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Turbulence-driven bootstrap current in low-collisionality tokamaks
C J McDevitt1, Xian-Zhu Tang, Zehua Guo
1Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Physical Review Letters
|December 3, 2013
Summary
A new mechanism drives bootstrap current in collisionless plasmas via resonant electron scattering. This microturbulent process complements neoclassical collisional effects, impacting tokamak reactor plasma currents.
Area of Science:
- Plasma Physics
- Fusion Energy Research
- Kinetic Theory
Background:
- Neoclassical bootstrap current is crucial for tokamak reactor equilibrium plasma currents.
- Existing models rely on collisional effects to establish electron equilibrium.
Purpose of the Study:
- To investigate a novel mechanism for driving bootstrap current in collisionless plasmas.
- To explore the role of resonant electron scattering by drift wave microturbulence.
- To quantify the interplay between collisional and microturbulent mechanisms.
Main Methods:
- Utilized a linearized Fokker-Planck collision operator.
- Modeled resonant scattering of electrons by drift wave microturbulence.
- Computed plasma current considering both collisions and scattering.
Main Results:
- Demonstrated that resonant electron scattering can drive bootstrap current in collisionless plasmas.
- Showed this microturbulent mechanism establishes equilibrium between trapped and passing electrons.
- Quantified the relative contributions of collisional and scattering mechanisms.
Conclusions:
- Resonant scattering offers an alternative pathway to bootstrap current generation.
- Microturbulence can significantly influence plasma current profiles in tokamaks.
- Understanding these mechanisms is vital for future fusion reactor designs.
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