Assembly and Initial Operation of 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 limited means of diagnosis in large plasma devices and additional complexity arising from the plasma dynamics. A novel ablation test stand is being developed on-campus at Columbia University to provide more direct ablation measurements. The test stand linearly propels pellets, utilizes a well-characterized electron beam as an ablation source, and measures mass loss and ablation rate via multiple diagnostics to better inform ablation models and pellet injection system development. A pipe-gun pellet injector with a cryogenic mechanical punch to release the pellets has been developed in collaboration with Oak Ridge National Laboratory. The injector has been installed on the PAC test stand and has injected initial H2 pellets. The injector and gas manifold are controlled by LabVIEW software, allowing fully-automated operation and consistent pellet parameters. Microwave resonance cavities and a high-speed python-coupled camera have been installed, serving as the primary pellet integrity and ablation diagnostics in preparation for the first ablation shot campaign.