2004 Fiscal Year Final Research Report Summary
Direct Measurement of Bounce Ions and Suppression of Radial Transport by Control of Radial Electric Field
| Project/Area Number |
15360488
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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 | University of Tsukuba |
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Principal Investigator |
ISHII Kameo University of Tsukuba, Graduate School of Pure and Applied Science, Associate Professor, 大学院・数理物質科学研究科, 助教授 (10015844)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Teruo University of Tsukuba, Graduate School of Pure and Applied Science, Associate Professor, 大学院・数理物質科学研究科, 助教授 (80143163)
KATANUMA Isao University of Tsukuba, Graduate School of Pure and Applied Science, Associate Professor, 大学院・数理物質科学研究科, 助教授 (70134202)
YOSHIKAWA Masayuki University of Tsukuba, Graduate School of Pure and Applied Science, Associate Professor, 大学院・数理物質科学研究科, 助教授 (00272138)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Plug Potential Bounce Ion / Potential Confinement / Tandem Mirror / Radial Electrostatic Field / Radial Transport / Charge Exchange Bounce Ion Analyzer / Gold Neutral Beam Probe / Coaxially Divided End-Plates |
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| Research Abstract |
The purpose of this research is to investigate the transport of ions bouncing between the electrostatic plug potentials or magnetic mirrors passing through the anchor cells having a non-axisymmetric magnetic field configuration. Existence of the bounced ion by the plug potential is essential for improvement of the plasma confinement in the tandem mirror. We observed the bounce ions using two kinds of measurement techniques, that is, we measured the bounce ions as the peaking end-loss ions appeared after switching off the microwave injection into the plug region by use of an end-loss energy component analyzer (ELECA), and we measured the bounce ions by use of a charge exchange bounce ion analyzer of a compact type (CXBIA) located near the inner mirror throat of the plug/barrier cell.
The transport of the bounce ions to the loss region, which was caused by the Alfven ion-cyclotron (AIC) fluctuation excited in the central solenoid and measured using a gold neutral beam probe (GNBP), was in
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vestigated from a view point of the ion diffusion across the loss boundary in the velocity space by measurement of the velocity distribution function of the end-loss ion. We observed the gentle hump structure on the energy distribution function of the end-loss ion, which was measured by the ELECA device, and estimated the enhancement factor. In order to control the radial potential profile of the core plasma, we changed the electrostatic potentials of the coaxially divided end plates, and observed experimentally the effect of the control of the potential profile. The trajectories of the bounced ions by the plug potential were calculated as a function of the width of the radial potential profile on the assumption that the shape of the magnetic flux tube was slightly different from the shape of the equi-potential surface at the mirror throats of the anchor cell. The discrepancy enhanced the radial transport for the bounce ions to flow from the bounce region to the loss region.
We confirmed experimentally and theoretically that the spread type of radial potential profile of the core plasma was effective for the increase of the density of the plasma and also the bounce ions. It is important that the microwave injection for the creation of the plug potential should be considered from this point of view. Less
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