SPI nonthermal seed formation as a function of neon fraction

2025 Research Campaign, Disruption Mitigation

Purpose of Experiment

The purpose of this experiment is to provide data to help understand at what neon fraction there is a danger of runaway electron (RE) formation in ITER when it uses shattered pellet injection (SPI) for disruption mitigation. ITER wishes to add some neon into its nominally D2 dominated SPI to prevent divertor melting from large disruption conducted heat loads; however, adding neon can increase the probability of forming REs also.

Experimental Approach

Super-H target plasmas will be used in DIII-D as these have high electron temperature and a high propensity for nonthermal electron seed formation during disruptions. The plasmas will be shut down with D2-dominant SPI from 15 degrees toroidal angle. The shutdown will be repeated with varying neon fractions, covering the range Ne/D2 ~ 1% – 20%. Diagnostics will be optimized for detection of nonthermal electron seeds during the disruption, including soft x-ray (SXR), mid x-ray (MXR), hard x-ray (HXR), visible imaging, Thomson scattering (TS), and IR imaging.

See more details, including project leads, at U.S. Department of Energy, Office of Scientific and Technical Information (OSTI).