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The technological developments for the ITER disruption mitigation system (DMS) are crucial since it has to mitigate the lifetime consequences of high-energy plasma disruptions on in-vessel components and structures of ITER. In the framework of the ITER “Technology Fundamental Studies for DMS,” CEA/DSBT designed and operates a pellet injection test bench to study the production and the acceleration of large cryogenic pellets (up to 28.5 mm diameter) of protium, deuterium, neon, and mixtures thereof. The pellet formation process has been explored over a wide range of operational parameters, such as barrel pressure and cold head temperatures with the aim to minimize the formation time and guarantee intact pellets upon firing. Variations procedure for the initial phase and after completion of the pellet formation have significantly improved the pellet integrity after acceleration. Large protium (H) pellets are successfully produced in 20 min at 5 K and 72 mbar of barrel pressure and accelerated above 500 m/s, which is within the target values for the ITER DMS (30 min, 500 m/s). Novel formation processes and firing conditions were intensively studied to achieve such promising results. Fine-tuning of the temperatures and pressures in the cold cell at the beginning and at the end of the pellet formation are key to launch fully reproducible intact pellets. The performed experiments show that the launch characteristics (dislodging pressure and speed) also dependent on the pellet temperatures history prior to the shot. Deuterium, neon, and H/Ne mixed with and without shell pellets have been successfully produced applying the same process. The deuterium pellets are formed in a similar duration as the protium ones but have slightly lower speeds due to a different ratio mass/breakaway pressure. The neon pellets are longer to produce and difficult to dislodge. To overcome this issue, protium shell (< 1 mm) with neon core pellets is produced and fired at propellant pressures lower than 150 bar. Finally, mixed pellets with up to 10% of neon mass fraction in protium pellets are produced with a slightly longer formation duration than pure protium ones and accelerated to similar speeds. Additional studies and analysis are ongoing to better characterize the pellet formation and acceleration process in order to define the adapted design and achievable performances of the ITER-DMS shattered pellet injection (SPI) system.