Researchers from the Max Planck Institute for Plasma Physics, including M. C. L. Morren, P. Mulholland, and their colleagues, have developed a new method to evaluate microinstabilities in magnetic confinement fusion devices. Their work, published in the Journal of Plasma Physics, aims to improve the understanding and prediction of small-scale turbulence that can limit the efficiency of fusion reactors.
Magnetic confinement fusion aims to harness the power of fusion reactions by confining hot plasma within a magnetic field. However, small-scale turbulence caused by microinstabilities can reduce the energy confinement time, making the reactions less efficient. The researchers have developed a semi-analytical dispersion relation that can describe two common types of microinstabilities: the ion temperature gradient (ITG) mode and the trapped-electron mode (TEM). This new approach is valid for arbitrary toroidal geometry, meaning it can be applied to various types of fusion devices, including tokamaks and stellarators.
The dispersion relation takes into account resonances with the magnetic drifts of ions and electrons, as well as non-local effects along the magnetic field line. It is also valid for both positive and negative growth rates and magnetic curvature. The researchers introduced several common approximation models for both the magnetic drift and finite Larmor radius (FLR) damping. Notably, the Padé approximation for FLR effect showed remarkable agreement with the baseline dispersion relation model at significantly reduced computational costs.
To verify their model, the researchers compared its solutions to high-fidelity linear gyrokinetic simulations. They used the exact eigenfunction of the electrostatic potential from simulations as a trial function, demonstrating good quantitative agreement for both ITGs and TEMs in shaped tokamaks and low-magnetic-shear stellarators. This verification step is crucial for ensuring the practical applicability of their model in real-world fusion devices.
The practical implications of this research for the energy sector are significant. By better understanding and predicting microinstabilities, fusion researchers can design more efficient and stable fusion reactors. This could accelerate the development of fusion power as a clean, sustainable energy source. The reduced computational costs associated with the Padé approximation also make the model more accessible and practical for routine use in fusion research and development.
In summary, the researchers have developed a robust and versatile tool for evaluating microinstabilities in magnetic confinement fusion devices. Their work represents a significant step forward in the quest for practical and efficient fusion power. The research was published in the Journal of Plasma Physics, providing a valuable resource for the scientific community.
This article is based on research available at arXiv.