First Access to ELM-free Negative Triangularity at Low Aspect Ratio
Abstract
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 < -0.06, an extended period of H-mode operation with Type-III ELMs is sustained at less negative 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 is decreased allows for similar normalized beta in the ELM-free NT and H-mode positive triangularity shapes.
Keywords
Cite
@article{arxiv.2408.00180,
title = {First Access to ELM-free Negative Triangularity at Low Aspect Ratio},
author = {A. O. Nelson and C. Vincent and H. Anand and J. Lovell and J. F. Parisi and H. S. Wilson and K. Imada and W. P. Wehner and M. Kochan and S. Blackmore and G. McArdle and S. Guizzo and L. Rondini and S. Freiberger and C. Paz-Soldan},
journal= {arXiv preprint arXiv:2408.00180},
year = {2024}
}