Injection barrel with a tapered structure for a low speed and small size cryogenic hydrogen pellet in medium-sized plasma fusion devices.
An injection barrel was designed and fabricated for a small size 0.8 mm cryogenic pellet with a low speed of 200-300 m/s in medium-sized plasma fusion devices. Pellet injection with pneumatic acceleration was examined using a conventional in situ technique. A tapered structure was applied in the downstream side of the injection barrel to satisfy the requirement of pellet speed reduction by expansion of the propellant gas. Shadowgraph and light gate measurements show that the intact pellets have speeds of 260 ± 30 m/s and a typical size of 1.1-1.2 mm. The pellet ablation code based on a neutral gas shielding model shows that the penetration depth of the measured pellet parameters does not cross the plasma center, even in medium-sized plasma devices such as the Heliotron J helical device. The injection barrel with a tapered structure developed in this study is feasible for low speed pellet injection.
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho Toki, Gifu 509-5292, Japan.
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Motojima
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho Toki, Gifu 509-5292, Japan.
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Sakamoto
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Okada
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Nagasaki
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho Toki, Gifu 509-5292, Japan.
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Yamada
Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Nakamura
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Kado
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Kobayashi
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Konoshima
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Minami
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Ohshima
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Yamamoto
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
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Mizuuchi
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho Toki, Gifu 509-5292, Japan.
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Mutoh