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A disruption mitigation system (DMS) is necessary for fusion-grade tokamakslike ITER in order to ensure the preservation of machine components throughouttheir designated operational lifespan. To address the intense heat andelectromagnetic loads that occur during a disruption, a shattered pelletinjection (SPI) system will be employed. The penetration and assimilation(ionized material that stays inside the plasma volume) of the injected materialis influenced by various SPI parameters, including the fragment sizes, speeds,and composition of the shattered fragments. An SPI system was installed on theASDEX Upgrade tokamak to study the effect of the aforementioned parameters. Inthis thesis, 1.5D simulations with the INDEX code have been utilised to conductparametric scans, thus examining the influence of fragment sizes, velocities,and pellet composition on the efficacy of disruption mitigation.  When injecting only deuterium, I found material assimilation to be limited tothe edge of the plasma with larger and faster fragments leading to higherassimilation. For mixed deuterium/neon injections, again, larger and fasterfragments enabled higher assimilation. The amount of assimilated neon increasedwith increasing injected neon amounts but saturated for larger neon fractionpellets. I also carried out comparisons with previous experimental results ofpenetration, material assimilation and pre-TQ duration. Previous experimentalresults for pure deuterium injections indicated that larger and fasterfragments exhibit greater penetration, aligning with findings from thesimulations. Simulated material assimilation trends for pure deuteriuminjections were also found to be qualitatively similar to the experiments.Nonetheless, a major difference in the quantitative assimilation values wasidentified, likely associated with the experimental assimilation criterion.

Modelling of shattered pellet injection experiments on the ASDEX Upgrade tokamak