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Book Anomalous Transport in the Tokamak Edge

Download or read book Anomalous Transport in the Tokamak Edge written by George Vayakis and published by . This book was released on 1991 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Anomalous Radial Transport in Tokamak Edge Plasma

Download or read book Anomalous Radial Transport in Tokamak Edge Plasma written by Vasudeva Raghavendra Kowsik Bodi and published by . This book was released on 2010 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Observations of Anomalous Transport in Tokamak Plasmas with No Momentum Input

Download or read book Observations of Anomalous Transport in Tokamak Plasmas with No Momentum Input written by William Davis Lee and published by . This book was released on 2003 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Anomalous Perturbative Transport in Tokamaks Due to Drift wave Turbulence

Download or read book Anomalous Perturbative Transport in Tokamaks Due to Drift wave Turbulence written by Anne A. Thoul and published by . This book was released on 1992 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Models of Coupled Transport to Investigate Anomalous Transport in Tokamaks

Download or read book Models of Coupled Transport to Investigate Anomalous Transport in Tokamaks written by Renato Gatto and published by . This book was released on 1996 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Anomalous Transport Modelling of Tokamak Plasmas

Download or read book Anomalous Transport Modelling of Tokamak Plasmas written by and published by . This book was released on 1992 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theory based transport simulations of DIII-D, JET, ITER are compared to experimental data using a combination of anamolous transport models. The Multiple-mode Transport Model is calibrated to a give set of L-mode and H-mode discharges with an emphasis on testing the adequacy of anomalous flux contributions from drift/[eta]{sub i} and resistive ballooning mode theories. A survey of possible additions and/or alternatives to the model from recent theories on neoclassical MHD effects, hot ion modes, circulating electron modes, and high-m tearing modes is also included.

Book Anomalous Transport and Confinement Scaling Studies in Tokamaks

Download or read book Anomalous Transport and Confinement Scaling Studies in Tokamaks written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In addressing the general issue of anomalous energy transport, this paper reports on results of theoretical studies concerning: (1) the characteristics and relative strength of the dominant kinetic instabilities likely to be present under realistic tokamak operating conditions; (2) specific nonlinear processes relevant to the saturation and transport properties of drift-type instabilities; (3) the construction of semiempirical models for electron thermal transport and the scaling trends inferred from them; and (4) the application of specific anomalous transport models to simulate recent large-scale confinement experiments (TFTR and JET) and current drive experiments.

Book On the Edge of Magnetic Fusion Devices

Download or read book On the Edge of Magnetic Fusion Devices written by Sergei Krasheninnikov and published by Springer. This book was released on 2021-09-09 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Turbulent Correlations and Anomalous Transport in Tokamaks

Download or read book Turbulent Correlations and Anomalous Transport in Tokamaks written by A. Thyagaraja and published by . This book was released on 1988 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Conceptual and Experimental Bases of Theories of Anomalous Transport in Tokamaks

Download or read book Conceptual and Experimental Bases of Theories of Anomalous Transport in Tokamaks written by F. A. Haas and published by . This book was released on 1986 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Control of Internal Transport Barriers in Magnetically Confined Tokamak Fusion Plasmas

Download or read book Control of Internal Transport Barriers in Magnetically Confined Tokamak Fusion Plasmas written by Soma Raj Panta and published by . This book was released on 2020 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the Tokamak plasma, for fusion to be possible, we have to maintain a very high temperature and density at the core at the same time keeping them low at the edge to protect the machine. Nature does not favor gradients. Gradients are source of free energy that causes instability. But we require a large gradient to get energy from plasma fusion. We therefore, apply a huge magnetic field on the order of few Tesla (1 T-10 T) that confines the plasma in the core, maintaining gradients. Due to gradients in density of charged particles (ions and electrons), there is an electric field in the plasma. Heat and particle transport takes place from core to edge mainly through anomalous transport while the E x B velocity sheer acts to reduce the transport of heat and particles. The regime at which the E x B velocity shear exceeds the maximum linear instability growth rate, as a result, the transport of particles and heat gets locally reduced is termed as the formation of a transport barrier. This regime can be identified by calculating the transport coefficients in the local region. Sometimes it can be observed in the edge where it is called an edge barrier while if it is near the core it is an internal transport barrier. There is a positive feedback loop between gradients and transport barrier formation. External heating and current drives play an important role to control such barriers. Auxiliary heating like neutral beam injection (NBI) and radio frequency (RF) heating can be used at a proper location (near the core of the plasma) to trigger or (far outside from the core) to destroy those barriers. Barrier control mechanism in the burning plasmas in international thermonuclear test reactor (ITER) parameter scenarios employing fusion power along with auxiliary heating source and pellets are studied. Continuous bombardment with pellets in the interval of a fraction of a second near the core of the burning plasma results in a stronger barrier. Frozen pellets along with auxiliary heating are found to be helpful to control the barriers in the tokamak plasmas. Active control mechanism for transport barriers using pellets and auxiliary heating in one of tokamaks in United States (DIII-D) parameter scenarios are presented in which intrinsic hysteresis is used as a novel control tool. During this process, a small background NBI power near the core assists in maintaining the profile. Finally, a self-sustained control mechanism in the presence of core heating is also explored in Japanese tokamak (JT-60SA) parameter scenarios. Centrally peaked narrow NBI power is mainly absorbed by ions with a smaller fraction by the electrons. Heat exchange between the electron and ion channels and heat conduction in the electron channel are found to be the main processes that govern this self control effect. A strong barrier which is formed in the ion channel is found to play the main role during the profile steepening while the burst after the peaked core density is found to have key role in the profile relaxation.

Book Some Aspects of Anomalous Transport in Tokamaks

Download or read book Some Aspects of Anomalous Transport in Tokamaks written by Steven C. Cowley and published by . This book was released on 1985 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: