Gyrokinetic Studies Of Particle Transport In Tokamaks
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| Author | : Carlos Andres Estrada-Mila |
| Publisher | : |
| Total Pages | : 113 |
| Release | : 2006 |
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| ISBN | : |
In this dissertation a systematic study of particle transport in tokamaks, using gyrokinetic simulations and theory, is presented. This work can be divided into three major parts. The first part studies particle transport in pure plasmas and investigates the origin and nature of flows against density gradients, also known as particle pinches. It is found that these pinches, which are primarily driven by temperature gradients, can also be responsible for the density peaking observed in experiments such as ASDEX-U, DIII-D or JET. The second part of this work studies plasmas with multiple ion species. First, we study helium ash transport and its effects in the core of a reactor plasma, finding that a helium pinch driven by finite toroidicity can be created in some cases. Second, we study deuterium and tritium plasmas from the point of view of isotope flow separation, finding that in a 50-50 deuterium-tritium plasma, a small fuel separation may occur. Finally, the last part studies the behavior of energetic species in reactor plasmas. It is found that alpha particles interact strongly with the background turbulence. Perhaps the most surprising finding is that the fluxes per particle of alphas can be stronger than the fluxes per particle of deuterium (i.e. main ion), as opposed to ``conventional wisdom'' which assumes that species with large gyroradii do not significantly interact with the turbulence.
| Author | : |
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| Total Pages | : 44 |
| Release | : 2015 |
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| Author | : Pierre Cottier |
| Publisher | : LAP Lambert Academic Publishing |
| Total Pages | : 128 |
| Release | : 2014-04-01 |
| Genre | : |
| ISBN | : 9783659411038 |
The magnetic confinement in tokamaks is for now the most advanced way towards energy production by nuclear fusion. Both theoretical and experimental studies showed that rotation generation can increase its performance by reducing the turbulent transport in tokamak plasmas. The rotation influence on the heat and particle fluxes is studied along with the angular momentum transport with the quasi-linear gyro-kinetic eigenvalue code QuaLiKiz. For this purpose, the QuaLiKiz code is modified in order to take the plasma rotation into account and compute the angular momentum flux. It is shown that QuaLiKiz framework is able to correctly predict the angular momentum flux including the ExB shear induced residual stress as well as the influence of rotation on the heat and particle fluxes. The different contributions to the turbulent momentum flux are studied and successfully compared against both non-linear gyro-kinetic simulations and experimental data.
| Author | : Thibaut Vernay |
| Publisher | : |
| Total Pages | : 202 |
| Release | : 2013 |
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| Author | : Sara Moradi |
| Publisher | : LAP Lambert Academic Publishing |
| Total Pages | : 168 |
| Release | : 2010-08 |
| Genre | : |
| ISBN | : 9783838326566 |
One of the least understood areas of the plasma particle or heat transport is the turbulent transport. In this work the main focus is on the development and data analysis of anomalous transport characteristics (transport coefficients and fluxes) under fusion conditions in large tokamaks. Fluid and gyro-kinetic models are used and obtained results are compared. A model based on fractional kinetics for the study of the SOL turbulent transport characteristics, where non-Gaussian PDFs are observed, is developed.
| Author | : R.B. White |
| Publisher | : Elsevier |
| Total Pages | : 374 |
| Release | : 2017-01-31 |
| Genre | : Science |
| ISBN | : 1483293262 |
This is a graduate textbook on tokamak physics, designed to provide a basic introduction to plasma equilibrium, particle orbits, transport, and those ideal and resistive magnetohydrodynamic instabilities which dominate the behavior of a tokamak discharge, and to develop the mathematical methods necessary for their theoretical analysis.
| Author | : |
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| Total Pages | : |
| Release | : 2011 |
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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.
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| Publisher | : |
| Total Pages | : 75 |
| Release | : 2011 |
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The three-year project GPS-TTBP resulted in over 152 publications and 135 presentations. This summary focuses on the scientific progress made by the project team. A major focus of the project was on the physics intrinsic rotation in tokamaks. Progress included the first ever flux driven study of net intrinsic spin-up, mediated by boundary effects (in collaboration with CPES), detailed studies of the microphysics origins of the Rice scaling, comparative studies of symmetry breaking mechanisms, a pioneering study of intrinsic torque driven by trapped electron modes, and studies of intrinsic rotation generation as a thermodynamic engine. Validation studies were performed with C-Mod, DIII-D and CSDX. This work resulted in very successful completion of the FY2010 Theory Milestone Activity for OFES, and several prominent papers of the 2008 and 2010 IAEA Conferences. A second major focus was on the relation between zonal flow formation and transport non-locality. This culminated in the discovery of the ExB staircase - a conceptually new phenomenon. This also makes useful interdisciplinary contact with the physics of the PV staircase, well-known in oceans and atmospheres. A third topic where progress was made was in the simulation and theory of turbulence spreading. This work, now well cited, is important for understanding the dynamics of non-locality in turbulent transport. Progress was made in studies of conjectured non-diffusive transport in trapped electron turbulence. Pioneering studies of ITB formation, coupling to intrinsic rotation and hysteresis were completed. These results may be especially significant for future ITER operation. All told, the physics per dollar performance of this project was quite good. The intense focus was beneficial and SciDAC resources were essential to its success.
| Author | : Mitsuru Kikuchi |
| Publisher | : Springer |
| Total Pages | : 412 |
| Release | : 2015-09-03 |
| Genre | : Technology & Engineering |
| ISBN | : 3319189050 |
This book reviews recent progress in our understanding of tokamak physics related to steady state operation, and addresses the scientific feasibility of a steady state tokamak fusion power system. It covers the physical principles behind continuous tokamak operation and details the challenges remaining and new lines of research towards the realization of such a system. Following a short introduction to tokamak physics and the fundamentals of steady state operation, later chapters cover parallel and perpendicular transport in tokamaks, MHD instabilities in advanced tokamak regimes, control issues, and SOL and divertor plasmas. A final chapter reviews key enabling technologies for steady state reactors, including negative ion source and NBI systems, Gyrotron and ECRF systems, superconductor and magnet systems, and structural materials for reactors. The tokamak has demonstrated an excellent plasma confinement capability with its symmetry, but has an intrinsic drawback with its pulsed operation with inductive operation. Efforts have been made over the last 20 years to realize steady state operation, most promisingly utilizing bootstrap current. Frontiers in Fusion Research II: Introduction to Modern Tokamak Physics will be of interest to graduate students and researchers involved in all aspects of tokamak science and technology.
| Author | : |
| Publisher | : |
| Total Pages | : 92505 |
| Release | : 2006 |
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A general geometry gyro-kinetic model for particle simulation of plasma turbulence in tokamak experiments is described. It incorporates the comprehensive influence of noncircular cross section, realistic plasma profiles, plasma rotation, neoclassical (equilibrium) electric fields, and Coulomb collisions. An interesting result of global turbulence development in a shaped tokamak plasma is presented with regard to nonlinear turbulence spreading into the linearly stable region. The mutual interaction between turbulence and zonal flows in collisionless plasmas is studied with a focus on identifying possible nonlinear saturation mechanisms for zonal flows. A bursting temporal behavior with a period longer than the geodesic acoustic oscillation period is observed even in a collisionless system. Our simulation results suggest that the zonal flows can drive turbulence. However, this process is too weak to be an effective zonal flow saturation mechanism.
