Fluctuations in the Edge Plasma of the Tosca Tokamak PDF Download
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Author: A. A. Howling
Publisher:
ISBN:
Category : Tokamaks
Languages : en
Pages : 215
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Author: A. A. Howling
Publisher:
ISBN:
Category : Tokamaks
Languages : en
Pages : 215
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Author: Jeffrey A. Masucci
Publisher:
ISBN:
Category :
Languages : en
Pages : 66
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Author: Wei Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 15
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Author:
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ISBN:
Category : Controlled fusion
Languages : en
Pages : 112
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Author: R. H. Cohen
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Category :
Languages : en
Pages :
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Results of recent modeling of tokamak edge plasma with the turbulence code BOUT are presented. In previous studies with BOUT the background profiles of plasma density and temperature were set as flux surface functions. However in the divertor region of a tokamak the temperature is typically lower and density is higher than those at the mid-plane. To account for this in the present study a poloidal variation of background plasma density and temperature is included to provide a more realistic model. For poloidally uniform profiles of the background plasma the calculated turbulence amplitude peaks near outer mid-plane, while in the divertor region the amplitude is small. However, present simulations show that as the background plasma profiles become more poloidally non-uniform the amplitude of density fluctuations, {tilde n}{sub i}, starts peaking in the divertor. It is found that in the divertor region the amplitude of n{sub i} fluctuations grows approximately linearly with the local density of the background plasma, n{sub i0}, while the amplitude of T{sub e} and {phi} fluctuations is positively correlated with the local electron temperature, T{sub e0}. Correlation analysis shows that plasma turbulence is isolated by the x-points.
Author:
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 936
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Author: R. L. Kubena
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 228
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An experimental investigation of low frequency floating potential fluctuations (f d"200 kHz) in a research tokamak plasma using two spatially separated electrostatic probes has been performed. The spectra, correlation length, and the phase velocity of the fluctuations in both the radial and azimuthal direction have been determined. The propagation velocity in the toroidal direction was also measured and was found to be in the direction of electron current flow. The waves traveled azimuthally in the ion diamagnetic drift direction, even after the usual E x B rotation was taken into account. The electron density fluctuations associated with these oscillations were large, [delta]n/n [approximately] 0.35 - 0.50. The spectra were found to have regularly spaced peaks which seemed to be related to specific azimuthal modes (m =1,2,3, ..., etc.) A parametric study was made to determine what effect plasma parameters had on these peaks. During periods of high electron density in the first 2 msec of the plasma lifetime, strong sawtooth type oscillations were observed. These oscillations typically had frequencies of approximately 10 kHz and were also present when large amounts of neutral gas were added during the discharge by a process called "gas puffing." The results are compared with experimental observations made on other plasma devices with electric and magnetic probes and with microwave and CO2 laser scattering techniques. (The scattering measurements are complimentary to the probe measurements since, in the former case, the wavelength is fixed by the scattering angle, but the oscillations could not be spatially localized.) The oscillations in the Caltech torus were probably related to a drift-tearing type instability which is thought to play a major role in the anomalous particle and energy flux observed in tokamaks. Comparisons are made between current theory and the experimental results. However, the theory for the observed oscillations is still in a rudimentary stage of development, and it is hoped that the present investigation will stimulate future analytical work.
Author:
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 1478
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Author: S. Coda
Publisher:
ISBN:
Category :
Languages : en
Pages : 14
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The spectrum of turbulent density fluctuations at long poloidal wavelengths in the edge plasma of the DIII-D tokamak peaks at nonzero radial wave number. The associated electric-potential fluctuations cause sheared E x B flows primarily in the poloidal direction. These zonal flows have been predicted by theory and are believed to regulate the overall level of turbulence and anomalous transport. The quantitative features of the measured spectra are in good agreement with predictions.
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Category :
Languages : en
Pages : 0
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