Non-dimensional confinement scaling in similar negative triangularity plasmas on the DIII-D and TCV tokamaks

TL;DR

This study compares energy confinement scaling in negative triangularity plasmas on DIII-D and TCV tokamaks using non-dimensional variables, revealing weak collisionality dependence and size scaling between Bohm and gyro-Bohm regimes.

Contribution

It demonstrates the applicability of non-dimensional confinement scaling in negative triangularity plasmas across different tokamaks, linking experimental and engineering scalings.

Findings

Normalized energy confinement weakly improves with collisionality

Size scaling lies between Bohm and gyro-Bohm regimes

Engineering scaling aligns with non-dimensional experiment results

Abstract

Similarity experiments were performed on the DIII-D and TCV tokamaks to explore the scaling of energy confinement in negative triangularity plasmas using non-dimensional variables. Near up-down symmetric plasmas with large top-bottom averaged negative triangularity were created in a lower single null configuration, with the shape of the separatrix being closely matched between the two devices. The normalized energy confinement is found to weakly improve at increasing collisionality and, between the two devices, shows a machine size scaling behavior between Bohm and gyro-Bohm. Engineering scaling on a large DIII-D dataset is in agreement with the non-dimensional experiment.