Dual SPI experiments on DIII-D

Experiments on DIII-D utilized two shattered pellet injections (SPIs) at different toroidal locations into the same plasma simultaneously or with a slight time delay between injections. Simultaneous SPIs using small pellets of equal composition (~200 torr-L of pure Ne) result in a shorter current quench (CQ) duration, more uniform radiation, a faster plasma cooling duration, and a four-fold increase in electron density compared to a single SPI from the same experiment. Comparison of the two small simultaneous SPIs to a single, larger, pure Ne SPI (~400 torr-L) mitigating like plasmas show similar CQ durations as well as electron density increases. Despite the similar characteristics, the reduction of radiation peaking for multiple pellets is a promising result critical to the success of the massively parallel ITER SPI system. A comparison of experiments and the possible implications to the ITER DMS system will be presented.