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Author: Vasudeva Raghavendra Kowsik Bodi Publisher: ISBN: Category : Languages : en Pages : 72
Book Description
Energy from nuclear fusion of Hydrogen isotopes is a possible alternative to fossil fuels. For this to be of practical utility, confinement of Hydrogen in a plasma state for a minimum duration is necessary. Since confinement is strongly affected by radial transport processes, understanding the observed modes of radial transport in confined plasma is of vital importance for progress towards fusion energy. The present dissertation is aimed at studying radial (cross-field) transport in the tokamak edge plasma. The present thesis is divided into three parts : In the first part, we present a model of generation of intermittent convective meso-scale structures (blobs) based on the synergy of the interchange drive and nonlinear effects associated with drift-wave turbulence. In the second part, we attempt to explain the preferential propagation of blobs radially outward as a consequence of the radially decreasing density of a confined plasma. In the third part, we present a model for simulating anomalous radial transport in kinetic codes for tokamak edge plasma.
Author: Vasudeva Raghavendra Kowsik Bodi Publisher: ISBN: Category : Languages : en Pages : 72
Book Description
Energy from nuclear fusion of Hydrogen isotopes is a possible alternative to fossil fuels. For this to be of practical utility, confinement of Hydrogen in a plasma state for a minimum duration is necessary. Since confinement is strongly affected by radial transport processes, understanding the observed modes of radial transport in confined plasma is of vital importance for progress towards fusion energy. The present dissertation is aimed at studying radial (cross-field) transport in the tokamak edge plasma. The present thesis is divided into three parts : In the first part, we present a model of generation of intermittent convective meso-scale structures (blobs) based on the synergy of the interchange drive and nonlinear effects associated with drift-wave turbulence. In the second part, we attempt to explain the preferential propagation of blobs radially outward as a consequence of the radially decreasing density of a confined plasma. In the third part, we present a model for simulating anomalous radial transport in kinetic codes for tokamak edge plasma.
Author: William Davis Lee Publisher: ISBN: Category : Languages : en Pages : 16
Book Description
Anomalous momentum transport has been observed in Alcator C-Mod tokamak plasmas. The time evolution of core impurity toroidal rotation velocity profiles has been measured with a crystal x-ray spectrometer array. Following the L-mode to EDA (enhanced D[/sub/ alpha]) H-mode transition in both Ohmic and ICRF heated discharges, the ensuing co-current toroidal rotation velocity, which is generated in the absence of any external momentum source, is observed to propagate in from the edge plasma to the core with a time scale of order of the observed energy confinement time, but much less than the neo-classical momentum confinement time. The steady state toroidal rotation velocity profiles in EDA H-mode plasmas are relatively flat and the momentum transport can be simulated with a simple diffusion model. Assuming the L-H transition produces an instantaneous edge velocity source (which disappears at the H- to L-mode transition), the momentum transport may be characterized by a diffusivity, with values of 0.07 m2/s during EDA H-mode and 0.2 m2/s in L-mode. These values are large compared to the calculated neo-classical momentum diffusivities. Velocity profiles during ELM-free H-modes are centrally peaked, which suggests inward momentum convection; the observed profiles are matched with simulations including an inward convection velocity of 10 m/s. In EDA H-mode discharges which develop internal transport barriers, the velocity profiles become hollow in the center indicating the presence of a negative radial electric field well in the vicinity of the barrier foot.
Author: Andrei N. Simakov Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
Effects of neutral particles on plasma flows and radial transport in a collision-dominated plasma are discussed, with a particular attention given to the modifications due to a poloidal variation of the neutral density. It is found that neutrals are of no importance if the radial particle transport is on a Pfirsch-Schlüter level. If, on the other hand, anomalous effects increase this transport to the Pfirsch-Schlüter radial heat transport level or higher, neutral effects become important in determining the radial heat transport, radial electric field, and the ion parallel flow velocity. Keywords: transport phenomena; neutral particle effects; edge plasma.
Author: Publisher: ISBN: Category : Aeronautics Languages : en Pages : 652
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Davide Galassi Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Nuclear fusion could offer a new source of stable, non-CO2 emitting energy. Today, tokamaks offer the best performance by confining a high temperature plasma by means of a magnetic field. Two of the major technological challenges for the operation of tokamaks are the power extraction and the confinement of plasma over long periods. These issues are associated with the transport of particles and heat, which is determined by turbulence, from the central plasma to the edge zone. In this thesis, we model turbulence in the edge plasma. We study in particular the divertor configuration, in which the central plasma is isolated from the walls by means of an additional magnetic field. This complex magnetic geometry is simulated with the fluid turbulence code TOKAM3X, developed in collaboration between the IRFM at CEA and the M2P2 laboratory of the University of Aix-Marseille.A comparison with simulations in simplified geometry shows a similar intermittent nature of turbulence. Nevertheless, the amplitude of the fluctuations, which has a maximum at the equatorial plane, is greatly reduced near the X-point, where the field lines become purely toroidal, in agreement with the recent experimental data. The simulations in divertor configuration show a significantly higher confinement than in circular geometry. A partial inhibition of the radial transport of particles at the X-point contributes to this improvement. This mechanism is potentially important for understanding the transition from low confinement mode to high confinement mode, the intended operational mode for ITER.
Author: Sergei Krasheninnikov Publisher: Springer ISBN: 9783030495961 Category : Science Languages : en Pages : 0
Book Description
This book reviews the current state of understanding concerning edge plasma, which bridges hot fusion plasma, with a temperature of roughly one million degrees Kelvin with plasma-facing materials, which have melting points of only a few thousand degrees Kelvin. In a fact, edge plasma is one of the keys to solution for harnessing fusion energy in magnetic fusion devices. The physics governing the processes at work in the edge plasma involves classical and anomalous transport of multispecies plasma, neutral gas dynamics, atomic physics effects, radiation transport, plasma-material interactions, and even the transport of plasma species within the plasma-facing materials. The book starts with simple physical models, then moves on to rigorous theoretical considerations and state-of-the-art simulation tools that are capable of capturing the most important features of the edge plasma phenomena. The authors compare the conclusions arising from the theoretical and computational analysis with the available experimental data. They also discuss the remaining gaps in their models and make projections for phenomena related to edge plasma in magnetic fusion reactors.
Author: Vasudeva Raghavendra Kowsik Bodi
Author: Vasudeva Raghavendra Kowsik Bodi
Author: A. K. Prinja
Author: George Vayakis
Author: William Davis Lee
Author: Ronald D. Stambaugh
Author: Andrei N. Simakov
Author: 
Author: Davide Galassi
Author: D. J. Sigmar
Author: Sergei Krasheninnikov