstract solutions to generic programming problems, which allow one to handle increased complexity. This work was done in collaboration with Henry Gardner, a computer scientist (and former plasma physicist) from the Australian National University. As an example, the Strategy Pattern is being used in GTC to support multiple solvers. This new code is currently being used in the study of energetic particles. A document describing the evolution of the GTC code to this new object-oriented version is available to users of GTC.

Download or read book Gyrokinetic Particle Simulation of Neoclassical Transport written by W. W. Lee and published by . This book was released on 1995 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gyrokinetic Particle Simulation of Neoclassical Transport written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A time varying weighting ([delta] f) scheme for gyrokinetic particle simulation is applied to a steady state, multi-species simulation of neoclassical transport. Accurate collision operators conserving momentum and energy are developed and implemented. Simulation results using these operators are found to agree very well with neoclassical theory. For example, it is dynamically demonstrated in these multispecies simulations that like-particle collisions produce no particle flux and that the neoclassical fluxes are ambipolar for an ion-electron plasma. An important physics feature of the present scheme is the introduction of toroidal sheared flow to the simulations. Simulation results are in agreement with the existing analytical neoclassical theory of Hinton and Wong. The poloidal electric field associated with toroidal mass flow is found to enhance density gradient driven electron particle flux and the bootstrap current while reducing temperature gradient driven flux and current. Finally, neoclassical theory in steep gradient profile relevant to the edge regime is examined by taking into account finite banana width effects. In general, the present work demonstrates a valuable new capability for studying important aspects of neoclassical transport inaccessible by conventional analytical calculation processes.

Download or read book Gyrokinetic Particle Simulation Model written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A new type of particle simulation model based on the gyrophase-averaged Vlasov and Poisson equations is presented. The reduced system, in which particle gyrations are removed from the equations of motion while the finite Larmor radius effects are still preserved, is most suitable for studying low frequency microinstabilities in magnetized plasmas. It is feasible to simulate an elongated system (L/sub parallel/” L/sub perpendicular/) with a three-dimensional grid using the present model without resorting to the usual mode expansion technique, since there is essentially no restriction on the size of .delta.x/sub parallel/ in a gyrokinetic plasma. The new approach also enables us to further separate the time and spatial scales of the simulation from those associated with global transport through the use of multiple spatial scale expansion. Thus, the model can be a very efficient tool for studying anomalous transport problems related to steady-state drift-wave turbulence in magnetic confinement devices. It can also be applied to other areas of plasma physics.

Download or read book Center for Gyrokinetic MHD Hybrid Simulation of Energetic Particle Physics in Toroidal Plasmas CSEPP Final Report written by and published by . This book was released on 2012 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt: At Colorado University-Boulder the primary task is to extend our gyrokinetic Particle-in-Cell simulation of tokamak micro-turbulence and transport to the area of energetic particle physics. We have implemented a gyrokinetic ion/massless fluid electron hybrid model in the global [delta] f-PIC code GEM, and benchmarked the code with analytic results on the thermal ion radiative damping rate of Toroidal Alfven Eigenmodes (TAE) and with mode frequency and spatial structure from eigenmode analysis. We also performed nonlinear simulations of both a single-n mode (n is the toroidal mode number) and multiple-n modes, and in the case of single-n, benchmarked the code on the saturation amplitude vs. particle collision rate with analytical theory. Most simulations use the f method for both ions species, but we have explored the full-f method for energetic particles in cases where the burst amplitude of the excited instabilities is large as to cause significant re-distribution or loss of the energetic particles. We used the hybrid model to study the stability of high-n TAEs in ITER. Our simulations show that the most unstable modes in ITER lie in the rage of 10

Download or read book Gyrokinetic Particle Simulations of Reversed Shear Alfv n Eigenmodes in Fusion Plasmas written by Wenjun Deng and published by . This book was released on 2011 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: A nonlinear gyrokinetic simulation model, which recovers the ideal magnetohydrodynamic (MHD) theory in the linear long-wavelength regime is formulated for studying kinetic MHD processes in magnetized plasmas. This comprehensive formulation enables gyrokinetic simulation of both pressure gradient-driven and current-driven instabilities including ideal and kinetic ballooning modes, kink modes, and shear Alfvén waves, as well as their nonlinear interactions in multi-scale simulations. Implemented in the gyrokinetic toroidal code (GTC), the new formulation is verified in simulations of reversed shear Alfvén eigenmode (RSAE) in fusion plasmas. The antenna excitation of RSAE provides verifications of its mode structure, frequency and damping rate from the initial perturbation simulation with kinetic thermal ions. When excited by fast ions, their non-perturbative contributions modify the mode structure relative to the ideal MHD theory. With inclusion of thermal plasma pressure, the mode frequency increases due to the elevation of the Alfvén continuum by the geodesic compressibility. The GTC simulations have been benchmarked with extended hybrid MHD-gyrokinetic simulations. The verified gyrokinetic simulation model is applied to studying the linear properties of RSAE driven by density gradient of neutral beam injected fast ions in a well-diagnosed DIII-D tokamak experiment (discharge #142111). GTC simulations find that weakly damped RSAE exists due to toroidal coupling and other geometric effects. Various damping and driving mechanisms are identified and measured in the simulations, which shows that accurate damping and growth rate calculation requires true mode structure from non-perturbative, fully self-consistent simulation. The mode structure has no up-down symmetry mainly due to the radial symmetry breaking by the radial variation of fast ion density gradient, as measured in the experiment by electron cyclotron emission imaging. The RSAE frequency up-sweeping and the mode transition from RSAE to toroidal Alfvén eigenmode are in good agreement with the experimental results when scanning the values of the minimum safety factor in simulations. Good agreements in frequencies, growth rates, and mode structures are obtained among simulations of gyrokinetic codes GTC and GYRO, and an MHD-hybrid code TAEFL, which provide further verification and validation of the gyrokinetic model for simulating the kinetic MHD processes. As a prelude to nonlinear simulations of RSAE and associated fast ion transport, properties of microturbulence in reversed shear plasmas are also studied.

