Advanced tokamak scenarios in negative triangularity at TCV

One way to improve plasma confinement is the operation in an advanced tokamak (AT) scenario, which requires highly tailored current density profiles by using non-inductive current sources to achieve an elevated or even slightly reversed core safety factor (q) profile. These q-profiles lead to the formation of an internal transport barrier (ITB), hence a significant increase in beta. If the bootstrap current increase due to the ITB is sufficiently strong, it can moreover open the path towards fully non-inductive long-pulse tokamak operation.

While the operation in an AT scenario is extensively studied in positive triangularity (PT) plasmas, particularly in view of ITER [1,2], this work presents experimental and modelling results in negative triangularity (NT) plasmas. NT further favours high-beta operation by inherently improving the edge confinement without accessing H-mode and thus allows ELM-free operation. We will present first results from limited and diverted NT configurations at the tokamak à configuration variable (TCV) demonstrating high-beta operation with (electron-)ITBs.

[1] C. Piron et al 2025, 9th AAPPS, conference contribution

[2] S. Coda et al 2025 30th IAEA Fusion Energy Conf., conference contribution