Overview of recent results from the ST40 compact high-field spherical tokamak

• Published in: Nuclear fusion Vol. 64; no. 11; pp. 112020 - 112033
• Main Authors: McNamara, S.A.M., Alieva, A., Anastopoulos Tzanis, M.S., Asunta, O., Bland, J., Bohlin, H., Buxton, P.F., Colgan, C., Dnestrovskii, A., du Toit, E., Fontana, M., Gemmell, M., Gryaznevich, M.P., Hakosalo, J., Hardman, M.R., Harryman, D., Hoffman, D., Iliasova, M., Janhunen, S., Janky, F., Lister, J.B., Lowe, H.F., Maartensson, E., Marsden, C., Medvedev, S.Y., Mirfayzi, S.R., Moscheni, M., Naylor, G., Nemytov, V., Njau, J., O’Gorman, T., Osin, D., Pyragius, T., Rengle, A., Romanelli, M., Romero, C., Sertoli, M., Shevchenko, V., Sinha, J., Sladkomedova, A., Sridhar, S., Stirling, J., Takase, Y., Thomas, P.R., Varje, J., Vekshina, E., Vincent, B., Willett, H.V., Wood, J., Wooldridge, E., Zakhar, D., Zhang, X., Battaglia, D., Bertelli, N., Bonofiglo, P.J., Delgado-Aparicio, L.F., Duarte, V.N., Gorelenkov, N.N., de Haas, M., Kaye, S.M., Maingi, R., Mueller, D., Ono, M., Podesta, M., Ren, Y., Trieu, S., Delabie, E., Gray, T.K., Lomanowski, B., Unterberg, E.A., Marchuk, O.
• Format: Journal Article
• Language: English
• Published: IAEA IOP Publishing 01.11.2024
• Subjects: high-field; overview; spherical tokamak; ST40
• ISSN: 0029-5515; 1741-4326
• DOI: 10.1088/1741-4326/ad6ba7

Abstract ST40 is a compact, high-field ( B T 0 ⩽ 2.1 T ) spherical tokamak (ST) with a mission to expand the physics and technology basis for the ST route to commercial fusion. The ST40 research programme covers confinement and stability; solenoid-free start-up; high-performance operating scenarios; and plasma exhaust. In 2022, ST40 obtained central deuterium ion temperatures of 9.6 ± 0.4 keV , demonstrating for the first time that pilot plant relevant ion temperatures can be reached in a compact, high-field ST. Analysis of these high-ion temperature plasmas is presented, including a summary of confinement, transport and microstability characteristics, and energetic particle instabilities. Recent scenario development activities have focused on establishing diverted H-mode plasmas across a range of toroidal fields and plasma currents, along with scenarios with high non-inductive current fractions. In future operations, beginning in 2025, a 1 MW dual frequency (104/137 GHz) electron cyclotron (EC) system will be installed to enable the study of EC and electron Bernstein wave plasma start-up and current drive. Predictive modelling of the potential performance of these systems is presented.