Multi-device analysis of thermal quench duration induced by mixed neon/deuterium shattered pellet injection.*

Unmitigated disruptions pose the largest risk to the success of ITER. To prevent damage to the plasma-facing components, rapid plasma shutdown in ITER will be primarily achieved using shattered pellet injection (SPI). A robust disruption mitigation system (DMS) requires accurate characterization of key disruption parameters, such as the thermal quench (TQ). Modelling suggests that ITER plasmas will feature slower TQs compared to current devices and that the SPI pellet plume may lead the cold front inducing the TQ. If validated, these predictions would have an impact on the desired pellet characteristics for the ITER DMS. To resolve these questions, a database of SPI experiments from several small-to-large sized devices (J-TEXT, AUG, DIII-D, KSTAR, and JET) has been compiled under the auspices of the International Tokamak Physics Activity (ITPA) MHD, Disruptions, and Control topical group. Analysis of the TQ duration scaling during mixed neon/deuterium SPI is presented. Several definitions of TQ duration (i.e., I_p rise, P_rad rise, SXR signal drop) are considered to provide a consistent comparison of data across devices due to each machine’s unique diagnostic suite and disruption evolution. TQ durations will be compared across plasma/pellet parameters such as plasma current, minor radius, and neon percentage in the pellet. The location of the SPI pellet plume leading edge at the time of TQ onset is also analyzed across devices and SPI content.