We develop a two-dimensional (2D) Gaussian deposition model to calculate the initial pellet deposition density immediately after pellet ablation, which is valid before the ∇B-drift of the ablated material significantly shifts its location. A 2D Gaussian particle distribution is assumed in the ablation cloud cross-section. Applying this new model to a typical EAST plasma, and comparing it with the conventional point deposition model, it is found that the new model can resolve the tangential singularity problem encountered by the point deposition model. In addition, the model predicts that the initial pellet deposition density depends strongly on the ablation cloud radius as well as the form of the radial particle distribution in the ablation cloud with tangential injection. The ∇B-drift is then introduced with the drift displacement estimated based on a scaling formula derived from HPI2 simulations. The model can provide a fast evaluation of pellet deposition density compared to the predictive HPI2 code at the expense of acceptable accuracy loss. This model could be a useful tool for physical studies relevant to pellet injection, such as pellet ELM triggering and particle and energy transport.

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Laser cladding is an advanced material processing technology that has potential to improve the performances of metals. To improve the hardness and wear resistance of the surface of Magnesium alloy, SiC-316L composite coating on AZ31 magnesium alloy by laser cladding was generated, and the composition and properties analysis of the cladding coating were conducted. The results show that the laser cladding coating and the substrate achieve a good metallurgical bonding. The growth morphology of boundary is mainly branch dendrite.When the laser power is 1250 W, spot diameter is 2mm, scanning speed is 25 mm/s and average energy density is 2.5×104J, the cladding layer possesses the best micro-hardness, about 3 times as hard as the substrate.