Recent research conducted by J. Varela and his team at the Institute for Fusion Studies and the National Institute for Fusion Science sheds light on the intricate dynamics of plasma behavior in nuclear fusion reactors. Their study, published in the journal Nuclear Fusion, focuses on the generation of shear flows (SFs) induced by Alfven Eigenmodes (AEs) and energetic particle modes (EPMs) during the saturation phase of plasma in the Large Helical Device (LHD).
The implications of this research are significant for the future of nuclear fusion energy, as managing these plasma behaviors is crucial for the stability and efficiency of fusion reactors. SFs play a pivotal role in regulating the saturation of AEs and EPMs, influencing the transport of energetic particles (EPs) and thermal plasma, and even contributing to the formation of transport barriers. As Varela notes, “Understanding how shear flows interact with plasma instabilities is essential for developing stable and efficient fusion reactors.”
The experiments carried out during the 23rd and 24th LHD experimental campaigns revealed fascinating insights. In particular, shots 176490 and 179697 demonstrated the destabilization of magnetohydrodynamic (MHD) bursts and energetic-ion-driven resistive interchange modes (EICs). Notably, charge exchange spectroscopy measurements indicated that the generation of SFs by AEs and EPMs was largely independent of perturbations from the neutral beam injector, a common tool for heating plasma.
The research utilized advanced nonlinear simulations through the gyro-fluid code FAR3d, which unveiled the formation of zonal structures, particularly SFs, during the saturation phase of Toroidal Alfven Eigenmodes (TAEs). These simulations suggested that radial electric fields, powered by energy transfers from unstable modes to the thermal plasma, were responsible for the generation of SFs. “The strongest shear flows were observed during the EIC bursting phase, highlighting the complex interplay of plasma dynamics,” Varela explained.
As the energy sector grapples with the challenge of harnessing fusion power, this research provides a clearer understanding of plasma behavior that could lead to more robust and reliable fusion systems. The insights gained from these experiments and simulations could influence the design of future reactors, making them more efficient and capable of sustaining the conditions necessary for fusion. The potential for commercial fusion energy to revolutionize the global energy landscape hinges on such foundational research, which is paving the way for practical applications.
For those interested in delving deeper into this compelling study, the full article is available in Nuclear Fusion, a leading journal in the field. To learn more about the work of J. Varela and his team, you can visit their affiliation at Institute for Fusion Studies, Department of Physics, University of Texas at Austin.
