2006 Fiscal Year Final Research Report Summary
Development of Neutral Lithium Beam by Microwave Heating Method and its Application to Divertor Plasma Research
| Project/Area Number |
16360461
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | National Institute for Fusion Science |
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Principal Investigator |
IGUCHI Harukazu National Institute for Fusion Science, Dep. Large helical Device Project, Associate Professor, 大型ヘリカル研究部, 助教授 (40115522)
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| Co-Investigator(Kenkyū-buntansha) |
MORISAKI Tomohiro National Institute for Fusion Science, Dep. Large helical Device Project, Associate Professor, 大型ヘリカル研究部, 助教授 (60280591)
GOTO Motoshi National Institute for Fusion Science, Dep. Large helical Device Project, Research Associate, 大型ヘリカル研究部, 助手 (00290916)
OKAMURA Shoichi National Institute for Fusion Science, Dep. Large helical Device Project, Professor, 大型ヘリカル研究部, 教授 (60115540)
SATO Motoyasu National Institute for Fusion Science, Coordination Research Center, Professor, 連携研究推進センター, 教授 (60115855)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Lithium Beam / Microwave Sintering / Divertor Plasma / Beam Probe / Ion Source / Beta-eucryptite / Plasma Diagnostics / Beam Probe Spectroscopy |
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| Research Abstract |
The research project aims to develop an intense lithium neutral beam (of 10 mA level) for diagnostic of the edge and diverter region of magnetically confined plasmas, where a unique method of microwave heating for the thermionic ion source is planned. The development is scheduled in two steps. In the first step, a method to heat up lithium P-eucryptite into liquid state and fill them into a porous tungsten disk in the microwave oven is developed. In the second step, an intense ion beam is extracted from an ion gun of a thermionic ion source heated by microwave.
So far, the lithium P-eucryptite has been successful absorbed in the porous tungsten disk of 30 mm diameter (70 % dense) in a vacuum microwave oven (2.45 GHz, 1.3 kW/CW), where microwave absorber is a silicon carbide (SiC) covered by ceramic fibers forming a thermal insulating block. The oven temperature reached above 1,400 degree C (much higher than the melting point of the β-eucryptite of 1,306 degree C) at 0.5 kW input power.
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When the tungsten of 50 mm diameter is tested with a similar configuration as the anode of the ion gun, heat loss through radiation becomes significant. Then the surface temperature of the tungsten disk was lower than the oven temperature. However, it reached to 1,200 degree C at 0.8 kW input power. This temperature is the nominal operation temperature of the lithium thermionic ion source. Feasibility of the ion gun with microwave heated thermionic ion source is confirmed.
As for the application to edge plasmas, two-dimensional imaging of the edge plasma structure has been successfully observed. A lithium neutral beam of the conventional type (6 mm diameter) with variable beam injection angle has been installed on the CHS. A two-dimensional map of the beam emission is converted to a 2-D electron density distribution. Up-down asymmetry of the plasma distribution in the edge chaotic layer of the CHS has been observed. The asymmetry of the plasma structure in the region should affect heat deposition asymmetry on the diverter plates. The result gives a significant impact on the future diverter design of helical devices. Less
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