Author: W. W. LeePublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
KINETIC STUDIES OF MICROINSTABILITIES IN TOROIDAL PLASMAS: SIMULATION ANDTHEORY.
Author: W. W. LeeKinetic Studies of Microinstabilities in Toroidal Plasmas
Author: Taik Soo HahmPublisher:
ISBN:
Category : Computer simulation
Languages : en
Pages : 7
Book Description
Kinetic Studies of Microinstabilities in Toroidal Plasmas
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 8
Book Description
A comprehensive program for the development and use of particle simulation techniques for solving the gyrokinetic Vlasov-Maxwell equations on massively parallel computers has been carried out at Princeton Plasma Physics Laboratory. This is a key element of our ongoing theoretical efforts to systematically investigate physics issues vital to understanding tokamak plasmas. In this paper, our focus is on spatial-gradient-driven microinstabilities. Their importance is supported by the recent progress in achieving a physics-based understanding of anomalous transport in toroidal systems which has been based on the proposition that these drift-type electrostatic modes dependent on ion temperature gradient (ITG) and trapped particle effects are dominant in the bulk (''confinement'') region. Although their presence is consistent with a number of significant confinement trends, results from high temperature tokamaks such as TFTR have highlighted the need for better insight into the nonlinear properties of such instabilities in long-mean-free-path plasmas. In addressing this general issue, we report important new results including (i) the first fully toroidal 3D gyrokinetic simulation of ITG modes and (ii) realistic toroidal eigenmode calculations demonstrating the unique capability to deal with large scale kinetic behavior extending over many rational surfaces. The effects of ITG modes (iii) on the inward pinch of impurities in 3D slab geometry and (iv) on the existence of microtearing modes in 2D slab are also discussed. Finally, (v) sheared toroidal flow effects on trapped-particle modes are presented.
Toroidal Microinstability Studies of High Temperature Tokamaks
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Results from comprehensive kinetic microinstability calculations are presented showing the effects of toroidicity on the ion temperature gradient mode and its relationship to the trapped-electron mode in high-temperature tokamak plasmas. The corresponding particle and energy fluxes have also been computed. It is found that, although drift-type microinstabilities persist over a wide range of values of the ion temperature gradient parameter [eta]/sub i/ /equivalent to/ (dlnT/sub i//dr)/(dlnn/sub i//dr), the characteristic features of the dominant mode are those of the /eta//sub i/-type instability when /eta//sub i/> /eta//sub ic/ /approximately/1.2 to 1.4 and of the trapped-electron mode when /eta//sub i/
Study of Micro-instabilities in Toroidal Plasmas with Negative Magnetic Shear
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The micro-instabilities driven by a parallel velocity shear, and a temperature gradient of ions are studied in toroidal plasmas with negative magnetic shear. Both the fluid and the gyro-kinetic formulations are investigated. It is found that for a broad range of parameters, the linear growth rates of the modes are lower, and the threshold temperature gradient[eta][sub icr] is higher for plasmas with negative magnetic shear compared to plasmas with positive magnetic shear of equal magnitude. The reduction in the growth rate (with negative shear), although not insignificant, does not seem to be enough to account for the dramatic improvement in the confinement observed experimentally. Other possible physical mechanisms for the improved confinement are discussed.
Long-wavelength Microinstabilities in Toroidal Plasmas
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 28
Book Description
Realistic kinetic toroidal eigenmode calculations have been carried out to support a proper assessment of the influence of long-wavelength microturbulence on transport in tokamak plasmas. In order to efficiently evaluate large-scale kinetic behavior extending over many rational surfaces, significant improvements have been made to a toroidal finite element code used to analyze the fully two-dimensional (r, [theta]) mode structures of trapped-ion and toroidal ion temperature gradient (ITG) instabilities. It is found that even at very long wavelengths, these eigenmodes exhibit a strong ballooning character with the associated radial structure relatively insensitive to ion Landau damping at the rational surfaces. In contrast to the long-accepted picture that the radial extent of trapped-ion instabilities is characterized by the ion-gyroradius-scale associated with strong localization between adjacent rational surfaces, present results demonstrate that under realistic conditions, the actual scale is governed by the large-scale variations in the equilibrium gradients. Applications to recent measurements of fluctuation properties in TFTR L-mode plasmas indicate that the theoretical trends appear consistent with spectral characteristics as well as rough heuristic estimates of the transport level. Benchmarking calculations in support of the development of a three-dimensional toroidal gyrokinetic code indicate reasonable agreement with respect to both the properties of the eigenfunctions and the magnitude of the eigenvalues during the linear phase of the simulations of toroidal ITG instabilities.
Nuclear Science Abstracts
Author: Kinetic Studies of Anomalous Transport
Author: W. M. TangPublisher:
ISBN:
Category : Transport theory
Languages : en
Pages : 16
Book Description
Energy Research Abstracts
Author: Long-wavelength Microinstabilities in Toroidal Plasmas
Author: G. RewoldtPublisher:
ISBN:
Category : Drift waves
Languages : en
Pages : 27
Book Description