Investigations of Electron Cyclotron Emission from a Tokamak Plasma PDF Download
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Author: David John Campbell
Publisher:
ISBN:
Category : Electrons
Languages : en
Pages :
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Author: David John Campbell
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ISBN:
Category : Electrons
Languages : en
Pages :
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Author: Paul Gray Stokes
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ISBN:
Category : Plasma (Ionized gases)
Languages : en
Pages : 390
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Category :
Languages : en
Pages :
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The absorption of 60 GHz electron cyclotron waves, with the extraordinary mode and an oblique angle of propagation, has been investigated in the PLT tokamak in the regime of down-shifted frequencies. The production of energetic electrons, with energies of up to 300 to 400 keV, peaks at values of toroidal field (approx. =29 kG) for which the wave frequency is significantly smaller than the electron cyclotron frequency in the whole plasma region. The observations are consistent with the predictions of the relativistic theory of electron cyclotron damping at down-shifted frequency. Existing rf sources make this process a viable method for assisting the current ramp-up, and for heating the plasma of present large tokamaks.
Author: Marc Alexander Sengstacke
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ISBN:
Category : Electrons
Languages : en
Pages : 538
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Author:
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Category :
Languages : en
Pages : 79
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This thesis studies several tearing mode problems from both theoretical and experimental points of view. A major part of this thesis is to demonstrate that Electron Cyclotron Emission (ECE) is an excellent diagnostic for studying an MHD mode structure and its properties in a tokamak plasma. It is shown that an MHD mode can be detected from the electron temperature fluctuations measured by ECE. The amplitude and phase profiles of the fluctuations contain detailed information about the mode structure. The ECE fluctuation phase profile indicates the magnetic island deformation due to the combination of sheared flow and viscosity. A model is presented to relate qualitatively the observed phase gradient to the local magnetic field, flow velocity shear and viscosity in a 2D slab geometry, using an ideal Ohm's law and the plasma momentum equation including flow and viscosity. Numerical solution of the resultant Grad-Shafranov-like equation describing the deformed island shows that the experimentally observed value of the phase gradient can be obtained under realistic parameters for the shear in the flow velocity and viscosity. A new approach to the tearing mode stability boundary and saturation level is also presented.
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Category :
Languages : en
Pages : 6
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The great stumbling block in the quest for fusion power using magnetic confinement devices is anomalous transport. It is conjectured that turbulent plasma fluctuations may be responsible for the degraded energy confinement observed in experiments. There exists a clear need for more detailed experimental studies of plasma microturbulence. We have started a set of experiments to measure electron temperature and density fluctuations using electron cyclotron emission (ECE). The ECE systems will employ auto-correlation and cross-correlation techniques to measure radiation from the Advanced Toroidal Facility at Oak Ridge National Laboratory (ORNL) and also from the Texas Experimental Tokamak (TEXT) at the University of Texas. This set of experiments on a stellerator and a tokamak will allow a unique comparative study of the fluctuation physics in the two different magnetic configurations. This work is in support of the United States Department of Energy Tokamak Transport Initiative and involves a collaborative effort between Auburn University, Georgia Institute of Technology, the University of Texas at Austin and ORNL. 3 refs.
Author: Horacio Gasquet
Publisher:
ISBN:
Category : Tokamaks
Languages : en
Pages : 486
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Author: Benjamin John Tobias
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ISBN: 9781124509778
Category :
Languages : en
Pages :
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Energy production through the burning of fossil fuels is an unsustainable practice. Exponentially increasing energy consumption and dwindling natural resources ensure that coal and gas fueled power plants will someday be a thing of the past. However, even before fuel reserves are depleted, our planet may well succumb to disastrous side effects, namely the build up of carbon emissions in the environment, thereby triggering world-wide climate change and the countless industrial spills of pollutants that continue to this day. Many alternatives are currently being developed, but none has so much promise as fusion nuclear energy, the energy of the sun. The confinement of hot plasma at temperatures in excess of 100 million Kelvin by a carefully arranged magnetic field for the realization of a self-sustaining fusion power plant requires new technologies and improved understanding of fundamental physical phenomena. Millimeter wave imaging of electron cyclotron radiation lends insight into the spatial and temporal behavior of electron temperature fluctuations and instabilities, providing a powerful diagnostic for investigations into basic plasma physics and nuclear fusion reactor operation. This dissertation presents the design and implementation of a new generation of Electron Cyclotron Emission Imaging (ECEI) diagnostics on toroidal magnetic fusion confinement devices, such as tokamaks and stellarators, around the world. The underlying physics of cyclotron radiation in fusion plasmas is reviewed, and a thorough discussion of millimeter wave imaging techniques and heterodyne radiometry in ECEI follows. The imaging of turbulence and fluid flows has evolved over half a millennium since Leonardo da Vinci's first sketches of cascading water, and applications for ECEI in fusion research are broad ranging. Two areas of physical investigation are discussed in this dissertation: the identification of poloidal shearing in Alfvén eigenmode structures predicted by hybrid gyrofluid-magnetohydrodynamic (gyrofluid-MHD) modeling, and magnetic field line displacement during precursor oscillations associated with the sawtooth crash, a disruptive instability observed both in tokamak plasmas with high core current and in the magnetized plasmas of solar flares and other interstellar plasmas. Understanding both of these phenomena is essential for the future of magnetic fusion energy, and important new observations described herein underscore the advantages of imaging techniques in experimental physics.
Author: Mark Albert Meier
Publisher:
ISBN:
Category : Tokamaks
Languages : en
Pages : 218
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Author: Shao Che
Publisher:
ISBN: 9781303537936
Category :
Languages : en
Pages :
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Magnetic confinement thermonuclear fusion energy has long been considered a potential substitute for fossil fuels as the major long term energy source of global development. With its effective magnetic field configuration, tokamak devices have received extensive investigations with advancement in plasma diagnostic tools [1]. A comprehensive millimeter wave passive imaging diagnostic system for measurement of electron temperature fluctuations in tokamaks has been conceived and developed at the University of California at Davis utilizing the Electron Cyclotron Emission from the plasma [2,3]. HL-2A is a diverted tokamak developed and constructed by the Southwestern Institute of Physics (SWIP) in Chengdu, China based on the vacuum vessel and magnetic coil system of the former German ASDEX device. Previous millimeter wave diagnostics including reflectometry and ECE radiometry have been installed on the tokamak for electron density and temperature profile measurements [4,5]. However, there is increasing need for fluctuation measurements over the plasma volume for research into plasma confinement and instabilities. Through a collaborative effort between the Davis Millimeter Wave Research Center (DMRC) of the University of California at Davis and SWIP, a new 192 channel (24 vertical by 8 radial) Electron Cyclotron Emission Imaging system has been designed and constructed at UC Davis for a 2 dimensional coverage of the plasma temperature with high spatial resolution. A new imaging optical system with zooming capability is optimized for the available port window on HL-2A with a versatile coverage of the plasma volume ranging from a magnification ratio of 1 to 1.8. A novel local oscillator (LO) optical system is designed to maintain the optimum illumination onto the antenna array under different operating frequencies of the Backward Wave Oscillator. The RF electronics for double down-conversion heterodyne frequency mixing and signal detection is developed from the DIIID ECEI system with improved sensitivity and reduced noise. Other millimeter wave components such as the dual-dipole antenna array and dichroic plate high-pass filters are fabricated and characterized. The complete system is assembled and calibrated in the laboratory at UC Davis with extensive testing and characterization of the functionality of each subsystem.
