Measurement of zero-frequency fluctuations generated by coupling between Alfven modes in the JET tokamak

Juan Ruiz Ruiz; Jeronimo Garcia; Michael Barnes; Mykola Dreval; Carine Giroud; Valerian H. Hall-Chen; Michael R. Hardman; Jon C. Hillesheim; Yevgen Kazakov; Samuele Mazzi; Felix I. Parra; Bhavin S. Patel; Alexander A. Schekochihin; Ziga Stancar; the JET Contributors; the EUROfusion Tokamak Exploitation Team

arXiv · 2407.01255

Measurement of zero-frequency fluctuations generated by coupling between Alfven modes in the JET tokamak

Juan Ruiz Ruiz·Jeronimo Garcia·Michael Barnes·Mykola Dreval·Carine Giroud·Valerian H. Hall-Chen·Michael R. Hardman·Jon C. Hillesheim·Yevgen Kazakov·Samuele Mazzi·Felix I. Parra·Bhavin S. Patel·Alexander A. Schekochihin·Ziga Stancar·the JET Contributors·the EUROfusion Tokamak Exploitation Team

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Abstract

We report the first experimental detection of a zero-frequency fluctuation that is pumped by an Alfv\`en mode in a magnetically confined plasma. Core-localized bidirectional Alfv\`en modes of frequency inside the toroidicity-induced gap (and its harmonics) exhibit three-wave coupling interactions with a zero-frequency fluctuation. The observation of the zero-frequency fluctuation is consistent with theoretical and numerical predictions of zonal modes pumped by Alfv\'en modes, and is correlated with an increase in the deep core ion temperature, temperature gradient, and confinement factor $H_{89,P}$. Despite the energetic particle transport induced by the Alfv\`en eigenmodes, the generation of a zero-frequency fluctuation that can suppress the turbulence leads to an overall improvement of confinement.

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Juan Ruiz Ruiz, Jeronimo Garcia, Michael Barnes, Mykola Dreval, Carine Giroud, Valerian H. Hall-Chen, Michael R. Hardman, Jon C. Hillesheim, Yevgen Kazakov, Samuele Mazzi, Felix I. Parra, Bhavin S. Patel, Alexander A. Schekochihin, Ziga Stancar, the JET Contributors, the EUROfusion Tokamak Exploitation Team. 2024-07-01. Measurement of zero-frequency fluctuations generated by coupling between Alfven modes in the JET tokamak. https://arxiv.org/abs/2407.01255

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