Multi–diagnostic comparison of turbulence in negative and positive triangularity plasmas in the TCV tokamak

Turbulence-driven anomalous transport plays a pivotal role in the performance of modern-day tokamaks. Plasma shaping can be useful in reducing turbulence and improving the confinement in fusion devices. Since the first development of the negative triangularity scenario in the TCV tokamak [1], numerous studies have demonstrated that negative triangularity plasmas exhibit superior confinement properties compared to their positive triangularity counterpart. Consequently, understanding and comparing turbulence across different plasma triangularities is paramount to developing a transport model.

This study employs three fluctuation diagnostics to characterize temperature and density turbulence from the plasma core to its edge in the Tokamak à Configuration Variable (TCV). Specifically, we utilize the Short-pulse Reflectometer (SPR) [2, 3] and the Tangential Phase Contrast Imaging (TPCI) systems [4] for characterizing density fluctuations and the Correlation Electron Cyclotron Emission (CECE) [5] diagnostic to characterize temperature fluctuations. Recently, SPR measurements have been validated with a full-wave synthetic diagnostic [6]. The details of the diagnostics and comparison results will be discussed.

[1] Moret et al., Phys. Rev Lett. 79, 2057, (1997).

[2] PA Molina Cabrera et al, Rev. of Sci. Instrum. 90, 123501, (2019)

[3] U Kumar et al., to be submitted, (2024)

[4] A Iantchenko Plasma Phys. Controll. Fusion 65, 02005, (2023)

[5] M Fontana, Rev. Scient. Instrm. 88, 083506, (2017)

[6] O Krutkin et al., Nucl. Fusion, 64, 026010, (2024)