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Non-equilibrium Microwave Plasma for Efficient High Temperature Chemistry
Published on: August 1, 2017
Magnetic-flux pumping in high-performance, stationary plasmas with tearing modes
C C Petty1, M E Austin, C T Holcomb
1General Atomics, San Diego, California 92186, USA.
Physical Review Letters
|March 5, 2009
Summary
Edge localized mode events in tokamak plasmas rapidly broaden the current density profile, but only when a specific tearing mode is present. This flux pumping phenomenon helps maintain plasma stability by preventing sawtooth instabilities.
Area of Science:
- Plasma physics
- Fusion energy research
- Magnetohydrodynamics
Background:
- Edge localized modes (ELMs) are transient plasma instabilities in tokamaks.
- Understanding ELM dynamics is crucial for stable fusion plasma confinement.
- Stationary, high-performance plasmas on DIII-D provide a relevant experimental environment.
Purpose of the Study:
- To analyze changes in magnetic field pitch angles during ELM events.
- To investigate the mechanism behind anomalous current density profile broadening.
- To determine the role of tearing modes in ELM-induced profile evolution.
Main Methods:
- Analysis of magnetic field pitch angle data during ELM events.
- Observation of high-performance, stationary plasmas in the DIII-D tokamak.
- Correlation of profile broadening with the presence of specific tearing modes (m/n=3/2).
Main Results:
- Rapid (<1 ms) broadening of the current density profile was observed during ELM events.
- This broadening occurred exclusively when an m/n=3/2 tearing mode was present.
- The phenomenon was identified as poloidal magnetic-flux pumping.
Conclusions:
- Poloidal magnetic-flux pumping is a key mechanism explaining anomalous current density broadening during ELMs.
- This broadening beneficially maintains the safety factor above unity.
- The observed effect helps forestall detrimental sawtooth instabilities, improving plasma confinement.
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