## 2 Overview of the Issue
The physics understanding behind the triggering of ELMs with pellets is still progressing, but simulations with JOREK [32] support the idea that high pressure and density plasmoids, generated by the injection of the frozen pellets at the edge of the plasma, lead to a helical perturbation centered on the field line of the injected pellet causing then an ELM. Considering what stated above, it emerges how a proper estimate of the triggering efficiency and pacing characterization is fundamental. The article written by [PERSON] et al. [33] focuses on such topics. It is devoted at estimating the efficiency of ELMs pacing by using a Spectrogram Cross-Correlation based algorithm combined to a k-means approach for classification. The developed methodology allows assessing which ELM is triggered by a pellet as well as which pellet actually triggered an ELM; the triggering efficiency in terms of percentage of triggered ELMs and in terms of triggering pellets as well as the triggering time delay and its distribution. The work has also shown how a relatively new type of diagnostic [34], based on a synthetic diamond sensor can be used to infer dynamical quantities related to ELMs. The resolution of such diagnostic allows in fact to derive a sharper triggered time distribution w.r.t the Be line signal that is used on a routine basis. Estimates using the diamond diagnostic are furthermore more in line with JOREK simulations of the expected triggering time [35]. The previous paragraphs have highlighted the importance of data analysis for both modelling and for diagnostic assessments and improvements, aimed at guaranteeing the operational safety, stability and feasibility of the next generation of devices. Another key feature that has emerged and that is strictly connected with the previous one, is represented by the manufacturing and by the study of the thermomechanical properties, the interaction with the plasma with the neutron fluxes of both the plasma facing materials (PFM) and of the plasma facing components (PFC). Thermally induced erosion of the (PFM) and the damage of the joints between the PFM and the heat sinks, are indeed to be considered for the integrity and operational safety of a device. Extensive research campaigns aimed at studying the PFM interaction with the plasma have been held by different facilities [36; 37; 38] and by many laboratory experiments [39; 40; 41; 42; 43; 44; 45; 46; 47; 48]. In such context, it is worth to recall the occurrence of the melting failure event during the plasma campaign in 2019 on the EAST tokamak [49; 50; 51; 52]. [PERSON] et al. [53] have studied, by metallography and SEM+EBSD technique, the microstructure of the upper divertor components of EAST, consisted of the CuCrZr cooling components, protected by tungsten armor, that have been damaged because of the just mentioned melting failure event occurred during the 2019 campaign. The recrystallization of the rolled tungsten components has been observed and the range of the recrystallization had been determined via heat flux distribution. Intergranular cracks in the recrystallized and in the rolled zones of tungsten monoblocs as well as interface deboning in Cu/CuCrZr interface of the cooling components were found. Tungsten is actually the main candidate of the PFMs to be used in the locations of the device with the highest thermal and plasma particles loads, such as the divertor, to protect the cooling system components [54; 55; 56; 57; 58; 59]. The joining of W with the heat sink materials is a challenging task due to the W refractory property. The plasma spraying (PS) of W on the heat sink materials with an appropriate interlayer is an established and recommended technique that shows good adhesion and thermomechanical proprieties [60; 61; 62; 63]. The optimal plasma spraying process parameters, interlayer and substrate characteristics are the object of many research campaigns [64; 65; 66; 67; 68]. [PERSON] et al.