Automated Formation and Initial Ablation Results of Hydrogen and Neon Pellets in a Pellet Ablation Test Stand

Cryogenic pellets used for disruption mitigation, core fueling, and edge-localized mode pacing are all assimilated into the bulk plasma via ablation. Data used to characterize ablation rate and mechanisms is sourced primarily in situ from tokamak experiments. This data suffers from poor precision due to the limited diagnostic capabilities in large plasma devices and the additional complexity arising from plasma dynamics. Pellets at Columbia (PAC) has been developed at Columbia University to provide more direct measurements of ablation.

A LabVIEW program has been developed to automate pellet formation, maximising consistency between shots. This program relies on feedback control of cryogenic temperature zones and barrel pressure, as well as differential pumping, to create uniform and consistent pellets of H2, Ne, and mixed species. A high-energy electron beam will be incorporated with the vacuum systems, providing a well-characterised ablating electron flux on the pellet. Pellet injection and beam pulsing have been aligned using an optical light gate to demonstrate ablation of H2 and Ne pellets.