TCV TeamEUROfusion Tokamak ExploitFevrier, O.Tsui, C. K.Durr-Legoupil-Nicoud, G.Theiler, C.Carpita, MassimoCoda, SColandrea, ClaudiaDuval, B. P.Gorno, Sophie Danielle AngelicaHuett, Emanuel PaulLinehan, B.Perek, ArturPorte, LReimerdes, H.Sauter, OTonello, E.Zurita, M.Bolzonella, T.Sciortino, F.2024-05-012024-05-012024-05-012024-06-0110.1088/1361-6587/ad3c1chttps://infoscience.epfl.ch/handle/20.500.14299/207737WOS:001206067300001In recent years, negative triangularity (NT) has emerged as a potential high-confinement L-mode reactor solution. In this work, detachment is investigated using core density ramps in lower single null Ohmic L-mode plasmas across a wide range of upper, lower, and average triangularity (the mean of upper and lower triangularity: delta) in the TCV tokamak. It is universally found that detachment is more difficult to access for NT shaping. The outer divertor leg of discharges with delta approximate to - 0.3 could not be cooled to below 5 eV through core density ramps alone. The behavior of the upstream plasma and geometrical divertor effects (e.g. a reduced connection length with negative lower triangularity) do not fully explain the challenges in detaching NT plasmas. Langmuir probe measurements of the target heat flux widths (lambda q ) were constant to within 30% across an upper triangularity scan, while the spreading factor S was lower by up to 50% for NT, indicating a generally lower integral scrape-off layer width, lambda int. The line-averaged core density was typically higher for NT discharges for a given fuelling rate, possibly linked to higher particle confinement in NT. Conversely, the divertor neutral pressure and integrated particle fluxes to the targets were typically lower for the same line-averaged density, indicating that NT configurations may be closer to the sheath-limited regime than their PT counterparts, which may explain why NT is more challenging to detach.Physical SciencesNegative TriangularityDetachmentDivertorPower ExhaustTcvtext::journal::journal article::research article