Download or read book Gyrokinetic Particle Simulation of Spectral Cascade and Collisionless Dissipation in Kinetic Alfven Wave Turbulence written by Cheng, Xi and published by . This book was released on 2011 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: The issue of spectral cascade and plasma heating in Alfvenic turbulence is a major unsolved problem in plasma physics. The possible heating mechanisms depend on the direction of spectral cascade with respect to the background magnetic field, i.e. perpendicular vs. parallel, and could be Landau damping of kinetic Alfven waves, ion cyclotron resonant heating and the stochastic heating by dispersive Alfven waves. Our focus is on the perpendicular cascade in the Alfvenic turbulence. In this thesis project, a massively parallel 3D gyrokinetic particle-in-cell (PIC) code has been developed to study spectral cascading and dissipation of Alfvenic turbulence with fully self-consistent nonlinear kinetic effects. This thesis describes the physical model, the progress of the code development including numerical techniques and verification of the code, and the simulation result of spectral cascade of kinetic Alfven wave turbulence in both inertial and dissipation ranges. We observe an energy spectrum characterized by a power law with an index of "-5/3 in the inertial range, which recovers magnetohychrodynamic model results. We also observe a break point in magnetic energy spectrum at the ion gyroradius scale followed by a steepened spectra, which suggests that Landau damping due to wave- particle resonance is a plausible mechanism of the collisionless dissipation complement with the ion cyclotron resonance and the nonlinear stochastic heating.

Download or read book Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas GPS TTBP Final Report written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this project is the development of the Gyrokinetic Toroidal Code (GTC) Framework and its applications to problems related to the physics of turbulence and turbulent transport in tokamaks, . The project involves physics studies, code development, noise effect mitigation, supporting computer science efforts, diagnostics and advanced visualizations, verification and validation. Its main scientific themes are mesoscale dynamics and non-locality effects on transport, the physics of secondary structures such as zonal flows, and strongly coherent wave-particle interaction phenomena at magnetic precession resonances. Special emphasis is placed on the implications of these themes for rho-star and current scalings and for the turbulent transport of momentum. GTC-TTBP also explores applications to electron thermal transport, particle transport; ITB formation and cross-cuts such as edge-core coupling, interaction of energetic particles with turbulence and neoclassical tearing mode trigger dynamics. Code development focuses on major initiatives in the development of full-f formulations and the capacity to simulate flux-driven transport. In addition to the full-f -formulation, the project includes the development of numerical collision models and methods for coarse graining in phase space. Verification is pursued by linear stability study comparisons with the FULL and HD7 codes and by benchmarking with the GKV, GYSELA and other gyrokinetic simulation codes. Validation of gyrokinetic models of ion and electron thermal transport is pursed by systematic stressing comparisons with fluctuation and transport data from the DIII-D and NSTX tokamaks. The physics and code development research programs are supported by complementary efforts in computer sciences, high performance computing, and data management.

Download or read book Plasma Simulation Using Gyrokinetic Gyrofluid Hybrid Models written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We are developing kinetic ion models for the simulation of extended MHD phenomena. The model they have developed uses full Lorentz force ions, and either drift-kinetic or gyro-kinetic electrons. Quasi-neutrality is assumed and the displacement current is neglected. They are also studying alpha particle driven Toroidal Alfven Eigenmodes (TAE) in the GEM gyrokinetic code [Chen 07]. The basic kinetic ion MHD model was recently reported in an invited talk given by Dan Barnes at the 2007 American Physical Society - Division of Plasma Physics (APS-DPP) and it has been published [Jones 04, Barnes 08]. The model uses an Ohm's law that includes the Hall term, pressure term and the electron inertia [Jones 04]. These results focused on the ion physics and assumed an isothermal electron closure. It is found in conventional gyrokinetic turbulence simulations that the timestep cannot be made much greater than the ion cyclotron period. However, the kinetic ion MHD model has the compressional mode, which further limits the timestep. They have developed an implicit scheme to avoid this timestep constraint. They have also added drift kinetic electrons. This model has been benchmarked linearly. Waves investigated where shear and compressional Alfven, whisterl, ion acoustic, and drift waves, including the kinetic damping rates. This work is ongoing and was first reported at the 2008 Sherwood Fusion Theory Conference [Chen 08] and they are working on a publication. They have also formulated an integrated gyrokinetic electron model, which is of interest for studying electron gradient instabilities and weak guide-field magnetic reconnection.

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2003 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Alfven Waves in Gyrokinetic Plasmas written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A brief comparison of the properties of Alfven waves that are based on the gyrokinetic description with those derived from the MHD equations is presented. The critical differences between these two approaches are the treatment of the ion polarization effects. As such, the compressional Alfven waves in a gyrokinetic plasma can be eliminated through frequency ordering, whereas geometric simplifications are needed to decouple the shear Alfven waves from the compressional Alfven waves within the context of MHD. Theoretical and numerical procedures of using gyrokinetic particle simulation for studying microturbulence and kinetic-MHD physics including finite Larmor radius effects are also presented.