This title appears in the Scientific Report :
2003
Please use the identifier:
http://hdl.handle.net/2128/248 in citations.
Modeling of rotating plasma states and their stability accounting for neutral beam injection and helical perturbations
Modeling of rotating plasma states and their stability accounting for neutral beam injection and helical perturbations
The revisited neoclassical transport theory for a collisional edge layer with steep radial gradients in the toroidal damping time scale is extended, to include the faster poloidal damping time scale. The evolution of the toroidal and poloidal rotation speeds is determined within the frame of neoclas...
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Personal Name(s): | Yarim, Cuma |
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Daybelge, Umur / Nicolai, Albert | |
Contributing Institute: |
Institut für Plasmaphysik; IPP |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2003
|
Physical Description: |
56 p. |
Document Type: |
Book |
Research Program: |
Kernfusion und Plasmaforschung |
Series Title: |
Berichte des Forschungszentrums Jülich
4091 |
Link: |
OpenAccess |
Publikationsportal JuSER |
The revisited neoclassical transport theory for a collisional edge layer with steep radial gradients in the toroidal damping time scale is extended, to include the faster poloidal damping time scale. The evolution of the toroidal and poloidal rotation speeds is determined within the frame of neoclassical theory by two equations accounting for ambipolarity and momentum conservation. The timescales $\tau_{T}$ and $\tau_{P}$ for the evolution of toroidal, U$_{T}$, and poloidal, U$_{P}$, velocities are quite different and allow for an expansion with respect to $\tau_{P}$/$\tau_{T}$. The truncation of the expansion at the linear term, i.e., U$_{T}$=U$_{T0}$+U$_{T1}$, and U$_{P}$= U$_{P0}$+ U$_{Pl}$, yields four equations for U$_{T0,1}$ and U$_{P0,1}$: A diffusion equation for U$_{T0}$, an ordinary differential equation for U$_{P0,1}$ depending on the U$_{T0}$-profile, an evolution equation for U$_{T1}$, depending on the U$_{P0}$-profile are obtained by separating the secular parts from the fast varying parts. Resorting to TEXTOR-data and assuming in a first step a stationary profile for U$_{T0}$ the time evolution of U$_{P0}$ is computed, in particular it is shown that the U$_{P0}$ is, in general, close to its neoclassical value, but has the characteristic deviations at the boundary as demanded by the revisited neoclassical theory. In order to determine the stability behavior of poloidal and toroidal rotations in a tokamak plasma, the dependence of the poloidal velocity on time and initial velocity is analysed. It is observed, that the poloidal and toroidal spin-up tendencies are strongly coupled by nonlocal interactions, although these evolve essentially on différent time scales. Rotation speeds are also influenced by charge exchange interactions, neutral beam injection, or a radial polarization current. |