Experimental observations of 3D neon transport following shattered pellet injection in Super H-modes*

Stable DIII-D Super H-modes with 1.8~MJ thermal energies are terminated by a shattered neon pellet to study radiation asymmetries during mitigated disruptions. Asymmetric neon distributions cause radiation peaking that might melt ITER components [Lehnen NF \textbf{55} (2015) 123027]. Ne-I images of the injection show field-aligned and cross-field structures, and penetration to the $q=2$ surface before the thermal quench (TQ). Near the injection in the co-rotation direction, an Absolute eXtreme UltraViolet fan array (AXUV-1) also exhibits signs of cross-field transport. Approximately twice the distance in the counter-rotation direction, AXUV-2 and interferometry measurements corroborate a 0.5-1~ms delay in the arrival of neon ions relative to AXUV-1, indicating a peaked Ne distribution during this time. When the Ne reaches AXUV-2, the Ne distribution is helical, and this helical structure is evident throughout the TQ. Interferometry further supports this helical structure and reveals strong inboard-to-outboard density asymmetries. Parallel diffusion does not appear suitable to explain these observations, so parallel convection models are under investigation, and implications for radiation peaking in ITER will be discussed.