The Small Aspect Ratio Tokamak SMART: status and plans*

SMART is a spherical tokamak currently being assembled at the University of Seville (Spain) to explore the physics of negative triangularity plasmas at low aspect ratio [1]. SMART is designed for flexible shaping with triangularities -0.6≤δ≤0.6, aspect ratio 1.4≤A≤3.0, elongation κ<3 and major/minor radii of 0.45m and 0.25cm, operating at Bt ≤1T and Ip≤1MA. After an initial phase of ohmic plasmas, SMART will be heated by hydrogen Neutral Beam Injection with PNBI=1MW and maximum injection energy of 30keV [2]. Planned diagnostics (including magnetics, Thomson scattering, spectroscopy, interferometry, probes) will be discussed. Initial plasma scenarios have been developed with the FIESTA code for magnetic equilibrium and coil settings and the ASTRA code for evaluating the plasma performance [3]. ASTRA simulations are used as a starting point for further time-dependent predictions through the TRANSP code. NBI parameters have been optimized using the ASCOT and TRANSP codes [4]. Stability studies have been performed using the MARS-F code for linear simulations and the MEGA code for hybrid non-linear simulations. For the given SMART scenarios, it has been observed that NT provides a smaller stable operational window against edge current and pressure gradient driven modes compared to positive triangularity, but comparable to that found in conventional tokamaks.

References: [1] M. Garcia-Munoz, IAEA-FEC (2023); [2] A. Mancini, FED 171 10 (2021); [3] S. J. Doyle, PRX 3 12 (2021); [4] D. J. Cruz-Zabala, EPS (2023)