Title: Suppression of first-wall interaction in negative triangularity plasmas on TCV

Abstract

Magnetically confined fusion plasmas with negative triangularity (d) exhibit greater L-mode confinement than with positive d. Recent experiments in the TCV and DIII-D tokamaks have correlated the confinement improvement to a reduction of fluctuations within the plasma core. We report on fluctuation measurements in the scrape-off layer (SOL) for −0.61 < d < +0.64 in limited and diverted ohmic L-mode plasmas; these reveal a strong reduction in SOL fluctuation amplitudes at d < −0.25, and, surprisingly, an almost full suppression of plasma interaction with the main-chamber first-wall, which could have important implications for the prospects of using negative d plasmas as a reactor solution. An exploration of several physical mechanisms suggests that a reduced connection length—intrinsic to negative d plasmas—plays a critical role in the origin of this phenomenon.

Authors:

Han, W.; Offeddu, N.; Golfinopoulos, T.; Theiler, C.; Tsui, C. K.; Boedo, J. A.; Marmar, E. S.

Publication Date:

2022-05-11

DOE Contract Number:  

SC0014264; SC0020327; SC0010529

Research Org.:

Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center; Univ. of California, San Diego, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY

OSTI Identifier:

1887946

DOI:

https://doi.org/10.7910/DVN/JOMOQF