Abstract in atti di convegno, 2023, ENG

Negative triangularity tokamak operation in TCV

Sauter O.; Bagnato F.; Balestri A.; Ball J.; Brunner S.; Coda S.; Di Giannatale G.; Duval B.; Fevrier O.; Merle A.; Murugappan M.; Pau A.; Porte L.; Sheikh U.; Vallar M.; Villard L.; Vu T.; Boedo J.A.; Tsui C.K.; Bolzonella T.; Pigatto L.; Mantica P.; Mariani A.; Marinoni A.; Medvedev S.Yu.; Piron C.; Dunne M.G.; Faitsch M.; Viezzer E.

Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), Lausanne, Switzerland; University of California-San Diego (UCSD), Center for Energy Research (CER), La Jolla, CA, USA; Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA), Padova, Italy; CNR ISTP - Istituto per la Scienza e la Tecnologia dei Plasmi, Milano, Italy; Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA, USA; Tokamak Energy Ltd, Culham Science Centre, Abingdon, UK; ENEA, Fusion and Nuclear Safety Department, C. R. Frascati, Roma, Italy; Max Planck Institute for Plasma Physics, Garching, Germany; Universidad de Sevilla, Spain.

TCV experiments and novel theoretical studies have addressed key questions regarding the operational space of negative triangularity (NT) plasmas in view of an L-mode NT reactor, in terms of stability, performance properties and core-edge integration. We show that reducing the top triangularity (?top) to more negative values induces an H-L back transition, confirming the direct dependence between H-mode existence and access to 2nd ballooning stability region. We also show that the X-point ? can prohibit H-mode access if sufficiently negative. Using these conditions to stay in L-mode, we show the sustainment of a stationary high ?N NT plasma, with H98y2 > 1, using real-time ? control with NBI as an actuator. This plasma has Ti > Te over the whole profile. Gyrokinetic simulations show that the benefit of NT might be lost for aspect ratio <2.5, in the TEM-dominated microturbulence regime and that the improved confinement is primarily due to the non X-point triangularity (top ? in single-null down divertor, SND). Global gyrokinetic studies also show that this improvement does not change with machine size (independent of ?*). These studies as well as other results presented at this conference allow us to propose in the conclusion a procedure for predicting and optimizing NT reactor plasmas which can be tested in present NT experiments.

29th IAEA Fusion Energy Conference (FEC 2023), London, United Kingdom, 16-21 October 2023

Keywords

Negative triangularity tokamak, TCV

CNR authors

Mariani Alberto, Mantica Paola

CNR institutes

ISTP – Istituto per la Scienza e Tecnologia dei Plasmi