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A Technique for Producing Large Dual-Layer Pellets in Support of Disruption Mitigation Experiments

S. K. Combs, J. W. Leachman, S. J. Meitner, L. R. Baylor, C. R. Foust, N. Commaux, T. C. Jernigan

Fusion Science and Technology / Volume 60 / Number 2 / August 2011 / Pages 473-479

Plasma Engineering - Fueling and Diagnostics / Proceedings of the Nineteenth Topical Meeting on the Technology of Fusion Energy (TOFE) (Part 2) /

A special single-shot pellet injection system that produces and accelerates large cryogenic pellets (~16mm diameter and composed of D2 or Ne) to relatively high speeds (>300 and 600 m/s, respectively) was previously developed at the Oak Ridge National Laboratory. Subsequently, a similar system was installed on DIII-D and used successfully in disruption mitigation experiments. To circumvent some operational issues with injecting the large Ne pellets, a technique has been developed in which a relatively thin layer (0.1 to 1.0 mm) of D2 is frozen on the inner wall of the pipe-gun barrel, followed by filling the core with solid Ne.A fast solenoid valve operating with a light gas (H2 or He) at relatively high pressure (~70 bar) provides the force necessary to break away the dual-layer pellet and accelerate it. The technique and the initial laboratory tests are described, as well as the implementation and operational issues for fusion experiments.

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