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Theory of two threshold fields for relativistic runaway electrons
Pavel Aleynikov1, Boris N Breizman2
1ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France.
Physical Review Letters
|May 2, 2015
Summary
This study introduces a kinetic theory for relativistic runaway electrons in tokamaks, revealing two critical electric fields for their behavior and avalanche hysteresis. This research clarifies the dynamics of runaway electrons impacting toroidal current decay.
Area of Science:
- Plasma Physics
- Fusion Energy
- Kinetic Theory
Background:
- Relativistic runaway electrons are crucial in tokamak plasma dynamics.
- Understanding their behavior is key for fusion energy research and plasma control.
- Existing theories may not fully capture near-critical electric field phenomena.
Purpose of the Study:
- Develop a rigorous kinetic theory for relativistic runaway electrons.
- Investigate electron behavior in near-critical electric fields within tokamaks.
- Explain the mechanism of hysteresis in runaway electron avalanches.
Main Methods:
- Formulation of a kinetic theory for relativistic runaway electrons.
- Analysis of electron distribution functions under specific electric field conditions.
- Theoretical modeling of runaway electron avalanche dynamics.
Main Results:
- A detailed distribution function for runaway electrons was derived.
- Two distinct threshold electric fields were identified: one for sustainment and one for avalanche onset.
- A mechanism explaining hysteresis in the runaway electron avalanche was described.
Conclusions:
- The near-threshold regime of runaway electrons is critical for understanding toroidal current decay.
- The identified threshold fields provide new insights into tokamak plasma behavior.
- This kinetic theory offers a framework for predicting and mitigating runaway electron effects.
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