2024/07/31 by A. O. Nelson, C. Vincent, Nelson, A. O. +27
Engineering · Materials Science · Physics and Astronomy · #Electron and X-Ray Spectroscopy Techniques #FOS: Physical sciences #Plasma Physics (physics.plasm-ph) #Surface Roughness and Optical Measurements #Surface and Thin Film Phenomena
paper · pdf · doi:10.48550/arxiv.2408.00180
openalex publication_date 2024/07/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
A plasma scenario with negative triangularity (NT) shaping is achieved on MAST-U for the first time. While edge localized modes (ELMs) are eventually suppressed as the triangularity is decreased below δ < -0.06, an extended period of H-mode operation with Type-III ELMs is sustained at less negative δ even through access to the second stability region for ideal ballooning modes is closed. This documents a qualitative difference from the ELM-free access conditions documented in NT scenarios on conventional aspect ratio machines. The electron temperature at the pedestal top drops across the transition to ELM-free operation, but a steady rise in core temperature as δ is decreased allows for similar normalized beta in the ELM-free NT and H-mode positive triangularity shapes.