Characterization of NBI-driven shear Alfvén waves in the TJ-II stellarator using Mirnov probes and electrostatic potential fluctuation measurements
Year: 2026
Type: article
Abstract: We present the first experimental measurements of the toroidal mode number of shear Alfvén waves in the TJ-II stellarator, made possible by the installation and commissioning of a tri-axial helical array of Mirnov coils. A series of experiments were carried out in three different magnetic configurations to investigate counter-NBI driven modes. Co- and counter- electron-cyclotron current drive was used to modify the rotational transform ( ι ) profile leading to the destabilization of a varied set of Alfvén eigenmodes with different frequencies and mode numbers. Some modes exhibit radial asymmetries in their potential profiles, which is a clear indicator of mode coupling. We show that the induced changes in ι , that have a strong impact on the mode activity, cannot be measured experimentally with the motional Stark effect diagnostic. Instead, the shielding current diffusion equation is solved in cylindrical geometry to estimate these changes. We then calculate the incompressible shear Alfvén continuum for selected cases using STELLGAP and find reasonable consistency with observations.
Authors: P Pons-Villalonga, Á Cappa, E Ascasíbar, O S Kozachok, M B Dreval, K J McCarthy, J de la Riva Villén, J Martínez-Fernández, TJ-II Team
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,325
OpenAlex ID: W4407012540