Rotating magnetohydrodynamic and trapped hot-ion induced internal kinks
Varadarajan, V.
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https://hdl.handle.net/2142/21572
Description
Title
Rotating magnetohydrodynamic and trapped hot-ion induced internal kinks
Author(s)
Varadarajan, V.
Issue Date
1993
Doctoral Committee Chair(s)
Miley, George H.
Department of Study
Nuclear, Plasma, and Radiological Engineering
Discipline
Nuclear Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Nuclear
Physics, Fluid and Plasma
Language
eng
Abstract
As a new and significant contribution to the tokamak literature, the linear internal MHD kink modes in finite aspect-ratio axisymmetric toroidally rotating tokamak equilibria and their kinetic modifications owing to the presence of hot ions are computationally studied herein using a bilinear form derived using a Lagrangian perturbation procedure. As a practical application, the rotating MHD and kinetic internal kinks are calculated in finite aspect-ratio TFTR- and ITER-like geometries. The MHD and kinetic modes of the rotating tokamak plasmas are found to be significantly destabilized by the centrifugal effects at rotation speeds in the range of $10\sp4$-10$\sp5$ rad/s at normal discharge densities. The kinetic instability model provides a unified description of several features of the 'fishbone'-like oscillations such as the slow mode rotating at the plasma rotation frequency, the fast mode with high rotation frequency, and variation of the slow as well as fast mode frequencies with plasma rotation. The slow kinetic modes rotate close to mean plasma rotation speeds, and the fast kinetic modes rotate at about 10$\sp5$ rad/s. The fast mode rotation frequencies are in the range of the magnetic-precession frequencies of the deeply trapped ions. Also, the kinetic kink modes are found to be excitable in ITER-like ignited tokamak configurations owing to hot fusion products such as alphas.
Also, a feasibility study of adaptive distributed parameter control of thermokinetics is demonstrated. Fast transport simulation and control are explored using a nonlinear Galerkin procedure, and a MIMO self-tuning control algorithm. It is found that only the density control can achieve reasonable power set-point follow-up, and that more popular control schemes such as auxiliary power control are not adequate to provide real-world power swings greater than 50-100 MW around the set point.
The several computational modules developed for this thesis are as follows. The equilibrium calculations are implemented in a code called FLOE (FLOw Equilibrium). The instability models are implemented in a code called PINK (Plasma INternal Kinks). The control algorithms and simulations are implemented in a code called ACT (Adaptive Control of Thermokinetics).
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