2002 Fiscal Year Final Research Report Summary
Studies on the mechanism of negative ion production in the magnetic multipole ion source
| Project/Area Number |
13680568
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Nuclear fusion studies
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| Research Institution | OSAKA UNIVERSITY |
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Principal Investigator |
MIYAMOTO Seiji GRAD. SCH. OF ENG., RESEARCH ASSOCIATE, 大学院・工学研究科, 助手 (50294046)
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| Co-Investigator(Kenkyū-buntansha) |
IIDA Toshiyuki GRAD. SCH. OF ENG, PROFESSOR, 大学院・工学研究科, 教授 (60115988)
INOUE Shoji GRAD. SCH. OF ENG., RESEARCH ASSOCIATE, 大学院・工学研究科, 助手 (10203233)
HORIIKE Hiroshi GRAD. SCH. OF ENG., PROFESSOR, 大学院・工学研究科, 教授 (20252611)
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| Project Period (FY) |
2001 – 2002
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| Keywords | magnetic multipole ion source / negative ion / NBI / electron enerrv distribution function / magnetic filter / arc discharge / tantalum filament / argon gas mixin |
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| Research Abstract |
As the required energy for neutral beam being high due to the enlargement of thermonuclear fusion experimental devices, there have arisen the needs of negative-ion-based neutral beam injector (NEI). The object of this research is to find optimum conditions for negative ion production by controlling spatial distribution of electron temperature.
It was indispensable to prevent discharge electron from penetrating into extraction region for negative ion production. Magnetic filters were usually introduced for this purpose, but there was a fault that the filters reduced
plasma density inevitably. In this experiment, it was aimed at to trap discharge electron in the wall magnetic field without any magnetic filters introduced, adjusting the position of the filaments in a source. As the result, it was
attained to decrease electron temperature without reducing density in the extraction region.
High-energy discharged electron was eliminated by magnetic filter, but there still remained the possibility that electron temperature was not optimized for negative ion production. We therefore introduce a new type of magnetic Biter which consisted of a watercooled coil. It was found that negative ion production was sensibly affected by electron temperature in the absence of discharge electron.
Material of filaments was also considered to affect the negative ion production. Tantalum filament was tested and the negative ion current was increased in few ten percent in low gas pressures. As well as changing filament material, mixing argon into hydrogen gas was tested and the effect was investigated.
Accomplishing these experiments, we developed a method to measure electron energy distribution function by a Langmuir probe and observed a high energy tail in the distribution function. The method is useful to measure and analyze discharge electron motion, which had to be inferred from computer simulation till now.
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