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The SMall aspect ratio tokamak (SMART) is a new spherical device, that is, currently being constructed at the University of Seville. The operation of SMART will cover three phases reaching a maximum plasma current ( $I_{P}$ ) of 400 kA, a toroidal magnetic field ( $B_{T}$ ) of 1 T, and a pulse length of 500 ms. Such operating conditions present notable challenges to the design and verification of SMARTs structural integrity during normal and off-normal operations. In particular, vertical displacement events (VDEs) and disruptions (Boozer, 2012) are most important as they can cause severe damage to the components directly exposed to the plasma due to the significant electromagnetic (EM) and thermal loads delivered over ms timescales. As a consequence, a detailed evaluation of the EM loads during plasma disruptions is mandatory for the correct dimensioning of the machine, in particular the vacuum vessel. The EM loads are mainly produced by: the poloidal flux variation during the thermal and current quench, halo currents (Boozer, 2013) that flow into the vacuum vessel and interacts with the toroidal magnetic field; and toroidal flux variation during the thermal and current quench. We present, here, the EM and structural analysis performed for the design of SMART. The modeling has been carried out by combining equilibrium scenarios obtained through the FIESTA code (Cunningham, 2013), estimating VDE and disruption time-scales by comparing other machines (Chen et al. 2015), (Hender et al. 2007), and (Bachmann et al. 2011) and computing EM forces through a finite element model (FEM) taking into account the effects of both eddy and halo currents (Roccella et al. 2008), (Titus et al. 2011), and (Ortwein et al. 2020). Finally, the structural assessment of the vacuum vessel is performed in order to verify its integrity during normal and off-normal events in phase 3.

The SMall Aspect Ratio Tokamak (SMART) is a new spherical device that is currently being designed at the University of Seville. SMART is a compact machine with a plasma major radius (R) greater than 0.4 m, plasma minor radius (a) greater than 0.2 m, an aspect ratio (A) over than 1.7 and an elongation (k) of more than 2. It will be equipped with 4 poloidal field coils, 4 divertor field coils, 12 toroidal field coils and a central solenoid. The heating system comprises of a Neutral Beam Injector (NBI) of 600 kW and an Electron Cyclotron Resonance Heating (ECRH) of 6 kW for pre-ionization. SMART has been designed for a plasma current (I) of 500 kA, a toroidal magnetic field (B) of 1 T and a pulse length of 500 ms preserving the compactness of the machine. The free boundary equilibrium solver code FIESTA [1] coupled to the linear time independent, rigid plasma model RZIP [2] has been used to calculate the target equilibria taking into account the physics goals, the required plasma parameters, vacuum vessel structures and power supply requirements. We present here the final design of the SMART vacuum vessel together with the Finite Element Model (FEM) analysis carried out to ensure that the tokamak vessel provides high quality vacuum and plasma performance withstanding the electromagnetic j×B loads caused by the interaction between the eddy currents induced in the vessel itself and the surrounding magnetic fields. A parametric model has been set up for the topological optimization of the vessel where the thickness of the wall has been locally adapted to the expected forces. An overview of the new machine is presented here.