Speaker
Description
Experiments at TCV [1–3], DIII-D [4–6] and AUG [7,8] indicate that Negative Triangularity (NT) plasmas [9] can achieve H-mode-like performance with negligible ELM activity. Therefore, NT is investigated as a possible scenario for fusion reactors [10, 11]. However, the physics of NT is still to be fully understood. An experimental and theoretical effort is ongoing to fill this gap.
A NT scenario is being designed for the Divertor Tokamak Test (DTT) facility [13], under construction in Italy, which aims to test alternative designs and materials for the EU DEMO divertor. Its transport properties are being studied by performing integrated modelling (ASTRA [14]/TGLF [15]), gyrokinetic simulations (GENE [16]) and experiments with DTT-like shapes on actual tokamaks. The first results of DTT predictions [17], as well as of experiments performed at TCV [3] and AUG [8], indicated that with the first proposed DTT NT shape with relatively small average triangularity, a beneficial effect of NT was found in the edge/scrape-off layer [18]. The NT confinement levels were found intermediate between positive delta H-mode and L-mode and NT core pressure values which are similar to the ones predicted for the Positive Triangularity (PT) H-mode scenario, in absence of ELMs, making the NT option an attractive alternative.
Then, a new DTT shape with larger upper NT and reduced volume was proposed, to further optimize the scenario. A newly developed ASTRA/TGLF interface that provides a realistic plasma shape was also adopted, since the standard ASTRA/TGLF Miller geometry was found a too strong approximation for the DTT ‘teardrop’-like NT shapes. In this way, the formation of a proto-pedestal in the edge pressure was observed in the simulations, further improving the NT performance almost reaching the PT H-mode. These ASTRA simulations provided input for more complex GENE-TANGO simulations, which are ongoing.
References
[1] Y. Camenen, et al., 2005 Plasma Phys. Control. Fusion 47, 1971.
[2] S. Coda, et al., 2022 Plasma Phys. Control. Fusion 64, 014004.
[3] A. Balestri, et al., 2024 Plasma Phys. Control. Fusion 66, 065031.
[4] M.E. Austin, et al., 2019 Phys. Rev. Lett. 122, 115001.
[5] A. Marinoni, et al., 2019 Phys. Plasmas 26, 042515.
[6] A. Marinoni, et al., 2021 Nucl. Fusion 61, 116010.
[7] T. Happel, et al., 2023 Nucl. Fusion 63, 016002.
[8] L. Aucone, et al., 2024 Plasma Phys. Control. Fusion 66, 075013.
[9] A. Marinoni, et al., 2021 Rev. Mod Plasma Phys. 5, 6.
[10] S.Yu. Medvedev, et al., 2015 Nucl. Fusion 55, 063013.
[11] M. Kikuchi, et al., 2019 Nucl. Fus. 59(5), 056017.
[12] J. Ball on behalf of the TSVV 2 team, AAPPS-DPP 2023.
[13] R. Ambrosino, et al., 2021 Fusion Eng. Des. 167, 112330.
[14] G.V. Pereverzev and P.N. Yushmanov 2002 IPP Report 5/98.
[15] G.M. Staebler, et al., 2016 Phys. Plasmas 23 062518.
[16] F. Jenko, et al., 2000 Phys. Plasmas 7 1904.
[17] A. Mariani, et al., 2024 Nucl. Fusion 64, 046018.
[18] A. Mariani, et al., 2024 Nucl. Fusion 64, 106024.
