| Co-Investigator(Kenkyū-buntansha) |
KOGOSHI Sumio Science University of Tokyo, Faculty of Science and Technology, Associate Profes, 理工学部, 助教授 (60134459)
SAKAMOTO Mizuki National Institute for Fusion Science, Research Associate, 助手 (30235189)
ANDO Akira National Institute for Fusion Science, Research Associate, 助手 (90182998)
KANEKO Osamu National Institute for Fusion Science, Associate Professor, 助教授 (00126848)
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| Research Abstract |
In order to study basic properties of toroidal plasmas by pellet injection, it is extremely desirable for the pellet injector to be reproducible and to be controllable. Until now, several injectors were developed in some places, where one could vary pellet size to a certain extent. However, they could vary it only in a discrete manner. In our present study, a new injector has been designed and constructed in order to develop a technique with continuous size-controllability.
The injector has been developed so as to vary a pellet size by using a special technique of a pellet-length limiting rod. The first results were not satisfactory ; that is, the obtained pellet sizes were not consistent with the presetting values. The reason was ocnsidered to be partially because that an attachment force of solid hydrogen and metal surface of the length-limiting rod might have disturbed the expected operation, and partially because that the pressure of hydrogen gas for producing ice pellet might also
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have disturbed the expected operation.
Various materials has been tested as a head of length-limiting rod and as a coating stuff on it. Experiments for comparison ofthe results with and without the hydrogen gas in the ice pellet production part have also been carried out. In addition to these studies, the effect of various shape of the pellet production cavity has been examined, which might have some influence in rsisting the attachment force of a pellet and the rod. Those results showed each effect to some extent, but each of it was not a perfect one.
Finally the improvement of the operaiton procedure in controlling a pellet size has been considered and tested. The idea is to change the pellet production position in order to eliminate the possibility of attachment of solid hydrogen and the surface of the length-limiting rod. The final results show very good agreemtne between the observed size and the presetting value. The pellet size has been measured by using a high-speed framing photograph just after the ejection from the muzzle. Thus, the technique will become a useful method for this field.
By using this newly developed injector, various injection experiments have been carried out, and several interesting phenomena have been observed. Less
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