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 andfabricated for a small size 0.8 mmcryogenic pellet with a low speed of 200-300 m/s in medium-sizedplasmafusion devices. Pellet injection withpneumatic acceleration was examined using a conventionalin 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 gatemeasurements 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 themeasured pellet parameters does not cross theplasma center, even in medium-sizedplasma devices such as the Heliotron J helicaldevice. The injection barrel with a tapered structure developed in this study is feasible for low speed pellet injection.

Source: Review of Scientific Instruments - October 17, 2016 Category: Physics Authors: G. Motojima, R. Sakamoto, H. Okada, K. Nagasaki, H. Yamada, Y. Nakamura, S. Kado, S. Kobayashi, S. Konoshima, T. Minami, S. Ohshima, S. Yamamoto, T. Mizuuchi and T. Mutoh Source Type: research