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Persistence of Ion Temperature Gradient Turbulent Transport at Finite Normalized Pressure
A Ishizawa1, D Urano1, Y Nakamura1
1Graduate School of Energy Science, Kyoto University, Uji 611-0011, Japan.
Physical Review Letters
|August 7, 2019
Summary
Plasma turbulence transport is not reduced by increasing plasma beta. Instead, ion energy diffusivity remains constant, while electron energy diffusivity rises due to magnetic field structure changes affecting ion-temperature-gradient driven turbulence.
Area of Science:
- Plasma Physics
- Fusion Energy Research
- Computational Physics
Background:
- Understanding plasma turbulent transport is crucial for magnetic confinement fusion.
- The dependence of turbulent transport on plasma beta (β) is a key factor for reactor performance.
- Previous studies often assumed a fixed magnetic field structure, neglecting self-consistent effects.
Purpose of the Study:
- To investigate the plasma beta dependence of electromagnetic turbulent transport.
- To analyze the impact of self-consistent changes in the equilibrium magnetic field on turbulence.
- To clarify the underlying physical mechanisms driving turbulent transport at different beta values.
Main Methods:
- Utilizing advanced gyrokinetic simulations.
- Incorporating self-consistent evolution of the equilibrium magnetic field.
- Analyzing ion-temperature-gradient (ITG) driven turbulence and its interaction with magnetic field structures.
Main Results:
- Ion energy transport due to ITG turbulence does not decrease with increasing beta.
- Ion energy diffusivity remains largely unchanged, while electron energy diffusivity increases with beta.
- Changes in magnetic field structure, influenced by the Pfirsch-Schluter current, significantly alter turbulence dynamics.
Conclusions:
- The self-consistent change in magnetic field structure with beta weakens the suppression of ITG modes.
- Nonlinear zonal flow production is suppressed by magnetic field modifications.
- These effects are particularly significant with increasing global magnetic shear, impacting confinement predictions.
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