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Active MHD Spectroscopy for Plasma Stability Studies
| Author: | Maurer D. A. |
| Coauthor: | |
| Institution : | Columbia University |
| Abstract text: | Actively probing plasmas using magnetic perturbations designed to resonate with distinct field line structures is an important and useful diagnostic tool for MHD equilibrium and stability studies. This technique of MHD spectroscopy is capable of measuring important characteristics of long wavelength MHD instabilities that are common to many ICC configurations. Magnetic perturbations used to actively probe plasma response in these experiments are generated using simple saddle coil antenna arrays with spatial and temporal Fourier components that couple to the MHD resonance under investigation. Using these resonant fields the amplitude and phase response of stable and unstable modes can be measured, and the effects of plasma rotation on stable and unstable mode behavior can be studied and quantified. By applying these perturbations to stable configurations, mode approach to marginal stability can also be detected. Examples of the use of MHD spectroscopy for understanding resistive wall mode and tearing mode behavior in tokamaks will be used to highlight these diagnostic techniques. In addition to the use of simple response functions to characterize the mode a dynamical approach allows comparison of experimental data with evolution equations for MHD mode behavior under active spectroscopy using magnetic perturbations with temporally and spatially varying phase. Possible future applications of this technique as applied to different ICCs will be discussed.
Acknowledging important contributions from C. J. Cates, M. E. Mauel, G. A. Navratil,
T. S. Pedersen, and M. A. Shilov
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