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Classical impurity ion confinement in a toroidal magnetized fusion plasma
S T A Kumar1, D J Den Hartog, K J Caspary
1Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. stkumar@wisc.edu
Physical Review Letters
|May 1, 2012
Summary
High-resolution measurements show classical ion confinement in toroidal plasmas. Reduced magnetic turbulence allowed observation of impurity ion dynamics, revealing temperature screening effects.
Area of Science:
- Plasma Physics
- Fusion Energy Research
- Atomic and Molecular Physics
Background:
- Understanding ion transport is crucial for magnetic confinement fusion.
- Neoclassical transport theory predicts enhanced ion diffusion due to particle drifts.
- Previous experiments lacked the resolution to isolate classical transport effects.
Purpose of the Study:
- To provide the first experimental evidence of classical ion confinement in a toroidal plasma.
- To investigate impurity ion dynamics under conditions minimizing neoclassical effects.
- To assess the role of temperature screening in impurity transport.
Main Methods:
- High-resolution measurements of fully stripped carbon ion density profiles in MST reversed-field pinch plasmas.
- Experiments conducted with significantly reduced magnetic turbulence.
- Methane pellet injection used to probe impurity particle confinement time.
Main Results:
- Impurity density profiles evolved to a hollow shape, supporting the temperature screening mechanism.
- Classical ion confinement was observed, distinct from neoclassical predictions.
- Impurity confinement time was found to be sensitive to residual magnetic fluctuation levels.
Conclusions:
- Classical ion transport mechanisms are experimentally validated in toroidal plasmas.
- Temperature screening plays a significant role in impurity profile evolution.
- Minimizing magnetic turbulence is key to observing classical transport phenomena and understanding impurity behavior.
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