## 2 Overview of the Issue
Disruptions are probably the most dangerous events preventing a safe and the steady state operation of a tokamak. However other designs of magnetically controlled fusion experiments exist, which might represent alternatives to the tokamak path. The most advanced competitor is the stellarator one, characterized by having field coils properly blended toroidally, shaping directly the magnetic field which confines the plasma. Such design allows avoiding the need of a toroidal current to induce a poloidal component as for tokamaks. Stellarators have a series of advantages, among which the most impressive one is indeed the almost absence of disruptions, due to the combination of the lack the toroidal current and the stabilizing effect of the magnetic shear on MHD instabilities, such as 2/1 and 3/1 modes [23]. However, stellarators have both a challenging engineering design, as well as physics issues. Considering the latter, the most important one is due to the fact that at high electron temperature, i.e., low collisionality, the neoclassical transport losses are much higher than the tokamak ones [23]. This is due to the fact that particles can be trapped in banana orbits in tokamaks, because of the axisymmetric magnetic field, while in stellarators particles are trapped in the so-called magnetic ripples, formed by the shape of the coils. Since the poloidal variation of their trajectories is small, such particles can be lost quite easily. However, W7-X has recently shown that it is possible to reduce such losses by working in a optimized neoclassical regime, reaching high temperature plasma conditions in the experimental campaigns conducted in 2017-2018 [24]. The recent developments in the stellarator community, stress the relevance of dedicated studies, such as the [PERSON] et al. [25] article, devoted at deriving alternative scaling laws for extrapolating the confinement time of the new generation of devices. The purely data-driven approach described, makes use of the Symbolic Regression technique which allows scanning a wider range of mathematical functions to describe the relationship between a dependent quantity (the confinement time in this case) and not dependent ones (the engineering and physical quantities considered as relevant). Specifically, the authors have shown how the use of a renormalization factor that has been historically used for the extrapolation of the confinement time, is not strictly mandatory. Alternative scaling laws are competitive with the widely accepted one by the community, called ISS04 [26], both for the shear and for the shear-less devices. Both tokamaks and stellarators are also affected by the so called Edge Localized Modes (ELMs) [27]. ELMs are periodic, radial events typical of the High confinement mode (H-mode), and are strictly connected to the pressure profile at the edge. Either peeling modes, or edge ballooning modes or coupled peeling-ballooning ones are the most rated ideal candidate MHD instabilities to originate ELMs [6]. ELMs cause large transient heats and particle loads on the PFCs. Extrapolating the energies associated to each ELMs to ITER [6], values up to twenty times higher than the benchmarked limits of considered materialsare expected. Energy densities up to 11 MJ m\({}^{-2}\) are indeed supposed to impact on the first wall. Therefore, methodologies to either suppress, such as Resonant Magnetic Perturbations, or mitigate, such as ELMs pacing have been tested by scientists in the last decades. Among the latter, ELMs pacing techniques have been extensively tested also on AUG [28], JET [29], DIII-D [30] and EAST [31] is thought to be one of the main tools for ELMs mitigation on ITER. Pacing would in fact reduce the heat and particle heats on PFCs wetted areas, lowering the loads to manageable levels, by triggering ELMs at the pellets pacing rate.